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diff --git a/.gitattributes b/.gitattributes new file mode 100644 index 0000000..d7b82bc --- /dev/null +++ b/.gitattributes @@ -0,0 +1,4 @@ +*.txt text eol=lf +*.htm text eol=lf +*.html text eol=lf +*.md text eol=lf diff --git a/LICENSE.txt b/LICENSE.txt new file mode 100644 index 0000000..6312041 --- /dev/null +++ b/LICENSE.txt @@ -0,0 +1,11 @@ +This eBook, including all associated images, markup, improvements, +metadata, and any other content or labor, has been confirmed to be +in the PUBLIC DOMAIN IN THE UNITED STATES. + +Procedures for determining public domain status are described in +the "Copyright How-To" at https://www.gutenberg.org. + +No investigation has been made concerning possible copyrights in +jurisdictions other than the United States. Anyone seeking to utilize +this eBook outside of the United States should confirm copyright +status under the laws that apply to them. diff --git a/README.md b/README.md new file mode 100644 index 0000000..8184f42 --- /dev/null +++ b/README.md @@ -0,0 +1,2 @@ +Project Gutenberg (https://www.gutenberg.org) public repository for +eBook #67331 (https://www.gutenberg.org/ebooks/67331) diff --git a/old/67331-0.txt b/old/67331-0.txt deleted file mode 100644 index 16ac8af..0000000 --- a/old/67331-0.txt +++ /dev/null @@ -1,12555 +0,0 @@ -The Project Gutenberg eBook of Illustrations of the Huttonian Theory -of the Earth, by John Playfair - -This eBook is for the use of anyone anywhere in the United States and -most other parts of the world at no cost and with almost no restrictions -whatsoever. You may copy it, give it away or re-use it under the terms -of the Project Gutenberg License included with this eBook or online at -www.gutenberg.org. If you are not located in the United States, you -will have to check the laws of the country where you are located before -using this eBook. - -Title: Illustrations of the Huttonian Theory of the Earth - -Author: John Playfair - -Release Date: February 6, 2022 [eBook #67331] - -Language: English - -Produced by: Tom Cosmas produced from materials made available at The - Internet Archive and placed in the Public Domain. - -*** START OF THE PROJECT GUTENBERG EBOOK ILLUSTRATIONS OF THE -HUTTONIAN THEORY OF THE EARTH *** - - - - - - -Transcriber Note - -Since § 134 appeared on page 143 and again on page 147, the Section -number on pages 147 and all succeeding were incremented. The Table of -Contents was also incremented respectively. Text emphasis denoted by -_Italics_. List of ERRATA below has been applied to the text. - - -ERRATA. - - Page 44. line 4. from the bottom, _for_ that _read_ as - " 189. " 6. " _for_ appearenes _read_ appearances - " 464. " 4. " _for_ D'AUBENTON _read_ DAUBENTON - " 482. " 12. " _for_ adversaries _read_ adversary - - - - - ILLUSTRATIONS - OF THE - HUTTONIAN THEORY - OF THE EARTH - - - BY JOHN PLAYFAIR - - F. R. S. EDIN. AND PROFESSOR OF MATHEMATICS - IN THE UNIVERSITY OF EDINBURGH. - - - ========================================================= - - Nunc naturalem causam quærimus et assiduam, - non raram et foriuitam. - - SENECA. - - ========================================================= - - - EDINBURGH: - - PRINTED FOR CADELL AND DAVIES, LONDON, AND - WILLIAM CREECH, EDINBURGH. - - ====== - - 1802. - - - Entered in Stationers Hall. - - NEILL & CO. } - Printers, Edinburgh } - - - -ADVERTISEMENT. - - -THE Treatise here offered to the Public, was drawn up with a view of -explaining Dr Hutton's Theory of the Earth in a manner more popular and -perspicuous than is done in his own writings. The obscurity of these -has been often complained of; and thence, no doubt, it has arisen, -that so little attention has been paid to the ingenious and original -speculations which they contain. - -THE simplest way of accomplishing the object proposed, seemed to be, to -present a General Outline of the System, in one continued Discourse; -and to introduce afterwards, in the form of Notes, what farther -elucidation any particular subject was thought to demand. Through the -whole, I have aimed at little more than a clear exposition of facts, -and a plain deduction of the conclusions grounded on them; nor shall -I claim any merit to myself, if, in the order which I have found it -necessary to adopt, some arguments may have taken a new form, and some -additions may have been made to a system naturally rich in the number -and variety of its illustrations. - -OF the qualifications which this undertaking requires, there is one -that I may safely suppose my self to possess. Having been instructed by -Di Hutton himself in his theory of the earth; having lived in intimate -friendship with that excellent man for several years, and almost in the -daily habit of discussing the questions here treated of; I have had the -best opportunity of understanding his views, and becoming acquainted -with his peculiarities, whether of expression or of thought. In the -other qualifications necessary for the illustration o a system so -extensive and various, I am abundantly sensible of my deficiency, and -shall therefore with great deference, and considerable anxiety wait -that decision from which there is no appeal. - - EDINBURGH COLLEGE, } - 1st March 1802. } - - - - - TABLE - - OF - - CONTENTS. - - - INTRODUCTION. Object of a Theory of the Earth. Division of minerals - into _Stratified_ and _Unstratified_. - - Page 1 - - - SECTION I. - - PHENOMENA PECULIAR TO STRATIFIED BODIES. - - 1. Materials of the Strata. - - Page 4 - - Present strata composed of the remains of more ancient rocks, § 1. - Proofs from calcareous strata, § 2.--from siliceous, § 3.--from - argillaceous, § 4.--from bituminous, § 5, 6. Absence of organized - remains from the strata called _primitive_, not universally true, - § 8, 9.--Term Primary substituted for Primitive. Composition from - the materials of more ancient rocks, § 10. - - - 2. Consolidation of the Strata. - - p. 15 - - Consolidation, what, § 11. Objections to aqueous consolidation, § - 12, 13, 14. Compression affects the action of fire on bodies, § - 15, 16, 17.--Igneous consolidation of minerals prove from fossil - wood, § 19.--From the flints in chalk, § 20.--from sandstone, - § 21.--from the calcareous strata, § 23, 24, 25.--from the - argillaceous, § 26, 27.--from the bituminous, § 28, 29.--from the - saline, § 32. Salt mines in Cheshire. Trona of Africa, § 54, 35. - - - 3. Position of the Strata. - - p. 40 - - Strata formed at the bottom of the sea, § 36. Apparent elevation - not produced by the retreat of the sea, § 37.--Strata, - horizontal, when formed, § 38, 39. Disturbance of the strata - proved from their inclined position § 40, 41, 42.--from shifts, - &c. § 42. Shifts of different dates, _ib._ Disturbance of the - primitive strata visible at their junction with the secondary, § - 43, 44. This disturbance produced by a force directed upward, § - 45, 46. This force the effect of subterraneous heat, § 47, 48. - - - SECTION II. - - PHENOMENA PECULIAR TO UNSTRATIFIED BODIES. - - 1. Metallic Veins. - - p. 57 - - Veins defined. They contain substances that were once in fusion, § - 49, 50. Metallic veins, native metals, &c. § 51. Native copper, § - 52. Manganese, § 53. Fragments of rocks included in veins, § 55. - Shifting and heaving of veins, § 56, 57. Veins of different dates, - § 58. Stratification not found in veins. Coating of the sides, - what, § 59. Metallic veins most common in primitive strata; but - not confined to them, § 60. - - 2. Whinstone. - - p. 66 - - Enumeration of stones of this genus, § 61. Whin, whether in veins - or in masses, resembles lava, § 62. Is a subterraneous lava, - § 63. Columnar structure an argument for fusion, § 64. Not - produced by drying, § 65. Whinstone penetrated by pyrites, § 66. - Induration of the strata in contact with whin, § 67 Coal charred - by whinstone veins, § 68. Disturbance of the strata by whinstone - veins, § 69. Phenomena of whin interposed between strata, § 70, - 71. Transition from whin to strata not gradual. § 72. Agates and - chalcedonies in whinstone, § 74. This stone melted and reproduced - from fusion by Sir James Hall, § 75. Mineral alkali found in it - by Dr Kennedy, _ib._ Whinstones of different formation, § 76. - Porphyry a species or variety of whinstone, §77. - - 3. Granite. - - p. 82 - - Granite defined. Exists in masses and veins, § 77. The basis - of other rocks, § 78. Its original fluidity inferred from - the crystallization of its parts, § 79. Its fusion, from the - structure of the Portsoy granite, § 80, 81.--from granite veins, - § 82. General conclusion as to the igneous origin of minerals, § - 83, 84, 85. Actual existence of subterraneous heat known from hot - springs, volcanoes, earthquakes, § 86. Volcanic fire seated deep - under the surface, § 87. Subterraneous heat not accompanied by - burning, § 88, 89. Transmission of subterraneous heat, so as to - produce hot springs, &c. § 90, 91. - - - SECTION III - - PHENOMENA COMMON TO STRATIFIED - AND UNSTRATIFIED BODIES. - - p. 97 - - Chemical agents which produce the decomposition of mineral - substances at the surface, § 92, 93. Mechanical agents, § 95, 96. - Proofs of wearing from the sea shore, § 97, 98. Rivers, § 99, - 100. Defiles among mountains, § 102. Supply of the soil from the - decomposition of rocks, § 103. Gravel in the soil, § 104, 105. - Gold found in the soil, § 106. Tin, § 107. Proofs of waste from - mountainous countries, § 108, 109. Structure of Valleys, § 111. - Transportation of stones, § 112. Nearest measure of the waste, - § 113. General remarks, § 114, 115. No production of minerals - on the surface, § 116. Reproduction at the bottom of the sea, § - 117. Continued system of decay and renovation, § 118. Defence - against the charge of impiety, 119. Antiquity and order of the - revolutions of the globe, § 120, 121, 122, 123, 124. Consistency - with the Sacred Writings, § 125. Scope of this theory of the - earth distinguishes it from others; beauty and extent of its - views, § 126. New facts, § 127. Comparison of this theory with - that of Buffon, § 129. Of Lazzaro Moro, § 130. _Plutonic_ system, - § 131. Distinguished by the principle of compression, § 132. - Explains the oblate figure of the earth, _ib._ Prejudices against - this system, § 133. What may be expected from the progress of - science, § 134. - - - NOTES AND ADDITIONS. - - NOTE I.--Origin of Calcareous Earth. - - p. 143 - - Dr Hutton's opinion on this subject accurately stated, § 135. - Misrepresented by Kirwan, § 136. - - NOTE II.--Origin of Coal. - - p. 147 - - Vegetable origin of coal. Opinion of Buffon, § 137.--of Arduino, - _ib._--of Lehman, § 138. Distinction attempted between wood coal - and mineral coal, § 139. Not of different origin, but gradually - pass one into the other, § 140. Bovey coal, § 141. Kirwan derives - the matter of mineral coal from the decomposition of hornblende, - &c. 143. Absurdity of this supposition, § 144, 145, 146, 147. - - NOTE III.--Primitive Mountains. - - p. 160 - - Lehman introduced the term Primitive mountains, § 149. Supposed - more ancient than organized bodies, § 150. Stratification of - primitive mountains denied by Pini, and maintained by Saussure, § - 151. - - NOTE IV.--Primary Strata not Primitive. - - p. 163 - - Shells found in primary strata, § 152. Sandstone in primary - mountains, § 153. Quartzy sand in the schistus of the Grampians, - _ib._ Rocks distinguished by Werner into three orders, § 154. - Objections to this arrangement, § 155. - - NOTE V.--Transportation of the Materials - of the Strata. - - p. 171 - - The transportation of materials, objected to by the Neptunists, is - implied in their own system, § 156, 157, 158. Proofs of great - transportation from the animal and vegetable remains, found in - rocks, § 160. - - NOTE VI.--Kirwan's Notion of Precipitation. - - p. 180 - - Difficulty, of precipitating the materials dissolved in the chaotic - fluid, § 162. Insufficiency of the explanation attempted, _ib._ - - NOTE VII.--Compression in the Mineral Regions. - - p. 181 - - Effects ascribed to compression by Newton, compared will the - effects ascribed to it in this theory, § 163. Fallacy of Kirwan's - argument concerning the fusion of Carrara marble, § 165, 166. - Heat of the mineral region may be supported without fuel, § 167. - Quotation from Newton's Optics, _ib._ General remarks, § 169. - - NOTE VIII.--Sparry Structure of Calcareous - Petrifactions. - - p. 190 - - Sparry and organic structure co-exist in certain fossils, § 171. - Sparry and stratified structure co-exist in gneiss, marble, &c. § - 172. - - NOTE IX.--Petroleum, &c. - - p. 194 - - Petroleum, &c. from the distillation of coal, § 173. Gradation from - petroleum to coal often met with, § 174. Connection of amber and - coal, § 175. Why mines of blind coal have not always petroleum - mines near them, § 176. - - NOTE X.--The Height above the Level of the Sea, - at which Marks of - Aqueous Deposition are now found. - - p. 199 - - These marks consist either in stratification or in marine objects, - § 177. The marks of stratification observed, 14739 feet above - the sea, § 178. Shells in Peru, 14190, § 179. Kirwan's mistake - concerning these shells, § 180. His error similar to VOLTAIRE'S, - § 181. - - NOTE XI.--Fracture and Dislocation - of the Strata. - - p. 204 - - Slips, § 182. Rib of limestone in a slip near Huddersfield, § 183, - 184. Singular fracture of pudding-stones at Oban in Argyleshire, - § 185. Similar phenomena observed by Saussure between Nice and - Genoa, _ib._ Remarks on it, § 186. - - NOTE XII.--Elevation and Inflection - of the Strata. - - p. 209 - - Junction of primary and secondary strata, § 187. Breccia - incumbent on the primary, § 188. Junction of the primary and - secondary strata: At Torbay in Devonshire, § 190,--coast of - Berwickshire, § 191,--Cullen in Banffshire, § 193,--Ardencaple - in Dunbartonshire, Arran, &c. § 194,--Pembrokeshire, - § 195,--Jedburgh, § 196,--Ingleborough in Yorkshire, § - 197,--Cumberland, § 198. Inflection of the strata, § 199. - Remarkable instances in the Alps and Pyrenees, § 200, 201,--on - Ben-Lawers in Perthshire, § 202,--coast of Berwickshire, - _ib._--Plymouth, § 203. Strata suffering such inflections - have been soft and ductile, § 204. General property of these - inflections, § 205, 206. uniform stretch of the primary strata, - § 207. Inferences as to the nature of the elevating force, § - 208. Imperfection of other theories. Crystallisation, _ib._ - Marks of undulæ in the schistus, § 209. Elevation of the strata - a stronghold of the Huttonian theory, § 210. Elevation of the - strata enables us to see far into the interior of the earth, § - 211. - - NOTE XIII.--Metallic Veins. - - p. 239 - - Specimens of native iron, § 212, 213. Margraaf's specimen, § 214. - Kirwan's hypothesis, § 215. Increase of the specific gravity of - native gold by fusion, no argument against its igneous origin, - § 216. Specimens of gold and silver shooting through quartz, an - argument in favour of the Huttonian theory, § 218, 219. Proof in - favour of the same from chalcedony including calcareous spar, - § 220. Matter that fills veins not from above or from either - side, § 221. Opinion of the Neptunists, § 222. Supposed fact - that veins are less rich as the depth increases, § 223. No marks - of horizontal deposition in veins; their coating differs from - stratification, § 224. Neptunists appear to be misled by the term - Stratification, § 225, 226. Veins heave or shift one another, - § 227. Vast force employed for that purpose, § 228. Veins of - different formation, § 231. Pieces of rock insulated in veins, § - 232. Supposition that veins have been filled by infiltrations, - absurd, 233. _Lenticular_ veins, and Pipe veins, § 234. - - NOTE XIV.--On Whinstone. - - p. 260 - - Whinstone, neither of volcanic nor aqueous formation, § 235. - Zeolite and carbonate of lime included in whinstone, but not in - lava, _ib._ Not introduced by infiltration, § 236. Disposition - of whinstone mountains differs from that of streams of lava, - § 237. This argument first employed by Mr Strange, § 238. His - general views of this subject, § 239. Explanation of the regular - structure of whinstone hills, according to Dr Hutton's theory, § - 240. Many hills supposed to be extinguished volcanoes, are rocks - of real whinstone that has flowed deep under the surface. Vein - of whinstone mistaken for a stream of lava by Faujas, § 241, - 242. Submarine volcanoes of Dolomieu, § 243. Objections to this - theory, § 244, 245. Dolomieu in another place contends for the - aqueous formation of basaltes, § 246. His arguments answered; - also those of Bergman, § 248, 249. Argument of WERNER for the - aqueous origin of basaltes, § 250. Remarks on the supposed - gradual transition of basaltes to argillaceous schistus, § - 251, 252. Of the shells said to be found in basaltes, § 253. - Instances from Portrush in Ireland, and from Cerigo on the - Coast of Greece, _ib._ and 254,--from the Veronese, § 255. - Objections to the Neptunian formation of whinstone, founded on - the difference between it and the contiguous stratified rocks, - § 256. On the resemblance of the strata below and above certain - masses of whinstone, § 257. On the irregularity of the thickness - of those masses, § 258. Wedge form masses of whinstone included - between strata, § 259. Consequences of this wedge form, § 260. - Sandstone fragments included in whin, § 261, 262. Bending of - the strata contiguous to whinstone, § 264. Induration, § 265, - 266. Charring of coal by whin, § 267. Of the manner in which the - bitumen may have been driven off by heat, § 268. Two kinds of - fossil coke, § 269. Graduation into plumbago, _ib._ and 270. Only - remaining objection obviated by Sir James Hall's experiments, § - 271. - - NOTE XV.--On Granite. - - p. 307 - - Granite veins of two kinds, § 274. Veins Of which the communication - with large masses of the same stone is not visible: At the Isle - of Coll in the Hebrides, § 275,--at Portsoy, § 276,--in Cornwall, - § 277,--in Glentilt, § 278. Veins visibly connected with larger - masses. Argument furnished by them in favour of this theory, § - 279, 280. Impossibility of their being formed by infiltration, § - 281. Veins of this kind in Arran, § 282,--Galloway, § 283,--sides - of Loch Chloney, Invernessshire, §284,--St Michael's Mount, - Cornwall § 285. Fragments of schistus contained in granite, § 287. - - 2. Granite of Portsoy. - - p. 320 - - Description of this granite, § 288. Pierre graphique of M. Patrin - not perfectly the same with that of Portsoy, § 289. Quartz - crystallized in the pierre graphique, § 290. Instances of quartz - crystallized in other granites. In that of St Agnes in Cornwall, - § 291. Whether this crystallization is only found in secondary - granites, § 292. - - 3. Stratification of Granite. - - p. 326 - - Question stated concerning the stratification of granite, § 293. - Remarkable examples of stratified granite at Chorley Forest, - Leicestershire, and at Fassnet _Water_ in Berwickshire, § 295. - Stratification of Mont Blanc, and the Aiguilles of Chamouni - maintained by Saussure, § 296, 297. Seems nevertheless doubtful, - § 298. In the granite mountains of Arran doubtful; § 300. - Explanation of the stratification of granite in this theory, § - 301. If granitic veins were found proceeding from real granitic - strata, they could not be explained on the principles here laid - down, § 302. No such veins have been discovered, § 303. Answer to - an objection made to the igneous origin of granitic mountains, § - 304, 305. Of the proportion of the earth's surface occupied by - granite rocks, § 306. Not exceeding a ninetieth part, § 307, 311. - Extent of granite in Scotland erroneously estimated by Dr Hutton, - § 312. Amounts perhaps to a twenty-fourth of the whole surface, § - 313. Observations on Mr Kirwan's opinion, § 314. - - NOTE XVI.--Rivers and Lakes. - - p. 350 - - The rivers have hollowed out the valleys, § 315. Illustration - from the course of the Danube, § 316. Courses of many rivers - retain marks of having consisted of a series of lakes, § 317, - 318. Filling up and draining of lakes, § 320. Instances from - the lakes in Cumberland, § 321. Lake of Geneva, § 322. Lakes in - North America, _ib._ Cataracts, § 323. Difficulties in explaining - the generation and continuance of lakes exemplified in that of - Geneva, § 324. Attempt to resolve these difficulties, § 325, 326, - 327, 328. All lakes not equally subject to them, § 329. Wasting - of the land by the rivers, proved from the mouths of rivers on - bold coasts, § 330. Examples from Cornwall, § 331. - - NOTE XVII.--Remains of Decomposed Rocks. - - p. 371 - - Plain of Crau, § 334. Its gravel from the decomposition of - pudding-stone, § 385. Same true of much of the gravel in this - island, § 337, 338. Mount Rigi in Switzerland the remains of a - body of pudding-stone, § 339. Measure of the destruction in the - stratified rocks sometimes, afforded by the unstratified, § 340, - 341. Rate at which the elevation of mountains has been supposed - to decrease, § 342. - - NOTE XVIII.--Transportation of Stones, &c. - - p. 381 - - Gravel smaller and rounder the farther from its native place, § - 343. Different sources of _caillou roulés_, § 344, 345. Stones - that have begun their migration before the cutting out of the - present valleys, § 346. Declivity necessary to enable stones - to travel from the top of Mont Blanc to the top of Mont Jura, - § 347. Granite from Mont Blanc found eastward in the valley of - the Drance, § 348. Machinery employed by nature in transporting - rocks, § 349, 350. Instances of transported stones of great - size,--from the vicinity of Geneva, § 351, 352,--from the Isle - of Arran, 353. How gravity may contribute to the moving of large - stones, even when the declivity is small, § 354. Rocking-stones, - § 355. Stone in Borrowdale,--in the valley of Urseren, § 356. - Large stones are sometimes the remains of veins, § 357. Of - the hypothesis of a _debacle_, § 358. Structure of valleys - unfavourable to this hypothesis, § 359, 360. Particularly of - valleys close at the ends, § 361, 362. Whether the supposition of - a _debacle_ is necessary to explain the moving of large masses - of rock, § 364. Whether the abrupt faces of hills indicate the - existence of any sudden torrent, &c. § 365. Fact concerning the - steep faces of the mountains in the south of Africa, § 366. A - fact stated that would lead necessarily to belief in a _debacle_; - no example of it has yet occurred, § 367. - - NOTE XIX.--Transportation of Materials - by the Sea. - - p. 413 - - Of the manner in which the _detritus_ of the land is spread out - over the bottom of the sea, § 369, 370. Seas rendered shallower, - § 371. Sand banks, § 372. Great system of currents traced in the - Atlantic, § 373, 374. How far this transportation of materials - may affect the earth's diurnal motion, § 376, 377. Kirwan's - misapprehension of Frisi, and of Major Rennell, § 378, 379. His - mistake about the tides, § 380, 381,--and about the formation of - sand banks, § 384. - - NOTE XX.--Inequalities of the - Planetary Motions. - - p. 437 - - These inequalities all periodical, § 385. Circumstances on which - this depends, § 386. Affinity of this conclusion to that which Dr - Hutton has established with respect to the changes at the surface - of the earth, § 387. - - NOTE XXI.--Changes in the Apparent - Level of the Sea. - - p. 441 - - Relative level of the sea and land subject to change, § 388. Proofs - that it has sunk, on the shores of this island, § 389,--on the - coasts of France and Flanders, § 390, 391,--on the shores of the - Baltic, § 392. This has not arisen from the depression of the - sea, but from the elevation of the land, § 393, 394. The surface - of the Hadriatic higher now than formerly, § 395, 396. Also of - the Mediterranean, § 398. Irregularities in these changes, § 399, - 400. Hypothesis of Frisi, that towards the equator the sea is - every where rising, § 401. Disproved, _ib._ Conclusion, § 402. - - NOTE XXII.--Fossil Bones. - - p. 458 - - Vegetable and animal remains contained in the fossil kingdom, § - 403. Of those that are enveloped or penetrated with calcareous - earth, § 405, 406. Of the bones buried in the loose earth, - § 407. Bones in Siberia referred to the rhinoceros and the - elephant, § 408. Those on the Ohio doubtful, § 408, 409. Opinion - of Camper, § 410.--of Cuvier, § 411. Objections to the latter, - _ib._ Enumeration of five _species_ of animals now extinct, § - 412. Change in the animal, and vegetable kingdom may account for - bones found in countries where no analogous species now exists, - § 414. Proofs that the animals whose bones are found in Siberia - inhabited that country, § 415-417. - - NOTE XXIII.--Geology of Kirwan and De Luc. - - p. 477 - - These authors have improperly drawn religion into their quarrel - with Dr Hutton, § 419. De Luc writes a history of what befel the - earth before the creation of the sun, § 420. Remarks on Kirwan's - geological writings, § 422, 423, 424, 425. - - NOTE XXIV.--System of Buffon. - - p. 483 - - In what Buffon's theory of the earth and Dr Hutton's agree, - and in what they differ, § 426, 427. Great merit of Buffon, - notwithstanding his errors, § 428. - - NOTE XXV.--Figure of the Earth. - - p. 488 - - Physical cause of the earth's oblate figure not obvious from its - present condition, § 429. How explained by the Neptunists, § - 430. Examination of their solution, § 431, 432. Contradiction - implied in it, § 433. Insufficiency of Buffon's explanation, § - 434. Of the principle on which the oblateness of the earth may - be accounted for in Dr Hutton's theory, § 435. Of the changes - that would happen in the figure of a terraqueous body like the - earth, supposing it ever so irregular, § 436, 437, 438. Two - different causes of change, _ib._ Ultimate figure, that by which - the causes of change are best resisted, § 439. Spheroidal figure, - never perfectly acquired, § 440. Agreement of this theory with - observation, § 441. Probable extension of the system of waste, - and renovation to the other planets, § 442, 443. Confirmation - from the system of Saturn, § 444, 445. - - NOTE XXVI.--Prejudices relating to - the Theory of the Earth. - - p. 510 - - Alleged by some that a theory of the earth ought not at present to - be attempted, § 446. The quick succession of geological theories - has partly arisen from their object being misunderstood, § 447. A - succession of theories is often a continued approximation to the - truth, § 448. The more various the phenomena of any class, the - greater the chance of discovering their true cause, § 449. Reason - to think that the leading facts in geology are now known, § 450, - 451. A tendency may be observed in geological systems to approach - to one another, and to the Huttonian, § 452. Example from that - of Saussure, § 453,--of Dolomieu, § 454, 455. The discoveries of - Dr Black were necessary for understanding the true theory of the - earth, § 457. Use of theory in matters of observation, § 458, &c. - - - - - ILLUSTRATIONS, &c. - - -A VERY little attention to the phenomena of the mineral kingdom, is -sufficient to convince us, that the condition of the earth's surface -has not been the same at all times that it is at the present moment. -When we observe the impressions of plants in the heart of the hardest -rocks; when we discover trees converted into flint, and entire beds of -limestone or of marble composed of shells and corals; we see the same -individual in two states, the most widely different from one another; -and, in the latter instance, have a clear proof, that the present land -was once deep immersed under the waters of the ocean. If to this we -add, that many masses of rock, the most solid and compact, consist of -no other materials but sand and gravel; that, on the other hand, loose -gravel, such as is formed only in beds of rivers, or on the sea shore, -now abounds in places remote from both: if we reflect, at the same -time, on the irregular and broken figure of our continents, and the -identity of the mineral strata on opposite sides of the same valley, or -the same inlet of the sea; we shall see abundant reason to conclude, -that the earth has been the theatre of many great revolutions, and that -nothing on its surface has been exempted from their effects. - -To trace the series of these revolutions, to explain their causes, and -thus to connect together all the indications of change that are found -in the mineral kingdom, is the proper object of a THEORY OF THE EARTH. - -But, though the attention of men may be turned to the theory of the -earth by a very superficial acquaintance with the phenomena of geology, -the formation of such a theory requires an accurate and extensive -examination of those phenomena, and is inconsistent with any but a -very advanced state of the physical sciences. There is, perhaps, in -those sciences, no research more arduous than this; none certainly -where the subject is so complex; where the appearances are so extremely -diversified, or so widely scattered, and where the causes that have -operated are so remote from the sphere of ordinary observation. Hence -the attempt! to form a theory of the earth are of very modern origin, -and as, from the simplicity of its subject astronomy is the eldest, so, -on account of the complexness of its subject, geology is the youngest -of the sciences. - -It is foreign from the present purpose to enter on any history of -the systems that, since the rise of this branch of science, have -been invented to explain the phenomena of the mineral kingdom. It is -sufficient to remark, that these systems are usually reduced to two -classes, according as they refer the origin of terrestrial bodies -to FIRE or to WATER; and that, conformably to this division, their -followers have of late been distinguished by the fanciful names of -_Vulcanists_ and _Neptunists_. To the former of these Dr Hutton belongs -much more than to the latter; though, as he employs the agency both of -fire and of water in his system, he cannot, in strict propriety, be -arranged with either. - -In the succinct account which I am now about to give of this system, I -shall consider the mineral kingdom as divided into two parts, namely, -stratified and unstratified substances I shall treat, first, of the -phenomena peculiar to the stratified; next, of those peculiar to the -unstratified; and, lastly, of the phenomena common to both. Beginning, -then, with the first, the subject naturally divides itself into three -branches; viz. the _materials_ the _consolidation_, and the _position_ -of the strata. - - - - - SECTION I. - - OF THE PHENOMENA PECULIAR TO STRATIFIED BODIES. - - - 1. _Materials of the Strata._ - -1. IT is well known that, on removing the loose earth which forms the -immediate surface of the land, we come to the solid rock, of which a -great proportion is found to be regularly disposed in strata, or beds -of determinate thickness, inclined at different angles to the horizon, -but separated from one another by equidistant superficies, that often -maintain their parallelism to a great extent. These strata bear such -evident marks of being deposited by water, that they are universally -acknowledged to have had their origin at the bottom of the sea; and -it is also admitted, that the materials which they consist of, were -then either soft, or in such a state of comminution and separation, -as renders them capable of arrangement by the action of the water in -which they were immersed. Thus far most of the theories of the earth -agree; but from this point they begin to diverge, and each to assume -a character and direction peculiar to itself. Dr Hutton's does so, by -laying down this fundamental proposition, That in all the strata we -discover proofs of the materials having existed as elements of bodies, -which must have been destroyed before the formation of those of which -these materials now actually make a part.[1] - -[Footnote 1: Hutton's Theory, vol. I p. 20, &c.] - -2. The calcareous strata are the portion of the mineral kingdom that -gives the clearest testimony to the truth of this assertion. They often -contain shells, corals, and other exuviæ of marine animals in so great -abundance, that they appear to be composed of no other materials. -Though these remains of organized bodies are now converted into stone -or into spar, their shape and interior structure are often so well -preserved, that the species of animal or plant of which they once made -a part, can still be distinguished and pointed out among the living -inhabitants of the ocean. - -Others of the calcareous strata appear to be composed of fragments of -some ancient rocks, which, after having been broken, have been again -united into a compact stone. In these we find pieces clearly marked -as having been once continuous but now placed at a distance from one -another, and exhibiting exactly the same appearances as if they floated -in a fluid of the same specific gravity with themselves. - -From these, therefore, and a variety of similar appearances, Dr Hutton -concludes, that the materials of all the calcareous strata have been -furnished, either from the dissolution of former strata, or from the -remains of organized bodies. But, though this conclusion is meant to be -extended to all the calcareous strata, it is not asserted that every -cubic inch of marble or of limestone contains in it the characters of -its former condition, and of the changes through which it has passed. -It may, however, be safely affirmed, that there is scarce any entire -stratum where such characters are not to be found. These must be -held as decisive with respect to the whole system of strata to which -they belong; they prove the existence of calcareous rocks before the -formation of the present; and, as the destruction of those is evidently -adequate to the supply of the materials of these that we now see, to -look for any other supply were superfluous, and could only embarrass -our reasonings by the introduction of unnecessary hypotheses.[2] - -[Footnote 2: NOTE I.] - -3. The same conclusions result from an examination of the siliceous -strata; under which we may comprehend the common sandstone, and also -those pudding-stones or breccias where the gravel consists of quartz. -In all these instances, it is plain, that the sand or gravel existed in -a state quite loose and unconnected, at the bottom of the sea, previous -to its consolidation into stone. But such bodies of gravel or sand -could only be formed from the attrition of large masses of quartz, or -from the dissolution of such sandstone strata as exist at present; for -it will hardly be alleged, that sand is a crystallization of quartz, -formed from that substance, when it passes from a fluid to a solid -state. - -Those pudding-stones in which the gravel is round and polished, carry -the conclusion still farther, as such gravel can only be formed in the -beds of rivers or on the shores of the sea; for, in the depths of the -ocean, though currents are known to exist, yet there can be no motion -of the water sufficiently rapid to produce the attrition required to -give a round figure and smooth surface to hard and irregular pieces -of stone. There must have existed, therefore, not only a sea, but -continents, previously to the formation of the present strata. - -The same thing is clearly shown by those petrifactions of wood, where, -though the vegetable structure is perfectly preserved, the whole mass -is siliceous, and has, perhaps, been found in the heart of some -mountain, deep imbedded in the solid rock. - -4. Characters of the same import are also found among the argillaceous -strata, though perhaps more rarely than among the calcareous or -siliceous. Such are the impressions of the leaves and stems of -vegetables; also the bodies of fish and amphibious animals, found very -often in the different kinds of argillaceous schistus, and in most -instances having the figure accurately preserved, but the substance -of the animal replaced by clay or pyrites. These are all remains -of ancient seas or continents; the latter of which have long since -disappeared from the surface of the earth, but have still their memory -preserved in those archives, where nature has recorded the revolutions -of the globe. - -5. Among bituminous bodies, pit-coal is the only one which constitutes -regular and extensive strata; and no fossil has its origin from the -waste of former continents, marked by stronger and more distinct -characters. Not to mention that the coal strata are alternated with -those that have been already enumerated, and that they often contain -shells and corals, perfectly mineralized, it is sufficient to remark, -that there are entire beds of this fossil, which appear to consist -wholly of wood, and in which the fibrous structure is perfectly -preserved. From these instances, the appearances of vegetable -structure may be traced through all possible gradations, down to an -evanescent state. This last state is undoubtedly the most common; and -though coal does not then, on bare inspection, make known its vegetable -origin, yet, if we take it in connection with the other terms of the -series, as we may call them; if we consider that the two extremes, viz. -coal, with the vegetable structure perfect, and coal without any such -structure visible, are often found in the same or in contiguous beds; -and, if we remark, that through all these gradations coal contains -nearly the same chemical elements, and yields, on analysis, bitumen and -charcoal, combined with a greater or less proportion of earth: if we -take all these circumstances into account, we cannot doubt that this -fossil is every where the same, and derives its origin from the trees -and plants that grew on the surface of the earth before the formation -of the present land. - -6. Dr Hutton has further observed, that if those ancient continents -were at all similar to the present, we can be at no loss to account for -the want of any distinct mark of vegetable organization in the greater -part of the coal strata. It is plain, that the daily waste of animal -and vegetable substances on the surface of the earth, must disengage -a great quantity of oily as well as carbonic matter, which, with -whatever element it is at first combined, is ultimately delivered into -the ocean. Thus, the oily or fuliginous parts of animal and vegetable -substances, let loose by burning, first ascend into the atmosphere, but -are at length precipitated, and either fall immediately into the sea, -or are, in part at least, washed down into it from the land. From other -causes also, much vegetable matter is carried down by the rivers; and -the whole quantity of animal and vegetable substances thus delivered -into the sea, must be very considerable, amounting annually to the -whole residuum of those substances, not employed in the maintenance or -reproduction of animal and vegetable bodies. Whether chemically united -to the waters of the ocean, or simply suspended in them, this matter is -at last precipitated, and, mingling with earthy substances, is formed -into strata, the place of which will be determined by the currents, the -position of the present continents, and many other circumstances not -easily enumerated. - -If, then, an order of things similar to what we now see, existed before -the formation of the present strata, it would necessarily happen, that -the animal and vegetable substances, diffused through the ocean, being -separated from the water, would be deposited at the bottom of the -sea, and, in the course of ages, would form beds, less or more pure, -according to the quantity of earth and other substances deposited -at the same time. These beds being consolidated and mineralized by -operations that are afterwards to be considered, have been converted -into pit-coal, the parts of which are impalpable, and retain nothing of -their primitive structure.[3] - -[Footnote 3: NOTE II.] - -If, then, the formation of coal from animal and vegetable bodies be -admitted, the general position which derives the origin of the strata -from the waste of former land, as it is applicable to all the kinds -already enumerated, and of course to all those with which they are -alternated, comprehends a very large portion of the earth's surface. -It comprehends, indeed, all the strata usually distinguished by the -name of _Secondary_; but there is another great division of the mineral -kingdom, viz. the rocks, called _Primitive_, which, as they are never -alternated with the secondary, but are always inferior to them, must -be further examined, before we can decide whether the same conclusion -extends to them or not. - -7. Here it must be carefully observed, that, among the primary rocks, -the granite is not meant to be included, except where that stone is -stratified, and either coincides with veined granite or with gneiss. -The primitive strata, in Dr Hutton's theory, comprehend, besides -gneiss, the micaceous, chlorite, hornblende, and siliceous schistus, -together with slate, and some other kinds of argillite; to which we -must add, serpentine, micaceous limestone, and the greater part of -marbles. These are mostly distinguished by their laminated structure, -by having their planes much elevated with respect to the horizon, -and by belonging more to the mountainous than the level parts of the -earth's surface. They rarely contain vestiges of organized bodies; -so rarely, indeed, that they were called primitive by the geologists -who first distinguished them from other rocks, on the supposition of -their being part of the primeval nucleus of the globe, which had never -undergone any change whatsoever; but this, I believe, has now almost -ceased to be the opinion of any geologist.[4] The Neptunists hold the -rocks, here enumerated, and also granite, to be produced by aqueous -deposition; but maintain them to be in the strictest sense primeval, -and of a formation antecedent to all organized bodies. - -[Footnote 4: NOTE III.] - -8. In opposition to this, Dr Hutton maintained, that the primary -schistus, like all the other strata, was formed of materials deposited -at the bottom of the sea, and collected from the waste of rocks still -more ancient. When, therefore, he conformed to the received language -of mineralogists, by calling these strata primitive, he only meant -to describe them as more ancient than any other strata now existing, -but not as more ancient than any that ever had existed. They are -distinguished, in his system, by the name of _Primary_, rather than of -_Primitive_ strata. - -That the account now given of their origin is well founded, may be -proved by unquestionable facts. For, first, though, agreeably to the -observation just made, the ancient strata do but rarely contain any -remains of organized bodies, they are not entirely destitute of them. -Different places in this island have been pointed out by Dr Hutton, -where marine objects have been discovered in primary limestone, either -by himself or others, and it would not be difficult to add more -instances of the same kind.[5] In Dauphine, coal, which is certainly a -derivative substance, has been found among mountains which have a title -to the character of primitive, such as no one will dispute. These facts -put the composition of such rocks from loose materials, beyond all -doubt, and also prove their formation to be posterior to the existence -of an animal and vegetable system. They do indeed prove this in the -strictest sense, only of the particular beds in which they are found; -but as these beds are in all other respects as much to be accounted -primary as any part of the mineral kingdom, it is evident that the -negative instances are here of no force, and that nothing can be gained -to the adversaries of this opinion by denying it in general, if they -are obliged to admit it in a single case. - -[Footnote 5: NOTE IV.] - -9. Again, it is certain, as Dr Hutton remarks, that there are few -considerable bodies of schistus, even the most decidedly primitive, -where sand and gravel may not in some parts be observed. Indeed, it is -not only true that they are to be found in some parts of them; but, -in fact, among many of the primitive mountains, we find large tracts, -composed entirely of a schistose and much indurated sandstone, in beds -highly inclined, sometimes alone, sometimes alternated with other -schisti. In many of them, the sand of which they consist appears to be -entirely of granite, from the detritus of which rock it should seem -that they were chiefly formed. - -10. Thus we conclude, that the strata both primary and secondary, -both those of ancient and those of more recent origin, have had their -materials furnished from the ruins of former continents, from the -dissolution of rocks, or the destruction of animal or vegetable -bodies, similar, at least in some respects, to those that now occupy -the surface of the earth. This conclusion is not indeed proved of every -individual portion of rock, but it is demonstrated of many and large -parts, and those scattered indifferently through all the varieties of -the strata; and therefore, from the rules of the strictest reasoning, -we must infer, that the whole is derived from the same origin.[6] - -[Footnote 6: NOTE V.] - -Thus far concerning the materials of the strata; and, as these were -originally loose and unconnected, we must next consider by what means -they were consolidated into stone. - - - 2. _Consolidation of the Strata_. - -11. Though Dr Hutton has no where defined the meaning of the term -consolidation, he has been scrupulously exact in using it constantly -in the same sense. He understands by it, not merely that quality in a -hard body, by which its parts cohere together, but also that by which -it fills up the space comprehended within its surface, being to sense -without porosity, and impervious to air and moisture. - -Now, a porous mass of unconnected materials, such as the strata appear -originally to have been, can acquire hardness and solidity only in two -ways, that is, either when it is first reduced by heat into a state of -fusion, or at least of softness, and afterwards permitted to cool; or -when matter that is dissolved in some fluid menstruum, is introduced -along with that menstruum into the porous mass, and, being deposited, -forms a cement by which the whole is rendered firm and compact. Fire -and water, therefore, are the only two physical agents to which we can -ascribe the consolidation of the strata; and, in order to determine to -which of them that effect is to be attributed, we must inquire whether -there are any certain characters that distinguish the action of the one -from that of the other, and which may be compared with the phenomena -actually observed among mineral substances. - -12. First, then, it is evident, that the consolidation produced by the -action of water, or of another fluid menstruum, in the manner just -referred to, must necessarily be imperfect, and can never entirely -banish the porosity of the mass. For the bulk of the solvent, and of -the matter it contained in solution, being greater than the bulk of -either taken singly, when the latter was deposited, the former would -have sufficient room left, and would continue to occupy a certain -space in the interior of the strata. A liquid solvent, therefore, could -never shut up the pores of a body to the entire exclusion of itself; -and, had mineral substances been consolidated, as here supposed, the -solvent ought either to remain within them in a liquid state, or if -evaporated, should have left the pores empty and the body pervious to -water. Neither of these however, is the fact; many stratified bodies -are perfectly impervious to water, and few mineral substances contain -water in a liquid state. That they sometimes contain it, chemically -united to them, is no proof of their solidity having been brought -about by that fluid; for such chemical union is as consistent with the -supposition of igneous as of aqueous consolidation, since the region in -which the fire was applied, on every hypothesis must have abounded with -humidity. - -13. Again, if water was the solvent by which the consolidating matter -was introduced into the interstices of the strata, that matter could -consist only of such substances as are soluble in water, whereas -it consists of a vast variety of substances, altogether insoluble -either in it, or in any single menstruum whatsoever. The strata are -consolidated, for example, by quartz, by fluor, by feldspar, and by all -the metals, in their endless combinations with sulphureous bodies. To -affirm that water was ever capable of dissolving these substances, is -to ascribe to it powers which it confessedly has not at present; and, -therefore, it is to introduce an hypothesis, not merely gratuitous, but -one which, physically speaking, is absurd and impossible. - -This is not all, however; for, even if this difficulty were to be -passed over, it would still be required to explain, how the water, -which, together with the matter which it held in solution, had -insinuated itself into the pores of the strata, became suddenly -disposed to deposit that matter, and to allow it, by crystallization -or concretion, to assume a solid form.[7] The Neptunists must either -assign a sufficient reason for this great and universal change, or must -expect to see their system treated as an inartificial accumulation -of hypotheses which assigns opposite virtues to the same subject, -and is alike at variance with nature and with itself; in a word, a -system that might pass for the invention of an age, when as yet sound -philosophy had not alighted on the earth, nor taught man that he is -but the minister and interpreter of nature, and can neither extend his -power nor his knowledge a hair's-breadth beyond his experience and -observation of the present order of things.[8] - -[Footnote 7: NOTE VI.] - -[Footnote 8: Homo naturæ minister, et interpres tantùm facit et -intelligit, quantùm de naturæ ordine re, vel mente, observaverit: nec -amplius scit, aut potest.--Nov. Org. lib. i. aph. 1.] - -14. Such are the more obvious, but I think unanswerable objections, -that may be urged against the aqueous consolidation of the strata. -It is true, that stony concretions, some of them much indurated, are -formed in the humid way under our eyes. Very particular conditions, -however, are required for that purpose, and conditions such as can -hardly have existed at the bottom of the sea. First. The water must -dissolve the substance of which the concretion is to be formed, as it -actually does in the case of calcareous, and in certain circumstances, -in that of siliceous, earth. Secondly. It must be separated from -that substance, as by evaporation, or by a combination of the matter -dissolved with some third substance, to which it has a greater affinity -than to water, so as to form with it an insoluble compound. Lastly, -the water that is deprived of its solution must be carried off, and -more of that which contains the solution must be supplied, as sometimes -happens where water runs in a stream, or drops from the roof of a -cavern. The two last conditions are peculiarly inapplicable to the -bottom of the sea, where the state of the surrounding fluid would -neither permit the water that was deprived of its solution from being -drawn off, nor that which contained the solution from succeeding it. - -It is further to be observed, that the consolidation of stalactitical -concretions, that is, the filling up of their pores, is always -imperfect, and is brought about by the repeated action of the fluid -running through the porous mass, and continuing to deposit there -some of the matter it holds in solution. This, which is properly -infiltration, is incompatible with the nature of a fluid, either -nearly, or altogether quiescent. - -15. In order to judge whether objections of equal weight can be opposed -to the hypothesis of igneous consolidation, we must attend to a very -important remark, first made by Dr Hutton, and applied with wonderful -success to explain the most mysterious phenomena of the mineral kingdom. - -It is certain, that the effects of fire on bodies vary with the -circumstances under which it is applied to them, and, therefore, a -considerable allowance must be made, if we would compare the operation -of that element when it consolidated the strata, with the results of -our daily experience. The materials of the strata were disposed, as we -have already seen, loose and unconnected, at the bottom of the sea; -that is, even on the most moderate estimation, at the depth of several -miles under its surface. At this depth, and under the pressure of a -column of water of so great a height, the action of heat would differ -much from that which we observe here upon the surface; and, though -our experience does not enable us to compute with accuracy the amount -of this difference, it nevertheless points out the direction in which -it must lie, and even marks certain limits to which it would probably -extend. - -The tendency of an increased pressure on the bodies to which heat is -applied, is to restrain the volatility of those parts which otherwise -would make their escape, and to force them to endure a more intense -action of heat. At a certain depth under the surface of the sea, the -power even of a very intense heat might therefore be unable to drive -off the oily or bituminous parts from the inflammable matter there -deposited, so that, when the heat was withdrawn, these principles -might be found still united to the earthy and carbonic parts, forming -a substance very unlike the residuum obtained after combustion under -a pressure no greater than the weight of the atmosphere. It is in -like manner reasonable to believe, that, on the application of heat -to calcareous bodies under great compression, the carbonic gas would -be forced to remain; the generation of quicklime would be prevented, -and the whole might be softened, or even completely melted; which last -effect, though not directly deducible from any experiment yet made, is -rendered very probable, from the analogy of certain chemical phenomena. - -16. An analogy of this kind, derived from a property of the barytic -earth, was suggested by that excellent chemist and philosopher, the -late Dr BLACK. The barytic earth, as is well known, has a stronger -attraction for fixed air than common calcareous earth has, so that the -carbonate of barytes is able to endure a great degree of heat before -its fixed air is expelled. Accordingly, when exposed to an increasing -heat, at a certain temperature, it is brought into fusion, the fixed -air still remaining united to it: if the heat be further increased, -the air is driven off, the earth loses its fluidity, and appears in -a caustic state. Here, it is plain, that the barytic earth, which is -infusible, or very refractory, _per se_, as well as the calcareous, -owes its fusibility to the presence of the fixed air; and it is -therefore probable, that the same thing would happen to the calcareous -earth, if by any means the fixed air were prevented from escaping when -great heat is applied to it. This escape of the fixed air is exactly -what the compression in the subterraneous regions is calculated to -prevent, and therefore we are not to wonder if, among the calcareous -strata, we find marks of actual fusion having taken place.[9] - -[Footnote 9: NOTE VII.] - -17. These effects of pressure to resist the decomposition, and augment -the fusibility of bodies, being once supposed, we shall find little -difficulty in conceiving the consolidation of the strata by heat, since -the intervals between the loose materials of which they originally -consisted may have been closed, either by the softening of those -materials, or by the introduction of foreign matter among them, in -the state of a fluid, or of an elastic vapour. No objection to this -hypothesis can arise from the considerations stated in the preceding -case; the solvent here employed would want no pores to lodge in after -its work was completed, nor would it find any difficulty in making its -retreat through the densest and most solid substances in the mineral -kingdom. Neither can its incapacity to dissolve the bodies submitted -to its action be alleged. Heat is the most powerful and most general -of all solvents; and, though some bodies, such as the calcareous, are -able to resist its force on the surface of the earth, yet, as has just -been shown, it is perfectly agreeable to analogy to suppose, that, -under great pressure, the carbonic state of the lime being preserved, -the purest limestone or marble might be softened, or even melted. -With respect to other substances, less doubt of their fusibility is -entertained; and though, in our experiments, the refractory nature of -siliceous earth has not been completely subdued, a degree of softness -and an incipient fusion have nevertheless been induced. - -Thus it appears, in general, that the same difficulties do not press -against the two theories of aqueous and of igneous consolidation; and, -that the latter employs an agent incomparably more powerful than the -former, of more general activity, and, what is of infinite importance -in a philosophical theory, vastly more definite in the laws of its -operation. - -18. A more particular examination of the different kinds of fossils -will confirm this conclusion, and will show, that, wherever they bear -marks of having been fluid, these marks are such as characterize the -fluidity of fusion, and distinguish it from that which is produced -by solution in a menstruum. Dr Hutton has enumerated many of these -discovered in the course of that careful and accurate examination of -fossils, in which he probably never was excelled by any mineralogist. -It will be sufficient here to point out a few of the most remarkable -examples. - -19. Fossil wood, penetrated by siliceous matter, is a substance well -known to mineralogists; it is found in great abundance in various -situations, and frequently in the heart of great bodies of rock. On -examination, the siliceous matter is often observed to have penetrated -the wood very unequally, so that the vegetable structure remains in -some places entire; and in other places is lost in a homogeneous mass -of agate or jasper. Where this happens, it may be remarked, that the -line which separates these two parts is quite sharp and distinct, -altogether different from what must have taken place, had the flinty -matter been introduced into the body of the wood, by any fluid in which -it was dissolved, as it would then have pervaded the whole, if not -uniformly, yet with a regular gradation. In those specimens of fossil -wood that are partly penetrated by agate, and partly not penetrated -at all, the same sharpness of termination may be remarked, and is an -appearance highly characteristic of the fluidity produced by fusion. - -20. The round nodules of flint that are found in chalk, quite insulated -and separate from one another, afford an argument of the same kind; -since the flinty matter, if it had been carried into the chalk by any -solvent, must have been deposited with a certain degree of uniformity, -and would not now appear collected into separate masses, without any -trace of its existence in the intermediate parts. On the other hand, if -we conceive the melted flint to have been forcibly injected among the -chalk, and to have penetrated it, somewhat as mercury may, by pressure, -be made to penetrate through the pores of wood, it might, on cooling, -exhibit the same appearances that the chalk-beds of England do actually -present us with. - -The siliceous pudding-stone is an instance closely connected with the -two last; in it we find both the pebbles, and the cement which unites -them, consisting of flint equally hard and consolidated; and this -circumstance, for which it is impossible to account by infiltration, or -the insinuation of an aqueous solvent, is perfectly consistent with the -supposition, that a stream of melted flint has been forcibly injected -among a mass of loose gravel. - -21. The common grit, or sandstone, though it certainly gives no -indication of having possessed fluidity, is strongly expressive of the -effects of heat. It is so, especially in those instances where the -particles of quartzy sand, of which it is composed, are firmly and -closely united, without the help of any cementing substance whatsoever. -This appearance, which is very common, seems to be quite inconsistent -with every idea of consolidation, except an incipient fusion, which, -with the assistance of a suitable compression, has enabled the -particles of quartz to unite into stone. - -It has indeed been asserted, that the mere apposition of stony -particles, so as to permit their corpuscular attraction to take place, -was sufficient to form them into stone. To this Dr Hutton has very well -replied, that, admitting the possibility of a hard and firm body being -produced in this way of which, however, we have no proof, the close -and compact texture, the perfect consolidation of the stones we are -now speaking of, would still remain to be explained, and of this it is -evident that the mere apposition of particles, and the force of their -mutual attraction, can afford no solution. - -22. These proofs that the strata must have endured the action of -intense heat, though immediately deduced from those of the siliceous -genus only, extend in reality to all the strata, of every kind, with -which they are found alternated. It is impossible that heat, of the -intensity here supposed, can have acted on a particular stratum, and -not on those that are contiguous to it; and, as there are no strata of -any kind with which the quartzy and siliceous are not intermixed, so -there are none of which the igneous consolidation is not thus rendered -probable. We need rest nothing, however, on this argument, as the -fossils of every genus may be shown to speak distinctly for themselves. - -23. Those of the calcareous genus do so perhaps more sparingly than -the rest; yet even among them there are many facts, that, though taken -unconnected with all others, are sufficient to establish the action of -subterraneous fire. Such, for example, are the calcareous breccias, -composed of fragments of marble or limestone, and not only adapted to -each other's shape, but indented into one another, in a manner not -a little resembling the _sutures_ of the human _cranium_. From such -instances, it is impossible not to infer the softness of the calcareous -fragments when they were consolidated into one mass. Now, this softness -could be induced only by heat; for it must be acknowledged, that the -action of any other solvent is quite inadequate to the softening of -large fragments of stone, without dissolving them altogether. - -24. In many other instances it appears certain, that the stones -of the calcareous genus have been reduced by heat into a state of -fluidity much more perfect. Thus, the saline or finer kinds of marble, -and many others that have a structure highly crystallized, must -have been softened to a degree little short of fusion, before this -crystallization could take place. Even the petrifactions which abound -so much in limestones tend to establish the same fact; for they possess -a sparry structure, and must have acquired that structure in their -transition from a fluid to a solid state.[10] - -[Footnote 10: NOTE VIII.] - -25. In accounting, by the operation of heat, for these appearances -of fluidity, Dr Hutton has proceeded on the principle already laid -down, as conformable to analogy, that calcareous earth, under great -compression, may have its fixed air retained in it, notwithstanding the -action of intense heat, and may, by that means, be reduced into fusion, -or into a state approaching to it. In all this I do not think that he -has departed from the strictest rules of philosophical investigation. -The facts just stated prove, that limestone was once soft, its -fragments retaining at the same time their peculiar form, an effect to -which we know of none similar but those of fire; and, therefore, though -we could not conjecture how heat might be applied to limestone so as -to melt it, instead of reducing it to a calx, we should, nevertheless, -have been forced to suppose, that this had actually taken place in the -bowels of the earth; and was a fact which, though we were not able to -explain it, we were not entitled to deny. The principle just mentioned -relieves us therefore from a difficulty, that would have embarrassed, -but could not have overturned, this theory of the earth. - -26. From the arguments which the argillaceous strata afford for the -igneous consolidation of fossils, I shall select one on which Dr Hutton -used to lay considerable stress, and which some of the adversaries of -his system have endeavoured to refute. This argument is founded on the -structure of certain ironstones called _septaria_, often met with among -the argillaceous schistus, particularly in the vicinity of coal. These -stones are usually of a lenticular or spheroidal form, and are divided -in their interior into distinct _septa_, by veins of calcareous spar, -of which one set are circular and concentric, the other rectilineal; -diverging from the centre of the former, and diminishing in size as -they recede from it. Now, what is chiefly to be remarked is, that -these veins terminate before they reach the surface of the stone; so -that the matter with which they are filled cannot have been introduced -from without by infiltration, or in any other way whatsoever. The only -other supposition, therefore, that is left for explaining the singular -structure of this fossil, is, that the whole mass was originally -fluid, and that, in cooling, the calcareous part separated from the -rest, and afterwards crystallized. - -27. It has been urged against this theory of the septaria, that these -stones are sometimes found with the calcareous veins extending all -the way to the circumference, and of course communicating with the -outside. But it must be observed, that this fact does not affect the -argument drawn from specimens in which no such communication takes -place. It is at best only an ambiguous instance, that may be explained -by two opposite theories, and may be reconciled either to the notion -of igneous or of aqueous consolidation: but if there is a single close -septarium in nature, it can, of course, be explained only by one of -these theories, and the other must, of necessity, be rejected. Besides, -it is plain, that a close septarium can never have been open, though an -open septarium may very well have been close; and indeed, as this stone -is, in certain circumstances, subject to perpetual exfoliation, it -would be wonderful if no one was ever found with the calcareous veins -reaching to the surface. With regard to the light, therefore, that they -give into their own history, these two kinds of septaria are by no -means on an equal footing; and this may serve to show, how necessary -it is, in all inductive reasoning, and particularly in a subject so -complex as geology, to separate with care such phenomena as admit of -two solutions, from such as admit only of one. - -28. The bituminous strata come next to be considered; and they are of -great consequence in the present argument, because their dissimilarity -in so many particulars to all other mineral substances, renders them -what Lord Bacon calls an _instantia singularis_, having the first -rank among facts subservient to inductive investigation. But though -unlike in substance to other fossils, and composed, as has been shown, -of materials that belonged not originally to the mineral kingdom, -they agree in many material circumstances with the strata already -enumerated. Their beds are disposed in the same manner, and are -alternated indiscriminately with those of all the secondary rocks, -and, being formed in the same region, must have been subject to the -same accidents, and have endured the operation of the same causes. -They are traversed too like the other strata, by veins of the metals, -of spars, of basaltes, and of other substances; and, whatever argument -may hereafter be derived from this to prove the action of fire on the -strata so traversed, is as much applicable to coal as to any other -mineral. The coal strata also contain pyrites in great abundance, a -substance that is perhaps, more than any other, the decided progeny of -fire. This compound of metal and sulphur, which is found in mineral -bodies of every kind, I believe, without any exception, is destroyed -by the contact of moisture, and resolved into a vitriolic salt. At -the same time it is found in the strata, not traversing them in -veins, which may be supposed of more recent formation than the strata -themselves; but existing in the heart of the most solid rocks, often -nicely crystallized, and completely inclosed, on all sides, without the -most minute vacuity. The pyrites must have been present, therefore, -when the strata were consolidated, and it is inconceivable, if their -consolidation was brought about in the wet way, that a substance -should be so generally found in them, the very existence of which is -incompatible with humidity. This argument for the igneous origin of the -strata is applicable to them all, but especially to those of coal, as -abounding with pyrites more than any other. - -29. The difficulty that here naturally present itself, viz. how -vegetable matter, such as coal is supposed to have been, could be -exposed to the action of intense heat, without being deprived of its -inflammable part, is obviated by the principle formerly explained -concerning the effects of compression. The weight incumbent on -the strata of coal, when they were exposed to the intense heat of -the mineral regions, may have been such as to retain the oily and -bituminous, as well as sulphureous parts, though the whole was reduced -almost to fusion; and thus, on cooling, the sulphur uniting with iron -might crystallize, and assume the form of pyrites. - -30. The compression, however, has not in every instance preserved the -bituminous, in union with the carbonic part of coal; and hence a mark -of the operation of fire quite peculiar to this fossil, and found in -those infusible kinds of it which contain no bitumen, and burn without -flame. These resemble, some of them very precisely, and all them in a -great degree, the products obtained by the distillation of the common -bituminous coal that is, they consist of charcoal, united to an earthy -basis in different proportions. It is natural therefore to conclude, -that this substance was prepared in the mineral regions by the action -of heat, which, in some instances, has driven off the inflammable part -of the coal. That the heat should, in some cases, have done so, is not -inconsistent with the general effect attributed to compression. The -conditions necessary for retaining the more volatile parts, may not -have been present every where in the same degree, so that the latter, -though they could not escape, may have been forced from one part of a -stratum, or body of strata, to another. - -31. In confirmation of this it must be observed, that, as the fixed -part of coal is thus found in the bowels of the earth, separate from -the volatile or bituminous, so, in the neighbourhood of coal strata, -the latter is sometimes found without any mixture of the former. The -fountains of naphtha and petroleum are well known; and Dr Hutton -has described a stratum of limestone, lying in the centre of a coal -country, which is pervaded and tinged by bituminous matter, through -its whole mass, and has, at the same time, many close cavities in -the heart of it, lined with calcareous spar, and containing fossil -pitch, sometimes in large pieces, sometimes in hemispherical drops, -scattered over the surface of the cavities. This combination could -only be effected by a part of the inflammable matter of the beds of -coal underneath, being driven off by heat, and made to penetrate the -limestone, while it was yet soft and pervious to heated vapours.[11] - -[Footnote 11: NOTE IX.] - -32. Hitherto we have enumerated those fossils that are either not at -all, or very sparingly soluble in water. There are, however, saline -bodies among the mineral strata, such for instance as rock-salt, which -are readily dissolved in water; and it yet remains to examine by what -cause their consolidation has been effected. - -Here the theorists who consider water as the sole agent in the -mineralization of fossils, are indeed delivered from one difficulty, -but it is only that they may be harder pressed on by another. It -cannot now be said, that the menstruum which they employ is incapable -of dissolving the substances exposed to its action, as in the case of -metallic or stony bodies; but it may very well be asked, how the water -came to deposit the salts which it held in solution, and to deposit -them so copiously as it has done in many places, without any vestige -of similar deposition in the places immediately contiguous. If they -refuse to call to their assistance any other than their favourite -element, they will not find it easy to answer this question, and must -feel the embarrassment of a system, subject to two difficulties, so -nicely, but so unhappily adjusted, that one of them is always prepared -to act whenever the other is removed. If, on the other hand, they will -admit the operation of subterraneous heat, it appears possible, that -the local application of such heat may have driven the water, in -vapour, from one place to another, and by such action often repeated in -the same spot, may have produced those great accumulations of saline -matter, that are actually found in the bowels of the earth. - -33. But granting that, either in the way just pointed out, or in some -other that is unknown, the salt and the water have been separated, -some further action of heat seems requisite, before a compact, and -highly indurated body, like rock-salt, could be produced. The mere -precipitation of the salt, would, as Dr Hutton has observed, form only -an assemblage of loose crystals at the bottom of the sea, without -solidity or cohesion: and to convert such a mass into a firm and solid -rock, would require the application of such heat as was able to reduce -it into fusion. The consolidation of rock-salt, therefore, however its -separation from the water is accounted for, cannot be explained but on -the hypothesis of subterraneous heat. - -34. Some other phenomena that have been observed in salt mines, come -in support of the same conclusion. The salt rock of Cheshire, which -lies in thick beds, interposed between strata of an argillaceous or -marly stone, and is itself mixed with a considerable portion of the -same earth, exhibits a very great peculiarity in its structure. Though -it forms a mass extremely compact, the salt is found to be arranged -in round masses of five or six feet in diameter, not truly spherical, -but each compressed by those that surround it, so as to have the shape -of an irregular polyhedron. These are formed of concentric coats, -distinguishable from one another by their colour, that is, probably -by the greater or less quantity of earth which they contain, so that -the roof of the mine, as it exhibits a horizontal section of them, -is divided into polygonal figures, each with a multitude of polygons -within it, having altogether no inconsiderable resemblance to a -_mosaic_ pavement. In the triangular spaces without the polygons, the -salt is in coats parallel to the sides of the polygons. - -The circumstances which gave rise to this singular structure we should -in vain endeavour to define; yet some general conclusions concerning -them seem to be within our reach. It is clear that the whole mass of -salt was fluid at once, and that the forces, whatever they were, which -gave solidity to it, and produced the new arrangement of its particles, -were all in action at the same time. The uniformity of the coated -structure is a proof of this, and, above all, the compression of the -polyhedra, which is always mutual, the flat side of one being turned to -the flat side of another, and never an angle to an angle, nor an angle -to a side. The coats formed as it were round so many different centres -of attraction, is also an appearance quite inconsistent with the notion -of deposition; both these, however, are compatible with the notion of -solidity acquired by the refrigeration of a fluid, where the whole -mass is acted on at the same time, and where no solvent remains to be -disposed of after the induration of the rest. - -35. Another species of fossil salt exhibits appearances equally -favourable to the theory of igneous consolidation. This is the Trona of -Africa, which is no other than soda, or mineral alkali, in a particular -state. The specimen of this fossil in Dr Black's, now Dr Hope's, -collection, is of a sparry and radiated structure, and is evidently -part of the contents of a vein, having a stony crust adhering to it, -on one side, with its own sparry structure complete, on the opposite. -It contains but about one sixth of the water of crystallization -essential to this salt when obtained in the humid way; and, what is -particularly to be remarked, it does not lose this water, nor become -covered with a powder, like the common alkali, by simple exposure to -the air. It is evident, therefore, that this fossil does not originate -from mere precipitation; and when we add, that in its sparry structure -it contains evident marks of having once been fluid, we have little -reason to entertain much doubt concerning the principle of its -consolidation. - -Thus, then, the testimony given to the operation of fire, or heat, -as the consolidating power of the mineral kingdom, is not confined -to a few fossils, but is general over all the strata. How far the -unstratified fossils agree in supporting the same conclusion, will be -afterwards examined. - - - 3. _Position of the Strata._[12] - -[Footnote 12: Theory of the Earth, vol. i. p. 120.] - -36. We have seen of what materials the strata are composed, and by -what power they have been consolidated; we are next to inquire, from -what cause it proceeds, that they are now so far removed from the -region which they originally occupied, and wherefore, from being all -covered by the ocean, they are at present raised in many places fifteen -thousand feet above its surface. Whether this great change of relative -place can be best accounted for by the depression of the sea, or the -elevation of the strata themselves, remains to be considered. - -Of these two suppositions, the former, at first sight, seems -undoubtedly the most probable, and we feel less reluctance to suppose, -that a fluid, so unstable as the ocean, has undergone the great -revolution here referred to, than that the solid foundations of the -land have moved a single fathom from their place. This, however, is a -mere illusion. Such a depression of the level of the sea as is here -supposed, could not happen without a change proportionally great in the -solid part of the globe; and, though admitted as true, will be found -very inadequate to explain the present condition of the strata. - -37. Supposing the appearances which clearly indicate submersion under -water to reach no higher than ten thousand feet above the present level -of the sea, and of course the surface of the sea to have been formerly -higher by that quantity than it is now; it necessarily follows, that -a bulk of water has disappeared, equal to more than a seven hundredth -part of the whole magnitude of the globe.[13] The existence of empty -caverns of extent sufficient to contain this vast body of water, and of -such a convulsion as to lay them open, and give room to the retreat of -the sea, are suppositions which a philosopher could only be justified -in admitting, if they promised to furnish a very complete explanation -of appearances. But this justification is entirely wanting in the -present case; for the retreat of the ocean to a lower level, furnishes -a very partial and imperfect explanation of the phenomena of geology. -It will not explain the numberless remains of ancient continents that -are involved, as we have seen, in the present, unless it be supposed -that the ancient ocean, though it rose to so great a height, had -nevertheless its shores, and was the boundary of land still higher than -itself. And, as to that which is now more immediately the object of -inquiry, the position of the strata, though the above hypothesis would -account in some sort for the change of their place, relatively to the -level of the sea; yet, if it shall be proved, that the strata have -changed their place relatively to each other, and relatively to the -plane of the horizon, so as to have had an angular motion impressed on -them, it is evident that, for these facts, the retreat of the sea does -not afford even the shadow of a theory. - -[Footnote 13: NOTE X.] - -38. Now, it is certain, that many of the strata have been moved -angularly, because that, in their original position, they must have -been all nearly horizontal. Loose materials, such as sand and gravel -subsiding at the bottom of the sea, and having their interstices filled -with water, possess a kind of fluidity: they are disposed to yield -on the side opposite to that where the pressure is greatest, and are -therefore, in some degree, subject to the laws of hydrostatics. On -this account they will arrange themselves in horizontal layers; and -the vibrations of the incumbent fluid, by impressing slight motion -backward, and forward, on the materials of these layers, will very much -assist the accuracy of their level. - -It is not, however, meant to deny, that the form of the bottom might -influence, in a certain degree, the stratification of the substances -deposited on it. The figure of the lower beds deposited on an uneven -surface, would necessarily be affected by two causes; the inclination -of that surface, on the one hand, and the tendency to horizontality, -on the other; but, as the former cause would grow less powerful as the -distance from the bottom increased, the latter cause would finally -prevail, so that the upper beds would approach to horizontally, and the -lower would neither be exactly parallel to them, nor to one another. -Whenever, therefore, we meet with rocks, disposed in layers quite -parallel to one another, we may rest assured, that the inequalities of -the bottom have had no effect, and that no cause has interrupted the -statical tendency above explained. - -Now, rocks having their layers exactly parallel, are very common, and -prove their original horizontally to have been more precise than we -could venture to conclude from analogy alone. In beds of sandstone, -for instance, nothing is more frequent than to see the thin layers of -sand, separated from one another by layers still finer of coaly, or -micaceous matter, that are almost exactly parallel, and continue so to -a great extent without any sensible deviation. These planes can have -acquired their parallelism only in consequence of the property of water -just stated, by which it renders the surfaces of the layers, which it -deposits, parallel to its own surface, and therefore parallel to one -another. Though such strata, therefore, may not now be horizontal, they -must have been so originally; otherwise it is impossible to discover -any cause for their parallelism, or any rule by which it can have been -produced. - -39. This argument for the original horizontality of the strata, -is applicable to those that are now farthest removed from that -position. Among such, for instance, as are highly inclined, or even -quite vertical, and among those that are bent and incurvated in the -most fantastical manner, as happens more especially in the primary -schisti, we observe, through all their sinuosities and inflections, -an equality of thickness and of distance among their component -laminæ. This equality could only be produced by those laminæ having -been originally spread out on a flat and level surface, from which -situation, therefore, they must afterwards have been lifted up by the -action of some powerful cause, and must have suffered this disturbance -while they were yet in a certain degree flexible and ductile. Though -the primary direction of the force which thus elevated them must have -been from below upwards, yet it has been so combined with the gravity -and resistance of the mass to which it was applied, as to create a -lateral and oblique thrust, and to produce those contortions of the -strata, which, when on the great scale, are among the most striking and -instructive phenomena of geology. - -40. Great additional force is given to this argument, in many cases, by -the nature of the materials of which the stratified rocks are composed. -The beds of breccia and pudding-stone, for instance, are often in -planes almost vertical, and, at the same time, contain gravel-stones, -and other fragments of rock, of such a size and weight, that they -could not remain in their present position an instant, if the cement -which unites them were to become soft; and therefore they certainly -had not that position at the time when this cement was actually soft. -This remark has been made by mineralogists who were not led to it by -any system. The judicious and indefatigable observer of the Alps, -describing the pudding-stone of Valorsine, near the sources of the -Arve, tells us, that he was astonished to find it in beds almost -vertical, a situation in which it could not possibly have been formed. -"That particles," he adds, "of extreme tenuity, suspended in a fluid, -might become agglutinated, and form vertical beds, is a thing that -may be conceived; but that pieces of stone, of several pounds weight, -should have rested on the side of a perpendicular wall, till they were -enveloped in a stony cement, and united into one mass, is a supposition -impossible and absurd. It should be considered, therefore, as a thing -demonstrated, that this pudding-stone was formed in a horizontal -position, or one nearly such, and elevated after its induration. We -know not," he continues, "the force by which this elevation has been -effected; but it is an important step among the prodigious number of -vertical beds that are to be met with in the Alps, to have found some -that must certainly have been formed in a horizontal situation."[14] - -[Footnote 14: Voyages aux Alpes, tom. ii § 690.] - -41. Nothing can be more sound and conclusive than this reasoning; and -had the ingenious author pursued it more systematically, it must have -led him to a theory of mountains very little different from that which -we are now endeavouring to explain. If some of the vertical strata are -proved to have been formed horizontally, there can be no reason for -not extending the same conclusion to them all, even if we had not the -support of the argument from the parallelism of the layers, which has -been already stated. - -42. The highly inclined position, and the manifold inflections of the -strata, are not the only proofs of the disturbance that they have -suffered, and of the violence with which they have been forced up from -their original place. Those interruptions of their continuity which -are observed, both at the surface and under it, are evidences of the -same fact. It is plain, that if they remained now in the situation -in which they were at first deposited, they would never appear to -be suddenly broken off. No stratum would terminate abruptly; but, -however its nature and properties might change, it would constitute -an entire and continued rock, at least where the effects of waste and -_detritus_ had not produced a separation. This, however, is very far -from being the actual condition of stratified bodies. Those that are -much inclined, or that make considerable angles with the horizontal -plane, must terminate abruptly where they come up to the surface. Their -doing so is a necessary consequence of their position, and furnishes no -argument, it may be said, for their having been disturbed, different -from that which has been already deduced from their inclination. There -are, however, instances of a breach of continuity in the strata, under -the surface, that afford a proof of the violence with which they have -been displaced, different from any hitherto mentioned. Of this nature -are the _slips_ or _shifts_, that so often perplex the miner in his -subterraneous journey, and which change at once all those lines and -bearings that had hitherto directed his course. When his mine reaches -a certain plane, which is sometimes perpendicular, sometimes oblique -to the horizon, he finds the beds of rock broken asunder, those on -the one side of the plane having changed their place, by sliding in -a particular direction along the face of the others. In this motion -they have sometimes preserved their parallelism, that is, the strata -on one side of the _slip_ continue parallel to those on the other; in -other cases, the strata on each side become inclined to one another, -though their identity is still to be recognized by their possessing -the same thickness, and the same internal characters. These _shifts_ -are often of great extent, and must be measured by the quantity of -the rock moved, taken in conjunction with the distance to which it -has been carried. In some instances, a vein is formed at the plane of -the shift or slip, filled with materials of the kinds which will be -hereafter mentioned; in other instances, the opposite sides of the rock -remain contiguous, or have the interval between them filled with soft -and unconsolidated earth. All these are the undeniable effects of some -great convulsion, which has shaken the very foundations of the earth; -but which, far from being a disorder in nature, is part of a regular -system, essential to the constitution and economy of the globe. - -The production of the appearances now described, belongs, without -doubt, to different periods of time; and, where slips intersect one -another, we can often distinguish the less from the more ancient They -are all, however, of a date posterior to that at which the waving and -undulated forms of the strata were acquired, as they do not carry with -them any marks of the softness of the rock, but many of its complete -induration. - -The same phenomenon which is thus exemplified on a great scale in -the bowels of the earth, is often most beautifully exhibited in -single specimens of stone, and is accompanied with this remarkable -circumstance, that the _integrity_ of the stone is not destroyed by the -shifts, whatever wounds had been made in it being healed, and the parts -firmly reunited to one another.[15] - -[Footnote 15: NOTE XI.] - -43. Though such marks of violence as have been now enumerated are -common in some degree to all the strata, they abound most among the -primary, and point out these as the part of our globe which has been -exposed to the greatest vicissitudes. At their junction with the -secondary, or where they emerge, as it were, from under the latter, -phenomena occur, which mark some of those vicissitudes with astonishing -precision; phenomena of which the nature was first accurately explored, -and the consequences fully deduced, by the geologist whose system I am -endeavouring to explain. He observed, in several instances, that where -the primary schistus rises in beds almost vertical, it is covered by -horizontal layers of secondary sandstone, which last are penetrated by -the irregular tops of the schistus, and also involve fragments of that -rock, some angular, others round and smooth, as if worn by attrition. -From this he concluded, that the primary strata, after being formed at -the bottom of the sea, in planes nearly horizontal, were raised, so as -to become almost vertical, while they were yet covered by the ocean, -and before the secondary strata had begun to be deposited on them. He -also argued, that, as the fragments of the primary rock, included in -the secondary, are many of them rounded and worn, the deposition of -the latter must have been separated from the elevation of the former -by such an interval of time, as gave room for the action of waste and -decay, allowing those fragments first to be detached, and afterwards -wrought into a round figure.[16] - -[Footnote 16: NOTE XII.] - -44. Indeed, the interposition of a breccia between the primary and -secondary strata, in which the fragments, whether round or angular, -are always of the primary rock, is a fact so general, and the quantity -of this breccia is often so great, that it leads to a conclusion more -paradoxical than any of the preceding, but from which, nevertheless, -it seems very difficult to withhold assent. Round gravel, when in -great abundance, agreeably to a remark already made, must necessarily -be considered as a production peculiar to the beds of rivers, or -the shores of continents, and as hardly ever formed at great depths -under the surface of the sea. It should seem, then, that the primary -schistus, after attaining its erect position, had been raised up to -the surface, where this gravel was formed; and from thence had been -let down again to the depths of the ocean, where the secondary strata -were deposited on it. Such alternate elevations and depressions of the -bottom of the sea, however extraordinary they may seem, will appear to -make a part of the system of the mineral kingdom, from other phenomena -hereafter to be described. - -45. On the whole, therefore, by comparing the actual position of the -strata, their erectness, their curvature, the interruptions of their -continuity, and the transverse stratification of the secondary in -respect of the primary, with the regular and level situation which -the same strata must have originally possessed, we have a complete -demonstration of their having been disturbed, torn asunder, and moved -angularly, by a force that has, in general, been directed from below -upwards. In establishing this conclusion, we have reasoned more from -the facts which relate to the _angular elevation_ of the strata, -than from those which relate to their _absolute elevation_, or their -translation to a greater distance from the centre of the earth. This -has been done, because the appearances, which respect the absolute -lifting up of the strata are more ambiguous than those, which respect -the change of their angular position. The former might be accounted -for, could they be separated from the latter, in two ways, viz. either -by the retreat of the sea, or the raising up of the land; but the -latter can be explained only in one way, and force us of necessity to -acknowledge the existence of an expanding power, which has acted on the -strata with incredible energy, and has been directed from the centre -toward the circumference. - -46. When we are assured of the existence of such a power as this in the -mineral regions, we should argue with singular inconsistency, if we did -not ascribe to it all the other appearances of motion in those regions, -which it is adequate to produce. If nature in her subterraneous abodes -is provided with a force that could burst asunder the massy pavement -of the globe, and place the fragments upright upon their edges, could -she not, by the same effort, raise them from the greatest depths of the -sea, to the highest elevation of the land? The cause that is adequate -to one of these effects is adequate to them both together; for it is a -principle well known in mechanical philosophy, that the force which -produces a parallel motion, may, according to the way in which it is -applied, produce also an angular motion, without any diminution of the -former effect. It would, therefore, be extremely unphilosophical to -suppose, that any other cause has changed the relative level of the -strata, and the surface of the sea, than that which has, in so many -cases, raised the strata from a horizontal to a highly inclined, or -even vertical situation: it would be to introduce the action of more -causes than the phenomena require, and to forget, that nature, whose -operations we are endeavouring to trace, combines the possession of -infinite resources with the most economical application of them. - -47. From all, therefore, that relates to the position of the strata, I -think I am justified in affirming, that their disturbance and removal -from the place of their original formation, by a force directed -from below upwards, is a fact in the natural history of the earth, -as perfectly ascertained as any thing which is not the subject of -immediate observation. As to the power by which this great effect has -been produced, we cannot expect to decide with equal evidence, but must -be contented to pass from what is certain to what is probable. We may, -then, remark, that of the forces in nature to which our experience -does in any degree extend, none seems so capable of the effect we -would ascribe to it, as the expansive power of heat; a power to which -no limits can be set, and one, which, on grounds quite independent of -the elevation of the strata, has been already concluded to act with -great energy in the subterraneous regions. We have, indeed, no other -alternative, but either to adopt this explanation, or to ascribe the -facts in question to some secret and unknown cause, though we are -ignorant of its nature, and have no evidence of its existence. - -We are therefore to suppose, that the power of the same subterraneous -heat, which consolidated and mineralized the strata at the bottom of -the sea, has since raised them up to the height at which they are now -placed, and has given them the various inclinations to the horizon -which they are found actually to possess. - -48. The probability of this hypothesis will appear greatly increased, -when it is considered, that, besides those now enumerated, there are -other indications of movement among the bodies of the mineral kingdom, -where effects of heat more characteristic than simple expansion are -clearly to be discovered. Thus, on examining the marks of disorder -and movement which are found among the strata, it cannot fail to be -observed, that notwithstanding the fracture and dislocation, of which -they afford so many examples, there are few empty spaces to be met -with among them, as far as our observation extends. The breaches and -separations are numerous, and distinct; but they are, for the most -part, completely filled up with minerals of a kind quite different -from the rock on each side of them, and remarkable for containing -no vestiges of stratification. We are thus led to consider the -unstratified minerals, the second of the divisions into which the whole -mineral kingdom, viewed geologically, ought to be distinguished. These -minerals are immediately connected with the disturbance of the strata, -and appear, in many instances, to have been the instruments of their -elevation. - - - - - SECTION II. - - OF THE PHENOMENA PECULIAR TO UNSTRATIFIED BODIES. - - - 1. _Metallic Veins._ - -49. THE unstratified minerals exist either in veins, intersecting the -stratified, or in masses surrounded by them. Veins are of various -kinds, and may in general be defined, separations in the continuity of -a rock, of a determinate width, but extending indefinitely in length -and depth, and filled with mineral substances, different from the rock -itself. The mineral veins, strictly so called, are those filled with -crystallized substances, and containing the metallic ores. - -That these veins are of a formation subsequent to the hardening and -consolidation of the strata which they traverse, is too obvious to -require any proof; and it is no less clear, from the crystallized -and sparry structure of the substances contained in them, that these -substances must have concreted from a fluid state. Now, that this -fluidity was simple, like that of fusion by heat, and not compound, -like that of solution in a menstruum, is inferred from many phenomena. -It is inferred from the acknowledged insolubility of the substances -that fill the veins, in any one menstruum whatsoever; from the total -disappearance of the solvent, if there was any; from the complete -filling up of the vein by the substances which that solvent had -deposited; from the entire absence of all the appearances of horizontal -or gradual deposition; and, lastly, from the existence of close -cavities, lined with crystals, and admitting no egress to any thing but -heat. - -50. To the same effect may be mentioned those groups of crystals -composed of substances the most different, that are united in the same -specimen, all intersecting and mutually impressing one another. These -admit of being explained, on the supposition that they were originally -in fusion, and became solid by the loss of heat; a cause that acted -on them all alike, and alike impelled them to crystallize: But the -appearances of simultaneous crystallization seem incompatible with the -nature of deposition from a solvent, where, with respect 16 different -substances, the effects must take place slowly, and in succession. - -51. The metals contained in the veins which we are now treating of, -appear very commonly in the form of an ore, mineralized by sulphur. -Their union with this latter substance can be produced, as we know, by -heat, but hardly by the way of solution in a menstruum, and certainly -not at all, if that menstruum is nothing else than water. The metals, -therefore, when mineralized by sulphur, give no countenance to the -hypothesis of aqueous solution; and still less do they give any when -they are found native, as it is called, that is, malleable, pure -and uncombined with any other substance. The great masses of native -iron found in Siberia and South America are well known; and nothing -certainly can less resemble the products of a chemical precipitation. -Gold, however, the most perfect of the metals, is found native most -frequently; the others more rarely, in proportion nearly to the -facility of their combination with sulphur. Of all such specimens it -may be safely affirmed, that if they have ever been fluid, or even -soft, they must have been so by the action of heat; for, to suppose -that a metal has been precipitated, pure and uncombined from any -menstruum, is to trespass against all analogy, and to maintain a -physical impossibility. But it is certain, that many of the native -metals have once been in a state of softness, because they bear on them -impressions which they could not have received but when they were soft. -Thus, gold is often impressed by quartz and other stones, which still -adhere to it, or are involved in it. Specimens of quartz, containing -gold and silver shooting through them, with the most beautiful and -varied ramifications, are every where to be met with in the cabinets of -the curious; and contain, in their structure, the clearest proof, that -the metal and the quartz have been both soft, and have crystallized -together. By the compactness, also, of the body which they form, they -show, that when they acquired solidity, it was by the concretion of the -whole mass, and not by such partial concretion as takes place when a -solvent is separated from substances which it held in solution. - -52. Native copper is very abundant; and some specimens of it have been -found crystallized. Here the crystallization of the metal is a proof -that it has passed from a fluid to a solid state; and its purity is a -proof that it did not make that transition by being precipitated from a -menstruum. - -53. Again, pieces of native manganese have been found possessing so -exactly the characters peculiar to that metal when reduced in our -furnaces, that it is impossible to consider them as deriving their -figure and solidity from any cause but fusion. The ingenious author -who describes these specimens, La Peyrouse, was so forcibly struck -with this resemblance, that he immediately drew the same conclusion -from it which is drawn here, attributing the only difference, which -he remarked between the native and the artificial _regulus_, to the -different energy with which the same agent works when employed by -nature and by art.[17] - -[Footnote 17: Theory of the Earth, vol. i. p. 68. Journal de Phys. -Janvier, 1786.] - -54. All these appearances conspire to prove, that the materials which -fill the mineral veins were melted by heat, and forcibly injected, in -that state, into the clefts and fissures of the strata. These fissures -we must conceive to have arisen, not merely from the shrinking of the -strata while they acquired hardness and solidity, but from the violence -done to them, when they were heaved up and elevated in the manner which -has already been explained.[18] - -[Footnote 18: NOTE XIII.] - -55. When these suppositions are once admitted, the other leading facts -in the history of metallic veins will be readily accounted for. Thus, -for instance, it is evident to what we must ascribe the fragments of -the surrounding rock that are often found immersed in the veins, and -encompassed on all sides by crystallized substances. These fragments -being no doubt detached by the concussion, which at once tore asunder -and elevated the strata, were sustained by the melted matter that -flowed at the same time upward through the vein. Large masses of rock -are often found in this manner completely insulated; one of these, -which M. De Luc has described with great accuracy, is no less than a -vast segment of a mountain.[19] - -[Footnote 19: Lettres Physiques, &c. tom. iii. P. 361.] - -56. The immense violence which has accompanied the formation of mineral -veins, is particularly marked by the slips and shifts of the strata on -each side of them all tending to show what mighty changes have taken -place in those regions, which our imagination erroneously paints as -the abode of everlasting silence and rest. This shifting of the strata -is best observed, where the veins make a transverse section of beds of -rock, considerably inclined to the horizon. There it is common to see -the beds on one side of the vein slipped along from the corresponding -beds on the other side, and removed sometimes in a horizontal, -sometimes in an oblique direction. In this way, not only the strata -are shifted, but veins, which intersect one another, are also shifted -themselves. They are _heaved_, as it is called in the significant -language of the miners, and forced out of their direction. It is -impossible, in such a case, but to connect in the mind the formation -of the vein, and the production of the slips which accompany it, and to -regard them as parts of the same phenomenon. - -57. Where these slips are horizontal, and exhibit great bodies of -strata carried from their place, while the parts of the transferred -mass remain undisturbed relatively to one another, they furnish a dear -proof, that this change of plaice has not arisen from the falling in -of the roofs of caverns, as some geologists suppose. The horizontal -direction, and the regularity of the movement, are incompatible with -the action of such a cause as this; and indeed it is highly interesting -to remark, in the midst of the signs of disturbance which prevail in -the bowels of the earth, that there reigns a certain symmetry and -order, which indicate the action of a force of incredible magnitude, -but slow and gradual in its effects. The parts of the mass moved are -undisturbed relatively to one another; what has been broken has been -cemented; the breaches of continuity have been filled up and healed; -and every where we see the operation of a cause that could unite as -well as separate. The twofold action of heat to expand and to melt, -could scarce be pointed out more clearly by any system of appearances. - -58. As a long period was no doubt required for the elevation of the -strata, the rents made in them are not all of the same date, nor the -veins all of the same formation. This is clear in the case of one vein -producing a shift or slip in another; for the vein which forces the -other out of its place, and preserves its own direction, is evidently -the more recent of the two, and must have had its materials in a -state of activity, when those of the other were inert. Sometimes, -also, at the intersection of two veins, we may trace the current of -the materials of the one, across those of the other; and here, of -consequence, the relative antiquity is determined just as in the former -instance. - -59. The want of any appearance of stratification in mineral veins has -already been taken notice of. There is, however, to be observed, in -many instances, a tendency to a regular arrangement of the substances -contained in them; those of the same kind forming coats parallel to the -sides of the vein, and nearly of an equal thickness. This phenomenon -is considered as one of the strongest arguments in favour of the -Neptunian system, but has nothing in it, in the least incompatible -with that theory which ascribes the formation of veins to the action -of subterraneous heat. When melted matter from the mineral regions was -thrown up into the veins, that which was nearest to the sides would -soonest lose its heat. The similar substances, also, would unite while -this process was going forward, and would crystallize, as in other -cases of congelation, from the sides toward the interior. There is the -more reason for supposing this to have been the case, that the same -sort of coating is often observed on the inside of close cavities, -which are, nevertheless, so constructed, as to afford a demonstration -that no chemical solvent was ever included in them, (§ 74.) Some -veins, it must also be considered, may have been filled by successive -injections of melted matter, and this would naturally give rise to a -variety of separate incrustations.[20] - -[Footnote 20: See some farther remarks on this subject at NOTE XIII.] - -60. In the view now given of metallic veins, they have been considered -as traversing only the stratified parts of the globe. They do, -however, occasionally intersect the unstratified parts, particularly -the granite, the same vein often continuing its course across rocks -of both kinds, without suffering any material change; and, if we have -hitherto paid no attention to this circumstance, it is because the -order pursued in this essay required, that the relation of the veins -to stratified bodies should be first treated of. Besides, the facts -in the natural history of veins, whether contained in stratified or -unstratified rocks, are so nearly alike, that in a general view of -geology, they do not require to be distinguished. It is material to -remark, that, though metallic veins are found indiscriminately in all -the different kinds of rock, whether stratified or otherwise, they are -most abundant in the class of primary schisti. All the countries most -remarkable for their mines, and the mountains distinguished by the -name of metalliferous, are primary, and the instance of Derbyshire is -perhaps the most considerable exception to this rule that is known. -This preference, which the metals appear to give to the primary strata, -is very consistent with Dr Hutton's theory, which represents the rocks -of that order as being most changed from their original position, and -those on which the disturbing forces of the subterraneous regions have -acted most frequently, and with greatest energy. The primary strata are -the lowest, also, and have the most direct communication with those -regions from which the mineral veins derive all their riches. - - - 2. _Of Whinstone._ - -61. Beside the veins filled with spar, and containing the metallic -ores, the strata are intersected by veins of whinstone, porphyry, and -granite, the characters of which are next to be examined. - -The term _whin_, or _whinstone_, with Dr. Hutton, like the word _trap_, -with the German mineralogists, denotes a class of stones, comprehending -several distinct species, or at least varieties. The common _basalt_, -the _wacken_, _mullen_, and _crag_ of Kirwan, the _grûnstein_ of -Werner, and the _amygdaloid_, are comprehended under the name of whin. -All these stones have a tendency to a spathose structure, and discover -at least the rudiments of crystallization. They are, at the same time, -without any mark of stratification in their internal texture, as they -are also, for the most part, in their outward configuration; and, as -the different species here enumerated compose, not unfrequently, parts -of the same continuous rock, the change from one to another being made -through a series of insensible gradations, they may safely be regarded -by the geologist as belonging to the same _genus_. - -62. Whin, though not stratified, exists in two different ways, that is, -either in veins, (called in Scotland _dykes_,) traversing the strata -like the veins already described, or in irregular masses, incumbent -on the strata, and sometimes interposed between them. In both these -forms, whinstone has nearly the same characters, and bears, in all its -varieties, a most striking resemblance to the lavas which have actually -flowed from volcanoes on the surface of the earth. This resemblance -is so great, that the two substances have been often mistaken for one -another; and many rocks, which have been pronounced to be the remains -of extinguished volcanoes, by mineralogists of no inconsiderable -name, have been found, on closer examination, to be nothing else than -masses or veins of whinstone. This latter stone is indeed only to be -distinguished from the former, by a careful examination of the internal -characters of both; and chiefly from this circumstance, that whinstone -often contains calcareous spar and zeolite, whereas neither of these -substances is found in such lavas, as are certainly known to have been -thrown out by volcanic explosions. - -Now, from these circumstances of affinity between lava and whinstone, -on the one hand, and of diversity on the other, as the formation of -the one is known, it should seem that some probable conclusion may be -drawn concerning the formation of the other. The affinity in question -is constant and essential; the difference variable and accidental; -and this naturally leads to suspect, that the two stones have the -same origin; and that, as lava is certainly a production of fire, so -probably is whinstone. - -63. But, in order to see whether this hypothesis will explain the -diversity of the two substances, without which it will not be entitled -to much attention, we must remark, that the presence of carbonate of -lime in a body that has been fused, argues, agreeably to the principles -formerly explained, that the fusion was brought about under a great -compressing force, that is to say, deep in the bowels of the earth, or -in the great laboratory of the mineral regions. We are, therefore, to -suppose that the fusion of the whin was performed in those regions, -where the compression was sufficient to preserve the carbonic gas in -union with the calcareous earth, so that these two substances melted -together, and, on cooling, crystallized into spar. In the lavas, again, -thrown out by volcanic eruption, the fusion, as we know, wherever it -may begin, continues in the open air, where the pressure is only that -of the atmosphere: the calcareous earth, which, therefore, may have -been, in the form of a carbonate, among the materials of this lava, -must be converted into quicklime, and become infusible; hence the want -of calcareous spar in lavas that have flowed at the surface. - -Thus, whinstone is to be accounted a subterraneous, or _unerupted_ -lava; and our theory has the advantage of explaining both the affinity -and the difference between these stony bodies, without the introduction -of any new hypothesis. In the Neptunian system, the affinity of -whinstone and lava is a paradox which admits of no solution. - -64. The columnar structure sometimes found in that species of whinstone -called basaltes, is a fact which has given rise to much discussion; -and it must be confessed, that though one of the most striking and -peculiar characters of this fossil, it is not that which gives the -clearest and most direct information concerning its origin. One -circumstance, however, very much in favour of the opinion that basaltic -rocks owe their formation to fire, is, that the columnar form is -sometimes assumed by the lava actually erupted from volcanoes. Now, it -is certainly of no small importance, to have the synthetic argument -on our side, and to know, that basaltic columns can be produced by -fire; though, no doubt, to give absolute certainty to our conclusion, -it would be necessary to show, that there are in nature no other -means but this by which these columns can be formed. This sort of -evidence is hardly to be looked for; but since the power of fusion, -to produce the phenomena in question, is perfectly established, and -since the production of the same phenomena in the humid way is a mere -hypothesis, if there be the least reason to suspect the action of -subterraneous heat as one of the causes of mineralization, every maxim -of sound philosophy requires that the basaltic structure, in all cases, -should be ascribed to it. - -65. The Neptunists will no doubt allege, with BERGMAN, that, in the -drying of starch, clay, and a few other substances, something analogous -to basaltic columns is produced. Here, however, a most important -difference is to be remarked, corresponding very exactly to one of the -characters which we have all along observed to distinguish the products -of aqueous, from those of igneous consolidation. The columns formed -by the substances just mentioned, are distant from one another: they -are separated by fissures which widen from the bottom to the top, and -which arise from the shrinking and drying of the mass. In the basaltic -columns, no such openings, nor vacuity of any kind is found; the -pillars are in contact, and, though perfectly distinct, are so close, -that the sharp edge of a wedge can hardly be introduced between them. -This is a great peculiarity in the basaltic structure, and is strongly -expressive of this fact, that the mass was all fluid together, and -that its parts took their new arrangement, not in consequence of the -separation of a fluid from a solid part, by which great shrinking and -much empty space might be produced; but in consequence of a cause -which, like refrigeration, acted equally on all the parts of the mass, -and preserved their absolute contact after their fluidity had ceased. - -66. A mark of fusion, or at least of the operation of heat, which -whinstone possesses in common with many other minerals, is its being -penetrated by pyrites, a substance, as has been already remarked, that -is of all others most exclusively the production of fire. Another -mark of fusion, more distinctive of whin, is, that both in veins and -in masses it sometimes includes pieces of sandstone, or of the other -contiguous strata, completely insulated, and having the appearance -of fragments of rock, floating in a fluid sufficiently dense and -ponderous to sustain their weight. Though these fragments have been -too refractory to be reduced into fusion themselves, they have not -remained entirely unchanged, but are, in general, extremely indurated, -in comparison of the rock from which they appear to have been detached. - -67. Similar instances of extraordinary induration are observed in the -parts of the strata in contact with whinstone, whether they form the -sides of the veins, or the floors, and roofs of the masses into which -the whinstone is distributed. The strata whether sandy or argillaceous, -in such situations, are usually extremely hard and consolidated; the -former in particular lose their granulated texture, and are sometimes -converted into perfect jasper. This interesting remark was first made -by Dr Hutton, and the truth of it has been verified by a great number -of subsequent observations. - -68. To the same excellent geologist we are indebted for the knowledge -of an analogous fact, attendant on the passage of whinstone veins -through coal strata. As the beds of stone where they are in contact -with veins of whin, seem to acquire additional induration, so those -of coal, in like circumstances, are frequently found to have lost -their fusibility, and to be reduced nearly to the condition of coke, -or of charcoal. The existence of coal of this kind has been already -mentioned, and considered as a proof of the operation of subterraneous -heat. In the instances here referred to, that is, where the charring -of the coal is limited to those parts of the strata which are in -contact with the whin, or in its immediate vicinity, the heat is -pointed out as residing in the vein; and this is to be accounted for -only on the supposition of the melted whin, at a period subsequent to -the consolidation of the coal, having flowed through the openings of -the strata. The heat has been powerful enough, in many cases, to drive -off the bituminous matter of the coal, and to force it into colder and -more distant parts. Few facts, in the history of fossils, are more -remarkable than this, and none more directly assimilates the operations -of the mineral regions, with those that take place at the surface of -the earth. - -69. Again, the disturbance of the strata, wherever veins of whinstone -abound, if not a direct proof of the original fluidity of the -whinstone, is a clear indication of the violence with which it was -introduced into its place. This disturbance of the position of the -strata, by shifting, unusual elevation, and other irregularities, where -they are intersected by whinstone veins, is a fact so well known to -miners, that when they meet with any sudden change in the lying of the -_metals_, they are wont to foretell their approach to masses, or veins -of unstratified matter; and, in their figurative language, point them -out as the causes of the confusion with which they are so generally -accompanied.[21] The mineral veins likewise, as well as the strata, are -often heaved and shifted by the veins of whinstone. - -[Footnote 21: A _Trouble_ is the name which the colliers in this -country give to a vein of whinstone.] - -70. Whinstone of every species is found frequently interposed in -tabular masses, between beds of stratified rocks; and it then adds to -the indications of its igneous origin, already enumerated, some others -that are peculiar to it when in this situation. In such instances, it -is not uncommon to find the strata in some places, contiguous to the -whin, elevated, and bent with their concavity upward, so that they -appear clearly to have been acted on by a force that proceeded from -below, at the same time that they were softened, and rendered in some -degree flexible: it is needless to remark, that these effects can be -explained by nothing but the fusion of the whin; and that the great -force with which it was impelled against the strata, could be produced -by no cause but heat, acting in the manner that is here supposed. - -71. Again, if it be true that the masses of whin, thus interposed -among the strata, were introduced there, after the formation of the -latter, we might expect to find, at least in many instances, that the -beds on which the whinstone rests, and those by which it is covered, -are exactly alike. If these beds were once contiguous, and have been -only heaved up and separated by the irruption of a fluid mass of -subterraneous lava, their identity should still be recognised. Now, -this is precisely what is observed; it is known to hold in a vast -number of instances, and is strikingly exemplified in the rock of -_Salisbury Crag_, near Edinburgh. - -This similarity of the strata that cover the masses of whinstone, -to those that serve as the base on which they rest, and again the -dissimilitude of both to the interposed mass, are facts which I think -can hardly receive any explanation, on the principles of the Neptunian -theory. If these rocks, both stratified and unstratified, are to be -regarded as productions of the sea, the circumstances would require to -be pointed out, which have determined the whinstone, and the beds that -are all round it, to be so extremely unlike in their structure, though -formed at the same time, and in the immediate vicinity of one another; -as also those circumstances, on the other hand, which determined the -stratified deposits above and below the whinstone, to be precisely -the same, though the times of their formation must have been very -different. The homogeneous substances, thus, placed at a distance, and -the heterogeneous brought so closely together, are phenomena equally -unaccountable, in a theory that ascribes their origin to the operation -of the same element, and that necessarily dates their formation -according to the order in which they lie, one above another. - -72. If, indeed, in these instances, the gradation were insensible, as -some have asserted it to be, between the strata and the interposed -mass, so that it was impossible to point out the line where the one -ended and the other began, whatever difficulties we might perceive in -the Neptunian theory, we should find it hard to substitute a better -in its room. But the truth seems to be, that, in the cases we are now -treating of, no such gradation exists; and that, though where the two -kinds of rock come into contact a change is often observed, by the -strata having acquired an additional degree of induration, yet the line -of separation is well defined, and can be precisely ascertained. This -at least is certain, that innumerable specimens, exhibiting such lines -of separation, are to be met with; and wherever care has been taken -to obtain a fresh fracture of the stone, and to remove the effects of -accidental causes, even where the two rocks are most firmly united, -and most closely assimilated, I am persuaded that no uncertainty has -ever remained as to the line of their separation. For these reasons, -it seems probable that the gradual transition of basaltes into the -adjoining strata, is in all cases imaginary, and is, in truth, a mere -illusion, proceeding from hasty and inaccurate observation. - -73. Another remarkable fact in the natural history of the whinstone -rocks, remains yet to be mentioned, and with it I shall conclude the -argument, as far as these rocks are concerned. - -Some of the species of whinstone are the common matrices of agates and -chalcedonies, which lie inclosed in them in the form of round nodules. -The original fluidity of these nodules is evinced by their figured, and -sometimes crystallized structure, and indeed is so generally admitted, -that the only question concerning them is, whether this fluidity -was the effect of heat or of solution. To answer this question, Dr -Hutton observes, that the formation of the concentric coats, of which -the agate is usually composed, has evidently proceeded from the -circumference toward the centre, the exterior coats always impressing -the interior, but never the reverse. The same thing also follows from -this other fact, that when there is any vacuity within the agate, it is -usually at the centre, and there too are found the regular crystals, -when any such have been formed. It therefore appears certain, that the -progress of consolidation has been from the circumference inwards, and -that the outward coats of the agate were the first to acquire solidity -and hardness. - -74. Now, it must be considered that these coats are highly -consolidated; that they are of very pure siliceous matter, and are -utterly impervious to every substance which we know of, except light -and heat. It is plain, therefore, that whatever at any time, during -the progress of consolidation, was contained within the coats already -formed, must have remained there as long as the agate was entire, -without the least possibility of escape. But nothing is found within -the coats of the agate save its own substance; therefore, no extraneous -substance, that is to say no solvent, was ever included within them. -The fluidity of the agate was therefore simple, and unassisted by any -menstruum. - -In this argument, nothing appears to me wanting, that is necessary to -the perfection of a physical, I had almost said of a mathematical, -demonstration. It seems, indeed, to be impossible that the igneous -origin of fossils could be recorded in plainer language, than by the -phenomenon which has just been described. - -75. The examination of particular specimens of agates and chalcedonies, -affords many more arguments of the same kind, which Dr Hutton used to -deduce with an acuteness and vivacity, which his friends have often -listened to with great admiration and delight.[22] These, however, -must be passed over at present; and I have only further to remark, -that a series of the most interesting experiments, instituted by Sir -JAMES HALL, and published in the Transactions of the Royal Society of -Edinburgh,[23] has removed the only remaining objection that could -be urged against the igneous origin of whinstone. This objection is -founded on the common observation, that when a piece of whinstone or -basaltes is actually melted in a crucible, on cooling, it becomes -glass, and loses its original character entirely; and from thence it -was concluded, that this character had not been originally produced -by fusion. The experiments above mentioned, however, have shown, in -the most satisfactory manner, that melted whin, by _regulated_ or by -slow cooling, is prevented from assuming the appearance of glass, and -becomes a stony substance, hardly to be distinguished from whinstone or -lava. - -[Footnote 22: NOTE XVI.] - -[Footnote 23: vol. v. p. 43.] - -The experiments of another ingenious chemist, Dr KENNEDY, have shown, -that whinstone contains mineral alkali, by which, of course, its fusion -must have been assisted.[24] Dr Hutton used to ascribe its fusibility, -in a great measure at least, to the quantity of iron contained in it: -both these causes have no doubt united to render it more easily melted -than the ordinary materials of the strata. - -[Footnote 24: Trans. R. S. Edin. vol. v. p. 85.] - -76. In a word, therefore, to conceive aright the origin of that class -of unstratified rocks, distinguished by the name of whinstone, we must -suppose, that long after the consolidation of the strata, and during -the time of their elevation, the materials of the former were melted -by the force of subterraneous heat, and injected among the rents and -fissures of the rocks already formed. In this manner were produced -the veins or dikes of whinstone; and, where circumstances allowed -the stream of melted matter to diffuse itself more widely, tabular -masses were formed, which were afterwards raised up, together with the -surrounding strata, above the level of the sea, and have been since -laid open by the operation of those causes that continually change and -waste the surface of the land. - -These unstratified rocks are not, however, all the work of the same -period; they differ evidently in the date of their formation, and it is -not unusual, to find tabular masses of one species of whin, intersected -by veins of another species. Indeed, of all the fossil bodies which -compose the present land, the veins of whin appear to be the most -recently consolidated.[25] - -[Footnote 25: NOTE XIV.] - -Porphyry may so properly be regarded as a variety of whin, -distinguished only by involving crystallized feldspar, that, in a -geological sketch like the present, it is hardly entitled to a separate -article. Like the other kinds of whin, it exists both in veins and -in tabular masses, having, no doubt, an origin similar to that which -has just been described. Porphyry, however, has the peculiarity of -being rarely found in any but the primary strata; it seems to be the -whinstone of the old world, or at least that which is of the highest -antiquity in the present. It no where, I believe, assumes a columnar, -or basaltic appearance, of any regularity; but this is also true of -many other varieties of whin, of all, indeed, except the most compact -and homogeneous. These differences are not so considerable as to -require our entering into any particular detail concerning the natural -history of this fossil. - - - 3. _Granite_. - -77. The term Granite is used by Dr Hutton to signify an aggregate -stone, in which quartz, feldspar, and mica are found distinct from -one another, and not disposed in layers. The addition of hornblende, -schorl, or garnet, to the three ingredients just mentioned, is not -understood to alter the _genus_ of the stone, but only to constitute a -specific difference, which it is the business of lithology to mark by -some appropriate character, annexed to the generic name of granite. - -The fossil now defined exists, like whinstone and porphyry, both in -masses and in veins, though most frequently in the former. It is like -them unstratified in its texture, and is regarded here, as being also -unstratified in its outward structure.[26] One ingredient which is -essential to granite, namely, quartz, is not contained in whinstone; -and this circumstance serves to distinguish these _genera_ from one -another, though, in other respects, they seem to be united by a chain -of insensible gradations, from the most homogeneous basaltes, to -granite the most highly crystallized. - -[Footnote 26: Those rocks that consist of the ingredients here -enumerated, if they have at the same time a schistose texture, or a -disposition into layers, are properly distinguished from granite, and -called Gneiss, or Granitic Schistus. But it has been questioned whether -a stone does not exist composed of these ingredients, and destitute -of a schistose texture, but yet divided into large beds, visible in -its external form. Dr Hutton supposes such a stone not to exist, or at -least not to constitute any such proportion of the mineral kingdom, as -to entitle it to particular consideration, in the general speculations -of geology. - -Whether this supposition is perfectly correct, may require to be -farther considered: this, however, is certain, that a rock, in all -respects conformable to it, composes a great proportion of what are -usually called the granite mountains. See NOTE XV.] - -78. Granite, it has been just said, exists most commonly in masses; and -these masses are rarely, if ever, incumbent on any other rock: they are -the basis on which others rest, and seem, for the most part, to rise -up from under the ancient, or primary strata. The granite, therefore, -wherever it is found, is inferior to every other rock; and as it also -composes many of the greatest mountains, it has the peculiarity of -being elevated the highest into the atmosphere, and sunk the deepest -under the surface, of all the mineral substances with which we are -acquainted. - -Notwithstanding the circumstance of not being alternated with -stratified bodies, which constitutes a remarkable difference between -granite and whinstone, the affinity of these fossils is such as to make -the similarity of their origin by no means improbable. Accordingly, -in Dr Hutton's theory, granite is regarded as a stone of more recent -formation than the strata incumbent on it; as a substance which has -been melted by heat, and which, when forced up from the mineral -regions, has elevated the strata at the same time. - -79. That granite has undergone a change from a fluid to a solid -state, is evinced from the crystallized structure in which some of -its component parts are usually found. This crystallization is -particularly to be remarked of the feldspar, and also of the schorl, -where there is any admixture of that substance, whether in slender -spiculæ, or in larger masses. The quartz itself is in some cases -crystallized, and is so, perhaps, more frequently than is generally -supposed. The fluidity of granite, in some former period of its -existence, is so evident from this, as to make it appear singular that -it should ever have been considered as a fossil that had remained -always the same, and one, into the origin of which it was needless to -inquire. If the regular forms of crystallization are not to be received -as proofs of the substance to which they belong having passed from -a fluid to a solid state, neither are the figures of shells and of -other supposed petrifactions, to be taken as indications of a passage -from the animal to the mineral kingdom; so that there is an end of -all geological theories, and of all reasonings concerning the ancient -condition of the globe. To an argument which strikes equally at the -root of all theories, it belongs not to this, in particular, to make -any reply. - -80. We shall, therefore, consider it as admitted, that the materials -of the granite were originally fluid; and, in addition to this, we -think it can easily be proved, that this fluidity was not that of the -elements taken separately, but of the entire mass. This last conclusion -follows, from the structure of those specimens, where one of the -substances is impressed by the forms which are peculiar to another. -Thus, in the Portsoy granite,[27] which Dr Hutton has so minutely -described, the quartz is impressed by the rhomboidal crystals of the -feldspar, and the stone thus formed is compact and highly consolidated. -Hence, this granite is not a congeries of parts, which, after being -separately formed, were somehow brought together and agglutinated; but -it is certain that the quartz, at least, was fluid when it was moulded -on the feldspar. In other granites, the impressions of the substances -on one another are observed in a different order, and the quartz gives -its form to the feldspar. This, however, is more unusual; the quartz -is commonly the substance which has received the impressions of all -the rest; and the spiculæ of schorl often shoot both across it and the -feldspar. - -[Footnote 27: Theory of the Earth, vol. i. p. 104.] - -The ingredients of granite were therefore fluid when mixed, or at least -when in contact with one another. Now, this fluidity was not the effect -of solution in a menstruum; for, in that case, one kind of crystal -ought not to impress another, but each of them should have its own -peculiar shape. - -81. The perfect consolidation of many granites, furnishes an argument -to the same effect. For, agreeably to what was already observed, in -treating of the strata, a substance, when crystallizing, or passing -from a fluid to a solid state, cannot be free from porosity, much -less fill up completely a space of a given form, if, at the same -time, any solvent is separated from it; because the solvent so -separated would still occupy a certain space, and, when removed by -evaporation or otherwise, would leave that space empty. The perfect -adjustment, therefore, of the shape of one set of crystallizing bodies, -to the shape of another set, as in the Portsoy granite, and their -consolidation into one mass, is as strong a proof as could be desired, -that they crystallized from a state of simple fluidity, such as, of all -known causes, heat alone is able to produce. - -82. This conclusion, however, does not rest on a single class of -facts. It has been observed in many instances, that where granite and -stratified rocks, such as primary schistus, are in contact, the latter -are penetrated by veins of the former, which traverse them in various -directions. These veins are of different dimensions, some being of the -breadth of several yards, others of a few inches, or even tenths of an -inch; they diminish as they recede from the main body of the granite, -to which they are always firmly united, constituting, indeed, a part of -the same continued rock. - -These phenomena, which were first distinctly observed by Dr Hutton, are -of great importance in geology, and afford a clear solution of the two -chief questions concerning the relation between granite and schistus. -As every vein must be of a date posterior to the body in which it is -contained, it follows, that the schistus was not super-imposed on -the granite, after the formation of this last. If it be argued, that -these veins, though posterior to the schisti, are also posterior to -the granite, and were formed by the infiltration of water in which the -granite was dissolved or suspended; it may be replied, _1mo_, That the -power of water to dissolve granite, is a postulatum of the same kind -that we have so often, and for such good reason, refused to concede; -and, _2do_, That in many instances the veins proceed from the main -body of the granite _upwards_ into the schistus; so that they are in -planes much elevated in respect of the horizon, and have a direction -quite opposite to that which the hypothesis of infiltration requires. -It remains certain, therefore, that the whole mass of granite, and the -veins proceeding from it, are coeval, and both of later formation than -the strata. - -Now, this being established, and the fluidity of the veins, when they -penetrated into the schistus, being obvious, it necessarily follows, -that the whole granite mass was also fluid at the same time. But this -can have been brought about only by subterraneous heat, which also -impelled the melted matter against the superincumbent strata, with such -force as to raise them from their place, and to give them that highly -inclined position in which they are still supported by the granite, -after its fluidity has ceased. Thus a conclusion, rendered probable by -the crystallization of granite, is established beyond all contradiction -by the phenomena of granitic veins.[28] - -[Footnote 28: NOTE XV.] - -83. With the granite, we shall consider the proof of the igneous origin -of all mineral substances as completed. These substances, therefore, -whether stratified or unstratified, owe their consolidation to the same -cause, though acting with different degrees of energy. The stratified -have been in general only softened or penetrated by melted matter, -whereas the unstratified have been reduced into perfect fusion. - -84. In this general conclusion we may distinguish two parts, which, in -their degree of certainty, differ perhaps somewhat from one another. -The first of these, and that which stands highest in point of evidence, -consists of two propositions; namely, that the fluidity which preceded -the consolidation of mineral substances was SIMPLE, that is, it did not -arise from the combination of these substances with any solvent; and, -next, that after consolidation, these bodies have been raised up by an -expansive force acting from below, and have by that means been brought -into their present situation. These two propositions seem to me to be -supported by all the evidence that is necessary to constitute the most -perfect demonstration. - -85. The other part of the general conclusion, that fire, or more -properly heat, was the cause of the fluidity of these mineral bodies, -and also of their subsequent elevation, is not perhaps to be considered -as a truth so fully demonstrated as the two preceding propositions; -it is, no doubt, a matter of THEORY; or a portion of one of those -invisible chains by which men seek to connect in the mind the state -of nature that is present, with the states of it that are past; and -participates of that uncertainty from which our reasonings concerning -such causes as are not direct objects of perception, are hardly ever -exempted. That it participates of this uncertainty in a very slight -degree, will, however, be admitted, when it is considered that the -cause assigned has been proved sufficient for the effect; that the same -is not true of any other known cause; and that this theory accounts, -with singular simplicity and precision, for a system of facts so -various and complex, as that which is presented by the natural history -of the globe. - -86. Neither can it be said that the existence of subterraneous heat is -a principle assumed without any evidence, but that of the geological -facts which it is intended to explain: on the contrary, it is proved by -phenomena within the circle of ordinary experience, namely, those of -hot springs, volcanoes, and earthquakes. These leave no doubt of the -existence of heat, and of a moving and expansive power, in the bowels -of the earth; so that the only questions are, at what depth is this -power lodged? to what extent, and with what intensity, does it act? -That it is lodged at a very considerable depth, is rendered probable by -the permanency of some of the preceding phenomena: from the earliest -times many fountains have retained their heat to the present day; and -volcanoes, though they become extinguished at length, have a very -long period allotted for their duration. The cause of earthquakes is -certainly a force that resides very deep under the surface, otherwise -the extent of the concussion could not be such as has been observed in -many instances. - -87. The intensity of volcanic fire, is another circumstance that -favours the opinion of its being seated deep under the surface. That -this intensity is considerable, is certain from the experiments made -by Sir James Hall on the fusibility of whinstone and lava; from which -it appears, that the lowest temperature in which either of these -stones melt, is about 80° of Wedgewood's pyrometer. Some mineralogists -have indeed affirmed, that lava is melted, not by the intensity of -the heat applied to it, but in consequence of a certain combination -formed between it and bituminous substances, in a manner which they do -not attempt to explain, and which has indeed no analogy to any thing -that is known. That a hypothesis, formed in such direct opposition to -the most obvious principles of inductive reasoning, should have been -imagined by a philosopher who had examined the phenomena of Etna and -Vesuvius with much attention, and described them with great accuracy -and truth, is more wonderful than that it should have been adopted by -mineralogists, whose views of nature may have been confined within a -cabinet or a laboratory. It is, however, a hypothesis, which, having -never had any support but from other hypotheses, hardly merited the -direct refutation that it has received from the experiments just -mentioned. - -88. But, if the intensity of volcanic heat be such as is here -stated, it will be found very difficult to account for a fire of -such activity, and of such long continuance in the same spot, by any -decomposition of mineral substances near the surface. In the place -where this combustion is supposed to exist, it must be remembered, -that there is no fresh supply of materials to replace those that have -been consumed, and that, therefore, the original accumulation of these -materials in one spot, must have been very unlike any thing that has -ever been observed concerning the disposition of minerals in the bowels -of the earth. - -89. If, on the other hand, we ascribe the phenomena of volcanoes to -the central heat, the account that may be given of them is simple, and -consistent with itself. According to all the appearances from which the -existence of such heat has been inferred above, it is of a nature so -far different from ordinary fire, that it may require no circulation -of air, and no supply of combustible materials to support it. It is -not accompanied with inflammation or combustion, the great pressure -preventing any separation of parts in the substances on which it acts, -and the absence of that elastic fluid without which heat seems to have -no power to decompose bodies, even the most combustible, contributing -to the unalterable nature of all the substances in the mineral regions. -There, of consequence, the only effects of heat are fusion and -expansion; and that which forms the nucleus of the globe may therefore -be a fluid mass, melted, but unchanged by the action of heat. - -90. If, from the confines of this nucleus, we conceive certain fissures -and openings to traverse the solid crust, and to issue at the surface -of the earth, the vapours ascending through these may in time heat the -sides of the tubes through which they pass to a vast distance from the -lower extremities. It is, indeed, difficult to fix the limit to which -this distance may extend, on account of the great difference between -the rate at which heat moves when it has a fluid for its vehicle, and -when it is left to make its way alone through a solid body. In the -present case, the supply of heat is rapid, as being made by a vapour -ascending through a tube of solid rock; and the dissipation of it slow, -as arising from its transmission through the rock. The waste of heat is -therefore small, compared with the supply, and grows smaller at every -given point, the longer the stream of heated vapour has continued to -flow. Such a stream, therefore, though it may at first be condensed -within a small distance of its source, will in time reach higher -and higher, and may at last be able to carry its heat to an immense -distance from the place of its original derivation. Thus, it is easy -to conceive, that vapours from the mineral regions may convey their -heat to reservoirs of water near the surface of the earth, and may in -that manner produce hot springs, and even boiling fountains, like those -of Rycum and Geyser. - -91. When, instead of a heated vapour, melted matter is thrown up -through the _shafts_ or _tubes_, which thus communicate with the -mineral regions, veins of whinstone and basaltes are formed in the -interior of the earth. When the melted matter reaches to the surface, -it is thrown out in the form of lava, and all the other phenomena of -volcanoes are produced. - -Lastly, where melted matter of this kind, or vapours without being -condensed, have their progress obstructed, those dreadful concussions -are produced, which seem to threaten the existence even of the earth -itself. Though terrible, therefore, to the present inhabitants of the -globe, the earthquake has its place in the great system of geological -operations, and is part of a series of events, essential, as will more -clearly appear hereafter, to the general order, and to the preservation -of the whole. - -Such, according to this theory, are the changes which have befallen -mineral substances in the bowels of the earth; and though different -for the stratified and unstratified parts of those substances, they -are connected together by the same _principle_, or explained by the -same _cause_. It remains to consider that part of the history of both -which describes their changes after their elevation to the surface; -and here we shall find new causes introduced, which are more directly -the subjects of observation, than those hitherto treated of; causes, -also, which act on all fossils alike, and alike prepare them for their -ultimate destination. - - - - - SECTION III. - - OF THE PHENOMENA COMMON TO STRATIFIED - AND UNSTRATIFIED BODIES. - - -92. THE series of changes which fossil bodies are destined to undergo, -does not cease with their elevation above the level of the sea; it -assumes, however, a new direction, and from the moment that they are -raised up to the surface, is constantly exerted in reducing them again -under the dominion of the ocean. The solidity is now destroyed which -was acquired in the bowels of the earth; and as the bottom of the -sea is the great laboratory, where loose materials are mineralized -and formed into stone, the atmosphere is the region where stones are -decomposed, and again resolved into earth. - -This decomposition of all mineral substances, exposed to the air, -is continual, and is brought about by a multitude of agents, both -chemical and mechanical, of which some are known to us, and many, no -doubt, remain to be discovered. Among the various aëriform fluids which -compose our atmosphere, one is already distinguished as the grand -principle of mineral decomposition; the others are not inactive, and -to them we must add moisture, heat, and perhaps light; substances -which, from their affinities to the elements of mineral bodies, have a -power of entering into combination with them, and of thus diminishing -the forces by which they are united to one another. By the action of -air and moisture, the metallic particles, particularly the iron, which -enters in great abundance into the composition of almost all fossils, -becomes oxydated in such a degree as to lose its tenacity; so that the -texture of the surface is destroyed, and a part of the body resolved -into earth. - -93. Some earths, again, such as the calcareous, are immediately -dissolved by water; and though the quantity so dissolved be extremely -small, the operation, by being continually renewed, produces a slow -but perpetual corrosion, by which the greatest rocks must in time be -subdued. The action of water in destroying hard bodies into which it -has obtained entrance, is much assisted by the vicissitudes of heat -and cold, especially when the latter extends as far as the point of -congelation; for the water, when frozen, occupies a greater space than -before, and if the body is compact enough to refuse room for this -expansion, its parts are torn asunder by a repulsive force acting in -every direction. - -94. Besides these causes of mineral decomposition, the action of which -we can in some measure trace, there are others known to us only by -their effects. - -We see, for instance, the purest rock crystal affected by exposure -to the weather, its lustre tarnished, and the polish of its surface -impaired, but we know nothing of the power by which these operations -are performed. Thus also, in the precautions which the mineralogist -takes to preserve the fresh fracture of his specimens, we have a proof -how indiscriminately all the productions of the fossil kingdom are -exposed to the attacks of their unknown enemies, and we perceive how -difficult it is to delay the beginnings of a process which no power -whatever can finally counteract. - -95. The mechanical forces employed in the disintegration of mineral -substances, are more easily marked than the chemical. Here again water -appears as the most active enemy of hard and solid bodies; and, in -every state, from transparent vapour to solid ice, from the smallest -rill to the greatest river, it attacks whatever has emerged above the -level of the sea, and labours incessantly to restore it to the deep. -The parts loosened and disengaged by the chemical agents, are carried -down by the rains, and, in their descent, rub and grind the superficies -of other bodies. Thus water, though incapable of acting on hard -substances by direct attrition, is the cause of their being so acted -on; and, when it descends in torrents, carrying with it sand, gravel, -and fragments of rock, it may be truly said to turn the forces of the -mineral kingdom against itself. Every separation which it makes is -necessarily permanent, and the parts once detached can never be united, -save at the bottom of the ocean. - -96. But it would far exceed the limits of this sketch, to pursue -the causes of mineral decomposition through all their forms. It is -sufficient to remark, that the consequence of so many minute, but -indefatigable agents, all working together, and having _gravity_ in -their favour, is a system of universal decay and degradation, which -may be traced over the whole surface of the land, from the mountain -top to the sea shore. That we may perceive the full evidence of this -truth, one of the most important in the natural history of the globe, -we will begin our survey from the latter of these stations, and retire -gradually toward the former. - -97. If the coast is bold and rocky, it speaks a language easy to -be interpreted. Its broken and abrupt contour, the deep gulfs and -salient promontories by which it is indented, and the proportion which -these irregularities bear to the force of the waves, combined with -the inequality of hardness in the rocks, prove, that the present -line of the shore has been determined by the action of the sea. The -naked and precipitous cliffs which overhang the deep, the rocks -hollowed, perforated, as they are farther advanced in the sea, and at -last insulated, lead to the same conclusion, and mark very clearly -so many different stages of decay. It is true, we do not see the -successive steps of this progress exemplified in the states of the same -individual rock, but we see them clearly in different individuals; -and the conviction thus produced, when the phenomena are sufficiently -multiplied and varied, is as irresistible, as if we saw the changes -actually effected in the moment of observation. - -On such shores, the fragments of rock once detached, become instruments -of further destruction, and make a part of the powerful artillery with -which the ocean assails the bulwarks of the land: they are impelled -against the rocks, from which they break off other fragments, and the -whole are thus ground against one another; whatever be their hardness, -they are reduced to gravel, the smooth surface and round figure of -which, are the most certain proofs of a _detritus_ which nothing can -resist. - -98. Again, where the sea coast is flat, we have abundant evidence of -the degradation of the land in the beaches of sand and small gravel; -the sand banks and shoals that are continually changing; the alluvial -land at the mouths of the rivers; the bars that seem to oppose their -discharge into the sea, and the shallowness of the sea itself. On -such coasts, the land usually seems to gain upon the sea, whereas, -on shores of a bolder aspect, it is the sea that generally appears -to gain upon the land. What the land acquires in extent, however, it -loses in elevation; and, whether its surface increase or diminish, the -depredations made on it are in both cases evinced with equal certainty. - -99. If we proceed in our survey from the shores, inland, we meet -at every step with the fullest evidence of the same truths, and -particularly in the nature and economy of rivers. Every river appears -to consist of a main trunk, fed from a variety of branches, each -running in a valley proportioned to its size, and all of them together -forming a system of vallies, communicating with one another, and having -such a nice adjustment of their declivities, that none of them join the -principal valley, either on too high or too low a level; a circumstance -which would be infinitely improbable, if each of these vallies were not -the work of the stream that flows in it. - -If indeed a river consisted of a single stream, without branches, -running in a straight valley, it might be supposed that some great -concussion, or some powerful torrent, had opened at once the channel -by which its waters are conducted to the ocean; but, when the usual -form of a river is considered, the trunk divided into many branches, -which rise at a great distance from one another, and these again -subdivided into an infinity of smaller ramifications, it becomes -strongly impressed upon the mind, that all these channels have been cut -by the waters themselves; that they have been slowly dug out by the -washing and erosion of the land; and that it is by the repeated touches -of the same instrument, that this curious assemblage of lines has been -engraved so deeply on the surface of the globe. - -100. The changes which have taken place in the courses of rivers, are -also to be traced, in many instances, by successive platforms, of flat -alluvial land, rising one above another, and marking the different -levels on which the river has run at different periods of time. Of -these, the number to be distinguished, in some instances, is not less -than four, or even five; and this necessarily carries us back, like -all the operations we are now treating of, to an antiquity extremely -remote: for, if it be considered, that each change which the river -makes in its bed, obliterates at least a part of the monuments of -former changes, we shall be convinced, that only a small part of the -progression can leave any distinct memorial behind it, and that there -is no reason to think, that, in the part which we see, the beginning is -included.[29] - -[Footnote 29: NOTE XVI.] - -101. In the same manner, when a river undermines its banks, it often -discovers deposits of sand and gravel, that have been made when it ran -on a higher level than it does at present. In other instances, the same -strata are seen on both the banks, though the bed of the river is now -sunk deep between them, and perhaps holds as winding a course through -the solid rock, as if it flowed along the surface; a proof that it must -have begun to sink its bed, when it ran through such loose materials as -opposed but a very inconsiderable resistance to its stream. A river, of -which the course is both serpentine and deeply excavated in the rock, -is among the phenomena, by which the slow waste of the land, and also -the cause of that waste, are most directly pointed out. - -102. It is, however, where rivers issue through narrow defiles among -mountains, that the identity of the strata on both sides is most easily -recognised, and remarked at the same time with the greatest wonder. On -observing the Potowmack, where it penetrates the ridge of the Allegany -mountains, or the Irtish, as it issues from the defiles of Altai, -there is no man, however little addicted to geological speculations, -who does not immediately acknowledge, that the mountain was once -continued quite across the space in which the river now flows; and, if -he ventures to reason concerning the cause of so wonderful a change, -he ascribes it to some great convulsion of nature, which has torn the -mountain asunder, and opened a passage for the waters. It is only the -philosopher, who has deeply meditated on the effects which action long -continued is able to produce, and on the simplicity of the means which -nature employs in all her operations, who sees in this nothing but the -gradual working of a stream, that once flowed over the top of the ridge -which it now so deeply intersects, and has cut its course through the -rock, in the same way, and almost with the same instrument, by which -the lapidary divides a block of marble or granite. - -103. It is highly interesting to trace up, in this manner, the action -of causes with which we are familiar, to the production of effects, -which at first seem to require the introduction of unknown and -extraordinary powers; and it is no less interesting to observe, how -skilfully nature has balanced the action of all the minute causes of -waste, and rendered them conducive to the general good. Of this we -have a most remarkable instance, in the provision made for preserving -the soil, or the coat of vegetable mould, spread out over the surface -of the earth. This coat, as it consists of loose materials, is easily -washed away by the rains, and is continually carried down by the rivers -into the sea. This effect is visible to every one; the earth is removed -not only in the form of sand and gravel, but its finer particles -suspended in the waters, tinge those of some rivers continually, and -those of all occasionally, that is, when they are flooded or swollen -with rains. The quantity of earth thus carried down, varies according -to circumstances; it has been computed, in some instances, that the -water of a river in a flood, contains earthy matter suspended in it, -amounting to more than the two hundred and fiftieth part of its own -bulk.[30] The soil, therefore, is continually diminished, its parts -being transported from higher to lower levels, and finally delivered -into the sea. But it is a fact, that the soil, notwithstanding, remains -the same in quantity, or at least nearly the same, and must have done -so, ever since the earth was the receptacle of animal or vegetable -life. The soil, therefore, is augmented from other causes, just as -much, at an average, as it is diminished by that now mentioned; and -this augmentation evidently can proceed from nothing but the constant -and slow disintegration of the rocks. In the permanence, therefore, -of a coat of vegetable mould on the surface of the earth, we have a -demonstrative proof of the continual destruction of the rocks; and -cannot but admire the skill, with which the powers of the many chemical -and mechanical agents employed in this complicated work, are so -adjusted, as to make the supply and the waste of the soil exactly equal -to one another. - -[Footnote 30: See Lehman, Traités de Phys. &c. tom. iii. p. 359. Note.] - -104. Before we take leave of the rivers and the plains, we must remark -another fact, often observed in the natural history of the latter, and -clearly evincing the former existence of immense bodies of strata, in -situations from which they have now entirely disappeared. The fact here -alluded to is, the great quantity of round and hard gravel, often to be -met with in the soil, under such circumstances, as prove, that it can -only have come from the decomposition of rocks, that once occupied the -very ground over which this gravel is now spread. In the chalk country, -for instance, about London, the quantity of flints in the soil is every -where great; and, in particular situations, nothing but flinty gravel -is found to a considerable depth. Now, the source from which these -flints are derived is quite evident, for they are precisely the same -with those contained in the chalk beds, wherever these last are found -undisturbed, and from the destruction of such beds they have no doubt -originated. Hence a great thickness of chalk must have been decomposed, -to yield the quantity of flints now in the soil of these countries; for -the flints are but thinly scattered through the native chalk, compared -with their abundance in the loose earth. To afford, for example, such -a body of flinty gravel as is found about Kensington, what an enormous -quantity of chalk rock must have been destroyed? - -105. This argument, which Dr Hutton has applied particularly to the -chalk countries, may be extended to many others. The great plain of -Crau, near the mouth of the Rhone, is well known, and was regarded -with wonder, even in ages when the natural history of the globe was -not an object of much attention. The immense quantity of large round -gravel-stones, with which this extensive plain is entirely covered, -has been supposed, by some mineralogists, to have been brought down -by the Durance, and other torrents, from the Alps; but, on further -examination, has been found to be of the same kind that is contained -in certain horizontal layers of pudding-stone, which are the basis of -the whole plain. It cannot be doubted, therefore, that the vast body of -gravel spread over it, has originated from the destruction of layers -of the same rock, which may perhaps have risen to a great height above -what is now the surface. Indeed, from knowing the depth of the gravel -that covers the plain, and the average quantity of the like gravel -contained in a given thickness of rock, one might estimate how much of -the latter has been actually worn away. Whether data precise enough -could be found, to give any weight to such a computation, must be left -fer future inquiry to determine.[31] - -[Footnote 31: NOTE XVII.] - -106. In these instances, chalk and pudding-stone, by containing in -them parts infinitely less destructible than their general mass, have, -after they are worn away, left behind them very unequivocal marks of -their existence. The same has happened in the case of mineral veins, -where the substances least subject to dissolution have remained, -and are scattered at a great distance from their native place. Thus -gold, the least liable to decomposition of all the metals, is very -generally diffused through the earth, and is found, in a greater or -less abundance, in the sand of almost all rivers. But the native place -of this mineral is the solid rock, or the veins and cavities contained -in the rock, and from thence it must have made its way into the soil. -This, therefore, is another proof of the vast extent to which the -degradation of the land, and of the rock, which is the basis of it, -has been earned; and consequently, of the great difference between -the elevation and shape of the earth's surface in the present, and in -former ages. - -107. The veins of tin furnish an argument of the same kind. The -ores of this metal are very indestructible, and little subject to -decomposition, so that they remain very long in the ground without -change. Where there are tin veins, as in Cornwall, the tin-stone or tin -ore is found in great abundance in such vallies and streams as have -the same direction with the veins; and hence the _streaming_, as it is -called, or washing of the earth, to obtain the tin-stone from it. Now, -if it be considered, that none of this ore can have come into the soil -but from parts of a vein actually destroyed, it must appear evident -that a great waste of these veins has taken place, and consequently of -the schistus or granite in which they are contained. - -108. These lessons, which the geologist is taught in flat and open -countries, become more striking, by the study of those Alpine tracts, -where the surface of the earth attains its greatest elevation. If we -suppose him placed for the first time in the midst of such a scene, -as soon as he has recovered from the impression made by the novelty -and magnificence of the spectacle before him, he begins to discover -the footsteps of time, and to perceive, that the works of nature, -usually deemed the most permanent, are those on which the characters -of vicissitude are most deeply imprinted. He sees himself in the midst -of a vast ruin, where the precipices which rise on all sides with -such boldness and asperity, the sharp peaks of the granite mountains, -and the huge fragments that surround their bases, do but mark so many -epochs in the progress of decay, and point out the energy of those -destructive causes, which even the magnitude and solidity of such great -bodies have been unable to resist. - -109. The result of a more minute investigation, is in perfect unison -with this general impression. Whence is it, that the elevation -of mountains is so obviously connected with the hardness and -indestructibility of the rocks which compose them? Why is it, that a -lofty mountain of soft and secondary rock is no where to be found; and -that such chains, as the Pyrenees or the Alps, never consist of any -but the hardest stone, of granite for instance, or of those primary -strata, which, if we are to credit the preceding theory, have been -twice heated in the fires, and twice tempered in the waters, of the -mineral regions? Is it not plain that this arises, not from any direct -connection between the hardness of stones, and their height in the -atmosphere, but from this, that the waste and _detritus_ to which all -things are subject, will not allow soft and weak substances to remain -long in an exposed and elevated situation? Were it not for this, the -secondary rocks, being in position superincumbent on the primary, ought -to be the highest of the two, and should cover the primary, (as they -no doubt have at one time done,) in the highest as well as the lowest -situations, or among the mountains as well as in the plains. - -110. Again, wherefore is it, that among all mountains, remarkable for -their ruggedness and asperity, the rock, on examination, is always -found of very unequal destructibility, some parts yielding to the -weather, and to the other causes of disintegration, much more slowly -than the rest, and having strength sufficient to support themselves, -when left alone, in slender pyramids, bold projections, and overhanging -cliffs? Where, on the other hand, the rock wastes uniformly, the -mountains are similar to one another; their swells and slopes are -gentle, and they are bounded by a waving and continuous surface. The -intermediate degrees of resistance which the rocks oppose to the causes -of destruction, produce intermediate forms. It is this which gives to -the mountains, of every different species of rock, a different habit -and expression, and which, in particular, has imparted to those of -granite that venerable and majestic character, by which they rarely -fail to be distinguished. - -111. The structure of the vallies among mountains, shows clearly to -what cause their existence is to be ascribed. Here we have first a -large valley, communicating directly with the plain, and winding -between high ridges of mountains, while the river in the bottom of it -descends over a surface, remarkable, in such a scene, for its uniform -declivity. Into this, open a multitude of transverse or secondary -vallies, intersecting the ridges on either side of the former, each -bringing a contribution to the main stream, proportioned to its -magnitude; and, except where a cataract now and then intervenes, -all having that nice adjustment in their levels, (99.) which is the -more wonderful, the greater the irregularity of the surface. These -secondary vallies have others of a smaller size opening into them; -and, among mountains of the first order, where all is laid out on the -greatest scale, these ramifications are continued to a fourth, and -even a fifth, each diminishing in size as it increases in elevation, -and as its supply of water is less. Through them all, this law is in -general observed, that where a higher valley joins a lower one, of the -two angles which it makes with the latter, that which is obtuse is -always on the descending side; a law that is the same with that which -regulates the confluence of streams running on a surface nearly of -uniform inclination. This alone is a proof that the vallies are the -work of the streams; and indeed what else but the water itself, working -its way through obstacles of unequal resistance, could have opened or -kept up a communication between the inequalities of an irregular and -alpine surface? - -112. Many more arguments, all leading to the same conclusion, may -be deduced from the general facts, known in the natural history of -mountains; and, if the Oreologist would trace back the progress of -waste, till he come in sight of that original structure, of which -the remains are still so vast, he perceives an immense mass of solid -rock, naked and unshapely, as it first emerged from the deep, and -incomparably greater than all that is now before him. The operation -of rains and torrents, modified by the hardness and tenacity of the -rock, has worked the whole into its present form; has hollowed out -the vallies, and gradually detached the mountains from the general -mass, cutting down their sides into steep precipices at one place, -and smoothing them into gentle declivities at another. From this has -resulted a transportation of materials, which, both for the quantity -of the whole, and the magnitude of the individual fragments, must seem -incredible to every one, who has not learned to calculate the effects -of continued action, and to reflect, that length of time can convert -accidental into steady causes. Hence fragments of rock, from the -central chain, are found to have travelled into distant vallies, even -where many inferior ridges intervene: hence the granite of Mont Blanc -is seen in the plains of Lombardy, or on the sides of Jura; and the -ruins of the Carpathian mountains lie scattered over the shores of the -Baltic.[32] - -[Footnote 32: NOTE XVIII.] - -113. Thus, with Dr Hutton, we shall be disposed to consider those great -chains of mountains, which traverse the surface of the globe, as cut -out of masses vastly greater, and more lofty than any thing that now -remains. The present appearances afford no data for calculating the -original magnitude of these masses, or the height to which they may -have been elevated. The nearest estimate we can form is, where a chain -or group of mountains, like those of Rosa in the Alps, is horizontally -stratified, and where, of consequence, the undisturbed position of the -mineral beds enables us to refer the whole of the present inequalities -of the surface to the operation of waste or decay. These mountains, -as they now stand, may not inaptly be compared to the pillars of earth -which workmen leave behind them, to afford a measure of the whole -quantity of earth which they have removed. As the pillars, (considering -the mountains as such,) are in this case of less height than they -originally were, so the measure furnished by them is but a limit, which -the quantity sought must necessarily exceed. - -114. Such, according to Dr Hutton's theory, are the changes which the -daily operations of waste have produced on the surface of the globe. -These operations, inconsiderable if taken separately, become great, by -conspiring all to the same end, never counteracting one another, but -proceeding, through a period of indefinite extent, continually in the -same direction. Thus every thing descends, nothing returns upward; the -hard and solid bodies every where dissolve, and the loose and soft no -where consolidate. The powers which tend to preserve, and those which -tend to change the condition of the earth's surface, are never _in -equilibrio_; the latter are, in all cases, the most powerful, and, in -respect of the former, are like living in comparison of dead forces. -Hence the law of decay is one which suffers no exception: The elements -of all bodies were once loose and unconnected, and to the same state -nature has appointed that they should all return. - -115. It affords no presumption against the reality of this progress, -that, in respect of man, it is too slow to be immediately perceived: -The utmost portion of it to which our experience can extend, is -evanescent, in comparison with the whole, and must be regarded as the -momentary increment of a vast progression, circumscribed by no other -limits than the duration of the world. TIME performs the office of -integrating the infinitesimal parts of which this progression is made -up; it collects them into one sum, and produces from them an amount -greater than any that can be assigned. - -116. While on the surface of the earth so much is every where going to -decay, no new production of mineral substances is found in any region -accessible to man. The instances of what are called petrifactions, or -the formation of stony substances by means of water, which we sometimes -observe, whether they be ferruginous concretions, or calcareous, or, -as happens in some rare cases, siliceous stalactites, are too few -in number, and too inconsiderable in extent, to be deemed material -exceptions to this general rule. The bodies thus generated, also, are -no sooner formed, than they become subject to waste and dissolution, -like all the other hard substances in nature; so that they but retard -for a while the progress by which they are all resolved into dust, and -sooner or later committed to the bosom of the deep. - -117. We are not, however, to imagine, that there is no where any means -of repairing this waste; for, on comparing the conclusion at which -we are now arrived, viz. that the present continents are all going -to decay, and their materials descending into the ocean, with the -proposition first laid down, that these same continents are composed -of materials which must have been collected from the decay of former -rocks, it is impossible not to recognise two corresponding steps of -the same progress; of a progress, by which mineral substances are -subjected to the same series of changes, and alternately wasted away -and renovated. In the same manner, as the present mineral substances -derive their origin from substances similar to themselves; so, from the -land now going to decay, the sand and gravel forming on the sea shore, -or in the beds of rivers; from the shells and corals, which in such -enormous quantities are every day accumulated in the bosom of the sea; -from the drift wood, and the multitude of vegetable and animal remains -continually deposited in the ocean: from all these we cannot doubt, -that strata are now forming in those regions, to which nature seems -to have confined the powers of mineral reproduction; from which, after -being consolidated, they are again destined to emerge, and to exhibit a -series of changes similar to the past.[33] - -[Footnote 33: NOTE XIX.] - -118. How often these vicissitudes of decay and renovation have been -repeated, is not for us to determine: they constitute a series, of -which, as the author of this theory has remarked, we neither see the -beginning nor the end; a circumstance that accords well with what -is known concerning other parts of the economy of the world. In the -continuation of the different species of animals and vegetables that -inhabit the earth, we discern neither a beginning nor an end; and, -in the planetary motions, where geometry has carried the eye so far -both into the future and the past, we discover no mark, either of -the commencement or the termination of the present order.[34] It is -unreasonable, indeed, to suppose, that such marks should any where -exist. The Author of nature has not given laws to the universe, which, -like the institutions of men, carry in themselves the elements of their -own destruction. He has not permitted, in his works, any symptom of -infancy or of old age, or any sign by which we may estimate either -their fixture or their past duration. He may put an end, as be no doubt -gave a beginning, to the present system, at some determinate period; -but we may safely conclude, that this great _catastrophe_ will not -be brought about by any of the laws now existing, and that it is not -indicated by any thing which we perceive. - -[Footnote 34: NOTE XX.] - -119. To assert, therefore, that, in the economy of the world, we see -no mark, either of a beginning or an end, is very different from -affirming, that the world had no beginning, and will have no end. The -first is a conclusion justified by common sense, as well as sound -philosophy; while the second is a presumptuous and unwarrantable -assertion, for which no reason from experience or analogy can ever be -assigned. Dr Hutton might, therefore, justly complain of the uncandid -criticism, which, by substituting the one of these assertions for the -other, endeavoured to load his theory with the reproach of atheism and -impiety. Mr KIRWAN, in bringing forward this harsh and ill-founded -censure, was neither animated by the spirit, nor guided by the maxims -of true philosophy. By the spirit of philosophy, he must have been -induced to reflect, that such poisoned weapons as he was preparing -to use, are hardly ever allowable in scientific contest, as having -a less direct tendency to overthrow the system, than to hurt the -person of an adversary, and to wound, perhaps incurably, his mind, his -reputation, or his peace. By the maxims of philosophy, he must have -been reminded, that, in no part of the history of nature, has any mark -been discovered, either of the beginning or the end of the present -_order_; and that the geologist sadly mistakes, both the object of his -science and the limits of his understanding, who thinks it his business -to explain the means employed by INFINITE WISDOM for establishing the -laws which now govern the world. - -By attending to these obvious considerations, Mr Kirwan would have -avoided a very illiberal and ungenerous proceeding; and, however he -might have differed from Dr Hutton as to the _truth_ of his opinions, -he would not have censured their _tendency_ with such rash and -unjustifiable severity. - -But, if this author may be blamed for wanting the temper, or neglecting -the rules, of philosophic investigation, he is hardly less culpable, -for having so slightly considered the scope and spirit of a work which -he condemned so freely. In that work, instead of finding the world -represented as the result of necessity or chance, which might be looked -for, if the accusations of atheism or impiety were well founded, we -see every where the utmost attention to discover, and the utmost -disposition to admire, the instances of wise and beneficent design -manifested in the structure, or economy of the world. The enlarged -views of these, which his geological system afforded, appeared to Dr -Hutton himself as its most valuable result. They were the parts of it -which he contemplated with greatest delight; and he would have been -less flattered, by being told of the ingenuity and originality of his -theory, than of the addition which it had made to our knowledge of -_final causes_. It was natural, therefore, that he should be hurt by -an attempt to accuse him of opinions, so different from those which he -had always taught; and if he answered Mr Kirwan's attack with warmth or -asperity, we must ascribe it to the indignation excited by unmerited -reproach. - -120. But to return to the natural history of the earth: Though there be -in it no _data_, from which the commencement of the present order can -be ascertained, there are many by which the existence of that order may -be traced back to an antiquity extremely remote. The beds of primitive -schistus, for instance, contain sand, gravel, and other materials, -collected, as already shown, from the dissolution of mineral bodies; -which bodies, therefore, must have existed long before the oldest part -of the present land was formed. Again, in this gravel we sometimes find -pieces of sandstone, and of other compound rocks, by which we are of -course carried back a step farther, so as to reach a system of things, -from which the present is the third in succession; and this may be -considered as the most ancient epocha, of which any memorial exists in -the records of the fossil kingdom. - -121. Next in the order of time to the consolidation of the primary -strata, we must place their elevation, when, from being horizontal, and -at the bottom of the sea, they were broken, set on edge, and raised to -the surface. It is even probable, as formerly observed, that to this -succeeded a depression of the same strata, and a second elevation, -so that they have twice visited the superior, and twice the inferior -regions. During the second immersion, were formed, first, the great -bodies of pudding-stone, that in so many instances lie immediately -above them; and next were deposited the strata that are strictly -denominated secondary. - -122. The third great event, was the raising up of this compound body of -old and new strata from the bottom of the sea, and forming it into the -dry land, or the continents, as they now exist.[35] Contemporary with -this, we must suppose the injection of melted matter among the strata, -and the consequent formation of the crystallized and unstratified -rocks, namely, the granite, metallic veins, and veins of porphyry and -whinstone. This, however, is to be considered as embracing a period -of great duration; and it must always be recollected, that veins are -found of very different formation; so that when we speak generally, it -is perhaps impossible to state any thing more precise concerning their -antiquity, than that they are posterior to the strata, and that the -veins of whinstone seem to be the most recent of all, as they traverse -every other. - -[Footnote 35: NOTE XXI.] - -123. In the fourth place, with respect to time, we must class the -facts that regard the detritus and waste of the land, and must -carefully distinguish them from the more ancient phenomena of the -mineral kingdom. Here we are to reckon the shaping of all the present -inequalities of the surface; the formation of hills of gravel, and -of what have been called tertiary strata, consisting of loose and -unconsolidated materials; also collections of shells not mineralised, -like those in Turaine; such petrifactions as those contained in the -rock of Gibraltar, on the coast of Dalmatia, and in the caves of -Bayreuth. The bones of land animals found in the soil, such as those -of Siberia, or North America, are probably more recent than any of the -former.[36] - -[Footnote 36: NOTE XXII.] - -124. These phenomena, then, are all so many marks of the lapse of -time, among which the principles of geology enable us to distinguish -a certain order, so that we know some of them to be more, and others -to be less distant, but without being able to ascertain, with any -exactness, the proportion of the immense intervals which separate them. -These intervals admit of no comparison with the astronomical measures -of time; they cannot be expressed by the revolutions of the sun or of -the moon; nor is there any synchronism between the most recent epoch as -of the mineral kingdom, and the most ancient of our ordinary chronology. - -125. On what is now said is grounded another objection to Dr Hutton's -theory, namely, that the high antiquity ascribed by it to the earth, -is inconsistent with that system of chronology which rests on the -authority of the Sacred Writings. This objection would no doubt be of -weight, if the high antiquity in question were not restricted merely to -the globe of the earth, but were also extended to the human race. That -the origin of mankind does not go back beyond six or seven thousand -years, is a position so involved in the narrative of the Mosaic books, -that any thing inconsistent with it, would no doubt stand in opposition -to the testimony of those ancient records. On this subject, however, -geology is silent; and the history of arts and sciences, when traced -as high as any authentic monuments extend, refers the beginnings of -civilization to a date not very different from that which has just been -mentioned, and infinitely within the limits of the most recent of the -epoch as, marked by the physical revolutions of the globe. - -On the other hand, the authority of the Sacred Books seems to be but -little interested in what regards the mere antiquity of the earth -itself; nor does it appear that their language is to be understood -literally concerning the _age_ of that body, any more than concerning -its _figure_ or its _motion_. The theory of Dr Hutton stands here -precisely on the same footing with the system of COPERNICUS; for -there is no reason to suppose, that it was the purpose of revelation -to furnish a standard of geological, any more than of astronomical -science. It is admitted, on all hands, that the Scriptures are not -intended to resolve physical questions, or to explain matters in no -way related to the morality of human actions; and if, in consequence -of this principle, a considerable latitude of interpretation were not -allowed, we should continue at this moment to believe, that the earth -is flat; that the sun moves round the earth; and that the circumference -of a circle is no more than three times its diameter. - -It is but reasonable, therefore, that we should extend to the -geologist the same liberty of speculation, which the astronomer and -mathematician are already in possession of; and this may be done, -by supposing that the chronology of MOSES relates only to the human -race. This liberty is not more necessary to Dr Hutton than to other -theorists. No ingenuity has been able to reconcile the natural history -of the globe with the opinion of its recent origin; and accordingly -the cosmologies of Kirwan and De Luc, though contrived with more -mineralogical skill, are not less forced and unsatisfactory than those -of Burnet and Whiston. - -126. It is impossible to look back on the system which we have thus -endeavoured to illustrate, without being struck with the novelty and -beauty of the views which it sets before us. The very plan and scope -of it distinguish it from all other theories of the earth, and point -it out as a work of great and original invention. The sole object of -such theories has hitherto been, to explain the manner in which the -present laws of the mineral kingdom were first established, or began to -exist, without treating of the manner in which they now proceed, and by -which their continuance is provided for. The authors of these theories -have accordingly gone back to a state of things altogether unlike the -present, and have confined their reasonings, or their fictions, to a -crisis which never has existed but once, and which never can return. -Dr Hutton, on the other hand, has guided his investigation by the -philosophical maxim, _Causam naturalem et assiduam quærimus, non raram -et fortuitam_. His theory, accordingly, presents us with a system of -wise and provident economy, where the same instruments are continually -employed, and where the decay and renovation of fossils being carried -on at the same time in the different regions allotted to them, preserve -in the earth the conditions essential for the support of animal and -vegetable life. We have been long accustomed to admire that beautiful -contrivance in nature, by which the water of the ocean, drawn up in -vapour by the atmosphere, imparts, in its descent, fertility to the -earth, and becomes the great cause of vegetation and of life; but now -we find, that this vapour not only fertilizes, but creates the soil; -prepares it from the solid rock, and, after employing it in the great -operations of the surface, carries it back into the regions where all -its mineral characters are renewed. Thus, the circulation of moisture -through the air, is a prime mover, not only in the annual succession -of the seasons, but in the great geological cycle, by which the waste -and reproduction of entire continents is circumscribed. Perhaps a more -striking view than this, of the wisdom that presides over nature, was -never presented by any philosophical system, nor a greater addition -ever made to our knowledge of final causes. It is an addition which -gives consistency to the rest, by proving, that equal foresight is -exerted in providing for the whole and for the parts, and that no -less a care is taken to maintain the constitution of the earth, than -to preserve the tribes of animals and vegetables which dwell on its -surface. In a word, it is the peculiar excellence of this theory, that -it ascribes to the phenomena of geology an order similar to that which -exists in the provinces of nature with which we are best acquainted; -that it produces seas and continents, not by accident, but by the -operation of regular and uniform causes; that it makes the decay of one -part subservient to the restoration of another, and gives stability to -the whole, not by perpetuating individuals, but by reproducing them in -succession. - -127. Again, in the detail of this theory, and the ample induction on -which it is founded, we meet with many facts and observations, either -entirely new, or hitherto very imperfectly understood. Thus, the veins -which proceed from masses of granite, and penetrate the incumbent -schistus, had either escaped the observation of former mineralogists, -or the importance of the phenomenon had been entirely overlooked. Dr -Hutton has described the appearances with great accuracy, and drawn -from them the most interesting conclusions. At the junction of the -primary and secondary strata, the facts which he has noted had been -observed by others; but no one I think had so fully understood the -language which they speak, or had so clearly perceived the consequences -that necessarily follow from them. He is the first who distinctly -pointed out the characters which distinguish whinstone from lava, and -who explained the true relation that subsists between these substances. -He also discovered the induration of the strata, in contact with veins -of whin, and the charring of the coal in their vicinity. His theory -also enabled him to determine the affinity of whinstone and granite -to one another, and their relation to the other great bodies of the -mineral kingdom. - -To the observations of the same excellent geologist, we are indebted -for the knowledge of the general and important fact, that all the hard -substances of the mineral kingdom, when elevated into the atmosphere, -have a tendency to decay, and are subject to a disintegration -and waste, to which no limit can be set but that of their entire -destruction; that no provision is made on the surface for repairing -this waste, and that there, no new fossil is produced; that the -formation of all the varied scenery which the surface of the earth -exhibits, depends on the operation of causes, the momentary exertions -of which are familiar to us, though we knew not before the effects -which their accumulated action was able to produce. These are facts in -the natural history of the earth, the discovery of which is due to Dr -Hutton; and, should we lay all further speculation aside, and consider -the theory of the earth as a work too great to be attempted by man, we -must still regard the phenomena and laws just mentioned, as forming a -solid and valuable addition to our knowledge. - -128. If we would compare this theory with others, as to the invisible -agents which it employs, we must consider, that fire and water are the -two powers which all of them must make use of, so that they can differ -from one another only by the way in which they combine these powers. -In Dr Hutton's system, water is first employed to deposit and arrange, -and then fire to consolidate, mineralize, and lastly, to elevate -the strata; but with respect to the unstratified or crystallized -substances, the action of fire only is recognised. The system having -least affinity to this is the Neptunian, which ascribes the formation -of all minerals to the action of water alone, and extends this -hypothesis even to the unstratified rocks. Here, therefore, the action -of fire is entirely excluded; and the Neptunists have certainly made a -great sacrifice to the love of truth, or of paradox, in rejecting the -assistance of so powerful an auxiliary.[37] - -[Footnote 37: NOTE XXIII.] - -129. In the systems which employ the agency of the latter element, we -are to look for a greater resemblance to that of Dr Hutton, though -many and great marks of distinction are easily perceived. In the -cosmologies, for example, of LEIBNITZ and BUFFON, fire and water are -both employed, as well as in this; but they are employed in a reverse -order. These philosophers introduce the action of fire first, and -then the action of water, which is to invert the order of nature -altogether, as the consolidation of the rocks must be posterior to -their stratification. Indeed, the theory of Buffon is singularly -defective: besides inverting the order of the two great operations -of stratification and consolidation, and of course giving no real -explanation of the latter, it gives no account of the elevation, or -highly inclined position of the strata; it makes no distinction between -stratified and unstratified bodies, nor does it offer any but the most -unsatisfactory explanation of the inequalities of the earth's surface. -This system, therefore, has but a very distant resemblance to the -Huttonian theory.[38] - -[Footnote 38: NOTE XXIV.] - -130. The system of LAZZARO MORO has been remarked as approaching nearer -to this theory than any other; and it is certain, that one very -important principle is common to them both. The theory of the Italian -geologist was chiefly directed to the explanation of the remains of -marine animals, which are found in mountains far from the sea; and it -appears to have been suggested to him by the phenomena of the _Campi -Phlegræi_, and by the production of the new island of _Santorini_ -in the Archipelago. He accordingly supposes, that the islands and -continents have been all raised up, like the above-mentioned island, -from the bottom of the sea, by the force of volcanic fire: that -these fires began to burn under the bottom of the ocean, soon after -the creation of the world, when as yet the ocean covered the whole -earth: that they at first elevated a portion of the land; and in this -primitive land no shells are found, as the original ocean was destitute -of fish. The volcanoes continuing to burn, under the sea, after the -creation of animated nature, the strata that were then raised up by -their action were full of shells and other marine objects; and, from -the violence with which they were elevated, arose the contortions and -inclined position which they frequently possess.[39] - -[Footnote 39: Dé Crostacei, et degli altri Marini Corpi, che si trovano -su' Monti: di Ant. Lazzaro Moro. Venezia. 1740.] - -This system is imperfect, as it makes no peculiar provision for the -consolidation of the strata, which, according to it, as well as the -Neptunian system, must be ascribed to the action, not of fire, but of -water. No account is given of the mineralization of the shells found -in the strata, or of the difference between them and the shells found -loose at the bottom of the sea; and no distinction is made between -stratified and unstratified substances. But, with all this, Lazzaro -Moro has certainly the merit of having perceived, that some other power -than that which deposited the strata, must have been employed for their -elevation, and that they have endured the action of a disturbing force. - -131. From this comparison it appears, that Dr Hutton's theory is -sufficiently distinct, even from the theories which approach to it most -nearly, to merit, in the strictest sense, the appellation of _new_ and -_original_. There are indeed few inventions or discoveries, recorded -in the history of science, to which nearer approaches were not made -before they were fully unfolded. It therefore very well deserves to be -distinguished by a particular name; and, if it behoves us to follow -the analogy observed in the names of the two great systems, which at -present divide the opinions of geologists, we may join Mr Kirwan in -calling this the PLUTONIC SYSTEM. For my own part, I would rather -have it characterized by a less splendid, but juster name, that of the -HUTTONIAN THEORY. - -132. The circumstance, however, which gives to this theory its -peculiar character, and exalts it infinitely above all others, is -the introduction of the principle of pressure, to modify the effects -of heat when applied at the bottom of the sea. This is in fact the -key to the grand enigma of the mineral kingdom, where, while one -set of phenomena indicates the action of fire, another set, equally -remarkable, seems to exclude the possibility of that action, by -presenting us with mineral substances, in such a state as they could -never have been brought into by the operation of the fires we see at -the surface of the earth. These two classes of phenomena are reconciled -together, by admitting the power of compression to confine the volatile -parts of bodies when heat is applied to them, and to force them, -in many instances, to undergo fusion, instead of being calcined or -dissipated by burning or inflammation. In this hypothesis, which some -affect to consider as a principle gratuitously assumed, there appears -to me nothing but a very fair and legitimate generalization of the -properties of heat. Combustion and inflammation are chemical processes, -to which other conditions are required, besides the presence of a high -temperature. The state of the mineral regions makes it reasonable -to presume, that these conditions are wanting in the bowels of the -earth, where, of consequence, we have a right to look for nothing but -expansion and fusion, the only operations which seem essential to -heat, and inseparable from the application of it, in certain degrees, -to certain substances. Though this principle, therefore, had no -countenance from analogy, the admirable simplicity, and the unity, -which it introduces into the phenomena of geology, would sufficiently -justify the application of it to the theory of the earth. - -As another excellence of this theory, I may, perhaps, be allowed to -remark, that it extends its consequences beyond those to which the -author of it has himself adverted, and that it affords, which no -geological theory has yet done, a satisfactory explanation of the -spheroidal figure of the earth.[40] - -[Footnote 40: NOTE XXV.] - -133. Yet, with all these circumstances of originality, grandeur, -and simplicity in its favour, with the addition of evidence as -demonstrative as the nature of the subject will admit, this theory -has probably many obstacles to overcome, before it meet the general -approbation. The greatness of the objects which it sets before us, -alarms the imagination; the powers which it supposes to be lodged -in the subterraneous regions; a heat which has subdued the most -refractory rocks, and has melted beds of marble and quartz; an -expansive force, which has folded up, or broken the strata, and raised -whole continents from the bottom of the sea; these are things with -which, however certainly they may be proved, the mind cannot soon -be familiarized. The change and movement also, which this theory -ascribes to all that the senses declare to be most unalterable, raise -up against it the same prejudices which formerly opposed the belief -in the true system of the world; and it affords a curious proof, how -little such prejudices are subject to vary, that as Aristarchus, an -ancient follower of that system, was charged with impiety for moving -the everlasting Vesta from her place, so Dr Hutton, nearly on the same -ground, has been subjected to the very same accusation. Even the length -of time which this theory regards as necessary to the revolutions of -the globe, is looked on as belonging to the marvellous; and man, who -finds himself constrained by the want of time, or of space, in almost -all his undertakings, forgets, that in these, if in any thing, the -riches of nature reject all limitation.[41] - -[Footnote 41: NOTE XXVI.] - -The evidence which must be opposed to all these causes of incredulity, -cannot be fully understood without much study and attention. It -requires not only a careful examination of particular instances, but -comprehensive views of the whole phenomena of geology; the comparison -of things very remote with one another; the interpretation of the -_obscure_ by the _luminous_, and of the _doubtful_ by the _decisive_ -appearances. The geologist must not content himself with examining -the insulated specimens of his cabinet, or with pursuing the nice -subtleties of mineralogical arrangement; he must study the relations of -fossils, as they actually exist; he must follow nature into her wildest -and most inaccessible abodes; and must select, for the places of his -observations, those points, from which the variety and gradation of her -works can be most extensively and accurately explored. Without such an -exact and comprehensive survey, his mind will hardly be prepared to -relish the true theory of the earth. "_Naturæ enim vis atque majestas -omnibus momentis fide caret, si quis modo partes atque non totam -complectatur animo_".[42] - -[Footnote 42: PLIN. Hist. Nat. lib. vii. Cap. i.] - -134. If indeed this theory of the earth is as well founded as we -suppose it to be, the lapse of time must necessarily remove all -objections to it, and the progress of science will only develope its -evidence more fully. As it stands at present, though true, it must be -still imperfect; and it cannot be doubted, that the great principles -of it, though established on an immoveable basis, must yet undergo -many modifications, requiring to be limited, in one place, or to be -extended, in another. A work of such variety and extent cannot be -carried to perfection by the efforts of an individual. Ages may be -required to fill up the bold outline which Dr Hutton has traced with so -masterly a hand; to detach the parts more completely from the general -mass; to adjust the size and position of the subordinate members; and -to give to the whole piece the exact proportion and true colouring of -nature. - -This, however, in length of time, may be expected from the advancement -of science, and from the mutual assistance which parts of knowledge, -seemingly the most remote, often afford to one another. Not only -may the observations of the mineralogist, in tracts yet unexplored, -complete the enumeration of geological facts; and the experiments of -the chemist, on substances not yet subjected to his analysis, afford a -more intimate acquaintance with the nature of fossils, and a measure -of the power of those chemical agents to which this theory ascribes -such vast effects: but also, from other sciences, less directly -connected with the natural history of the earth, much information may -be received. The accurate geographical maps and surveys which are now -making; the foundings; the obsevations of currents; the barometrical -measurements, may all combine to ascertain the reality, and to fix the -quantity of those changes which terrestrial bodies continually undergo. -Every new improvement in science affords the means of delineating more -accurately the face of nature as it now exists, and of transmitting, to -future ages, an account, which may be compared with the face of nature -as it shall then exist. If, therefore, the science of the present times -is destined to survive the physical revolutions of the globe, the -HUTTONIAN THEORY may be confirmed by historical record; and the author -of it will be remembered among the illustrious few, whose systems -have been verified by the observations of succeeding ages, supported -by facts unknown to themselves, and established by the decisions of a -tribunal, slow, but infallible, in distinguishing between truth and -falsehood. - - - ==================================== - - NOTES AND ADDITIONS. - - ==================================== - - - - - NOTES AND ADDITIONS. - - - - - NOTE I. § 2. - - _Origin of calcareous rocks._ - - -135. IT has been asserted, that Dr Hutton went farther than is stated -at § 2, and maintained all calcareous matter to be _originally_ of -animal formation. This position, however, is so far from being laid -down by Dr Hutton, that it belongs to an inquiry which he carefully -avoided to enter on, as being altogether beyond the limits of -philosophical investigation. - -He has indeed no where treated of the _first origin_ of any of the -earths, or of any substance whatsoever, but only of the transformations -which bodies have undergone since the present laws of nature were -established. He considered this last as all that a science, built on -experiment and observation, can possibly extend to; and willingly left, -to more presumptuous inquirers, the task of carrying their reasonings -beyond the boundaries of nature, and of unfolding the properties of -the chaotic fluid, with as much minuteness of detail, as if they were -describing the circumstances of a chemical process which they had -actually witnessed. - -The idea of calcareous matter which really belongs to the Huttonian -Theory, is, that in all the changes which the terraqueous globe has -undergone in past ages, this matter existed, as it does now, either -in the form of limestone and marble, or in the composition of other -stones, or in the state of corals, shells, and bones of animals. It may -be true, that there is no particle of calcareous matter, at present -existing on the surface of the earth, that has not, at some time, made -a part of an animal body; but of this we can have no certainty, nor is -it of any importance that we should. It is enough to know, that the -rocks of marble and limestone contain in general marks of having been -formed from materials collected at the bottom of the sea; and of this -a single cockle-shell, or piece of coral, found included in a rock, is -a sufficient proof with respect to the whole mass of which it makes a -part. - -The principal object which Dr Hutton had in view when he spoke of the -masses of marble and limestone, as composed of the calcareous matter -of marine bodies,[43] was to prove, that they had been all formed -at the bottom of the sea, and from materials there deposited. His -general conclusion is, "That all the strata of the earth, not only -those consisting of such calcareous masses, but others superincumbent -upon these, have had their origin at the bottom of the sea, by the -collection of sand and gravel, of shells, of coralline and crustaceous -bodies, and of earths and clays variously mixed, or separated and -accumulated. This is a general conclusion, well authenticated by the -appearances of nature, and highly important in the natural history of -the earth."[44] - -[Footnote 43: Theory of the Earth, vol. i. p. 23, 24.] - -[Footnote 44: Theory of the Earth, vol. i. p. 26.] - -136. In his Geological Essays, Mr Kirwan says, that "some geologists, -as Buffon, and of late Dr Hutton, have excluded calcareous earth from -the number of the primeval, asserting the masses of it we at present -behold to proceed from shell-fish. But, in addition to the unfounded -supposition, that shell-fish, or any animals, possess the power of -producing any simple earth, these philosophers should have considered, -that, before the existence of any fish, the stony masses that inclose -the bason of the sea, must have existed; and, among these, there is -none in which calcareous earth is not found. Dr Hutton endeavours to -_evade_ this argument, by supposing the world we now inhabit to have -arisen from the ruins and fragments of an anterior, without pointing -at any original. If we are thus to proceed _in infinitum_, I shall not -pretend to follow him; but, if he stops any where, he will find the -same argument equally to occur."[45] - -[Footnote 45: Geol. Essays, p. 13.] - -The argument here employed would certainly be conclusive against any -one, who, in disputing about the _first origin_ of things, should deny -that the calcareous is as ancient as any other of the simple earths. -But this has nothing to do with Dr Hutton's speculations, which, as has -been just said, never extended to the _first origin_ of substances, -but were confined entirely to their changes; so that what he asserts -concerning the calcareous rocks, is no more than that those which we -now see have been formed from loose materials, deposited at the bottom -of the sea. It was not therefore in order to _evade_ Mr Kirwan's -argument, as the preceding passage would lead us to believe, that he -supposed the world which we now inhabit to have arisen from the ruin -and waste of an anterior world; but it was because this seemed to him -a conclusion which necessarily followed from the phenomena of geology, -and it was a conclusion that he had deduced long before he heard of Mr -Kirwan's objections to his system. Instead of an _evasion_, therefore, -any one who considers the subject fairly, will see, in Dr Hutton's -reasoning, nothing but the caution of a philosopher, who wisely -confines his theory within the same limits by which nature has confined -his experience and observation. - -It is nevertheless true, that Dr Hutton has sometimes expressed himself -as if he thought that the present calcareous rocks are all composed of -animal remains.[46] This conclusion, however, is more general than the -facts warrant; and, from some incorrectness or ambiguity of language, -is certainly more general than he intended. The idea of calcareous -rocks, on which he argues throughout his whole theory, is precisely -that which is stated in the preceding article. - -[Footnote 46: Theory of the Earth, vol. i. p. 23.] - - - - - NOTE II. § 6. - - _Origin of coal._ - - -137. The vegetable origin of coal seems to be sufficiently proved by -the reasoning in § 5. and 6.; and that reasoning will appear still -more satisfactory, from what is said at § 28. and 29., concerning the -consolidation of this fossil. Dr Hutton has treated both of the matter -of coal and of its consolidation. Part. I. Chap. 8., of his Theory of -the Earth [47]. - -[Footnote 47: Vol. i. p. 558, &c.] - -The notion, however, that coal is of vegetable origin, is not peculiar -to this theory, but has been for some time the prevailing opinion. -Buffon supposes this mineral to be formed from vegetable and animal -substances, the oil and fat of which have been converted into bitumen -by the action of acids.[48] A fundamental mistake, however, is -committed by this author, and by M. GENSANNE, (author of the natural -history of Languedoc,) on whose observations he greatly relies, in -considering coal as consisting of bitumen united to earth, thus -omitting the only ingredient essential to coal, namely the carbon or -charcoal. This may truly be considered as the essential part, because -coal may exist without bitumen, as in the instance of blind coal, but -not without charcoal. - -[Footnote 48: Hist. Nat. des Mineraux. tom. i. p. 429, 4to edit.] - -Another theory of coal, very analogous to Dr Hutton's, is that of -ARDUINO, professor of mineralogy at Venice, in which he supposes it -formed from vegetable and animal remains from the land and sea, but -chiefly from the latter.[49] This theory of coal is contained in Dr -Hutton's, in which the animal and vegetable remains must be supposed -to come both from the earth and the sea. It seems to be without any -good reason that Arduino considers the sea as the chief source of these -materials. His remarks, however, are very ingenious, and deserving of -attention. - -[Footnote 49: Saggio Fisico-mineralogico del Sig. Giov. Arduino; Atti -di Siena, tom. v. p. 228, 281, &c.] - -These accounts of the origin of coal are all nearly the same; it is -in what relates to the distinction between the common coal, in which -there is no ligneous structure, and those varieties of it in which that -structure is apparent, and again in explaining the consolidation of -both, that the theory laid down here is peculiar. - -138. Some other mineralogists refer one of the ingredients of coal -to the vegetable kingdom, but not the other. Unable to resist the -conviction which arises from the fibrous structure of parts of strata, -and even entire strata of coal, they have supposed, that wood, which -had been somehow buried in the earth, or perhaps deposited at the -bottom of the sea, had become impregnated with bitumen, which last, -however, they consider as of mineral origin. This appears to be the -opinion of Lehman; and also of some very late writers. There seems, -however, to be hardly less reason for referring the origin of one part -of coal to the vegetable or animal kingdom than another. The two last -are certainly capable of furnishing both the carbonic and bituminous -parts; and therefore, to derive these from different sources, is at -least a very unnecessary complication of hypotheses. - -139. Another explanation of coal, very different from any of the -preceding, has lately been advanced and set up in opposition to the -Huttonian Theory. Mr Kirwan,[50] the only mineralogist, I believe, who -has attempted to derive both the carbonic and bituminous matter of coal -from the mineral kingdom, distinguishes between wood coal and mineral -coal, and gives a theory entirely new of the formation of the latter. -Wood coal is that in which the ligneous structure is so apparent, as to -leave no doubt of its vegetable origin; mineral coal is that in which -no such structure can be discovered, and is the same which Dr Hutton -derives from the vegetable juices, and other remains, comminuted, -dispersed, carried into the sea, and there precipitated, so as to -unite with different proportions of earth, and to become afterwards -mineralized. - -[Footnote 50: Geol. Essays, essay vii. p. 290.] - -These two species of coal, which the Huttonian theory considers as -gradations of the same substance, Mr Kirwan regards as perfectly -distinct, constituting two minerals, of an origin and formation -entirely different. He therefore endeavours to ascertain the -distinguishing characters of each, considered geologically. - -140. But here the leading distinction, implied in all the rest, that -the two kinds of coal are never found in the same bed, but always in -different situations, and with different laws of stratification, is -expressly contradicted by matter of fact. Coal, as is said above, with -its ligneous texture quite apparent, and coal with no such structure -visible, are often found in the same seam, are brought up from the same -mine, and united in the same specimen. I have a specimen from a bed of -coal, in the Isle of Sky, found under a basaltic rock, consisting of a -ligneous part, which graduates into one in which there is no vestige -of a fibrous texture, and in which the surface is smooth and glossy, -with a fracture almost vitreous. The upper part of the specimen is -therefore perfect wood coal, and the under part perfect mineral-coal, -in the language of Mr Kirwan; at the same time that the transition from -the one to the other is made by insensible degrees. This specimen, -were it perfectly solitary, is sufficient to prove the identity -of the two species of coal we are now speaking of, and to show, -that the difference between them is accidental, not essential. The -specimen, however, is far from being solitary; the number of similar -appearances is so great, as hardly to have escaped the observation -of any mineralogist. Mr Kirwan admits, that wood coal is often found -under basaltes;[51] but what is essential to be remarked is, that, in -this instance, we have both the wood coal and the common mineral-coal, -lying under that rock, and the one passing gradually into the other It -appears, indeed, that many of the facts which Mr Kirwan produces, in -treating of what he calls _carboniferous_ soils, are quite inconsistent -with the distinction he would make between wood-coal and mineral -coal.[52] - -[Footnote 51: Geol. Essays, p. 310.] - -[Footnote 52: _Ibid._ p. 311.] - -141. It is, however, true, that there are instances in which the wood -coal, or fossil wood, as it is usually called, forms entire beds, quite -unconnected with the ordinary coal, and stratified in some respects -differently. Such is the Bovey coal in Devonshire, the wood-coal in the -north of Ireland, and perhaps the Surturbrandt of Iceland. With respect -to the Bovey coal, it does by no means answer to one of Mr Kirwan's -remarks, viz. that late observations have ascertained, that no such -parallelism of the beds, as in mineral coal, nor even any distinct -number of strata is found. In the Bovey coal, the number of strata is -very well defined, by beds of clay regularly interposed; but as to the -extent of these beds, the coal having been worked only at one place, -and by an open pit, without any extensive subterraneous excavation, -nothing is known with certainty. - -In the Bovey coal too, I must observe, though its beds have the -ligneous structure very distinct, the clay interposed between these -beds, which is but little indurated, contains a great deal of coaly -matter, in the form of thin flakes, interspersed through it. So far as -I know, there are no mineral reins nor shifts, nor any bed of indurated -stone, that accompany this coal; so that, though one can not doubt of -its vegetable origin, some doubt may be entertained concerning the -nature of the mineralizing operations, to which it has been subjected -The consideration of these, however, does not belong to the present -argument; and the peculiarities of this semi-mineralized coal, as it -may be called, have nothing to do with the general question, whether -wood coal and mineral coal are the same substance; about which -question, if the gradations are properly considered, I think, no -reasonable doubt can remain. - -142. One of Mr Kirwan's objections to the vegetable origin of coal, -is founded on this fact, that there is, in the museum at Florence, a -cellular sandstone, the cells of which are filled with genuine mineral -coal. "Could this (adds he) have been originally wood?"[53] The answer -to the interrogatory proposed here as a _reductio ad absurdum_, is, -that most undoubtedly it may have been wood. Sandstone with charred -wood, that is, with wood coal in it, is not an uncommon phenomenon in -coal countries. I have seen a specimen of this kind from the Hales -Quarry, near Edinburgh, consisting of a piece of charred wood, imbedded -in sandstone; the wood was much altered, but the remains of its fibrous -structure were distinctly visible. This affords a perfect commentary on -the specimen in the Florence cabinet. - -[Footnote 53: Geol. Essays, p. 321.] - -143. If then it be granted, as I think it must, that the two kinds of -coal we have been speaking of are of the same origin, it is not very -necessary to enter on a refutation of Mr Kirwan's theory with respect -to either of them. His account of the formation of mineral coal, -however, is so singular, that it cannot be passed over without remark. - -Mr Kirwan supposes, 1mo, That natural carbon was originally contained -in many mountains of the granite and porphyritic order, and also in -siliceous schistus; and might, by disintegration and decomposition, be -separated from the stony particles. 2do, That both petrol and carbon -are often contained in trap, since hornblende, which has lately been -found to contain carbon, very frequently enters into its composition. - -"My opinion (adds he) is, that coal mines, or strata of coal, as well -as the mountains in which they are found, owe their origin to the -disintegration of primeval mountains, either now totally destroyed, -or whose height and bulk, in consequence of such disintegration, are -considerably lessened; and that these rocks, anciently destroyed, -contained most probably a far larger proportion of carbon and -petrol than those of the same denomination now contain, since their -disintegration took place at so early a period.[54] - -[Footnote 54: Geol. Essays, p. 328, &c.] - -"By the decomposition of these mountains, the feldspar and hornblende -were converted into clay; the bituminous particles, thus set free, -reunited, and were absorbed, partly by the argil, but chiefly by the -carbonaceous matter, with which they have the greatest affinity. The -carbonic and bituminous particles, thus united, being difficultly -miscible with water, and specifically heavier, sunk through the moist, -pulpy, incoherent argillaceous masses, and formed the lowest stratum," -&c. - -Such is Mr Kirwan's theory of the formation of coal, and nobody I think -will dispute the originality of it. - -144. To enter on a formal refutation of an opinion so loaded with -objections, would be a task as irksome as unnecessary. A few -observations will suffice. - -The notion of the great degradation of mountains, involved in this -hypothesis, is the part of it to which I am least disposed to object. -But I cannot help reminding Mr Kirwan, that the effects of waste are -not supposed less in this, than in Dr Hutton's theory; and that he has -assumed the very principle, of which that theory makes so much use, -though he has reserved to himself, as it should seem, the right of -denying it, when it does not accord with his system. It is indeed worth -while to compare what is said concerning the degradation of mountains, -in the above quotations, and still more fully in the book itself, with -what is advanced concerning their indestructibility, in another passage -of the same volume:[55] - -[Footnote 55: Page 436.] - -"All mountains are not subject to decay; for instance, scarce any of -those that consist of red granite. The stone of which the Runic rocks -are formed, have withstood decomposition for two thousand years, as -their characters evince," &c. - -"Basaltic pillars, in general, bid defiance to decay," &c. He goes on -to deny every step of the degradation of land, by which it is wasted, -carried into the sea, and spread out over its bottom, though all these -are necessary _postulata_ in his theory of the formation of coal. One -can be at no loss about estimating the value of a system, in which such -gross inconsistencies make a necessary part. - -145. The quantity of hornblende and siliceous schistus, necessary to -be decomposed, in order to produce the coal strata presently existing, -is enormous, and would lead to an estimate of what is worn away from -the primeval mountains, far exceeding any thing that Dr Hutton has -supposed. It is true, that Mr Kirwan, never at all embarrassed about -preserving a similitude between nature as she is now, and as she was -heretofore, lays it down, that the part of the primeval mountains -which is worn away, contained much more carbon than the part which is -left behind. This, however, is an arbitrary supposition; and since, in -this system, such suppositions are so easily admitted, why may we not -conceive, in the primeval mountains, a more copious source of carbonic -matter than hornblende or siliceous schistus? We have but to imagine, -that the _diamond_ existed among these mountains in such abundance, as -to constitute large rocks. This stone being made up of pure, or highly -concentrated carbon, the adamantine summits of a single ridge, by -their decomposition, might afford a carbonic basis, sufficient for the -coal beds of all the surrounding plains. - -146. We may also object to Mr Kirwan, that the siliceous part of -the mountains has not been chemically dissolved; it has been only -abraded and worn away. Mechanical action has reduced the quartz to -gravel and sand, but has not produced on it any chemical change. -The carbon, therefore, could not be let loose. Experiment, indeed, -might be employed, to determine whether the siliceous matter of the -secondary, and of the primary strata contains this substance in the -same proportion. - -Again, a more fatal symptom can hardly be imagined in any theory, than -that, when the circumstances of the phenomena to be explained are _a -little_ changed, the theory is under the necessity of changing _a -great deal_. Now, this is what happens to Mr Kirwan's theory, in the -attempt made to explain by it the stratum of coal described in the -_Annales de Chimie_,[56] as cutting a mountain of argillaceous strata -in two, at about three-fourths of its height. This stratum, Mr Kirwan -says, must have been formed by _transudation_ from the superior part -of the mountain,[57] Besides that this is a gratuitous supposition -of a thing, without example, it involves in it an absurdity, which -becomes evident the moment the question is asked, What occupied the -place of the coal-bed before the transudation from the upper part of -the mountain? Has the _liquid coal_, as it percolated through the upper -strata, expelled any substance from the place it now occupies? or has -it been powerful enough to raise up, or to float, as it were, the upper -part of the mountain? - -[Footnote 56: Tom. xi. p. 272.] - -[Footnote 57: Geol. Essays, p. 338.] - -The situation of this bed of coal is not singular, and its formation -is easily explained on Dr Hutton's theory. It is part of a stratum of -coal, which has been deposited, like all others, at the bottom of the -sea; from whence certain causes, of very general operation, have raised -it up, together with the attending strata: these strata have since -been all cut down, and worn away by the operations of the surface; and -the mountain, with the coal stratum in the middle of it, is a part -of them which has been left behind. There is no wonder, that a coal -stratum should be found alternating with others, in a mountain, any -more than in the bowels of the earth, and no more need of a separate -explanation.[58] - -[Footnote 58: This stratum of coal, which is described by HASSENFRATZ, -is remarkable for being in a mountain which rests immediately on -primary schistus and granite.] - -147. After all, it may be asked, for what purpose is it that so -many incongruous and ill supported hypotheses are thus piled on one -another? is it only to avoid ascribing the carbonic and bituminous -matter of coal to a substance in which we know with certainty that such -matter resides in great abundance, in order to derive it from other -substances, in which a subtle analysis has shown, that it exists in a -very small proportion? Such reasoning is so great a trespass on every -principle of common sense, not to say of sound philosophy, that, to -bestow any time on the refutation of it, is, in some degree, to fall -under the same censure. - - - - - NOTE III. § 7. - - _Primitive mountains._ - - -148. The enumeration of the different kinds of primary schistus, at -§ 7, is not proposed as at all complete. It will be less defective, -however, if we add to it _talcose schistus_, and _lapis ollaris_ or -_potstone_.[59] - -[Footnote 59: Kirwan's Mineralogy, vol. i. p. 155.] - -149. The rocks called here by the name of primary, were first -distinguished, as forming the basis of all the great chains of -mountains, and as constituting a separate division of the mineral -kingdom, by J. G. LEHMAN, director of the Prussian mines. See his -work, intituled, _Essai d'une Histoire Naturelle des Couches de la -Terre_.[60] These rocks were regarded by Lehman as parts of the -original nucleus of the globe, which had undergone no alteration, but -remained now such as they were at first created; and, agreeably to -this supposition, he bestowed on them, and on the mountains composed -of them, the name of primitive. He remarks, nevertheless, their -distribution into beds, either perpendicular to the horizon, or highly -inclined, and the super-position of the secondary and horizontal -strata. However mineralogists may now differ in their theories from -Lehman, they must consider this distinction as a great step in the -science of geology, and very material to the right arrangement of the -natural history of the earth. - -[Footnote 60: Tom. iii. p. 239, &c. The French translation is in 1759, -but the original preface is dated at Berlin, 1756.] - -150. Several mineralogists have agreed with him in the supposition, -that these rocks are a part of the original structure of the globe, and -prior to all organized matter. Of this number is PALLAS;[61] and also -DE LUC, who applies the term _primordial_ to the rocks in question, -and considers them as neither stratified nor formed by water.[62] -In his subsequent writings, however, he admits their formation from -aqueous deposition, as the Neptunists do in general, but holds them to -be more ancient than organized bodies. - -[Footnote 61: Observations sur la Formation des Montagnes.] - -[Footnote 62: Lettres Phys. Sur l'Histoire de la Terre, tom. ii. p. -206.] - -151. PINI, professor of natural history at Milan, has denied the -stratification of primitive mountains, in a memoir on the mineralogy -of St Gothard, and in another on the revolutions of the globe.[63] -His reasonings are opposed by SAUSSURE,[64] and are certainly, in -many respects, very open to attack. They proceed on a comparison -between the division of rocks, by what is called the planes of their -stratification, and their division by transverse fissures: two -things, which he thinks so much alike, that they ought not to be -referred to different causes; and, as the one cannot be regarded as -the effect of aqueous deposition, so neither should the other. This -is a very fallacious argument, because it confounds two things that -are essentially different; and, instead of inquiring about a matter -of fact, inquires about its cause. The truth is, that the dispute has -arisen from not distinguishing the granite from the schistus mountains, -and from involving both under the name of primitive. M. Pini seems -to be in the right, when he holds the granite of St Gothard to be -unstratified; but it is without any good reason, that he would extend -the same conclusion to the schistus of that mountain. CHARPENTIER, and -Saussure, in his last two volumes, contend even for the stratification -of granite.[65] - -[Footnote 63: Memoria sulle Rivoluzioni del Globo Terrestre; Memorie -della Societa Italiana, tom. v. p. 222, &c.] - -[Footnote 64: Voyages aux Alpes, tom. iv. § 1881.] - -[Footnote 65: See NOTE XV. on Granite.] - -As the consent, if not universal, is very general for the -stratification of the primary schistus, and the fact itself abundantly -obvious, in almost all the instances I have ever met with, I have not -considered it as necessary to enter here into any argument on this -subject. - - - - - NOTE IV. § 8. - - _Primary strata not primitive._ - - -152. An account of the facts referred to § 8, may be found in Hutton's -Theory, vol. i. p. 332, &c. To what is there said, of the shells -contained in the primary limestone of Cumberland, I must add, that -I have since had an opportunity of verifying the conjecture, that -the limestone rock, in which the shells were found, near the head of -_Coniston_ Lake, is part of the same body of strata, where shells were -found, in a quarry between Ambleside and Low-wood. The limestone of -that quarry contains several marine objects; it is in strata declining -about 10° from the perpendicular, toward the S. E., and forms a belt, -stretching across the country from N. E. to S. W. - -In a quarry where the argillaceous schistus, on the south side of this -limestone belt, is worked for pavement, are impressions of what I think -may safely be accounted marine objects; they have the form of shells, -are much indurated, and full of pyrites. They seem to be of the same -kind with the impressions said to be found in a slate quarry, near the -village of Mat in Switzerland.[66] - -[Footnote 66: Hutton's Theory, vol. i. p. 327.] - -Another spot, affording instances of shells in primary limestone, is -in Devonshire. On the sea shore on the east side of Plymouth Dock, -opposite to Stonehouse, I found a specimen of schistose micaceous -limestone, containing a shell of the bivalve kind: it was struck -off from the solid rock, and cannot possibly be considered as an -adventitious fossil. - -Now, no rocks can be more decided primary than those about Plymouth. -They consist of calcareous strata, in the form either of marble or -micaceous limestone, alternating with varieties of the same schistus, -which prevails through Cornwall to the west, and extends eastward into -Dartmoor, and on the sea-coast, as far as the Berry-head. These all -intersect the horizontal plane, in a line from east to west nearly; -they are very erect, those at Plymouth being elevated to the north. - -Though, therefore, the remains of marine animals are not frequent among -the primary rocks, they are not excluded from them; and hence the -existence of shell-fish and zoophytes, is clearly proved to be anterior -to the formation even of those parts of the present land which are -justly accounted the most ancient. - -153. The rocks which contain sand or gravel, which are of a granulated -texture, must also be considered as carrying in themselves a testimony -of the most unequivocal kind, of their being derived from the -_detritus_ and waste of former rocks. Now, the fact stated in the text, -concerning sand found in schistus, most justly accounted primary, -might be exemplified by actual reference to many spots on the earth's -surface. A few such will be sufficient in this place. - -St Gothard is a central point, in one of the greatest tracts of primary -mountains on the face of the earth, yet arenaceous strata are found in -its vicinity. Between Ayrolo and the Hospice of St Gothard, Saussure -found a rock, composed of an arenaceous or granular paste, including in -it hornblende and garnets. He is somewhat unwilling to give the name -_gres_ to this stone, which M. Besson had done; but he nevertheless -describes it as having a granulated structure.[67] - -[Footnote 67: Voyages aux Alpes, tom. iv. § 1822.] - -Among the most indurated rocks that compose the mountains of this -island, many are arenaceous. Thus, on the western coast of Scotland, -the great body of high and rugged mountains on the shores of Arafaig, -&c. from Ardnamurchan to Glenelg, consists, in a great measure, of a -granitic sandstone, in vertical beds. This stone sometimes occupies -great tracts; at other times it is alternated with the micaceous, or -other varieties of primary schistus; it occurs, likewise, in several of -the islands, and is a fossil which we hardly find described or named -by the writers on mineralogy. Much, also, of a highly indurated, -but granulated quartz, is found in several places in Scotland, in -beds or strata, alternated with the common schistus of the mountains. -Remarkable instances of this may be seen on the north side of the ferry -of Balachulish, and again on the sea-shore at Cullen. At the latter, -the strata are remarkably regular, alternating with different species -of schistus. At the former, the quartz is so pure, that the stone has -been mistaken for marble. - -These examples are perhaps sufficient; but I must add, that in the -micaceous and talcose schisti themselves, thin layers of sand are -often found, interposed between the layers of mica or talc. I have -a specimen, from the summit of one of the highest of the Grampian -mountains, where the thin plates, of a talcky or asbestine substance, -are separated by layers of a very fine quartzy sand, not much -consolidated. - -The mountain from which it was brought, consists of vertical strata, -much intersected by quartz veins. It is impossible to doubt, in this -instance, that the thin plates of the one substance, and the small -grains of the other, were deposited together at the bottom of the sea, -and that they were alike produced from the degradation of rocks, more -ancient than any which now exist. - -154. In the Neptunian system, as improved by WERNER, an attempt is made -to take off the force of such instances as are produced in § 8, 9, and -152, &c. by distinguishing rocks, as to their formation, into three -different orders, the primitive, the intermediate, and the secondary, -or, to speak more properly, into primary, secondary, and tertiary. The -same mineralogist distinguishes, among the materials of these rocks, -between what he terms chemical and mechanical deposits. By mechanical -deposits, are understood sand, gravel, and whatever bears the mark of -fracture and attrition; by chemical deposits, those which are regularly -crystallized, or which have a tendency to crystallization, and in which -the action of mechanical causes cannot be traced. This distinction -is founded in nature, and proceeds on real and palpable differences; -but the application made of it to the three kinds of strata just -enumerated, seems by no means entitled to the same praise. - -The primitive rocks contain, it is said, none but chemical deposits, -and are entirely composed of them: the intermediate contain a mixture -of both, and also some vestiges of organized bodies: the secondary -consist almost entirely of the mechanical, or of the remains of such -bodies, with little of the chemical. The first of these, then, are held -to contain no mark or vestige whatsoever of any thing more ancient -than themselves, and are, in the strictest sense, primeval, or formed -of the first materials, deposited by the immense ocean which originally -encompassed the globe. - -After them were formed the intermediate, mostly consisting of chemical -deposits, but containing also some animal remains, and some spoils from -the land, subjected to the various kinds of destruction, which even -then made a part of the order of nature. These rocks, it is alleged, -are chiefly argillaceous, are less indurated than the primary, and not -intersected by veins of quartz. - -The secondary were formed from the remains of the other two, and -contain more mechanical deposits than any other. - -This sketch of what I understand to be Werner's opinion concerning the -different formation of the strata, is chiefly taken from a view of his -system, in the _Journal de Physique_ for 1800. - -155. The main objection to the distinction here made between the -primary and the intermediate strata, is founded on the facts that -have been just stated. The sandstone of St Gothard is from a country -having every character of a primary one in the highest perfection. The -instances I have mentioned from the Highlands of Scotland, are from -mountains, less elevated indeed than the Alps, but where the rock is -micaceous, talcose, or siliceous, in planes erect to the horizon, and -intersected by veins' of quartz. The shells from Plymouth are from a -rock, that Werner would, I think, admit to be truly primitive. Those -from the lakes, also, are from the centre of a country, occupied by -porphyry, schorl, hornstone-schistus, and many others, about the order -of which there can be no dispute. It is true, that in this tract -there are argillaceous strata, of the kind that might be accounted -intermediate, were they not interposed among those that are certainly -primary; and this very intermixture shows, how little foundation there -is for the distinction attempted to be made between the formation of -the one and of the other. If there is any principle in mineralogy, -which may be considered as perfectly ascertained, it is, that rocks -similarly stratified, and alternated with one another, are of the same -formation. - -Hence we conclude, that there is _no order of strata yet known_, that -does not contain proofs of the existence of more ancient strata. We see -nothing, in the strict sense, primitive. It must be understood, that -what is here said has no reference to granite, which I do not consider -as a stratified rock, and in which neither the remains of organized -bodies, nor sand, have I believe been ever found; though some -instances will be hereafter mentioned, where granite contains fragments -of other stone, viz. of different kinds of primary schistus. - -To the instances of sand involved in primary schistus, I might have -added many from the rocks of that order on the coast of Berwickshire, -of which mention is so often made in these Illustrations; but I wished -to draw the evidence from those rocks that are most unequivocally -primary, and to which the Wernerian distinction of _intermediate_ could -not possibly be applied. - -If any one assert, as M. De Luc has done, that sand is a chemical -deposit, a certain mode of crystallization which quartz sometimes -assumes, let him draw the line which separates sand from gravel; and -let him explain why quartz, in the form of sand, is not found in -mineral veins, in granite, nor in basaltes, that is, in none of the -situations where the appearances of crystallization are most general -and best ascertained. - - - - - NOTE V. § 10. - - _Transportation of the - materials of the strata._ - - -156. The great transportation or _travelling_ of the materials of the -strata, supposed by Dr Hutton, has been treated as absurd by some -of his opponents, particularly De Luc and Kirwan. These philosophers -seem not to have observed, that their own system, and indeed every -system which derives the secondary strata from the primary, involves -a transportation of materials, hardly less than is supposed in the -Huttonian theory, and a degradation of the primeval mountains, in -many instances much greater. To form some notion of this degradation, -it must be recollected, that the primeval mountains, which furnished -the materials of the secondary strata in the plains, cannot have -stood in the place now occupied by these plains. This is obvious; and -therefore we must necessarily regard the secondary strata as derived -from the primitive mountains which are the nearest to them, and of -which a part still remains. This part is sufficient to define the -base of the original mountains; and the quantity of the secondary -strata which surround them may help us to make some estimate of their -height. Let us take, for instance, the extensive tract of secondary -country about Newcastle, where coal mines have been sunk through a -succession of secondary strata, to the depth of more than a thousand -feet. This secondary country may be considered as comprehending almost -the whole of the counties of Northumberland and Durham, and probably -as extending very far under the part of the German Ocean which washes -their coasts; and the whole strata composing it must be derived, on -the hypothesis we are now considering, from the Cheviot Hills, on one -side, and from those in the high parts of Westmoreland and Cumberland -on the other, comprehending the Alston-Moor Hills, and the large group -of primary mountains, so well known from the sublime and romantic -scenery of the _Lakes_. Now, the mountains which stood on this base, -had not only to supply the materials for the tract already mentioned, -on the east, but had also their contingent to furnish to the plains on -the west and north; the Cheviots to Roxburghshire and Berwickshire; -the Northumberland mountains to the coal strata about Whitehaven, and -along the sea coast to Lancashire. On the whole, we shall not exceed -the truth, if we suppose, that the secondary strata, at the feet of the -above mountains, are six or seven times more extensive than the base -of the mountainous tract. If then we take the medium depth of these -secondary strata to be one thousand feet, it is evident, that the mass -of stone which composes them, if it were placed on the same base with -the primitive mountains, would reach to the height of six thousand -feet. This is supposing the mass to preserve the breadth of its base -uniformly to the summit; but if it be supposed to taper, as mountains -usually do, we must multiply this six thousand by three, in order to -have the height of these primeval mountains, which, therefore, were -originally elevated not less than eighteen thousand feet; in height, -therefore, they once rivalled the Cordilleras, and are now but poorly -represented by the hills of Skidaw and Helvellyn. It were easy to show, -that this estimate is still below the result that strictly follows from -the Neptunian hypothesis; but it is unnecessary to proceed further, -than to prove, that the principle of the degradation of mountains, is -involved in that hypothesis to an excessive and improbable degree; and -that the supporters of it, have either been guilty of the inconsistency -of refusing to Dr Hutton the moderate use of a principle, which they -themselves employ in its utmost extent, or of not having sufficiently -adverted to the consequences of their own system. - -157. The formation of secondary strata from the degradation of the -contiguous mountains, on close examination, is subject to many -other difficulties of the same kind. Mountains of secondary strata, -and nearly horizontal, are found in this island of the height of -three thousand feet. Such are Ingleborough, Wharnside, and perhaps -some others on the west of Yorkshire. The whole chain, indeed, -for secondary mountains, is of great elevation. The strata are of -limestone, and of a very coarse-grained sandstone, alternating with it. -No mountains can more clearly point out, that the strata of which they -consist were once continued quite across the vallies which now separate -them; and hence, if the materials of those strata were indeed furnished -from any contiguous primitive mountains, the latter must have been, out -of all proportion, higher than any mountains now in Britain. - -158. Thus, a great degradation of the primitive mountains, and of -course a great travelling of their materials, is proved to make a -necessary part of the Neptunian theory. The extent of this travelling -or transportation may be rendered more evident, if we apply a similar -mode of reasoning to larger portions of the globe. The north-west of -Europe furnishes us an instance of a very extensive tract of secondary -country, comprehending the greater part of Britain, the whole of -Flanders and Holland, part of Germany, the northern provinces of -France, and probably the bed of the German Ocean, at least for a great -extent. Within this circle almost all is secondary, and on the sides -of it all round are placed ridges or groups of primitive mountains, -namely the mountains of Auvergne, at least in part, and going round by -the east, the Alps, the Vosges, the Hartz, the Highlands and Western -Islands of Scotland, the hilly countries of Cumberland, Wales, and -Cornwall. This zone of primitive mountains, on the supposition of the -Neptunists, must have risen up in the form of islands in the great -ocean, that originally covered the earth, forming a kind of circular -Archipelago, including in its bosom a sea, which was from seven to -five hundred miles in diameter. Over the whole of this extent, the -_detritus_ of the above mountains must have been carried, in order to -form the flat interjacent countries which are now exposed to our view. -Such then, even on their own supposition, is the extent to which the -Neptunists must admit that the materials of the primeval mountains were -transported by the ocean. - -159. This transportation of materials, may not be so great as that -which is involved in Dr Hutton's theory, but is such as should make the -enemies of his system consider, how nearly the principles they _must_ -introduce, agree with those that they _would_ reject. This is one -fact, out of many, which shows, that there is at present a much nearer -agreement between the systems of geology, than between their authors. - -160. To these facts, demonstrating the great transportation of fossils -in some former conditions of the globe, we may add another, recognised -by all mineralogists. The animal exuviæ contained in limestone and -marble, are often known to belong to seas, extremely remote from the -countries where they are now found. In the chalk-beds of England, in -the limestones of France, a great proportion of the petrifactions -belong to the tropical seas, and appear to have been brought from the -vicinity of the equator. Buffon observes, that of the fossil shells -found in France, it has been disputed, whether the foreign are not -more numerous than the native; and, though he is himself of opinion -that they are not, it is evident that they must bear a considerable -proportion to the whole.[68] In the petrifactions of Monte Bolca, near -Verona, where the impressions of fish are preserved between the laminæ -of a calcareous schistus, one hundred and five different species have -been enumerated, of which thirty-nine are from the Asiatic seas, three -from the African, eighteen from those of South, and eleven from those -of North America.[69] Similar observations have been made on the marine -plants, and the impressions of vegetables, found in rocks, in different -parts of Europe. At St Chaumont, near Lyons, is found an argillaceous -schistus, covering a bed of coal, every lamina of which is marked with -the impressions of the stem, leaf, or other part of some plant; and it -happens, says M. FONTENELLE, by an unaccountable destination of nature, -that not one of these plants is a native of France. They are all ferns -of different species, peculiar to the East Indies, or the warmer -climates of America. Here also was found the fruit of a tree, which -grows only on the coasts of Malabar and Coromandel.[70] - -[Footnote 68: Buffon, Théorie de la Terre, art. 8.] - -[Footnote 69: Saussure, Voyages aux Alpes, tom. iii. § 1535.] - -[Footnote 70: Mém. De l'Acad. Des Sciences, 1718, p. 3 and 287; and -1721, p. 89, &c.] - -The same holds of the bodies of amphibious animals which now make a -part of the fossil kingdom. The head and the bones of crocodiles have -been found in the island of Shepey, at the mouth of the Thames; and the -remains of an animal of the same species, but of a variety now peculiar -to the Ganges, have been discovered in the alum rocks on the coast of -Yorkshire.[71] These proofs of the transportation of materials by the -sea, have the advantage of involving nothing hypothetical, and of being -equally addressed to the geologists of every persuasion. - -[Footnote 71: Phil. Trans. vol. l. p. 688. CAMPER denies that the -remains here mentioned belong to the crocodile, or any amphibious -animal, and refers them to the balænaæ. He passes the same judgment on -those fossil bones from St Peter's Mount, near Maestricht, which have -been supposed to belong to the crocodile; he looks on them as belonging -to whales, though of an unknown species. In this Mount, so famous for -its petrifactions, he finds many specimens of bones, which he thinks -belong to the turtle. Phil. Trans. vol lxxvi. p. 443. The opinion of an -author, so well skilled in comparative anatomy, must be regarded as of -great weight: if it takes from our argument in one part, it adds to it -in another, and the acquisition of the turtle makes up abundantly for -the loss of the crocodile.] - -On this subject I cannot help observing, that the accurate comparison -of the animal exuviæ of the mineral kingdom, with their living -archetypes, is not merely a curious inquiry, but is one that may lead -to important consequences, concerning the nature and direction of the -forces which have changed, and are continually changing, the surface of -the earth. - -161. These remarks I have thought it proper to add to the proofs of the -composition of the present from former strata, in order to show, that -the great transportation of materials involved in that supposition, is -not only conformable to the hypothesis of the Neptunists concerning -the secondary strata, but is also proved by the most direct evidence, -independently of all hypothesis. All this reasoning regards the ancient -state of the globe. Whether such a travelling of stony bodies makes -a part of the system now actually carrying on, will be considered in -another place.[72] - -[Footnote 72: See NOTE XIX.] - - - - - - NOTE VI. § 13. - - _Mr Kirwan's notion of precipitation._ - - -162. The Neptunist who has provided the means of dissolving the -materials of the strata, has only performed half his work, and must -find it a task of equal difficulty to force this powerful menstruum -to part with its solution. Mr Kirwan, aware in some degree of this -difficulty, has attempted to obviate it in a very singular way. First, -he ascribes the solution of all substances in water, or in what he -calls the chaotic fluid, to their being finely pulverised, or created -in a state of the most minute division. Next, as to the deposition, the -solvent being, as he acknowledges, very insufficient in quantity, the -precipitation took place, (he says,) on that account the more rapidly. - -If he means by this to say, that a precipitation without solution -would take place the sooner the more inadequate the menstruum was to -dissolve the whole, the proposition may be true; but will be of no -use to explain the crystallization of minerals, (the very object he -has in view,) because to crystallization, it is not a bare subsidence -of particles suspended in a fluid, but it is a passage from chemical -solution to non-solution, or insolubility, that is required. - -If, on the other hand, he means to say, that the solution actually took -place more quickly, and was more immediately followed by precipitation, -because the quantity of the menstruum was insufficient, this is to -assert, that the weaker the cause, the more instantaneous will be its -effect. - -Of two propositions the one of which is nugatory, and the other absurd, -it is not material to inquire which the author had in view. - - - - - NOTE VII. § 16. - - _Compression in the mineral regions._ - - -163. It is worthy of remark, that the effects ascribed to compression -in the Huttonian Theory, very much resemble those which Sir ISAAC -NEWTON supposes to be produced in the sun and the fixed stars by -that same cause. "Are not," says he, "the sun and fixed stars great -earths, vehemently hot, whose heat is conserved by the greatness of -the bodies, and the mutual action and reaction between them, and the -light which they emit; and _whose parts are kept from fuming away, -not only by their fixity, but also by the vast weight and density of -the atmospheres incumbent upon them, and very strongly compressing -them_."[73] - -[Footnote 73: Newton's Optics, Query 11.] - -164. The fact of water boiling at a lower temperature under a less -compression, is sufficient to justify the supposition, that bodies may -be made by pressure to endure extreme heat, without the dissipation -of their parts, that is, without evaporation or combustion. A further -_postulatum_ is introduced in Dr Hutton's theory, namely, that compound -bodies, such as carbonate of lime, when the compression prevents their -separation, may admit of fusion, notwithstanding that the fixed part -may be infusible when separated from the volatile. This assumption is -supported by the analogical fact of the fusion of the carbonate of -barytes, as mentioned in the text. - -165. In a region where the action of heat was accompanied with such -compression as is here supposed, there could be no fire, properly so -called, and no combustion; this is admitted by Dr Hutton, and it is -therefore a fallacious argument which is brought against his theory, -from the impossibility of fire being maintained in the bowels of the -earth. This impossibility is precisely what he supposes; and yet Mr -Kirwan's arguments are directed, not against the existence of heat in -the interior of the earth, but against the existence of burning and -inflammation. - -After taking notice,[74] that Saussure had succeeded, though with -extreme difficulty, in melting a particle of limestone, so small as -to be visible only with a microscope, "what (adds he) must have been -the heat necessary to melt whole mountains of this matter? Judging -by all that we at present know of heat, such a high degree could -only be produced by the purest air, acting on an enormous quantity -of combustible matter. Now, EHRMAN observed, that the combustion of -two hundred and eighty cubic inches of air, acting on charcoal, was -not able to effect the fusion of one grain of Carrara marble; from -whence it is apparent, that all the air in the atmosphere, nor in ten -atmospheres, would not melt a single mountain of this substance, of -any extent, even if there were a sufficient quantity of inflammable -matter for it to act upon. Judging also of subterraneous heat by what -we know of that of volcanoes, no such heat exists: the highest they -in general produce, is that requisite for the fusion of the volcanic -glass called obsidian, which Saussure found not to exceed 115° of -Wedgewood; but basaltine, which requires 140° of Wedgewood, is never -melted in the lavas of Ætna. How little capable, then, would volcanic -heat be to effect the fusion of Carrara marble, which, according to -the same excellent author, would require a heat of upwards of 6300° -of Wedgewood, if this pyrometer could extend so far? And in what -circumstances does Dr Hutton suppose this astonishing heat to have -existed, and even still to exist, under the ocean, in the bowels of -the earth, where neither a sufficient quantity of pure air, nor of -combustible matter, capable of such mighty effects, can, with any -appearance of probability, be supposed to exist: and, without these, -such degrees of heat cannot even be imagined, without flying into the -region of chimeras." - -[Footnote 74: Geol. Essays, p. 453.] - -166. Now, this reasoning is not applicable to Dr Hutton's hypothesis -of subterraneous heat, because it is grounded on experiments, where -that very separation of the volatile and fixed parts takes place, which -is excluded in that hypothesis. When limestone or marble is exposed -to such heat as is here mentioned, or even to heat of a degree vastly -inferior, the carbonic gas is expelled, and the body is reduced to pure -lime; from the refractory nature of which, as we learn from the fact -relative to barytes, mentioned above, no conclusion can be drawn as to -the infusibility of the same substance, when combined with the carbonic -gas. The Carrara marble may require a heat of 6300° of Wedgewood, to -melt it in the open air, where the carbonic gas escapes from it; but -under such a pressure as would retain this gas, it cannot be inferred, -that it might not melt with the heat of a glass-house furnace. In like -manner, it may be true, that two hundred and eighty cubic inches of -air, acting on charcoal, cannot effect the fusion of one grain of this -marble, after its fixed air is driven off from it; but we cannot from -thence draw any inference, applicable to a case where the carbonic gas -is retained, and where the action of heat is independent of atmospheric -air. - -Nothing, therefore, can be more inconclusive than this reasoning, -as it proceeds on the supposition, that Dr Hutton's system admits -propositions, which in fact it expressly denies. - -167. Of the production and maintenance of heat, in circumstances -so different from those of ordinary experience, we can hardly be -expected to give any explanation; but we are not entitled, merely -on that account, to doubt of the existence of such heat. Mr Kirwan -thinks otherwise: "Judging," he says, "from all we at present know of -heat, such a high degree of it, (as will melt limestone,) could only -be produced by the purest air, acting on an enormous quantity of -combustible matter. Without these, such degrees of heat cannot even be -imagined, without flying into the region of chimeras."[75] - -[Footnote 75: Geol. Essays, p. 454.] - -Now, in the first place, the high degree of temperature which is -here understood, is probably not necessary to the purposes of -mineralization, as has just been shown; and, in the second place, it is -not FIRE, in the usual sense of the word, but HEAT, which is required -for that purpose; and there is nothing chimerical in supposing, that -nature has the means of producing heat, even in a very great degree, -without the assistance of fuel or of vital air. Friction is a source -of heat, unlimited, for what we know, in its extent, and so perhaps -are other operations, both chemical and mechanical; nor are either -combustible substances, or vital air, concerned in the heat thus -produced. So also the heat of the sun's rays in the focus of a burning -glass, the most intense that is known, is independent of the substances -just mentioned; and, though that heat certainly could not calcine a -metal, nor even burn a piece of wood, without oxygenous gas, it would -doubtless produce as high a temperature in the absence as in the -presence of that gas. - -It is true, that it is not by the solar rays that subterraneous heat -is produced; but still, from this instance, we see, that there is no -incongruity in supposing the production of heat to be independent of -combustible bodies, and of vital air. We are indeed, in all cases, -strangers to the origin of heat; philosophers dispute, at this moment, -concerning the source of that which is produced by burning; and much -more are they at a loss to determine, what upholds the light and heat -of the great luminary, which animates all nature by its influence. If -we would form any opinion on this object, we shall do well to attend -to the suggestions of that great philosopher, who was hardly less from -others by his doubts and conjectures, than by his most rigorous and -profound investigations. "May not great, dense, and fixed bodies, when -heated beyond a certain degree, emit light so copiously, as, by the -emission and reaction of its light, and the reflections and refractions -of its rays within its pores, to grow still hotter, till it comes to -a certain period of heat, such as is that of the sun? And, are not -the sun and fixed stars great earths, vehemently hot, whose heat is -conserved by the greatness of the bodies, and the mutual action and -reaction between them and the light which they emit?"[76] - -[Footnote 76: Newton's Optics, _ubi supra_.] - -168. Some recent experiments, seem to make the suggestions in this -query applicable to an opaque body like the earth, as well as to -luminous bodies, such as the sun and fixed stars. The radiation of -heat, where there is no light, was first rendered probable by the -experiments of M. PICTET of Geneva;[77] and the only objections to -which the conclusions from those experiments seemed liable, are removed -by the late very important discoveries of Dr HERSCHEL.[78] From these -it appears, that heat is capable of refraction and reflection, as well -as light, so that it is not absurd to suppose, that _the heat of great, -dense, and faced bodies, may be conserved by the greatness of the -bodies, and the mutual action and reaction between them and the heat -which they emit_. - -[Footnote 77: Essai sur le Feu.] - -[Footnote 78: Phil. Trans. 1800, p. 84.] - -The existence of subterraneous heat is still further rendered probable -from the researches of MAIRAN, which tend to show, that there is -another source of terrestrial heat besides the influence of the solar -rays.[79] - -[Footnote 79: Mém. de l'Acad. des Sciences, 1765, p. 143.] - -Whatever be the truth with regard to these conjectures, it is certain, -that the first and original source of heat is independent of burning. -Burning is an _effect_ of the concentration of heat; and though, by a -certain reaction, it has the power of continuing and augmenting that -heat, it never can be regarded as its primary and material cause. When, -therefore, we suppose a source of heat, independent of fire and of -burning, we suppose what certainly exists in nature, though we are not -informed of the manner of its existence, nor of its place, otherwise -than from considering the phenomena of the mineral kingdom. - -169. Lastly, we are not entitled, according to any rules of -philosophical investigation, to reject a principle, to which we are -fairly led by an induction from facts, merely because we cannot give -a satisfactory explanation of it. It would be a very unsound view of -physical science, which would induce one to deny the principle of -gravitation, though he cannot explain it, or even though the admission -of it reduces him to great metaphysical difficulties. If indeed a -downright absurdity, or inconsistency with known and established -facts, be involved in any principle, it ought not to be admitted, -however it may seem calculated to explain other appearances. If, for -instance, Dr Hutton held, that combustion was carried on in a region -where there was no vital air, we should have said, that he admitted -an absurdity, and that a theory founded on such _postulata_ was worse -than chimerical. But, if the only thing imputable to him is, that, -being led by induction to admit the fusion of mineral substances in the -bowels of the earth, he has assumed the existence of such heat as was -sufficient for this fusion, though he is unable to assign the cause -of it, I believe it will be found, that his system only shares in an -imperfection, which is common to all physical theories, and which the -utmost improvement of science will never completely remove. - -170. Thus, then, we are led, it must be allowed, into the _region of -hypothesis_ and conjecture, but by no means into that of chimeras. -Indeed, the reproach of flying into the latter region, may be said to -come but ill from one, who has trode so often the crude consistence of -the chaos, and who delights to dwell beyond the boundaries of nature. -By sojourning there long, it is not impossible that the eye may become -so accustomed to fantastic forms, that the figures and proportions of -nature shall appear to it deformed and monstrous. - - - - - NOTE VIII. § 24. - - _Sparry structure of - calcareous petrifactions._ - - -171. When the shells and corals in limestone are quoted by -mineralogists, it is not always considered in what state they are -found. In general, they have a sparry structure, very different -from that of the original shell or coral, of which, however, they -retain the figure with wonderful exactness, though probably sometimes -altered in size. Though sparry, they are often foliated, and preserve -their animal, in conjunction with their mineral, texture. Now, this -crystallization is a mark of some operation, quite different from any -that can be ascribed to the water in which these bodies had their -origin, and by which they were brought into their place. They were -impervious to water; and it cannot be said that their sparry structure -has been derived from the percolation of that fluid, carrying new -calcareous matter into their pores. We can account for the change -produced in them, I think, only by supposing them to have been softened -by heat, so as to permit their parts to arrange selves anew, and to -assume the characteristic organization of mineral substances. - -All shells have not the change effected on them that is here referred -to; those in chalk, for instance, retain very much their original form -in all respects. This is what we might expect from the very different -degree of intensity, with which the mineralizing cause has acted on -chalk, and on limestone or marble. In general, it is in the hardest -and most consolidated limestone, that the marine objects are most -completely changed into spar. - -It would be exceedingly interesting to examine, whether any of the -phosphoric acid remains united to shells of either of these kinds. We -might most readily expect it to be united, in a certain degree, to the -shells that are least mineralized. - -This experiment would enable us also to appreciate the force of Mr -Kirwan's argument against the finer marbles, such as the Carrara, -containing shells.[80] This argument proceeds on an experiment, -mentioned in the _Turin Memoirs_ for 1789, from which it appears, -that no phosphoric acid is found in pure limestone; and its absence, -Mr Kirwan says, cannot be attributed to fusion, as phosphoric acid is -indestructible by heat. - -[Footnote 80: Geol. Essays, p. 458.] - -He calls this a demonstration; but, in order to entitle it to that -name, it will be necessary, first, to prove, that phosphoric acid -exists in those limestones which evidently consist of shells in a -mineralized state. If these are found without phosphoric acid, it is -evident that the preceding argument fails entirely. If they are found -to contain that acid, it will then no doubt afford a probability, -though not a demonstration, that Carrara marble does not directly -originate from shells. - -That nature has some process, by which the above acid is separated -from the earth of bones, and probably also from the earth of shells, -is evident from the state in which the bones are found in the caves of -Bayreuth. Those that are the most recent, and least petrified, contain -most of the phosphoric acid. Where the petrifaction has proceeded far, -that acid is not found. - -172. Among many of the strata, such a fluidity has prevailed, as -to enable some of the substances included in them to crystallize. -Calcareous spar and siliceous crystals are often found in stratified -rocks, forming veins of secretion, or lining close cavities, included -on all sides by the uncrystallized rock. In the instances of gneiss, -and many species of marble, almost the whole matter of the stratum is -crystallized. This union of a stratified and crystallized structure -in the same substance, has a great affinity to that union of the -crystallized with the organic structure of shells and corals which has -just been mentioned; and both are doubtless to be referred to the same -cause. - - - - - NOTE IX. § 81. - - _Petroleum, &c._ - - -173. According to the theory of coal laid down above, its two chief -materials, charcoal and bitumen, being furnished by the vegetable and -animal kingdoms, both of the land and of the sea, have formed with one -another a new combination, by the action of subterraneous heat; but -have also, in some cases, been separated by that same action, where -the degree of compression necessary for their union, happened to be -wanting. The carbonic part, when thus separated from the bituminous, -forms an infusible coal, which burns without flame: the bituminous -part, when separated from the carbonic, is found in the various states -of naphtha, petroleum, asphaltes, and jet. - -The great resemblance of infusible or blind coal, to the residuum -obtained by the distillation of bituminous coal; and again, the -coincidence of the bitumens just named, with the volatile part, or -the matter brought over by such distillation, are strong arguments -in favour of this theory. The other facts in the natural history of -coal, serve to confirm the same conclusion; but it must be confessed, -that what we know of the pure bitumens, except the circumstance -just mentioned, is of a more ambiguous nature, and may be reconciled -with different theories. The drops of petroleum contained within the -cavities of the limestone, mentioned at § 31, are however strong facts -in confirmation of Dr Hutton's opinions, and they are furnished by the -substances purely bituminous. A careful examination would probably -make us acquainted with others of the same kind, for limestone is very -often the matrix in which petroleum and asphaltes are contained. The -greatest mine of asphaltes in Europe, that in the _Val de Travers_ in -the territory of Neufchâtel, is in limestone, from which, though it in -some places exudes, it is in general extracted by the application of -heat. The strata for several leagues are impregnated with bitumen; and, -if examined with attention, would probably afford specimens similar to -those which have just been mentioned. - -174. It is a general remark, that, where petroleum is found, on -digging deeper, they come to asphaltes; and, at a depth still greater, -they discover coal. This probably does not hold invariably; but -it is certain, that most of the fountains of petroleum are in the -neighbourhood of coal strata. Petroleum and asphaltes are found in -great abundance in Alsace, in a bed of sand, between two beds of clay -or argillaceous schistus, and the same country also affords coal.[81] -This is true likewise of the fossil pitch of Coal-Brookdale; and of the -petroleum found in St Catharine's Well, near Edinburgh. Auvergne[82] -contains abundance of fossil pitch, which exudes, in the warm season, -from a rock impregnated with it through its whole mass. There are also -coal strata in the same country, not far distant. - -[Footnote 81: Encyclopédia, mot, _Asphalte_.] - -[Footnote 82: Voyage en Auvergne, par Lagrand, tom. i. p. 351.] - -A very satisfactory observation relating to this subject, has lately -been communicated from a country, with whose natural history we were -till of late entirely unacquainted. In the Burmha empire, petroleum is -dug up in an argillaceous earth, from the depth of seventy cubits. This -argillaceous earth, or schistus, lies under a bed of freestone; and -under all, about one hundred and thirty cubits from the surface, is a -bed of coal.[83] - -[Footnote 83: Asiatic Researches, vol. vi, art. 6. p. 130.] - -175. In the petroleum lake of the Island of Trinidad, described _Phil -Trans._ 1789, the petroleum evidently exudes from the rock, and is -collected in a variety of springs in the bottom, after which it -hardens, and acquires the consistency of pitch. The manner, therefore, -in which petroleum exists in the strata, is very consistent with the -idea of its having been introduced in the form of a hot vapour. - -Even amber appears to have some relation to coal. It is found in the -unconsolidated earth in Prussia and Pomerania; but I am not sure -whether this earth is _travelled_ or not. In the same earth where the -amber is found, there is often a mixture of coaly matter, which burns -in the fire; it is apparently fibrous, and has been considered as a -kind of fossil-wood.[84] - -[Footnote 84: Buffon, Hist. Nat. des Mineraux, tom. ii. p. 5.] - -These circumstances make out a connection between the purer bitumens -and ordinary coal; but do not, it must be acknowledged, establish any -thing with respect to the more immediate relation, supposed in this -theory to exist between them and blind coal. It is probable, indeed, -that, to discover any facts of that kind, the natural history of both -substances must be more carefully examined; the natural history of -blind coal, in particular, has hitherto been but little attended to. - -176. A fact is mentioned by Mr Kirwan, which must not be regarded as -less valuable for being adverse to this theory. It is, that neither -petroleum, nor any fossil bitumen, is found in the vicinity of the -Kilkenny coal, as might be expected, if that coal was deprived of -its bituminous part by subterraneous distillation.[85] This, however, -admits of explanation. Though a general connection, on the above -hypothesis, might be expected between bitumens and infusible coal, we -cannot look for it in every instance. The heat which drove off the -bitumen from one part of a stratum of coal, may only have forced it to -a colder part of the same stratum; and thus, in separating it from one -portion of carbonic matter, may have united it to another. Blind coal -may therefore be found where no bitumen has been actually extricated. -In like manner, bitumen may have been separated, where the coal was -not reduced to the state of coke, as a part of the bitumen only may -have been driven off, and enough left to prevent the coal from becoming -absolutely infusible. - -[Footnote 85: Geol. Essays, p. 473.] - -It should be considered too, if the bitumen was really separated, and -forced, in the state of vapour, into some argillaceous or limestone -stratum, that this stratum may have been wasted and worn away long ago, -so that the bitumen it contained may have entirely disappeared. It does -not therefore necessarily follow, that, wherever we find blind coal, -there also we should discover some of the purer bitumens. - - - - - NOTE X. § 37. - - _The height above the level of the sea - at which the marks of aqueous - deposition are now found._ - - -177. We have two methods of determining the _minimum_ of the change -which has happened to the relative level of the sea and land; or -for fixing a limit, which the true quantity of that change must -necessarily exceed. The one is, by observing to what height the regular -stratification of mountains reaches above the present level of the sea; -the other is, by determining the greatest height above that level, -at which the remains of marine animals are now found. Of these two -criteria, the first seems preferable, as the fact on which it proceeds -is most general, and least subject to be affected by accidental causes, -or such as have operated since the formation of the rocks. The results -of both, however, if we are careful to select the extreme cases, agree -more nearly than could have been expected. - -178. The mountain Rosa, in the Alps, is entirely of stratified rocks, -very regularly disposed, and nearly horizontal.[86] The highest summit -of this mountain is, by Saussure's measurement, 2430 toises, or 14739 -English feet, above the level of the sea, or lower than the top of -Mont Blanc only by 20 toises, or 128 feet.[87] This is, I believe, the -highest point on the earth's surface, at which the marks of regular -stratification are certainly known to exist; for though, by the account -of the same excellent mineralogist, Mont Blanc itself is stratified, -yet, as the rock is granite, the stratification vertical, and somewhat -ambiguous, it is much less proper than Monte Rosa for ascertaining the -limit in question. - -[Footnote 86: Voyages aux Alpes, tom. iv. § 2138.] - -[Footnote 87: _Ibid._ § 2135.] - -179. Again, in the new continent, we have an instance of shells -contained in a rock, not much lower than the summit of Monte Rosa. -This is one described by Don ULLOA, near the quicksilver mine of -Guanca-Velica, in Peru. The height at which a specimen of these shells, -given by Ulloa to M. Le GENTIL, was found, was 2222 1/3 toises, or -14190 feet English, above the level of the seas.[88] This height agrees -with the preceding, within 549 feet, a quantity comparatively small. - -[Footnote 88: See Hist. Acad. des Sciences, 1770. Phys. Générale, No. -7.] - -180. The last of the facts just mentioned is curiously commented on by -Mr Kirwan. As he has proved, he says, that the mountains higher than -8500 feet were all formed before the creation of fish, it follows, -that the shells found at Guanca-Velica, must have been carried there -by the deluge.[89] Now, without objecting to the proof here referred -to, (though it seems very open to objection,) it is sufficient to -remark, that, if the shells at Guanca-Velica were carried there by -the deluge, or any other cause that operated after the formation of -the rock of which the mountain consists, they can make no part of -that rock, but must lie, like other adventitious fossils, loose and -detached on the surface, or at most externally agglutinated to the -stone. This, however, is certainly not the fact; for, in the account -just quoted, we read, that Don Ulloa told M. le Gentil, "qu'il avoit -détaché ces coquilles d'un banc fort épais." This seems plainly to -indicate, that the shells were included in a bed of rock; But, granting -that the expression is a little ambiguous, on turning to the _Mémoires -Philosophiques_ of the same author, the difficulty is completely -removed, and it is made evident, that these shells are in fact -integrant parts of the rock. "On voit dans ces montagnes-là, (about -Guanca-Velica, and particularly at that in which is the quicksilver -mine,) des coquilles entières, petrifiées et enfermées au milieu de la -roche, que les eaux de pluie mettent à decouvert. Ces coquilles font -corps avec la pierre; mais malgré cela, on remarque que la partie qui -fut coquille, se distingue par la couleur, la structure, la qualité de -la matière de tout autre corps pierreux qui l'enferme, et du massif qui -s'est fixé entre les deux ecailles,"[90] &c. He goes on to say, that -one can distinguish marks of these shells having been worn, before they -were included in the stone. - -[Footnote 89: Geol. Essays, p. 54.] - -[Footnote 90: Mém. Philosophiques de Don Ulloa, Discours xvi. vol. i. -p. 364.] - -181. Thus it appears, that whatever proof any fossil shell affords, -that the rock in which it is found was formed under the sea, the -same is afforded by the fossil shells of Guanca-Velica; and we are, -therefore, perfectly entitled to conclude, that the relative level of -the sea and land has changed, since the formation of the latter, by -more than 14000 feet. The height assumed in § 37 is therefore much -under the truth; and the water, for which the Neptunists must provide -room in subterraneous caverns, might very well have been stated at -more than a five-hundredth part of the whole mass of the earth. - -Thus also the argument by which the Neptunists would connect the -creation of fish with the beginning of the secondary mountains, falls -entirely to the ground. Indeed, it is strange that Mr Kirwan should -have supposed it possible, that the shells in question were loose and -unconnected with the rock, and had continued so, ever since the deluge, -in such elevated ground, where the torrents wear and cut down the -mountains with unexampled violence, and have hollowed out _Quebradas_ -so much deeper and more abrupt than the glens or vallies among other -mountains. He had not, I believe, seen the passage I have quoted from -Ulloa; but the circumstances did not warrant the shells in question to -be regarded as extraneous and adventitious fossils. A geologist should -have known better than to suppose this possible. When we see VOLTAIRE -ascribing to accidental causes the transportation of those shells -which he had been told were often found among the Alps, we can excuse -in a Poet and a Wit, that ignorance of the facts in mineralogy, which -concealed from him the extreme absurdity of his assertion; but when a -Chemist or Mineralogist talks and reasons in the same manner, we cannot -consider him as entitled to the same indulgence. - - - - - NOTE XI. § 42. - - _Fracture and dislocation - of the strata._ - - -182. The greatest part of the facts relative to the fracture and -dislocation of the strata, belongs to the history of veins. The -instances of slips, where no new mineral substance is introduced -between the separated rocks, are what properly belong to this place. -The frequency of these, and their great extent, are well known wherever -mines have been wrought. In some of them no opening is left, but the -slipped strata remain contiguous; in other cases, there is introduced -an unconsolidated earth, often a clay, which may be supposed to have -come from above, arid very probably to have been carried down by the -water. In some such cases, however, there are not wanting appearances, -which show the matter in the slip to have been forced up from below, -as we find it to contain substances which could not have come from the -surface.[91] - -[Footnote 91: Unconsolidated earth contained between the sides of -a rock that has slipped, is frequent in Cornwall, and is called a -_Fleukan_. ] - -183. A very remarkable fact of this kind occurred not long ago, in -digging the Huddersfield canal in Yorkshire; and a very distinct -account of it is given in the _Philosophical Transactions_, by the -engineer who directed the work. In carrying a tunnel into the heart of -a hill, the miners came to what is called in the description a _fault_, -_throw_, or _break_, or what we have here called a shift, which was -filled with _shale_ set on edge, mixed with softer earth, and in some -places with small lumps of coal. The fault or space filled with these -materials, was in general about four yards broad, and lay nearly in -the direction of the tunnel, so that a considerable extent of it was -visible. Beside the shale, it contained a _rib_ of limestone, about -four feet thick, which run parallel to the sides of the _fault_, and -about four feet from the southern margin of it. On each side of this -rib were found balls of limestone, promiscuously scattered, and of -various sizes, from an ounce to one hundred pounds weight. The balls, -when broken, were found to contain some pyrites near their edges; they -were not perfectly globular, but flattened on the opposite sides, and -similar to one another.[92] At the time when the account was written, -about seventy yards of the rib had been discovered. - -[Footnote 92: Phil. Trans. 1796, p. 350.] - -184. Now, it is certain, that neither this rib of limestone, nor the -balls that accompanied it, can have come from above, as there is no -limestone within twenty miles of the place where they were found. They -must, therefore, have been forced up from below, and no doubt belong -to some limestone strata, which lie there at a great depth under the -surface. The length of this fragment of rock, which, from the account, -one must suppose to have been entire, conveys no mean idea, either of -the intensity or regularity of the force by which it was brought into -its present situation. In veins, it is not uncommon to meet with stones -that appear to have come from a greater depth: but this is probably the -most remarkable instance of the same phenomenon, which has appeared in -a mere slip, and none, I think, can speak a language less liable to be -misunderstood. - -185. I shall here mention another mark of violent fracture, that has -been observed in rocks of breccia or pudding-stone, which, though not -of the same kind with the preceding, and of a nature quite peculiar, -belongs rather to this place than any other. In rocks of the kind, -just mentioned, it sometimes happens, that considerable portions are -separated from one another, as if by a mathematical plane, which had -cut right across all the quartzy pebbles in its way. None of the -pebbles are drawn out of their sockets, that is, out of the cement that -surrounds them, but are divided in two with a very smooth and even -fracture. The pebbles, in the instances which I have seen, were of -quartz, and other species of primary and much indurated rock. - -Lord WEBB SEYMOUR and I observed pudding-stone rocks, exhibiting, -instances of this singular kind of fracture, near Oban, in Argyleshire, -about three years ago. The phenomenon was then entirely new to us both; -but I have since met with an instance of the same kind in Saussure's -last work. As the fact is of so particular a kind, I shall state it in -his own words: The place was on the sea shore, near the little town of -Alassio, between Nice and Genoa. - -"En passant entre ces blocs de breche, j'admirai quelques-uns -d'entr'eux, d'une grandeur considérable, et taillés en cubes, avec -la plus parfaite régularité. Il y avoit ceci de remarquable, c'est -que l'action de la pesanteur, qui avoit taillé ces cubes en rompant -leurs couches, avoit coupé tous les cailloux des breches à fleur de -la surface de la pierre, aussi nettement que si c'eût été une masse -molle qu'on eût tranchée verticalement avec un rasoir. Cependant parmi -ces cailloux, la plupart calcaires, il s'en trouvoit de très durs, de -petrosilex, par exemple, même de jade, qui étoient tranchées tout -aussi nettement que les autres."[93] - -[Footnote 93: Voyages aux Alpes, tom. iii. § 1731.] - -186. This description is no doubt accurate, though it involves in it -something of theory, viz. that the fracture was made by the weight of -the stone. This may indeed be true: the operation probably belongs -altogether to the surface, and is one with which the powers of the -mineral regions are not directly concerned. The phenomenon, however, -appears to me, on every supposition, very difficult to explain. In the -specimen which I brought from Oban, the smallest pieces of stone are -cut in two, as well as the largest. The consolidation and hardness of -the mass are very great, and the connection of the different fragments -so perfect, that it is no wonder the whole should break as one stone. -But still, that the fracture should be so exactly in one plane, and -without any shattering, is not a little enigmatical; if it is indeed -a fracture, it must be the consequence of an immense impulse, very -suddenly communicated. - - - - - NOTE XII. § 43. - - _Elevation and inflection - of the strata._ - - -187. The evidence of the different formation of the primary and -secondary strata, and of the changes which the former have undergone, -is best seen at the points where those strata come into contact with -one another. Dr Hutton was not the first who observed these junctions, -though the first who rightly interpreted the appearances which they -exhibit. He has mentioned observations of this sort by De Luc on the -confines of the Hartz; by the author of the _Tableau de la Suisse_, -at the pass of Yetz; by Voight, in Thuringia; and Schreiber, at the -mountain of Gardette.[94] - -[Footnote 94: Theory of the Earth, vol. i. p. 410 to 453.] - -The leading facts to be remarked, are, - -I. The vertical or very upright position of the primary or lower strata. - -II. The superstratification of the secondary, in a position nearly -horizontal, so as to be at right angles to those on which they rest. - -III. The interposition of a breccia between them or, as happens in -many cases, the transition of the lowest of the secondary beds into a -breccia, containing fragments sometimes worn, sometimes angular, of the -primary rock. - -This last is a phenomenon extremely general, and all our subsequent -information confirms Dr Hutton's anticipations concerning it. "It will -be very remarkable," he says, "if similar appearances, (such as those -of the breccia described by Voight,) are always found upon the junction -of the Alpine with the level countries."[95] Saussure, in a part of his -work, not published when Dr Hutton wrote this passage, has attested the -generality of the fact with respect to the whole Alps, from the Tyrol -to the Mediterranean: "Un sait que l'on observe sans aucune exception, -ce sont les amas de débris, sous la forme de blocs, de breches, de -poudingues, de grès, de sable, ou amoncelés, et formant des montagnes, -ou des collines, dispersés sur le bord exterieur, ou même dans les -plaines qui bordent la chaine des Alpes."[96] - -[Footnote 95: Theory of the Earth, vol. i. p. 448.] - -[Footnote 96: Voyages aux Alpes, tom. iv. § 2330.] - -This passage is perfectly decisive as to the generality of the fact, -that the Alps, from the Tyrol to the Mediterranean, are bordered all -round by pudding-stones or breccias. At the same time, it is necessary -to remark, that M. Saussure, by enumerating loose blocks and sand, -along with pudding-stones, breccias and grit, confounds together things -which are extremely different, and which have had their origin at -periods extremely remote from one another. The consolidated rocks of -breccia, pudding-stone and grit, though they are indications of waste, -have received their present character at the bottom of the sea: the -loose blocks of stone, the sand and gravel, on the other hand, are the -effects of the waste now going forward on the surface of the land, and -are the materials out of which rocks of the three kinds just mentioned -may hereafter be composed. If so skilful a mineralogist as Saussure -is guilty of such inaccuracy, it must be ascribed to the confusion -necessarily arising from the system which he followed, and not to his -own want of discrimination. - -188. The same phenomenon, of a breccia circumscribing the primary -mountains, is met with in Scotland; and the Grampians, wherever they -are bounded by secondary strata, whether on the south or north, afford -examples of it. The breccia generally consists of the fragments of -the primary rock, most commonly rounded, but sometimes also angular, -united by a cement of secondary formation, and the whole disposed -in horizontal beds. It was on the constancy of this accompaniment -of the primary strata, and on the great quantity of highly polished -gravel often included in these breccias, that Dr Hutton grounded the -hypothesis of the double raising up and letting down of the ancient -strata. See § 43. - -189. As the spots where the primary and secondary rocks may be seen -in contact with one another are of great importance in geology, and -present to the senses the most striking monuments of the high antiquity -and great revolutions of the globe, it may be useful to point out such -of them as have been observed in this island. To those which Dr Hutton -has described, I have a few more to add, the result of some geological -excursions, which I made in company with the Right Honourable Lord -WEBB SEYMOUR, to whose assistance I have been much indebted in the -prosecution of these inquiries. - -190. The most southern junction which we observed is at Torbay, where -the ancient schistus which prevails along the coast, from the Land's -End to that point, receives a covering of red horizontal sandstone, -the same which composes the greater part of Devonshire. The spot where -the immediate contact is visible, is on the shore, a little to the -south of Paynton; and one circumstance, which among many others serves -to distinguish the different formation of the two kinds of rock, is, -that the schistus, which is elevated here at an angle of about 45°, is -full of quartz veins, which veins are entirely confined to it, and do -not, in as far as we could observe, penetrate into the sandstone, in a -single instance. It is probable, that on the north shore of the bay, -the same line of junction is visible: we saw it at Babicomb Bay, still -more to the northward. - -191. From this place, the secondary strata of different kinds prevail -without interruption, along the coast of the British Channel, and -of the German Ocean, as far as Berwick upon Tweed, and for some -miles beyond it. The sea coast then intersects a primary ridge, the -Lammermuir Hills, which traverses Scotland from east to west, uniting, -near the centre of the country, with the metalliferous range of -Leadhills, and afterwards with the mountains of Galloway. The section -which the sea coast makes of the eastern extremity of this ridge, is -highly instructive, from the great disturbance of the primary strata, -and the variety of their inflections. The junction of these strata -with the secondary, on the south side, is near the little sea-port of -Eyemouth, but the immediate contact is not visible. - -On the north side of the ridge, the junction is at a point called the -_Siccar_, not far from Dunglass, the seat of Sir James Hall, Baronet. -By being well laid open, and dissected by the working of the sea, -the rock here displays the relation between the two orders of strata -to great advantage. Dr Hutton himself has described this junction; -_Theory of the Earth_, vol. i. p. 464. - -192. From the point just mentioned, the secondary strata continue as -far as Stonehaven, where the southern chain of the Grampian mountains -is intersected by the sea-coast. Here a great mass of pudding-stone -appears to lie on the primary strata, but their immediate contact has -not been observed. - -193. Going along the coast toward the north, the next junctions which -we saw were on the shore, one near Gardenston, and another near Cullen, -in Banffshire. The latter is very distinct; it is about a mile to the -westward of the rocks called _The Three Kings_, where a red sandstone, -the lower beds of which involve much quartzy gravel, lies horizontally -upon very regular, upright, and highly indurated strata. Some of these -strata are micaceous, and others of the granulated quartz, mentioned in -§ 153. - -194. This last is, I believe, the most northern junction which has -been observed in our island. The western coast furnishes several more, -which however are not all visible. The line of separation, between -the primary schistus of the Grampians and the sandstone which covers -it, is intersected at its western extremity by the Frith of Clyde, -not far from Ardencaple in Dunbartonshire. The two kinds of stone can -be traced within a few yards of each other, but not to the actual -contact: the beds of sandstone nearest the schistus form as usual a -breccia, loaded with fragments of the primary rock. The secondary rock, -which begins here, continues for about fifty miles south, to Girvan in -Ayrshire, where the primary schistus again rises up, but is not seen in -contact with the secondary. It extends to the Mull of Galloway and the -shores of the Solway Frith. - -The Isle of Arran, however, not far distant from this part of the -coast, contains a junction at its northern extremity, where secondary -strata of limestone lie immediately on a primary micaceous schistus. -This is described by Dr Hutton, and was the first phenomenon of the -kind which he had an opportunity of examining.[97] The junction is -visible but at one spot, and is not seen so distinctly as in some of -the instances just mentioned; but the great quantity of pudding-stone -near it, renders it more interesting than it would be otherwise. As the -greater part of this little island is surrounded by secondary strata, -other junctions might be expected to be visible. - -[Footnote 97: Theory of the Earth, vol. i. p. 429.] - -195. On the coast of England and Wales, from the Solway Frith to the -Land's End, though there are several alternations from secondary to -primary strata, I know not that any of them have been observed. At St -Bride's Bay, in Pembrokeshire, the primary and secondary strata are -seen very near their junction; but the precise line I believe is not -visible. The coal-pits in the secondary strata, approach here within a -few hundred yards of the primary. The secondary strata which commence -at this place, occupy both sides of the Bristol Channel, and meet the -Cornish schistus, which extends across the north of Devonshire to the -Quantock Hills, in a line that may be looked for on the sea coast, some -where between Watchett and Minehead. - -196. Besides the sea coast, the beds of rivers may be expected to -afford information on this subject. To the instances I have mentioned, -I have accordingly two others from the inland country to be added. One -of them is from the river Jed, a little way above Jedburgh, where the -secondary strata are seen lying horizontally on the primary, a section -of both being made by the bed of the river. The phenomena here are very -distinct, and strongly marked; Dr Hutton has described and represented -them in a plate.[98] He has mentioned another junction, not far from -this, which he saw in the Tiviot. Both these belong to the same primary -ridge with the Siccar point. - -[Footnote 98: Theory of the Earth, vol. i. p. 430; also plate 3.] - -197. I shall mention only one other, which was discovered by Lord Webb -Seymour and myself, at the foot of the high mountain of Ingleborough, -in Yorkshire. As we went along the Askrig road from Ingleton, about a -mile and a half from the latter, an opening appeared in the side of -the hill, on the right, about one hundred yards from the road, formed -by a large stone, which lay horizontally, and was supported by two -others, standing upright. On going up to the spot, we found it was the -mouth of a small cave, the stone lying horizontally, being part of a -limestone bed, and the two upright stones, vertical plates of a primary -argillaceous schistus. The limestone bed, which formed the roof of the -cave, was nearly horizontal, declining to the south-east; the schistus -nearly vertical, stretching from north-west by west, to south-east by -east. The schistus, though close in contact with the limestone, seemed -to contain nothing calcareous, and did not effervesce with acids in the -slightest degree. - -As this cave is at the foot of Ingleborough, a cold wind, 24° below the -temperature of the external air, which issued from the mouth of it, -might very well be supposed to come from the inmost recesses of that -mountain. Ingleborough, which consists entirely of strata of limestone -and grit, nearly horizontal, and alternating with one another, rises -to the height of 1800 or 2000 feet above the spot where we now stood. -This, I believe, is the greatest thickness of secondary strata that -has ever been observed incumbent on the primary, and it is therefore -a geological fact highly deserving of attention. The country all -round, to a very great extent, is composed of limestone, with a few -beds of grit interposed, and forming, beside Ingleborough, some other -high mountains, such as Wharnside and Pennigant, all resting, it is -probable, on the same foundation. - -At the spot just described, no breccia appeared to be interposed -between the primitive and secondary rock; but we found a breccia at -another point of the same junction, not far distant. This was at a -cascade, in the river Greta, called Thornton Force, about two miles -and a half from the place just mentioned. The Greta here precipitates -itself from a horizontal rock of limestone; and, after a fall of -about eighteen or twenty feet, is received into a bason which it has -worked out in the primary schistus. This schistus is in beds almost -perpendicular; it exactly resembles that which has Just been described, -and stretches nearly in the same direction. On the south side of the -river a breccia was seen, lying upon the schistus, or rather, it might -be said, that the lowest beds of limestone contained in them many -rounded fragments of stone, which, on comparison, resembled exactly -the schistus underneath. The primary rock itself is here seven or eight -hundred feet above the level of the sea. - -The same schistus, somewhat lower down the valley, and nearer to -Ingleton, appears in large quantities, and is quarried for slate. Here, -however, the immediate junction of the limestone and schistus does not -appear. - -I have dwelt longer on the description of these appearances than on -any others of the same kind, because, from the great mass of secondary -strata which here covers the primary, the circumstances are such as we -cannot expect to see very often exemplified. - -198. The Lakes of Cumberland are much visited by travellers; and it may -be worth remarking, on that account, that, as the site of these lakes -is a patch of primary country, bounded on all sides by secondary, so, -in the rivers that run from the lakes, such junctions as we are now -treating of may be expected to be found. Under Dun-Mallet, on the side -toward Ulles Water, we observed a breccia, which was in horizontal -layers, and seemed to lie on the primary schistus, so that the whole -hill is perhaps a piece of more indurated breccia, or secondary rock, -which has resisted the wearing and washing down of the rivers better -than the rest. - -199. After ascertaining the fact of the disturbance of the strata, and -their removal from their original position, it is of consequence to -inquire into the direction of the force by which these changes have -been produced. Now, if the disturbed or elevated strata, were every -where in planes, without bending or sinuosity, it might perhaps be -hard to determine, whether that force had acted in the direction of -gravity, or in the opposite. Either supposition would account for the -appearances; and, as gravity is a known force, providing we can find -some place fit to receive the matter impelled downward by it, its -action would furnish the most probable solution of the difficulty. - -It is on this principle that the Neptunian system proceeds, imagining, -that certain great caverns or vacuities having been opened in the -interior of the globe, a great part of the waters which formerly -covered its surface, retired into them, and much of the solid rock also -sunk down at the same time. In this way, one extremity of a stratum -has been elevated, while the other has been depressed, and a certain -inclination to the horizon has been given to the whole of it. Thus one -cause serves two purposes; the vacuities in the interior of the earth -account, both for the depression of the sea, and the elevation of the -land; and the Neptunists, if the phenomena were all such as have been -now stated, might boast of a felicity of explanation, not very usual in -their system. - -But this appearance of success vanishes, when the elevation and -disturbance of the strata are more minutely examined, and are found -to include waving and inflection, in a great variety of forms. It -then becomes evident, that the beds of rock, at the time when they -were disturbed from their horizontal position, had not their present -hardness and rigidity, but were, in a certain degree at least, soft -and flexible. Without these qualities, they could not have received, -as they have often done, the curvature of a circle, not many feet, -nay, not many inches, in diameter; nor could they have been bent into -superficies, with their curvature in opposite directions, so that -the same surface is in one part convex, and in another concave, on -the same side, with a line of contrary flexure interposed. These are -appearances, not reconcilable with the mere falling in, and breaking -down of indurated rocks. - -200. The inflections and wavings that we are here speaking of, though -not peculiar to the primary strata, are found most frequently among -them, and are perfectly familiar to every one who his travelled among -mountains with any view to the study of geology. The following are a -few instances of this phenomenon out of a great number which might be -produced. - -Saussure, in describing the route from Geneva to Chamouni, mentions -many remarkable instances of the bending of the strata, and -particularly where the small stream of Nant d'Arpenaz forms a cascade, -by falling over the face of a perpendicular limestone rock. The strata -of this rock are bent into circular arches, extremely regular, and with -their concavity turned to the left. What deserves particularly to be -remarked, is, that a mountain behind the cascade has its strata bent -in a direction opposite to the former, or with their concavity to the -right. There is no doubt that the strata of both rocks are the same, so -that a vertical section of them would give a curve, in the figure of an -S.[99] These circumstances are mentioned by Saussure, and from them we -may infer this other property of these strata, that their section by a -horizontal plane, must exhibit a system of straight lines, probably all -parallel to one another. - -[Footnote 99: Voyages aux Alpes, vol i. § 472; also, Theory of the -Earth, vol. ii. p. 30.] - -The same mineralogist describes the calcareous strata which compose -the mountain Axenberg, on the side of the Lake of Lucerne, as having -from top to bottom of the mountain the form of the letter S compressed, -(_ecrasée_) with their curvature in some places very great. These -inflections are repeated several times, and often in contrary -directions; the layers are sometimes broken, where their curvature is -greatest.[100] - -[Footnote 100: Voyages aux Alpes, tom. iv. § 1935.] - -On the side of the same lake, is another instance of bent strata, in a -mountain, of which the beds are horizontal in the lower part, but are -bent at one end upwards, in the form of the letter C. The horizontal -part is of great extent, and the rock is also calcareous,[101] - -[Footnote 101: _Ibid._ § 337.] - -The Montagne de la Tuile, near Montmelian, receives its name from the -beds of rock being incurvated in form of a tyle.[102] Among secondary -mountains, the same kind of phenomena are observed, though less -frequently, and with less variety of inflection. The chain of Jura is -secondary, and the beds which compose it are of limestone, or of grit: -they are bent in such a manner, that in a transverse section of the -mountain, each layer would have the figure of a parabola.[103] - -[Footnote 102: _Ibid._ vol. iii. § 1182, and plate i.] - -[Footnote 103: _Ibid._ tom. i. § 334.] - -201. The Pyrenees furnish abundance of phenomena of the same kind, -as we learn from the _Essai sur la Mineralogie des Pyrenées_. The -calcareous strata of the valley of Aspe, represented plate v. of that -work, deserve particularly to be remarked. - -202. Our own island abounds with examples of the bending and inflection -of the strata, especially the primary, and many of them very much -resembling those in the Alps and Pyrenees. On the top of the mountain -of _Ben-Lawers_, in Perthshire, there is a rock, the face of which -exhibits a section of a great number of thin equidistant layers, bent -backwards and forwards like those described by Saussure; and this -unequivocal proof of the rock having once existed in the state of a -flexible and tenacious paste, is rendered more striking, by the great -elevation of the spot, and the ruggedness and induration, both of -the stone itself, and of every thing that surrounds it. Many other -mountains in this tract consist of a schistus, which is talcose rather -than micaceous, and subject, in a remarkable degree, to the sort of -sinuosity and inflection here treated of. - -The appearances of the primary strata on the coast of Berwickshire, -have been already mentioned, as affording much valuable instruction in -geology. They also exemplify the waving and inflection of the strata -on a large scale, and with great variety. A section of some of them -is given by Dr Hutton, in his _Theory of the Earth_, vol. i. from a -drawing made by Sir James Hall. The nature of the curve superficies -into which the schistus is bent, is the better understood from this, -that, besides transverse sections from north to south, the deep -indentures which the sea has made, and the projecting points of rock, -exhibit many longitudinal sections, in a direction from east to west. - -203. The dock-yards at Plymouth are in several places cut out of a -solid rock of primary schistus, singularly incurvated. The inflections -are seen there to great advantage, being exhibited in three sections, -at right angles to one another, transverse, longitudinal and horizontal. - -204. From these instances, to which it were easy to add many more, two -conclusions may be drawn. The first of these is very obvious, viz. -that the strata must have been pliant and soft when they acquired -their present form. The bending of an indurated bed of stone into an -arch of great curvature, and without fracture, as in the preceding -examples, is a physical impossibility. Saussure has indeed observed a -fracture to accompany the bending, in one or two cases; but it is an -uncommon phenomenon, and, where it happens, must no doubt be understood -to indicate an imperfect flexibility. Now, if it be granted that the -strata were at any time soft and flexible, since their complete -formation, it will be found impossible to deny their having been -softened by the application of heat. - -205. The second conclusion, alluded to above, results from a property, -which belongs very generally, if not universally, to the inflections of -the strata. This consists in their curvature being simple, or in one -dimension only, like a cylindric superficies, not double, or in two -dimensions, like the superficies of a sphere or spheroid. This may be -otherwise expressed by saying, that the sections of the bent strata, -by a horizontal plane, are straight lines, parallel to one another. On -this account, every such stratum seems as if it were bent over all axis -and the axes of all these different bendings, for a great extent of -country, are nearly parallel. - -The truth of this is evident, where the strata are seen both -transversely and longitudinally. It holds remarkably of the primary -schistus on the coast of Berwickshire; where the beds of rock, if -cut transversely, by a vertical plane, exhibit the figures of very -complicated curves, with various maxima and minima, and points of -contrary flexure; but, if they are cut by a horizontal plane, the -section will produce nothing but straight lines, nearly parallel. - -206. The constancy of the direction of the primary strata, when -estimated by their intersection with the horizontal plane, is often -very remarkable. Their elevation and flexure are subject to great and -sudden changes, so as to pass not only from greater to less, but from -one side to the opposite, within a small distance; but the horizontal -line in which they _stretch_, usually preserves the same bearing -to a great extent. The general direction of the primary strata, in -the south part of Scotland, is from E.N.E. to W.S.W.; and the same -is nearly true of those which compose the ridge of the Grampians on -the north, and the hills of Cumberland and Westmoreland toward the -south, though between the schistus of these three tracts, there is no -communication at the surface, each being entirely separated from the -one next it, by the interposition of secondary strata. I have already -mentioned the observations of Lord Webb Seymour and myself, at the -foot of Ingleborough; and it appears from them, that the vertical -schistus on which that mountain rests, though it still preserves an -eastern and western direction, varies several points from that of the -more northern strata. The strata of Wales return more to the first -mentioned direction, and those of Devonshire and Cornwall agree with -it very nearly. In all this, it will be easily conceived, that I do -not mean to speak with absolute precision, or to deny the existence of -great local irregularities. The result given is only a kind of average, -deduced from observations hardly susceptible of great exactness, and -not yet sufficiently multiplied to give to the conclusion all the -accuracy it may attain. - -207. This tendency of the primary strata to take a uniform direction, -has also been observed in other countries. Saussure remarked in the -Alps, that the beds of schistus are generally parallel to the chains of -mountains composed of them;[104] and this remark is probably applicable -to all mountains consisting of primary strata. The general direction, -therefore, of the schistus of the Alps, must be confined between W. -10° S. and W. 40° S. In the Pyrenees, the direction of the strata is -about W.N.W.[105] If Saussure's rule may be depended on, the schistus -of the Altaic, and most of the other great chains in the old continent, -are in directions that run considerably to the south of west. The -Urals, and perhaps some other of the northern chains, are however -entirely different. In the Urals, as we learn not only from the general -direction of the chain, but from a section of it in the 10th volume of -the Nova Acta of Petersburgh (Tab. 12,) the direction of the strata is -nearly from N. to S. This last is probably the direction in the great -chains of South America; so that the uniformity of direction in the -primary strata, which some mineralogists would extend to those of the -whole earth, is certainly imaginary, though there can be no doubt that -it extends over very large portions of the earth's surface.[106] - -[Footnote 104: Voyage aux Alpes, tom. i. § 577.] - -[Footnote 105: Essai sur la Mineralogie des Pyrenées.] - -[Footnote 106: It is perhaps unnecessary to observe, that the two -propositions, that the intersections of the strata with the horizon -are parallel lines; and that they are lines which reserve the same -bearing with respect to the points of the compass; are nearly the same -thing for tracts of moderate extent, but for large portions of the -earth's surface are extremely different. If, for instance, the belt -of primary vertical schistus, which traverses the south of Scotland, -were to be produced eastward in the same plane, from its northern -extremity, where its direction is E.N.E. and its latitude 55° 57', it -would cut the meridian always less obliquely as it advanced, till, -having increased it longitude about 26° 28', it would be at right -angles to the meridian, and its direction of consequence due east and -west. This would happen in the parallel of 58° 51', (on the shore of -the Gulf of Finland, near Revel,) the strata being now extended about -880 G. miles from the Siccar Point. Conversely, vertical strata, having -the same bearing with respect to the meridian, may be in planes very -much inclined to one another. A stratum which bears east and west in -Cornwall, and one that does the same at the east end of the Altaic, -will be in planes, which, if produced, would cut one another at right -angles. All this is sufficiently plain from the doctrine of the -sphere, and is mentioned here merely as a caution to prevent too hasty -conclusions from being drawn from any correspondence of bearing among -the strata of remote countries. - -For the sake of those who would deduce the medium bearing of any body -of strata from a number of observations, it may be proper to take -notice, that the true average is not to be found by simply taking -an arithimetical mean among all the observations. A more exact way -is to work by the traverse table, as in keeping a ship's reckoning, -(supposing the distance run to be always unity,) and to compute from -the observed bearings the amount of all the southing or northing, and -also all the easting and westing. The sum of all the latter, divided -by the sum of all the former, is the tangent of the angle which the -general direction of the strata makes with the meridian.] - -208. The tendency of the primary strata to remain straight in the -horizontal direction, and to be bent in the vertical, is a phenomenon -which points very directly to the causes from whence it has arisen. A -surface of simple curvature, or a surface straight in one direction, -is what the application of forces to different points of a plane, -which is flexible, though with a certain degree of rigidity, will -naturally produce. The supposition, therefore, that these strata were -once flat and horizontal, and were impelled upward from that situation -before they had become rigid or hard, will explain their having the -kind of curvature which removes them as little as possible from their -original condition. But no other hypothesis affords any reason why -they should have that curvature more than any other. From the falling -in of roofs of caverns, we might expect fracture and dislocation, -without any order or regularity; but certainly no bending or sinuosity, -nor any symmetrical arrangement. If, as some mineralogists allege, -the curvature, as well as inclination of the strata, arose from the -irregularities of the bottom on which they were deposited, why is the -former in one dimension only, and why is it not in every direction, -like that of hills and valleys, or the actual surface of the earth? -Or, lastly, if the whole structure of the primitive mountains is an -effect of crystallization, and if these mountains are now such as -they have ever been from the time of their consolidation, whence is -it, that, in their bendings the law just mentioned is so constantly -observed? Indeed, the idea of ascribing the inflections of the strata -to crystallization, though suggested by Saussure,[107] and since -become a favourite system with several mineralogists, appears to me -in the highest degree unsatisfactory and illusive. The purpose for -which crystallization is here introduced, is not to give a specific -figure to a particular substance, but to arrange the substances which -it has formed and figured, according to certain rules; a work which -we know not how it is to perform, and in which we have no experience -of its power. Accordingly, this principle does not account, in any -way whatever, for the circumstances which attend the inflection of -the strata, for the simple curvature which they affect, nor for that -parallelism of their layers, which, in all their bendings, is so -accurately preserved. It does, indeed, so little serve to explain -these facts, that, were the appearances completely reversed; did the -strata assume the most complex, instead of the most simple curvature; -instead of equidistant, were they converging, or alternately receding -and approaching to one another; the theory of crystallization might -be equally applied to them. The state of the phenomena is a matter of -perfect indifference to such a theory as this; all things are explained -by it with the same facility; the straight and the crooked, the square -and the round, the moveable and the immoveable. Is it not evident that -such an explanation is a mere word; or, if any thing more than a word, -an expression of our ignorance, so awkward and indirect, as to deprive -us of whatever credit might have been gained by a plain and candid -avowal of it? - -[Footnote 107: Voyages aux Alpes, tom. i. § 475.] - -It should never be forgotten, that a theory which accounts for _any -thing_, and a theory which accounts for _nothing_, stand precisely -on the same footing, and ought to be banished from all parts of -philosophy, as they have been from those sciences which are justly -honoured with the name of accurate. The animated orbs of Aristotle, -and the vortices of Des Cartes, have long ceased to be mentioned in -physical astronomy; the first, because, they accounted for every thing -alike; the second, because, when they accounted for one thing, they -never could be made to account for another. Both theories, therefore, -have very properly been rejected; and, when geology shall undergo a -similar purification, the principle we have been considering will not -be the only sacrifice required of the Neptunian system. - -209. An appearance observed in some kinds of primary schistus, which -clearly indicates their deposition by water, and in planes very -different from those in which we now see them, though it might have -been introduced before, is also much connected with the present -argument. This appearance consists of small wavings or undulæ on the -surface of the plates of schistus, precisely similar to these marks -which are left by the sea on a gently inclining beach of sand, at the -ebbing of the tide. All the species of schistus do not seem to afford -instances of these wavings. The rocks which do so, are, I think, -chiefly of the argillaceous kind, but often highly indurated; so that -the laminæ containing the impressions are not to be torn asunder but -with great difficulty. Instances of it abound in the schistus of -Berwickshire, and are also not unfrequent in that of Galloway. All must -agree about the agent which produced these marks; it could be no other -than the sea; but it must have been the sea acting on loose, small and -round particles, lying on a surface which was nearly horizontal. - -210. Dr Hutton's theory is no where stronger, than in what relates -to the elevation and inflection of the strata; points in which all -others are so egregiously defective. The phenomena to be connected -are here extremely various, and even in appearance contradictory: -the horizontally of one part of the strata; the inclined or vertical -position of another; the perfect planes in which one set are extended; -the breaking and dislocation found in a second; the inflection and -sinuosity of a third; and almost every where the utmost rigidity and -induration, combined with appearances of the greatest softness and -flexibility; the preservation of a parallelism of superficies in the -midst of so much irregularity, and the assumption of a determinate -species of curvature, under circumstances the most dissimilar; all -these appearances were to be connected with one another, and with -the consolidation of the strata, and this is done by the twofold -hypothesis, of aqueous deposition, and the action of subterraneous -heat. When these circumstances are fairly considered, and when the -shifts which other systems are put to on this occasion are remembered, -I think it will be granted, that few attempts at generalization have -been more successful, than that which has been made by the Huttonian -Theory. - -211. To the fact of the elevation of the strata, the study of geology -is much indebted. The stratified form of a great proportion of the -earth's surface, gives to minerals that organization and regularity, -which makes their disposition an object of science, and their inclined -position serves to bring that organization into view, from far greater -depths than we can ever reach by artificial excavations. If, for -instance, the termination of strata, that make with the horizon an -angle of 30°, lying one over another, is seen for a horizontal distance -of two miles; then it is certain, that if these strata have that extent -under ground, which may be reasonably supposed, the thickness of the -whole mass, measured by a line perpendicular to its stratification, is -half the horizontal distance, or amounts to one mile. It would also -require a pit to be sunk from the uppermost of these strata, to the -depth of (2 miles × tan 30°, =) 6093 feet before it could intersect the -undermost; and therefore, if we suppose the same stratum to preserve -the same character for the extent of some miles, we obtain the same -information from inspecting the edge-seams, and see in reality as far -into the bowels of the earth, as if we had sunk a perpendicular shaft -to the depth of 6000 feet. - -In general, the length of the horizontal line drawn across the strata, -from the lowest in position to the highest, multiplied into the sine of -the inclination of the strata to the horizon, gives the thickness of -the whole, measured perpendicularly to the plane of the stratification: -and the same horizontal distance, multiplied into the tangent of the -inclination, gives the actual depth at which the lowest stratum would -meet a perpendicular to the horizon, drawn from the highest extremity -of the upper stratum. - -In many cases, the extent of stratified materials admitting of such -an examination as this, is much greater than has now been supposed. -M. Pallas describes a range of hills on the south-east side of the -peninsula of the Tauride, which is cut down perpendicularly toward the -sea, and offers a complete section of the parallel beds of a primary, -or, as he calls it, an ancient limestone, inclined at an angle of -45° to the horizon; and this section continues for the length of 130 -_versts_, or about 86 English miles. The beds are so regular, that M. -Pallas compares them to the leaves of a book.[108] The height of these -hills does not exceed 1200 feet, but the real height of the uppermost -stratum above the undermost, is 86 × √1/2 = 86 × 5/7 = 61 miles nearly. - -[Footnote 108: See Nova Acta Acad. Petropol. tom. x. (1792,) p. 257.] - -If therefore we conceive that there is no shift in all this great -system of strata, we in reality are enabled, by means of it, to see no -less than 61 miles into the interior of the earth, nearly a 65th part -of the radius of the globe. It is true, that we can hardly suppose so -great a body of strata to have been raised without shifting, so that -we must diminish this depth considerably; but were it reduced even to -one-half it will appear, that men see much farther into the interior -of the globe than they are aware of, and that geologists are reproached -without reason for forming theories of the earth, when all that they -can do is but to make a few scratches on its surface. Art indeed can do -little more; but nature supplies the deficiency, and makes discoveries -to the attentive observer, on the same great scale with her other -operations. - -The simplest account that can be given of the vast body of parallel and -highly inclined strata just mentioned, is, that it consists of the ends -of horizontal strata, or of strata not greatly inclined, that have been -forced up when they were all soft and flexible. This is a much more -conceivable supposition than Pallas's, viz. that the greater part of -this mass has sunk down into some vast cavern in the interior of the -earth. - - - - - NOTE XIII. § 53. - - _Metallic Veins._ - - -212. The large specimens of native iron found in Siberia and Peru, -mentioned above, § 51, are among the most curious facts in the natural -history of metals. It has been doubted, however, by some, whether they -really belong to natural history, or are not rather to be accounted -artificial productions. If they had been found in the heart of rocks, -or in the midst of metallic veins, no doubt of this sort could possibly -have been entertained; but, as they lie quite on the surface, in the -middle of flat countries, and at a distance from any known vein of -metal, the conjecture that they may be artificial, and the remains of -the iron founderies of ancient and unknown nations, is at first sight -not entirely destitute of probability. This probability, however, will -appear to be the less, the more carefully the specimens are examined. -The metal is too perfect, and the masses too large, to have been melted -in the furnaces, or to have been transported by the machinery, of a -rude people. The specimen in South America weighs 300 quintals, or -about 15 tons, and is soft and malleable.[109] The Siberian specimen, -described by Pallas, is also very large; it is soft and malleable, and -full of round cavities, containing a substance, which, on examination, -has been found to be chrysolite.[110] Now, it is certainly quite -impossible, that, in an artificial fusion, so much chrysolite could -have come by any means to be involved in the iron; but, if the -fusion was natural, and happened in a mineral vein, the iron and the -chrysolite were both in their native place, and their meeting together -has nothing in it that is inexplicable. - -[Footnote 109: Phil. Trans. 1788, p. 37. also p. 183, &c.] - -[Footnote 110: Kirwan's Mineralogy, vol. ii. art. Native Iron.] - -213. Some circumstances in the description of the specimen in South -America, such as the impressions of the feet of men and of birds on its -surface, are not to be accounted for on any hypothesis, and certainly -require more careful investigation. It is said, that this iron is -very little subject to rust, and the analysis of a piece of it by -PROUST makes it probable, that it owes this quality to its union with -nickel.[111] It appears, also, that the country of Chaco, where this -specimen was found, affords many others of the same kind, one of which -is mentioned in the description above referred to. That country lies -on the east side of the Plata, and is a plain extremely level, and of -vast extent, without any appearance of mineral veins; but such veins -may nevertheless exist undiscovered, in a tract subject to periodical -inundations, and where the native rock is covered with alluvial earth -and gravel to a great depth. The veins maybe washed away, and the more -durable substances, such as those pieces of native iron, may be left -behind; and, though they must be of a formation extremely ancient, -according to this hypothesis, they may not have been very long on the -surface. - -[Footnote 111: Annales de Chimie, tom. xxxv. Messidor, p. 47.] - -214. Specimens of native iron have been found, less remarkable than -the preceding for their size, but in circumstances that excluded -all idea of artificial fusion. Of this sort was MARGRAAF'S specimen -of native iron, the first of the kind that was known; it consisted -of small bits of soft and malleable iron, found in the heart of a -brown iron-stone.[112] This makes it certain, that native iron is a -natural production, and the mere circumstance of great magnitude, in -the specimens before mentioned, does not entitle us to doubt of their -having that same origin. It is a circumstance, besides, not in the -least material to this argument; the smallest piece of native iron -being as much a proof of fusion as the greatest; and the specimen -of Margraaf being just as conclusive in favour of the Huttonian -Theory, as those of Pallas or De Celis, supposing their reality in -mineral productions to be completely established. À metal malleable -and ductile, in ever so small a quantity, cannot be the result of -precipitation from a menstruum, without a very particular combination -of circumstances. Such a metal, can the other hand, can be readily -produced by igneous fusion; so that here the negative and affirmative -parts of the inductive argument may both be regarded as complete. - -[Footnote 112: Kirwan's Mineralogy, vol. ii. p. 156.] - -215. Mr Kirwan, in order to account for the magnitude of the two large -specimens mentioned above, supposes, that small pieces of native iron -(about the formation of which he appears to have no difficulty) have -been originally agglutinated by petroleum, and left bare, when the -surrounding stony or earthy masses either withered or were washed -off.[113] This is no doubt the most singular of all the opinions which -have been advanced on the subject; and, as it borrows nothing from -analogy, it admits of no proof, and requires no refutation. None but a -chemist of eminence could have ventured with impunity on an assertion -so inconsistent with all the phenomena and principles of his science. - -[Footnote 113: Geol. Essays, p. 405.] - -216. A remark of the same author, on the subject of the native gold -found in the county of Wicklow in Ireland, is entitled to more -attention. "That these lumps of native gold," he says, "were never in -fusion, is evident from their low specific gravity, and the grains of -sand found in the midst of them. I found the specific gravity of a lump -of the size of a nutmeg to be only 12800, whereas, after fusion, it -became 18700."[114] - -[Footnote 114: _Ibid._ p. 402.] - -This argument is plausible; but, I think, nevertheless inconclusive. -The sand found in the gold, accounts, at least in part, for its -lightness. It is only by repeated fusions that any of the metals is -brought to its utmost purity and highest specific gravity; and on no -supposition can the melting of gold in the mineral regions, be very -likely to separate it from heterogeneous substances. That quartzy -sand should be found in it, after such a process, is naturally to be -expected. The impressions which the quartz crystals have left on the -Wicklow gold, would be received as a full proof of the fusion of that -metal, if geologists always regulated their theories by the principles -which determine the belief of ordinary men. - -217. Don Rubin de Celis, in the paper referred to above, mentions some -masses of silver found at Quantajaia, and also some dust of platina, in -terms that excite a strong desire to have more information concerning -them. They are considered by him as effects of volcanic fire; so we -may conclude, that they contain evident marks of fusion, and would in -this system be ascribed to that heat, from which volcanic fire is but a -partial and accidental derivation. - -218. The state also in which gold and silver are often found pervading -masses of quartz, and shooting across them in every direction, -furnishes a strong argument for the igneous origin, both of the metal -and the stone. From such specimens, it is evident, that the quartz -and the metal crystallized, or passed from a fluid to a solid state, -at the same time; and it is hardly less clear, that this fluidity did -not proceed from solution in any menstruum: For the menstruum, whether -water or the _chaotic fluid_, to enable it to dissolve the quartz, -must have had an alkaline impregnation; and, to enable it to dissolve -the metal, it must have had, at the same time, an acid impregnation. -But these two opposite qualities could not reside in the same subject; -the add and alkali would unite together, and, if equally powerful, -form a neutral salt, (like sea-salt,) incapable of acting either on -the metallic or the siliceous body. If the acid was most powerful, the -compound salt might act on the metal, but not at all upon the quartz; -and if the alkali was most powerful, the compound might act on the -quartz, but not at all on the metal. In no case, therefore, could it -act on both at the same time. Fire or heat, if sufficiently intense, -is not subject to this difficulty, as it could exercise its force with -equal effect on both bodies. - -219. The simultaneous consolidation of the quartz and the metal is -indeed so highly improbable, that the Neptunists rather suppose, that -the ramifications in such specimens as are here alluded to, have been -produced by the metal defusing itself through _rifts_ already formed -in the stone.[115] But it may be answered, that between the channels -in which the metal pervades the quartz, and the ordinary cracks or -fissures in stones, there is no resemblance whatever: That a system of -hollow tubes, winding through a stone, (as the tubes in question, must -have been, according to this hypothesis, before they were filled by -the metal,) is itself far more inconceivable than the thing which it -is intended to explain; and lastly, that if the stone was perforated -by such tubes, it would still be infinite to one that they did not all -exactly join, or inosculate with one another. - -[Footnote 115: Geol. Essays, p. 401.] - -220. The compenetration, as it may be called, of two heterogeneous -substances, has here furnished a proof of their having been melted by -fire. The inclusion of one heterogeneous substance within another, -as happens among the spars and drusens, found so commonly in mineral -veins, often leads to a similar conclusion. Thus, from a specimen of -chalcedony, including in it a piece of calcareous spar, Dr Hutton -has derived a very ingenious and satisfactory proof, that these two -substances were perfectly soft at the same time, and mutually affected -each other at the moment of their concretion.[116] - -[Footnote 116: Theory of the Earth, vol. i. p. 93.] - -Each of these substances has its peculiar form, which, when left to -itself, it naturally assumes; the spar taking the form of rhombic -crystals, and the chalcedony affecting a mammalated structure, or a -superficies composed of spherical segments, contiguous to one another. -Now, in the specimen under consideration, the spar is included in the -chalcedony, and the peculiar figure of each is impressed on the other; -the angles and planes of the spar are indented into the chalcedony, -and the spherical segments of the chalcedony are imprinted on the -planes of the spar. These appearances are consistent with no notion of -consolidation that does not involve in it the simultaneous concretion -of the whole mass; and such concretion cannot arise from precipitation -from a solvent, but only from the congelation of a melted body. This -argument, it must be remarked, is not grounded on a solitary specimen, -(though if it were it might still be perfectly conclusive,) but on a -phenomenon of which there are innumerable instances. - -221. According to this theory, veins were filled by the injection of -fluid matter from below; and this account of them, which agrees so -well with the phenomena already described, is confirmed by this, that -nothing of the substances which fill the veins is to be found any where -at the surface. It is not with the veins as with the strata, where, in -the loose sand on the shore, and in the shells and corals accumulated -at the bottom of the sea, we perceive the same materials of which these -strata are composed. The same does not equally hold of metallic veins: -"Look," says Dr Huston, "into the sources of our mineral treasures? Ask -the miner from whence has come the metal in his veins? Not from the -earth or air above, not from the strata which the vein traverses: these -do not contain an atom of the minerals now considered. There is but -one place from whence these minerals may have come; this is the bowels -of the earth; the place of power and expansion; the place from whence -has proceeded that intense heat, by which loose materials have been -consolidated into rocks, as well as that enormous force, by which the -regular strata have been broken and displaced."[117] - -[Footnote 117: Theory of the Earth, vol. i. p. 130.] - -222. The above is a very just and natural reflection; but if, instead -of interrogating the miner; we consult the Neptunist, we will receive -a very different reply. As this philosopher never embarrasses himself -about preserving a uniformity in the course of nature, he will tell -us, that though it may be true, that neither the air, the upper part -of the earth's surface, nor even the sea, contain at present any thing -like the materials of the veins, yet the time was when these materials -were all mingled together in the chaotic mass, and constituted one -vast fluid, encompassing the earth; from which fluid it was, that the -minerals were precipitated and deposited in the clefts and fissures of -the strata. - -223. It is alleged, in proof of this hypothesis, that mineral veins are -found to be less rich as they go farther down, whereas they ought to -be richer if they were filled by the projection of melted matter from -below. But the fact, that mines are less rich as they descend farther, -though it may hold in some instances, is not general, and may therefore -be supposed to arise from local causes, such as are, in respect of us, -accidental, and beyond the limits to which our theories can be expected -to reach. Thus the mines of Mexico and Peru are said to be subject -to the preceding rule; but in the mines of Derbyshire and Cornwall, -the very contrary is understood to take place. Besides, what we are -pleased to call the riches of a mine, are riches relatively to us, and -relatively to a distinction which nature does not recognise. The spars -and veinstones which are thrown out in the rubbish of our mines, may be -as precious in the eyes of nature, as conducive to the great objects -of her economy, and are certainly as characteristic of mineral veins, -as the ores of silver or gold, to which we attach so great a value. -Unless the former are in smaller quantity, or less highly crystallized -at great than at small depths, which I believe is not alleged, no -conclusion can be drawn from substances, which occupy in general but a -small proportion of any vein, and, in their dissemination through it, -do not seem to be always guided by the same law. - -224. Again, if the veins were filled by deposition from above, we ought -to discover in them such horizontal stratification as is the effect of -deposition from water, and we should perceive no marks of the materials -having been introduced with violence into their place. The Neptunists -cannot object to the trial of their theory by these two frets. - -As to the first, it is acknowledged, that there is a certain regular -disposition of the substances in mineral veins, as stated § 59, but it -is one which has hardly any thing in common with the real phenomena -of stratification. It consists in the distribution of the principal -substances in coats parallel to the sides of the vein, each substance -forming a separate coat. In a vein, for instance, containing quartz, -fluor, calcareous spar, lead, &c. we might expect to find a lining of -quartz crystals, applied immediately to the walls of the mine, and -following exactly the irregularities of their surface; next, perhaps, -a coat of fluor, then of calcareous spar, and last of lead ore in the -centre of the vein, the same order being observed on the opposite -side. These successive coats, it is material to remark, are not in -planes, but in uneven surfaces, of which the inequalities are evidently -determined by those of the walls, that is, of the rock which forms -the sides of the vein; neither are they horizontal, but are parallel -to the walls, whether these be perpendicular or inclined. Here, -therefore, there is no appearance of the action of that statical law -which has directed the arrangement of the other strata, and which tends -to make the plane of every stratum deposited by water perpendicular -to the direction of gravity. The coating of the veins has therefore -been performed under the conduct of some other power than that which -presides over aqueous deposition. If, as the Neptunists maintain, the -materials in the veins were deposited by water, in the most perfect -tranquillity, it is wonderful that we do not find those materials -disposed in horizontal layers, across the vein, instead of being -parallel to its sides; and it seems very unaccountable, that the common -strata, deposited as we are told while the water was in a state of -great agitation, have so rigorously obeyed the laws of hydrostatics, (§ -38.) and acquired a parallelism in the planes of their stratification, -which approaches so often to geometrical precision; while the materials -of the veins, in circumstances so much more favourable for doing the -same, have done nearly the reverse, and taken a position, often at -right angles to that which hydrostatical principles require. This is a -paradox which the Neptunian system has created, and which therefore it -is not very likely to resolve. - -225. Mere words should have little power to mislead, in a science which -treats of sensible objects, such as are always easily subjected to the -examination of sight or of touch; yet there is some appearance as if -the Neptunists were misled in this, and other instances, by the term -_stratification_. Though an incrustation on the perpendicular face of a -rock has very little affinity to a stratum, such as we are accustomed -to see deposited by water, yet the same name being once imposed on -both, mineralogists have proceeded to reason concerning them, as if -they were precisely the same thing, and were both to be ascribed to -the same cause. Indeed every perpendicular or highly inclined bed of -stone, is inexplicable as an effect of aqueous deposition, in a system, -unprovided, as the Neptunian is,[118] with the means of raising up -such beds from a horizontal into a vertical position. This observation -may also be extended to all cases of vertical stratification. Water -cannot directly arrange its deposits in planes highly inclined, and -therefore I have often wondered to see the Neptunists contending so -eagerly for the stratification of certain rocks, such as granite, -which, being vertical, or highly inclined, was much less friendly to -their system than the entire absence of all stratification would have -been. I was disposed to admire their candour, when the use which -they made of the fact convinced me, that I ought only to wonder at -their inconsequential reasoning. The Huttonian Theory is, indeed, the -only one which possesses the means of reconciling the elevation of -the strata with their horizontal deposition, and which is entitled to -consider stratification, in whatever plane it may be, as originally the -work of the ocean. The geologists who attach themselves exclusively to -the action of water, will never be able to extend the dominion of that -element so far as Dr Hutton has done, by combining it with fire. - -[Footnote 118: See preceding note.] - -226. But, though the Neptunian system were provided with engines, -powerful enough to raise up strata from a level to a vertical plane, -this would avail nothing in the present instance; since, on no -supposition, can the incrustations on the perpendicular sides of a -vein have ever been horizontal. On no supposition, therefore, can -these incrustations be received as a proof of aqueous deposition: it -may indeed be certainly inferred from them, that the matter which they -consist of was fluid at the time of their formation; but the absence of -all appearance of a horizontal disposition, in any part of the vein, -amounts nearly to a demonstration, that this fluidity did not proceed -from solution in a menstruum. We must therefore conceive the coats -to have been formed during the refrigeration of the melted matter -injected from the mineral regions into the clefts and fissures of the -strata. (§ 59.) - -227. Mineral veins, particularly at their intersections with one -another, contain abundant marks of the most violent and repeated -disturbance (§ 56.). Not to mention that they owe their first formation -to the fracture and displacing of rocks already consolidated, it -appears, that they have originated at very different periods, and that -the birth of each has been accompanied with convulsions, which shook -the foundations of the earth. In Cornwall, for instance, the principal -veins, and those which they distinguish particularly by the name of -_Lodes_, have nearly the same direction with the strata or vertical -schistus, extending from about E. N. E. to W. S. W. These, however, -are often intersected nearly at right angles by other mineral veins, -called _Cross Courses_, and this hardly ever happens without the latter -moving, or, as it is called, heaving the former out of their direction. -This plainly indicates, that the cross courses are of later origin -than the others, and that their formation was accompanied with such a -force, as must, in many substances, have moved the whole body of rock -which constitutes the promontory of Cornwall, and probably much more, -for several yards, in a horizontal direction. Sometimes, also, both -the longitudinal and the cross vein are forced out of their place by -a third. These disturbances arise not only from mineral veins, but -from veins of porphyry and granite, the production of which has been -attended with no less violence than of the others. - -228. What is here said of Cornwall, is the history, in some degree, -of all mineral countries whatever. The great horizontal _translation_ -which has thus accompanied the formation of veins; the movement -impressed on such vast bodies of rock, and the frequent renewal of -these immense convulsions; are not to be explained by the mild and -tranquil dominion of the watery element. They require the utmost power -that is known any where to exist, and were it not for the admonitions -of the volcano and the earthquake, we might doubt if even subterraneous -heat itself possessed an energy adequate to these astonishing effects. - -229. From the _heaving_ of one vein by another, it is evident, that -there was a force of protrusion in the direction of one of them, that -acted at the time of its formation. This force cannot be accounted -for on the supposition that veins were produced by the mere shrinking -of the strata; for the rocks could not, in that case, have been rent -asunder, and impelled forward at the same time. It appears most likely, -that fissures in the strata were made, at least in many instances, -and the matter poured into them, nearly at the same time, both being -effects of the same cause, the expansive force of subterraneous heat. - -230. It is remarked, at § 56, that the shifting of the strata is best -observed where the veins make a transverse section of beds of rock, -considerably inclined to the horizon. It is also true, that in some -cases the near approach of the strata to the level, may make the shifts -produced by the veins very easy to be discovered. Thus in Derbyshire, -where the mineral veins are in secondary strata, nearly horizontal, -there is almost no instance in which the corresponding strata are not -observed to be on different levels, on the opposite sides of the same -vein. - -231. The fact described by De Luc, and referred to at § 55, may, for -what we know of it, admit of being explained in two ways. The great -wedge of rock which appears to be insulated between two branches of the -same vein, may either be a mass that has been broken off, and sustained -by the melted matter that flowed all around it; or, it may be a mass -of rock contained between two veins that are in reality distinct, and -of different formation. Whether this last supposition is the truth, -would probably be evident from a careful examination of both parts -of the vein; as some difference of character cannot fail to be the -consequence of different formation. If no such difference is observed, -the two branches must be supposed to belong to the same vein, and the -only probable explanation of the insulation of so large a mass of rock -will be by the first mentioned supposition. This fact, therefore, -notwithstanding the great attention M. De Luc has bestowed on it, -still requires further examination, before it can be decided whether -it inclines to the Huttonian Theory, as on the first supposition, or -is, as on the latter hypothesis, equally balanced between it and the -_Wernerian_. - -232. Whatever be the case with this fact, the general one of pieces of -rock being found insulated in veins, is certainly favourable to the -notion of an injected and ponderous fluid having originally sustained -them. Where, as happens in some instances, the stones contained in -the veins have no affinity to any of the rocks above, they cannot -be supposed to have come any how but from below, and to have been -carried up by the matter of the vein. The instance from the slip at the -Huddersfield Canal has been already mentioned. - -233. The preceding observations have been principally directed against -that theory of veins which supposes them to have been filled by -deposition from water. There is another theory maintained by some -of the Neptunists, that the metals in veins were introduced there by -infiltration.[119] This opinion is sufficiently refuted by the fact, -that rarely any metallic ore is found out of the vein, or in the rock -on either side of it, and least of all where the vein is richest. -This is inconsistent with the notion of the ore being carried into -the vein by water percolating through the adjacent rocks, unless some -satisfactory reason is assigned, which determined the water to leave -the ore in the vein and no where else. Besides, this hypothesis does -not account for the formation of the spars and veinstones which fill -the vein, and which appear clearly to have been brought there at the -same time with the ore, and no doubt by the same cause. - -[Footnote 119: Geol. Essays, p. 401.] - -234. The veins, properly so called, are indefinitely extended; but -there are also thin plates of spar, and of crystals of different kinds, -often found included in rocks, and shut in on all sides, to which the -name of veins is commonly applied. These last ought certainly to be -distinguished from the former, and may not improperly be called _Plate -Veins_ or _Lenticular Veins_, the plate or cake of spar of which they -consist having very often the form of a lens, though, as may be -supposed, considerably irregular. Either of these terms being derived -entirely from external characters, has the advantage of involving -nothing theoretical. - -The lenticular veins are certainly not formed like the usual mineral -veins, by injection, since they are shut in, on all sides, by the solid -rock. When they are found, therefore, in stratified rocks, such as -have not themselves been melted, we must conceive them to be composed -of materials more fusible than the surrounding rock, so that they -have been brought into fusion by a degree of heat which the rest of -the rock was able to resist, and, on cooling, have assumed a sparry -structure. When they are found in rocks, of which the whole has been -fluid, they must be considered as component parts of that mass, which, -by an elective attraction, have united with one another, and separated -themselves from the substances to which they had less affinity. - -The veins of this kind seem to be connected with those called in -Derbyshire _Pipe Veins_, in which the ores of metals are sometimes -found. The pipe veins, indeed, are not in all cases completely -insulated, but sometimes communicate with the veins properly called -mineral. I am too little acquainted, however, with their natural -history, to Be able to say with certainty to which of the two species -they ought to be referred. - - - - - NOTE XIV. § 75. - - _On Whinstone._ - - -235. To the facts and reasonings given above, I shall, in this note, -add a few remarks, tending to show, that whinstone is not of volcanic, -nor of aqueous, but certainly of igneous origin. - -It is asserted, (§ 62,) that carbonate of lime and zeolite are often -contained in whinstone, but never in lava, and that this circumstance -may sometimes serve to distinguish these stones from one another. With -respect to carbonate of lime, in particular, it seems evident, that -this substance cannot enter into the original composition of any lava, -because the same heat which melted the lava, would, where there was no -greater pressure than the weight of the atmosphere, expel the carbonic -acid and produce quicklime. Notwithstanding this, rocks containing -carbonate of lime, have often been considered as lavas, into the pores -and cavities of which, calcareous matter having been carried by the -infiltration of water, had crystallized into spar. Thus SPALLANZANI, -in his account of the Euganean Hills, in Lombardy, describes some of -the rocks as abounding at their surface, and even in their interior, -with air-bubbles of various sizes, from such as are hardly perceptible, -to some that are half an inch in diameter; and which, he says, are all -of an oval figure, with their longest diameters in the same direction. -This he considers as a proof that the rock is a genuine lava; for the -air-bubbles prove the stone to have had its fluidity from fire; and -by their elongation in the same direction they prove, that the mass -when fluid was also in motion. Spallanzani adds, that _many of these -cavities are filled with crystals of the carbonate of lime, an effect -of the infiltration of water_.[120] - -[Footnote 120: Voyages dans les deux Siciles, tom. iii. p. 157. Edit. -de Faujas de St Fond.] - -236. Though the argument here advanced for the igneous origin of the -rock may be admitted as conclusive, the introduction of calcareous -spar into it by infiltration must still be questioned. Lava, except -in a state of decay or decomposition, is not readily penetrated by -water; and, if it were, the filling of cavities with spar, by means -of the water percolating through them, would still be subject to many -difficulties, (§12.). Besides, whinstone rocks are frequently found so -full of calcareous spar, or of zeolite, that they would become porous -to such a degree, if the cavities filled with these latter substances -were all empty, that they could hardly sustain their own weight, and -much less that of the great masses of rock incumbent on them. In such -cases, it is certain, that the crystallized substances were part of the -original composition of the rock. The truth is, that the infiltration -of the water is a mere gratuitous assumption, introduced for the -purpose of explaining the existence of carbonated lime in a stone which -had endured the action of intense heat: and this assumption ought of -course to be rejected, if the phenomenon can be explained by a theory, -that is in other respects conformable to nature. The spar, then, may be -considered as a proof, that the rocks in question are to be numbered -with those unerupted lavas which have flowed deep in the bowels of the -earth, and under a great compressing force. This is the more probable, -that the Euganean Hills, like some whinstone hills in our own country, -have, in certain places, a covering of slaty and calcareous strata -incumbent on them, even at their summits,[121] so that the torrent of -melted stone, of which they are admitted to consist, cannot have flowed -from the mouth of a volcano. I do not mean to say, that there are -among these hills no vestiges of volcanic explosion. I am very far from -having _data_ sufficient for drawing this conclusion; but I believe it -may be safely affirmed, that the bulk of them is no more composed of -volcanic lava, than the basaltes of Staffa, or of the Giant's Causeway. - -[Footnote 121: Phil. Trans. 1775, p. 34.] - -237. But, besides the evidence deduced from calcareous spar and -zeolite, against the rocks containing them being real lava, there are -other marks, even less equivocal perhaps, that distinguish the lavas -which we suppose to have flowed in the mineral regions, from those -which have actually flowed on the surface. These are what we collect -from the disposition, the organization, or, as we may say, the physical -geography of whinstone countries, unlike, in so many respects, to that -of volcanic countries. The shape of whinstone hills; their large flat -terraces, rising one above another; their perpendicular faces, and the -correspondence of their heights even at considerable distances; have -nothing similar to them in the irregular torrents of volcanic lavas. -The phenomena of the former are also on a scale of magnitude very far -exceeding the latter, and clearly indicate, that though both have been -produced by fire, it has been by fire in very different circumstances, -and regulated by very different laws. The structure of the two kinds -of rock agrees, in many respects, and so does their chemical analysis; -but their disposition and arrangement are so dissimilar, that they -cannot be supposed to be of the same formation. - -238. This argument, I believe, was first stated by Mr Strange, in -a letter to Sir JOHN PRINGLE, published in the 65th volume of the -_Philosophical Transactions_.[122] That intelligent observer, after -visiting the countries in Europe most remarkable either for burning, -or for what are accounted, extinguished volcanoes, and examining them -with a very discriminating eye, remained convinced, that there are two -distinct species of rock, which both owe their origin to fire; but -to fire acting in circumstances and situations extremely different. -The first is the common volcanic lava; the other, to which he gives -the name of a basaltine rock, comprehends such rocks as the Giant's -Causeway, the basaltes of the Vivarais, of the Euganean Hills, &c. -and differs in nothing from that which is called here by the name -of whinstone. Mr Strange conceived, that the one of these kinds of -stone could, no more than the other, be accounted the work of aqueous -deposition, but was led to the distinction just mentioned, by observing -the organization and arrangement in the rocks of the latter kind, and -comparing them with the disorder and ruin that every where mark the -footsteps of volcanic fire He does not pretend to determine the nature -of the fire to which the basaltine rocks owe their formation, nor the -circumstances in which it has acted: he is satisfied with the negative -conclusion, that it is not volcanic; and his paper affords a specimen -of what is perhaps rare in any of the sciences, and certainly most rare -of all in geology, viz. a philosophic induction carried just as far as -the facts will bear it out, and not a single step beyond that point. - -[Footnote 122: Account of Two Giants' Causeways in the Venetian State, -&c. by John Strange, Esq. Phil. Trans. vol. lxv. (1775,) p. 5, &c.] - -239. Several other hints contained in this paper are highly deserving -of notice; for we not only find in it the notion of a formation of -basaltic rocks, igneous though not volcanic, but also that of their -simultaneous crystallization,[123] together with the suggestion, that -granite and basalt are of the same origin,[124] These opinions had not, -I believe, occurred at that time to any mineralogist except Dr Hutton, -nor had they been communicated by him to any but a few of his most -intimate friends; so that Mr Strange has without doubt all the merit -of a first discoverer. Indeed, without the knowledge of the principle -of compression, such as it is laid down by Dr Hutton, it was hardly -possible for him to proceed further than he has done. He remarked -the unburnt limestone that lies on the tops of some of the Euganean -basaltes, and seems to have been aware of the great difficulty, which -it was reserved for the Huttonian Theory to overcome. His letter -contains also some excellent general remarks on the rocks of the -Vivarais and Velay, which he had visited, before FAUJAS DE ST FOND had -published his curious and elaborate description of these countries. - -[Footnote 123: Phil. Trans, _ubi supra_, p. 17.] - -[Footnote 124: _Ibid._ p. 36 and 37.] - -240. The cause of the peculiar structure which has just been observed -to distinguish whinstone from volcanic countries, is easily assigned -in the Huttonian Theory. According to that theory, the whinstone rocks -were formed, in the bowels of the earth, of melted matter poured into -the rents and openings of the strata. They were cast, therefore, -in those openings, as in a mould; and received the impression and -character of the rocks by which they were surrounded. Hence the tabular -masses of whinstone, which when soft have been interposed between -strata, and compressed by their weight, so as almost to have themselves -acquired the appearance of stratification. Hence the perpendicular -faces of the same rocks, produced by their being abutted when yet -soft, against the abrupt sides of the strata. The rocks which formed -those moulds have, in many cases, entirely disappeared; in others, a -part still remains, surrounding, or even covering, the basaltes, as in -the Euganean Hills, in those of the Val di Noto in Sicily, the rocks -near Lisbon,[125] and in different parts of Great Britain. - -[Footnote 125: Recherches sur les Volcans Eteints du Vivarais; Lettre -du Dolomieu, p. 443.] - -Above all, the veins of whinstone which intersect the strata, are the -completest proofs of the theory here given of these rocks, and the most -inconsistent, in all respects, with the hypothesis of their volcanic -origin. - -241. If these _criteria_ are applied to what are called extinguished -volcanoes, I have no doubt that many which have been reckoned of that -number, will be found to derive their origin more directly from the -fire of the mineral regions. The basaltic rocks of the Vivarais, I am -well persuaded, belong to this class; and I conclude that they do so, -not only from the account of them given by Mr Strange, but from the -description of Faujas himself, who, though under the influence of the -opposite theory, seems very fair and accurate in his description of -phenomena. The most unequivocal mark of real whinstone rock, and of -a formation in the strictest sense mineral, is where veins of that -kind of rock intersect the strata. Now, in a letter to Buffon, on the -streams of lava found in the interior of certain calcareous rocks in -the lower Vivarais, Faujas describes what can be accounted nothing -else but a vein or dike of whinstone, accompanied with several of -its most remarkable and characteristic appearances: "Figurez-vous un -courant de lave, de la nature du basalte noir, dur et compacte, qui a -percé à travers les masses calcaires, et s'est fait jour dans quelques -parties, paroissant et disparoissant alternativement: Cette coulée -de matière volcanique s'enfonce sous une partie de la ville, bâtie -sur le rocher; elle reparoit dans la cave d'un maréchal, se cache et -se montre encore de temps en temps en descendant dans le vallon, &c. -Ce qu'il y a d'admirable, c'est que la lave forme deux branches bien -extraordinaires, dont l'une s'éleve sur la crête du rocher, tandis que -l'autre coupe horizontalement de grands bancs calcaires escarpés, qui -sont à découvert, et bordent le chemin. - -"Quels efforts n'-a-t-il pas fallu pour forcer cette lave se prendre -une telle direction, et se percer cette suite de rochers calcaires? -Si cette longue coulée de lave avoit eu 200 ou 300 toises de largeur, -je ne serois pas surpris qu'un torrent de matière en fusion de ce -volume eut pu produire, des effets extraordinaires et violens; _mais -figurez-vous, Monsieur, que dans les endroits les plus larges, elle n'a -tout-au-plus qu'environ 12 ou 15 pieds; elle n'en a que 3 ou 4 dans -certaines parties_".[126] - -[Footnote 126: Volcains Eteints du Vivarais, p. 328, &c.] - -This narrow stream is to be traced across the strata for more than a -league and a half; and the whole appeared to Faujas so marvellous, -that he says he almost doubted the testimony of his senses. He would -have done much better, however, to have doubted the conclusions of his -theory; for it was by them that the phenomena before him were rendered -so mysterious and incredible. While he continued to regard what is -described above as a stream of melted lava, which had descended from -the top of one mountain, and climbed up the sides of the opposite, like -water in a conduit pipe, piercing occasionally through vast bodies of -solid rock, it is no wonder that he considered as marvellous what is -indeed physically impossible. Had his belief in the volcanic theory -permitted him to see in all this, not a superficial current, but one of -indefinite depth, he would have beheld the object divested, not of what -was curious and interesting, but of what was incredible or absurd, and -reduced to the same class of things with mineral veins. That it belongs -really to this class, and is no more than a vein or dike of whinstone, -intersecting the strata to an unknown depth, and most probably, like -other veins, communicating with the mineral regions, cannot be doubted -by any one who has studied the subject of basaltine rocks, through -any other medium than the volcanic theory. The ramifications which -run from it into the calcareous rock, contrived, Faujas says, just as -if on purpose to perplex mineralogists, is one of the well known and -characteristic appearances of basaltic veins. - -242. It can hardly be doubted, that the lava described by the same -author as heaving up a mass of granite,[127] and including pieces of -it, is a rock of real whinstone. The same may be said of many others; -and, though I pretend not to affirm that there is nothing volcanic in -the Vivarais, I must say, that nothing decidedly volcanic appears in -the description of that country, but many things that are certainly of -a very different origin. - -[Footnote 127: Volcains Eteints du Vivarais, fol. p. 365, &c.] - -In the present state of geological science, a skilful mineralogist -could hardly employ himself better, than in traversing those ambiguous -countries, where so much has been ascribed to the ancient operation -of volcanic fire, and marking out what belongs either clearly to the -erupted or unerupted lavas, and what parts are of doubtful formation, -containing no mark by which they may be referred to the one of these -any more than the other. Such a work would contribute very materially -to illustrate the natural history of the earth. - -243. One of the most ingenious attempts to support the volcanic theory, -is the system of _submarine volcanoes_, imagined by the celebrated -mineralogist DOLOMIEU. The phenomenon that led to this hypothesis, -was what he had observed in the hills near Lisbon, and still more -remarkably in those of the Val di Noto in Sicily, where the basaltine -rocks had regular strata incumbent on them, and in some cases -interposed or alternated with them.[128] It seemed from this evident, -that the strata were of later formation than the stone on which they -rested; and as they must, on every supposition, be held to be deposited -by water, it was concluded, that the lava which they covered had been -thrown out by volcanoes at the bottom of the sea; that the strata had -afterwards been deposited on this lava; and that, in some cases, there -had been frequent alternations of these eruptions and depositions.[129] - -[Footnote 128: Mémoire de Deodate de Dolomieu, sur les Volcains -Eteints du Val di Noto, en Sicile. Journal de Phys. tom. xxv. (1784. -Septembre.) p. 191.] - -[Footnote 129: Near Vizini, in the Val di Noto, Dolomieu tells us, -that he counted eleven beds, alternately calcareous and volcanic, in -the perpendicular face of a hill, which at a distance appeared like a -piece of cloth, striped black and white; _ubi supra_. He has since made -similar observations in the Vicentine and in Tyrol. Journal de Phys. -tom. xxxvii. (1790), partie 2, p. 200.] - -244. Though this hypothesis does certainly deliver the system of -the Volcanists from one great difficulty, it is itself liable to -insurmountable objections. I shall just mention some of the principal. - -1. The regular and equidistant strata that we often see covering the -tops of whinstone or basaltic rocks, could not have been deposited in -the oblique and very much inclined position which they now occupy. - -This is remarkable in the strata which cover the basaltic rock of -Salisbury _Craig_, near Edinburgh, at its northern extremity. The -strata are very regular, and must have been deposited in a plane nearly -horizontal; yet the surface of the basaltes on which they now rest is -very much inclined, dipping rapidly to the north-east. The necessity of -a horizontal deposition in strata, which, though not now horizontal, -have their planes nearly parallel to one another, has been proved at § -38. - -2. If there is any truth in the principles established above, even the -strata themselves have not been consolidated without the action of -fire. By Dolomieu's system, therefore, the consolidation of the strata -which cover the basaltes is not accounted for. - -3. There are no means furnished by the hypothesis of submarine -volcanoes for bringing the basalt, and the strata which cover it, -above the level of the sea. If it is said that the waters of the sea -have been drained off, the objections are all incurred that have been -stated at § 37.[130] If it is said, that the rocks themselves have been -elevated by a force, impelling them upwards, we say, that the existence -of such a force, when admitted, furnishes another means of explaining -the whole phenomenon, namely, that of the injection of melted matter -among the strata, the same that is used in the Huttonian Theory. - -[Footnote 130: Dolomieu adopts this supposition; he thinks, that the -surface of the sea must have been formerly 500 or 600 toises above its -present level. _Ibid._ p. 196.] - -4. The phenomena of basaltic veins are not in the least explained by -the hypothesis of submarine volcanoes. That hypothesis, then, even -if the foregoing objections were removed, does not serve to explain -all the facts respecting the rocks of this genus, and wants, of -consequence, one of the most important characters of a true theory. -It must be allowed, however, that it makes a considerable approach to -such a theory, and that the submarine volcanoes of Dolomieu, have an -affinity to the unerupted lavas of Dr Hutton. - -245. Though in these remarks I have endeavoured to expose the errors -of the volcanic system, I cannot but consider that system as coming -infinitely nearer to the truth than the Neptunian. It has the merit -of distinguishing an order of rocks, which bears no marks of aqueous -formation, and in which the crystallized, sparry, or lava-like -structure, bespeaks their primeval fluidity, and refers their origin -to fire. The Neptunian system, on the other hand, strives to confound -the most marked distinction in the mineral kingdom, and to explain -the formation, both of the stratified and unstratified rocks, by -the operation of the same element. Though chargeable with this -inconsistency, it has become the prevailing system of geology; and the -arguments which support it are therefore entitled to attention. - -246. It will no doubt be thought singular, that the same mineralogist, -whom we have just seen exerting his ingenuity in defence of the -volcanic system, should now appear equally strenuous in defence of the -Neptunian. Though Dolomieu contends for the volcanic origin of some -basaltic rocks, he does not admit that all basaltes is volcanic, nor -even all of igneous formation. Thus he states, that he had examined at -Rome some of the most ancient monuments of art, executed in basaltes, -brought from Upper Egypt, and that he could discover no mark of the -action of fire in any of them.[131] - -[Footnote 131: Journal de Physique, tome xxxvii. (1790,) partie 2, p. -193.] - -On the contrary, he found that some of them consisted of green -basaltes, which changes its colour to a bronze, when exposed even to a -moderate heat, and which therefore, he argues, can never have endured -any strong action of fire. - -The answer to this argument is very plain, if we admit the effects -ascribed by Dr Hutton to the compression which necessarily takes place -in the mineral regions. If indeed the heat in those regions resembled -exactly that of our fires at the surface, it would not be easy to deny -the above conclusion, which therefore certainly holds good against -the volcanic origin of the Egyptian basaltes. But there is no reason -why, under strong compression, the colouring matter of these stones -might not be fixed, and indestructible by heat, though it can be easily -volatilized or consumed when such compression is removed. This argument -then is against the volcanic; but not against what has been called the -_Plutonic_ formation of basaltes. - -247. As to the other marks of fire which Dolomieu sought for and did -not find in the above mentioned stones, we are not exactly informed -in what they consisted. If the crystallized or spathose texture that -belongs to this description of stones was wanting, the specimens were -not to be considered as of the real basaltic or whinstone genus, -whatever their name or history may seem to indicate. If they did -possess that texture, they had the only mark of an igneous origin that -could be expected, supposing that origin to have been in the bowels of -the earth. No part, therefore, of the observations of this ingenious -mineralogist, can be considered as inconsistent with the theory of -basaltic rocks which has been laid down above. - -248. Bergman had before reasoned on this subject precisely in the same -manner, but from better data, as the stones from which he derived -his argument were in their native place: "Trap," says that ingenious -author, (that is whinstone,) "is found in the stratified mountains -of West Gothland, in a way that deserves to be described. The lower -stratum, which is several Swedish miles in circuit, (10-1/2 of these -miles make a degree,) is an arenaceous stone, horizontal, resting on -granite, and having its particles agglutinated by clay. The stratum -above this is calcareous, full of the petrifactions of marine animals, -and above this is the trap. These three kinds of rock compose the -greater part of the mountains just mentioned, though there are some -other beds, particularly very thin beds of marl and of clay, which -separate the middle stratum, both from that which is under it and -over it, and are frequently so penetrated with bitumen that they -burn in the fire. This schistus is black; when burnt it becomes red, -and afterwards, when washed with water, affords alum. How can it be -supposed," he adds, "that the trap has ever been violently heated, -while the shistus on which it is incumbent retains its blackness, which -however it loses by the action even of a very weak fire?"[132] - -[Footnote 132: Bergman de Productis Volcaniis, Opuscula, tom. iii. p. -214, &c.] - -The answer to this argument is already given. The reasoning, as -in the former instance, is conclusive only against the action of -volcanic fire, or fire at the surface; but not against the action of -heat deep in the bowels of the earth, and under the pressure of the -superincumbent ocean. In such a situation, the bituminous schistus -might be in contact with the melted basalt, and yet there might be no -evaporation of the volatile, nor combustion of the inflammable parts. -It does not, however, always happen, that the bituminous substances, or -substances alterable by fire, which are found in contact with basaltes, -are without any mark of having endured the operation of fire. Instances -in which such operation is apparent are given above, § 30; and more -will be added in the conclusion of this note. - -249. The same mineralogist founds another argument for the aqueous -formation of whin or trap on the existence of that stone in the form -of veins, included in primeval rocks: "Invenitur hoc saxum (trap) in -Suecia pluribus locis, sæpeque in montibus primævis, angustas implens -venas, adeo subtilis structuræ, ut particulæ sint impalpabiles, et, dum -niger est, genuinum efficit lapidem Lydium. In hisce montibus, nulla -adsunt ignis subterranei vestigia."[133] - -[Footnote 133: Opuscula, _ubi supra_.] - -The phenomena here described, namely, a vein of compact whinstone -traversing a primary rock, is, without doubt, as incapable of being -explained by the operation of a volcano, as it is by that of aqueous -deposition. It is, however, a most complete proof of the original -softness of the substance of which the veins consist, and affords one -of the strongest possible arguments for such an operation of fire as is -supposed in the present theory. The main arguments, therefore, which -have been proposed as subversive of the igneous origin of basaltes, are -only subversive of their formation by one modification of fire, viz. -of fire acting near the surface; and thus the weapons which directly -pierce the armour of the Volcanist, and inflict a mortal wound, are -easily turned aside by the superior temper of the _Plutonic_ mail. - -250. An argument founded on facts very similar to some of the -preceding, and leading to the same conclusion, is employed by the -mineralogist to whom the Neptunian system owes its chief support. -Werner, in his observations on volcanic rocks and on basaltes, has -rested his proof of the aqueous formation of the latter, on their -interposition between beds of stone in mountains regularly stratified, -and obviously formed by water. He describes an instance of this in the -basaltic hill of _Scheibenberg_; and the facts, though most of them are -not uncommon, are highly deserving of attention. Near the top of this -hill, and above the basaltic rock which composes the body of it, he -tells us, that there was a sand-pit; a circumstance which he appears -to consider as not a little singular. It was, however, at the bottom of -the hill, that he met with the appearances which chiefly attracted his -notice: "First," says he; "or lowest, was a thick bank of quartzy sand, -above that a bed of clay, then a bed of the argillaceous stone called -wacke; and upon this last rested the basaltes." "When I saw," adds he, -"the three first beds running almost horizontally under the basaltes, -and forming its base; the sand becoming finer above, then argillaceous, -and at last changing into real clay, as the argil was converted into -wacke in the superior part; and, lastly, the wacke into basaltes; in a -word, when I found a perfect transition from pure sand to argillaceous -sand, from the latter to a sandy clay, and from this sandy clay, -through many gradations, to a fat clay, to wacke, and at last basaltes, -I was irresistibly led to conclude, that the basaltes, the wacke, the -clay, and the sand, are all of one and the same formation; and that -they are all the effect of a chemical precipitation during one and the -same submersion of this country."[134] - -[Footnote 134: "Combien je fus surpris de voir en arrivant au fond, -un epais _banc de sable quartzeux_, puis au-dessus une _couche -d'argile_, enfin une couche de la pierre argileuse nommée _Wacke_, et -sur celle-ci reposer le _basalte_. Quand je vis les trois premiéres -couches s'enfoncer _presqu' horizontalement sous le basalte_, et former -ainsi sa _base_; le sable devenir plus fin au-dessus, puis argileux, -et se changer enfin en vraie argile, comme l'argile se convertissoit -en wacke dans sa partie supérieure; et finalement la wacke en basalte; -en un mot, de trouver ici une _transition parfaite_ du _sable pur_ au -_sable argileux_, de celui-ci à _l'argile sablonneuse_, et de _l'argile -sablonneuse_, par plusieurs gradations, à l'argile _grasse_, à la -_wacke_ et enfin au _basalte_. - -"A cette vue, je fus sur le champ et irrésistiblement entrainé à -penser, (comme l'auroit été sans doute tout connoisseur impartial -frappé des conséquences de ce phénomène;) je fus, dis je, -irrésistiblement entrainé aux id es suivantes: Ce _basalte_, cette -_wacke_, cette _argile_, et ce _sable, sont d'une seule et même -formation_; ils sont tous l'effet d'une _precipitation par voie humide_ -dans une seule et même submersion de cette contrée; les eaux qui la -couvroient alors transportoient d'abord le _sable_, puis deposoient -l'_argile_, et changoient peu-à-peu leur précipitation en _wacke_, et -enfin en vraie _basalte_.--Journal de Physique, tom. xxxviii. (1791,) -Partie i. p. 415.] - -First, as to the sand on the top of this basaltic hill, it is most -probably the remains of certain sandstone strata that originally -covered the basaltic part, but are now worn away. We are therefore to -consider this as an instance of a basaltic rock, interposed between -strata that are undoubtedly of marine origin. In this, however, there -is nothing inconsistent with Dr Hutton's theory of basaltes; on the -contrary, it is one of the principal facts on which that theory is -founded. It has indeed been argued by some mineralogists, that bodies -thus contiguous must owe their origin to the same element, and that -a mineral substance cannot be of more recent formation than that -which lies above it. But the maxim, that a fossil must have the same -origin with those that surround it, does not hold, unless they have a -certain similarity of structure. It is, for instance, the want of this -similarity, that authorizes us to assign different periods of formation -to mineral veins, and to the rocks in which they are included. - -In a succession of strata, no one can doubt, that the lowest were the -first formed, and the others in the order in which they lie; but, when -between two strata of sandstone or of limestone we find an intermediate -rock, so different as to resemble lava, and to have nothing schistose -or stratified in its composition, the same instrument cannot be -supposed to have been employed in the formation of both; nor is there -any reason why we may not suppose, that the intermediate body was -interposed between the other two, by some action subsequent to their -formation. It was thus that Dolomieu concluded, when he saw a lava-like -stone interposed between calcareous strata in the Val di Noto, that, -though contiguous, these two rocks could not possibly be of the same -formation; and thus far it is certain, that every unprejudiced observer -must agree with him. - -251. But the circumstance on which Werner seems to lay the greatest -stress, is the gradual transition from the sand to the basalt, through -the intermediate steps of clay and wacke; this gradual transition he -considers as a direct proof, that they are all of the same formation. - -A gradual transition of one body into another, can only be said to -take place, when it is impossible to define their common boundary, -or to determine the line where the one begins and the other ends. -Now, if this be the proper notion of gradual transition, I must say, -that after much careful examination, I have never seen an instance, -in which such a transition takes place between whinstone and the -contiguous strata. The _line_ of separation, though in some places -less evident than in others, has, on the whole, been marked out with -great precision; and, though the stones have been firmly united, or, -as one may say, welded one upon another, yet, when a fresh fracture -was obtained, the stratified and unstratified parts have rarely failed -to be distinguished. The fresh fracture is indeed often necessary, for -many species of whinstone get by decomposition a granulated texture at -the surface, so as hardly to be distinguished from real sandstone. - -Some of the kinds of primary schistus also, particularly the -argillaceous, when much indurated, have in their structure a -considerable resemblance to whinstone; they are slightly granular, or -laminated, and have a tendency to a sparry texture. Where it happens -that this sort of schistus and whinstone are contiguous, it is natural -to expect, that their common boundary will be traced with difficulty, -and in many parts will be quite uncertain. Still, however, if a careful -examination is made; if the effects of accidental causes are removed; -and, above all, if the more ambiguous instances are compared with the -more decisive, and interpreted by them, though single specimens may be -doubtful, we will hardly ever find that any uncertainty remains with -respect to entire rocks. - -252. This general fact, which I state on much better authority than -that of my own observations, viz. on those of Dr Hutton, is not given -as absolutely without exception. The theory of whinstone which has -been laid down here, leads us indeed to look for some such exceptions. -It is certain, that the basis of whinstone, or the material out of -which it is prepared by the action of subterraneous heat, is clay in -some state or other, and probably in that of argillaceous schistus. -It follows, of consequence, that argillaceous schistus may by heat be -converted into whinstone, or the material out of which is prepared by -the action of subterraneous heat, is clay in some state or other, and -probably in that of argillaceous schistus. It follows, of consequence, -that argillaceous schistus may by heat be converted into whinstone. -When, therefore, melted whinstone has been poured over a rock of such -shistus, it may, by its heat, have converted a part of that rock into -a stone similar to itself; and thus may now seem to be united, by -an insensible gradation, with the stratum on which it is incumbent; -and phenomena of this kind may be expected to have really happened, -though but rarely, as a particular combination of circumstances seems -necessary to produce them. Hence it is evident, that stones may -graduate into one another, without being of the same formation; and -that it is fallacious to conclude, from the insensible transition -of one kind of rock into another, without any other circumstance of -affinity, that they have both the same origin. - -I am disposed, therefore, to make some limitation to what is said -in § 72, where I have expressed an absolute incredulity as to such -transitions as are here referred to. The great skill and experience -of the mineralogist who has described the strata at Scheibenberg, do -not allow us to doubt of his exactness, though some of the appearances -are such as decomposition and wearing might well enough be supposed to -produce. The fairest way is to take Mr Werner's observations just as -they are given us, and to try whether they cannot be explained without -the assistance of his theory. In effect, the wacken which he describes, -rests, it would seem, on an unconsolidated bed of clay; and it may be -supposed, that a part of this bed has been converted into wacken by -the heat of the incumbent mass, and has thus produced the apparent -gradation from the one substance to the other. As the appearances of -the rocks of Scheibenberg seem to be considered by Werner as furnishing -a very strong, and even an unexpected confirmation of his system, I -cannot help thinking, that an explanation of them, on the principles -of Dr Hutton, without any straining or forcing of those principles, -contributes not a little toward extending the empire of the latter over -all the phenomena of geology. - -253. Another fact, which has been much infilled on of late, in proof -of the aqueous formation of basaltic rocks, is that shells are found -in them. Of the reality of this fact, however, or at least of the -instances hitherto produced, great doubts I think may be reasonably -entertained. The specimens of the supposed basaltes, with shells -included in them, that are chiefly relied on, are found at Portrush in -Ireland, a rocky promontory to the westward of the Giant's Causeway, -and separated from it by a considerable body of calcareous strata. -Some of these specimens were brought to Edinburgh about a year ago, -and were supposed, I believe, to contain an irrefragable proof of the -Neptunian origin of the basaltic promontory where they were found. I -went to see these specimens in company with Lord Webb Seymour and Sir -James Hall; and, on examining them carefully, we were all of opinion, -that the stones which contained the shells, or the impressions of the -shells, were no part of the real basaltes. They were all very compact, -and had all more or less of a siliceous appearance, such as that of -chert; they had nothing of a sparry or crystallized structure; their -fracture was conchoidal, and but slightly uneven. In two of them, -one of which bore the impression of a _cornu ammonis_, the schistose -texture might be distinctly perceived. A specimen which accompanied -them, but in which there was no shell, served very exactly to explain -the relation between these stones and the true basaltes. Part of this -specimen was a true basalt, and the rest a sort of hornstone, exactly -the same with that in which the shells were, and not unlike the jasper -that is under the whinstone of Salisbury Crag, and in contact with -it; so that on the whole it was evident, that the rock containing the -shells is the schistus or stratified stone, which serves as the base of -the basaltes, and which has acquired a high degree of induration, by -the vicinity of the great ignited mass of whinstone. - -This solution of the difficulty has since been confirmed by -observations made on the spot by Dr Hope, who discovered two or three -alternations of the basaltic rock, with the beds of the schistus in -which the shells are contained. - -254. This also explains some observations of Spallanzani, made in -the island of Cerigo, on the coast of Greece, the Cythæra of the -ancients.[135] The base of that island is limestone; but it abounds -also in unstratified rocks, which the Italian naturalist supposes to -be of volcanic origin; but which, if I mistake not, we would regard -as whinstone, or perhaps porphyry; and they are said to contain -oyster-shells and pectinites of a large size, perfectly mineralized. -These petrifactions, however, Spallanzani says, are not contained -in the lava that has actually flowed, but in stones which have only -endured a slighter action of fire. Without the commentary afforded by -the Portrush specimens, it would be difficult to make out any thing -very precise from this description. By help of the information derived -from those specimens, we may conclude, that the condition of the -shells in them, and in the rocks of Cerigo, is perfectly alike; and -that, in both cases, the shells are involved in parts of the rock which -are truly stratified, but which have been, in some degree, assimilated -to the basaltes by the heat which they have endured. Spallanzani would -probably have used exactly the same terms which he employs in speaking -of Cerigo, if he had been required to describe the petrified shells at -Portrush. - -[Footnote 135: Journal de physique, tom. xlviii. (1798,) p. 278.] - -255. In the instances just mentioned, the petrified marine objects are -not found in the real whinstone; but if they were found in it, when it -borders on stratified rocks containing such objects, the thing would -not be at all surprising, nor furnish any argument against the igneous -consolidation of the stone. If a torrent of melted matter was poured -in among the strata, by a force which at the same time broke up and -disordered those strata, nothing could be more natural, than that this -matter should contain fragments of them, and of the objects peculiar to -them. - -In one instance, mentioned by Mr Strange, this seems actually to have -taken place. In the Veronese, a country remarkable for a mixture of -limestone strata, containing marine objects, with volcanic or basaltine -hills, he assures us, that he had seen a mass of stone, which had -evidently concreted from fusion, in which the marine fossil bodies, -originally, as he supposes, contained in the strata, were perfectly -distinguishable, though variously disfigured.[136] It may be, that -in this, as in the foregoing examples, it was not real basaltes, or -real lava, which contained the shells, but the conterminal rock; but, -supposing it to be as Mr Strange represents it, there appears to be -no inconsistency between the phenomenon, and the igneous origin of -the rock in which the shells were included. Here, however, it should -be remarked, that the presence of great pressure, to prevent the -conversion of the shells into quicklime, seems absolutely necessary; -and that the phenomenon of these basaltic petrifactions, requires the -application of heat to have been deep under the surface of the earth. - -[Footnote 136: Phil. Trans. 1775, p. 25.] - -256. The phenomena we have been considering, have been selected as the -most unfavourable to the igneous origin of basaltic rocks; and we have -seen, that when duly examined, they are not at all inconsistent with -it. We are now to take a view of some appearances, that seem quite -irreconcilable with the aqueous formation of these rocks. - -Where whinstone rocks are found in masses, bounded by the strata, -and insulated among them, they subject the Neptunian system to great -difficulties. For, supposing it true that this stone may be produced by -the precipitation and crystallization of mineral substances dissolved -in water, yet it seems unaccountable, that this effect has been so -local and limited in extent, as often to be confined to an irregular -figure of a few acres, while, all round, the substances deposited have -had no tendency to crystallization, and have been formed into the -common secondary strata. The rock of Salisbury _Craig_, for instance, -is a mass of whinstone, having a perpendicular face eighty or ninety -feet high toward the west, and extending from north to south with -a circular sweep about 900 yards. The whole of this rock rests on -regular beds of secondary sandstone, not horizontal, but considerably -depressed toward the north-east: the rock is loftiest in the middle, -and decreases in thickness toward each end, terminating at its northern -extremity in a kind of wedge. It is covered at top, toward that -extremity, with regular beds of sandstone, perfectly similar to those -on which it is incumbent; and it is not improbable, that this covering -formerly extended over the whole. - -Now, what cause can have determined the column of water, which rested -on the base at present occupied by this rock, to deposit nothing but -the materials of whinstone, while the water on the south, west, and -north, was depositing the materials of arenaceous and marly strata? -Wherefore, within this small space, was the precipitate every where -_chemical_, to use the language of Werner, while close to it, on either -side, it was entirely _mechanical?_ Why is there, in this case, no -gradation? and why is a mere mathematical line the boundary between -regions where such different laws have prevailed? Whence also, we may -ask, has the basaltic deposit been abruptly terminated toward the west, -so as to produce the steep face which has just been mentioned? The -operation of currents, or of any motion that can take place in a fluid, -will furnish no explanation whatever of these phenomena; yet they are -phenomena far from being peculiar to a single hill; they are among the -most general and characteristic appearances in the natural history of -whinstone mountains; and a geological theory which does not account for -them, is hardly entitled to any consideration. - -257. The basaltic rock, just described, is also covered, at least -partly, with strata perfectly similar to those that lie under it. -Now, it appears altogether unaccountable, that after the water had -done depositing the materials of the whin on the spot in question, -the former order was so quickly resumed, and a deposition of sand, -and of the other materials of the strata, took place just as before. -All this is quite unintelligible; and the principles of the Neptunian -system seem here to stand as much in need of explanation, as any of the -appearances which they are intended to account for. - -258. The unequal thickness, and great irregularity in the surface -of the whinstone mass, here treated of, and of many rocks of the -same kind, is also a great objection to the notion of their aqueous -formation. This seems to have been perceived by Werner, in the instance -of the rocks formerly mentioned; and he endeavours to explain it, by -supposing, that much of these rocks has been destroyed by waste and -decomposition, so that an irregularity of their surface, and want of -correspondence has been given to them, which they did not originally -possess. In the instance of Salisbury _Craig_, however, we have a -proof, that the great irregularity of surface, and the inequality of -thickness, do not always arise from these causes. The thinnest part -of that rock, toward its northern extremity, is still covered by the -strata in their natural place, and has been perfectly defended by them -from every sort of wearing and decay. The cuneiform shape, therefore, -which this rock takes at its extremities, and the great difference of -its thickness at them and in the middle, is a part of its original -constitution, and can be attributed to nothing casual, or subsequent to -its consolidation. - -The same may be said of many other basaltic rocks, where an inequality -of thickness, most unlike to what belongs to aqueous deposits, is known -to exist in beds of whinstone that are still deep under the surface. -Thus the toadstone of Derbyshire, even where it has a thick covering of -strata over it, has been found, by the sinking of perpendicular shafts, -to vary from the thickness of eighteen yards to more than sixty, within -the horizontal distance of less than a furlong. Nothing of this kind -is ever found to take place in those beds of rock which are certainly -known to originate from aqueous deposition, and no character can more -strongly mark an essential difference of formation. - -259. We have had frequent occasion to consider the characters of -those masses of whinstone which are so often found interposed between -stratified rocks. These have been found in general very adverse to the -Neptunian system; and two of them which yet remain to be mentioned, -are even more so than any of the rest. - -Where a bed or tabular mass of whinstone is interposed between strata, -and wherever an opportunity offers of seeing its termination, if the -strata under it are not broken, it may be remarked, that they do not -abut themselves bluff and abrupt against the whin. On the contrary, -if we mark the course of the stratum which covers the whinstone, and -of that which is the base of it, we shall find they converge toward -one another, the interposed mass growing thinner and thinner, like a -wedge. When the latter terminates, the two former come in contact, and -have no stratum interposed between them. Thus the roof and base of the -whinstone rock are contiguous beds, that appear as if they had been -lifted up and bent, and separated by an interposed mass. Had the whole -been an effect of simultaneous deposition, the regular strata must have -been abruptly terminated by the whin, like two courses of different -forts of masonry where they meet with one another. - -260. From this wedge-form of the whinstone masses, and in general from -the irregularity of their surfaces, another conclusion follows, similar -to the preceding, and one which has been already mentioned. Where the -surface of the interposed mass is greatly inclined to the horizon, the -strata which rest on this inclined plane, are nevertheless as exactly -parallel to that plane, and to one another, as if they were really -horizontal. It is certain, therefore, that they were not deposited on -the same inclined plane on which they now rest; for, if so, they would -have been still nearly horizontal, and by no means parallel to the -inclined side of the whinstone. This follows from the nature of aqueous -deposition, as already explained. - -We have a remarkable instance of the phenomenon here referred to, in -the rock of Salisbury _Craig_, of which mention has been so often made, -and in which almost every circumstance is united, that can serve to -elucidate the natural history of basaltic rocks. The north end of that -rock is in the figure of a wedge, with its inclined side considerably -steep, and covered by strata of grit, perfectly regular, and parallel -to the surface on which they lie. The inspection of them will convince -any one, that they were not deposited by the water, on a bottom so -highly inclined as that on which they now rest. They are of a structure -very schistose; their layers very thin; so that any inaccuracy of -their parallelism would be readily observed. The appearances of the -horizontal deposition of these strata, are indeed so clear, and so -impossible to be misunderstood, that the followers of the Huttonian -system would not risk much, if they were to leave the whole theory of -whinstone to the decision of this single fact, and should agree to -abandon that theory altogether, if the Neptunists can shew any physical -or statical principle, on which the deposition now described can -possibly have been made; or will point out the rule, by which nature -has given a structure so nicely stratified to arenaceous beds deposited -on a surface so highly inclined. If no such principle can be pointed -out, though we cannot conclude that the Huttonian Theory is true, we -certainly may conclude that the Neptunian is false. - -261. Proofs of the igneous formation of whinstone, still more direct, -are derived from the induration of the contiguous strata; from their -disturbance when interfered by veins of whinstone; and from the -charring of the coal which happens to be in contact with these veins. -These are considered above at § 66, 67, &c.; and it is particularly -taken notice of at § 66, that pieces of sandstone are sometimes found -as if floating in the whinstone, and, at the same time, greatly altered -in their texture. One of the best and most unequivocal instances of -this sort which I have seen, is to be found on the south side of -_Arthur's Seat_, near Edinburgh. The rock which composes the upper -part of the hill, on that side, is a whinstone breccia, such as we have -many examples of, and, I believe, very much resembling what is called -a _lava brecciata_ by the volcanic geologists. The stony fragments -included in this compound mass, are for the greater part rounded; -and some of them are of whinstone, others of porphyry, strongly -characterized by rectangular maculæ of feldspar, and many seem to be -of sandstone, but so considerably altered, as to leave it at least -disputable whether they really are so or not. In one part, however, -where the face of the rock is nearly perpendicular, a narrow ridge is -seen standing out from the rest, and of a different colour, being more -entirely covered with moss than the rock round about it, and, as may -be presumed from that circumstance, less liable to decomposition. On -examination I found, that this ridge does not consist of whinstone, but -of a very hard and highly consolidated sandstone. It appears to be the -edge of a stratum, of the thickness of about nine or ten inches, and of -the height of fifteen or sixteen feet. It is not perfectly straight, -but slightly waved, its general direction being nearly vertical; and -it is on both sides firmly embraced by the whinstone. When broken, it -appears that this sandstone resembles in colour, and in every thing -but its greater consolidation, and more vitreous structure, the common -grit found at the bottom of the hill, and over all the adjacent plain. - -262. If all these circumstances are put together, there appears but -one conclusion that can be drawn from them. We have here the manifest -marks of some power which could lift up this fragment of rock from its -native place, distant at least several hundred yards from its present -situation, place it upright on its edge, encompass it with a solid -rock, of a nature quite heterogeneous to itself, and bestow on it, at -the same time, a great addition of solidity and induration. If the mass -in which this stone is now imbedded, be supposed to have been once in -fusion, and forcibly thrown up from below, invading the strata, and -carrying the fragments along with it, the whole phenomena now described -admit of an explanation, and all the circumstances accord perfectly -with one another; but, without this supposition, they are so many -separate prodigies, which have no connection with one another, nor with -any thing that is known. It is indeed impossible, that the effects of -motion and heat can be more clearly expressed than they are here, or -the subject in which these powers resided more distinctly pointed out. - -263. The preceding facts being susceptible but of one interpretation, -are on that account extremely valuable. The phenomena of Salisbury -_Craig_, near the same place, are almost equally free from ambiguity. -The basaltic rock which forms that precipice, rests on arenaceous or -marly strata; and these, in their immediate contact with the former, -afford an instance of what is mentioned § 67, namely, the conversion -of the strata in such situations into a kind of petrosilex, or even -jasper. The line which separates the one rock from the other, is, -at the same time, so well defined, as, in the eyes even of the most -determined Neptunist, to exclude all idea of insensible gradation. - -264. The same rock affords some remarkable instances of the disturbance -of the strata contiguous to the whinstone. The beds of the former are -bent upwards in several places; and, at one in particular, form an -arch, with its convexity downward, so as to make it evident, that the -force which produced this bending was directed from below upwards. - -265. It is, however, where whinstone takes the form of veins, -intersecting the strata, that the induration of the latter is most -conspicuous. The coast of Ayrshire, and the opposite coast of Arran, -exhibit these veins in astonishing variety and abundance. The strata -are, in many instances, so _reticulated_ by the veins, and intersected -at such small distances, that it seems necessary to suppose, that the -fissures in them were hardly sooner made than filled up. This at least -is true, if the veins are to be accounted all of the same formation; -and, in the greatest number of instances by far, there is no mark of -the one being posterior to the other. - -266. The induration of the sides of these veins, in some cases, has -been such, that the sides have become more durable than the vein -itself; so that the whinstone has been worn away by the washing of the -waves, and has left the sides standing up, with an empty space, like -a _ditch_, between them. One of these I remarked on the south side of -Brodick Bay, in Arran, which, where it met the face of an abrupt cliff -was not less than forty or fifty feet in depth. - -267. I shall pass over whatever argument might be drawn in favour -of our system, from the slender ramifications of the veins, and -the varieties of their sizes, from a few inches to many fathoms in -diameter, and also from the connection which they often appear to have -with the great tabular masses of basaltes; and shall only add a few -remarks on the charring of coal in the vicinity of veins or masses -of whinstone. The connection between the charring of coal and the -presence of whinstone, was first observed by Dr Hutton; and, as far as -opportunities of verifying the observation have yet occurred, appears -to be a fact no less general than it is curious and interesting. In the -coal mines of Scotland, it certainly holds remarkably, particularly in -those about Saltcoats in Ayrshire, where a whinstone dike is known to -stretch across the whole of the coal country, and to be every where -accompanied with blind or uninflammable coal. At Newcastle, dikes of -the same kind are met with, and one, in particular, in what is called -the _Walker_ Colliery, has proved the action of subterraneous fire, to -the satisfaction of mineralogists nowise prejudiced in favour of the -Huttonian system. - -The coal found under basaltes, in the Island of Sky, has been already -mentioned, § 140. To what was said concerning the fibrous structure of -the parts of that fossil in immediate contact with the whin, it may be -added, that it is also charred in those parts, so as to have hardly -any flame when it is burnt, though further down it is of the nature of -ordinary coal. Indeed, if there be any truth in Mr Kirwan's general -remark, that it is common to find wood coal under basaltes, it must -be understood to arise from this, that the coal in contact with the -basaltes is frequently charred, and its fibrous structure, by that -means, rendered more visible. - -268. It has been objected to the supposition of coal having its -bituminous part driven off by the heat of the whinstone, that this -ought not, on Dr Hutton's principles, to happen in the mineral -regions. But it may be replied, as has been done above, that the local -application of heat might certainly produce this effect, and might -drive off the volatile ports from a hotter to a colder part of the -same stratum. The bitumen has not been so volatilized and expanded as -entirely to escape from the mineral regions; but it has been expelled -from some parts of a mass, only to be condensed and concentrated in -others. This supposition coincides exactly with the appearances. - -269. The native or fossil coke which accompanies whinstone, has been -distinguished into two varieties. The first is the most common, in -which, though the coal is perfectly charred, it is solid, and breaks -with a smooth and shining surface. The second is also perfect charcoal, -but is very porous and spongy. This substance is much rarer than the -other. Dr Hutton mentions an instance of it at the mouth of the river -Ayr, where there is a whinstone dike.[137] I had the satisfaction of -visiting it along with him. It was in the bed of the river, below the -high water mark; the specimens had the exact appearance of a _cinder_. - -[Footnote 137: Theory of the Earth, vol. i. p. 611.] - -In the banks of the same river, some miles higher up, he found a piece -of coal, belonging to a regular stratum, involved in whinstone, and -extremely incombustible. It consumed very slowly in the fire, and -deflagrated with nitre like plumbago. This be considered as the same -fossil which has been described under the name of _plombagine_. Near -it, and connected with the same vein of whinstone, was a real and -undoubted plumbago. - -From these circumstances he also concluded, that plumbago is the -extreme of a gradation, of which fossil-coal is the beginning, and is -nothing else than this last reduced to perfect charcoal This agrees -with the chemical analysis, which shows plumbago to be composed of -carbon, combined with iron. - -In confirmation of this theory, he mentions a specimen, in his -possession, of steatical whinstone, from Cumberland, containing nodules -of a very perfect and beautiful plumbago; and he also takes notice of a -mine of this last, in Ayrshire, which, on the authority of Dr Kennedy, -who has examined it with great care, I can state as being contained, -or enveloped in whinstone; and I hope the public will soon be favoured -with a particular description of this very interesting spot, by the -same ingenious and accurate observer. - -270. Thus the mineralogical and chemical discoveries agree in -representing coal, blind coal, plombagine, plumbago, as all -modifications of the same substance, and as exhibiting the same -principle, carbon, in a state of greater or less combination. As the -last and highest term of this series should be placed the _diamond_; -but we are yet unacquainted with the matrix of this curious fossil, -and its geological relation to other minerals. When known, they will -probably give to this substance the same place in the geological, as in -the chemical arrangement: in the mean time, it is hardly necessary to -remark, how well all the preceding facts agree with the hypothesis of -the igneous formation of whinstone, and how anomalous and unconnected -they appear, according to every other theory. - -271. Notwithstanding all this accumulated and unanswerable evidence -for the igneous formation of basaltes, a great objection would still -remain to our theory, were it not for the very accurate and conclusive -experiments concerning the fusion of this fossil, referred to above, § -75. A strong prejudice against the production of any thing like a real -stone by means of fusion, had arisen, even among those mineralogists, -who were every day witnesses of the stony appearance assumed by -volcanic lava. They still maintained, on the authority of their own -imperfect experiments, that nothing but glass can ever be obtained -by the melting of earths or of stones, in whatever manner they are -combined. - -An ingenious naturalist, after describing a block of basaltes, in which -he discovered such appearances, as inclined him to admit its igneous -consolidation, rejects that hypothesis, merely from the imaginary -inability of fire to give to any substance a stony character: "Quelque -mélange,"says he, "de terres que l'on suppose, quelque soit le degré -de feu que l'on imagine, quelque soit le tems que l'on emploie, il est -très certain que l'on n'obtiendra pas, par le seul fluide igné, ni -basalte, ni rien qui lui ressemble."[138] - -[Footnote 138: Journal de Phys. tom. xlix. (1799,) p. 36.] - -Sir James Hall's experiments have completely demonstrated the contrary -of what is here asserted: they have added much to the evidence of the -Huttonian system; and, independently of all theory, have narrowed the -circle of prejudice and error. - - - - - NOTE XV. § 83. - - _On Granite._ - - - 1. _Granite Veins._ - -272. It is said above, § 77, that granite is found in unstratified -masses, and in veins. In the former of these conditions, it constitutes -entire mountains, and forms the central ridge of many of the greatest -chains that traverse the surface of the earth. It is the granite of -this kind that has been most generally described by travellers and -mineralogists. The veins have not been so much attended to, though -they are of peculiar importance for ascertaining the relation between -granite and other fossils. - -273. Though Dr Hutton was the first geologist who explained the nature -of granite veins, and who observed with attention the phenomena -which accompany them, he is not the first who has mentioned them. M. -Besson found veins of this kind in the Limoges, in an argillaceous -schistus, and unconnected, as far as appeared, with any large mass of -granite.[139] - -[Footnote 139: Journal de Phys. tom. xxix. p. 89.] - -Saussure met with granite veins in the Valorsine, but did not see them -distinctly. He ascribed them to infiltration.[140] The date of this -observation is in 1776: He afterwards discovered similar appearances at -Lyons.[141] - -[Footnote 140: Voyage au Alpes, tom. i. § 598, 599.] - -[Footnote 141: _Ibid._ § 601.] - -Werner also, in enumerating the substances of which veins are formed, -reckons granite as one of them. - -274. Veins of granite may be considered as of two kinds, according as -they are connected, or not connected apparently with any large mass of -granite, it is probable, that these two kinds of veins only differ in -appearance, and that both are connected with masses of the same rock, -though that connection is visible in some instances, and invisible in -others. The distinction, however, whatever it be with respect to the -thing observed, is real with respect to the observer; and, as it is -right, in a description of facts, to avoid every thing hypothetical, I -shall speak of these veins separately. - -275. Veins of granite, having no communication, so far as can be -discovered, with any mass of the same rock, are found in the Western -Islands of Scotland, peculiarly in that of Coll, where they traverse -the beds of gneiss and hornblende schistus, which compose the main -body of the island. They are sometimes several fathoms in thickness, -obliquely intersecting the planes of the strata just mentioned, which -are nearly vertical. In these veins the feldspar is predominant; it is -very highly crystallized, and of a beautiful flesh colour. Many smaller -veins are also to be met with in the same place; but no large mass of -granite is found, either in this or the adjacent island of Tiree. - -276. The Portsoy granite, of which mention has been already made, § -80, also constitutes a vein or dike, traversing a highly indurated -micaceous schistus, about a mile to the eastward of the little town -of Portsoy, and not visibly connected with any large mass of the same -kind. More dikes than one of this granite have been observed near the -same spot. - -A similar granite is likewise found inland, in the neighbourhood of -Huntly, about eighteen miles south of Portsoy; but whether in the shape -of a vein or a mass, I have not been able to learn. - -277. Veins of granite are also frequent in Cornwall, where they are -known by the name of _lodes_, the same name which is applied in that -country to metallic veins. The granite veins frequently intersect -the metallic, and are remarkable for producing shifts in them, or -for throwing them out of their natural direction. The mineral veins, -particularly those that yield copper and tin, run nearly from east to -west, having the same direction with the beds of the rock itself, which -is a very hard schistus. The granite lodes, as also those of porphyry, -called _elvan_ in Cornwall, are at right angles nearly to the former; -and it is remarked, that they generally heave the mineral veins, but -that the mineral veins seldom or never heave the cross-veins. In this -country, therefore, the veins of granite and porphyry are posterior in -formation to the metallic veins. These veins of granite may perhaps be -connected with the great granitic mass that runs longitudinally through -Cornwall, from Dartmoor to the Land's End. This much is certain, that -their directions in general are such, that, if produced, they would -intersect that mass, nearly at right angles. - -278. The granite veins in Glentilt, where Dr Hutton made his first -observations on this subject, are not, I believe, visibly connected -with any large mass of the same rock.[142] The bed of the river Tilt, -in the distance of little more than a mile, is intersected by no -less than six very powerful veins of granite, all of them accompanied -with such marks of disorder and confusion in the strata, as indicate -very strongly the violence with which the granite was here introduced -into its place. These veins very probably belong to the great mass -of granite which is known to form the central ridge of the Grampians -further to the north; but they are several miles distant from it, and -the connection is perhaps invisible in the present state of the earth's -surface. - -[Footnote 142: Trans. Royal Society Edin. Vol iii. p. 77, &c.] - -279. The second kind of granite vein, is one which proceeds visibly -from a mass of that rock, and penetrates into the contiguous strata. -The importance of this class of veins, for ascertaining the relation -between granite and other mineral bodies, has been pointed out, § -82; and by means of them it has been shown, that the granite, though -inferior in position, is of more recent formation than the schistus -incumbent on it; and that the latter, instead of having been quietly -deposited on the former, has been, long after its deposition and -consolidation, heaved up from its horizontal position, by the liquid -body of granite forcibly impelled against it from below. - -It has been alleged, in order to take off the force of the argument -derived from granite veins, that these veins are formed by -infiltration, though, to give any probability to this supposition, -it would be necessary to show, that water is able to dissolve the -ingredients of granite; and even if this could be done, the direction -which the veins have, in many instances, rising up from the granite, -is a proof, as remarked § 82, that they cannot be the effect of -infiltration. - -Another objection has been thrown out, namely, that the veins here -referred to are not of true granite, according to the definition -which mineralogists have given of that substance. The force of a -fact, however, is not to be lessened by a change of names, or the -use of arbitrary definitions. The general fact is, that the granitic -mass, and the vein proceeding from it, constitute one continuous, -and uninterrupted body, without any line of separation between them. -The geological argument turns on this circumstance alone; and it is -no matter whether the rock be a syenite, a granitelle, or a real -granite. The phenomenon speaks the same language, and leads to the same -conclusion, whatever be the technical terms the mineralogist employs in -describing it. - -280. It must, however, be admitted, that a difference of character is -often to be observed between the granite mass and the veins proceeding -from it; sometimes the substances in the latter are more highly -crystallized than in the former; sometimes, but more rarely, they are -less crystallized, and, in some instances, an ingredient that enters -into the mass seems entirely wanting in the vein. These varieties, -for what we yet know, are not subject to any general rule; but they -have been held out as a proof, that the masses and the veins are not -of the same formation. It may be answered, that a perfect similarity -between substances that, on every hypothesis, must have crystallized -in very different circumstances, is not always to be looked for; but -the most direct answer is, that this perfect similarity does sometimes -occur, insomuch that, in certain instances, no difference whatsoever -can be discovered between the mass and the vein, but they consist of -the same ingredients, and have the same degree of crystallization. Some -instances of this are just about to be remarked. - -281. A strong objection to the supposed origin of granitic veins -from infiltration, and indeed to their formation in any way but by -igneous fusion, arises from the number of fragments of schistus, often -contained, and completely insulated in those veins. How these fragments -were introduced into the fissures of the schistus, and sustained till -they were surrounded by the matter deposited by water, is very hard -to be conceived; but if they were carried in by the melted granite, -nothing is more easily understood. - -The following are some of the places where the phenomena of granite -veins may be distinctly seen. - -282. The island of Arran, remarkable for collecting into a very small -compass a great number of the most interesting facts of geology, -exhibits many instances of the penetration of schistus by veins of -granite. A group of granite mountains occupies the northern extremity -of the island, the highest of which, Goatfield, rises nearly to the -height of 3000 feet, and on the south side is covered with schistus -to the height of 1100. From thence, the line of junction, or that -at which the granite emerges from under the schistus, winds, so far -as I was able to observe, round the whole group of mountains, with -many wavings and irregularities, rising sometimes to a greater, and -descending sometimes to a much lower level, than that just mentioned. -Along this line, particularly on the south, wherever the rock is laid -bare, and cut into by the torrents, innumerable veins of granite are to -be seen entering into the schistus, growing narrower as they advance -into it; and being directed, in very many cases, from below upwards, -they are precisely of the kind which the infiltration of water could -not produce, even were that fluid capable of dissolving the substances -which the vein consists of. From this south face of the mountain, and -from the bed of a torrent that intersects it very deeply, Dr Hutton -brought a block of schistus, of several hundred weight, curiously -penetrated by granite veins, including in them many insulated fragments -of the schistus. - -From this point, the common section of the granite and schistus -descends towards the west side of the mountain, and is visible at the -bottom of a deep glen, (Glen-Rosa,) which detaches Goatfield from the -hills farther to the west. The junction is laid bare at several places -in the bed of the river which runs in the bottom of this glen; and in -all of them exhibits, in a greater or less degree, the appearances of -disturbance and violence which have accompanied the injection of the -granite veins. Many circumstances render this spot interesting to a -geologist, and, among others, an intersection of the granite, a little -above its junction with the schistus, by a dike or vein of very compact -whinstone. - -The same line of junction is found on the opposite, or north-east, side -of the mountain, where it is intersected by another little river, the -Sannax, which on this side determines the base of the mountain. This -junction is no less remarkable than the other two. - -The island of Arran contains, I have no doubt, many other spots where -these phenomena are to be seen; but I have had no opportunity of -observing them, nor do I find that Dr Hutton met with any others in his -visit to this island. - -283. Another series of granite veins is found in Galloway, which was -first discovered by Dr Hutton and his friend Mr Clerk, and afterwards -more fully explored by Sir James Hall and Mr Douglas, the present Earl -of Selkirk. The two last traced the line of separation between a mass -of granite and the schistus incumbent upon it, all round a tract of -country, about eleven miles by seven, extending from the banks of Loch -Ken westward; and in all this tract they found, "that wherever the -junction of the granite with the schistus was visible, veins of the -former, from fifty yards, to the tenth of an inch in width, were to be -seen running into the latter, and pervading it in all directions, so -as to put it beyond all doubt, that the granite of these veins, and -consequently of the great body itself, which was observed to form with -the veins one uninterrupted mass, must have flowed in a soft or liquid -state into its present position."[143] I have only farther to add, that -some of these veins are remarkable for containing granite, not sensibly -different, in any respect, from the mass from which they proceed. - -[Footnote 143: Trans. Royal Society Edin. vol. iii. p. 8.] - -284. In Invernessshire, between Bernera and Fort Augustus, the same -phenomena occur on the north side of Loch Chloney, where some granite -mountains rise from under the schistus. In travelling near this place, -Lord Webb Seymour and myself were advertised of our approach to a -junction of granite and schistus, by finding among the loose stones on -the road many pieces of schistus, intersected with veins of feldspar -and granite. We walked along this junction for more than a mile; and -toward the east end, where the road leaves it, we saw, in the bed of -a stream that runs into Loch Chloney, many beautiful specimens of -granitic veins pervading the schistus, and branching out into very -minute ramifications. - -285. The last instance I have to mention from my own observation, is -at St Michael's Mount in Cornwall. That mount is entirely of granite, -thrust up from under a very hard micaceous schistus, which surrounds -it on all sides. At the base of it, on the west side, a great number -of veins run off from the granite, and spread themselves like so many -roots fixed in the schistus: they are seen at low water. In the smaller -veins, the granite is of very minute, though distinct parts; in the -larger, it is more highly crystallized, and is undistinguishable from -the mass of the hill. - -Besides the above, Cornwall probably affords many other instances of -the same kind, which I have not had an opportunity to examine. Such -instances may in particular be looked for at the Land's End, where a -promontory, consisting of a central part of granite, and covered by -a micaceous schistus on both sides of it, is cut transversely by the -sea coast, and the contact of the granite and schistus of course twice -exposed to view. - -286. Scotland also affords other examples of granite veins, and some -of them have been actually described. Mr Jameson has taken notice of -some which he saw in the bottom of the river Spey, at Glen Drummond, in -Badenach, and has represented them in an engraving.[144] They traverse -the strata in various directions, and inclose pieces of the micaceous -schistus; and, from the great number of loose blocks which he found, -exhibiting portions of such veins, it is probable, that they are very -numerous in this quarter. The same mineralogist mentions some instances -of similar veins in the Shetland Isles.[145] - -[Footnote 144: Mineralogy of the Scottish Isles, vol. ii. p. 3.] - -[Footnote 145: _Ibid._ p. 216.] - -In Ross-shire, Sir George Mackenzie has observed a great variety of -granite veins, some of them of large size. One of them, in particular, -not far from Coul, when first discovered, was supposed to be a -single mass, rising from under the schistus; but, on a more careful -examination, has been found to be a part of a great system of veins -which intersects the micaceous schistus of this tract in various -directions. - -287. The granite veins are not the only proof that this stone is more -recent than some other productions of the mineral kingdom. Specimens -of granite are often found, containing round nodules of other stones, -as, for example, of gneiss or micaceous schistus. Such is the specimen -of granite containing gneiss, which Werner himself is said to be in -possession of, and to consider as a proof, that the schistus is of -greater antiquity than the granite. Such also seemed to me some pieces -of granite, which I met with in Cornwall, near the Land's End; and -others which I saw in Ayrshire, in loose blocks, on the sea coast -between Ayr and Girvan. It is impossible to deny that the containing -stone is more modern than the contained. The Neptunists indeed admit -this to be true, but allege, that all granite is not of the same -formation; and that, though some granite is recent, the greater part -boasts of the highest antiquity which belongs to any thing in the -fossil kingdom. This distinction, however, is purely hypothetical; it -is a fiction contrived on purpose to reconcile the fact here mentioned -with the general system of aqueous deposition, and has no support from -any other phenomenon. - - - 2. _Granite of Portsoy._ - -288. The granite of Portsoy is one of the most singular varieties of -this stone, and is remarkable for this circumstance, that the feldspar -is the substance which has assumed the figure of its proper crystal, -and has given its form to the quartz, so that the latter is impressed -both with the acute and obtuse angles belonging to the rhombic figure -of the former. The angular pieces of quartz thus moulded on the -feltspar, and ranged by means of it in rows, give to this stone the -appearance of rude alphabetical writing. - -Now, Dr Hutton argued, that substances precipitated from a solution, -and crystallizing at liberty, cannot be supposed to impress one another -in the manner here exemplified; and that they could do so only when -the whole mass acquired solidity at the same time, or at the same time -nearly.[146] Such simultaneous consolidation can be produced in no way -that we know of, but by the cooling of a mass that has been in fusion. - -[Footnote 146: Theory of the Earth, vol. i. P. 104.] - -289. A granite, brought from Daouria by M. PATRIN, and described by him -in the Journal de Physique for 1791, p. 295, under the name of _pierre -graphique_, seemed to Dr Hutton to have so great a resemblance to the -granite of Portsoy, that he ventured to consider them both as the same -stone, and as both containing quartz moulded on feltspar.[147] It -should seem, however, from further explanations, which M. Patrin has -since given, but Dr Hutton was mistaken in his conjecture, and that, in -the _pierre graphique_ of the former mineralogist, the quartz gives its -form to the feltspar, preserving in its crystals their natural angle of -120 degrees[148] It is impossible, I think, to doubt of the accuracy -of this statement; and the graphical stone of Portsoy must therefore -be admitted to differ materially from that of Daouria. They are not, -however, without some considerable affinity, besides that of their -outward appearance; for, though the quartz in the former is generally -moulded on the feltspar, the feldspar is also occasionally impressed by -the quartz, and sometimes even included in it. They may be considered -as varieties of the same species of granite; and the _pierre graphique_ -of Corsica is probably a third variety, different from them both. - -[Footnote 147: Trans. Royal Society Edin. vol. iii. p. 83.] - -[Footnote 148: Journal Britainnique, (of Geneva,) 1798, vol. viii. -Sciences et Arts, p. 78.] - -290. It would seem, however, that all these stones lead exactly to -the same conclusion. M. Patrin describes his specimen as containing -quartz crystals, that are for the most part only _cases_, having their -interior filled with feltspar "Le feltspath en masse contient des -crysteaux quartzeux, qui n'ont le plus souvent que la carcasse, et dont -l'interieur est rempli de feltspath; souvent il manque à ces carcasses -quelques unes de leurs faces, et souvent la section de cette pierre -dans un sens transversal aux crysteaux, presente une suite de figures -qui sont des portions d'hexagones, et qui ne resemblent pas mal à des -caractères Hebraiques."[149] - -[Footnote 149: Journal Britannique, _Ibid._] - -These imperfect hexagonal cases of quartz, filled with feldspar, -certainly indicate the crystallization of substances, which all -assumed their solidity at the same time, and, in doing so, constrained -the figures of one another. To use the words of Dr Hutton, "whether -crystallizing quartz inclose a body of feltspar, or concreting feltspar -determine the shape of fluid quartz, particularly if we have, as is -here the case, two solid bodies including and included, it amounts to -a demonstration, that those bodies have concreted from a fluid state -of fusion, have not crystallized, in the manner of salts, from a -solution."[150] - -[Footnote 150: Trans. Royal Society Edin. _ubi supra_, p. 84.] - -291. The quartz in granite so generally receives the impressions of -all the other substances, particularly of the feldspar and schorl, -and appears to be so passive a body, that it has been doubted by some -mineralogists, whether in this stone it ever assumes its own figure, -except where cavities afford room for its crystallization. But it -is certain that, beside the Daourian granite just mentioned, there -are others, in which the quartz is completely crystallized. Of this -sort are some specimens, found in a granite vein on the west side of -the hill of St Agnes, in Cornwall. The vein traverses the primitive -schistus, of which that hill consists, from south to north nearly: -the stone is much decomposed, and the feldspar in general is almost -reduced to the state of clay. In this decomposed mass, quartz crystals -are found, having the shape of double hexagonal pyramids, perfectly -regular and complete. The side of the hexagon, which is the base of the -two opposite pyramids, varies from half a tenth to a tenth of an inch -in length, and is the same with the altitude of each of the pyramids. -In some few specimens, the two pyramids do not rest on the same base, -but are separated by a very short, though regular, hexagonal prism. -The surfaces of these crystals are rough, and somewhat opaque, with -slender spiculæ of schorl frequently traversing them. This roughness -is occasioned by slight furrows on the surface of the crystal, very -regularly disposed, and parallel to one another, being without doubt -impressions from the thin plates of the feldspar, which surrounded -the crystal, and slightly indented it. They very much resemble some -impressions, remarked by Dr Hutton in the granite of Portsoy, and -ascribed by him also to a similar cause. He has represented these in -his Theory of the Earth, vol. i. plate ii. fig. 4. The action and -reaction of two crystallizing bodies, hardly admits of a stronger and -more unequivocal expression, than in these two instances. - -Where the granite was little decomposed, the quartz was not easily -disengaged from the mass it was imbedded in, and often broke in pieces -before it could be extricated. The crystallization of the quartz, -therefore, would not have been discovered, but for the decomposition of -the feltspar; and it is probable, that similar crystallizations exist -in many granites where they are not perceived. - -292. Some mineralogists are inclined to think, that the regular -crystallization of quartz is to be found only in what they call -secondary granites, or in those that are of a formation subsequent -to the great masses which constitute the granite mountains. It is -indeed true, that in the instances given here, both from Cornwall and -Daouria, the granites containing quartz crystals are from veins that -intersect the primary schistus, and are therefore, on every hypothesis, -of a formation subsequent to that schistus. But it does not follow -from thence, that they are less ancient than the great masses of -unstratified granite; with these last they are most probably coëval, -nor can there be any reason for thinking the crystallization of quartz -a mark of more recent formation than that of feltspar. - - - 3. _Stratification of Granite._ - -293. What are the various modes in which granite exists, is a question -not absolutely decided among mineralogists. 1. That it exists as a -schistose stone of a fissile texture, in gneiss and _veined granite_, -is on all hands admitted, though in this state the name of granite -is generally withheld from it. 2. That it exists often without any -indication of a fissile texture, and altogether unstratified, is -likewise acknowledged. 3. That it is found in veins, intersecting -the strata, has been shown above. The only mode of its existence -subject to dispute, is that in which it is said to be stratified in -its outward configuration, but not schistose in its texture. On this -point mineralogists do not perfectly agree: Dr Hutton did not think -that this was a state in which granite ever appears. When not schistose -in its structure, he supposed it to be unstratified altogether; and -he considered it as a body which, like whinstone, was originally in -a state of igneous fusion, and, in that condition, injected among -the strata. The school of Werner, on the other hand, maintain, that -granite, if not always, is generally stratified, and disposed in beds, -sometimes horizontal, though more frequently vertical, or highly -inclined. - -In forming an opinion where there are great authorities on opposite -sides, a man must trust chiefly to his own observations, and ought -to esteem himself fortunate if these lead to any certain conclusion. -Mine incline me to differ from Dr Hutton, on the one hand, and from -the Neptunists, on the other, as they convince me, that granite does -form strata where it has no character of gneiss; and, at the same -time, induce me to suspect, that the stratification ascribed by the -Neptunists to the granite mountains, is, in many instances, either an -illusion, or at least something very different from what, in other -stones, is accounted stratification. - -294. The first example I ever saw of granite that was stratified, -and yet had no character of gneiss, was at Chorley Forest, in -Leicestershire. The greater part of that forest has for its base a -hornstone schistus, primary and vertical; and, on its eastern border, -particularly near Mount Sorrel, are beds of granite, holding the same -direction with those of the schistus. The stone is a real granite; -it has nothing in its internal structure of a schistose or fissile -appearance; and its beds, which it is material to remark, are no -thicker than those of the hornstone strata in the neighbourhood. This -granite is remarkable, too, for being close to the secondary sandstone -strata; I did not see their contact, but traced them within a small -distance of one another; so that I think it is not likely that any body -of rock intervenes. At the same time that I state my belief of this -rock of granite being in regular strata, I must acknowledge, that a -very intelligent mineralogist, who viewed these rocks at the same time, -and whose eye was well practised in geological observation, remained in -doubt concerning them. - -295. Another instance of a real granite, disposed in regular beds, but -without any character of gneiss, is one which I saw in Berwickshire, -in Lammermuir, near the village of Priestlaw. The little river of -Fassnet cuts the beds across, and renders it easy to observe their -structure. The beds are not very thick; they run from about S.S.W. to -N.N.E. like the schistus on either side of them. I was in company with -Sir James Hall when I saw these rocks; we examined them with a good -deal of attention, and traced them for more than a mile in the bed of -the river; and, if I mistake not, our opinions concerning them were -precisely the same. - -296. What exists in two instances may exist in many, and, after these -observations, I should be guilty of great inconsistency, in refusing -to assent to the accounts of Pallas, De Luc, Saussure, and many other -mineralogists, who so often represent granite as formed into strata. -In some cases, however, it is certain, that the stratification they -describe is extremely unlike that in the two instances just mentioned, -and indeed very unlike any thing that is elsewhere known by the name -of stratification. For example, the stratification must be very -ambiguous, and very obscurely marked, that was not discovered till -after a series of observations, continued for more than twenty years, -by a very skilful and distinguishing mineralogist. Yet such undoubtedly -is the stratification of Mont Blanc, and of the granite mountains in -its neighbourhood, as it escaped the eyes of Saussure, in the repeated -visits which he made to them, during a period of no less extent than -has just been mentioned. It was not till near the conclusion of those -labours, to which the geologists of every age will consider themselves -as highly indebted, that, having reached the summit of Mont Blanc, he -perceived, or thought that he perceived, the stratification of the -granite mountains. The _Aiguilles_ or Needles which border the valley -of Chamouni, and even Mont Blanc itself, appeared to be formed of vast -tabular masses of granite, in position nearly vertical, and so exactly -parallel, that he did not hesitate to call them by the name of strata. -Till this moment, these same mountains, viewed from a lower point, -had been regarded by him as composed of great plates of rock, nearly -vertical indeed, but applied, as it were, round an axis, and resembling -the leaves of an artichoke;[151] and the fissures by which they are -separated from one another, had been considered as effects of waste and -degradation. "But now," (says he, speaking of the view from the top of -Mont Blanc,) "I was fully convinced, that these mountains are entirely -composed of vast plates of granite, perpendicular to the horizon, and -directed from N.E. to S.W. Three of these plates, separated from each -other, formed the top of the _Aiguille du Midi_, and other similar -plates, decreasing gradually in height, compose its declivity to the -south."[152] - -[Footnote 151: Voyages aux Alpes, tom. ii. § 910, &c.] - -[Footnote 152: Voyages aux Alpes, tom. iv. § 1996.] - -297. Saussure was so strongly impressed with the appearances of what -he accounted regular stratification, such as water only can produce, -and such as must have been in the beginning horizontal, that, placed -as he now was, on one of the highest points of the earth's surface, he -formed the bold conception, that the summit on which he was standing -had been once buried under the surface, to the depth at least of half -the diameter of the mountain, and horizontally distant from its present -place by a line not less than the whole height of the mountain; the -granite beds which compose that mountain, having been raised by some -enormous power from their horizontal position, and turned as on an -axis, till they were brought into the vertical plane. In this notion, -which suits so well with the nature of mountains really composed of -vertical strata, and which does credit to the extent of Saussure's -views, it is wonderful that he did not see the overthrow of the -geological system be had adopted, which is provided with no means -whatsoever of explaining these great effects. - -Such, then, were the ideas suggested to Saussure, by viewing the -mountains of the Alps from the highest of their summits. His great -experience, his accurate knowledge of the objects before him, and the -power he had acquired of dissipating those illusions, to which, in -viewing mountainous tracts, the eye is peculiarly subject, all conspire -to give great weight to his opinion. Yet, as this opinion is opposed -by that which he himself had so long entertained, before it can be -received with perfect confidence, it will require to be verified by new -observations. It seems certain, that the beds of rock here described, -differ from all ordinary strata, both horizontal and vertical, in the -circumstance of their vast thickness, three of them being so large as -to form the main body of a mountain. Their parallelism cannot easily -be ascertained; and they have at best but a very slight resemblance to -such beds as water is known to produce. - -298. Their parallelism is difficult to be ascertained; for, on account -of the magnitude and inaccessibility of the objects, it is impossible -to place the eye in any situation, where it shall not be much nearer to -one part of the planes whereof the parallelism is to be estimated, than -to another. Indeed, one can perceive a cause which may have rendered -the parallelism of the plates of granite which compose the _aiguilles_, -more accurate in appearance than in reality, when viewed from a point -so elevated as the summit of Mont Blanc. For, even on the supposition -that the comparison of those plates to leaves of artichokes was just, -and that the planes of their separation converged toward one another, -in ascending to the top, when they were viewed from a point more -elevated than that top, this convergency would be diminished, and, by -the force of the perspective, might even be converted into parallelism. -We cannot at present ascertain what effect this cause of deception may -have actually produced. - -299. The observations of Saussure concerning the stratification -of granite, are not, however, in all instances, liable to these -objections; and it seems to be on much less exceptionable grounds -that he pronounces the granite of St Gothard to be stratified. The -gneiss and micaceous schistus which constitute the lower part of that -mountain, are succeeded by a granite without any schistose appearance, -but divided into large plates, exactly parallel to the beds of the -former gneiss. These he regards as real strata. On studying them in -detail, he says, considerable irregularities were to be observed, but -not greater than in the case of limestone or micaceous schistus.[153] -It may be inferred from this, that these plates of granite are not so -thick but that they admit of comparison with beds that are known with -certainty to be of aqueous formation, and I am therefore disposed to -believe, that the granite of St Gothard, in this part at least, is -stratified. The transition from gneiss to granite en masse, is not -uncommon, as Saussure has observed in other instances, and as we are -just about to consider more particularly. - -[Footnote 153: Voyages aux Alpes, tom. iv. § 1830.] - -300. In the mountains of our own country, some difficulties concerning -the stratification of granite have also occurred. In Arran, for -instance, the mountain of Goatfield, which I have mentioned above -as affording an instance of granite sending out many veins into -the schistus, and rivetted, as it were, by means of them to the -superincumbent rock, when I visited it, with, a view of verifying -on the spot the interesting observations which Dr Hutton had there -made, appeared to me to be without any vestige of stratification in -its granitic part, as did also the whole group of mountains to which -it belongs. It was, therefore, not without a good deal of surprise, -that I lately read, in an account of that island, by a very accurate -and ingenious mineralogist, that Goatfield consists of stratified -granite.[154] The impression which the appearance of that mountain -made on my mind, is just the reverse; and though I saw large tabular -masses, sometimes nearly vertical, separated by fissures, they -appeared to be much too irregular, too little extended in length and -height, and vastly too much in thickness, to be reckoned the effects -of stratification. For all this, I would by no means be understood -to set my observations in opposition to those of Mr Jameson. In my -visit to Arran, I did not direct my inquiries much toward this point; -the general appearance of the rocks did not suggest the necessity of -doing so, and I was not perfectly aware how much the stratification of -granite had been insisted on by some mineralogists; so that I applied -myself entirely to study some other of the interesting phenomena which -this little island offers in so great abundance. I therefore carry -my confidence in the appearances which seemed to indicate a want of -stratification in the granite of Arran no further than to remain -sceptical both as to Mr Jameson's conclusions and my own, till an -opportunity shall occur of verifying the one or the other by actual -observation. - -[Footnote 154: Mineralogy of the Scottish Isles, vol. i. p. 35, 36.] - -301. The stratification of granite, though it made no part of Dr -Hutton's system, does by no means embarrass his theory with any new -difficulty. Rocks, of which the parts are highly crystallized, are -already admitted as belonging to the strata, and are exemplified in -marble, gneiss, and veined granite. In the two last, we have not only -stratification, but a schistose, united with a crystallized structure, -and the effects of deposition by water, and of fluidity by fire, are -certainly no where more singularly combined. The stratification of -these substances is therefore more extraordinary than even that of the -most highly crystallized granite. Neither the one nor the other can be -explained but by supposing, that while such a degree of fluidity was -produced by heat, as enabled the body when it cooled to crystallize, -the whole mass was kept in its place by great pressure acting on all -sides, so that the shape was preserved as originally given to it by -the sea. As we cannot, however, suppose, that the intensity of the -heat, or the fusibility of the substance through all the parts of a -stratum, were precisely the same, we may expect to find in the same -stratum, or in the same body of strata, that in some parts the marks -of stratification are completely obliterated while in others they -remain entire. It is thus that _veined granite_, of what I think should -be called granitic schistus, often graduates into granite _in mass_, -that is, granite without any schistose or fissile texture. Saussure -says, that to be veined or not veined, is an affection of granite, -that seems, in many cases, accidental;[155] as, in the midst of rocks -of that substance, most clearly fissile, large portions appear without -any vestige of stratification. Of this phenomenon, which is frequent -in the Alps, instances are also to be met with in the granite rocks -of Scotland, and the adjacent isles; and I know that Dr Hope, in a -mineralogical excursion which he lately made among the Hebrides, -observed many interesting and curious examples of it. Indeed, when -rocks were so much fused as to crystallize, and so compressed, at the -same time, as to remain stratified, they were evidently on the verge of -change; two opposite forces were very nearly balanced, and each carried -as far as it could go without entirely overcoming the other; so that -a small alteration in the conditions may have made a great alteration -in the effects. Hence a sudden transition from a stratified to an -unstratified texture, which is only found in rocks highly crystallized, -and such as have endured the most violent action of the mineralizing -powers. - -[Footnote 155: Voyages aux Alpes, tom. iv. § 2143.] - -302. Now, though the stratification of granite, or the mixture of the -stratified with the unstratified rocks of that genus, is not only -reconcilable with the principles of the Huttonian geology, but might -even have been deduced as a corollary from those principles, before -it was actually observed, it may be considered as inconsistent with -the theory of granitic veins that has just been given. A stratum, -though soft or fluid, could not invade the surrounding strata with -violence, nor send out veins to penetrate into them. It might, if, -strongly compressed by another stratum less fluid than itself, fill up -any fissures or cracks that were in that other, but this would hardly -produce, such large veins, and of such considerable length, as often: -penetrate from the granite into the schistus, nor could it give rise -to any appearance of disturbance. If, therefore, veins were found -proceeding from such stratified granite as that of Chorley Forest or -Lammermuir, I should think, that the explanation of them was still a -_desideratum_ in geology. The Neptunian theory of infiltration would -indeed be as applicable to them as to any other veins; for it is but -little affected by the condition of the phenomena to be explained. -Indeed, it is very difficult to set any limits to the explanations -which this theory affords; and it would certainly puzzle a Neptunist, -to assign any good reason why infiltration has not produced veins of -one schistus running into another, or veins of schistus running into -granite, as well as of granite running into, schistus. He will find it -a hard task to restrain the activity of his theory, and to confine its -explanations to those things that really exist. - -303. As the Huttonian system cannot boast of theories of equal -versatility, it would be not a little embarrassed to account for veins -of great magnitude proceeding from a rock distinctly stratified, and -accompanied with marks of having disturbed the rocks through which they -pass. I am, however, inclined to believe, that this embarrassment will -never occur; and that the granite veins do not proceed from the rocks -that are really stratified, but from such as have never been deposited -by water, and where the appearances of stratification, if there are -any, are altogether illusory. This anticipation, however, requires to -be verified by future observation; and it remains to be seen, whether -granitic veins ever accompany real granitic strata, or are peculiar to -those in which the appearances of regular beds are either ambiguous, -or are entirely wanting. The decision of this question is an object -highly worthy of the attention of geologists. - -304. An argument, directed at once against the igneous origin and -unstratified nature of all granite, is given in a work already -mentioned. "If granite had flowed from below, how does it happen, that, -after it had burst through the strata of micaceous schistus, &c. it did -not overflow the neighbouring country? If this hypothesis were true, -Mont Blanc could never have existed."[156] - -[Footnote 156: Mineralogy of the Scottish Isles, vol. ii. p. 166.] - -A theory is never more unfairly dealt with, than when those parts -are separated which were meant to support one another, and each left -to stand or fall by itself. This, however, is precisely what is done -in the present instance; for Dr Hutton's theory of granite would -not deserve a moment's consideration, if it were so inartificially -constructed, as to suppose that granite was originally fluid, and yet -to point out no means of hindering this fluid from diffusing itself -over the strata, and settling in a horizontal plane. The truth is, that -his theory, at the same time that it conceives this stone to have been -in fusion, supposes it to have been, in that state, injected among the -strata already consolidated; to have heaved them up, and to have been -formed in the concavity so produced, as in a mould. Thus Mont Blanc, -supposing that it is unstratified, is understood to consist of a mass -that was melted by subterraneous heat under the strata, and being -impelled upwards by a force, that may stand in some comparison with -that which projected the planets in their orbits, heaved up the strata -by which it was covered, and in which it remained included on all sides. - -305. The covering of strata, thus raised up, may have been burst -asunder at the summit, where the curvature and elevation were the -greatest; but the melted mass underneath may have already acquired -solidity, or may have been sustained by the beds of schistus incumbent -on its sides. This schistus, forming the exterior crust, was -immediately acted on by the causes of waste and decomposition, which -have long since stripped the granite of a great part of its covering, -and are now exercising their power on the central mass. That even Mont -Blanc itself, as well as other unstratified mountains, was once covered -with schistus, will appear to have in it nothing incongruous, when we -consider the height to which the schistus still rises on its sides, -or in the adjacent mountains; and when we reflect, that, from the -appearances of waste and degradation which these mountains exhibit, it -is certain, that the schistus must have reached much higher than it -does at present. - -It is obvious, therefore, that when the corresponding parts are brought -together, and placed in their natural order, no room is left for the -reproach, that this system is inconsistent with the _existence_ of -granite mountains. I have no pleasure in controversial writing; and, -notwithstanding the advantages which a weak attack always gives to a -defender, I cannot but regret, that Dr Hutton's adversaries have been -so much more eager to refute than to understand his theory. - -[Illustration] - -306. A remark which Dr Hutton has made on the quantity of granite that -appears at the surface, compared with that of other mineral bodies, -has been warmly contested. Having affirmed, that the greater part of -rocks bear marks of being formed from the waste and decomposition of -other rocks, he alleges that granite, (a stone which does not contain -such marks) does not, for as much as appears from actual observation, -make up a tenth, nor perhaps even a hundredth part of the mineral -kingdom.[157] Mr Kirwan contends, that this is a very erroneous -estimate, and that the quantity of granite visible on the surface, far -exceeds what is here supposed.[158] The question is certainly of no -material importance to the establishment of Dr Hutton's theory: it is -evident, too, that an estimation, which varies so much as from a tenth -to a hundredth part, cannot have been meant as any thing precise; yet -it may not be quite superfluous to show, that the truth probably lies -nearer to the least than the greatest of the limits just mentioned. - -[Footnote 157: Theory of the Earth, vol. i. p. 211.] - -[Footnote 158: Geol. Essays, p. 480.] - -307. Though granite forms a part, generally the central part, of all -the great chains of mountains, it usually occupies a much less extent -of surface than the primary schistus. Thus in the Alps, if a line be -drawn from Geneva to Ivrea, it will be about eighty-five geographical -miles in length, and will measure the breadth of this formidable -chain of mountains, at the place of its greatest elevation. Now, from -the observations of Saussure, who crossed the Alps exactly in this -direction, it may be collected, that less than nine miles of this line, -or not above a tenth part of it, in the immediate vicinity of Mont -Blanc, is occupied by granite. - -308. In some sections of the Alps, no granite at all appears. Thus, in -the route from Chambery to Turin, across Mont Cenis, which measures by -the road not less than ninety miles, no granite is found, at least of -that kind which is distinctly in mass, and different from gneiss or -veined granite.[159] - -[Footnote 159: Voyages aux Alpes, tom. iii. § 1190, &c.] - -309. In some other places of the same mountains, the granite is more -abundant. A line from the lake of Thun, along the course of the Aar, -and over the mountains to the upper end of Lago Maggiore, crosses a -very elevated tract, and passes by the sources of the Rhone, the Rhine, -and the Tessino, which last runs into the Po. A good deal of granite is -discovered here, in the mountains of Grimsel and St Gothard; but by far -the greater part of it is the veined granite, the granite in mass being -confined chiefly to the north side of the Grimsel. Both together do not -occupy more than one-third of the line, and therefore the latter less -than one-sixth. - -310. The essay on the mineralogy of the Pyrenees, by the Abbé PALASSO, -contains a mineralogical chart of those mountains. From this chart I -have found, by computation, that the granite does not occupy one-fifth -of the horizontal surface on the north side of the ridge, reckoning -from one end of it to the other. Indeed, many great tracts, even of the -central parts of the Pyrenees, contain no granite whatsoever; and not a -few of the highest mountains consist entirely of calcareous schistus. -A large deduction should be made from the fraction 1/5 on account of -the substances unknown, which, from the construction of the chart, are -often confounded with the granitic tract. - -311. I might add other estimations of the same kind, all confessedly -rude and imperfect, but still conveying, by means of numbers, a better -idea of the limit to which our knowledge approximates, than could be -done simply by words; and, on the whole, it would appear, that if we -state the proportion of granite to schistus to be that of one to four, -we shall certainly do no injustice to the extent of the former. - -It remains to form a rough estimate from maps, and from the accounts -of travellers, of what proportion of the earth's surface consists -of primary, and what of secondary rocks. After supplying the want -of accurate measurement by what appeared to me the most probable -suppositions, I have found, that about 1/18 of the surface of the old -continent may be conceived to be occupied by primitive mountains; of -which, if we take one-fifth, we have 1/90 for the part of the surface -occupied by granite rocks, which differs not greatly from the least of -the two limits assigned by Dr Hutton. - -312. In estimating the granite of Scotland, Dr Hutton has certainly -erred considerably in defect,[160] and Mr Kirwan, who always differs -from him, is here nearest the truth; though he is right purely by -accident, as the information on which he proceeds is vague and -erroneous. - -[Footnote 160: Dr Hutton in this case no doubt made a very loose -estimate. He says, the granite does not perhaps occupy more than a -500dth part of the whole surface. The whole surface of Scotland is not -much more than 23,000 geographical miles, the 500dth part of which is -exactly 46; and this is exceeded by the granite in Kirkcudbrightshire -done, as may be gathered from what is said § 283.] - -The places in Scotland where granite is found, are very well known; but -the extent of some of the most considerable of them is not accurately -ascertained. In the southern parts, except the granite of Galloway, -which is found in two pretty large insulated tracts, there is no -other of any magnitude. The granite of the north extends over a large -district. If we suppose a line to be drawn, from a few miles south -of Aberdeen to a few miles south of Fort William, it will mark out -the central chain of the Grampians in its full extent, passing over -the most elevated ground, and by the heads of the largest rivers, -in Scotland. Along this line there are many granite mountains, and -large tracts in which granite is the prevailing rock. There are, -however, large spaces also in which no granite appears, though, if we -were permitted to speak theoretically, and if the question did not -entirely relate to a matter of observation, we might suppose, that, -in no part of this central ridge is the granite far from the surface, -notwithstanding that in some places it may be covered by the schistus. - -313. A great part of the Grampian mountains is on the south side of the -line just mentioned, but hardly any granite is found in this division -of them, except such veins as those of Glentilt. On the north side of -the line, the granite extends in various directions; and, if from Fort -William a line is drawn to Inverness, the quadrilateral figure, bounded -on two sides by these lines, and on the other two by the sea, will be -found to contain much granite, and many districts consisting entirely -of that stone. This is in fact the great granite country of Scotland: -it is a large tract, containing about 3170 square geographical -miles, or about a seventh part of the whole: but the proportion of -it occupied by granite cannot at present be ascertained with any -exactness, nor will, till some mineralogist shall find leisure to -examine the courses of the great rivers, the Dee, the Spey, &c. which -traverse this country. If we call it one-fourth of the whole surface, -its extent is certainly not underrated, and will amount to 790 square -miles nearly; to which adding 150, as a very full allowance for all the -other granite contained in Scotland, exclusive of the isles, we shall -have 940 square miles, between a twenty-fourth and twenty-fifth part of -the surface of the whole. - -This computation, it must be observed, aims at nothing precise, but I -think it is such, that a more accurate survey would rather diminish -than increase the proportion assigned in it to the granite rock. - -314. This result may perhaps fall as much short of Mr Kirwan's notion, -as it exceeds the estimate made by Dr Hutton. If it shall not, and if -the former has, in this instance, come nearest the truth, it cannot -be ascribed to the accuracy of his information, or the soundness of -the principles which directed his research. Mr WILLIAMS, whom he -quotes, was a miner, of great skill and experience in some branches -of his profession, to which, if he had confined himself, he might -have written a book full of useful information. What he says on the -subject of granite, is, in the main I believe just; but it is far too -general to authorize the conclusion which Mr Kirwan derives from it. -Dr Ash, for whose judgment I have great respect, cannot, I think, have -meant, when he used the expression granitic rocks, to describe granite -strictly so called. He says, in the passage quoted by Mr Kirwan, that -"from Galloway, Dumfries, and Berwick, there is a chain of mountains, -commonly schistose, but often also granitic." Now, the fact is, that -the great belt of primary rock, here alluded to, which traverses the -south of Scotland, consists of vertical schistus of various kinds; -but except in Galloway, and again in Lammermuir, near Priestlaw, it -appears, as already mentioned, to contain no granite whatsoever. If the -German mineralogist quoted by Mr Kirwan, when he says that the Grampian -mountains consist of micaceous limestone, gneiss, porphyry, argillite, -and granite, alternating with one another, means only to affirm that -all these stones are found in the Grampians, he is certainly in the -right, and the catalogue might easily be enlarged; but, if he either -means to say, that these are nearly in equal abundance, or that the -granite is commonly found in strata alternating with other strata, I -must say, that these are propositions quite contrary to any thing -I have ever seen or heard of those mountains. But it is probable -that this is not meant, and that the fault lies in understanding -the expressions much too literally. Mr Kirwan accuses Dr Hutton of -not knowing where to look for the granite; not aware of how much, -notwithstanding any error committed in the present estimate, he was -skilled in the art of mineralogical observation; an art, which those -who have not practised do not always know how to appreciate. But, -however imperfect Mr Kirwan's knowledge of this subject has been, -he has here had the good fortune to correct a mineralogist of very -superior information. The mere disposition to oppose is not always -without its use: no man is in every thing free from error, and, to -controvert indiscriminately all the opinions of any individual, is an -infallible secret for being sometimes in the right. - - - - - NOTE XVI. § 100. - - _Rivers and Lakes._ - - -315. Rivers are the causes of waste most visible to us, and most -obviously capable of producing great effects. It is not, however, in -the greatest rivers, that the power to change and wear the surface of -the land is most clearly seen. It is at the heads of rivers, and in the -feeders of the larger streams, where they descend over the most rapid -slope, and are most subject to irregular or temporary increase and -diminution, that the causes which tend to preserve, and those that tend -to change the form of the earth's surface, are farthest from balancing -one another, and where, after every season, almost after every flood, -we perceive some change produced, for which no compensation can be -made, and something removed which is never to be replaced. When we -trace up rivers and their branches toward their source, we come at -last to rivulets, that run only in time of rain, and that are dry, at -other seasons. It is there, says Dr Hutton, that I would wish to carry -my reader, that he may be convinced, by his own observation, of this -great; fact, _that the rivers have, in general, hollowed out their -valleys_. The changes of the valley of the main river are but slow; -the plain indeed is wasted in one place, but is repaired in another, -and we do not perceive the place from whence the repairing matter has -proceeded. That which the spectator sees here, does not therefore -immediately suggest to him what has been the state of things before -the valley was hollowed out. But it is otherwise in the valley of the -rivulet; no person can examine it without seeing, that the rivulet -carries away matter which cannot be repaired, except by wearing away -some part of the surface of the place upon which the rain that forms -the stream is gathered. The remains of a former state are here visible; -and we can, without any long chain of reasoning, compare what has been -with what is at the present moment. It requires but little study to -replace the parts removed, and to see nature at work, resolving the -most hard and solid masses, by the continued influences of the sun and -atmosphere.[161] We see the beginning of that long journey, by which -heavy bodies travel from the summit of the land to the bottom of the -ocean, and we remain convinced, that, _on our continents, there is no -spot on which a river may not formerly have run_.[162] - -[Footnote 161: Theory of the Earth, vol. ii. 294.] - -[Footnote 162: _Ibid._ p. 296.] - -316. The view thus afforded of the operations, in their nascent state, -which have shaped out and fashioned the present surface of the land, -is necessary to prepare us for following them to the utmost extent -of their effects. From these effects, the truth of the proposition, -that rivers have cut and formed, not the beds only, but the whole of -the valleys, or rather system of valleys, through which they flow, is -demonstrated on a principle which has a close affinity to that on which -chances are usually calculated, § 99. In order to conceive rightly the -course of a great river, and the communication subsisting between the -main trunk and its remotest branches, let us take the instance of the -Danube and cast our eyes on one of the maps constructed by MARSIGLI, -for illustrating the natural history of that great river.[163] When -it is considered, that over all the vast and uneven surface, which -reaches from the Alps to the Euxine, and from the mountains of Crapack -to those of Hæmus, a regular communication is kept up between every -point and the line of greatest depression, in which the river flows, no -one can hesitate to acknowledge, that it is the agency of the waters -alone which has opened them a free passage through all the intricacies -of this amazing labyrinth. In effect, suppose this communication to be -interrupted, and that some sudden operation of nature were to erect a -barrier of mountains to oppose the Theise or the Drave, as they rolled -their waters to the Danube. From this what could possibly result, but -the damming up of those rivers till their waters were deep, or high -enough to find a vent, either under the bases or over the tops of the -opposing ridge. Thus there would be formed immense lakes and immense -cataracts, which, by filling up what was too low, and cutting down what -was too high, would in time restore such a uniform declivity of surface -as had before prevailed. Just so in the times that are past, whatever -may have been the irregularities of the surface at its first emerging -from the sea, or whatever irregularities may have been produced in -it by subsequent convulsions, the slow action of the streams would -not fail in time to create or renew a system of valleys communicating -with one another, like that which we at present behold. Water, in all -circumstances, would find its way to the lowest point; though, where -the surface was quite irregular, it would not do so till after being -dammed up in a thousand lakes, or dashed in cataracts over a thousand -precipices. Where neither of these is the case; and where the lake and -the cataract are comparatively rare phenomena; there we perceive that -constitution of a surface, which water alone, of all physical agents, -has a tendency to produce; and we must conclude, that the probability -of such a constitution having arisen from another cause, is, to the -probability of its having arisen from the running of water, in such a -proportion as unity bears to a number infinitely great. - -[Footnote 163: Histoire du Danube, tom. i. tab. 34.] - -317. The courses of many rivers retain marks that they once consisted -of a series of lakes, which have been converted into dry ground, by the -twofold operation of filling up the bottoms, and deepening the outlets. -This happens, especially, when successive terraces of gravelly and -flat land are found on the banks of a river, § 100. Such platforms, or -_haughs_ as they are called in this country, are always proofs of the -waste and _detritus_ produced by the river, and of the different levels -on which it has run; but they sometimes lead us farther, and make it -certain, that the great mass of gravel which forms the successive -terraces on each side of the river, was deposited in the basin of a -lake. If, from the level of the highest terrace, down to the present -bed of the river, all is alluvial, and formed of sand and gravel, it -is then evident, that the space as low as the river now runs must have -been once occupied by water; at the same time, it is dear, that water -must have stood, or flowed as high at least, as the uppermost surface -of the meadow. It is impossible to reconcile these two facts, which are -both undeniable, but by supposing a lake, or body of stagnant water, -to have here occupied a great hollow, (which by us must be held as -one of the original inequalities of the globe, because we can trace -it no farther back,) and that this hollow, in the course of ages, has -been filled up by the gravel and alluvial earth brought down by the -river, which is now cutting its channel through materials of its own -depositing. There is no great river that does not afford instances -of this, both in the hilly part of its course, and where it descends -first from thence into the plain. Were there room here for the minuter -details of topographical description, this might be illustrated by -innumerable examples. - -318. It is said above, that the water must have run or stood, in -former times, as low as the present bottom of the river; but there is -often clear evidence, that it has run or stood much lower, because the -alluvial land reaches far below the present level of the river. This is -known to hold in very many instances, where it has happened that pits -have been sunk to considerable depths on the banks of large rivers. By -that means, the depth of the alluvial ground, under the present bed of -the river, has been discovered to be great; and from this arises the -difficulty, so generally experienced, of finding good foundations for -bridges that are built over rivers in large valleys, or open plains, -the ground being composed of travelled materials to an unknown depth, -without any thing like the native or solid strata. In such cases, it -is evident, that formerly the water must have been much lower, as well -as much higher, than its present level, and this is only consistent -with the notion, that the place was once occupied by a deep lake. - -319. If, following the light derived from these indications, we go -back to the time when the river ran above the highest of those levels -at which it has left any traces of its operations, we shall see it -composed of a series of lakes and cataracts, from which, by the -filling up of the one, and the wearing down of the other, the waters -have at length worked out to themselves a quiet and uninterrupted -passage to the ocean. We may, indeed, on good evidence, go back still -farther than the succession of such meadows or terraces, as are above -mentioned, will carry us, and may consider the whole valley, or -trough of the river, as produced by its own operations. The original -inequalities of the surface, and the disposition of the strata, must -no doubt have determined the water courses at first; but this does not -hinder us from considering the rivers as having modified and changed -those inequalities, and as the proximate causes of the shape and -configuration which the surface has now assumed. - -320. From this gradual change of lakes into rivers, it follows, that -a lake is but a temporary and accidental condition of a river, which -is every day approaching to its termination; and the truth of this is -attested, not only by the lakes that have existed, but also by those -that continue to exist. Where any considerable stream enters a lake, -a flat meadow is usually observed increasing from year to year. The -soil of this meadow is disposed in horizontal strata: the meadow is -terminated by a marsh; which marsh is acquiring solidity, and is soon -to be converted into a meadow, as the meadow will be into an arable -field. All this while the sediment of the river makes its way slowly -into the lake, forming a mound or bank under the surface of the water, -with a pretty rapid slope toward the lake. This mound increases by the -addition of new earth, sand, and gravel, poured in over the slope; and -thus the progress of filling up continually advances. - -321. In small lakes, this progress may easily be traced; and will be -found singularly conspicuous in that beautiful assemblage of lakes, -which so highly adorns the mountain scenery of Westmoreland and -Cumberland. Among these a great number of instances appear, in which -lakes are either partially filled up, or have entirely disappeared. In -the Lake of Keswick, we not only discover the marks of filling up at -the upper end, which extend far into Borrowdale, from which valley a -small river flows into the lake; but we have the clearest proof, that -this lake was once united to that of Bassenthwaite, and occupied the -whole valley from Borrowdale to Ouse-Bridge. These two lakes are at -present joined only by a stream, which runs from the former into the -latter, and their continuity is interrupted by a considerable piece of -alluvial land, composed of beds of earth and gravel, without rock, or -any appearance of the native strata. This separation, therefore, seems -no other than a _bar_, formed by the influx of two rivers, that enter -the valley here from opposite sides, the Greata from the east, and -Newland's water from the west. The surface of this meadow is at present -twelve or fifteen feet at least above the level of either lake and a -quantity of water of that depth must therefore have been drawn off by -the deepening of the issue at Ouse-Bridge, through which the water of -both lakes passes, in its way to the ocean. - -Many more examples, similar to this, may be collected from the same -lakes; there are indeed few places from which, in this branch of -geology, more information may be collected. - -322. The larger lakes exemplify the same progress. Where the Rhone -enters the Lake of Geneva, the beach has been observed to receive an -annual increase; and the Portus Valesiæ, now Port Valais, which is at -present half a league from the lake, was formerly close upon its bank. -Indeed, the sediments of the Rhone appear clearly to have formed the -valley through which it runs, to a distance of about three leagues at -least from the place where the river now discharges itself into the -lake. The ground there is perfectly horizontal, composed of sand and -mud, little raised above the level of the river, and full of marshes. -The deposition made by the Rhone after it enters the lake, is visible -to the eye; and may be seen falling down in clouds to the bottom. - -The great lakes of North America are undergoing the same changes, and, -it would seem, even with more rapidity. As the rivers, however, which -supply these vast reservoirs, are none of them very great, the filling -up is much less remarkable than the draining off of the water, by the -deepening of the outlet. An intelligent traveller has remarked, that -in Lake Superior itself the diminution of the waters is apparent, -and that marks can be discovered on the rocks, of the surface having -been six feet higher than it is at present. In the smaller lakes this -diminution is still more evident.[164] In some of those far inland, the -ground all round appeared to the same traveller to be the deposit from -the rivers, of which the lakes themselves may be considered as a mere -expansion.[165] - -[Footnote 164: Mackenzie's Voyages through the Continent of North -America to the Frozen and Pacific Oceans, p. xlii. and xxxvi.] - -[Footnote 165: _Ibid._ p. 122.] - -323. In order to give uniform declivities to the rivers, the lakes -must not only be filled up or drained, but the cataract, wherever -there is one, must be worn away. The latter is an operation in all -cases visible. The stream, as it precipitates itself over the rocks, -hurries along with it, not only sand and gravel, but occasionally large -stones, which grind and wear down the rock with a force proportioned -to their magnitude and acceleration. The smooth surface of the rocks -in all waterfalls, their rounded surface, and curious excavations, -are the most satisfactory proofs of the constant attrition which they -endure; and, where the rocks are deeply intersected, these marks -often reach to a great height above the level on which the water now -flows. The phenomena, in such instances, are among the arguments best -calculated to remove all incredulity respecting the waste which rivers -have produced, and are continuing to produce. They suffer no doubt to -remain, that the height and asperity of every waterfall are continually -diminishing; that innumerable cataracts are entirely obliterated; that -those which remain are verging toward the same end, and that the Falls -of Montmorenci and Niagara must ultimately disappear. - -324. Though there can be no doubt of the justness of the preceding -conclusions, when applied to lakes in general, some apparent -exceptions occur, in which the progress of draining and filling up -seems to have been suspended, or even to have gone in a contrary -direction. These exceptions consist of the lakes which appear to -have received a greater quantity of materials than was sufficient to -have filled them up. Such, for example, is the Lake of Geneva, which -receives the Rhone descending from the Valais, one of the deepest and -longest valleys on the surface of the earth. Now, if this valley, or -even a large proportion of it, had been excavated by the Rhone itself, -as our theory leads us to suppose, the lake ought to have been entirely -filled up, because the materials brought down by the river seem to be -much greater than the lake, on any reasonable supposition concerning -its original magnitude, can possibly have received. What, then, it -may be said, has become of all that the Rhone has brought down and -deposited in it? The lake, at this moment, retains, in some places, the -depth of more than 1000 feet; and yet, of all that the Rhone carries -into it, nothing but the pure water issues. If it has been continuing -to diminish, both in superficial extent and in depth, from the time -when the Rhone began to run into it, what must have been its original -dimensions? - -I cannot pretend to remove entirely the difficulty which is here -stated; yet I think the following remarks may go some length in doing -so. - -325. It is certain, that from the present state of the Lake of Geneva, -and of the ground round it, we can hardly draw any inference as to its -original dimensions. Saussure has traced, with his usual skill, the -marks of the course of the Rhone, on a level greatly above the present; -and, by observations on the side of Mont Saleve, has found proofs of -the running of water, at least 200 toises above the present superficies -of the lake. But, if ever the superficies of the lake stood at this -height, or at this height nearly, though we can conjecture but little -concerning the state of the adjacent country, which no doubt was also -on a higher level, the lake may very well be supposed to have been of -far greater dimensions than it is now. It may have occupied the whole -space from Jura to Saleve, and included the Lake of Neufchâtel; so -that it may have been of magnitude sufficient to receive the spoils of -the Valais, which, as the surface of its waters lowered, may have been -washed away and carried down to the sea. Thus it may have afforded a -temporary receptacle for the _debris_ of the Alps, and may have served -for an _entrepot_, as it were, where those _debris_ were deposited, -before they were carried to the place of their ultimate destination. - -326. But the great depth which the lake has at present, still remains -to be explained, because no mud or gravel could be carried beyond the -gulf, of a thousand feet deep, which was here ready to receive it. The -reality of this difficulty must be acknowledged; and some cause seems -to act, if not in the generation, yet certainly in the preservation of -lakes, with which we are but little acquainted We can indeed imagine -some causes of that kind to occur in the course of the degradation -of the land, which may produce new lakes, or increase the dimensions -of the old. The wearing away of a stratum, or body of strata, may -lay bare, and render accessible to the water, some beds of mineral -substances soluble in that fluid. The district, for instance, in -Cheshire, which contains rock-salt, extends over a tract of fourteen or -fifteen miles, and is covered by a thick stratum of clay, more or less -indurated, which defends the salt from the water at the surface, and -preserves the whole mass in a state of dryness. Should this covering be -broke open by any natural convulsion, or should it be worn away, as it -must be in the progress of the general detritus, the water would gain -admission to the saline strata, would gradually dissolve them, and -form of course a very deep and extensive lake, where all was before dry -land. This event is not only possible, but it should seem, that in the -course of things it must necessarily happen. - -327. Something of this kind may have taken place in the track of the -Rhone, and may have produced the Leman Lake. It is not impossible, -that, at a very remote period, the Rhone descended from the Alps -without forming any lake, or at least any lake of which the remains are -now existing; and this supposition, which is more probable than that of -§ 325, we shall soon find to be conformable to appearances of another -kind. The river may have wore away the secondary limestone strata over -which it took its course after it left the schistus of the mountains; -and, in doing so, may have reached some stratum of a saline nature, and -this being washed out, may have left behind it a lake, which is but -modern compared with many of the revolutions that have happened on the -surface of the earth.[166] - -[Footnote 166: There are salt springs at Bex, near Aigle, about ten -miles from the head of the lake: saline strata, therefore, are probably -at no great distance.] - -This explanation is no doubt hypothetical; but it is proposed in one -of those cases, in which hypothetical reasonings are warranted by -the strictest rules of philosophical investigation. It is proposed -in a case, where the causes visible to man seem inadequate to the -effect, and where we must therefore have recourse to an agent that is -invisible. If the operations ascribed to this agent are conformable to -the analogy of nature, it is all that can in reason be required. - -328. Another circumstance may also influence the generation and -preservation of lakes; but it is also one with which we are but little -acquainted. The strata, and indeed the whole body of mineral substances -which forms the basis of our land, have been raised up from the bottom -of the sea, by a progress that should seem in general to have been -gradual and slow. Appearances, however, are not wanting, which show, -that this progress is not uniform; and that both rising and sinking in -the surface of the land, or in the rocks which are the base of it, have -happened within a period of time, which is by no means of great extent. -In this progress, the elevations and depressions may not be the same -for every spot. They may be partial, and one part of a stratum, or body -of strata, may rise to a greater height, or be more depressed, than -another. It is not impossible, that this process may affect the depth -of lakes, and change the relative level of their sides and bottom. - -329. All lakes, however, do not involve the difficulty which the -preceding conjectures are intended to remove. The great lakes of North -America do not, for instance, receive their supply from very large -rivers. Of course, it is not from a tract great in comparison of -themselves, that the waste and detritus is brought down into them; and -it seems not at all wonderful, that, without being filled up, they have -been able to receive it. The same, in a degree at least, is true of -many other lakes. - -It should also be considered, that we may err greatly in the estimate -we make of the materials actually carried down and deposited in any -lake. To judge of their entire amount, we should know the original -form of the inequalities on the earth's surface; of the quantity of -depression which existed, independently of the rivers; and though, -in general, these original inequalities may be overlooked, and the -present considered as made by the running of water, yet, in particular -instances, this may be far from true. The Valais, for example, which -we consider as the work of the Rhone, may, when the Alps rose out of -the sea, have included many depressions of the surface, which the river -joined together, and, from being a series of lakes, formed into one -great valley. - - * * * * * - -330. The mouths by which rivers on bold rocky coasts discharge their -waters into the sea, afford a very striking confirmation of the -conclusions concerning the general system of waste and degradation -which have been drawn above. At these mouths we usually see, not only -the bed of the river, but frequently a considerable valley, cut out -of the solid rock, while that rock preserves its elevation, and its -precipitous aspect, wherever it is not intersected by a run of water. -No convulsion that can have torn asunder the rocks; no breach that can -have been made in them, antecedent to the running of the waters, will -account for the circumstance of every river finding a corresponding -opening, by which it makes its way to the sea; for that opening being -so nearly proportional to the magnitude of the river, and for such -breaches never occurring but where streams of water are found. - -331. The actual survey of any bold and rocky coast, will make this -clearer than any general statement can possibly do. Let us take, for an -example, the coast of the British Channel, from Torbay to the Land's -End, which is faced by a continued rampart of high cliffs, formed -of much indurated and primeval rock. If we consider the breaches in -this rampart, at the mouths of the Dart, of the Plym and Tamer, of -the river at Fowey, of the Fal, the Hel, &c. it will appear perfectly -clear, that they have been produced by their respective streams. Where -there is no stream, there is no breach in the rock, no softening in -the bold and stern aspect which this shore every where presents to the -ocean. If we look at the smaller streams, we find them working their -way through the cliffs at the present moment; and we see the steps by -which the larger valleys of the Dart and the Tamer have been cut down -to the level of the sea. If we would have still clearer evidence, that -no breaches made antecedently to the running of the rivers have opened -a way for them, we need only look to the opposite side, or northern -shore, of the same promontory, where we also find a series of outlets, -all originating in the ridge of the country, and becoming deeper as -they approach the sea, but altogether unconnected with the openings -on the south side; and this could hardly have been the case, had they -been the effects of previous concussions, or of any peculiarity in the -original structure of the rocks. - -332. In contemplating such coasts as these, when we go back to the -time when the rivers ran upon a level as high as the highest of the -cliffs on the sea shore, we must suppose, that the land then extended -many miles farther into what is now occupied by the sea. When at -Plymouth, for instance, the Tamer and the Plym flowed on the level of -Mount Edgecombe or of Staten Heights, if the rivers ran with a moderate -declivity into the sea, the coast must have advanced many miles beyond -its present line. Thus the land, when higher, was also more extended, -and the limits of our island in that ancient state, were doubtless very -different from these by which it is at present circumscribed. - -If with the same views we consider any other of the bold coasts which -the map of the world presents us with, we shall quickly remark, that -wherever a deep intersection of the sea is made into the land, as on -the western shores of our own island, or on those of Norway, a river -runs in at the head of it, and points out by what means such inlets -are formed, viz. by the united powers of the sea and of the land, the -waters of the latter having opened the way by which those of the former -have penetrated so far into the country. - -333. It is not meant assuredly to deny the irregularities of the sea -coast, as it may have originally existed; these irregularities no doubt -determined the initial operations of that waste and decay, by which, in -process of time, they were themselves entirely effaced. The line of -our coasts may be compared to one of those curves, which are sometimes -treated of in the higher geometry, where the ordinates are functions, -not only of, their abscissæ, but also of the time elapsed since a -certain epocha. The form of the curve at that epocha, or when the time -began to flow, corresponds to the original form of the sea coast, on -its emerging from the ocean, and before the powers of wasting and decay -had begun to act upon it. To speak strictly, the original figure, in -both cases, influences all the subsequent; but the farther removed from -it in point of time, the less is that influence; so that, in physical -questions, and for the purpose of such approximations as suit the -imperfection of our knowledge, the consideration of the original figure -may be wholly left out. - - - - - NOTE XVII. § 105. - - _Remains of Decomposed Rocks._ - - -334. THE plain of Crau was the _Campus Lapideus_ of the ancients; and, -as mythology always seeks to connect itself with the extraordinary -facts in natural history, it was said to be the spot where Hercules, -fighting with the sons of Neptune, and being in want of weapons, was -supplied from heaven by a shower of stones: hence it was called _Campus -Herculeus_. - -This plain is on the east side of the Rhone, between Salon and Aries: -it is of a triangular form, about twenty square leagues in extent, and -is covered almost entirely with quartzy gravel. This immense collection -of gravel has been supposed by some to have been brought down by the -Durance from the Alps of Dauphine; by others it has been ascribed to -the Rhone; and by many to the sea, as being a work too great for any -river. The explanation mentioned above, § 105, namely, that the loose -gravel on the plain arises from the decomposition of a great stratum -of pudding-stone, which is the basis of the whole, is the opinion of -Saussure, and is founded on his own observations.[167] - -[Footnote 167: See Voyages aux Alpes, tom. iii. § 1592 et 1597. See -also on this subject a Memoir by Lamanon, Journal de Physique, tom. -xxii. p. 477; and another by M. De Servieres, _ibid._ p. 270.] - -335. The theories that have been contrived for explaining the -phenomena of the plain of Crau, afford an instance of the necessity -of generalizing our observations before we can explain a particular -appearance: in other words, they prove the truth of Lord Bacon's -maxim, That the explanation of a phenomenon should not be sought for -from the study of that phenomenon alone, but from the comparison of it -with others. One of the theories of this plain is, that the breccia, -which is the base of it, is formed from the consolidation of the loose -gravel of the plain, by water percolating through it, and carrying some -cementing substance along with it, or some _lapidific juice_, as it -is called. And indeed, whether the gravel is formed from the breccia, -or the breccia from the gravel, is a question which probably could -never be resolved by the mere examination of the plain itself. But the -question is very soon decided, when we compare what is observed here -with other appearances in the natural history of the earth's surface, -and consider how much more frequent the decomposition of solids is, -than their reconsolidation, in any place above the level of the sea. - -336. The argument for the decomposition of stony substances which is -afforded by the state of this singular plain, may be confirmed by -the appearances observed in many extensive tracts of land all over -the world, and especially in some parts of Great Britain. The road -to Exeter from Taunton Dean, between the latter and Honiton, passes -over a large heath or down, considerably elevated above the plain of -Taunton. The rock which is the base of this heath, as far as can be -discovered, is limestone, and over the surface of it large flints, in -the form of gravel, are very thickly spread. There is no higher ground -in the neighbourhood from which this gravel can be supposed to have -come, nor any stream that can have carried it, so that no explanation -of it remains, but that it is formed of the flints contained in beds -of limestone, which are now worn away. The flints on the heath are -precisely of the kind found in limestone; many of them are not much -worn, and cannot have travelled far from the rock in which they were -originally contained. It seems certain, therefore, that they are the -_debris_ of limestone strata, now entirely decomposed, that once lay -above the strata which at present form the base of this elevated plain, -and probably covered them to a considerable height. This explanation -carries the greater probability with it, that any other way of -accounting for the fact in question, as the travelling of the gravel -from higher grounds, or the immersion of the surface under the sea, -will imply changes in the face of the country, incomparably greater -than are here supposed. Our hypothesis seems to give the _minimum_ of -all the kinds of change that can possibly account for the phenomenon. - -337. The same remarks may be made on the high plain of Blackdown, which -the road passes over in going from Exeter to the westward. The flints -there are disseminated over the surface as thickly as in the other -instance, and can be explained only on the same supposition. - -Again, in the interior of England, beginning from about Worcester -and Birmingham, and proceeding north-east through Warwickshire, -Leicestershire, Nottinghamshire, as far as the south of Yorkshire, a -particular species of highly indurated gravel, formed of granulated -quartz, is found every where in great abundance. This same gravel -extends to the west and north-west, as far as Ashburn in Derbyshire, -and perhaps still farther to the north. The quantity of it about -Birmingham is very remarkable, as well as in many other places; and the -phenomenon is the more surprising, that no rock of the same sort is -seen in its native place. It is such gravel as might be expected in a -mountainous country, in Scotland, for instance, or in Switzerland, but -not at all in the fertile and secondary plains of England. - -This enigma is explained, however, when it is observed, that the basis -of the whole tract just described is a red sandstone, often containing -in it a hard quartzy gravel, perfectly similar to that which has just -been mentioned. From the dissolution of beds of this sandstone, which -formerly covered the present, there can be no doubt that this gravel -is derived. But, as the gravel is in general thinly dispersed through -the sandstone, and abounds only in some of its layers, it should -therefore seem, that a vast body of strata must have been worn away and -decomposed, before such quantities of gravel as now exist in the soil -could have been let loose. - -338. I have said, that a rock capable of affording such gravel as -this, is not to be found in the tract of country just mentioned. -This however, is not strictly true; for in Worcestershire, between -Bromesgrove and Birmingham, about seven miles from the latter, a rock -is found consisting of indurated strata, greatly elevated, and without -doubt primitive, from the detritus of which such gravel as we are -now speaking of might be produced. These strata seem to rise up from -under the secondary, where they are intersected by the road; and, for -as much as appears, are not of great thickness, so that they cannot -have afforded the materials of this gravel directly, though they may -have done so indirectly, or through the medium of the red sandstone; -that is to say, a primary rock of which they are the remains, may have -afforded materials for the gravel in the sandstone; and this sandstone -may in its turn have afforded the materials of the present soil, and -particularly the gravel contained in it. - -339. Pudding-stones being very liable to decomposition, have probably, -in most countries, afforded large proportion of the loose gravel now -found in the soil The mountains, or at least hills, of this rock, which -are found in many places, prove the great extent of such decomposition. -Mount Rigi, for instance, on the side of the Lake of Lucerne, is -entirely of pudding-stone, and is 742 toises in height, measured from -the level of the lake. By the descriptions given of it, as well as -of other hills of the same kind in Switzerland, we may, without due -attention, be led to suppose that they are entirely formed of loose -gravel. Even M. Saussure's description is chargeable with this fault, -though, when attended to, it will be found to contain a sufficient -proof, that this hill is composed of real pudding-stone.[168] The -nature of the thing also, would be sufficient to convince us, that a -hill, more than 4000 feet in height, could not consist of loose and -unconsolidated materials. - -If, then, we regard Mount Rigi as the remains of a body of -pudding-stone strata, we must conclude, that these strata were -originally more extensive, and the adjacent valleys and plains will -serve, in some degree, to measure the quantity of them which time has -destroyed. - -[Footnote 168: Voyages aux Alpes, tom. iv. § 1941.] - -340. If the theory of unstratified mountains, namely those of -whinstone, porphyry, and granite, be admitted as laid down above, it -will furnish a measure of the destruction which has taken place in the -stratified rocks, and of the vast depredations which have been made -upon them since they were raised up from the bottom of the sea. Like -every other measure, however, of wasting, by a thing that is itself -subject to waste, it can only give a _minimum_, or a limit which the -quantity wasted must necessarily exceed. - -The abrupt face of a whinstone rock must be understood as an evidence, -that some body of strata which supported it when fluid, remained -in contact with it, when it was become solid; and if this part of -the mould in which the whinstone was cast, has disappeared, it must -generally be ascribed to the operation of waste and decomposition. -Such a face, for instance, as that which Salisbury _Craig_ presents to -the west, viz. a perpendicular wall of whinstone, about ninety feet -high, raised on a body of sandstone strata of the height of about -300 feet, can have been produced only by having been abutted against -some stratified rock, equally abrupt, and of the same elevation with -itself. Of this rock no part remains. - -The basaltic rock of Edinburgh Castle is nearly in the same state. Its -perpendicular sides on the south, west, and north, are now disengaged -from the strata by which they were once encompassed. - -341. The granite mountains also, where they are quite unstratified, -give rise to the same conclusion. Those central chains which we find -in so many instances towering above the schistus which cover their -sides, have probably been once completely enveloped by the latter; -and, on this supposition, an estimate may sometimes be formed of the -original height of such mountains. In these estimations, however, some -uncertainty must arise, from our being unable to distinguish between -the effects which are to be ascribed to the fracture and dislocation -that took place when the compound body of stratified and unstratified -rocks was raised up from the bottom of the sea, and the effects -produced by the subsequent waste and decomposition at the surface. In -this, as in many other instances, we are not always able to separate -between the original inequalities of the surface, and those which -wearing has produced. - -342. It would be important to ascertain the rate at which the elevation -of mountains decreases, and this is what we may perhaps expect to -be accomplished, by the progress of geological science, and the -multiplying of accurate observations. It has been supposed, that the -Pyrenees diminish about ten inches in a century; but what confidence is -to be put in this estimate, I am unable to determine.[169] - -[Footnote 169: Essai sur la Mineralogie des Pyrenées, p. 87.] - -A very unequivocal mark of the degradation of mountains is often to -be met with in the heaps of loose stones found on their tops. These -stones, it is obvious, cannot have come from any other place by natural -means, and they are accordingly always sharp and angular, and have none -of the characters of transported rocks. They are said sometimes to -have been brought by men's hands; but this is highly improbable, their -quantity is often so considerable, and the difficulty of transportation -so great. Where any purpose was to be served by heaping them together, -men have availed themselves of the stones that they found ready -prepared on the summit, and have constructed from them cairns, which -have served as signals, useful in their pastoral, and sometimes in -their military occupations. - - - - - NOTE XVIII. § 112. - - _Transportation of Stones, &c._ - - -343. NATURE supplies the means of tracing with considerable certainty -the migration of fossil bodies on the surface of the earth, as only -the more indurated stones, and those most strongly characterized, can -endure the accidents that must befal them in travelling to a distance -from their native place. - -It is a fact very generally observed, that where the valleys among -primitive mountains open into huge plains, the gravel of those plains -consists, of stones, evidently derived from the mountains. The nearer -that any spot is to the mountains, the larger are the gravel stones, -and the less rounded is their figure; and, as the distance increases, -this gravel, which often forms a stratum nearly level, is covered -with a thicker bed of earth or vegetable soil. This progression has -particularly been observed in the valleys of Piémont and the plains of -Lombardy, where a bed of gravel forms the basis of the soil, from the -foot of the Alps to the shores of the Hadriatic.[170] We may collect -from GUETTARD, that a similar gradation is found in the gravel and -earth which cover the great plain of Poland, from Mount Krapack to the -Baltic.[171] The reason of this gradation is evident; the farther the -stones have travelled, and the more rubbing they have endured, the -smaller they grow, the more regular is the figure they assume, and the -greater the quantity of that finer detritus which constitutes the soil. -The washing of the rains and rivers is here obvious; and each of the -three quantities just mentioned, if not directly proportional to the -distance which the stones have migrated from their native place, may -be said, in the language of geometry, to be at least proportional to a -certain function of that distance. - -[Footnote 170: Voyages aux Alpes, tom. iii. § 1315.] - -[Footnote 171: Mém. Acad. des Sciences, 1762, p. 234, 293, &c.] - -344. The immense quantity of _cailloux roulés_, or rounded gravel, -collected in the immediate vicinity of mountainous tracts, has led -some geologists to suppose the existence of ancient currents, which -descended from the mountains, in a quantity, and with a _momentum_, -of which there is no example in the present state of the world. Thus -Saussure imagines, that the hill of Supergue, near Turin, which is -formed of gravel, can only be explained by supposing such currents as -are just mentioned, or what he terms a _debacle_, to have taken place -at some former period.[172] If, however, we ascribe to the mountains -a magnitude and elevation vastly greater than that which they now -possess; if we regard the valleys between them as cut out by the rivers -and torrents from an immense rampart of solid rock, neither materials -sufficiently great, nor agents sufficiently powerful, will appear to -be wanting, for collecting bodies of gravel and other loose materials, -equal to any that are found on the surface of the earth. The necessity -of introducing a _debacle_, or any other unknown agent, to account for -the transportation of fossils, seems to arise from underrating the -effects of action long continued, and not limited by such short periods -as circumscribe the works, and even the observations, of men. - -[Footnote 172: Voyages aux Alpes, tom. iii. § 1303.] - -345. The supply of gravel and _cailloux roulés_, for the plains -extended at the feet of primitive mountains, is doubtless in many cases -much increased by the pudding-stone, interposed between the secondary -and the primary strata. The beds of pudding-stone contain gravel -already formed on the shores of continents, that ceased to exist before -the present were produced; and the cement of this gravel, yielding -easily to the weather, allows the stones included in it to be washed -down by the torrents, and scattered over the plains. I know not if -the hill of Supergue above mentioned, is not in reality a mass of the -pudding-stone which forms the border of the Alps, and of which the -materials have suffered no transportation since the time of their last -consolidation. This at least is certain, that Saussure, notwithstanding -his accuracy, has sometimes confounded the loose gravel on the surface -with that which is consolidated into rock; an inaccuracy which is to be -charged, as I have elsewhere observed, rather against his system than -himself. - -346. The loose stones found on the sides of hills, and the bottoms -of valleys, when traced back to their original place, point out with -demonstrative evidence the great changes which have happened since the -commencement of their journey; and in particular serve to show, that -many valleys which now deeply intersect the surface, had not begun to -be cut out when these stones were first detached from their native -rocks. We know, for instance, that stones under the influence of such -forces as we are now considering, cannot have first descended from one -ridge, and then ascended on the side of an opposite ridge. But the -granite of Mont Blanc has been found, as mentioned above, on the sides -of Jura, and even on the side of it farthest from the Alps. Now, in -the present state of the earth's surface, between the central chain of -the Alps, from which these pieces of granite must have come, and the -ridge of Mont Jura, besides many smaller valleys, there is the great -valley of the Rhone, from the bottom of which, to the place where they -now lie, is a height of not less than 3000 feet. Stones could not, by -any force that we know of, be made to ascend over this height. We must -therefore suppose, that when they travelled from Mont Blanc to Jura, -this deep valley did not exist, but that such an uniform declivity, as -water can run on with rapidity, extended from the one summit to the -other. This supposition accords well with what has been already said -concerning the recent formation of the Leman Lake, and of the present -valley of the Rhone. - -347. We can derive, in a matter of this sort, but little and from -calculation; yet we may discover by it, whether our hypothesis -transgresses materially against the laws of probability, and is -inconsistent with physical principles already established. The -horizontal distance from Mont Jura to the granite mountains, at the -head of the Arve, may be accounted fifty geographic miles. Though -we suppose Mont Blanc, and the rest of those mountains, to have been -originally much higher than they are at present, the ridge of Jura must -have been so likewise; and though probably not by an equal quantity, -yet it is the fairest way to suppose the difference of their height to -have been nearly the same in former ages that it is at present, and -it may therefore be taken at 10,000 feet. The declivity of a plane -from the top of Mont Jura to the top of Mont Blanc, would therefore be -about one mile and three quarters in fifty, or one foot in thirty; an -inclination much greater than is necessary for water to run on, even -with extreme rapidity, and more than sufficient to enable a river or -a torrent to carry with it stones or fragments of rock, almost to any -distance. - -Saussure, in relating the fact that pieces of granite are found among -the high passes near the summits of Mont Jura, alleges, that they are -only found in spots from which the central chain of the Alps may be -seen. But it should seem that this coincidence is accidental, because, -from whatever cause the transportation of these blocks has proceeded, -the form of the mountains, especially of Mont Jura, must be too much -changed to admit of the supposition, that the places of it from which -Mont Blanc is now visible, are the same from which that mountain was -visible when these stones were transported hither. It may be, however, -that the passes which now exist in Mont Jura are the remains of valleys -or beds of torrents, which once flowed westward from the Alps; and it -is natural, that the fragments from the latter mountains should be -found in the neighbourhood of those ancient water-tracks. - -348. Saussure observed in another part of the Alps, that where the -Drance descends from the sides of Mont Velan and the Great St Bernard, -to join the Rhone in the Valais, the valley it runs in lies between -mountains of primary schistus, in which no granite appears, and yet -that the bottom of this valley, toward its lower extremity, is for -a considerable way covered with loose blocks of granite.[173] His -familiar acquaintance with all the rocks of those mountains, led him -immediately to suspect, that these stones came from the granite chain -of Mont Blanc, which is westward of the Drance, and considerably higher -than the intervening mountains. This conjecture was verified by the -observations of one of his friends, who found the stones in question to -agree exactly with a rock at the point of Ornes, the nearest part of -the granite chain. - -[Footnote 173: Voyages aux Alpes, tom. ii. § 1022.] - -In the present state of the surface, however, the valley of Orsiere -lies between the rocks of Ornex and the valley of the Drance, and would -certainly have intercepted the granite blocks in their way from the one -of these points to the other, if it had existed at the time when they -were passing over that tract. The valley of Orsiere, therefore, was not -formed, when the torrents, or the glaciers transported these fragments -from their native place. - -Mountainous countries, when carefully examined, afford so many facts -similar to the preceding, that we should never have done were we -to enumerate all the instances in which they occur. They lead to -conclusions of great use, if we would compare the machinery which -nature actually employs in the transportation of rocks, with the -largest fragments of rock which appear to have been removed, at some -former period, from their native place. - -349. For the moving of large masses of rock, the most powerful engines -without doubt which nature employs are the glaciers, those lakes or -rivers of ice which are formed in the highest valleys of the Alps, -and other mountains of the first order. These great masses are in -perpetual motion, undermined by the influx of heat from the earth, and -impelled down the declivities on which they rest by their own enormous -weight, together with that of the innumerable fragments of rock with -which they are loaded. These fragments they gradually transport to -their utmost boundaries, where a formidable wall ascertains the -magnitude, and attests the force, of the great engine by which it was -erected. The immense quantity and size of the rocks thus transported, -have been remarked with astonishment by every observer,[174] and -explain sufficiently how fragments of rock may be put in motion, even -where there is but little declivity, and where the actual surface of -the ground is considerably uneven. In this manner, before the valleys -were cut out in the form they now are, and when the mountains were -still more elevated, huge fragments of rock may have been carried to a -great distance; and it is not wonderful, if these same masses, greatly -diminished in size, and reduced to gravel or sand, have reached the -shores, or even the bottom, of the ocean. - -[Footnote 174: The stones collected on the _Glacier de Miage_, when -Saussure visited it, were in such quantity as to conceal the ice -entirely. Voyages aux Alpes, tom. ii. § 854.] - -350. Next in force to the glaciers, the torrents are the most powerful -instruments employed in the transportation of stones. These, when -they descend from the sides of mountains, and even where the declivity -of their course is not very great, produce effects which nothing but -direct experience could render credible. The fragments of rock which -oppose the torrent, are rendered specifically lighter by the fluid -in which they are immersed, and lose by that means at least a third -part of their weight: they are, at the same time, impelled by a force -proportional to the square of the velocity with which the water rushes -against them, and proportional also to the quantity of gravel and -stones which it has already put in motion. Perhaps, after taking all -these circumstances into computation, in the midst of a scene perfectly -quiet and undisturbed, a philosopher might remain in doubt as to the -power of torrents to move the enormous bodies of rock which are seen -in the bottom of the narrow valleys or deep glens of a mountainous -country; but his incredulity, says an experienced traveller, will -cease altogether, if he has been surprised by a storm in the midst of -some Alpine region; if he has seen the number and impetuosity of the -cataracts which rushed down the sides of the mountains, and beheld the -ruin which accompanied them; and if, when the tempest was passed, he -has viewed those meadows, which a few hours before were covered with -verdure, now buried under heaps of stones, or overwhelmed by masses of -liquid mud, and the sides of the mountains cut by deep ravines, where -the track of the smallest rivulet was not before to be discovered.[175] - -[Footnote 175: See an account of a thunder storm near Bareges, in the -Essai sur la Mineralogie des Pyrenées, p. 134.] - -It is but rarely, however, even on occasions like these, that such -vast masses of rock can be seen actually in motion, as are often found -on the surface, apparently removed to a great distance from their -native place. The magnitude of these is so great, in many instances, -that their transportation cannot be explained without supposing, -that the surface was very different when these transportations took -place from what it is at present; that the elevation of the mountains -was greater, and the ground smoother and more uniform, at least in -some directions. If these suppositions are admitted, and they are -countenanced, as we have already seen, by almost every phenomenon in -geology, the difficulties which present themselves here will not appear -insurmountable. - -351. One of the largest blocks of granite that we know of, is on -the east side of the lake of Geneva, called _Pierre de Gouté_, -about ten feet in height, with a horizontal section of fifteen by -twenty.[176] Another block not far from it, and nearly of the same -size, has some remains of schistus attached to it. These stones very -much resemble those which have fallen from the _Aiguilles_, in the -valley of Chamouni. The distance from their present situation to those -_Aiguilles_ is about thirty English miles, with many mountains and -valleys at present interposed. By whatever means, therefore, these -blocks were transported, their motion must have been over a surface -of much more uniform declivity than the present. If the surface was -without great inequalities, and its general declivity about one foot -in thirty, as already computed, the glaciers, in the first place, and -the torrents afterwards, may have served for the transportation even of -these rocks. - -[Footnote 176: Voyages aux Alpes, tom. i. § 308.] - -352. Again, in the narrow vale or glen which separates the Great from -the Little Saleve, the strata are all calcareous, but a great number -of loose blocks of granite and primary schistus are scattered over the -surface. A block of the former, near the lower end of the valley, is -about the size of 1200 cubic feet. Two other large blocks of the same -kind of stone rest on a base of horizontal limestone, elevated two -or three feet above the rest of the surface. This elevation arises -no doubt from the protection which the stones have afforded to the -calcareous beds on which they lie, so that these beds do not wear away -so fast as those which are fully exposed to the weather. But it is -surely to take a very limited view of the operations on the surface, -to suppose, with Saussure, that the parts of the calcareous rock under -these stones has suffered no waste whatsoever, so that the stones -remain now in the identical spot where they were placed by the great -_debacle_ which brought them down from the high Alps.[177] For my part, -I have no doubt that the Arve, which is still at no great distance, -when it ran on a higher level, and in a line different from the -present, aided by the glaciers and superior elevation of the mountains, -was an engine sufficiently powerful for effecting the transportation of -these stones. - -[Footnote 177: _Ibid._ § 227.] - -353. These phenomena are not peculiar to the Alps, but prevail, in -a greater or less degree, in the vicinity of all primary or granite -mountains. In the island of Arran, a fragment of the same kind with -that which constitutes the upper part of Goatfield, is found on the sea -shore, at least three miles from the nearest granite rock, and with a -bay of the sea intervening. Its dimensions are not far from those of -the _pierre de gouté_. In some former state of the granitic mountains -in that island, the declivity from the top of Goatfield may have been -very uniform, and more rapid than it is at present. - -354. Besides glaciers and torrents, which have no doubt been the -principal instruments in producing these changes, other causes -may have occasionally operated. Large stones, when once detached, -and resting on an inclined plane, from the effects of waste and -decomposition, may advance horizontally, at the same time that they -descend perpendicularly, and this will happen though they be not urged -by any torrent, or any thing but their own weight; for the surface -of the ground, as it wastes, remains higher under the stone, and for -a little way round it, than at a greater distance, on account of the -protection which it receives from the stone, as in the instances at -Saleve, just mentioned. The stone itself also becomes rounded at the -bottom; and thus the surface in contact with the ground is diminished -in extent, and the two surfaces rendered convex towards one another. It -must therefore happen, that the support, continually weakening, will at -length give way, and the stone incline or roll toward the lower side, -and may even roll considerably, if its centre of gravity has been high -above its point of support, and if its surface has had much convexity: -Thus the horizontal may very far exceed the perpendicular motion; -and, in the course of ages, the stone may travel to a great distance. -A stone, however, which travels in this manner, must diminish as it -proceeds, and must have been much greater in the beginning than it is -at present. - -355. This kind of motion may be aided by particular circumstances. -When a stone rests on an inclined plane, so as to be in a state -not very remote from equilibrium, if a part be taken away from the -upper side, the equilibrium will be lost, and the stone will thereby -be put in motion. That stones which lie on other stones, may, by -wearing, be brought very near an equilibrium, is proved by what are -called _rocking-stones_, or in Cornwall _Logan stones_, which have -sometimes been mistaken for works of art; but are certainly nothing -else than stones, which have been subjected to the universal law -of wasting and decay, in such peculiar circumstances, as nearly to -bring about an equilibrium of that stable kind, which, when slightly -disturbed, re-establishes itself.[178] The Logan stone at the Land's -End, is a mass of granite, weighing more than sixty tons, resting -on a rock of granite, of considerable height, and close on the sea -shore. The two stones touch but in a small spot, their surfaces being -considerably convex towards one another. The uppermost is so nearly -in an equilibrium, that it can be made to vibrate by the strength -of a man, though to overset it entirely would require a vast force. -This arises from the centre of gravity of the stone being somewhat -lower than the centre of curvature of that part of it on which it -has a tendency to roll; the consequence of which is, that any motion -impressed on the stone, forces its centre of gravity to rise, (though -not very considerably,) by which means it returns whenever the force -is removed, and vibrates backward and forward, till it is reduced to -rest. Were it required to remove the stone from its place, it might be -most easily done, by cutting off a part from one side, or blowing it -away by gunpowder; the stone would then lose its balance, would tumble -from its pedestal, and might roll to a considerable distance. Now, what -art is here supposed to perform, nature herself in time will probably -effect. If the waste on one side of this great mass shall exceed that -on the opposite in more than a certain proportion, and it is not likely -that that proportion will be always maintained, the equilibrium of the -Logan stone will be subverted, never to return. Thus we perceive how -motion may be produced by the combined action of the decomposition and -gravitation of large masses of rock. - -[Footnote 178: I do not presume so far as to say, that all -rocking-stones are produced by natural means: I have not sufficient -information to justify that assertion; but the great size of that -at the Land's End, its elevated position, and the approaches toward -something of the same kind which are to be seen in other parts of that -shore, prove that it is no work of art. They who ascribe it to the -Druids, do not consider the rapidity with which the Cornish granite -wastes, nor think how improbable it is, that the conditions necessary -to a rocking-stone, whether produced by nature or art, should have -remained the same for sixteen or seventeen hundred years.] - -356. Besides the gradual waste to which stones exposed to the -atmosphere are necessarily subject, those of a great size appear to be -liable to splitting, and dividing into large portions, no doubt from -their weight. This may be observed in almost all stones that happen to -be in such circumstances as we are now considering; and from this cause -the subversion of their balance may be more sudden, and of greater -amount, than could be expected from their gradual decay. - -Thus, if to the wasting of a stone at the bottom, we add the accidents -that may befal it in the wasting of its sides, we see at least the -physical possibility of detached stones being put in motion, merely -by their own weight. It is indeed remarkable, that some of the largest -of these stones rest on very narrow bases. Those at the foot of -Saleve touch the ground only in a few points: The Boulder stone of -Borrowdale is supported on a narrow ridge like the keel of a ship, and -is prevented from tumbling by a stone or two, that serve as a kind of -shores to prop it up. Very unexpected accidents sometimes happen to -disturb the rest of such fragments of rock as have once migrated from -their own place. Saussure mentions a great mass of _lapis ollaris_[179] -that lies detached on the side of a declivity in the valley of Urseren, -in the canton of Uri. The people use this stone as a quarry, and are -working it away on the upper side, in consequence of which it will -probably be soon overset, and will roll to the bottom of the valley. - -[Footnote 179: Voyages aux Alpes, tom. iv. § 1851.] - -357. In many instances it cannot be doubted, that stones of the kind -here referred to are the remains of masses or veins of whinstone or -granite, now worn away, and that they have travelled but a very short -way, or perhaps not at all, from their original place. Many of the -large blocks of whinstone which we find in this country, sometimes -single, and sometimes scattered in considerable abundance over a -particular spot, are certainly to be referred to this cause. But the -most remarkable examples of this sort are the stones found at the Cape -of Good Hope, on the hill called _Paarlberg_, which takes its name from -a chain of large round stones, like the pearls of a necklace, that -passes over the summit. Two of these, placed near the highest point, -are called the Pearl and the Diamond, and were mentioned several years -ago in the Philosophical Transactions.[180] From a more recent account, -these stones appear to be a species of granite, though the hill on -which they lie is composed of sandstone strata.[181] The Pearl is a -naked rock, that rises to the height of 400 feet above the summit of -the hill; the Diamond is higher, but its base is less, and it is more -inaccessible. - -[Footnote 180: Vol. lxviii. p. 102.] - -[Footnote 181: Barrow's Travels into Southern Africa, p. 60.] - -From the above stones forming a regular chain, as well as from the -immense size of the two largest, it is impossible to suppose that they -have been moved; and it is infinitely more probable, that they are -parts of a granite vein, which runs across the sandstone strata, and -of which some parts have resisted the action of the weather, while the -rest have yielded to it. The whole geological history of this part of -Africa seems highly interesting, since, as far as can be collected from -the accounts of the ingenious traveller just mentioned, it consists -of horizontal beds of sandstone or limestone, resting immediately on -granite, or on primary schistus. Loose blocks of granite are seen in -great abundance at the foot of the Table Mountain, and along the sea -shore. - - * * * * * - -358. The system which accounts for such phenomena as have been -considered in this and some of the preceding notes, by the operation -of a great deluge, or _debacle_, as it is called, has been already -mentioned. In Dr Hutton's theory, nothing whatever is ascribed to such -accidental and unknown causes; and, though their existence is not -absolutely denied, their effects, whatever they may have been, are -alleged to be entirely obliterated, so that they can be referred to -no other class but that of mere possibilities. A minute discussion, -however, of the question, Whether there are, on the surface of the -earth, any effects that require the interposition of an extraordinary -cause, would lead into a longer digression than is suited to this -place. I shall briefly state what appear to be the principal -objections to all such explanations of the phenomena of geology. - -359. The general structure of valleys among mountains, is highly -unfavourable to the notion that they were produced by any single great -torrent, which swept over the surface of the earth. In some instances, -valleys diverge, as it were from a centre, in all directions. In -others, they originate from a ridge, and proceed with equal depth and -extent on both sides of it, plainly indicating, that the force which -produced them was _nothing_, or evanescent at the summit of that ridge, -and increased on both sides, as the distance from the ridge increased. -The working of water collected from the rains and the snows, and -seeking its way from a higher to a lower level, is the only cause we -know of, which is subject to this law. - -360. Again, if we consider a valley as a space, which perhaps with many -windings and irregularities, has been hollowed out of the solid rock, -it is plain, that no force of water, suddenly applied, could loosen -and remove the great mass of stone which has actually disappeared. -The greatest column of water that could be brought to act against -such a mass, whatever be the velocity we ascribe to it, could not -break asunder and displace beds of rock many leagues in length, and -in continuity with the rock on either side of them. The slow working -of water, on the other hand, or the powers that we see every day in -action, are quite sufficient for this effect, if time only is allowed -them. - -361. Some valleys are so particularly constructed, as to carry with -them a still stronger refutation of the existence of a _debacle_. These -are the longitudinal valleys, which have the openings by which the -water is discharged, not at one extremity, but at the broadside Such is -that on the east side of Mont Blanc, deeply excavated on the confines -of the granite and schistus rock, and extending parallel to the beds of -the latter, from the Col de la Segne to the Col de Ferret; its opening -is nearly in the middle, from which the Dora issues, and takes its -course through a great valley, nearly at right angles to the chain of -the Alps, and to the valley just mentioned. From the structure of these -valleys, Saussure has argued very justly against Buffon's hypothesis, -concerning the formation of valleys by currents at the bottom of the -sea.[182] It affords indeed a complete refutation of that hypothesis: -and it affords one no less complete of the system which Saussure -himself seems on some occasions so much inclined to support. For if it -be said, that this valley was cut out by the current of a _debacle_, -that current must either have run in the direction of the valley of -Ferret, or in that of the Dora, which issues from it. If it had the -direction of the first, it could not cut out the second; and if it had -the direction of the second, it could not cut out the first. Besides, -the force which excavated this valley must have been _nothing_ at the -two extreme points, viz. at the Col de la Segne and the Col de Ferret, -and must have increased with the distance from each. It can have been -produced, therefore, only by the running of two streams in opposite -directions, on a surface that was but slightly uneven, these streams at -meeting taking a new direction, nearly at right angles to the former. A -clearer proof could hardly be required than is afforded in this case, -that what is now a deep valley was formerly solid rock, which the -running of the waters has gradually worn away; and that the waters, -when they began to run, were on a level as high, at least, as the tops -of those mountains by which the valley is bounded toward the lower side. - -[Footnote 182: Voyage aux Alpes, tom. ii. § 920.] - -362. Longitudinal valleys, with the water bursting out transversely -from their sides, like the preceding, are by no means confined to -mountains of the first order. We have a very good example, though -on a small scale, of a valley of this sort, within a few miles of -Edinburgh. The Pentland Hills form a double ridge, separated by a -small longitudinal valley, that runs from N. E. to S. W., the water of -which issues from an opening almost in the middle, and directed towards -the south. This, therefore, is not the work of any great torrent, which -overwhelmed the country; for no one direction, which it is possible -to assign to such a torrent, will afford an explanation, both of the -valley and its outlet.[183] - -[Footnote 183: In Scotland there is one valley, of a kind that I -believe is extremely rare in any part of the world, in accounting for -which, the hypothesis of a torrent or _debacle_ might, if any where, -be employed to advantage. This is the valley which extends across the -island, from Inverness to Fort William, or from sea to sea, being open -at both ends, and very little elevated in the middle. It is nearly -straight, and of a very uniform breadth, except that towards each end -it widens considerably. The bottom, reckoning transversely, is flat, -without any gradual slope from the sides towards the middle. From the -sides the mountains rise immediately, and form two continued ridges -of great height, like ramparts or embankments on each side of a large -fossé. A great part of the bottom of this singular valley is occupied -by lakes, namely, Loch Ness, Loch Oich, and Loch Lochy. Its length is -about sixty-two miles, and the point of partition from which the waters -run different ways, viz. north-east to the German Ocean, and south-west -to the Atlantic, is between Loch Oich and Loch Lochy; and, by the -estimation of the eye, I should hardly think that it is elevated more -than ten or fifteen feet above the surface of either lake. The country -on both sides is rugged and mountainous, and the streams which descend -from thence into the valley, either fall directly into the lakes, or -turn off almost at right angles when they enter the valley. Though -the bottom of this valley, therefore, is every where alluvial, with -the exception, perhaps, of a few rocks which appear at the surface, -it is certainly not excavated by the rivers which now flow in it. The -direction of the valley, it is to be observed, is the same with that of -the vertical strata which compose the mountain on either side. - -Here, then, we have a valley, not cut out by the working of any streams -which now appear; and we may therefore make trial of the hypothesis -of a _debacle_. This, however, will afford us no assistance; because, -if we suppose what is now hollow to have been once occupied by the -same kind of rock which is on either side, no force of torrents can -have suddenly loosened and removed from its place a body of such vast -magnitude. A greater column of water, than one having for its base a -transverse section of the valley, could not act against it, and this -would have to overcome the cohesion and inertia of a column of rock -of the same section, and of the length of sixty-two miles. It is not -hazarding much to affirm, that no velocity which could be communicated -to water, not even that which it could acquire by falling from an -infinite height, could give to it a force in any degree adequate to -this great effect. - -The explanation of this valley, which appears to me the most probable, -is the following. It will be shown hereafter, that there is good reason -to suppose, that, in most parts of our island, the relative level of -the sea and land has been in past ages considerably higher than it is -at present. In such circumstances, this valley may have been under -the surface of the sea, the highest part of it being scarcely 100 -feet above that level at present. It may have been a kind of sound, -therefore, or strait, which connected the German Sea with the Atlantic; -and the strong currents, which, on account of the different times -of high water in these two seas, must have run alternately up and -down this strait, may have produced that flatness of the bottom, and -straightness of the sides, and that widening at the extremities, which -are mentioned above. In this way, too, some difficulties are removed -relative to Loch Ness, which is so deep as hardly to be consistent with -the indefinite length of the period of waste that must be ascribed to -the mountains on each side of it. Its depth is said, where greatest, -not to be less than 180 fathoms. According to this hypothesis, it may, -at no very distant period, have been a part of the bottom of the sea.] - -363. They who maintain the existence of the _debacle_, will no doubt -allege, that though these valleys were not cut out by means of it, yet -others may. But it must be recollected, that if some of the greatest -and deepest valleys on the face of the earth, such as that just -mentioned, on the east side of Mont Blanc, are thus shown to be the -work of the daily wasting of the surface, what other inequalities can -be great enough to require the interposition of a more powerful cause? -If a _dignus vindice nodus_ does not exist here, in what part of the -natural history of the earth is it likely to be found? - -364. The large masses of rock so often met with at a distance from -their original place, are one of the arguments used for the _debacle_. -It has, however, been shown, that, supposing a form of the earth's -surface considerably different from the present, especially, supposing -the absence of the valleys which the rivers have gradually cut out, the -transportation of such stones is not impossible, even by such powers -as nature employs at present. Now, without the supposition that the -surface was more continuous, and that its present inequalities did not -exist, no force of torrents, whatever their velocity and magnitude may -have been, could have produced this transportation. No force of water -could raise a stone like the _pierre de goutté_ from the bottom of -a valley, to the top of a steep hail. Indeed, if we suppose a great -fragment of rock to be hurried along on a horizontal or an inclined -plane, by the force of water, the moment it comes to a deep valley, and -has to rise up over an ascent of a certain steepness, it will remain -at rest; the water itself will lose its velocity, and the heavy bodies -which it carried with it will proceed no farther. Thus, therefore, we -have the following dilemma. If the surface is not supposed to have -had a certain degree of uniformity in past times, a _debacle_ is -insufficient for the transportation of stones: If it is supposed to -have had that uniformity, a _debacle_ is unnecessary. - -365. Another fact, which has been supposed favourable to the opinion -of the action of great torrents at some former period, is, that in -countries like that round Edinburgh, where whinstone hills rise up from -among secondary strata, a remarkable uniformity is observed in the -direction of their abrupt faces. Thus, in the country just mentioned, -the steep faces generally front the west, whiles in the opposite -direction, the slope is gentle, and the hills decline gradually into -the plain. Hence it is supposed, that a torrent, sweeping from west to -east, has carried off the strata from the west side of these hills, -but, being obstructed by the whinstone rock, has left the strata on -the east side in their natural place. - -But, besides that no force which can ever be ascribed to a torrent -could have removed at once bodies of strata 300 or 400 feet, nay even -800 or 1000 in thickness, which must have been the case if this were -the true explanation of the fact, there is a circumstance which may -perhaps enable us to explain these phenomena without the assistance of -any extraordinary cause. The secondary strata in which the whinstone -hills are found in this part of Scotland, are not horizontal, but -rise or _head_ towards the west, dipping towards the east. The side, -therefore, of the whinstone hills which is precipitous, is the same -with that towards which the strata rise. Now, from the manner in which -these hills are supposed to have been elevated, the strata are likely -to have been most broken and shattered towards that side, while, on the -opposite, they had the support of the whinstone rock. They would become -a prey, therefore, more easily to the common causes of erosion and -waste on the upper side than on the lower. The streams that flowed from -the higher grounds would wear them on the former most readily; and the -action of these streams would be resisted by the superior hardness of -the whinstone, just as the great torrent of the _debacle_ is supposed -to have been. - -It should also be observed, that this fact of the uniform direction of -the abrupt faces of mountains, is often too hastily generalized. In -primitive countries, it is no farther observed than by the steep faces -of the mountains being most frequently turned toward the central chain. -In Scotland, as soon as you leave the flat country, and enter the -Highlands, the scarps of the hills face indiscriminately all the points -of the compass, and are directed as often to the east as to the west. - -366. Where the strata are nearly horizontal, they afford the most -distinct information concerning the direction and progress of the -wasting of the land. The inclined position of the strata, which in all -other cases must enter for so much into our estimate of the causes -which have produced the present inequality of the earth's surface, -disappears there entirely; and the whole of that inequality is to be -ascribed to the operations at the surface, whether they have been -sudden or gradual. A very important fact from a country of this -sort, is related by BARROW, in his Travels into Southern Africa. The -mountains about the Cape of Good Hope, and as far to the north as that -ingenious traveller prosecuted his journey, are chiefly of horizontal -strata of sandstone and limestone, exhibiting the appearance, on their -abrupt sides, of regular layers of masonry, of towers, fortifications, -&c. Now, among all these mountains, he observed, that the high or -steep sides look constantly down the rivers, while the sloping or -inclined sides have just the opposite direction. When, in travelling -northward, he passed the line of partition, where the waters from -running south take their direction to the north, he found, that the -gradual slope, which had hitherto been turned to the north, was now -turned to the south: The abrupt aspect of the mountains, in like -manner, from facing the south, was directed to the north; so that, -in both cases, the hills turned their backs on the line of greatest -elevation.[184] - -[Footnote 184: Barrow's Travels into Southern Africa, p. 245.] - -It is evident, therefore, that the form of this land has been -determined by the slow working of the streams. The causes which -produced the effects here described, began their action from the line -of greatest elevation, and extended it from thence on both sides, in -opposite directions. This is the most precise character that can mark -the alluvial operations, and distinguish them from the overwhelming -power of a great _debacle_. - -367. Lastly, if there were any where a hill, or any large mass composed -of broken and shapeless stones, thrown together like rubbish, and -neither worked into gravel nor disposed with any regularity, we must -ascribe it to some other cause than the ordinary _detritus_ and -wasting of the land. This, however, has never yet occurred; and it -seems best to wait till the phenomenon is observed, before we seek for -the explanation of it. - -368. These arguments appear to me conclusive against the necessity of -supposing the action of sudden and irregular causes on the surface of -the earth. In this, however, I am perhaps deceived: neither Pallas, -nor Saussure, nor Dolomieu, nor any other author who has espoused -the hypothesis of such causes, has explained his notions with any -precision; on the contrary, they have all spoken with such reserve and -mystery, as seemed to betray the weakness, but may have concealed the -strength of their cause. I have therefore been combating an enemy, that -was in some respects unknown; and I may have supposed him dislodged, -only because I could not penetrate to his strongholds. The question, -however, is likely soon to assume a more determinate form. A zealous -friend of Dr Hutton's theory, has lately[185] declared his approbation -of the hypothesis which has here been represented as so adverse to that -theory; and, from his ability and vigour of research, it is likely to -receive every improvement of which it is susceptible. - -[Footnote 185: Trans. Royal Society Edin. vol. v. p 68.] - - - - - NOTE XIX. § 117. - - _Transportation of Materials by the Sea._ - - -369. THE existence of the great and extensive operations, by which the -spoils of the land are carried all over the ocean, and spread out on -the bottom of it, may be supposed to require some further elucidation. -We must attend, therefore, to the following circumstances. - -When the detritus of the land is delivered by the rivers into the sea, -the heaviest parts are deposited first, and the lighter are carried -to a greater distance from the shore. The accumulation of matter -which would be made in this manner on the coast, is prevented by the -farther operation of the tides and currents, in consequence of which -the substances deposited continue to be worn away, and are gradually -removed farther from the land. The reality of this operation is -certain; for otherwise we should have on the sea shore a constant and -unlimited accumulation of sand and gravel, which, being perpetually -brought down from the land, would continually increase on the shore, if -nature did not employ some machinery for removing the advanced part -into the sea, in proportion to the supply from behind. - -The constant agitation of the waters, and the declivity of the -bottom, are no doubt the causes of this gradual and widely extended -deposition. A soft mass of alluvial deposit, having its pores filled -with water, and being subject to the vibrations of a superincumbent -fluid, will yield to the pressure of that fluid on the side of the -least resistance, that is, on the side toward the sea, and thus will -be gradually extended more and more over the bottom. This will happen -not only to the finer parts of the detritus, but even to the grosser, -such as sand and gravel. For suppose that a body of gravel rests on -a plane somewhat inclined, at the same time that it is covered with -water to a considerable depth, that water being subject not only to -moderate reciprocations, but also to such violent agitation as we see -occasionally communicated to the waters of the ocean; the gravel, -being rendered lighter by its immersion in the water, and on that -account more moveable, will, when the undulations are considerable, -be alternately heaved up and let down again. Now, at each time that -it is heaved up, however small the space may be, it must be somewhat -accelerated in its descent, and will hardly settle on the same point -where it rested before. Thus it will gain a little ground at each -undulation, and will slowly make its way towards the depths of the -ocean, or to the lowest situation it can reach. This, as far as we may -presume to follow a progress which is not the subject of immediate -observation, is one of the great means by which loose materials of -every kind are transported to a great distance, and spread out in beds -at the bottom of the ocean. - -370. The lighter parts are more easily carried to great distances, -being actually suspended in the water, by which they are very gradually -and slowly deposited. A remarkable proof of this is furnished from an -observation made by Lord Mulgrave, in his voyage to the North Pole. -In the latitude of 65° nearly, and about 250 miles distant from the -nearest land, which was the coast of Norway, he sounded with a line of -688 fathoms, or 4098 feet; and the lead, when it struck the ground, -sunk in a soft blue clay to the depth of ten feet.[186] The tenuity -and fineness of the mud, which allowed the lead to sink so deep into -it, must have resulted from a deposition of the lighter kinds of -earth, which being suspended in the water, had been carried to a great -distance, and were now without doubt forming a regular stratum at the -bottom of the sea. - -[Footnote 186: Phipps's Voyage, p. 74, 141.] - -371. The quantity of detritus brought down by the rivers, and -distributed in this manner over the bottom of the sea, is so great, -that several narrow seas have been thereby rendered sensibly shallower. -The Baltic has been computed to decrease in depth at the rate of -forty inches in a hundred years. The Yellow Sea, which is a large -gulf contained between the coast of China and the peninsula of Corea, -receives so much mud from the great rivers that run into it, that it -takes its colour, as well as its name, from that circumstance; and the -European mariners who have lately navigated it, observed, that the -mud was drawn up by the ships, so as to be visible in their wake to a -considerable distance.[187] Computations have been made of the time -that it will require to fill up this gulf, and to withdraw it entirely -from the dominion of the ocean: but the data are not sufficiently exact -to afford any precise result, and are no doubt particularly defective -from this cause, that much of the earth carried into the gulf by the -rivers, must be carried out of it by the currents and tides, and -the finer parts wafted probably to great distances in the Pacific -Ocean.[188] The mere attempt, however, towards such a computation, -shows how evident the progress of filling up is to every attentive -observer; and, though it may not ascertain the measure, it sufficiently -declares the reality of the operations, by which the waste of the -present continents is made subservient to the formation of new land. - -[Footnote 187: Staunton's Account of the Embassy to China, vol. i. p. -448.] - -[Footnote 188: Perouse, in sailing along the coast of China, from -Formosa to the strait between Corea and Japan, though generally -fifty or sixty leagues from the land, had soundings at the depth of -forty-five fathoms, and sometimes at that of twenty-two. Atlas du -Voyage de la Perouse, No. 43.] - -372. Sandbanks, such as abound in the German Ocean, to whatever they -owe their origin, are certainly modified, and their form determined, -by the tides and currents. Without the operation of these last, banks -of loose sand and mud could hardly preserve their form, and remain -intersected by many narrow channels. The formation of the banks on the -coast of Holland, and even of the Dogger Bank itself, has been ascribed -to the meeting of tides, by which a state of tranquillity is produced -in the waters, and of consequence a more copious deposition of their -mud. Even the great bank of Newfoundland seems to be determined in its -extent by the action of the Gulf stream. In the North Sea, the current -which sets out of the Baltic, has evidently determined the shape of -the sandbanks opposite to the coast of Norway, and produced a circular -sweep in them, of which it is impossible to mistake the cause. - -In proof of the action here ascribed to the waters of the sea, in -transporting materials to an unlimited extent, we may add the well -known observation, that the stones brought up by the lead from the -bottom of the sea, are generally round and polished, hardly ever sharp -and angular. This could never happen to stones that were not subject to -perpetual attrition. - -373. Currents are no doubt the great agents in diffusing the detritus -of the land over the bottom of the sea. These have been long known to -exist; but it is only since the later improvements in navigation, that -they have been understood to constitute a system of great permanence, -regularity, and extent, connected with the trade winds, and other -circumstances in the natural history of the globe. The Gulf stream was -many years since observed to transport the water, and the temperature -of the tropical regions into the climates of the north; and we are -indebted to the researches of Major RENNELL, for the knowledge of a -great system of currents, of which it is only a part. That geographer, -who is so eminent for enriching the details of his science with the -most interesting facts in history or in physics, has shown, that -along the eastern coast of Africa, from about the mouth of the Red -Sea, a current fifty leagues in breadth sets continually towards the -south-west.[189] It doubles the Cape of Good Hope, runs from thence -north-west, preserving on the whole the direction of the coast, but -reaching so far into the ocean, that, about the parallel of St Helena, -its breadth exceeds 1000 miles. From thence, as it approaches the line, -its direction is more nearly east; and meeting in the parallel of 3° -north, with a current which has come along the western coast of Africa -from the north, the two united stretch across the Atlantic, in a line -somewhat south of west, and in a very wide and rapid stream. This -stream meets the American land at Cape St Roque, where it is joined -by another coming up along the eastern shore of that continent, and -directed towards the north. They proceed northward together till they -enter the Gulf of Florida, from which being as it were reflected, they -form the Gulf stream, passing along the coast of North America, and -stretching across the Atlantic to the British Isles. From thence the -current turns to the south, and, proceeding down the coast of Spain -and Africa, meets the stream ascending from the south, as already -described, and thus continues in perpetual circulation. The velocity of -these currents is not less remarkable than their extent. At the Cape -of Good Hope, the rate is thirty nautical miles in twenty four hours; -in some places forty five; and under the line seventy seven. When the -Gulf stream issues from the Straits of Bahama, it runs at the rate of -four miles an hour, and proceeds to the distance of 1800 miles, before -its velocity is reduced to half that quantity. In the parallel of 38°, -near 1000 miles from the above strait, the water of the stream has been -found ten degrees warmer than the air. - -[Footnote 189: Geography of Herodotus, p. 672.] - -374. The course of the Gulf stream is so fixed and regular, that -nuts and plants from the West Indies are annually thrown ashore on -the Western Islands of Scotland. The mast of a man of war, burnt at -Jamaica, was driven several months afterwards on the Hebrides,[190] -after performing a voyage of more than 4000 miles, under the direction -of a current, which, in the midst of the ocean, maintains its course as -steadily as a river does upon the land. - -[Footnote 190: Pennant's Arctic Zoology, Introd. p. 70.] - -The great system of currents thus traced through the Atlantic, has no -doubt phenomena corresponding to it in the Indian and Pacific Oceans, -which the industry of future navigators may discover. The whole appears -to be connected with the trade winds, the figure of our continents, the -temperature of the seas themselves, and perhaps with some inequalities -in the structure of the globe. The disturbance produced by these causes -in the equilibrium of the sea, probably reaches to the very bottom of -it, and gives rise to those counter currents, which have sometimes been -discovered at great depths under the surface.[191] - -[Footnote 191: Histoire Naturelle de Buffon, Supplément, tom. ix. p. -479. 8vo.] - -The great transportation of materials that must result from the -action of these combined currents is obvious, and serves not a little -to diminish our wonder, at finding the productions of one climate -so frequently included among the fossils of another. Amid all the -revolutions of the globe, the economy of nature has been uniform, in -this respect, as well as in so many others, and her laws are the only -thing that have resisted the general movement. The rivers and the -rocks, the seas and the continents, have been changed in all their -parts; but the laws which direct those changes, and the rules to which -they are subject, have remained invariably the same. - -375. Objections have been made to that translation of materials by the -waters of the ocean which is supposed in this theory, particularly -by Mr Kirwan, in his Geological Essays; and, though I might perhaps -content myself with the remark already made, that the Neptunian system -involves suppositions concerning the transportation of solid bodies by -the sea, in the early ages of the world, as wonderful as those which, -according to our theory, are common to all ages, I am unwilling to -remain satisfied with a mere _argumentum ad hominem_, where the fallacy -of the reasoning is so easily detected. - -376. One of Mr Kirwan's objections to the deposition of materials at -the bottom of the sea, is thus stated: "FRISI has remarked, in his -mathematical discourses, that if any considerable mass of matter were -accumulated in the interior of the ocean, the diurnal motion of the -globe would be disturbed, and consequently it would be perceptible; -a phenomenon, however, of which no history or tradition gives any -account."[192] - -[Footnote 192: Geol. Essays, p. 441.] - -The appeal made here to Frisi is singularly unfortunate, as that -philosopher has demonstrated the very contrary of Mr Kirwan's -position, and has proved, that the disturbance given to the diurnal -motion by the causes here referred to may be real, but cannot be -perceptible. Having investigated a formula expressing the law which -all such disturbances must necessarily observe, he concludes, "Hàc -autem formulâ manifestum fiet, ex iis omnibus variationibus quæ in -terrestri superficie observari solent, montium et collium abrasione, -dilapsu corporum ponderosiorum in inferiores telluris sinus, nullam -oriri posse variationem _sensibilem_ diurni motûs. Nam si statuamus -data aliqua annorum periodo terrestrem superficiem ad duos usque pedes -abradi undique, eam vero materiæ quantitatem ad profunditatem pedum -1000 dilabi; erit omne quod inde orietur incrementum velocitatis diurni -motûs 30000/(19638051)^2 = 1/12855068184."[193] - -[Footnote 193: Frisii Opera, tom. iii. p. 269.] - -Here, it is evident, that Frisi admits those very changes on the -surface which we are contending for, and shows, that their tendency is -to accelerate the earth's diurnal motion, but, by a quantity so small, -that, in a space of time amounting at least to 200 years, the increase -of the diurnal motion would only be such a part of the whole as the -preceding fraction is of unity.[194] - -[Footnote 194: The time requisite for taking away by waste and erosion -two feet from the surface of all our continents, and depositing it at -the bottom of the sea, cannot be reckoned less than 200 years. The -fraction 1/12855068184, reduced to parts of a day, is 1/148554 of a -second; so that it would require 200 years to shorten the length of -the day, by the above fraction of a second; and therefore it would -require 148554 times 200 years, or 29710800 years, to diminish it an -entire second. The accumulated effect, however, of all the diminutions -during that period, would amount to much more: and if we had any -perfectly uniform standard to compare the motion of the earth with, -its difference from that standard would increase as the squares of the -time, and the total acceleration would amount to one second in 77080 -years. Whatever relation this bears to the age of the globe itself, it -exceeds more than ten times the age of any historical record. - -Though Frisius concludes, as is stated here, that the acceleration -produced in the diurnal motion of the earth, is far too inconsiderable -to become the object of astronomical observation, he makes a -supposition difficult to be reconciled with this conclusion, namely, -that the acceleration has had a sensible effect on the figure of the -earth, or rather of the sea, having increased the centrifugal force, -and thereby accumulated the waters under the equator, in the present, -more than in former ages. Such an accumulation, he thinks agreeable -to certain appearances that have been observed respecting the ancient -level of the sea. These appearances will be afterwards considered: it -is sufficient to remark here, that though the fraction, expressing the -increment of the centrifugal force, must be double that which expresses -the acceleration, it must be too small to have any perceptible effect -in elevating the sea, except after an immense interval of time; and the -compensations which arise from other causes, probably must prevent it -from becoming sensible in any length of time whatsoever.] - -377. The instance just given may serve as one of many, to shew what -confidence is to be placed in that indigested mass of facts and -quotations which Mr Kirwan, without discrimination, and without -discussion, has brought together from all quarters. He has no -intention, I believe, to deceive his readers; but we may judge, from -this specimen, of the precautions he has taken against being deceived -himself. - -In some respects, the result of Frisi's investigation must be -considered as imperfect. If there were no relative motion in the parts -of our globe, but that by which things descend from a higher to a lower -level, a continual acceleration of its rotation, though extremely slow, -would take place, as above computed. But as, in the interior of the -earth, there are undoubtedly motions of a tendency opposite to those on -the surface, and directed from the centre towards the circumference, -they must produce a retardation in the diurnal revolution; and from -this must arise an inequality, not uniformly progressive in the same -direction, but periodical, and confined within certain limits, as the -causes are by which it is produced.[195] - -[Footnote 195: Even in the descent of bodies from a higher to a lower -level at the surface of the earth, the whole tendency is not to -increase the velocity of the earth's rotation, and many compensations -take place, which, when the matter is considered only in general, -are necessarily overlooked. This will appear evident, if we reflect, -that it is not simply the approach of a body towards the centre of -the earth, or its removal from that centre, which tends to disturb -the rotation of the earth; but its approach to the axis of the earth, -or its removal from that axis. The velocity with which a particle of -matter revolves, whether on the surface, or in the interior of the -globe, is proportional to its distance from the axis of rotation; -and therefore, when a body comes nearer to the axis, it loses a part -of the motion which it had before; which part, of consequence, is -communicated to the whole mass of the earth, and therefore tends to -increase the velocity with which it revolves. The contrary happens when -a body recedes from the axis; for it then receives an addition to its -velocity, which, of course, is taken away from the rotatory motion of -the earth. - -Hence, bodies moving in a horizontal plane, may increase or diminish -the swiftness of the diurnal motion, according as they move towards the -poles or towards the equator; and those which descend from a higher to -a lower level, disturb the earth's rotation, much more in consequence -of their horizontal, than of their perpendicular motion. The Ganges, -for instance, though its source is probably elevated no less than -7000 feet above the level of the sea, tends to retard the earth's -rotation, by bringing its waters, and the mud contained in them, from -the parallel of 31° to that of 22°, and so increasing their distance -from the earth's axis by more than 1/12 th part. Had the Ganges flowed -towards the north, as the Nile does, its effect would have been just -the contrary. - -In the same manner, a stone descending from the top of a mountain, may -accelerate or retard the earth's rotation, according to the direction -in which it descends. If it descend on the side of the elevated pole, -it will then produce acceleration, because its distance from the axis -will be diminished; but if it descend on the side of the depressed -pole, and if the direction in which it is moved, be over a line less -inclined, than a line drawn from the same point to the depressed pole, -it will then produce a retardation, because its distance from the axis -will be increased. - -Let us suppose, for example, that the top of Mount Blanc is in latitude -45° 49′, and that its height is 2450 toises above the level of the sea. -The point at which a line drawn from the top of this mountain, parallel -to the earth's axis, will meet the superficies of the sea, (supposing -that superficies continued inland from the Mediterranean), must be -about 2382 toises in horizontal distance, or about 2-1/2 minutes south -of the summit, that is, in the parallel of 45° 46-1/2′; and if this -parallel be continued all round the globe, the points of the earth's -surface between it and the equator, are all more distant from the -earth's axis than the top of Mount Blanc is; whereas all the points -to the north of it are nearer to that axis. A stone, therefore, from -the top of Mount Blanc, if carried any where to the south of the above -parallel, will retard the earth's diurnal motion; but if carried any -where to the north of the same line, will accelerate that motion. - -The same quantity of matter, however, carried an equal distance -toward the pole, and toward the equator, from any point, will lose -more velocity in the former case than it will gain in the latter, as -easily follows from the nature of circle. Therefore, supposing an equal -dispersion of the detritus of a mountain in all directions, the parts -that go toward the pole will most disturb the diurnal motion; and hence -a balance on their side, or in favour of acceleration, as already -observed.] - -378. Mr Kirwan's second objection is founded on the misapprehension -of a well-known fact in the natural history of the earth. "Rivers," -says this author, "do not carry into the sea the spoils which they -bring from the land, but employ them in the formation of deltas of low -alluvial land at their mouths, according to what Major Rennell has -proved." The fact of the formation of _deltas_ from the spoils which -the rivers carry from the higher grounds, is perfectly ascertained; -and the detail into which Major Rennell has entered in the passage -referred to by Mr Kirwan, does credit to the acuteness and accuracy -of that excellent geographer. But it is not there asserted, that -rivers employ _all_ the materials which they carry with them, in the -formation of those deltas, and deliver none of them into the sea. On -the contrary, they carry from the _delta_ itself mud and earth, which -they can deposit no where but in the sea; and it is this circumstance -chiefly that limits the increase of those alluvial lands, and makes -them either cease to increase, or makes them increase very slowly after -a certain period, though the supply of earth from the higher grounds -remains nearly the same. To make Mr Kirwan's argument conclusive, it -would be necessary to prove, that _all_ the mud carried down by the -Nile or the Ganges, was deposited on the low lands before these rivers -enter the sea; a thing so obviously absurd, that nothing but his haste -to obtain a conclusion unfavourable to the Plutonic system, could have -prevented him from perceiving it[196]. - -[Footnote 196: The instance mentioned in the Geological Essays, from -the travels of the Abbé Fortis, concerning urns thrown into the -Adriatic, upwards of 1400 years ago, and not yet covered with mud, -must be explained from peculiar circumstances, or local causes, with -which we are unacquainted, as it makes against the deposition of earth -near the shore, and in narrow seas; a general fact which, I think, -every body admits.] - -379. A remark which Major Rennell has made concerning the mouths of -rivers, in his Geography of Herodotus, deserves Mr Kirwan's attention, -though perhaps he may not be able to put on it an interpretation quite -so favourable to his system. The remark is, that the mouths of great -rivers are often formed on principles quite opposite to one another, so -that some of them have a real delta or triangle of flat land at their -mouths, while others have an estuary, or what may not improperly be -called a _negative_ delta. Of the latter kind are some of the greatest -rivers in the world, the Plata, the Oroonoko and the Maranon, and by -far the greatest number of our European rivers. Nobody can doubt, that -the three rivers just named carry with them as much earth as the Nile, -or the Euphrates, or any other river in the world. All this they have -deposited in the sea, and committed to the currents, which sweep along -the shore of the American continent, and by these they have been spread -out over the unlimited tracts of the ocean. - -Indeed, nothing can be more just than Dr Hutton's observation, that -where low land is formed at the mouths of rivers, there the rivers -bring down more than the sea is able to carry away; but that where -such land is not formed, it is because the sea is able to carry off -immediately all the deposit which it receives. - -380. Mr Kirwan has denied on another principle the power of the sea to -carry to a distance the materials delivered into it: "Notwithstanding," -says he, "many particles of earth are by rivers conduced to the sea, -yet _none are conveyed in any distance_, but are either deposited at -their mouths, or rejected by currents or by tides; and the reason -is, because the tide of flood is always more impetuous and forcible -than the tide of ebb, the advancing waves being pressed forward by -the countless number behind them, whereas the retreating are pressed -backward by a far smaller number, as must be evident to an attentive -spectator; and hence it is that all floating things cast into the sea, -are at last thrown on shore, and not conveyed into the mid regions of -the sea, as they should be if the reciprocal undulations of the tides -were equally powerful "[197] - -[Footnote 197: Kirwan's Geol. Essays, p. 439.] - -381. But if the _attentive spectator_, instead of trusting to a vague -impression, or listening to some crude theory of undulations, reflects -on one of the most simple facts respecting the ebbing and flowing of -the tides, he will be very little disposed to acquiesce in the above -conclusion. He has only to consider, that the flowing of the tide -requires just six hours, and the ebbing of it likewise six hours; so -that the same body of water flows in upon the shore, and retreats from -it, in the same time. The quantity of matter moved, therefore, and the -velocity with which it is moved, are in both cases the same; and it -remains for Mr Kirwan to show in what the difference of their force can -possibly consist. - -The force with which the waves usually break upon our shores, does not -arise from the velocity of the tide being greater in one direction -than in another. In the main ocean, the waves have no progressive -motion, and the columns of water alternately rise and fall, without -any other than a reciprocating motion: a kind of equilibrium takes -place among the undulations, and each wave being equally acted upon by -those on opposite sides, remains fixed in its place. Near the shore -this cannot happen; the water on the land side from its shallowness -being incapable of rising to the height necessary to balance the -great undulations which are without. The water runs, therefore, as it -were, from a higher to a lower level, spreading itself towards the -land side. This produces the breakers on our shores, and the surf -of the tropical seas. A rock or a sandbank coming within a certain -distance of the surface, is sufficient, in any part of the ocean, to -obstruct the natural succession of undulations; and, by destroying the -mutual reaction of the waves, to give them a progressive instead of a -reciprocating motion. - -382. It is, however, but from a small distance, that the waves are -impelled against the shore with a progressive motion. The border of -breakers that surrounds any coast is narrow, compared with the distance -to which the _detritus_ from the land is confessedly carried; the -water, while it advances at the surface, flows back at the bottom; -and these contrary motions are so nearly equal, that it is but a very -momentary accumulation of the water that is ever produced on any shore. - -If it were otherwise, and if it were true that the sea throws out every -thing, and carries away nothing, we should have a constant accumulation -of earth and sand along all shores whatsoever, at least wherever a -stream ran into the sea. This, as is abundantly evident, is quite -contrary to the fact. - -So, also, the bars formed at the mouths of rivers, after having -attained a certain magnitude, increase no farther, not because they -cease to receive augmentations from the land, but because their -diminution from the sea, increasing with their magnitude, becomes at -length so great, as completely to balance those augmentations. When -properly examined, therefore, the phenomena, which have been proposed -as most inconsistent with the indefinite transportation of stony -bodies, afford very satisfactory proofs of that operation. - -383. It is true, that bodies which float in the water, when carried -along on the tops of the waves towards a shelving beach, having -acquired a certain velocity, are thrown farther in upon the land than -the distance they would have floated to, if they had been simply -sustained by the water. The depth of water, therefore, at the place -where they take the ground, is not likely to be such as to float them -again, and to carry them out towards the sea. They are, therefore, left -behind; and this produces an appearance of a force impelling floating -bodies towards the land, much greater and more general than really -takes place. - -These observations may serve to show, how unsound the principles are -from which Mr Kirwan's conclusions are deduced: they are perhaps more -than is necessary for that purpose: it might have been sufficient to -observe, that the increase of land on the sea shore is limited, though -the augmentation from the land is certainly indefinite, a proof that -the diminution from the sea is constant and equal to the increase. - -384. "Mariners," says Mr Kirwan, "were accustomed, for some centuries -back, to discover their situation, by the kind of earth or sand brought -up by their sounding plummets; a method which would prove fallacious, -if the surface of the bottom did not continue invariably the same."[198] - -[Footnote 198: Geol. Essays, p. 440.] - -The fact here stated, that mariners, when navigation was more imperfect -than it is now, had very frequent recourse to this method, and that -they still use it occasionally, is very true. But from this, the only -inference that can be fairly deduced is, that the changes at the bottom -of the sea are very slow, and the variation but little; not merely -from one year to another, but even from one century to another. The -rules by which the mariner judged of his position from the quality of -the earth which the lead brought up, and which were deduced no doubt -from observations made at no very great distance of time, might be -sufficient for his purpose, though a slow change had been all the while -going forward. Such observations could at best have little accuracy, -and could not be affected by small variations. It is the slowness of -the change, that makes the experience of one age applicable, in this, -as in innumerable other instances, to the observations of the next. If -a long interval is taken, we will look in vain for the same uniformity -of results. A pilot, who would at present judge of his position in the -German Ocean, by comparing his soundings with those taken by PYTHEAS, -(supposing them known) in his navigation of that sea, more than 2000 -years ago, could hardly be expected to determine his latitude and -longitude with great exactness; and I know not if the most zealous -advocate for the immutability of the earth's surface, would be willing -to trust his safety in a ship that was guided by such antiquated rules. - - - - - NOTE XX. § 118. - - _Inequalities in the Planetary Motions._ - - -385. The assertion that, in the planetary motions, we discover no -mark, either of the commencement or termination of the present order, -refers to the late discoveries of LA GRANGE and LA PLACE, which have -contributed so much to the perfection of physical astronomy. From -the principle of universal gravitation, these mathematicians have -demonstrated, that all the variations in our system are periodical; -that they are confined within certain limits; and consist of alternate -diminution and increase. The orbits of the planets change not only -their position, but even their magnitude and their form: the longer -axis of each has a slow angular motion; and, though its length remains -fixed, the shorter axis increases and diminishes, so that the form of -the orbit approaches to that of a circle, and recedes from it by turns. -In the same manner, the obliquity of the ecliptic, and the inclination -of the planetary orbits, are subject to change; but the changes are -small, and, being first in one direction, and then in the opposite, -they can never accumulate so as to produce a permanent or a progressive -alteration. Thus, in the celestial motions, no room is left for the -introduction of disorder; no irregularity or disturbance, arising from -the mutual action of the planets, is permitted to increase beyond -certain limits, but each of them, in time, affords a correction for -itself. The general order is constant, in the midst of the variation of -the parts; and, in the language of La Place, there is a certain mean -condition, about which our system perpetually _oscillates_ performing -small vibrations on each side of it, and never receding from it -far.[199] The system is thus endowed with a stability, which can refill -the lapse of unlimited duration; it can only perish by an external -cause, and by the introduction of laws, of which at present no vestige -is to be traced. - -[Footnote 199: Exposition du Systéme du Monde, par La Place, Livre iv. -chap. 6. p. 199. 2d edit.] - -386. The same _calculus_ to which we are indebted for these sublime -conclusions, informs us of two circumstances, which mark the law -here treated of as an effect of wise design, to the entire exclusion -both of necessity and chance. One of these circumstances consists in -the planetary motions being all in the same direction, or all _in -consequentia_ as it is called by the astronomers. This is essential -to the compensation and stability above mentioned:[200] had one planet -circulated round the sun in a direction from east to west, and another -in a direction from west to east, the disturbances they would have -produced on one another's motion would not necessarily have been -periodical; their irregularities might have continually increased, and -they might have deviated in the course of ages from their original -condition, beyond any limits that can be assigned. - -[Footnote 200: La Place, _ibid._] - -The other circumstance, on which the stability of our system depends, -is the small eccentricity of the planetary orbits, or their near -approach to circles. Were their orbits very eccentric, an opening -would be given to progressive change, that might so far increase, as -to prove the destruction of the whole. But neither the movement of all -the planets in the same direction, nor the small eccentricity of their -orbits, can be ascribed to accident, since that either of these should -happen by chance, in as many instances as there are planets, both -primary and secondary, is almost infinitely improbable. Again, that any -necessity in the nature of things should have either determined the -_direction_ of the planetary motions, or proportioned the _quantity_ -of them to the intensity of the central force, cannot be admitted, as -these are things unavoidably conceived to be quite independent of one -another. It remains, therefore, that we consider the laws, which make -the disturbances in our system correct themselves, and by that means -give firmness and permanence to it, as a proof of the consummate wisdom -with which the whole is constructed. - -387. The geological system of Dr Hutton, resembles, in many respects, -that which appears to preside over the heavenly motions. In both, we -perceive continual vicissitude and change, but confined within certain -limits, and never from a certain, mean condition, which is such, that, -in the lapse of time, the deviations from it on the one side, must -become just equal to the deviations from it on the other. In both, a -provision is made for duration of unlimited extent, and the lapse of -time has no effect to wear out or destroy a machine, constructed with -so much wisdom. Where the movements are all so perfect, their beginning -and end must be alike invisible. - - - - - NOTE XXI. § 122. - - _Changes in the apparent - Level of the Sea._ - - -388. In speaking of the natural epochs marked out by the phenomena -of the mineral kingdom, we have supposed a greater simplicity, and -separation of effects from one another, than probably takes place in -nature. We have, for instance, abstracted, in speaking of the waste -and degradation of the land, from that elevation which may have been -carried on at the same time. This appeared necessary to be done, in -order to simplify as much as possible the view that was to be given of -the whole; but there can be no doubt, that, while the land has been -gradually worn down by the operations on its surface, it has been -raised up by the expansive forces acting from below. There is even -reason to think, that the elevation has not been uniform, but has been -subject to a kind of oscillation, insomuch, that the continents have -both ascended and descended, or have had their level alternately raised -and depressed, independently of all action at the surface, and this -within a period comparatively of no great extent. - -It will be easily understood, that the facts we are going to state, -each taken singly, prove nothing more than a change of the line in -which the surface of the sea intersects the surface of the land, -leaving it uncertain to which of the two the change ought really to be -ascribed. Taken in combination, however, these facts may determine what -each of them separately cannot ascertain. I shall first, therefore, -mention some of the principal observations relative to the change above -mentioned, and shall then compare them, in order to discover whether it -is most probable that this change has been produced by the motion of -the land or of the sea. - -389. If we begin with examining the coasts of our own island, we shall -find clear evidence every where, that the sea once reached higher up -upon the land than it does at present. The marks of an ancient sea -beach are to be seen beyond the present limits of the tide, and beds -of sea shells, not mineralized, are found in the loose earth or soil, -sometimes as high as thirty feet above the present level of the sea. -Some of these on the shores of the Frith of Forth are very well known, -and have been often mentioned. Indeed, on the shores of that frith, -many monuments appear, which would seem to carry the difference -between the present and the ancient level of the sea, to more than -forty feet. The ground on which the Botanic Garden of Edinburgh is -situated, after a thin covering of soil is removed, consists entirely -of sea sand, very regularly stratified, with layers of a black -carbonaceous matter, in thin lamellæ, interposed between them. Shells I -believe are but rarely found in it, but it has every other appearance -of a sea beach. The height of this ground above the present level of -the sea is certainly not less than forty feet. - -390. On almost every part of the coast where the rocks do not rise -quite abrupt and precipitous from the sea, similar marks of the -lowering of the sea, or the rising of the land, may be observed. On the -shores opposite to ours, the same appearances are remarked. The author -of the Lettre Critique to M. de Buffon, tells us, that he had found -the bottom of a bason at Dunkirk, which he had reason to think was dug -about 950 years ago, ten feet and a half above the present low water -mark, though it must have been originally under it. The bottom of this -bason is in the native chalk. From this, the same author concludes, -that the sea at Dunkirk lowers its level at the rate of an inch nearly -in seven years. The observation was made in 1762, (Lettre à M. le -Comte de Buffon, &c. p. 55.)[201] - -[Footnote 201: In the county of Suffolk, near Wood Bridge, at the -distance of seven or eight miles from the sea, are the Crag-pits, in -which prodigious quantities of sea shells are discovered, many of them -perfect and quite solid, (Pennant's Arctic Zoology, Introd. p. 6.) -Lincolnshire affords various proofs of the same kind; but some other -circumstances in the appearance of that coast, just about to be taken -notice of, indicate changes of a more complicated nature.] - -391. The shores of the Low Countries, and of Holland, have been often -instanced in proof of the same kind of changes, and it has been -supposed, that, independently of those artificial barriers which at -present exclude the waters of the ocean from overflowing a great part -of this tract, nature herself has brought it nearer to the surface -than it had formerly been. It is indeed certain, that those countries, -to a very great extent inland, have either been under the sea at some -period, by no means remote if compared with the great revolutions of -the globe, or that they are entirely alluvial, and of the same sort -with the Deltas formed at the mouths of rivers. The relative changes, -however, of the sea and land on this tract, have been differently -represented, and I am unwilling, on that account, to found any -argument on them. - -392. If we proceed farther to the north, to the shores of the Baltic -for instance, we have undoubted evidence of a change of level in the -same direction as on our own shores. The level of this sea has been -represented as lowering at so great a rate as 40 inches in a century. -Celsius observed, that several rocks which are now above water, -were not long ago sunken rocks, and dangerous to navigators; and he -particularly took notice of one, which, in the year 1680, was on the -surface of the water, and in the year 1791 was 20-1/2 Swedish inches -above it. From an inscription near Aspô, in the lake Melar, which -communicates with the Baltic, engraved, as is supposed, about five -centuries ago, the level of the sea appears to have sunk in that time -no less than 13 Swedish feet.[202] All these facts, with many more -which it is unnecessary to enumerate, make the gradual depression, -not only of the Baltic, but of the whole northern ocean, a matter of -certainty. - -[Footnote 202: Frisii Opera, tom. iii. p. 274.] - -393. Supposing these changes of level between the sea and land to be -sufficiently ascertained, the supposition which at first occurs is, -that the motion has been in the sea rather than in the land, and that -the former has actually descended to a lower level. The imagination -naturally feels less difficulty in conceiving, that an unstable -fluid like the sea, which changes its level twice every day, has -undergone a permanent depression in its surface, than that the land, -the _terra firma_ itself, has admitted of an equal elevation. In all -this, however, we are guided much more by fancy than reason; for, in -order to depress or elevate the absolute level of the sea, by a given -quantity, in any one place, we must depress or elevate it by the same -quantity over the whole surface of the earth; whereas no such necessity -exists with respect to the elevation or depression of the land. To -make the sea subside 30 feet all round the coast of Great Britain, it -is necessary to displace a body of water 30 feet deep over the whole -surface of the ocean. The quantity of matter to be moved in that way is -incomparably greater than if the land itself were to be elevated; for -though it is nearly three times less in specific gravity, it is as much -greater in bulk, as the surface of the ocean is greater than that of -this island. - -394. Besides, the sea cannot change its level, without a proportional -change in the solid bottom on which it rests. Though there be reason to -suppose that such changes in the bottom do actually take place, yet -they are probably much slower and more imperceptible than those which -we are here considering. It is evident, therefore, that the simplest -hypothesis for explaining those changes of level, is, that they proceed -from the motion, upwards or downwards, of the land itself, and not -from that of the sea. As no elevation or depression of the sea can -take place, but over the whole, its level cannot be affected by local -causes, and is probably as little subject to variation as any thing to -be met with on the surface of the globe. - -395. Other observations, however, made on different shores from the -preceding, give greater certainty to this conclusion, and make it -clear, that the motion or change which we are now treating of is not to -be ascribed to the sea itself. - -The observations just mentioned prove, that the level of the North -Sea is lower now than it was heretofore; but it appears, that in the -Mediterranean, the opposite takes place. Very accurate observations -made by MANFREDI, render it certain, that the superficies of the -Hadriatic was higher about the middle of the last century, than toward -the beginning of the Christian era. - -Some repairs that were carrying on in the cathedral church of Ravenna, -in the year 1731, afforded him an opportunity of observing, that the -ancient, and probably original, pavement, was four feet and a half -below the present, and nearly a foot under the level of the sea at high -water.[203] Now, when the church was built, this cannot have been the -position of the pavement, relatively to the level of the sea, for it -would have subjected the floor to be under water twice in twenty-four -hours, and must have done so the more unavoidably, because at that time -(the beginning of the fifth century) the walls of Ravenna were washed -by the sea. The fact that this pavement is under the high-water mark, -by the quantity just mentioned, was ascertained by actual levelling. -This result was confirmed by similar facts, observed by ZENDRINI at -Venice. - -[Footnote 203: Commentarii Academiæ Bononiensis, tom. ii. pars 1ma, p. -237, &c. and pars 2da, p. 1. &c.] - -396. Manfredi himself attributes all this to the elevation of the -surface of the sea, and has entered into a long calculation to -ascertain at what rate that surface may be supposed to rise, on account -of the earth and sand brought down by the rivers, and spread out over -the bottom of the sea. But as the fact of the rise of the level of the -sea is not general, and as the contrary is observed in the north seas, -as already proved, this hypothesis will not explain the apparent rise -in the level of the Hadriatic. - -397. Though a local subsidence, or settling of the ground, could hardly -account for this change, the pavement being perfect in its level, and -the walls of the cathedral without any shake, yet a subsidence that -has extended to a great tract, as to the whole of Italy, if the mass -moved has continued parallel to itself, and changed its place slowly, -will agree very well with the appearances. The facts here stated are -also the more deserving of attention, that about Ravenna, the land, at -the same time that it has sunk in its level, has extended its surface, -and has encroached on the sea. Since the time of AUGUSTUS, the line -of the coast has been carried farther out by about three miles.[204] -This last is the undoubted effect of the degradation of the land by the -rivers; and here we have very clear evidence of the forces, both under -and above the surface, producing their respective effects at the same -time, so that while the surface is raised by earth brought down by the -rivers, every given point in the ground is depressed and let down to a -lower level.[205] - -[Footnote 204: Manfredi, _ibid._] - -[Footnote 205: On the coast of Dalmatia also, the rising of the level -of the sea has been remarked, particularly at the ruins of Diocletian's -palace of Spalatro.] - -398. On the southern coast of Italy similar facts have been observed. -BREISLAC, in his _Topographia Fisica della Campagnia di Roma_,[206] -from certain appearances in the Gulfs of Baja and Naples, concludes, -that at the beginning of the Christian era, the level of the sea was -lower on that part of the coast than it is now. The facts which he -mentions are the following: _1mo_, The remains of an ancient road are -now to be seen in the Gulf of Baja at a considerable distance from -the land. _2do_, Some ancient buildings belonging to Porto Giulio are -at present covered by the sea. _3tio_, Ten columns of granite at the -foot of Monte Nuovo, which appear to have belonged to the Temple of -the Nymphs, are also nearly covered by the sea. _4to_, The pavement of -the Temple of Serapis is now somewhat lower than the high water mark, -though it cannot be supposed that this edifice when built was exposed -to the inconvenience of having its floor frequently under water. _5to_, -The ruins of a palace, built by Tiberius in the island of Caprea, are -now entirely covered by the sea. - -[Footnote 206: Cap. vi. p. 300.] - -Thus, it appears that the level of the sea is sinking in the more -northern latitudes, and rising in the Mediterranean, and it is evident -that this cannot happen by the motion of the sea itself. The parts -of the ocean all communicating with one another, cannot rise in one -place and fall in another; but, in order to maintain a level surface, -must rise equally or fall equally over the whole of its extent. If, -therefore, we place any confidence in the preceding observations, and -they are certainly liable to no objection, either from their own nature -or the character of the observers, we must consider it as demonstrated, -that the relative change of level has proceeded from the elevation or -depression of the land itself. This agrees well with the preceding -theory, which holds, that our continents are subject to be acted upon -by the expansive forces of the mineral regions; that by these forces -they have been actually raised up, and are sustained by them in their -present situation. - -399. According to some other facts stated by the same ingenious -author, it appears, that on the coast of Italy the progress of the -sea in ascending, or of the land in descending, has not been uniform -during the period above mentioned, but that different oscillations -have taken place; so that, from about the beginning of the Christian -era, till some time in the middle ages, the sea rose to be sixteen -feet higher than at present, from which height it has descended till -it became lower than it is now, and from that state of depression it -is now rising again. Breislac infers this from two facts, which he -combines very ingeniously with the preceding, viz. the remains of some -ancient buildings, at the foot of Monte Nuovo, five or six feet above -the present level of the sea, in which are found the shells of some -of those little marine animals that eat into stone: And again, the -marble columns of the temple of Serapis, which are also perforated -by pholades, to the height of sixteen feet above the ground. All -these changes Breislac ascribes to the motion of the sea itself; a -supposition which, as we have seen, cannot possibly be admitted, since -nothing can permanently affect the level of the sea in one place, which -does not affect it in all places whatsoever. - -400. Appearances, which indicate such alternations as have just been -mentioned in the level of the sea, are to be met with on some other -coasts. In England, on the coast of Lincolnshire, the remains of a -forest have been observed, which are now entirely covered by the -sea.[207] The submarine stratum which contains the remains of this -forest, can be traced into the country to a great distance, and is -found throughout all the fens of Lincolnshire. The stratum itself is -about four feet thick; it is covered in some places by a bed of clay -sixteen feet thick, and under it for twenty feet more is a bed of soft -mud, like the scourings of a ditch, mixed with shells and silt. - -[Footnote 207: Phil. Trans. 1799, p. 145.] - -Here then we have a stratum which must have been once uppermost on the -surface of the dry land, though one part of it is now immersed under -the sea, and another covered with earth, to the depth of sixteen feet. -A change of level in the sea itself will not explain these appearances: -they can only be explained by supposing the whole tract of land to -have subsided, which is the hypothesis adopted by the author of the -description in the Transactions, M. CORRIA DE SERRA; the subsidence, -however, is not here understood to arise from the mere yielding of -some of the strata immediately underneath, but is conceived to be a -part of that geological system of alternate depression and elevation -of the surface, which probably extends to the whole mineral kingdom. -To reconcile all the different facts, I should be tempted to think, -that the forest which once covered Lincolnshire, was immersed under the -sea by the subsidence of the land to a great depth, and at a period -considerably remote; that when so immersed, it was covered over with -the bed of clay which now lies on it, by deposition from the sea, and -the washing down of earth from the land; that it has emerged from this -great depth till a part of it has become dry land; but that it is now -sinking again, if the tradition of the country deserves any credit, -that the part of it in the sea is deeper under water at present than -it was a few years ago. This might also serve to reconcile, in some -measure, the phenomena of this submarine forest with the appearances -which indicate an extension of the land on the coast of Lincolnshire. -Indeed the extension of the land is no direct proof, either of its own -elevation, or of the depression of the sea, as we may conclude from the -instance of Ravenna already mentioned. - -401. We have concluded from the facts stated above, that the level of -the sea rises in the Mediterranean, and sinks in the more northern -latitudes; and thence some have suspected, that the level of the sea -had in general a tendency to rise towards the equator, and to sink -towards the poles. This is the notion of Frisi, as has been already -remarked, and he suggests, that this rise of the sea may be owing to a -slight acceleration in the earth's diurnal motion. But there are facts -which show, that between the tropics the relative level of the sea -and land has sunk, and is lower at present than it was at some former -period, probably not extremely remote. The opinion of Frisi, therefore, -is unsupported by observation, and, as has been already shown, cannot -be justified from theory. - -Between the tropics, islands are formed from the mere accumulation -of coral; and it is the peculiarity of those regions, to produce -rocks that have not passed through the usual process of mineral -consolidation.[208] The islets, however, which are thus formed, must -have their bases laid on a solid rock, though perhaps at a great -depth; and it is not probable, that after they are once raised above -the surface of the sea, they can still rise farther, except by some -elevation of the rock which serves as their foundation.[209] Now, -at Palmerston island, which comprehends nine or ten low islets, that -may be reckoned the heads of a great reef of coral rock, Captain -Cook informs us of his having seen, "far beyond the reach of the -sea, even in the most violent storms, elevated coral rocks, which, -on examination, appeared to have been perforated in the same manner -that the rocks are that now compose the outer edge of the reef. This -evidently shows," he adds, "that the sea had formerly reached so far; -and some of these perforated rocks were almost in the centre of the -island."[210] - -[Footnote 208: Dr Foster, in his Voyage round the World, (vol. ii. p. -146,) gives an instance in the South Sea Islands, where the surface of -the island, though entirely a coral rock, was raised forty feet above -the level of the sea.] - -[Footnote 209: A very curious account of the formation of such islands -is given by A. Dalrymple, Esq., in the Philosophical Transitions, vol. -lvii. p. 394.] - -[Footnote 210: Cook's Third Voyage, vol i. p. 221.] - -The same excellent navigator, giving an account of the peninsula at -Cape Denbigh, remarks: "It appeared to me, that this peninsula must -have been an island in remote times; for there were marks of the sea -having flowed over the isthmus." - -402. We are here touching on one of those subjects, where we feel much -the want of accurate and ancient observations, and where it is not from -the infancy, but the maturity of science that any thing approaching -to certainty can be looked for. The utmost that we can expect at -present, is an anticipation, which future ages must certainly modify -and correct. The best thing, in the mean time, that can be done for the -advancement of this branch of geological knowledge, is to ascertain -with exactness the relative level of the sea, and of such points upon -the land as can be distinctly marked, and pointed out to succeeding -ages. This is not so easy as it may at first appear. Where every object -changes, it is difficult to find a measure of change, or a fixed point -from which the computation may begin. The astronomers already feel -this inconvenience, and when they would refer their observations to -an immoveable plane, that shall preserve its position the same in all -ages, they meet with difficulties, which cannot be removed but by a -profound mathematical investigation. - -In geology, we cannot hope to be delivered from this embarrassment in -the same manner; and we have no resource but to multiply observations -of the difference of level; to make them as exact as possible, and -to select points of comparison that have a chance of being long -distinguished. The improvements in barometrical measurements, which -give such facility to the determination of heights, along with so -considerable a degree of accuracy, will furnish an accumulation of -facts that must one day be of great value to the geologist. - - - - - NOTE XXII. § 123. - - _Fossil Bones._ - - -403. The remains of organized bodies, at present included in the solid -parts of the globe, may be divided into three classes. The first -consists of the shells, corals,-and even bodies of fish, and amphibious -animals, which are now converted into stone, and make integrant parts -of the solid rock. All these are parts of animals that existed _before -the formation of the present land_, or even of the rocks whereof it -consists. These remains have been already treated of, and the evidence -which they furnish must ever be regarded as of the utmost importance -in the theory of the earth. The second class consists of remains, -which, by the help of stalactitical concretions, are converted into -stone. These are the exuviæ of animals, which existed on the very same -continents on which we now dwell, and are no doubt the most ancient -among their inhabitants, of which any monument is preserved. In -comparison of the first class, they must, nevertheless, be considered -as of very modern origin. - -404. The third class consists of the bones of animals found in the -loose earth or soil; these have not acquired a stony character, and -their nature appears to be but little changed, except by the progress -of decomposition and of mouldering into earth. No decided line can be -drawn between the antiquity of this and the preceding class, as there -may be between the preceding and the first. In some instances, the -objects of this third class may be coeval with those of the second; in -general, they must be accounted of later origin, as they are certainly -not preserved in a manner so well fitted for long continuance. - -405. The animal remains of the second class, are generally found in -the neighbourhood of limestone strata, and are either enveloped or -penetrated by calcareous, or sometimes ferruginous matter. Of this -sort are the bones found in the rock of Gibraltar, and on the coast -of Dalmatia. The latter are peculiarly marked for their number, and -the extent of the country over which they are scattered, leaving it -doubtful whether they are the work of successive ages, or of some -sudden catastrophe that has assembled in one place, and overwhelmed -with immediate destruction, a vast multitude of the inhabitants of -the globe. These remains are found in greatest abundance in the -islands of Cherso and Osero ; end always in what the Abbé FORTIS calls -an _ocreo-stalactitic earth_. The bones are often in the state of -mere splinters, the broken and confused relics of various animals, -concreted with fragments of marble and lime, in clefts and chasms of -the strata.[211] Sometimes human bones are said to be found in these -confused masses. - -[Footnote 211: Travels into Dalmatia, p. 449.] - -406. A very remarkable collection of bones in this state is found -in the caves of Bayreuth in Franconia. Many of these belong, as is -inferred with great certainty from the structure of their teeth, to -a carnivorous animal of vast size, and having very little affinity -to any of those that are now known. The bones are found in different -states, some being without any stalactitical concretion, and having -the calcareous earth still united to the phosphoric acid, so that -they belong to the third, rather than the second, of the preceding -divisions. In others, the phosphoric acid has wholly disappeared, and -given place to the carbonic. - -The number of these bones, accumulated in the same place, is matter of -astonishment, when it is considered, that the animals to which they -belonged were carnivorous, so that more than two can never have lived -in the same cavern at the same time. The caves of Bayreuth seem to have -been the den and the tomb of a whole dynasty of unknown monsters, that -issued from this central spot to devour the feebler inhabitants of the -woods, during a long succession of ages, before man had subdued the -earth, and freed it from all domination but his own. - -407. The fossil bones of the second and third class, but chiefly of the -third, have now afforded matter of conjecture and discussion for more -than a century. The facts with respect to them are very numerous and -interesting, but can be considered here only very generally. - -The remains of this kind, consist of the bones only of large animals, -so that they have generally been compared with those of the elephant, -the rhinoceros, the hippopotamus, or other animals of great size The -bones of smaller animals have also been found, but much more rarely -than the other. It is usually remarked, that the bones thus discovered -in the earth are larger than those of the similar living animals. - -Another general fact concerning these remains, is, that they are found -in all countries whatsoever, but always in the loose or travelled -earth, and never in the genuine strata. Since the year 1696, when the -attention of the curious was called to this subject, by the skeleton -of an elephant dug up in Thuringia, and described by Tentzelius,[212] -there is hardly a country in Europe which has not afforded instances -of the same kind. Fossil bones, particularly grinders and tusks of -elephants, have been found in other places of Germany, in Poland, -France, Italy, Britain, Ireland, and even Iceland.[213] Two countries, -however, afford them in greater abundance by far than any other part of -the known world; namely, the plains of Siberia in the old continent, -and the flat grounds on the banks of the Ohio in the new.[214] - -[Footnote 212: Phil. Trans. vol. xix. p. 757.] - -[Footnote 213: A grinder of an elephant found in Iceland, is described -by _Bartholinus_, Acta Hafniens. vol. i. p. 83.] - -[Footnote 214: The fossil bones on the Ohio are described in two papers -by Mr P. Collinson, Phil. Trans. vol. lvii. p. 464 and 468.] - -408. When the bones in Siberia were first discovered, they were -supposed to belong to an animal that lived under ground, to which -they gave the name of the _mammouth_; and the credit bestowed on this -absurd fiction, is a proof of the strong desire which all men feel -of reconciling extraordinary appearances with the regular course of -nature. Much skill, however, in natural history was not required to -discover that many of the bones in question resembled those of the -elephant, particularly the grinders and the tusks of that animal. -Others resembled the bones of the rhinoceros; and a head of that kind, -having the hide preserved upon it, was found in Siberia, and is still -in the imperial cabinet at Petersburgh. - -Pallas has described the fossil bones which he found in the museum at -Petersburgh, on his being appointed to the superintendence of it, and -enumerates, not only bones that belong, in his opinion, to the elephant -and rhinoceros, but others that belong to a kind of buffalo, very -different from any now known, and of a size vastly greater.[215] He has -also described, in another very curious memoir, the bones of the same -kind that he met with in his travels through the north-east parts of -Asia. - -[Footnote 215: Novi Comment Petrop. tom. xiii. (1768,) p. 436, and tom. -xvii. p. 576, &c.] - -The fossil bones found on the banks of the Ohio, resemble in many -things those of Siberia; like them they are contained in the soil or -alluvial earth, and never in the solid strata; like them too they are -no otherwise changed from their natural state, than by being sometimes -slightly calcined at the surface; they are also of great size, and in -great numbers, being probably the remains of several different species. - -409. Two inquiries concerning these bones have excited the curiosity -of naturalists; first, to discover among the living tribes at present -inhabiting the earth, those to which the fossil remains may with the -greatest probability be referred; and, secondly, to find out the cause -why these remains exist in such quantities, in countries where the -animals to which they belong, whatever they be, are at present unknown. -The solution of the first of these questions, is much more within our -reach than the second, and at any rate must be first sought for. - -On the authority of so eminent a naturalist as Pallas, the bones from -Siberia may safely be referred to the elephant, the rhinoceros, and -buffalo, as mentioned above, though perhaps to varieties of them with -which we are not now acquainted. With respect to the bones of North -America, the question is more doubtful, for they have this particular -circumstance attending them, viz. that along with the thighbones, -tusks, &c. which might be supposed to belong to the elephant, grinders -are always found of a structure and form entirely different from -the grinders of that animal.[216] Some naturalists, particularly M. -DAUBENTON, referred these grinders to the hippopotamus; but Dr W. -HUNTER appears to have proved, in a very satisfactory manner, that they -cannot have belonged to either of the animals just mentioned, but to a -_carnivorous_ animal of enormous size, the race of which, fortunately -for the present inhabitants of the earth, seems now to be entirely -extinct.[217] The foundation of Dr Hunter's opinion is, that in these -grinders the enamel is merely an external covering; whereas, in the -elephant, and other animals destined to live on vegetable food, the -enamel is intermixed with the substance of the tooth.[218] - -[Footnote 216: See Mr Collinson's papers, above referred to. Phil. -Trans. vol. lvii.] - -[Footnote 217: Phil. Trans. vol. lviii. p. 3, &c.] - -[Footnote 218: A fossil grinder in the collection of JOHN MACGOWAN, -Esq. of Edinburgh, answers nearly to Mr Collinson's description, and is -very well represented by the figure which accompanies it. This grinder -weighs four pounds one-fourth avoirdupois; the circumference of the -_corona_ is eighteen inches; the coat of enamel is one-fourth of an -inch thick; there are five double teeth; in Mr Collinson's specimen -there are only four.] - -410. Though this argument appears to be of considerable weight, yet -CAMPER, who was greatly skilled in comparative anatomy, and who had -studied this subject with particular attention, was of opinion, that -these grinders belong to a species of elephant. This opinion he states -in a letter to Pallas, who had found grinders and other bones of this -same animal, on the western declivity of the Ural mountains.[219] -Camper denies that the animal is carnivorous, because the _incisores_, -or canine teeth, are wanting; and he argues farther, from the weight of -the head, which may be inferred from the weight of the grinders, that -the neck must have been short, and the animal must have been furnished -with a _proboscis_. He afterwards abandoned the latter hypothesis, and -gave it as his opinion that the _incognitum_ was neither carnivorous, -nor a species of the elephant.[220] - -[Footnote 219: Acta Acad. Petrop. tom. i. (1777,) pars posterior, p. -213, &c.] - -[Footnote 220: _Ibid._ tom. ii. (1784,) p. 262.] - -411. Nevertheless, CUVIER, in a _mémoire_ read before the National -Institute of Paris, maintains, that the fossil bones of the new -Continent, as well as most of those of the old, belong to certain -species of the elephant; of which, at least, two do not now exist, and -are only known from remains preserved in the ground. He distinguishes -them thus:[221] - -[Footnote 221: Mémoires de l'Institut National, Sciences Physiques, -tom. ii. p. 19, &c.] - -_Elephas mammonteus_,--_maxillâ obtusiore, lamellis molarium tenuibus, -rectis_. - -_Elephas Americanus_,--_molarities multicuspidibus, lamellis post -detritionem quadric-lobatis_. - -The latter species, which is meant to include the _animal incognitum_, -is said to have lived, not only in America, but in many parts of the -old Continent. Yet some late inquiries into the structure of the teeth -of graminivorous animals, and particularly of the elephant, make it -very improbable that the _incognitum_ has belonged to this genus.[222] -The grinders of the elephant have been found to consist of three -substances, enamel, bone, and what is called the _crusta petrosa_, -applied in layers, or folds contiguous to one another; and no vestige -of this structure appears in the grinders of the unknown animal of the -Ohio.[223] At the same time, Dr Hunter's assertion, that this animal -was carnivorous, is rendered doubtful, not only by the want of _canine_ -teeth, but also from the resemblance between its grinders and those of -the wild boar, which Mr Home has observed to be considerable.[224] The -grinder of the boar is similar to that of the elephant, in the extent -of the masticating surface, but not at all in the internal structure; -and the same is true of the tooth of the _animal incognitum_, so that -a considerable probability is established, that it and the boar are of -the same genus, and both destined to live occasionally either on animal -or vegetable food. - -[Footnote 222: See Mr Home's Observations on the Teeth of Graminivorous -Animals, Phil. Trans. 1799. Also, an Essay on the Structure of the -Teeth, by Dr Blake.] - -[Footnote 223: In a paper inserted in the fourth volume of the American -Philosophical Transactions, an account is given of two different -grinders that are found at the Salt Licks near the Ohio. One of them -resembles the grinder of the elephant, and may have belonged to the -_Elephas Americanus_ of Cuvier; the other agrees pretty nearly with the -grinder of Dr Hunter's _animal incognitum_. The author of the paper -thinks that the _animal incognitum_ was not wholly carnivorous, as the -incisores, or canine teeth, are never found. At the Great Bone Lick, -bones of smaller animals, particularly of the buffalo kind, have been -discovered. The saline impregnation of the earth at these Licks must -no doubt have contributed to the preservation of the bones. Trans. -American Phil. Soc. vol. iv. (1799,) p. 510, &c.] - -[Footnote 224: Observations on the Grinding Teeth of the wild boar and -_animal incognitum_. Phil. Trans. 1801, p. 319.] - -412. Another _animal incognitum_ found in South America has been -described by Cuvier, and appears to be of a different genus from the -_incognitum_ of the North. Thus, if we include the two _incognita_ of -America, the _elephas mammonteus_, the unknown buffalo of Pallas, and -the great animal of Bayreuth, we have at least five distinct genera, -or species of the animal kingdom, which existed on our continents -formerly, but do not exist on them now. The number is probably much -greater: Pallas mentions fossil horns of a gazelle, of an unknown -species; and horns of deer are often found, that cannot be referred to -any species now existing. Those extinct races have been remarkable for -their size: some of the ancient elephants appear to have been three -times as large as any of the present.[225] - -[Footnote 225: Camper, Nov. Acta Petrop. tom. ii. (1784) p. 257.] - -413. The inhabitants of the globe, then, like all the other parts of -it, are subject to change. It is not only the individual that perishes, -but whole _species_, and even perhaps _genera_, are extinguished. It -is not unnatural to consider some part of this change as the operation -of man. The extension of his power would necessary subvert the balance -that had before been established between the inhabitants of the earth, -and the means of their subsistence. Some of the larger and fiercer -animals might indeed dispute with him, for a long time, the empire of -the globe; and it may have required the arm of a Hercules to subdue -the monsters which lurked in the caves of Bayreuth, or roamed on the -banks of the Ohio. But these, with others of the same character, were -at length exterminated: the more innocent species fled to a distance -from man; and being forced to retire into the most inaccessible parts, -where their food was scanty, and their migration checked, they may have -degenerated from, the size and strength of their ancestors, and some -species may have been entirely extinguished. - -But besides this, a change in the animal kingdom seems to be a part of -the order of nature, and is visible in instances to which human power -cannot have extended. If we look to the most ancient inhabitants of the -globe, of which the remains are preserved in the strata themselves, -we find in the shells and corals of a former world hardly any that -resemble exactly those which exist in the present. The species, except -in a few instances, ate the same, but subject to great varieties. The -vegetable impressions on slate, and other argillaceous stones, can -seldom be exactly recognised; and even the insects included in amber -are different from those of the countries in which the amber is found. - -414. Supposing, then, the changes which have taken place in the -qualities and habits of the animal creation, to be as great as those -in their structure and external form, we can have no reason to wonder -if it should appear that some have formerly dwelt in countries from -which the similar races are now entirely banished. The power of living -in a different climate, of enduring greater degrees of cold or of -heat, or of subsisting on different kinds of food, may very well have -accompanied the other changes. Though one species of elephant may -now be confined to the southern parts of Asia, another may have been -able to endure the severer climates of the north; and the same may -be true of the buffalo or the rhinoceros. In all this no physical -impossibility is involved; though whether it is a probable solution of -the difficulty concerning the origin of these animal remains, can only -be judged of from other circumstances. - -415. If we consider attentively the facts that respect the Siberian -fossil bones, there will appear insurmountable objections to every -theory that supposes them to be exotic, and to have been brought into -their present situation from a distant country. - -The extent of the tract through which these bones are scattered, is a -circumstance truly wonderful. Pallas assures us,[226] that there is not -a river of considerable size in all the north of Asia, from the Tanais, -which runs into the Black Sea, to the Anadyr, which falls into the Gulf -of Kamtchatka, in the sides or bottom of which bones of elephants and -other large animals have not been found. This is especially the case -where the rivers run in plains through gravel, sand, clay, &c.; among -the mountains, the bones are rarely discovered. The extent of the tract -just mentioned exceeds four thousand miles; and how the bones could -be distributed over all that extent, by any means but by the animals -having lived there, it seems impossible to conceive. No torrent nor -inundation could have produced this effect, nor could the bones brought -in that way have been laid together so as to form complete skeletons. - -[Footnote 226: De Reliquiis Animalium exoticorum, per Asiam Borealem -repertis.--"Nov. Comment Petrop. tom. xvii. (1772,) p. 576.] - -416. One fact recorded by the same author, seems calculated to remove -all uncertainty. It is that of the carcase of a rhinoceros, almost -entire, and covered with the hide, found in the earth in the banks of -the river Wilui, which falls into the Lena below Jakutsk.[227] Some of -the muscles and tendons were actually adhering to the head when Pallas -received it. The head, after being dried in an oven, is still preserved -in the museum at Petersburgh. The preservation of the skin and muscles -of this natural mummy, as Pallas calls it, was no doubt brought -about by its being buried in earth that was in a state of perpetual -congelation; for the place is in the parallel of 64°, where the ground -is never thawed but to a very small depth below the surface. - -[Footnote 227: Pallas _ubi supra_, p. 586. Also, Voyages de Pallas, -tom. iv. p. 131.] - -But by what means can we account for the carcase of a rhinoceros being -buried in the earth, on the confines of the polar circle? Shall we -ascribe it to some immense torrent, which, sweeping across the deserts -of Tartary, and the mountains of Altai, transported the productions of -India to the plains of Siberia, and interred in the mud of the Lena -the animals that had fed on the banks of the Barampooter or the Ganges? -Were all other objections to so extraordinary a supposition removed, -the preservation of the hide and muscles of a dead animal, and the -adhesion of the parts, while it was dragged for 2000 miles over some -of the highest and most rugged mountains in the world, is too absurd -to be for a moment admitted. Or shall we suppose that this carcase has -been floated in by an inundation of the sea, from some tropical country -now swallowed up, and of which the numerous islands of the Indian -Archipelago are the remains? The heat of a tropical climate, and the -putrescence naturally arising from it, would soon, independently of all -other accidents, have stripped the bones of their covering. Indeed this -_instantia singularis_, as in every sense it may properly be called, -seems calculated for the express purpose of excluding every hypothesis -but one from being employed to explain the origin of fossil bones. -It not only excludes the two which have just been mentioned, but it -excludes also that of Buffon, viz. that these bones are the remains of -animals which lived in Siberia, when the arctic regions enjoyed a fine -climate, and a temperature like that which southern Asia now possesses. -From the preservation of the flesh and hide of this rhinoceros, it is -plain, that when the body was buried in the earth, the climate was -much the same that it is now, and the cold sufficient to resist the -progress of putrefaction. - -Pallas takes notice of the inconsistency of the state of this skeleton, -with the hypothesis of Buffon; but he does not observe that the -inconsistency is equally great between it and his own hypothesis, the -importation of the fossil bones by an inundation of the sea, and that -flesh or muscle must have been entirely consumed long before it could -be carried by the waves to the parallel of 64°, from any climate which -the rhinoceros at present inhabits. - -417. The presence of petrified marine objects in places where some of -the fossil bones are found, is no proof that the latter have come from -the sea, though it is produced as such both by Pallas himself, and -afterwards by Kirwan. These marine bodies are the shells and corals -that have been parts of calcareous rocks, from which being detached -by the ordinary progress of disintegration, they are now contained in -the beds of sand or gravel where the animal remains are buried. They -have nothing in common with these remains; they are real stones, and -belong to another, and a far more remote epochs. Such objects being -found in the same place where the bones lie, argues only that the -strata in the higher grounds, from which the gravel has come, are -calcareous; and nothing can show in a stronger light the necessity of -distinguishing the different condition of fossil bodies, united by the -mere circumstance of contiguity, before we draw any inference as to -their having a common origin. If the marine remains were in the same -condition with the bones; if they were in no respect mineralized; then -the conclusion, that both had been imported by the sea, would have -great probability; but without that, their present union must be held -as casual, and can give no insight into the origin of either. - -418. On the whole, therefore, no conclusion remains, but that these -bones have belonged to species of elephants, rhinoceros, &c. which -inhabited the very countries where their remains are now buried, and -which could endure the severity of the Siberian climate. The rhinoceros -of the Wilui certainly lived on the confines of the Polar Circle, and -was exposed to the same cold while alive, by which, when dead, its body -has been so long, and so curiously preserved. - -These animals may also have lived occasionally farther to the south, -among the valleys between the great ranges of mountains that bound -Siberia on that side. Fossil bones are but rarely found in these -valleys, probably because they have been washed down from thence into -the plains. We must observe, too, that those animals may have migrated -with the seasons, and by that means avoided the rigorous winter of the -high latitudes. The dominion of man, by rendering such migration to -the larger animals difficult or impossible, must have greatly changed -the economy of all those tribes, and narrowed the circle of their -enjoyments and existence. The heaps in which the fossil bones appear to -be accumulated in particular places, especially in North America, have -a great appearance of being connected with the migrations of animals, -and the accidents that might bring multitudes of them into the same -spot. - -What holds of Siberia and of North America, is applicable, _a -fortiori_, to all the other places where animal remains are found -in the same condition. Thus we are carried back to a time when many -larger species of animals, now entirely extinct, inhabited the earth, -and when varieties of those that are at present confined to particular -situations, were, either by the liberty of migration, or by their -natural constitution, accommodated to all the diversities of climate. -This period, though beyond the limits of ordinary chronology, is -posterior to the great revolutions on the earth's surface, and the -latest among geological epochs. - - - - - NOTE XXIII. § 128. - - _Geology of_ KIRWAN _and_ DE LUC. - - -419. The two champions of the Neptunian system, who have distinguished -themselves most by their hostility to Dr HUTTON, are DE LUC and KIRWAN. -They have carried on their attack nearly on the same plan, and have -employed against their antagonist the weapons both of theology and -science. With a spirit as injurious to the dignity of religion, as to -the freedom of philosophical inquiry, they have disregarded a maxim -enforced by the authority of Bacon, and by all our experience of the -past; "_Tanto magis hæc vanitas inhibenda venit et coërcenda, quia, -ex divinorum et humanorum male-sana admixtione, non solum educitur -philosophia phantastica, sed etiam religio hæretica. Itaque salutare -admodum est, si mente sobriâ, fidei tantum dentur quæ fidei sunt_."[228] - -[Footnote 228: The whole passage is deserving of attention, and -it seems as if the prophetic spirit of Bacon had addressed it to -the cosmologists of the present day. "_Pessima enim res errorem_ -APOTHEOSIS, _et pro peste intellectús habenda est, si vanis accedat -veneratio. Huic autan vanitati nonnulli ex modernis summâ levitate ita -indulserunt, ut, in primo capitolo_ GENESEOS, _et aliis Scripturis -Sacris, philosophiam naturalem fundari conati sunt:_ Inter VIVA -quærentes MORTUA.--"Nov. Organum, lib. i. aphor. 65] - -Proceeding, accordingly, in direct opposition to rules that, have never -yet been violated with impunity, and mistaking the true object of a -theory of the earth, they carry back their inquiries to a period prior -to the present series of causes and effects, where, having neither -experience nor analogy to direct them, they pretend to be guided by -a superior light. They would have us to consider their geological -speculations as a commentary on the text of MOSES; they endeavour to -explain the action of creative power, and, with indiscreet curiosity, -would tear off the veil which the hand of the prophet has so wisely -respected. But the veil cannot be torn off, and all that is behind it -must be to man as that which never has existed. - -420. M. De Luc has nevertheless treated very diffusely of the history -of the solar system, previous to the establishment of the present laws -of nature, and has dwelt on it with great complacency, and singular -minuteness of detail. His tenth letter to LA METHERIE has the following -title: - -"On the History of the Earth, from the time when that planet was -penetrated by _light_, till the appearance of the sun; a portion of -time which includes the origin of heat, and of the figure of the -earth; of its primeval strata, of the ancient sea, of our continents, -as the bottom of that sea, of the great chains of mountains, and of -vegetation."[229] - -[Footnote 229: Journal de Physique, tom. 37. (1790,) partie 2de, p. -332. As I may not have done justice to this extraordinary title, it may -be right to present it in the original. "Sur l'Histoire de la TERRE, -depuis que cette planette fut penetrée de LUMIERE, jusqu'à l'apparition -du SOLEIL; espace de tems qui renferme les ORIGINES de la _chaleur_, -et de la _figure_ de notre globe; de ses _couches primordiales_, de -_l'ancienne mer_, de nos _continens_, comme fond de cette mer, de leurs -grandes chaînes de _montagnes_, et de la _vegetation_."] - -I must confess that I am unacquainted with every thing of this letter -but the title; and could not easily be prevailed on to follow any man -who professedly goes out of nature in search of knowledge; who pretends -to give the history of our planetary system when there was no sun, -and to enumerate the events which took place between the existence of -that luminary, and the existence of light. The absurdity of such an -undertaking admits of no apology; and the smile which it might excite, -if addressed merely to the fancy, gives place to indignation when it -assumes the air of philosophic investigation. - -421. It sets, however, in a strong light, the inconsistencies that -may be observed in the intellectual character of the same individual, -to consider that the author of this strange and inconsistent -reverie, is, nevertheless, an excellent observer, and well skilled in -experimental inquiries. It will hardly be believed that he who writes -the history of the earth before the formation of the sun, is versed -in the principles of inductive reasoning; and that he has added much -to the stock of geological knowledge, having observed accurately, and -described with great perspicuity and candour. His _Lettres Physiques_ -are full of valuable and just observations, though accompanied with -reasonings that do not seem always entitled to the same praise; and -in another work he has succeeded where many men of genius had failed, -and has made considerable improvements in a branch of the mathematics, -without borrowing almost any assistance from the principles of that -science.[230] - -[Footnote 230: Essai sur les Modifications de l'Atmosphere.] - -422. Some of the same observations apply to Mr Kirwan. His Geological -Essays have also for their object to explain the first origin of -things; and to say that he has not succeeded, in an attempt where no -man ever can succeed, implies no reproach on the execution of his -work, whatever it may do on the design. We have indeed no criterion by -which the execution of it can be estimated: what would in any other -place be a blemish, may be here deserving of praise; and if the work -is full of confusion and perplexity, these are qualities inherent in -the subject which it is intended to describe. It were, no doubt, to -be wished, that after emerging into the regions of day, Mr Kirwan had -been as successful in copying the beauty and simplicity of nature, as -in representing the disorder and inconsistency of the chaotic mass. -But his cosmology is without unity in its principles, or consistency -in its parts; the causes introduced, are, for the most part, such as -will account for one set of appearances just as well as for another; -or, if any of them is likely to prove inadequate to the effect ascribed -to it, a new and arbitrary hypothesis is always ready to come to its -assistance. The information given is seldom exact: a multitude of facts -brought together, without the order and discussion essential to precise -knowledge; and an infinity of quotations, amassed without criticism or -comparison, afford proofs of extensive reading, but of the most hasty -and superficial inquiry. Thus we have seen passages from ULLOA and -FRISI, produced in support of opinions, which, when fairly stated, they -had the most direct tendency to overthrow. - -423. In one respect, the geological writings of Kirwan are far inferior -to De Luc's: They are evidently the productions of a man who has not -seen nature with his own eyes; who has studied mineralogy in cabinets, -or in books only; but who has seldom beheld fossils in their native -place. With the balance in his hand, and the external characters of -WERNER in his view, he has examined minerals with diligence, and has -discovered many of those marks which serve to ascertain their places, -in a system of artificial arrangement. But to _reason_ and to _arrange_ -are very different occupations of the mind; and a man may deserve -praise as a mineralogist, who is but ill qualified for the researches -of geology. - -424. The same hurry and impatience are visible in the manner in which -his argument against Dr Hutton is usually conducted. He has seldom been -careful to make himself master of the opinions of his adversary; and -what he gives as such, and directs his reasonings against, have often -no resemblance to them whatsoever. Without any intention to deceive -others, but deceived himself, he usually begins with misrepresenting Dr -Hutton's notions, and then proceeds to the refutation of them. In this -imaginary contest, it will readily be supposed, that he is in general -successful: when a man has the framing both of his own argument, and -that of his antagonist, he must be a very unskilful logician if he does -not come off with the advantage. - -425. It is but justice, however, to the Neptunists, to acknowledge, -that they are not all liable to the censure of beginning their -researches from a period antecedent to the existence of the laws of -nature. This absurdity does not, so far as I know, infect the system of -Werner. That mineralogist has not proposed to explain the first origin -of things, though he has supposed, at some former period, a condition -of the globe very unlike the present, viz. the entire submersion of the -solid under the fluid part. - - - - - NOTE XXIV. § 129. - - _System of_ BUFFON. - - -426. The affinity of Dr Hutton's theory to that of Buffon, is nothing -more than what arises from their making use of the same agents, viz. -fire and water, in producing the present condition of the earth's -surface. In almost all other respects the two theories are extremely -different. The order in which those agents are employed in them, is -directly opposite, as has already been remarked; Buffon introducing the -action of fire first, and of water only in the second place, to waste -and destroy mineral bodies, and afterwards to dispose them anew, and -arrange them into strata. He makes no provision for the consolidation -of these strata, nor any for their angular elevation; he has no means -of explaining the unstratified rocks; nor any, but one extremely -imperfect, for explaining the inequalities of the earth's surface. - -Again, Buffon mistook, in some degree, the true object of a theory of -the earth; and though he did not go back, like the geologists just -named, to a time when the laws of nature were not fully established, -he begins from a condition of things too unlike the present to be the -basis of any rational speculation. He does not, indeed, undertake to -examine the state of our planetary system before the sun existed; for -from such extravagance, even when most disposed to indulge his fancy, -he would surely have revolted. But he treats of the world, when the -earth and the planets had just ceased to be a part of the sun, and were -newly detached from the body of that luminary.[231] - -[Footnote 231: According to Buffon, the granite is the true solar -matter, unchanged but by its congelation.] - -This hypothesis concerning the origin of the planets, contrived chiefly -to account for the circumstance of their motion being all in the -same direction, and in other respects not only unsupported, but even -inconsistent with the principle of gravitation, has nothing in common -with a theory, confined as Dr Hutton's is, within the field which must -for ever bound our inquiries, and not venturing to speculate about the -earth, when in a condition totally different from the present. - -427. In what relates to the future, the two systems are not more like -than in what relates to the past Buffon represents the cooling of our -planet, and its loss of heat, as a process continually advancing, and -which has no limit, but the final extinction of life and motion over -all the surface, and through all the interior, of the earth. The death -of nature herself is the distant but gloomy object that terminates -our view, and reminds us of the wild fictions of the Scandinavian -mythology, according to which, _annihilation_ is at last to extend -its empire even to the gods. This dismal and unphilosophic vision -was unworthy of the genius of Buffon, and wonderfully ill suited to -the elegance and extent of his understanding. It forms a complete -contrast to the theory of Dr Hutton, where nothing is to be seen beyond -the continuation of the present order; where no latent seed of evil -threatens final destruction to the whole; and where the movements are -so perfect, that they can never terminate of themselves. This is surely -a view of the world more suited to the dignity of NATURE, and the -wisdom of its AUTHOR, than has yet been offered by any other system of -cosmology. - -428. I have often quoted Buffon in, the course of these -_Illustrations_, and most commonly for the purpose of combating his -opinions; but I am very sensible, nevertheless, of the obligations -under which he has laid all the sciences connected with the natural -history of the earth. - -The extent and variety of his knowledge, the justness of his -reasonings, the greatness of his views, his correct taste, and manly -eloquence, qualified him, better, perhaps, than any other individual, -to compose the History of Nature. The errors into which he Has fallen, -are almost all the unavoidable consequences of the circumstances in -which he was placed; and if their amount is estimated by the proportion -that they bear to the general excellence of the work, they will be -reckoned but of small account. Buffon began to write when many parts -of natural history had made but little progress; when the quantity -of authentic information was small, and when scientific and correct -description was hardly to be found. Many of the greatest and most -important facts in geology were quite unknown, and scarcely any part -of the mineral kingdom had been accurately surveyed; and, with such -materials as this state of things afforded, it is not wonderful if -some parts of the edifice he erected have not proved so solid and -durable as the rest. Had he appeared somewhat later; had he been -farther removed from the time when reasonings _a priori_ usurped the -place of induction; and had he been as willing to correct the errors -into which he had been betrayed by imperfect information, as he was -ingenious in defending them, his work would probably have reached as -great perfection, as it is given for any thing without the sphere of -the accurate sciences to attain. If he had examined the natural history -of the earth more with his own eyes, and been as careful to delineate -it with fidelity as force; if he had listened with greater care to -the philosophers around him; had he attended to the demonstrations of -NEWTON more, and despised the arrangements of LINNÆUS less; he would -have produced a work, as singular for its truth as for its beauty, and -would have gone near to merit the eulogy pronounced by the enthusiasm -of his countrymen, MAJESTATI NATURÆ PAR INGENIUM. - - - - - NOTE XXV. § 130. - - _Figure of the Earth._ - - -429. That the earth is a spheroidal body, compressed at the poles, -or elevated at the equator, is a fact established by many accurate -experiments; and though these experiments do not exactly coincide, as -to the degree of oblateness which they give to that spheroid, they -agree sufficiently to put it beyond all dispute, that the earth, though -solid, has nearly the same figure which it would assume if fluid, in -consequence of its rotation on its axis. - -Now, it is not at all obvious, to what physical cause this phenomenon -is to be ascribed. The earth, as it exists at present, has none of the -conditions that render the assumption of the figure of equilibrium in -any way necessary to it. Constituted as it is, its parts cohere with -forces incomparably too great to obey the laws of statical pressure, -or to assume any one figure rather than another, on account of the -centrifugal tendency which results from its revolution on its axis. -There is no necessity that its superficies should be every where level, -or perpendicular to the direction of gravity, nor that every two -columns, standing on the same base, any where within it, and reaching -from thence to any two points of the surface, should be of such weights -as precisely to balance one another. Neither of these, indeed, is at -all conformable to fact. They are, however, the very suppositions on -which the determination of the spheroid of equilibrium is founded; and -as they certainly do in no degree belong to the earth, it seems strange -that the result deduced from them should be in any way applicable to -it. This coincidence remains, therefore, to be explained; and it must -greatly enhance the merit of any geological system, if it can connect -this great and enigmatical phenomenon with the other facts in the -natural history of the earth. - -430. To establish such a connection, has, accordingly, been a favourite -object with geologists, whether they have embraced the Neptunian or -Volcanic theory: both have thought that they were entitled to suppose -the primeval fluidity of the globe, the one by water, and the other -by fire; and in whatsoever way that fluidity was produced, the result -of it could be no other than the spheroidal figure of the whole mass, -agreeably to the laws of hydrostatics. If in this fluid state the earth -was homogeneous, the spheroid would be accurately elliptical, and the -compression at the poles would be 1/230 of the radius of the equator; -if the fluid was denser toward the centre, the flattening would be -less: and in either case, the body, as it acquired solidity, may be -supposed to have retained its spheroidal figure with little variation. -But though the fluidity of the earth will account for the phenomenon -of its oblate figure, it may reasonably be questioned, whether this -fluidity can be admitted, in consistency with other appearances. -According to what is established above, none of the appearances in the -mineral kingdom indicate more than a partial fluidity in any former -condition of the earth. The present strata, made up as they are of the -ruins of former strata, though softened by heat, have not been rendered -fluid by it, and have even possessed their softness in parts, and in -succession, not altogether, nor at the same time. - -The unstratified, and more crystallized substances, were cast in the -bosom of others, which were solid at the time when they were fluid. In -all this, therefore, there is no indication of a fluidity prevailing -through the whole mass, or even over the whole surface of the earth, -and therefore nothing that can explain the spheroidal figure which it -has acquired. The supposition, then, of the entire body of the earth, -or even of its external crust, having been fluid, though it might -account for the compression at the poles, does not connect that fact -with the other facts in the natural history of the globe, and fails, -therefore, in the point most essential to a theory. It is liable, also, -to other objections, whether it be conceived to have proceeded from -fire or from water; whether it has happened on the principles of Buffon -or of Werner. - -431. First, let us suppose that the fluidity of the earth, or of the -external crust of it, at least to a certain depth, proceeded from a -solution of the whole in the waters of the ocean; and, waving all the -objections that have been stated to this hypothesis, on account of -the absolute insolubility of many mineral substances in water, let us -suppose them all soluble in a certain degree, and let us compute the -quantity of the menstruum, which, on the suppositions most favourable -to the system, must have been required to this great geologico-chemical -operation. - -The siliceous earth, though not soluble in water _per se_, yet, after -being dissolved in that fluid by means of an alkali, was found by Dr -Black, in his analysis of the Geyser water, to remain suspended in a -quantity of water, between 500 and 1000 times its own weight. This is -one of the facts most favourable to the Neptunian theory; and that -every advantage may be given to that theory, we shall take the least of -the numbers just mentioned, and suppose that siliceous earth may be -dissolved or suspended in 500 times its weight of water. - -Taking this for the extreme degree of insolubility of mineral -substances, (though there are many of which the insolubility is -absolute, or, to speak in the language of calculation, infinitely -great,) we may suppose the insolubility of all the rest, or the -quantities of water in which they are dissolved, to be ranged in a -descending scale from 500 to 0, the extreme degree of deliquescence. -Then, taking the arithmetical mean between these extremes, it will give -us 250, as the proportion of water in which mineral substances may at -an average be dissolved. But this average is much less than the truth; -for the quantity of siliceous earth is great in comparison of any of -the rest, and the mineral substances that are extremely soluble in -water are but in a small quantity; therefore, when we suppose mineral -bodies, at a medium, to be soluble in 250 times their own weight of -water, we make a supposition extremely favourable to the Neptunian -system. - -432. This is the proportion between the _weight_ of the solvent, and -of the substances held in solution: to have the proportion of their -_bulks_, we may suppose the specific gravity of mineral bodies in -general to be to that of water as 5 to 2, and then we have the ratio -of bulks, that of 250 × 5 to 2 × 1, or of 625 to 1. It follows, then, -that minerals in general cannot be supposed soluble in less than 625 -times their bulk of water. - -433. Again, it must be allowed to the Neptunists, that the fluidity -of the whole earth is not necessary to account for its assuming the -spheroidal figure. It is sufficient if the whole of that crust or shell -of matter was fluid, which is contained between the actual surface -of the terrestrial spheroid, and the surface of the sphere inscribed -within it; that is, of the sphere which has for its diameter the polar -axis of the earth. The whole of the minerals which compose this shell, -must at least have been dissolved in water, and have formed the chaotic -mass of Mr Kirwan. The volume of the water required for this was not -less than 625 times the bulk of the spheroidal shell that has just been -mentioned. - -But, assuming the difference between the polar axis and the equatorial -diameter to be 1/300 of the latter, which is the supposition most -agreeable to the phenomena, it is easy to show that the magnitude of -the above spheroidal shell, or the difference between the solid content -of the earth, and the sphere inscribed in it, is greater than 1/151 and -less than 1/150 of the whole earth; so that the earth is less than 151 -times the spheroidal shell. - -The volume of the water, therefore, necessary to hold in solution the -materials of this shell, is to the volume of the whole earth as 625 -to 151, or in a greater ratio than that of four to one: and such, -therefore, at the very least, is the quantity of water which Mr Kirwan -supposes, after it ceased to act in its chemical capacity, to have -retired into caverns in the interior of the earth. Thus the Neptunists, -in their account of the spheroidal figure of the earth, are reduced -to a cruel dilemma, and are forced to choose between a physical and a -mathematical impossibility. - -If we would inquire whether the opinion of the igneous origin of -minerals, as commonly received by the Vulcanists, is capable of -affording a better solution of this difficulty, the theory of M. de -Buffon is the first that presents itself. - -434. That philosopher considers the existence of the spheroidal figure -as a proof that the whole of the earth must have been originally fluid; -and as the fluidity of the whole can only be ascribed to fusion, he has -supposed that the earth was originally a mass of melted matter struck -off from the sun by the collision of a comet; and that this mass, when -made to revolve on its axis, put on a spheroidal figure, which it has -retained, though now cooled down to congelation. - -This system need not be considered in detail; the foundation of it is -laid in such defiance of the principles of geometry and mechanics, that -the architect, notwithstanding all the fertility of his invention, and -all the resources of his genius, was never able to give any solidity to -the structure. - -But it will be said, that we may take a part of the system, without -venturing on the whole, and may suppose that the earth, or at least -the external crust of it, has been fluid by fire, though we do not -inquire into the cause of this fire, or into the manner in which it was -produced. - -It is indeed true, that, when this is done, we have not the same sort -of absurdity to encounter that we met with in the Neptunian system, and -that the Volcanic theory does not, like it, come into direct collision -with an axiom of geometry. There are, nevertheless, great objections -to it; for though all the phenomena of the mineral kingdom attest a -fluidity of igneous origin, yet it is a fluidity that was never more -than partial; and though it has been over all the earth, has been over -it in succession only. Besides, we are not entitled to assume the -existence, and again the disappearance of such a great quantity of -heat, without assigning some cause for the change. - -435. Since, then, neither the hypothesis of the Neptunists or the -Vulcanists, affords any good explanation of the figure of the earth, or -such a one as can connect it with the other appearances in its natural -history, it remains to inquire, whether the system that supposes a -partial and successive fluidity, like Dr Hutton's, has any resource for -explaining this great phenomenon. - -Of this subject Dr Hutton has not treated; and when I was first made -acquainted with his system, it appeared to me a very serious objection -to it, that it did not profess to give an explanation of so important -a fact as the oblate figure of the earth. On considering the matter -more closely, however, I found that there were principles contained -in it from which a very satisfactory solution (and, I think, the only -satisfactory solution) of that difficulty might be deduced. This -solution I shall endeavour to explain, in as far, at least, as is -necessary for the purpose of general illustration. - -It is laid down in Dr Hutton's theory, that the surface of the earth is -perpetually changed by the _detritus_ of the land; and that from the -materials thus afforded, new horizontal strata are perpetually formed -at the bottom of the sea. If this be true, and if the alternations of -decay and renovation have been often repeated, it is certain, that the -figure of the earth, whatever it may have originally been, must be -brought at length to coincide with the spheroid of equilibrium. - -436. Here it is necessary to remark, that the expressions, _figure of -the earth_, and _surface of the earth_ are each of them occasionally -taken in two different senses. - -The surface of the earth, in its most obvious sense, is that which -bounds the whole earth, and includes all its inequalities; it is a -surface extremely irregular, rising to the tops of the mountains, -descending to the bottoms of the valleys, and having the continuity -of its curvature often interrupted, or suddenly changed. This may be -called the _actual_ surface, and the figure bounded by it, the _actual_ -figure, of the earth. - -The surface of the earth, in another sense, is one that is every where -horizontal, and is the same which water assumes when at rest. - -This superficies is determined by the circumstance of its being -constantly perpendicular to the direction of gravity; it is the surface -marked out by levelling, and may be supposed to be continued from the -sea, through the interior of the land, till it meet the sea again. The -figure bounded by this horizontal surface, may properly be called the -_statical_ figure of the earth. - -When it is said that the figure of the earth is an oblate spheroid, it -is the statical, not the actual figure which is meant; and the degrees -of the meridian which astronomers measure, are also referred to the -superficies of the former. - -437. Suppose now a body like the earth, but with its actual figure -infinitely more irregular, having a sea circumfused around it, the -water will descend into the lowest situations, and will so arrange -itself, that its surface shall be perpendicular every where to the -plumb-line, or to the direction of gravity, in which state only it can -remain at rest. The figure of the superficies which the sea must thus -take will be of a continuous curvature, and will return into itself; -though it may, if the actual figure is very irregular, be far either -from a sphere or a spheroid. If, however, we suppose the solid parts -of this mass subject to be dissolved or worn away, and carried down to -the ocean, there will be a tendency to give to the whole body the same -figure that it would have assumed, if it had been entirely fluid, and -subject to the laws of hydrostatics. This tendency is the result of -two principles. - -438. Let us suppose the body just described to have no rotation, so -that the particles of it are actuated only by the forces of cohesion -and of attraction. - -It is then clear, that every particle taken away by attrition from the -parts above the level of the sea, and deposited under the surface of -it, makes the general figure more compact, bringing the remoter parts -nearer to the centre of gravity of the whole; so that, in time, if the -body is homogeneous, all the points of the surface will become equally -distant from that centre. Thus the _actual_ figure changes continually, -and approaches nearer to the _statical_. - -While this change is going forward in the actual figure, there is -another produced on the statical, that tends very much to accelerate -the final coincidence, of the two. - -The effect of the inequalities of the land, that rise above the -horizontal surface, is, by their attraction, to render the parts of -that surface immediately under them, more convex, _cæteris paribus_, -than the rest. Again, where there are parts of extraordinary depth in -the sea, that is, where the solid and denser parts are far removed from -the surface of the ocean, the curvature of the superficies of the sea -is thereby diminished, and that superficies is rendered less convex -than it would be if the sea were shallower. These propositions are both -capable of strict mathematical demonstration. Hence the taking away of -any particle of matter from the top of a mountain tends to diminish the -curvature of the horizontal surface under the mountain, where it is -greatest; and the deposition of the same particle at the bottom of the -sea, tends to increase the curvature of this superficies where it is -least. The general tendency, therefore, being to increase the curvature -where it is least, and to diminish it where it is greatest, must be -to bring about an uniform curvature throughout, that is, a spherical -figure. Thus, by the waste and subsequent stratification of the land, -the direction of gravity is continually altered; it is more and more -concentrated, and the figure brought nearer to that which a fluid would -assume. - -439. If now we suppose the body to revolve on its axis, all other -things remaining as before, the surface bounding the sea will become -different from what it was in the former case, and will be more swelled -out toward the middle or equatorial regions. The land above the level -of the sea will still, as before, be worn down and deposited in the -bottom of the sea, so as to form strata nearly parallel to its surface: -the tendency, therefore, is to render the real figure of the planet -nearer to the statical. At the same time the _statical_ figure is -changed, as explained above; so that the two figures mutually approach, -and the limit, or ultimate figure to which they tend, is one over which -the ocean might be diffused every where to the same depth, for then the -causes of change would entirely cease. But this figure is no other than -the spheroid of equilibrium, which, therefore, is the effect which the -waste and reconsolidation of the land would necessarily produce, if the -process were continued indefinitely, without interruption. In this, as -in many other instances, when a body is subject to the action of causes -by which its form is _gradually_ changed, the figure best adapted -to resist those changes, is the figure which the changes themselves -ultimately produce. - -Also, whatever be the irregularities of density, the tendency to a -change of figure will not cease till the body is moulded into that -particular spheroid which admits of being covered with water every -where to the same depth.[232] Thus it appears, that a solid of an -irregular figure, and of irregular density, provided it be in part -covered with water; and be at the same time subject to waste above the -surface of the sea, and reconsolidation under it, has a tendency to -acquire, in time, the same figure that it would have acquired had it -been entirely fluid. - -[Footnote 232: In the same manner as a transition is thus made from an -irregular figure to a spheroid of equilibrium, so, if the actual figure -were at first more simple than the spheroid, it would still be changed -into this last by degrees. - -Let us conceive, for instance, that the earth is at rest, and is a -perfect sphere of solid matter, surrounded by an ocean every where of -equal depth, for example, of one mile. Then, if a rotatory motion be -communicated to it, so that it shall revolve on its axis in twenty-four -hours, in consequence of the centrifugal force, the water circumfused -about the sphere will immediately rise up under the equator, and will -become part of a spheroidal surface, (not elliptical, but nearly so,) -the equatorial diameter of which is greater than the polar axis, in the -ratio of 588 to 577 By this means the water will be accumulated at the -equator to the depth of nearly 2.5 miles, and form a zone surrounding -the earth, and extending about 37° on each side of the equator. The -remainder of the surface will be left dry, forming two vast circumpolar -continents, that reach 53° on every side of the poles, and that are -elevated in the middle more than four miles above the level of the sea. - -Such would be the state of our globe, on the hypothesis above laid -down; and, if there were no waste or destruction of the land, this -order of things would be permanent, and neither the solid nor fluid -part of the mass could ever acquire any other figure than that which -has been described. But, if the same laws be supposed to regulate the -action of the atmosphere in those circumstances, that do actually -regulate it according to the present constitution of the globe, the -vapours raised up from the surface of the sea, would be carried by the -winds over the land, where they would be condensed and precipitated in -rain. Thus, all the agents of destruction would be let loose on the two -great circumpolar continents; rivers would be formed; the land would -become deeply intersected by ravines; those ravines would gradually -open into wide valleys; the masses of greatest resistance would be -shaped into hills and mountains: and from a superficies originally -smooth and uniform, the same inequalities would be produced which at -present diversify the surface of the earth. - -While the parts of the sphere without the spheroid are thus continually -diminished, the loose earth and sand washed down from them, will be -deposited at the bottom of the sea, and will form strata parallel -to the surface of the superincumbent water. The actual and statical -figure are thus brought nearer one another; and, at the same time the -statical is changed, on the principle already explained, (the change in -the direction of gravity,) and is made continually to approximate to a -state, which when it has attained, no farther change can take place, -viz. an oblate elliptic spheroid, of which the surface is perpendicular -to the direction of gravity, having the equatorial diameter to the -polar axis in the ratio of 230 to 229.] - -440. In the preceding reasonings, we have supposed the process of decay -and subsequent stratification to be carried on without interruption, -till the whole of the land is covered by the sea. This supposition is -useful for explaining the nature of the forces which have determined -the figure of the earth; but there is no reason to think that it has -ever been realized in its full extent, the elevation of strata from the -bottom of the sea interrupting the progress, and producing new land -in one place, as the old decays in another. The very same land also, -which is wasted at its surface, may perhaps be lifted up by the forces -that are placed under it; or it may be let down, undergoing alterations -of its level, from causes that we do not perceive, but of which the -action is undoubted, (§ 388.) But notwithstanding these interruptions, -the general tendency to produce in the earth a spheroidal figure may -remain, and more may be done by every revolution, to bring about the -attainment of that figure than to cause a deviation from it. This -figure, therefore, though never likely to be perfectly acquired, will -be the _limiting_ or _asymptotic_ figure, if it may be so called, to -which the earth will continually approach. - -441. If the preceding conclusions are just, and if the figure of -equilibrium is only an asymptotic figure, to which that of the earth -may approximate, but cannot perfectly attain, we are not to be -surprised if considerable deviations from it are actually observed. -This has accordingly happened, insomuch, that the results deduced from -the most accurate measurement of degrees of the meridian, differ from -one another, in the oblateness they give to the earth, by nearly one -half of the quantity to be determined. When we compare the degrees -measured in France, and in some other countries of Europe, with -those measured in Peru, we obtain for the compression at the poles, -less than 1/300 of the radius of the earth. But when we compare the -degrees measured in France with one another, and with those lately -measured in England, we find that they are best represented by a -spheroid that has its compression 1/150 of its semi-axis.[233] There -is reason to think, therefore, that the meridians are not elliptical; -and other observations seem to show, that they are not even similar -to one another; or that the earth is not, strictly speaking, a solid -of revolution; so, also, the comparison of the degree measured at -the Cape of Good Hope, with those measured on the opposite side of -the equator, creates a suspicion, that the northern and southern -hemispheres are not perfectly alike, and that the earth is not equally -compressed at the Arctic and the Antarctic poles. These irregularities, -though they do not affect the general fact of the earth's compression -at the poles, show that the true statical figure is but imperfectly -attained; and though this may be accounted for, without having recourse -to the principles involved in our theory, it is in a manner very -unsatisfactory, and, by help of suppositions, not at all consistent -with the original fluidity ascribed to the whole mass, or to the -exterior crust of the earth. - -[Footnote 233: Exposition du Systéme du Monde, par La Place, p. 61, 2d -edit.] - -442. As the principles here laid down explain how a solid body may -attain very nearly the figure which a fluid would acquire in order to -preserve its parts in equilibrium; and since the oblate figure belongs -to other of the planets as well as the earth, and the globular to all -the great bodies of the universe, this suggests an analogy that goes -deep into the economy of nature, and extends far beyond the limits -within which the mineralogist is wont to confine his speculations. - -443. That no very irregular figure is found among the planetary bodies, -may therefore be considered as a proof of the universality of that -system of waste and reconsolidation that we have been endeavouring to -trace in the natural history of the earth. A farther proof of the same -arises from considering, that for every given mass of matter, having a -given period of rotation, there are two different spheroids that answer -the conditions of establishing an equilibrium among its parts, the one -near to the sphere, and the other very distant from it, and so oblate -as to have a lenticular form. Thus the earth, supposing it homogeneous, -might either be in equilibrium, by means of the figure which it -actually has, or of one in which the polar was to the equatorial -diameter as 1 to 768. The same is true of the other planets; and yet we -no where find that this highly compressed spheroid is actually employed -by nature. The reason, no doubt, is, that in so oblate a spheroid, the -equilibrium between the gravitating and the centrifugal force is of -the kind that does not re-establish itself when disturbed; so that the -parts let loose, and not kept in their place by firm cohesion, would -fly off altogether. In such a body, the waste at the surface would -lead to an entire change of form, and therefore the constitution here -supposed could not be permanent. - -444. In the system of Saturn, we have a great deviation from the -general order, which, nevertheless, has led to a very unexpected -verification of some of the conclusions deduced above. A principle -extremely like that which is the basis of all the foregoing reasonings, -led one of the greatest philosophers of the present age to discover -the revolution of Saturn's ring on its axis, and even to determine -the velocity of that revolution, such as it has been since found by -observation. LA PLACE, laying it down as a maxim, that nothing in -nature can exist, where there are causes of change, not balanced or -compensated by other causes,[234] concluded, that the-parts of the -ring must be held from falling down to the body of the planet by some -other force than their mere cohesion to one another. Were it otherwise, -every particle detached from the ring, by any means, must descend in a -straight line, almost perpendicular to the surface of Saturn; and the -final destruction of the ring must be inevitable. The only force that -could balance this effect of gravitation, seemed to be a centrifugal -force, arising from the rotation of the ring on an axis passing through -its centre, and perpendicular to its plane. La Place proceeded to -inquire what celerity of rotation was adequate to this effect, and -found that one of ten hours and a quarter would be required, which -is almost precisely the time afterwards determined by Dr HERSCHEL -from actual observation. If, with this rotation, the ring is a solid -annulus generated by the rotation of a very flat ellipsis about a given -point in its greater axis, coinciding with the centre of Saturn, it may -be so constituted, that the attraction of Saturn, combined with the -centrifugal force, may produce a force perpendicular to its surface, -and may enable detached parts to remain at rest, animals, for instance, -to walk on its surface, and fluids to be _in equilibrio_. The system of -Saturn is thus fortified against the lapse of time, as effectually as -that of the earth itself; and the means by which this is accomplished, -seem to prove, that the weapons which time employs, are in both cases -the same, viz. the slow wearing and decomposition of the solid parts. -This slow wearing may have produced the figure by which its action is -most effectually resisted. - -[Footnote 234: La Place, _ubi supra_, p. 242.] - -445. Thus Dr Hutton's theory of the earth comes at last to connect -itself with the researches of physical astronomy. The conclusion to be -drawn from this coincidence is to the credit of both sciences. When two -travellers, who set out from points so distant as the mineralogist and -the astronomer, and who follow routes so different, meet at the end of -their journey, and agree in their report of the countries through which -they have passed, it affords no slight presumption, that they have kept -the right way, and that they relate what they have actually seen. - - - - - NOTE XXVI. § 133. - - _Prejudices relating to - the Theory of the Earth._ - - -446. Among the prejudices which a new theory of the earth has to -overcome, is an opinion, held, or affected to be held, by many, that -geological science is not yet ripe for such elevated and difficult -speculations. They would, therefore, get rid of these speculations, _by -moving the previous question_, and declaring that at present we ought -to have no theory at all. We are not yet, they allege, sufficiently -acquainted with the phenomena of geology; the subject is so various and -extensive that our knowledge of it must for a long time, perhaps for -ever, remain extremely imperfect. And hence it is, that the theories -hitherto proposed have succeeded one another with so great rapidity, -hardly any of them having been able to last longer than the discovery -of a new fact, or a fact unknown when it was invented. It has proved -insufficient to connect this fact with the phenomena already known, and -has therefore been justly abandoned. In this manner, they say, have -passed away the theories of Woodward, Burnet, Whiston, and even of -Buffon; and so will pass, in their turn, those of Hutton and Werner. - -447. This unfavourable view of geology, ought not, however, to be -received without examination; in science, presumption is less hurtful -than despair, and inactivity is more dangerous than error. - -One reason of the rapid succession of geological theories, is the -mistake that has been made as to their object, and the folly of -attempting to explain by them the first origin of things. This mistake -has led to fanciful speculations that had nothing but their novelty to -recommend them, and which, when that charm had ceased, were rejected -as mere suppositions, incapable of proof. But if it is once settled, -that a theory of the earth ought to have no other aim but to discover -the laws that regulate the changes on the surface, or in the interior -of the globe, the subject is brought within the sphere either of -observation or analogy; and there is no reason to suppose, that man, -who has numbered the stars, and measured their forces, shall ultimately -prove unequal to this investigation. - -448. Again, theories that have a rational object, though they be false -or imperfect in their principles, are for the most part approximations -to the truth, suited to the information at the time when they were -proposed. They are steps, therefore, in the advancement of knowledge, -and are terms of a series that must end when the real laws of nature -are discovered. It is, on this account, rash to conclude, that in the -revolutions of science, what has happened must continue to happen, -and because systems have changed rapidly in time past, that they must -necessarily do so in time to come. - -He who would have reasoned so, and who had seen the ancient physical -systems, at first all rivals to one another, and then swallowed up by -the Aristotelian; the Aristotelian physics giving way to those of Des -Cartes; and the physics of Des Cartes to those of Newton; would have -predicted that these last were also, in their turn, to give place to -the philosophy of some later period. This is, however, a conclusion -that hardly any one will now be bold enough to maintain, after a -hundred years of the most scrupulous examination have done nothing -but add to the evidence of the NEWTONIAN SYSTEM. It seems certain, -therefore, that the rise and fall of theories in times past, does not -argue, that the same will happen in the time that is to come. - -449. The multifarious and extremely diversified object of geological -researches, does, no doubt, render the first steps difficult, and -may very well account for the instability hitherto observed in such -theories; but the very same thing gives reason for expecting a very -high degree of certainty to be ultimately attained in these inquiries. - - -Where the phenomena are few and simple, there may be several different -theories that will explain them in a manner equally satisfactory; -and in such cases, the true and the false hypotheses are not easily -distinguished from one another. When, on the other hand, the phenomena -are greatly varied, the probability is, that among them, some of -those _instantiæ crucis_ will be found, that exclude every hypothesis -but one, and reduce the explanation given to the highest degree of -certainty. It was thus, when the phenomena of the heavens were but -imperfectly known, and were confined to a few general and simple facts, -that the Philolaic could claim no preference to the Ptolemaic system: -The former seemed a possible hypothesis; but as it performed nothing -that the other did not perform, and was inconsistent with some of our -most natural prejudices, it had but few adherents. The invention of the -telescope, and the use of more accurate instruments, by multiplying -and diversifying the facts, established its credit; and when not only -the general laws, but also the inequalities, and disturbances of the -planetary motions were understood, all physical hypotheses vanished, -like phantoms, before the philosophy of NEWTON. Hence the number, the -variety, and even the complication of facts, contribute ultimately to -separate truth from falsehood; and the same causes which, in any case, -render the first attempts toward a theory difficult, make the final -success of such attempts just so much the more probable. - -This maxim, however, though a general encouragement to the prosecution -of geological inquiries, does not amount to a proof that we are yet -arrived at the period when those inquiries may safely assume the form -of a theory. But that we are arrived at such a period, appears clear -from other circumstances. - -450. It cannot be denied, that a great multitude of facts, respecting -the mineral kingdom, are now known with considerable precision; and -that the many diligent and skilful observers, who have arisen in the -course of the last thirty years, have produced a great change in the -state of geological knowledge. It is unnecessary to enumerate them -all; FERBER, BERGMAN, DE LUC, SAUSSURE, DOLOMIEU, are those on whom -Dr Hutton chiefly relied; and it is on their observations and his own -that his system is founded. If it be said, that only a small part of -the earth's surface has yet been surveyed, and described with such -accuracy as is found in the writers just named, it may be answered, -that the earth is constructed with such a degree of uniformity, that a -tract of no very large extent may afford instances of all the leading -facts that we can ever observe in the mineral kingdom. The variety of -geological appearances which a traveller meets with, is not at all in -proportion to the extent of country he traverses; and if he take in a -portion of land sufficient to include primitive and secondary strata, -together with mountains, rivers, and plains, and unstratified bodies in -veins and in masses, though it be not a very large part of the earth's -surface, he may find examples of all the most important facts in the -history of fossils. Though the labours of mineralogists have embraced -but a small part of the globe, they may therefore have comprehended a -very large proportion of the phenomena which it exhibits; and hence a -presumption arises, that the outlines, at least, of geology have now -been traced with tolerable truth, and are not susceptible of great -variation. - -451. When the phenomena of any class are in general ambiguous, and -admit of being explained by different or even opposite theories; if few -of those exclusive facts are known, which admit but of one or a few -solutions, then we have no right to expect much from our endeavours to -generalise, except the knowledge of the points where our information -is most deficient, and to which our observations ought chiefly to be -directed. But that many of the exclusive and unambiguous instances are -known, in the natural history of the globe, I think is evident from the -reasoning in the foregoing pages, where so many examples have occurred -of appearances that give the most direct negative to the Neptunian -system, and exclude it from the number of possible hypotheses, by -which the phenomena of geology can be explained. The abundance of such -instances is an infallible sign, that the mass of knowledge is in that -state of fermentation, from which the true theory may be expected to -emerge. - -452. Another indication of the same kind, is the near approach that -even the most opposite theories make, in some respects, to one another. -There are so many points of contact between them, that they appear -to approximate to an ultimate state, in which, however unwillingly, -they must at last coincide. That ultimate form, too, which all these -theories have a tendency to put on, if I am not deceived, is no other -than that of the Huttonian theory. - -453. The first example I shall take from the system of Saussure. It -is to be regretted, that this excellent geologist has no where given -us a complete account of his theory. Some of the leading principles -of it are, however, unfolded in the course of his observations, and -enable us to form a notion of its general outline. It was evidently far -removed from the system of subterraneous heat, and seems, especially -in the latter part of the author's life, to have been very much -accommodated to the prevailing system of WERNER. Nevertheless, with -so little affinity between their general views, Saussure and Hutton -agree in that most important article which regards the elevation of -the strata. Saussure plainly perceived the impossibility of the strata -being formed in the vertical situations which so many of them now -occupy; and he takes great pains to demonstrate this impossibility, -from some facts that have been referred to above. He also believed that -this elevation had been given to strata that were originally level, by -a force directed upwards, or by the _refoulement_ of the beds, not by -their falling in, as is the opinion of De Luc and some other of the -Neptunists. - -Now, whoever admits this principle, and reasons on it consistently, -without being afraid to follow it through all its consequences, must -unavoidably come very close to the Huttonian theory. He must see, -that a power which, acting from below, produced this great effect -can never have belonged to water, unless rarefied into steam by the -application of heat. But if it be once admitted that heat resides in -the mineral regions, the great objection to Dr Hutton's system is -removed; and the theorist, who was furnished with so active and so -powerful an agent, would be very unskilful in the management of his -own resources, if he did not employ it in the work of consolidating as -well as in that of raising up the strata. A little attention will show, -that it is qualified for both purposes; though insuperable objections -must, no doubt, offer themselves, where the effects of compression -are not understood. We may safely conclude, then, that the accurate -and ingenious Geologist of Geneva ought to have been a _Plutonist_, -in order to give consistency to the principles which he had adopted, -and to make them coalesce as parts of one and the same system. If he -embraced an opposite opinion, it probably was from feeling the force of -those objections that arise from our discovering nothing in the bowels -of the earth like the remains left by combustion, or inflammation, at -its surface. The secret by which these seeming contradictions are to be -reconciled, was unknown to this mineralogist, and he has accordingly -decided strongly against the action of fire, even in the case of those -unstratified substances that have the greatest affinity to volcanic -lava. - -454. The theoretical conclusions of another accurate and skilful -observer, Dolomieu, furnish a still more remarkable example of a -tendency to union between systems professedly hostile to one another. - -This ingenious mineralogist, observing the interposition of the basalt -between stratified rocks, so that it had not only regular beds of -sandstone for its base, but was also covered with beds of the same -kind, saw plainly that these appearances were inconsistent with the -supposition of common volcanic explosions at the surface. He therefore -conceived, that the volcanic eruption had happened at the bottom of -the sea, (the level of which, in former ages, had been much higher -than at present,) and that the materials afterwards deposited on the -lava, had been in length of time consolidated into beds of stone. It -is evident, that this notion of submarine volcanoes, comes very near, -in many respects, to Dr Hutton's explanation of the same appearances. -If the only thing to be accounted for were the phenomenon in question, -it cannot be denied that Dolomieu's hypothesis would be perfectly -sufficient; but Dr Hutton, to whom this phenomenon was familiar, and -who, like Dolomieu, conceived the basalt to have been in fusion, was -convinced that the retreat of the sea was not a fact well attested by -geological appearances, and if admitted, was inadequate to account for -the facts usually explained by it. He conceived, therefore, that such -lava as the preceding had flowed not only at the bottom of the sea, -but in the bowels of the earth, and having been forced up through the -fissures of rocks already formed, had heaved up some of these rocks, -and interposed itself between them. This agrees with the other facts in -the natural history both of the basaltes and the strata. - -It is plain, that, in this, there is a great approach of the two -theories to one another: both maintain the igneous origin of basaltes, -and its affinity to lava; both acknowledge that this lava cannot have -flowed at the surface, and that the strata which cover it have been -formed at the bottom of the sea. They only differ as to the mode in -which the submarine or subterraneous volcano produced its effect, and -that difference arises merely from the one geologist having generalized -more than the other. Dolomieu sought to connect the basalt with the -lavas that proceed from volcanic explosions at the surface; Dr Hutton -sought not only to connect these two appearances with one another, but -also with the other phenomena of mineralogy, particularly with the -veins of basaltes, and the elevation of the strata. - -455. In another point, the coincidence of Dolomieu's opinions and Dr -Hutton's is still more striking. The former has remarked, that many -of the extinguished volcanoes are in granite countries, and that, -nevertheless, the lavas that they have erupted contain no granitic -stones. There must be, therefore, says he, something under the granite, -and this last is not, at least in all cases, to be considered as the -basis of the mineral kingdom, or as the body on which all others rest. -In this system, therefore, granite is not always a primordial rock, any -more than in Dr Hutton's. - -But Dolomieu makes a still nearer advance to the Huttonian theory; for -he supposes, that under the solid and hard crust of the globe, there is -a sphere of melted stone, from which this basaltic lava was thrown up. -The system of subterraneous heat is here adopted in its utmost extent, -and in that form which is considered as the most liable to objection, -viz. the existence of it at the present moment, in such a degree as to -melt rocks, and keep them in a state of fusion. In this conclusion, the -two theories agree perfectly; and if they do so, it is only because -the nature of things has forced them into union, notwithstanding the -dissimilitude of their fundamental principles. - -This ought to be considered as a strong proof, that the phenomena -known to mineralogists are sufficient to justify the attempts to form -a theory of the earth, and are such as lead to the same conclusions, -where there was not only no previous concert, but even a very marked -opposition. I have already observed, that there is a greater tendency -to agree among geological theories, than among the authors of those -theories. - -456. Another circumstance worthy of consideration is, that in the -search which the Neptunists have made, for facts most favourable to the -aqueous formation of minerals, we find hardly any of a kind that was -unknown to the author of the system here explained. The appearances on -which WERNER grounds his opinion with respect to basaltes, and by which -he would exclude the action of fire from any share in the formation of -it, are all comprehended in the alternation of that rock with beds, or -strata obviously of aqueous origin. Now these appearances were well -known to Dr Hutton, and are easily explained by his theory, provided -the effects of compression are admitted. From this, and the other -circumstances just observed, I am disposed to think, that the great -facts on which every geological system must depend, are now known, and -that it is not too bold an anticipation to say, that a theory of the -earth, which explains all the phenomena with which we are at present -acquainted, will be found to explain all those that remain to be -discovered. - -457. The time indeed was, and we are not yet far removed from it, -when one of the most important principles involved in Dr Hutton's -theory was not only unknown, but could not be discovered. This was -before the causticity produced in limestone by exposure to fire was -understood, and when it was not known that it arose from the expulsion -of a certain aerial fluid, which before was a component part of the -stone. It could not then be perceived, that this aerial part might be -retained by pressure, even in spite of the action of fire, and that in -a region where great compression existed, the absence of causticity was -no proof that great heat had not been applied. The discoveries of Dr -BLACK, therefore, mark an era, before which men were not qualified to -judge of the nature of the powers that had acted in the consolidation -of mineral substances. Those discoveries were, indeed, destined to -produce a memorable change in chemistry, and in all the branches of -knowledge allied to it; and have been the foundation of that brilliant -progress, by which a collection of practical rules, and of insulated -facts, has in a few years risen to the rank of a very perfect science. -But even before they had explained the nature of carbonic gas, and its -affinity to calcareous earth, I am not sure but that Dr Hutton's theory -was, at least, partly formed, though it must certainly have remained, -even in his own opinion, exposed to great difficulties. His active and -penetrating genius soon perceived, in the experiments of his friend, -the solution of those difficulties, and formed that happy combination -of principles, which has enabled him to explain the most enigmatical -appearances in the natural history of the earth. - -As we are not yet far removed from the time when our chemical knowledge -was too imperfect to admit of a satisfactory explanation of the -phenomena of mineralogy, so it is not unlikely that we are approaching -to other discoveries that are to throw new light on this science. It -would, however, be to argue strangely to say, that we must wait till -those discoveries are made before we begin any theoretical reasonings. -If this rule were followed, we should not know where the imperfections -of our science lay, nor when the remedies were found out, should we -be in a condition to avail ourselves of them. Such conduct would not -be caution, but timidity, and an excess of prudence fatal to all -philosophical inquiry. - -458. The truth, indeed, is, that in physical inquiries, the work of -theory and observation must go hand in hand, and ought to be carried -on at the same time, more especially if the matter is very complicated, -for there the clue of theory is necessary to direct the observer. -Though a man may begin to observe without any hypothesis, he cannot -continue long without seeing some general conclusion arise; and to this -nascent theory it is his business to attend, because, by seeking either -to verify or to disprove it, he is led to new experiments, or new -observations. He is led also to the very experiments and observations -that are of the greatest importance, namely, to those _instantiæ -crucis_, which are the _criteria_ that naturally present themselves -for the trial of every hypothesis. He is conducted to the places where -the transitions of nature are most perceptible, and where the absence -of former, or the presence of new circumstances, excludes the action -of imaginary causes. By this correction of his first opinion, a new -approximation is made to the truth; and by the repetition of the same -process, certainty is finally obtained. Thus theory and observation -mutually assist one another; and the spirit of system, against which -there are so many and such just complaints, appears, nevertheless, as -the animating principle of inductive investigation. The business of -sound philosophy is not to extinguish this spirit, but to restrain and -direct its efforts. - -459. It is therefore hurtful to the progress of physical science to -represent observation and theory as standing opposed to one another. -Bergman has said, "Observationes veras quàm ingeniosissimas fictiones -sequi præstat; naturæ mysteria potius indagare quàm divinare." - -If it is meant by this merely to say, that it is better to have facts -without theory, than theory without facts, and that it is wiser to -inquire into the secrets of nature, than to guess at them, the truth -of the maxim will hardly be controverted. But if we are to understand -by it, as some may perhaps have done, that all theory is mere fiction, -and that the only alternative a philosopher has, is to devote himself -to the study of facts unconnected by theory, or of theory unsupported -by facts, the maxim is as far from the truth, as I am convinced it is -from the real sense of Bergman. Such an opposition between the business -of the theorist and the observer, can only occur when the speculations -of the former are vague and indistinct, and cannot be so embodied as to -become visible to the latter. But the philosopher who has ascended to -his theory by a regular generalization of facts, and who descends from -it again by drawing such palpable conclusions as may be compared with -experience, furnishes the infallible means of distinguishing between -_perfect science_ and _ingenious fiction_. Of a geological theory that -has stood this double test of the analytic and synthetic methods, Dr -Hutton has furnished us with an excellent instance, in his explanation -of granite. The appearances which he observed in that stone led him to -conclude, that it had been melted, and injected while fluid, among the -stratified rocks already formed. He then considered, that if this is -true, veins of granite must often run from the larger masses of that -stone, and penetrate the strata in various directions; and this must -be visible at those places where these different kinds of rock come -into contact with one another. This led him to search in Arran and -Glentilt for the phenomena in question; the result, as we have seen, -afforded to his theory the fullest confirmation, and to himself the -high satisfaction which must ever accompany the success of candid and -judicious inquiry. - -460. It cannot, however, be denied, that the impartiality of an -observer may often be affected by system; but this is a misfortune -against which the want of theory is not always a complete security. -The partialities in favour of opinions are not more dangerous than -the prejudices against them; for such is the spirit of system, and so -naturally do all men's notions tend to reduce themselves into some -regular form, that the very belief that there can be no theory, becomes -a theory itself, and may have no inconsiderable sway over the mind -of an observer. Besides, one man may have as much delight in pulling -down, as another has in building up, and may choose to display his -dexterity in the one occupation as well as in the other. The want -of theory, then, does not secure the candour of an observer, and it -may very much diminish his skill. The discipline that seems best -calculated to promote both, is a thorough knowledge of the methods of -inductive investigation; an acquaintance with the history of physical -discovery; and the careful study of those sciences in which the rules -of philosophising have been most successfully applied. - - - FINIS. - - - * * * * * - - -Transcriber Note - -Minor typos corrected. Some differences in application of accents and -formatting were left as printed. - - - - -*** END OF THE PROJECT GUTENBERG EBOOK ILLUSTRATIONS OF THE HUTTONIAN -THEORY OF THE EARTH *** - -Updated editions will replace the previous one--the old editions will -be renamed. - -Creating the works from print editions not protected by U.S. copyright -law means that no one owns a United States copyright in these works, -so the Foundation (and you!) can copy and distribute it in the -United States without permission and without paying copyright -royalties. 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You may copy it, give it away or re-use it under the terms -of the Project Gutenberg License included with this eBook or online -at <a href="https://www.gutenberg.org">www.gutenberg.org</a>. If you -are not located in the United States, you will have to check the laws of the -country where you are located before using this eBook. -</div> - -<p style='display:block; margin-top:1em; margin-bottom:1em; margin-left:2em; text-indent:-2em'>Title: Illustrations of the Huttonian Theory of the Earth</p> -<p style='display:block; margin-top:1em; margin-bottom:0; margin-left:2em; text-indent:-2em'>Author: John Playfair</p> -<p style='display:block; text-indent:0; margin:1em 0'>Release Date: February 6, 2022 [eBook #67331]</p> -<p style='display:block; text-indent:0; margin:1em 0'>Language: English</p> - <p style='display:block; margin-top:1em; margin-bottom:0; margin-left:2em; text-indent:-2em; text-align:left'>Produced by: Tom Cosmas produced from materials made available at The Internet Archive and placed in the Public Domain.</p> -<div style='margin-top:2em; margin-bottom:4em'>*** START OF THE PROJECT GUTENBERG EBOOK ILLUSTRATIONS OF THE HUTTONIAN THEORY OF THE EARTH ***</div> - - - - - - - -<div class="pmt4 transnote"> -<p class="caption3nb">Transcriber Note</p> - -<p>Since <a href="#sec_134">§ 134</a> appeared on page 143 and again on page 147, the Section -number on <a href="#sec_135">pages 147</a> and all succeeding were incremented. The Table of -Contents was also incremented respectively. List of ERRATA below has been applied to the text.</p> - -<p class="caption4nb">ERRATA.</p> - -<table summary="errata"> -<tr> - <td class="tdc">Page</td> - <td class="tdr">44.</td> - <td class="tdc">line</td> - <td class="tdr">4.</td> - <td class="tdc">from the bottom,</td> - <td class="tdc"><i>for</i></td> - <td class="tdc">that</td> - <td class="tdc"><i>read</i></td> - <td class="tdc">as</td> -</tr> -<tr> - <td class="tdc">"</td> - <td class="tdr">189.</td> - <td class="tdc">"</td> - <td class="tdr">6.</td> - <td class="tdc">"</td> - <td class="tdc"><i>for</i></td> - <td class="tdc">appearenes</td> - <td class="tdc"><i>read</i></td> - <td class="tdc">appearances</td> -</tr> -<tr> - <td class="tdc">"</td> - <td class="tdr">464.</td> - <td class="tdc">"</td> - <td class="tdr">4.</td> - <td class="tdc">"</td> - <td class="tdc"><i>for</i></td> - <td class="tdc"><span class="smcap">D'Aubenton</span></td> - <td class="tdc"><i>read</i></td> - <td class="tdc"><span class="smcap">Daubenton</span></td> -</tr> -<tr> - <td class="tdc">"</td> - <td class="tdr">482.</td> - <td class="tdc">"</td> - <td class="tdr">12.</td> - <td class="tdc">"</td> - <td class="tdc"><i>for</i></td> - <td class="tdc">adversaries</td> - <td class="tdc"><i>read</i></td> - <td class="tdc">adversary</td> -</tr> -</table> -</div> - -<div class="figcenter" id="cover" style="width: 231px;"> - <img src="images/cover.png" width="231" height="313" alt="Illustrations of the Huttonian Theory of the Earth, by John Playfair" /> -</div> - - -<p><span class="pagenum" id="Page_i">- i -</span></p> - - - -<h1> -<span class="smaller">ILLUSTRATIONS</span><br /> -<span class="vsmall">OF THE</span><br /> -HUTTONIAN THEORY<br /> -<span class="smaller">OF THE EARTH</span><br /> -</h1> - - -<h2><span class="smcap">By JOHN PLAYFAIR</span></h2> - -<p class="pmb2 tdc"> -<span style="margin-left: 1em;">F. R. S. EDIN. AND PROFESSOR OF MATHEMATICS</span><br /> -<span style="margin-left: 1em;">IN THE UNIVERSITY OF EDINBURGH.</span><br /> -</p> - - -<div class="figcenter" style="width: 400px;"> - <img src="images/bar_double.png" width="400" height="15" alt="" /> - - Nunc naturalem causam quærimus et assiduam,<br /> - non raram et foriuitam.<br /> - -<div class="tdr"> -<span style="margin-left: 1em;"><span class="smcap">Seneca.</span></span><br /> -</div> - - <img src="images/bar_double.png" width="400" height="15" alt="" /> -</div> - - -<p class="pmt2 pmb4 tdc">EDINBURGH:<br /> -<br /> -PRINTED FOR CADELL AND DAVIES, LONDON, AND<br /> -WILLIAM CREECH, EDINBURGH.<br /> -<br /> - <img src="images/bar_double.png" width="80" height="15" alt="" /><br /> -<br /> -1802.</p> - -<p><span class="pagenum" id="Page_ii">- ii -</span></p> - - -<p class="pmt4 pmb4 antiqua tdc">Entered in Stationers Hall.</p> - - -<p> -<span style="margin-left: 3.5em;"><span class="smcap">Neill & Co.</span> }</span><br /> -<span style="margin-left: 2em;">Printers, Edinburgh }</span><br /> -</p> - -<p><span class="pagenum" id="Page_iii">- iii -</span></p> - - - - -<h2>ADVERTISEMENT.</h2> - - -<div class="fl_left"> -<span class="vbig">T</span> -</div> - -<p><span class="hidden">T</span>HE Treatise here offered to the Public, was drawn up with a -view of explaining Dr Hutton's Theory of the Earth in a manner more -popular and perspicuous than is done in his own writings. The obscurity -of these has been often complained of; and thence, no doubt, it has -arisen, that so little attention has been paid to the ingenious and -original speculations which they contain.</p> - -<p><span class="smcap">The</span> simplest way of accomplishing the object proposed, seemed -to be, to present a General Outline of the System, in one continued -Discourse; and to introduce afterwards, in the form of Notes, what -farther elucidation any particular subject was thought to demand. -Through the whole, I have aimed at little more than a clear exposition -of facts, and a plain deduction of the conclusions grounded on them; -nor shall I claim any merit to myself, if, in the order which I have -found it necessary to adopt, some arguments may have taken a -<span class="pagenum" id="Page_iv">- iv -</span> -new form, -and some additions may have been made to a system naturally rich in the -number and variety of its illustrations.</p> - -<p><span class="smcap">Of</span> the qualifications which this undertaking requires, there -is one that I may safely suppose my self to possess. Having been -instructed by Di Hutton himself in his theory of the earth; having -lived in intimate friendship with that excellent man for several years, -and almost in the daily habit of discussing the questions here treated -of; I have had the best opportunity of understanding his views, and -becoming acquainted with his peculiarities, whether of expression or -of thought. In the other qualifications necessary for the illustration -o a system so extensive and various, I am abundantly sensible of my -deficiency, and shall therefore with great deference, and considerable -anxiety wait that decision from which there is no appeal.</p> - -<p> -<span style="margin-left: 2em;"><span class="smcap">Edinburgh College</span>, }</span><br /> -<span style="margin-left: 2.5em;">1st March 1802. }</span><br /> -</p> - - -<hr class="chap x-ebookmaker-drop" /> - -<div class="chapter"> -<p><span class="pagenum" id="Page_v">- v -</span></p> - -<h2 class="nobreak" id="TABLE">TABLE<br /> - -<span class="vsmall">OF</span><br /> - -CONTENTS.<br /> -</h2> -</div> - -<div class="figcenter" style="width: 156px; padding: 48px 0;"> - <img src="images/bar_blob.png" width="156" height="13" alt="" /> -</div> - - -<div class="blockquot"> - -<p>INTRODUCTION. Object of a Theory of the Earth. Division of minerals -into <i>Stratified</i> and <i>Unstratified</i>.</p> -</div> - -<p class="tdr"><a href="#ILLUSTRATIONS">Page 1</a></p> - - -<p class="caption3nb">SECTION I.</p> - -<p class="tdc">PHENOMENA PECULIAR TO STRATIFIED BODIES.</p> - -<p class="tdc2">1. Materials of the Strata.</p> - -<p class="tdr"><a href="#SECTION_I">Page 4</a></p> - -<div class="blockquot"> - -<p>Present strata composed of the remains of more ancient rocks, § 1. -Proofs from calcareous strata, § 2.—from siliceous, § 3.—from -argillaceous, § 4.—from bituminous, § 5, 6. Absence of organized -remains from the strata called <i>primitive</i>, not universally -true, § 8, 9.—Term Primary substituted for Primitive. -Composition from the materials of more ancient rocks, § 10.</p> -</div> - - -<p class="tdc2">2. Consolidation of the Strata.</p> - -<p class="tdr"><a href="#sect1p2">p. 15</a></p> - -<div class="blockquot"> - -<p>Consolidation, what, § 11. Objections to aqueous consolidation, § -12, 13, 14. Compression affects the action of fire on bodies, § -15, 16, 17.—Igneous consolidation of minerals prove from fossil -wood, § 19.—From the flints in chalk, § 20.—from sandstone, -§ 21.—from -<span class="pagenum" id="Page_vi">- vi -</span> -the calcareous strata, § 23, 24, 25.—from the -argillaceous, § 26, 27.—from the bituminous, § 28, 29.—from the -saline, § 32. Salt mines in Cheshire. Trona of Africa, § 54, 35.</p> -</div> - - -<p class="tdc2">3. Position of the Strata.</p> - -<p class="tdr"><a href="#sect1p3">p. 40</a></p> - -<div class="blockquot"> - -<p>Strata formed at the bottom of the sea, § 36. Apparent elevation -not produced by the retreat of the sea, § 37.—Strata, -horizontal, when formed, § 38, 39. Disturbance of the strata -proved from their inclined position § 40, 41, 42.—from shifts, -&c. § 42. Shifts of different dates, <i>ib.</i> Disturbance -of the primitive strata visible at their junction with the -secondary, § 43, 44. This disturbance produced by a force -directed upward, § 45, 46. This force the effect of subterraneous -heat, § 47, 48.</p> -</div> - - -<p class="caption3nb">SECTION II.</p> - -<p class="tdc">PHENOMENA PECULIAR TO UNSTRATIFIED BODIES.</p> - -<p class="tdc2">1. Metallic Veins.</p> - -<p class="tdr"><a href="#sect2p1">p. 57</a></p> - -<div class="blockquot"> - -<p>Veins defined. They contain substances that were once in fusion, § -49, 50. Metallic veins, native metals, &c. § 51. Native copper, § -52. Manganese, § 53. Fragments of rocks included in veins, § 55. -Shifting and heaving of veins, § 56, 57. Veins of different dates, -§ 58. Stratification not found in veins. Coating of the sides, -what, § 59. Metallic veins most common in primitive strata; but -not confined to them, § 60.</p> -</div> - -<p><span class="pagenum" id="Page_vii">- vii -</span></p> - -<p class="tdc2">2. Whinstone.</p> - -<p class="tdr"><a href="#sect2p2">p. 66</a></p> - -<div class="blockquot"> - -<p>Enumeration of stones of this genus, § 61. Whin, whether in veins -or in masses, resembles lava, § 62. Is a subterraneous lava, -§ 63. Columnar structure an argument for fusion, § 64. Not -produced by drying, § 65. Whinstone penetrated by pyrites, § 66. -Induration of the strata in contact with whin, § 67 Coal charred -by whinstone veins, § 68. Disturbance of the strata by whinstone -veins, § 69. Phenomena of whin interposed between strata, § 70, -71. Transition from whin to strata not gradual. § 72. Agates and -chalcedonies in whinstone, § 74. This stone melted and reproduced -from fusion by Sir James Hall, § 75. Mineral alkali found in it -by Dr Kennedy, <i>ib.</i> Whinstones of different formation, § -76. Porphyry a species or variety of whinstone, §77.</p> -</div> - -<p class="tdc2">3. Granite.</p> - -<p class="tdr"><a href="#sect2p3">p. 82</a></p> - -<div class="blockquot"> - -<p>Granite defined. Exists in masses and veins, § 77. The basis -of other rocks, § 78. Its original fluidity inferred from -the crystallization of its parts, § 79. Its fusion, from the -structure of the Portsoy granite, § 80, 81.—from granite veins, -§ 82. General conclusion as to the igneous origin of minerals, § -83, 84, 85. Actual existence of subterraneous heat known from hot -springs, volcanoes, earthquakes, § 86. Volcanic fire seated deep -under the surface, § 87. Subterraneous heat not accompanied by -burning, § 88, 89. Transmission of subterraneous heat, so as to -produce hot springs, &c. § 90, 91.</p> -</div> - -<p><span class="pagenum" id="Page_viii">- viii -</span></p> - - -<p class="caption3nb">SECTION III</p> - -<p class="tdc">PHENOMENA COMMON TO STRATIFIED AND UNSTRATIFIED BODIES.</p> - -<p class="tdr"><a href="#SECTION_III">p. 97</a></p> - -<div class="blockquot"> - -<p>Chemical agents which produce the decomposition of mineral -substances at the surface, § 92, 93. Mechanical agents, § 95, 96. -Proofs of wearing from the sea shore, § 97, 98. Rivers, § 99, -100. Defiles among mountains, § 102. Supply of the soil from the -decomposition of rocks, § 103. Gravel in the soil, § 104, 105. -Gold found in the soil, § 106. Tin, § 107. Proofs of waste from -mountainous countries, § 108, 109. Structure of Valleys, § 111. -Transportation of stones, § 112. Nearest measure of the waste, -§ 113. General remarks, § 114, 115. No production of minerals -on the surface, § 116. Reproduction at the bottom of the sea, § -117. Continued system of decay and renovation, § 118. Defence -against the charge of impiety, 119. Antiquity and order of the -revolutions of the globe, § 120, 121, 122, 123, 124. Consistency -with the Sacred Writings, § 125. Scope of this theory of the -earth distinguishes it from others; beauty and extent of its -views, § 126. New facts, § 127. Comparison of this theory with -that of Buffon, § 129. Of Lazzaro Moro, § 130. <i>Plutonic</i> -system, § 131. Distinguished by the principle of compression, -§ 132. Explains the oblate figure of the earth, <i>ib.</i> -Prejudices against this system, § 133. What may be expected from -the progress of science, § 134.</p> -</div> - -<p><span class="pagenum" id="Page_ix">- ix -</span></p> - - -<p class="caption3nb">NOTES AND ADDITIONS.</p> - -<p class="tdc2"><span class="smcap">Note i.</span>—Origin of Calcareous Earth.</p> - -<p class="tdr"><a href="#NOTES_and_ADDITIONS">p. 143</a></p> - -<div class="blockquot"> - -<p>Dr Hutton's opinion on this subject accurately stated, § 135. -Misrepresented by Kirwan, § 136.</p> -</div> - -<p class="tdc2"><span class="smcap">Note ii.</span>—Origin of Coal.</p> - -<p class="tdr"><a href="#Note_ii">p. 147</a></p> - -<div class="blockquot"> - -<p>Vegetable origin of coal. Opinion of Buffon, § 137.—of Arduino, -<i>ib.</i>—of Lehman, § 138. Distinction attempted between -wood coal and mineral coal, § 139. Not of different origin, but -gradually pass one into the other, § 140. Bovey coal, § 141. -Kirwan derives the matter of mineral coal from the decomposition -of hornblende, &c. 143. Absurdity of this supposition, § 144, -145, 146, 147.</p> -</div> - -<p class="tdc2"><span class="smcap">Note iii.</span>—Primitive Mountains.</p> - -<p class="tdr"><a href="#Note_iii">p. 160</a></p> - -<div class="blockquot"> - -<p>Lehman introduced the term Primitive mountains, § 149. Supposed -more ancient than organized bodies, § 150. Stratification of -primitive mountains denied by Pini, and maintained by Saussure, § -151.</p> -</div> - -<p class="tdc2"><span class="smcap">Note iv.</span>—Primary Strata not Primitive.</p> - -<p class="tdr"><a href="#Note_iv">p. 163</a></p> - -<div class="blockquot"> - -<p>Shells found in primary strata, § 152. Sandstone in primary -mountains, § 153. Quartzy sand in the schistus of the Grampians, -<i>ib.</i> Rocks distinguished by Werner into three orders, § -154. Objections to this arrangement, § 155.</p> -</div> - -<p><span class="pagenum" id="Page_x">- x -</span></p> - -<p class="tdc2"><span class="smcap">Note v.</span>—Transportation of the Materials of the Strata.</p> - -<p class="tdr"><a href="#Note_v">p. 171</a></p> - -<div class="blockquot"> - -<p>The transportation of materials, objected to by the Neptunists, is -implied in their own system, § 156, 157, 158. Proofs of great -transportation from the animal and vegetable remains, found in -rocks, § 160.</p> -</div> - -<p class="tdc2"><span class="smcap">Note vi.</span>—Kirwan's Notion of Precipitation.</p> - -<p class="tdr"><a href="#Note_vi">p. 180</a></p> - -<div class="blockquot"> - -<p>Difficulty, of precipitating the materials dissolved in the chaotic -fluid, § 162. Insufficiency of the explanation attempted, -<i>ib.</i></p> -</div> - -<p class="tdc2"><span class="smcap">Note vii.</span>—Compression in the Mineral Regions.</p> - -<p class="tdr"><a href="#Note_vii">p. 181</a></p> - -<div class="blockquot"> - -<p>Effects ascribed to compression by Newton, compared will the -effects ascribed to it in this theory, § 163. Fallacy of Kirwan's -argument concerning the fusion of Carrara marble, § 165, 166. -Heat of the mineral region may be supported without fuel, § 167. -Quotation from Newton's Optics, <i>ib.</i> General remarks, § 169.</p> -</div> - -<p class="tdc2"><span class="smcap">Note viii.</span>—Sparry Structure of Calcareous Petrifactions.</p> - -<p class="tdr"><a href="#Note_viii">p. 190</a></p> - -<div class="blockquot"> - -<p>Sparry and organic structure co-exist in certain fossils, § 171. -Sparry and stratified structure co-exist in gneiss, marble, &c. § -172.</p> -</div> - -<p><span class="pagenum" id="Page_xi">- xi -</span></p> - -<p class="tdc2"><span class="smcap">Note ix.</span>—Petroleum, &c.</p> - -<p class="tdr"><a href="#Note_ix">p. 194</a></p> - -<div class="blockquot"> - -<p>Petroleum, &c. from the distillation of coal, § 173. Gradation from -petroleum to coal often met with, § 174. Connection of amber and -coal, § 175. Why mines of blind coal have not always petroleum -mines near them, § 176.</p> -</div> - -<p class="tdc2"><span class="smcap">Note x.</span>—The Height above the Level of the Sea, at which Marks -of Aqueous Deposition are now found.</p> - -<p class="tdr"><a href="#Note_x">p. 199</a></p> - -<div class="blockquot"> - -<p>These marks consist either in stratification or in marine objects, -§ 177. The marks of stratification observed, 14739 feet -above the sea, § 178. Shells in Peru, 14190, § 179. Kirwan's -mistake concerning these shells, § 180. His error similar to -<span class="smcap">Voltaire's</span>, § 181.</p> -</div> - -<p class="tdc2"><span class="smcap">Note xi.</span>—Fracture and Dislocation of the Strata.</p> - -<p class="tdr"><a href="#Note_xi">p. 204</a></p> - -<div class="blockquot"> - -<p>Slips, § 182. Rib of limestone in a slip near Huddersfield, § 183, -184. Singular fracture of pudding-stones at Oban in Argyleshire, -§ 185. Similar phenomena observed by Saussure between Nice and -Genoa, <i>ib.</i> Remarks on it, § 186.</p> -</div> - -<p class="tdc2"><span class="smcap">Note xii.</span>—Elevation and Inflection of the Strata.</p> - -<p class="tdr"><a href="#Note_vii">p. 209</a></p> - -<div class="blockquot"> - -<p>Junction of primary and secondary strata, § 187. Breccia -incumbent on the primary, § 188. Junction of the primary and -secondary strata: At Torbay in Devonshire, -<span class="pagenum" id="Page_xii">- xii -</span> -§ 190,—coast of -Berwickshire, § 191,—Cullen in Banffshire, § 193,—Ardencaple -in Dunbartonshire, Arran, &c. § 194,—Pembrokeshire, -§ 195,—Jedburgh, § 196,—Ingleborough in Yorkshire, § -197,—Cumberland, § 198. Inflection of the strata, § 199. -Remarkable instances in the Alps and Pyrenees, § 200, 201,—on -Ben-Lawers in Perthshire, § 202,—coast of Berwickshire, -<i>ib.</i>—Plymouth, § 203. Strata suffering such inflections -have been soft and ductile, § 204. General property of these -inflections, § 205, 206. uniform stretch of the primary strata, -§ 207. Inferences as to the nature of the elevating force, § -208. Imperfection of other theories. Crystallisation, <i>ib.</i> -Marks of undulæ in the schistus, § 209. Elevation of the strata -a stronghold of the Huttonian theory, § 210. Elevation of the -strata enables us to see far into the interior of the earth, § -211.</p> -</div> - -<p class="tdc2"><span class="smcap">Note xiii.</span>—Metallic Veins.</p> - -<p class="tdr"><a href="#Note_xiii">p. 239</a></p> - -<div class="blockquot"> - -<p>Specimens of native iron, § 212, 213. Margraaf's specimen, § 214. -Kirwan's hypothesis, § 215. Increase of the specific gravity of -native gold by fusion, no argument against its igneous origin, -§ 216. Specimens of gold and silver shooting through quartz, an -argument in favour of the Huttonian theory, § 218, 219. Proof in -favour of the same from chalcedony including calcareous spar, -§ 220. Matter that fills veins not from above or from either -side, § 221. Opinion of the Neptunists, § 222. Supposed fact -that veins are less rich as the depth increases, § 223. No marks -of horizontal deposition in veins; their coating -<span class="pagenum" id="Page_xiii">- xiii -</span> -differs from -stratification, § 224. Neptunists appear to be misled by the term -Stratification, § 225, 226. Veins heave or shift one another, -§ 227. Vast force employed for that purpose, § 228. Veins of -different formation, § 231. Pieces of rock insulated in veins, § -232. Supposition that veins have been filled by infiltrations, -absurd, 233. <i>Lenticular</i> veins, and Pipe veins, § 234.</p> -</div> - -<p class="tdc2"><span class="smcap">Note xiv.</span>—On Whinstone.</p> - -<p class="tdr"><a href="#Note_xiv">p. 260</a></p> - -<div class="blockquot"> - -<p>Whinstone, neither of volcanic nor aqueous formation, § 235. -Zeolite and carbonate of lime included in whinstone, but not -in lava, <i>ib.</i> Not introduced by infiltration, § 236. -Disposition of whinstone mountains differs from that of streams -of lava, § 237. This argument first employed by Mr Strange, -§ 238. His general views of this subject, § 239. Explanation -of the regular structure of whinstone hills, according to Dr -Hutton's theory, § 240. Many hills supposed to be extinguished -volcanoes, are rocks of real whinstone that has flowed deep -under the surface. Vein of whinstone mistaken for a stream of -lava by Faujas, § 241, 242. Submarine volcanoes of Dolomieu, § -243. Objections to this theory, § 244, 245. Dolomieu in another -place contends for the aqueous formation of basaltes, § 246. -His arguments answered; also those of Bergman, § 248, 249. -Argument of <span class="smcap">Werner</span> for the aqueous origin of basaltes, -§ 250. Remarks on the supposed gradual transition of basaltes -to argillaceous schistus, § 251, 252. Of the shells said to be -found in basaltes, § 253. -<span class="pagenum" id="Page_xiv">- xiv -</span> -Instances from Portrush in Ireland, -and from Cerigo on the Coast of Greece, <i>ib.</i> and 254,—from -the Veronese, § 255. Objections to the Neptunian formation -of whinstone, founded on the difference between it and the -contiguous stratified rocks, § 256. On the resemblance of the -strata below and above certain masses of whinstone, § 257. On the -irregularity of the thickness of those masses, § 258. Wedge form -masses of whinstone included between strata, § 259. Consequences -of this wedge form, § 260. Sandstone fragments included in whin, -§ 261, 262. Bending of the strata contiguous to whinstone, § 264. -Induration, § 265, 266. Charring of coal by whin, § 267. Of the -manner in which the bitumen may have been driven off by heat, § -268. Two kinds of fossil coke, § 269. Graduation into plumbago, -<i>ib.</i> and 270. Only remaining objection obviated by Sir -James Hall's experiments, § 271.</p> -</div> - -<p class="tdc2"><span class="smcap">Note xv.</span>—On Granite.</p> - -<p class="tdr"><a href="#Note_xv">p. 307</a></p> - -<div class="blockquot"> - -<p>Granite veins of two kinds, § 274. Veins Of which the communication -with large masses of the same stone is not visible: At the Isle -of Coll in the Hebrides, § 275,—at Portsoy, § 276,—in Cornwall, -§ 277,—in Glentilt, § 278. Veins visibly connected with larger -masses. Argument furnished by them in favour of this theory, § -279, 280. Impossibility of their being formed by infiltration, § -281. Veins of this kind in Arran, § 282,—Galloway, § 283,—sides -of Loch Chloney, Invernessshire, §284,—St Michael's Mount, -Cornwall § 285. Fragments of schistus contained in granite, § 287.</p> -</div> - -<p><span class="pagenum" id="Page_xv">- xv -</span></p> - -<p class="tdc2">2. Granite of Portsoy.</p> - -<p class="tdr"><a href="#Granite_of_Portsoy">p. 320</a></p> - -<div class="blockquot"> - -<p>Description of this granite, § 288. Pierre graphique of M. Patrin -not perfectly the same with that of Portsoy, § 289. Quartz -crystallized in the pierre graphique, § 290. Instances of quartz -crystallized in other granites. In that of St Agnes in Cornwall, -§ 291. Whether this crystallization is only found in secondary -granites, § 292.</p> -</div> - -<p class="tdc2">3. Stratification of Granite.</p> - -<p class="tdr"><a href="#Stratification">p. 326</a></p> - -<div class="blockquot"> - -<p>Question stated concerning the stratification of granite, § 293. -Remarkable examples of stratified granite at Chorley Forest, -Leicestershire, and at Fassnet <i>Water</i> in Berwickshire, § -295. Stratification of Mont Blanc, and the Aiguilles of Chamouni -maintained by Saussure, § 296, 297. Seems nevertheless doubtful, -§ 298. In the granite mountains of Arran doubtful; § 300. -Explanation of the stratification of granite in this theory, § -301. If granitic veins were found proceeding from real granitic -strata, they could not be explained on the principles here laid -down, § 302. No such veins have been discovered, § 303. Answer to -an objection made to the igneous origin of granitic mountains, § -304, 305. Of the proportion of the earth's surface occupied by -granite rocks, § 306. Not exceeding a ninetieth part, § 307, 311. -Extent of granite in Scotland erroneously estimated by Dr Hutton, -§ 312. Amounts perhaps to a twenty-fourth of the whole surface, § -313. Observations on Mr Kirwan's opinion, § 314.</p> -</div> - -<p><span class="pagenum" id="Page_xvi">- xvi -</span></p> - -<p class="tdc2"><span class="smcap">Note xvi.</span>—Rivers and Lakes.</p> - -<p class="tdr"><a href="#Note_xvi">p. 350</a></p> - -<div class="blockquot"> - -<p>The rivers have hollowed out the valleys, § 315. Illustration -from the course of the Danube, § 316. Courses of many rivers -retain marks of having consisted of a series of lakes, § 317, -318. Filling up and draining of lakes, § 320. Instances from the -lakes in Cumberland, § 321. Lake of Geneva, § 322. Lakes in North -America, <i>ib.</i> Cataracts, § 323. Difficulties in explaining -the generation and continuance of lakes exemplified in that of -Geneva, § 324. Attempt to resolve these difficulties, § 325, 326, -327, 328. All lakes not equally subject to them, § 329. Wasting -of the land by the rivers, proved from the mouths of rivers on -bold coasts, § 330. Examples from Cornwall, § 331.</p> -</div> - -<p class="tdc2"><span class="smcap">Note xvii.</span>—Remains of Decomposed Rocks.</p> - -<p class="tdr"><a href="#Note_xvii">p. 371</a></p> - -<div class="blockquot"> - -<p>Plain of Crau, § 334. Its gravel from the decomposition of -pudding-stone, § 385. Same true of much of the gravel in this -island, § 337, 338. Mount Rigi in Switzerland the remains of a -body of pudding-stone, § 339. Measure of the destruction in the -stratified rocks sometimes, afforded by the unstratified, § 340, -341. Rate at which the elevation of mountains has been supposed -to decrease, § 342.</p> -</div> - -<p class="tdc2"><span class="smcap">Note xviii.</span>—Transportation of Stones, &c.</p> - -<p class="tdr"><a href="#Note_xviii">p. 381</a></p> - -<div class="blockquot"> - -<p>Gravel smaller and rounder the farther from its native place, § -343. Different sources of <i>caillou roulés</i>, -<span class="pagenum" id="Page_xvii">- xvii -</span> -§ 344, 345. -Stones that have begun their migration before the cutting out of -the present valleys, § 346. Declivity necessary to enable stones -to travel from the top of Mont Blanc to the top of Mont Jura, -§ 347. Granite from Mont Blanc found eastward in the valley of -the Drance, § 348. Machinery employed by nature in transporting -rocks, § 349, 350. Instances of transported stones of great -size,—from the vicinity of Geneva, § 351, 352,—from the Isle -of Arran, 353. How gravity may contribute to the moving of large -stones, even when the declivity is small, § 354. Rocking-stones, -§ 355. Stone in Borrowdale,—in the valley of Urseren, § 356. -Large stones are sometimes the remains of veins, § 357. Of the -hypothesis of a <i>debacle</i>, § 358. Structure of valleys -unfavourable to this hypothesis, § 359, 360. Particularly of -valleys close at the ends, § 361, 362. Whether the supposition -of a <i>debacle</i> is necessary to explain the moving of large -masses of rock, § 364. Whether the abrupt faces of hills indicate -the existence of any sudden torrent, &c. § 365. Fact concerning -the steep faces of the mountains in the south of Africa, § -366. A fact stated that would lead necessarily to belief in a -<i>debacle</i>; no example of it has yet occurred, § 367.</p> -</div> - -<p class="tdc2"><span class="smcap">Note xix.</span>—Transportation of Materials by the Sea.</p> - -<p class="tdr"><a href="#Note_xix">p. 413</a></p> - -<div class="blockquot"> - -<p>Of the manner in which the <i>detritus</i> of the land is spread -out over the bottom of the sea, § 369, 370. Seas rendered -shallower, § 371. Sand banks, § 372. Great system of currents -traced in the Atlantic, § 373, 374. How far this transportation -of materials may affect the -<span class="pagenum" id="Page_xviii">- xviii -</span> -earth's diurnal motion, § 376, 377. -Kirwan's misapprehension of Frisi, and of Major Rennell, § 378, -379. His mistake about the tides, § 380, 381,—and about the -formation of sand banks, § 384.</p> -</div> - -<p class="tdc2"><span class="smcap">Note xx.</span>—Inequalities of the Planetary Motions.</p> - -<p class="tdr"><a href="#Note_xx">p. 437</a></p> - -<div class="blockquot"> - -<p>These inequalities all periodical, § 385. Circumstances on which -this depends, § 386. Affinity of this conclusion to that which Dr -Hutton has established with respect to the changes at the surface -of the earth, § 387.</p> -</div> - -<p class="tdc2"><span class="smcap">Note xxi.</span>—Changes in the Apparent Level of the Sea.</p> - -<p class="tdr"><a href="#Note_xxi">p. 441</a></p> - -<div class="blockquot"> - -<p>Relative level of the sea and land subject to change, § 388. Proofs -that it has sunk, on the shores of this island, § 389,—on the -coasts of France and Flanders, § 390, 391,—on the shores of the -Baltic, § 392. This has not arisen from the depression of the -sea, but from the elevation of the land, § 393, 394. The surface -of the Hadriatic higher now than formerly, § 395, 396. Also of -the Mediterranean, § 398. Irregularities in these changes, § 399, -400. Hypothesis of Frisi, that towards the equator the sea is -every where rising, § 401. Disproved, <i>ib.</i> Conclusion, § -402.</p> -</div> - -<p class="tdc2"><span class="smcap">Note xxii.</span>—Fossil Bones.</p> - -<p class="tdr"><a href="#Note_xxii">p. 458</a></p> - -<div class="blockquot"> - -<p>Vegetable and animal remains contained in the fossil kingdom, § -403. Of those that are enveloped or penetrated with calcareous -earth, § 405, 406. Of the bones buried in the loose earth, § 407. -Bones in Siberia referred to the rhinoceros and the elephant, -<span class="pagenum" id="Page_xix">- xix -</span> -§ -408. Those on the Ohio doubtful, § 408, 409. Opinion of Camper, -§ 410.—of Cuvier, § 411. Objections to the latter, <i>ib.</i> -Enumeration of five <i>species</i> of animals now extinct, § -412. Change in the animal, and vegetable kingdom may account for -bones found in countries where no analogous species now exists, -§ 414. Proofs that the animals whose bones are found in Siberia -inhabited that country, § 415-417.</p> -</div> - -<p class="tdc2"><span class="smcap">Note xxiii.</span>—Geology of Kirwan and De Luc.</p> - -<p class="tdr"><a href="#Note_xxiii">p. 477</a></p> - -<div class="blockquot"> - -<p>These authors have improperly drawn religion into their quarrel -with Dr Hutton, § 419. De Luc writes a history of what befel the -earth before the creation of the sun, § 420. Remarks on Kirwan's -geological writings, § 422, 423, 424, 425.</p> -</div> - -<p class="tdc2"><span class="smcap">Note xxiv.</span>—System of Buffon.</p> - -<p class="tdr"><a href="#Note_xxiv">p. 483</a></p> - -<div class="blockquot"> - -<p>In what Buffon's theory of the earth and Dr Hutton's agree, -and in what they differ, § 426, 427. Great merit of Buffon, -notwithstanding his errors, § 428.</p> -</div> - -<p class="tdc2"><span class="smcap">Note xxv.</span>—Figure of the Earth.</p> - -<p class="tdr"><a href="#Note_xxv">p. 488</a></p> - -<div class="blockquot"> - -<p>Physical cause of the earth's oblate figure not obvious from its -present condition, § 429. How explained by the Neptunists, § -430. Examination of their solution, § 431, 432. Contradiction -implied in it, § 433. Insufficiency of Buffon's explanation, § -434. Of the principle on which the oblateness of the earth may be -accounted for in Dr Hutton's theory, § 435. Of the changes that -would happen in the figure of a terraqueous body like the earth, -supposing -<span class="pagenum" id="Page_xx">- xx -</span> -it ever so irregular, § 436, 437, 438. Two different -causes of change, <i>ib.</i> Ultimate figure, that by which the -causes of change are best resisted, § 439. Spheroidal figure, -never perfectly acquired, § 440. Agreement of this theory with -observation, § 441. Probable extension of the system of waste, -and renovation to the other planets, § 442, 443. Confirmation -from the system of Saturn, § 444, 445.</p> -</div> - -<p class="tdc2"><span class="smcap">Note xxvi.</span>—Prejudices relating to the Theory of the Earth.</p> - -<p class="tdr"><a href="#Note_xxvi">p. 510</a></p> - -<div class="blockquot"> - -<p>Alleged by some that a theory of the earth ought not at present to -be attempted, § 446. The quick succession of geological theories -has partly arisen from their object being misunderstood, § 447. A -succession of theories is often a continued approximation to the -truth, § 448. The more various the phenomena of any class, the -greater the chance of discovering their true cause, § 449. Reason -to think that the leading facts in geology are now known, § 450, -451. A tendency may be observed in geological systems to approach -to one another, and to the Huttonian, § 452. Example from that -of Saussure, § 453,—of Dolomieu, § 454, 455. The discoveries of -Dr Black were necessary for understanding the true theory of the -earth, § 457. Use of theory in matters of observation, § 458, &c.</p> -</div> - - -<div class="figcenter" style="width: 400px; padding: 48px 0;"> - <img src="images/bar_double.png" width="400" height="15" alt="" /> -</div> - -<div class="chapter"> -<p><span class="pagenum" id="Page_1">- 1 -</span></p> - -<h2 class="nobreak" id="ILLUSTRATIONS">ILLUSTRATIONS, &c.</h2> -</div> - - -<div class="fl_left"> -<span class="vbig">A</span> -</div> - -<p><span class="hidden">A </span><span class="smcap">Very</span> little attention to the phenomena of the mineral -kingdom, is sufficient to convince us, that the condition of the -earth's surface has not been the same at all times that it is at the -present moment. When we observe the impressions of plants in the heart -of the hardest rocks; when we discover trees converted into flint, and -entire beds of limestone or of marble composed of shells and corals; -we see the same individual in two states, the most widely different -from one another; and, in the latter instance, have a clear proof, -that the present land was once deep immersed under the waters of the -ocean. If to this we add, that many masses of rock, the most solid and -compact, consist of no other materials but sand and gravel; that, on -the other hand, loose gravel, such as is formed only in beds of rivers, -or on the sea shore, now abounds in places remote from both: if we -reflect, at the same time, on the irregular -<span class="pagenum" id="Page_2">- 2 -</span> -and broken figure of our -continents, and the identity of the mineral strata on opposite sides of -the same valley, or the same inlet of the sea; we shall see abundant -reason to conclude, that the earth has been the theatre of many great -revolutions, and that nothing on its surface has been exempted from -their effects.</p> - -<p>To trace the series of these revolutions, to explain their causes, and -thus to connect together all the indications of change that are found -in the mineral kingdom, is the proper object of a <span class="smcap">Theory of the -Earth</span>.</p> - -<p>But, though the attention of men may be turned to the theory of the -earth by a very superficial acquaintance with the phenomena of geology, -the formation of such a theory requires an accurate and extensive -examination of those phenomena, and is inconsistent with any but a -very advanced state of the physical sciences. There is, perhaps, in -those sciences, no research more arduous than this; none certainly -where the subject is so complex; where the appearances are so extremely -diversified, or so widely scattered, and where the causes that have -operated are so remote from the sphere of ordinary observation. Hence -the attempt! to form a theory of the earth are of very modern origin, -and as, from the simplicity of its subject astronomy is the eldest, so, -on account of the complexness -<span class="pagenum" id="Page_3">- 3 -</span> -of its subject, geology is the youngest -of the sciences.</p> - -<p>It is foreign from the present purpose to enter on any history of -the systems that, since the rise of this branch of science, have -been invented to explain the phenomena of the mineral kingdom. It is -sufficient to remark, that these systems are usually reduced to two -classes, according as they refer the origin of terrestrial bodies to -<span class="smcap">fire</span> or to <span class="smcap">water</span>; and that, conformably to this -division, their followers have of late been distinguished by the -fanciful names of <i>Vulcanists</i> and <i>Neptunists</i>. To the -former of these Dr Hutton belongs much more than to the latter; though, -as he employs the agency both of fire and of water in his system, he -cannot, in strict propriety, be arranged with either.</p> - -<p>In the succinct account which I am now about to give of this system, I -shall consider the mineral kingdom as divided into two parts, namely, -stratified and unstratified substances I shall treat, first, of the -phenomena peculiar to the stratified; next, of those peculiar to the -unstratified; and, lastly, of the phenomena common to both. Beginning, -then, with the first, the subject naturally divides itself into three -branches; viz. the <i>materials</i> the <i>consolidation</i>, and the -<i>position</i> of the strata.</p> - - -<hr class="chap x-ebookmaker-drop" /> - -<div class="chapter"> -<p><span class="pagenum" id="Page_4">- 4 -</span></p> - -<h2 class="nobreak" id="SECTION_I">SECTION I.</h2> -</div> - -<p class="caption3nb">OF THE PHENOMENA PECULIAR TO STRATIFIED BODIES.</p> - - -<p class="caption3nb">1. <i>Materials of the Strata.</i></p> - -<div class="fl_left"> -<span class="num_left">1.</span> <span class="vbig">I</span> -</div> - -<p><a id="sec_1"></a><span class="hidden">1. I</span>T is well known that, on removing the loose earth which forms -the immediate surface of the land, we come to the solid rock, of which -a great proportion is found to be regularly disposed in strata, or beds -of determinate thickness, inclined at different angles to the horizon, -but separated from one another by equidistant superficies, that often -maintain their parallelism to a great extent. These strata bear such -evident marks of being deposited by water, that they are universally -acknowledged to have had their origin at the bottom of the sea; and -it is also admitted, that the materials which they consist of, were -then either soft, or in such a state of comminution and separation, -as renders them capable of arrangement by the action of the water in -which they were immersed. Thus far most of the theories of the earth -agree; -<span class="pagenum" id="Page_5">- 5 -</span> -but from this point they begin to diverge, and each to assume -a character and direction peculiar to itself. Dr Hutton's does so, by -laying down this fundamental proposition, That in all the strata we -discover proofs of the materials having existed as elements of bodies, -which must have been destroyed before the formation of those of which -these materials now actually make a part.<a id="FNanchor_1" href="#Footnote_1" class="fnanchor">[1]</a></p> - -<div class="footnote"> - -<p><a id="Footnote_1" href="#FNanchor_1" class="label">[1]</a> Hutton's Theory, vol. I p. 20, &c.</p> - -</div> - -<p>2. The calcareous strata are the portion of the mineral kingdom that -gives the clearest testimony to the truth of this assertion. They often -contain shells, corals, and other exuviæ of marine animals in so great -abundance, that they appear to be composed of no other materials. -Though these remains of organized bodies are now converted into stone -or into spar, their shape and interior structure are often so well -preserved, that the species of animal or plant of which they once made -a part, can still be distinguished and pointed out among the living -inhabitants of the ocean.</p> - -<p>Others of the calcareous strata appear to be composed of fragments of -some ancient rocks, which, after having been broken, have been again -united into a compact stone. In these we find pieces clearly marked -as having been once continuous but now placed at a distance from -<span class="pagenum" id="Page_6">- 6 -</span> -one another, and exhibiting exactly the same appearances as if they floated -in a fluid of the same specific gravity with themselves.</p> - -<p>From these, therefore, and a variety of similar appearances, Dr Hutton -concludes, that the materials of all the calcareous strata have been -furnished, either from the dissolution of former strata, or from the -remains of organized bodies. But, though this conclusion is meant to be -extended to all the calcareous strata, it is not asserted that every -cubic inch of marble or of limestone contains in it the characters of -its former condition, and of the changes through which it has passed. -It may, however, be safely affirmed, that there is scarce any entire -stratum where such characters are not to be found. These must be -held as decisive with respect to the whole system of strata to which -they belong; they prove the existence of calcareous rocks before the -formation of the present; and, as the destruction of those is evidently -adequate to the supply of the materials of these that we now see, to -look for any other supply were superfluous, and could only embarrass -our reasonings by the introduction of unnecessary hypotheses.<a id="FNanchor_2" href="#Footnote_2" class="fnanchor">[2]</a></p> - -<div class="footnote"> - -<p><a id="Footnote_2" href="#FNanchor_2" class="label">[2]</a> <span class="smcap"><a href="#Note_i">Note i.</a></span></p> - -</div> - -<p>3. The same conclusions result from an examination of the siliceous -strata; under which we may comprehend the common sandstone, -<span class="pagenum" id="Page_7">- 7 -</span> -and also -those pudding-stones or breccias where the gravel consists of quartz. -In all these instances, it is plain, that the sand or gravel existed in -a state quite loose and unconnected, at the bottom of the sea, previous -to its consolidation into stone. But such bodies of gravel or sand -could only be formed from the attrition of large masses of quartz, or -from the dissolution of such sandstone strata as exist at present; for -it will hardly be alleged, that sand is a crystallization of quartz, -formed from that substance, when it passes from a fluid to a solid -state.</p> - -<p>Those pudding-stones in which the gravel is round and polished, carry -the conclusion still farther, as such gravel can only be formed in the -beds of rivers or on the shores of the sea; for, in the depths of the -ocean, though currents are known to exist, yet there can be no motion -of the water sufficiently rapid to produce the attrition required to -give a round figure and smooth surface to hard and irregular pieces -of stone. There must have existed, therefore, not only a sea, but -continents, previously to the formation of the present strata.</p> - -<p>The same thing is clearly shown by those petrifactions of wood, where, -though the vegetable structure is perfectly preserved, the whole mass -is siliceous, and has, perhaps, been found -<span class="pagenum" id="Page_8">- 8 -</span> -in the heart of some -mountain, deep imbedded in the solid rock.</p> - -<p>4. Characters of the same import are also found among the argillaceous -strata, though perhaps more rarely than among the calcareous or -siliceous. Such are the impressions of the leaves and stems of -vegetables; also the bodies of fish and amphibious animals, found very -often in the different kinds of argillaceous schistus, and in most -instances having the figure accurately preserved, but the substance -of the animal replaced by clay or pyrites. These are all remains -of ancient seas or continents; the latter of which have long since -disappeared from the surface of the earth, but have still their memory -preserved in those archives, where nature has recorded the revolutions -of the globe.</p> - -<p>5. Among bituminous bodies, pit-coal is the only one which constitutes -regular and extensive strata; and no fossil has its origin from the -waste of former continents, marked by stronger and more distinct -characters. Not to mention that the coal strata are alternated with -those that have been already enumerated, and that they often contain -shells and corals, perfectly mineralized, it is sufficient to remark, -that there are entire beds of this fossil, which appear to consist -wholly of wood, and in which the fibrous structure is perfectly -preserved. From these instances, -<span class="pagenum" id="Page_9">- 9 -</span> -the appearances of vegetable -structure may be traced through all possible gradations, down to an -evanescent state. This last state is undoubtedly the most common; and -though coal does not then, on bare inspection, make known its vegetable -origin, yet, if we take it in connection with the other terms of the -series, as we may call them; if we consider that the two extremes, viz. -coal, with the vegetable structure perfect, and coal without any such -structure visible, are often found in the same or in contiguous beds; -and, if we remark, that through all these gradations coal contains -nearly the same chemical elements, and yields, on analysis, bitumen and -charcoal, combined with a greater or less proportion of earth: if we -take all these circumstances into account, we cannot doubt that this -fossil is every where the same, and derives its origin from the trees -and plants that grew on the surface of the earth before the formation -of the present land.</p> - -<p>6. Dr Hutton has further observed, that if those ancient continents -were at all similar to the present, we can be at no loss to account for -the want of any distinct mark of vegetable organization in the greater -part of the coal strata. It is plain, that the daily waste of animal -and vegetable substances on the surface of the earth, must disengage -a great quantity of oily as well -<span class="pagenum" id="Page_10">- 10 -</span> -as carbonic matter, which, with -whatever element it is at first combined, is ultimately delivered into -the ocean. Thus, the oily or fuliginous parts of animal and vegetable -substances, let loose by burning, first ascend into the atmosphere, but -are at length precipitated, and either fall immediately into the sea, -or are, in part at least, washed down into it from the land. From other -causes also, much vegetable matter is carried down by the rivers; and -the whole quantity of animal and vegetable substances thus delivered -into the sea, must be very considerable, amounting annually to the -whole residuum of those substances, not employed in the maintenance or -reproduction of animal and vegetable bodies. Whether chemically united -to the waters of the ocean, or simply suspended in them, this matter is -at last precipitated, and, mingling with earthy substances, is formed -into strata, the place of which will be determined by the currents, the -position of the present continents, and many other circumstances not -easily enumerated.</p> - -<p>If, then, an order of things similar to what we now see, existed before -the formation of the present strata, it would necessarily happen, that -the animal and vegetable substances, diffused through the ocean, being -separated from the water, would be deposited at the bottom of the -<span class="pagenum" id="Page_11">- 11 -</span> -sea, and, in the course of ages, would form beds, less or more pure, -according to the quantity of earth and other substances deposited -at the same time. These beds being consolidated and mineralized by -operations that are afterwards to be considered, have been converted -into pit-coal, the parts of which are impalpable, and retain nothing of -their primitive structure.<a id="FNanchor_3" href="#Footnote_3" class="fnanchor">[3]</a></p> - -<div class="footnote"> - -<p><a id="Footnote_3" href="#FNanchor_3" class="label">[3]</a> <span class="smcap"><a href="#Note_ii">Note ii.</a></span></p> - -</div> - -<p>If, then, the formation of coal from animal and vegetable bodies be -admitted, the general position which derives the origin of the strata -from the waste of former land, as it is applicable to all the kinds -already enumerated, and of course to all those with which they are -alternated, comprehends a very large portion of the earth's surface. -It comprehends, indeed, all the strata usually distinguished by the -name of <i>Secondary</i>; but there is another great division of the -mineral kingdom, viz. the rocks, called <i>Primitive</i>, which, as -they are never alternated with the secondary, but are always inferior -to them, must be further examined, before we can decide whether the -same conclusion extends to them or not.</p> - -<p>7. Here it must be carefully observed, that, among the primary rocks, -the granite is not meant to be included, except where that stone is -stratified, and either coincides with veined -<span class="pagenum" id="Page_12">- 12 -</span> -granite or with gneiss. -The primitive strata, in Dr Hutton's theory, comprehend, besides -gneiss, the micaceous, chlorite, hornblende, and siliceous schistus, -together with slate, and some other kinds of argillite; to which we -must add, serpentine, micaceous limestone, and the greater part of -marbles. These are mostly distinguished by their laminated structure, -by having their planes much elevated with respect to the horizon, -and by belonging more to the mountainous than the level parts of the -earth's surface. They rarely contain vestiges of organized bodies; -so rarely, indeed, that they were called primitive by the geologists -who first distinguished them from other rocks, on the supposition of -their being part of the primeval nucleus of the globe, which had never -undergone any change whatsoever; but this, I believe, has now almost -ceased to be the opinion of any geologist.<a id="FNanchor_4" href="#Footnote_4" class="fnanchor">[4]</a> The Neptunists hold the -rocks, here enumerated, and also granite, to be produced by aqueous -deposition; but maintain them to be in the strictest sense primeval, -and of a formation antecedent to all organized bodies.</p> - -<div class="footnote"> - -<p><a id="Footnote_4" href="#FNanchor_4" class="label">[4]</a> <span class="smcap"><a href="#Note_iii">Note iii.</a></span></p> - -</div> - -<p>8. In opposition to this, Dr Hutton maintained, that the primary -schistus, like all the other strata, was formed of materials deposited -at the -<span class="pagenum" id="Page_13">- 13 -</span> -bottom of the sea, and collected from the waste of rocks still -more ancient. When, therefore, he conformed to the received language -of mineralogists, by calling these strata primitive, he only meant -to describe them as more ancient than any other strata now existing, -but not as more ancient than any that ever had existed. They are -distinguished, in his system, by the name of <i>Primary</i>, rather -than of <i>Primitive</i> strata.</p> - -<p>That the account now given of their origin is well founded, may be -proved by unquestionable facts. For, first, though, agreeably to the -observation just made, the ancient strata do but rarely contain any -remains of organized bodies, they are not entirely destitute of them. -Different places in this island have been pointed out by Dr Hutton, -where marine objects have been discovered in primary limestone, either -by himself or others, and it would not be difficult to add more -instances of the same kind.<a id="FNanchor_5" href="#Footnote_5" class="fnanchor">[5]</a> In Dauphine, coal, which is certainly a -derivative substance, has been found among mountains which have a title -to the character of primitive, such as no one will dispute. These facts -put the composition of such rocks from loose materials, beyond all -doubt, and also prove their formation to be posterior to the existence -<span class="pagenum" id="Page_14">- 14 -</span> -of an animal and vegetable system. They do indeed prove this in the -strictest sense, only of the particular beds in which they are found; -but as these beds are in all other respects as much to be accounted -primary as any part of the mineral kingdom, it is evident that the -negative instances are here of no force, and that nothing can be gained -to the adversaries of this opinion by denying it in general, if they -are obliged to admit it in a single case.</p> - -<div class="footnote"> - -<p><a id="Footnote_5" href="#FNanchor_5" class="label">[5]</a> <span class="smcap"><a href="#Note_iv">Note iv.</a></span></p> - -</div> - -<p>9. Again, it is certain, as Dr Hutton remarks, that there are few -considerable bodies of schistus, even the most decidedly primitive, -where sand and gravel may not in some parts be observed. Indeed, it is -not only true that they are to be found in some parts of them; but, -in fact, among many of the primitive mountains, we find large tracts, -composed entirely of a schistose and much indurated sandstone, in beds -highly inclined, sometimes alone, sometimes alternated with other -schisti. In many of them, the sand of which they consist appears to be -entirely of granite, from the detritus of which rock it should seem -that they were chiefly formed.</p> - -<p>10. Thus we conclude, that the strata both primary and secondary, -both those of ancient and those of more recent origin, have had their -materials furnished from the ruins of former continents, from the -dissolution of rocks, or the -<span class="pagenum" id="Page_15">- 15 -</span> -destruction of animal or vegetable -bodies, similar, at least in some respects, to those that now occupy -the surface of the earth. This conclusion is not indeed proved of every -individual portion of rock, but it is demonstrated of many and large -parts, and those scattered indifferently through all the varieties of -the strata; and therefore, from the rules of the strictest reasoning, -we must infer, that the whole is derived from the same origin.<a id="FNanchor_6" href="#Footnote_6" class="fnanchor">[6]</a></p> - -<div class="footnote"> - -<p><a id="Footnote_6" href="#FNanchor_6" class="label">[6]</a> <span class="smcap"><a href="#Note_v">Note v.</a></span></p> - -</div> - -<p>Thus far concerning the materials of the strata; and, as these were -originally loose and unconnected, we must next consider by what means -they were consolidated into stone.</p> - - -<p class="caption3nb" id="sect1p2">2. <i>Consolidation of the Strata</i>.</p> - -<p>11. Though Dr Hutton has no where defined the meaning of the term -consolidation, he has been scrupulously exact in using it constantly -in the same sense. He understands by it, not merely that quality in a -hard body, by which its parts cohere together, but also that by which -it fills up the space comprehended within its surface, being to sense -without porosity, and impervious to air and moisture.</p> - -<p><span class="pagenum" id="Page_16">- 16 -</span></p> - -<p>Now, a porous mass of unconnected materials, such as the strata appear -originally to have been, can acquire hardness and solidity only in two -ways, that is, either when it is first reduced by heat into a state of -fusion, or at least of softness, and afterwards permitted to cool; or -when matter that is dissolved in some fluid menstruum, is introduced -along with that menstruum into the porous mass, and, being deposited, -forms a cement by which the whole is rendered firm and compact. Fire -and water, therefore, are the only two physical agents to which we can -ascribe the consolidation of the strata; and, in order to determine to -which of them that effect is to be attributed, we must inquire whether -there are any certain characters that distinguish the action of the one -from that of the other, and which may be compared with the phenomena -actually observed among mineral substances.</p> - -<p>12. First, then, it is evident, that the consolidation produced by the -action of water, or of another fluid menstruum, in the manner just -referred to, must necessarily be imperfect, and can never entirely -banish the porosity of the mass. For the bulk of the solvent, and of -the matter it contained in solution, being greater than the bulk of -either taken singly, when the latter was deposited, the former would -have sufficient room left, and would continue to occupy -<span class="pagenum" id="Page_17">- 17 -</span> -a certain -space in the interior of the strata. A liquid solvent, therefore, could -never shut up the pores of a body to the entire exclusion of itself; -and, had mineral substances been consolidated, as here supposed, the -solvent ought either to remain within them in a liquid state, or if -evaporated, should have left the pores empty and the body pervious to -water. Neither of these however, is the fact; many stratified bodies -are perfectly impervious to water, and few mineral substances contain -water in a liquid state. That they sometimes contain it, chemically -united to them, is no proof of their solidity having been brought -about by that fluid; for such chemical union is as consistent with the -supposition of igneous as of aqueous consolidation, since the region in -which the fire was applied, on every hypothesis must have abounded with -humidity.</p> - -<p>13. Again, if water was the solvent by which the consolidating matter -was introduced into the interstices of the strata, that matter could -consist only of such substances as are soluble in water, whereas -it consists of a vast variety of substances, altogether insoluble -either in it, or in any single menstruum whatsoever. The strata are -consolidated, for example, by quartz, by fluor, by feldspar, and by all -the metals, in their endless -<span class="pagenum" id="Page_18">- 18 -</span> -combinations with sulphureous bodies. To -affirm that water was ever capable of dissolving these substances, is -to ascribe to it powers which it confessedly has not at present; and, -therefore, it is to introduce an hypothesis, not merely gratuitous, but -one which, physically speaking, is absurd and impossible.</p> - -<p>This is not all, however; for, even if this difficulty were to be -passed over, it would still be required to explain, how the water, -which, together with the matter which it held in solution, had -insinuated itself into the pores of the strata, became suddenly -disposed to deposit that matter, and to allow it, by crystallization -or concretion, to assume a solid form.<a id="FNanchor_7" href="#Footnote_7" class="fnanchor">[7]</a> The Neptunists must either -assign a sufficient reason for this great and universal change, or must -expect to see their system treated as an inartificial accumulation -of hypotheses which assigns opposite virtues to the same subject, -and is alike at variance with nature and with itself; in a word, a -system that might pass for the invention of an age, when as yet sound -philosophy had not alighted on the earth, nor taught man that he is -but the minister and interpreter of nature, and can neither extend his -power nor his knowledge -<span class="pagenum" id="Page_19">- 19 -</span> -a hair's-breadth beyond his experience and -observation of the present order of things.<a id="FNanchor_8" href="#Footnote_8" class="fnanchor">[8]</a></p> - -<div class="footnote"> - -<p><a id="Footnote_7" href="#FNanchor_7" class="label">[7]</a> <span class="smcap"><a href="#Note_vi">Note vi.</a></span></p> - -<p><a id="Footnote_8" href="#FNanchor_8" class="label">[8]</a> Homo naturæ minister, et interpres tantùm facit et -intelligit, quantùm de naturæ ordine re, vel mente, observaverit: nec -amplius scit, aut potest.—Nov. Org. lib. i. aph. 1.</p> - -</div> - -<p>14. Such are the more obvious, but I think unanswerable objections, -that may be urged against the aqueous consolidation of the strata. -It is true, that stony concretions, some of them much indurated, are -formed in the humid way under our eyes. Very particular conditions, -however, are required for that purpose, and conditions such as can -hardly have existed at the bottom of the sea. First. The water must -dissolve the substance of which the concretion is to be formed, as it -actually does in the case of calcareous, and in certain circumstances, -in that of siliceous, earth. Secondly. It must be separated from -that substance, as by evaporation, or by a combination of the matter -dissolved with some third substance, to which it has a greater affinity -than to water, so as to form with it an insoluble compound. Lastly, -the water that is deprived of its solution must be carried off, and -more of that which contains the solution must be supplied, as sometimes -happens -<span class="pagenum" id="Page_20">- 20 -</span> -where water runs in a stream, or drops from the roof of a -cavern. The two last conditions are peculiarly inapplicable to the -bottom of the sea, where the state of the surrounding fluid would -neither permit the water that was deprived of its solution from being -drawn off, nor that which contained the solution from succeeding it.</p> - -<p>It is further to be observed, that the consolidation of stalactitical -concretions, that is, the filling up of their pores, is always -imperfect, and is brought about by the repeated action of the fluid -running through the porous mass, and continuing to deposit there -some of the matter it holds in solution. This, which is properly -infiltration, is incompatible with the nature of a fluid, either -nearly, or altogether quiescent.</p> - -<p>15. In order to judge whether objections of equal weight can be opposed -to the hypothesis of igneous consolidation, we must attend to a very -important remark, first made by Dr Hutton, and applied with wonderful -success to explain the most mysterious phenomena of the mineral kingdom.</p> - -<p>It is certain, that the effects of fire on bodies vary with the -circumstances under which it is applied to them, and, therefore, a -considerable allowance must be made, if we would compare -<span class="pagenum" id="Page_21">- 21 -</span> -the operation -of that element when it consolidated the strata, with the results of -our daily experience. The materials of the strata were disposed, as we -have already seen, loose and unconnected, at the bottom of the sea; -that is, even on the most moderate estimation, at the depth of several -miles under its surface. At this depth, and under the pressure of a -column of water of so great a height, the action of heat would differ -much from that which we observe here upon the surface; and, though -our experience does not enable us to compute with accuracy the amount -of this difference, it nevertheless points out the direction in which -it must lie, and even marks certain limits to which it would probably -extend.</p> - -<p>The tendency of an increased pressure on the bodies to which heat is -applied, is to restrain the volatility of those parts which otherwise -would make their escape, and to force them to endure a more intense -action of heat. At a certain depth under the surface of the sea, the -power even of a very intense heat might therefore be unable to drive -off the oily or bituminous parts from the inflammable matter there -deposited, so that, when the heat was withdrawn, these principles -might be found still united to the earthy and carbonic parts, forming -a substance very unlike the residuum -<span class="pagenum" id="Page_22">- 22 -</span> -obtained after combustion under -a pressure no greater than the weight of the atmosphere. It is in -like manner reasonable to believe, that, on the application of heat -to calcareous bodies under great compression, the carbonic gas would -be forced to remain; the generation of quicklime would be prevented, -and the whole might be softened, or even completely melted; which last -effect, though not directly deducible from any experiment yet made, is -rendered very probable, from the analogy of certain chemical phenomena.</p> - -<p>16. An analogy of this kind, derived from a property of the barytic -earth, was suggested by that excellent chemist and philosopher, the -late Dr <span class="smcap">Black</span>. The barytic earth, as is well known, has a -stronger attraction for fixed air than common calcareous earth has, -so that the carbonate of barytes is able to endure a great degree of -heat before its fixed air is expelled. Accordingly, when exposed to an -increasing heat, at a certain temperature, it is brought into fusion, -the fixed air still remaining united to it: if the heat be further -increased, the air is driven off, the earth loses its fluidity, and -appears in a caustic state. Here, it is plain, that the barytic earth, -which is infusible, or very refractory, <i>per se</i>, as well as the -calcareous, owes its fusibility to the presence of the fixed air; and -it is therefore -<span class="pagenum" id="Page_23">- 23 -</span> -probable, that the same thing would happen to the -calcareous earth, if by any means the fixed air were prevented from -escaping when great heat is applied to it. This escape of the fixed -air is exactly what the compression in the subterraneous regions is -calculated to prevent, and therefore we are not to wonder if, among the -calcareous strata, we find marks of actual fusion having taken place.<a id="FNanchor_9" href="#Footnote_9" class="fnanchor">[9]</a></p> - -<div class="footnote"> - -<p><a id="Footnote_9" href="#FNanchor_9" class="label">[9]</a> <span class="smcap"><a href="#Note_vii">Note vii.</a></span></p> - -</div> - -<p>17. These effects of pressure to resist the decomposition, and augment -the fusibility of bodies, being once supposed, we shall find little -difficulty in conceiving the consolidation of the strata by heat, since -the intervals between the loose materials of which they originally -consisted may have been closed, either by the softening of those -materials, or by the introduction of foreign matter among them, in -the state of a fluid, or of an elastic vapour. No objection to this -hypothesis can arise from the considerations stated in the preceding -case; the solvent here employed would want no pores to lodge in after -its work was completed, nor would it find any difficulty in making its -retreat through the densest and most solid substances in the mineral -kingdom. Neither can its incapacity to dissolve the bodies submitted -to its action be alleged. Heat is the most powerful and most general -of all solvents; and, though -<span class="pagenum" id="Page_24">- 24 -</span> -some bodies, such as the calcareous, are -able to resist its force on the surface of the earth, yet, as has just -been shown, it is perfectly agreeable to analogy to suppose, that, -under great pressure, the carbonic state of the lime being preserved, -the purest limestone or marble might be softened, or even melted. -With respect to other substances, less doubt of their fusibility is -entertained; and though, in our experiments, the refractory nature of -siliceous earth has not been completely subdued, a degree of softness -and an incipient fusion have nevertheless been induced.</p> - -<p>Thus it appears, in general, that the same difficulties do not press -against the two theories of aqueous and of igneous consolidation; and, -that the latter employs an agent incomparably more powerful than the -former, of more general activity, and, what is of infinite importance -in a philosophical theory, vastly more definite in the laws of its -operation.</p> - -<p>18. A more particular examination of the different kinds of fossils -will confirm this conclusion, and will show, that, wherever they bear -marks of having been fluid, these marks are such as characterize the -fluidity of fusion, and distinguish it from that which is produced -by solution in a menstruum. Dr Hutton has enumerated many of these -discovered in the course of -<span class="pagenum" id="Page_25">- 25 -</span> -that careful and accurate examination of -fossils, in which he probably never was excelled by any mineralogist. -It will be sufficient here to point out a few of the most remarkable -examples.</p> - -<p>19. Fossil wood, penetrated by siliceous matter, is a substance well -known to mineralogists; it is found in great abundance in various -situations, and frequently in the heart of great bodies of rock. On -examination, the siliceous matter is often observed to have penetrated -the wood very unequally, so that the vegetable structure remains in -some places entire; and in other places is lost in a homogeneous mass -of agate or jasper. Where this happens, it may be remarked, that the -line which separates these two parts is quite sharp and distinct, -altogether different from what must have taken place, had the flinty -matter been introduced into the body of the wood, by any fluid in which -it was dissolved, as it would then have pervaded the whole, if not -uniformly, yet with a regular gradation. In those specimens of fossil -wood that are partly penetrated by agate, and partly not penetrated -at all, the same sharpness of termination may be remarked, and is an -appearance highly characteristic of the fluidity produced by fusion.</p> - -<p>20. The round nodules of flint that are found in chalk, quite insulated -and separate -<span class="pagenum" id="Page_26">- 26 -</span> -from one another, afford an argument of the same kind; -since the flinty matter, if it had been carried into the chalk by any -solvent, must have been deposited with a certain degree of uniformity, -and would not now appear collected into separate masses, without any -trace of its existence in the intermediate parts. On the other hand, if -we conceive the melted flint to have been forcibly injected among the -chalk, and to have penetrated it, somewhat as mercury may, by pressure, -be made to penetrate through the pores of wood, it might, on cooling, -exhibit the same appearances that the chalk-beds of England do actually -present us with.</p> - -<p>The siliceous pudding-stone is an instance closely connected with the -two last; in it we find both the pebbles, and the cement which unites -them, consisting of flint equally hard and consolidated; and this -circumstance, for which it is impossible to account by infiltration, or -the insinuation of an aqueous solvent, is perfectly consistent with the -supposition, that a stream of melted flint has been forcibly injected -among a mass of loose gravel.</p> - -<p>21. The common grit, or sandstone, though it certainly gives no -indication of having possessed fluidity, is strongly expressive of the -effects of heat. It is so, especially in those instances where the -particles of quartzy sand, of -<span class="pagenum" id="Page_27">- 27 -</span> -which it is composed, are firmly and -closely united, without the help of any cementing substance whatsoever. -This appearance, which is very common, seems to be quite inconsistent -with every idea of consolidation, except an incipient fusion, which, -with the assistance of a suitable compression, has enabled the -particles of quartz to unite into stone.</p> - -<p>It has indeed been asserted, that the mere apposition of stony -particles, so as to permit their corpuscular attraction to take place, -was sufficient to form them into stone. To this Dr Hutton has very well -replied, that, admitting the possibility of a hard and firm body being -produced in this way of which, however, we have no proof, the close -and compact texture, the perfect consolidation of the stones we are -now speaking of, would still remain to be explained, and of this it is -evident that the mere apposition of particles, and the force of their -mutual attraction, can afford no solution.</p> - -<p>22. These proofs that the strata must have endured the action of -intense heat, though immediately deduced from those of the siliceous -genus only, extend in reality to all the strata, of every kind, with -which they are found alternated. It is impossible that heat, of the -intensity here supposed, can have acted on a particular -<span class="pagenum" id="Page_28">- 28 -</span> -stratum, and -not on those that are contiguous to it; and, as there are no strata of -any kind with which the quartzy and siliceous are not intermixed, so -there are none of which the igneous consolidation is not thus rendered -probable. We need rest nothing, however, on this argument, as the -fossils of every genus may be shown to speak distinctly for themselves.</p> - -<p>23. Those of the calcareous genus do so perhaps more sparingly than -the rest; yet even among them there are many facts, that, though taken -unconnected with all others, are sufficient to establish the action of -subterraneous fire. Such, for example, are the calcareous breccias, -composed of fragments of marble or limestone, and not only adapted to -each other's shape, but indented into one another, in a manner not -a little resembling the <i>sutures</i> of the human <i>cranium</i>. -From such instances, it is impossible not to infer the softness of -the calcareous fragments when they were consolidated into one mass. -Now, this softness could be induced only by heat; for it must be -acknowledged, that the action of any other solvent is quite inadequate -to the softening of large fragments of stone, without dissolving them -altogether.</p> - -<p>24. In many other instances it appears certain, that the stones -of the calcareous genus have been reduced by heat into a state of -fluidity -<span class="pagenum" id="Page_29">- 29 -</span> -much more perfect. Thus, the saline or finer kinds of marble, -and many others that have a structure highly crystallized, must -have been softened to a degree little short of fusion, before this -crystallization could take place. Even the petrifactions which abound -so much in limestones tend to establish the same fact; for they possess -a sparry structure, and must have acquired that structure in their -transition from a fluid to a solid state.<a id="FNanchor_10" href="#Footnote_10" class="fnanchor">[10]</a></p> - -<div class="footnote"> - -<p><a id="Footnote_10" href="#FNanchor_10" class="label">[10]</a> <span class="smcap"><a href="#Note_viii">Note viii.</a></span></p> - -</div> - -<p>25. In accounting, by the operation of heat, for these appearances -of fluidity, Dr Hutton has proceeded on the principle already laid -down, as conformable to analogy, that calcareous earth, under great -compression, may have its fixed air retained in it, notwithstanding the -action of intense heat, and may, by that means, be reduced into fusion, -or into a state approaching to it. In all this I do not think that he -has departed from the strictest rules of philosophical investigation. -The facts just stated prove, that limestone was once soft, its -fragments retaining at the same time their peculiar form, an effect to -which we know of none similar but those of fire; and, therefore, though -we could not conjecture how heat might be applied to limestone so as -to melt it, instead of reducing it to a calx, we should, nevertheless, -have been forced to -<span class="pagenum" id="Page_30">- 30 -</span> -suppose, that this had actually taken place in the -bowels of the earth; and was a fact which, though we were not able to -explain it, we were not entitled to deny. The principle just mentioned -relieves us therefore from a difficulty, that would have embarrassed, -but could not have overturned, this theory of the earth.</p> - -<p>26. From the arguments which the argillaceous strata afford for the -igneous consolidation of fossils, I shall select one on which Dr Hutton -used to lay considerable stress, and which some of the adversaries of -his system have endeavoured to refute. This argument is founded on -the structure of certain ironstones called <i>septaria</i>, often met -with among the argillaceous schistus, particularly in the vicinity of -coal. These stones are usually of a lenticular or spheroidal form, and -are divided in their interior into distinct <i>septa</i>, by veins -of calcareous spar, of which one set are circular and concentric, -the other rectilineal; diverging from the centre of the former, and -diminishing in size as they recede from it. Now, what is chiefly to be -remarked is, that these veins terminate before they reach the surface -of the stone; so that the matter with which they are filled cannot -have been introduced from without by infiltration, or in any other way -whatsoever. The only other supposition, therefore, that is left for -explaining the singular structure -<span class="pagenum" id="Page_31">- 31 -</span> -of this fossil, is, that the whole -mass was originally fluid, and that, in cooling, the calcareous part -separated from the rest, and afterwards crystallized.</p> - -<p>27. It has been urged against this theory of the septaria, that these -stones are sometimes found with the calcareous veins extending all -the way to the circumference, and of course communicating with the -outside. But it must be observed, that this fact does not affect the -argument drawn from specimens in which no such communication takes -place. It is at best only an ambiguous instance, that may be explained -by two opposite theories, and may be reconciled either to the notion -of igneous or of aqueous consolidation: but if there is a single close -septarium in nature, it can, of course, be explained only by one of -these theories, and the other must, of necessity, be rejected. Besides, -it is plain, that a close septarium can never have been open, though an -open septarium may very well have been close; and indeed, as this stone -is, in certain circumstances, subject to perpetual exfoliation, it -would be wonderful if no one was ever found with the calcareous veins -reaching to the surface. With regard to the light, therefore, that they -give into their own history, these two kinds of septaria are by no -means on an equal footing; and this may serve to show, how -<span class="pagenum" id="Page_32">- 32 -</span> -necessary -it is, in all inductive reasoning, and particularly in a subject so -complex as geology, to separate with care such phenomena as admit of -two solutions, from such as admit only of one.</p> - -<p>28. The bituminous strata come next to be considered; and they are of -great consequence in the present argument, because their dissimilarity -in so many particulars to all other mineral substances, renders them -what Lord Bacon calls an <i>instantia singularis</i>, having the -first rank among facts subservient to inductive investigation. But -though unlike in substance to other fossils, and composed, as has -been shown, of materials that belonged not originally to the mineral -kingdom, they agree in many material circumstances with the strata -already enumerated. Their beds are disposed in the same manner, and -are alternated indiscriminately with those of all the secondary rocks, -and, being formed in the same region, must have been subject to the -same accidents, and have endured the operation of the same causes. -They are traversed too like the other strata, by veins of the metals, -of spars, of basaltes, and of other substances; and, whatever argument -may hereafter be derived from this to prove the action of fire on the -strata so traversed, is as much applicable to coal as to any other -mineral. The coal strata -<span class="pagenum" id="Page_33">- 33 -</span> -also contain pyrites in great abundance, a -substance that is perhaps, more than any other, the decided progeny of -fire. This compound of metal and sulphur, which is found in mineral -bodies of every kind, I believe, without any exception, is destroyed -by the contact of moisture, and resolved into a vitriolic salt. At -the same time it is found in the strata, not traversing them in -veins, which may be supposed of more recent formation than the strata -themselves; but existing in the heart of the most solid rocks, often -nicely crystallized, and completely inclosed, on all sides, without the -most minute vacuity. The pyrites must have been present, therefore, -when the strata were consolidated, and it is inconceivable, if their -consolidation was brought about in the wet way, that a substance -should be so generally found in them, the very existence of which is -incompatible with humidity. This argument for the igneous origin of the -strata is applicable to them all, but especially to those of coal, as -abounding with pyrites more than any other.</p> - -<p>29. The difficulty that here naturally present itself, viz. how -vegetable matter, such as coal is supposed to have been, could be -exposed to the action of intense heat, without being deprived of its -inflammable part, is obviated by the principle formerly explained -concerning the effects -<span class="pagenum" id="Page_34">- 34 -</span> -of compression. The weight incumbent on -the strata of coal, when they were exposed to the intense heat of -the mineral regions, may have been such as to retain the oily and -bituminous, as well as sulphureous parts, though the whole was reduced -almost to fusion; and thus, on cooling, the sulphur uniting with iron -might crystallize, and assume the form of pyrites.</p> - -<p><a id="sec_30"></a>30. The compression, however, has not in every instance preserved the -bituminous, in union with the carbonic part of coal; and hence a mark -of the operation of fire quite peculiar to this fossil, and found in -those infusible kinds of it which contain no bitumen, and burn without -flame. These resemble, some of them very precisely, and all them in a -great degree, the products obtained by the distillation of the common -bituminous coal that is, they consist of charcoal, united to an earthy -basis in different proportions. It is natural therefore to conclude, -that this substance was prepared in the mineral regions by the action -of heat, which, in some instances, has driven off the inflammable part -of the coal. That the heat should, in some cases, have done so, is not -inconsistent with the general effect attributed to compression. The -conditions necessary for retaining the more volatile parts, may not -have been present every where in the same degree, -<span class="pagenum" id="Page_35">- 35 -</span> -so that the latter, -though they could not escape, may have been forced from one part of a -stratum, or body of strata, to another.</p> - -<p>31. In confirmation of this it must be observed, that, as the fixed -part of coal is thus found in the bowels of the earth, separate from -the volatile or bituminous, so, in the neighbourhood of coal strata, -the latter is sometimes found without any mixture of the former. The -fountains of naphtha and petroleum are well known; and Dr Hutton -has described a stratum of limestone, lying in the centre of a coal -country, which is pervaded and tinged by bituminous matter, through -its whole mass, and has, at the same time, many close cavities in -the heart of it, lined with calcareous spar, and containing fossil -pitch, sometimes in large pieces, sometimes in hemispherical drops, -scattered over the surface of the cavities. This combination could -only be effected by a part of the inflammable matter of the beds of -coal underneath, being driven off by heat, and made to penetrate the -limestone, while it was yet soft and pervious to heated vapours.<a id="FNanchor_11" href="#Footnote_11" class="fnanchor">[11]</a></p> - -<div class="footnote"> - -<p><a id="Footnote_11" href="#FNanchor_11" class="label">[11]</a> <span class="smcap"><a href="#Note_ix">Note ix.</a></span></p> - -</div> - -<p>32. Hitherto we have enumerated those fossils that are either not at -all, or very sparingly soluble in water. There are, however, saline -<span class="pagenum" id="Page_36">- 36 -</span> -bodies among the mineral strata, such for instance as rock-salt, which -are readily dissolved in water; and it yet remains to examine by what -cause their consolidation has been effected.</p> - -<p>Here the theorists who consider water as the sole agent in the -mineralization of fossils, are indeed delivered from one difficulty, -but it is only that they may be harder pressed on by another. It -cannot now be said, that the menstruum which they employ is incapable -of dissolving the substances exposed to its action, as in the case of -metallic or stony bodies; but it may very well be asked, how the water -came to deposit the salts which it held in solution, and to deposit -them so copiously as it has done in many places, without any vestige -of similar deposition in the places immediately contiguous. If they -refuse to call to their assistance any other than their favourite -element, they will not find it easy to answer this question, and must -feel the embarrassment of a system, subject to two difficulties, so -nicely, but so unhappily adjusted, that one of them is always prepared -to act whenever the other is removed. If, on the other hand, they will -admit the operation of subterraneous heat, it appears possible, that -the local application of such -<span class="pagenum" id="Page_37">- 37 -</span> -heat may have driven the water, in -vapour, from one place to another, and by such action often repeated in -the same spot, may have produced those great accumulations of saline -matter, that are actually found in the bowels of the earth.</p> - -<p>33. But granting that, either in the way just pointed out, or in some -other that is unknown, the salt and the water have been separated, -some further action of heat seems requisite, before a compact, and -highly indurated body, like rock-salt, could be produced. The mere -precipitation of the salt, would, as Dr Hutton has observed, form only -an assemblage of loose crystals at the bottom of the sea, without -solidity or cohesion: and to convert such a mass into a firm and solid -rock, would require the application of such heat as was able to reduce -it into fusion. The consolidation of rock-salt, therefore, however its -separation from the water is accounted for, cannot be explained but on -the hypothesis of subterraneous heat.</p> - -<p>34. Some other phenomena that have been observed in salt mines, come -in support of the same conclusion. The salt rock of Cheshire, which -lies in thick beds, interposed between strata of an argillaceous or -marly stone, and is itself mixed with a considerable portion of the -same earth, exhibits a very great peculiarity in its structure. Though -it forms a mass extremely -<span class="pagenum" id="Page_38">- 38 -</span> -compact, the salt is found to be arranged -in round masses of five or six feet in diameter, not truly spherical, -but each compressed by those that surround it, so as to have the shape -of an irregular polyhedron. These are formed of concentric coats, -distinguishable from one another by their colour, that is, probably -by the greater or less quantity of earth which they contain, so that -the roof of the mine, as it exhibits a horizontal section of them, -is divided into polygonal figures, each with a multitude of polygons -within it, having altogether no inconsiderable resemblance to a -<i>mosaic</i> pavement. In the triangular spaces without the polygons, -the salt is in coats parallel to the sides of the polygons.</p> - -<p>The circumstances which gave rise to this singular structure we should -in vain endeavour to define; yet some general conclusions concerning -them seem to be within our reach. It is clear that the whole mass of -salt was fluid at once, and that the forces, whatever they were, which -gave solidity to it, and produced the new arrangement of its particles, -were all in action at the same time. The uniformity of the coated -structure is a proof of this, and, above all, the compression of the -polyhedra, which is always mutual, the flat side of one being turned to -the flat side of another, and never an angle to an angle, nor an angle -to a side. The coats formed as it -<span class="pagenum" id="Page_39">- 39 -</span> -were round so many different centres -of attraction, is also an appearance quite inconsistent with the notion -of deposition; both these, however, are compatible with the notion of -solidity acquired by the refrigeration of a fluid, where the whole -mass is acted on at the same time, and where no solvent remains to be -disposed of after the induration of the rest.</p> - -<p>35. Another species of fossil salt exhibits appearances equally -favourable to the theory of igneous consolidation. This is the Trona of -Africa, which is no other than soda, or mineral alkali, in a particular -state. The specimen of this fossil in Dr Black's, now Dr Hope's, -collection, is of a sparry and radiated structure, and is evidently -part of the contents of a vein, having a stony crust adhering to it, -on one side, with its own sparry structure complete, on the opposite. -It contains but about one sixth of the water of crystallization -essential to this salt when obtained in the humid way; and, what is -particularly to be remarked, it does not lose this water, nor become -covered with a powder, like the common alkali, by simple exposure to -the air. It is evident, therefore, that this fossil does not originate -from mere precipitation; and when we add, that in its sparry structure -it contains evident marks of having once been fluid, we have -<span class="pagenum" id="Page_40">- 40 -</span> little -reason to entertain much doubt concerning the principle of its -consolidation.</p> - -<p>Thus, then, the testimony given to the operation of fire, or heat, -as the consolidating power of the mineral kingdom, is not confined -to a few fossils, but is general over all the strata. How far the -unstratified fossils agree in supporting the same conclusion, will be -afterwards examined.</p> - - -<p class="caption3nb" id="sect1p3">3. <i>Position of the Strata.</i><span class="smaller"><a id="FNanchor_12" href="#Footnote_12" class="fnanchor">[12]</a></span></p> - -<div class="footnote"> - -<p><a id="Footnote_12" href="#FNanchor_12" class="label">[12]</a> Theory of the Earth, vol. i. p. 120.</p> - -</div> - -<p>36. We have seen of what materials the strata are composed, and by -what power they have been consolidated; we are next to inquire, from -what cause it proceeds, that they are now so far removed from the -region which they originally occupied, and wherefore, from being all -covered by the ocean, they are at present raised in many places fifteen -thousand feet above its surface. Whether this great change of relative -place can be best accounted for by the depression of the sea, or the -elevation of the strata themselves, remains to be considered.</p> - -<p><span class="pagenum" id="Page_41">- 41 -</span></p> - -<p>Of these two suppositions, the former, at first sight, seems -undoubtedly the most probable, and we feel less reluctance to suppose, -that a fluid, so unstable as the ocean, has undergone the great -revolution here referred to, than that the solid foundations of the -land have moved a single fathom from their place. This, however, is a -mere illusion. Such a depression of the level of the sea as is here -supposed, could not happen without a change proportionally great in the -solid part of the globe; and, though admitted as true, will be found -very inadequate to explain the present condition of the strata.</p> - -<p><a id="sec_37"></a>37. Supposing the appearances which clearly indicate submersion under -water to reach no higher than ten thousand feet above the present level -of the sea, and of course the surface of the sea to have been formerly -higher by that quantity than it is now; it necessarily follows, that -a bulk of water has disappeared, equal to more than a seven hundredth -part of the whole magnitude of the globe.<a id="FNanchor_13" href="#Footnote_13" class="fnanchor">[13]</a> The existence of empty -caverns of extent sufficient to contain this vast body of water, and of -such a convulsion as to lay them open, and give room to the retreat of -the sea, are suppositions which a philosopher could only be justified -in admitting, if they promised to furnish a very complete explanation -of -<span class="pagenum" id="Page_42">- 42 -</span> -appearances. But this justification is entirely wanting in the -present case; for the retreat of the ocean to a lower level, furnishes -a very partial and imperfect explanation of the phenomena of geology. -It will not explain the numberless remains of ancient continents that -are involved, as we have seen, in the present, unless it be supposed -that the ancient ocean, though it rose to so great a height, had -nevertheless its shores, and was the boundary of land still higher than -itself. And, as to that which is now more immediately the object of -inquiry, the position of the strata, though the above hypothesis would -account in some sort for the change of their place, relatively to the -level of the sea; yet, if it shall be proved, that the strata have -changed their place relatively to each other, and relatively to the -plane of the horizon, so as to have had an angular motion impressed on -them, it is evident that, for these facts, the retreat of the sea does -not afford even the shadow of a theory.</p> - -<div class="footnote"> - -<p><a id="Footnote_13" href="#FNanchor_13" class="label">[13]</a> <span class="smcap"><a href="#Note_x">Note x.</a></span></p> - -</div> - -<p><a id="sec_38"></a>38. Now, it is certain, that many of the strata have been moved -angularly, because that, in their original position, they must have -been all nearly horizontal. Loose materials, such as sand and gravel -subsiding at the bottom of the sea, and having their interstices filled -with water, possess a kind of fluidity: they are disposed to -<span class="pagenum" id="Page_43">- 43 -</span> -yield -on the side opposite to that where the pressure is greatest, and are -therefore, in some degree, subject to the laws of hydrostatics. On -this account they will arrange themselves in horizontal layers; and -the vibrations of the incumbent fluid, by impressing slight motion -backward, and forward, on the materials of these layers, will very much -assist the accuracy of their level.</p> - -<p>It is not, however, meant to deny, that the form of the bottom might -influence, in a certain degree, the stratification of the substances -deposited on it. The figure of the lower beds deposited on an uneven -surface, would necessarily be affected by two causes; the inclination -of that surface, on the one hand, and the tendency to horizontality, -on the other; but, as the former cause would grow less powerful as the -distance from the bottom increased, the latter cause would finally -prevail, so that the upper beds would approach to horizontally, and the -lower would neither be exactly parallel to them, nor to one another. -Whenever, therefore, we meet with rocks, disposed in layers quite -parallel to one another, we may rest assured, that the inequalities of -the bottom have had no effect, and that no cause has interrupted the -statical tendency above explained.</p> - -<p><span class="pagenum" id="Page_44">- 44 -</span></p> - -<p>Now, rocks having their layers exactly parallel, are very common, and -prove their original horizontally to have been more precise than we -could venture to conclude from analogy alone. In beds of sandstone, -for instance, nothing is more frequent than to see the thin layers of -sand, separated from one another by layers still finer of coaly, or -micaceous matter, that are almost exactly parallel, and continue so to -a great extent without any sensible deviation. These planes can have -acquired their parallelism only in consequence of the property of water -just stated, by which it renders the surfaces of the layers, which it -deposits, parallel to its own surface, and therefore parallel to one -another. Though such strata, therefore, may not now be horizontal, they -must have been so originally; otherwise it is impossible to discover -any cause for their parallelism, or any rule by which it can have been -produced.</p> - -<p>39. This argument for the original horizontality of the strata, -is applicable to those that are now farthest removed from that -position. Among such, for instance, as are highly inclined, or even -quite vertical, and among those that are bent and incurvated in the -most fantastical manner, as happens more especially in -<span class="pagenum" id="Page_45">- 45 -</span> -the primary -schisti, we observe, through all their sinuosities and inflections, -an equality of thickness and of distance among their component -laminæ. This equality could only be produced by those laminæ having -been originally spread out on a flat and level surface, from which -situation, therefore, they must afterwards have been lifted up by the -action of some powerful cause, and must have suffered this disturbance -while they were yet in a certain degree flexible and ductile. Though -the primary direction of the force which thus elevated them must have -been from below upwards, yet it has been so combined with the gravity -and resistance of the mass to which it was applied, as to create a -lateral and oblique thrust, and to produce those contortions of the -strata, which, when on the great scale, are among the most striking and -instructive phenomena of geology.</p> - -<p>40. Great additional force is given to this argument, in many cases, by -the nature of the materials of which the stratified rocks are composed. -The beds of breccia and pudding-stone, for instance, are often in -planes almost vertical, and, at the same time, contain gravel-stones, -and other fragments of rock, of such a size and weight, that they -could not remain in their present -<span class="pagenum" id="Page_46">- 46 -</span> -position an instant, if the cement -which unites them were to become soft; and therefore they certainly -had not that position at the time when this cement was actually soft. -This remark has been made by mineralogists who were not led to it by -any system. The judicious and indefatigable observer of the Alps, -describing the pudding-stone of Valorsine, near the sources of the -Arve, tells us, that he was astonished to find it in beds almost -vertical, a situation in which it could not possibly have been formed. -"That particles," he adds, "of extreme tenuity, suspended in a fluid, -might become agglutinated, and form vertical beds, is a thing that -may be conceived; but that pieces of stone, of several pounds weight, -should have rested on the side of a perpendicular wall, till they were -enveloped in a stony cement, and united into one mass, is a supposition -impossible and absurd. It should be considered, therefore, as a thing -demonstrated, that this pudding-stone was formed in a horizontal -position, or one nearly such, and elevated after its induration. We -know not," he continues, "the force by which this elevation has been -effected; but it is an important step among the prodigious number of -vertical beds that are to be met with in the Alps, to have found some -<span class="pagenum" id="Page_47">- 47 -</span> -that must certainly have been formed in a horizontal situation."<a id="FNanchor_14" href="#Footnote_14" class="fnanchor">[14]</a></p> - -<div class="footnote"> - -<p><a id="Footnote_14" href="#FNanchor_14" class="label">[14]</a> Voyages aux Alpes, tom. ii § 690.</p> - -</div> - -<p>41. Nothing can be more sound and conclusive than this reasoning; and -had the ingenious author pursued it more systematically, it must have -led him to a theory of mountains very little different from that which -we are now endeavouring to explain. If some of the vertical strata are -proved to have been formed horizontally, there can be no reason for -not extending the same conclusion to them all, even if we had not the -support of the argument from the parallelism of the layers, which has -been already stated.</p> - -<p>42. The highly inclined position, and the manifold inflections of the -strata, are not the only proofs of the disturbance that they have -suffered, and of the violence with which they have been forced up from -their original place. Those interruptions of their continuity which -are observed, both at the surface and under it, are evidences of the -same fact. It is plain, that if they remained now in the situation -in which they were at first deposited, they would never appear to -be suddenly broken off. No stratum would terminate abruptly; but, -however its nature -<span class="pagenum" id="Page_48">- 48 -</span> -and properties might change, it would constitute -an entire and continued rock, at least where the effects of waste and -<i>detritus</i> had not produced a separation. This, however, is very -far from being the actual condition of stratified bodies. Those that -are much inclined, or that make considerable angles with the horizontal -plane, must terminate abruptly where they come up to the surface. Their -doing so is a necessary consequence of their position, and furnishes no -argument, it may be said, for their having been disturbed, different -from that which has been already deduced from their inclination. There -are, however, instances of a breach of continuity in the strata, under -the surface, that afford a proof of the violence with which they have -been displaced, different from any hitherto mentioned. Of this nature -are the <i>slips</i> or <i>shifts</i>, that so often perplex the miner -in his subterraneous journey, and which change at once all those lines -and bearings that had hitherto directed his course. When his mine -reaches a certain plane, which is sometimes perpendicular, sometimes -oblique to the horizon, he finds the beds of rock broken asunder, those -on the one side of the plane having changed their place, by sliding in -a particular direction along the face of the others. In this motion -they have sometimes preserved their parallelism, that is, the strata -<span class="pagenum" id="Page_49">- 49 -</span> -on one side of the <i>slip</i> continue parallel to those on the other; -in other cases, the strata on each side become inclined to one another, -though their identity is still to be recognized by their possessing the -same thickness, and the same internal characters. These <i>shifts</i> -are often of great extent, and must be measured by the quantity of -the rock moved, taken in conjunction with the distance to which it -has been carried. In some instances, a vein is formed at the plane of -the shift or slip, filled with materials of the kinds which will be -hereafter mentioned; in other instances, the opposite sides of the rock -remain contiguous, or have the interval between them filled with soft -and unconsolidated earth. All these are the undeniable effects of some -great convulsion, which has shaken the very foundations of the earth; -but which, far from being a disorder in nature, is part of a regular -system, essential to the constitution and economy of the globe.</p> - -<p>The production of the appearances now described, belongs, without -doubt, to different periods of time; and, where slips intersect one -another, we can often distinguish the less from the more ancient They -are all, however, of a date posterior to that at which the waving and -undulated forms of the strata were acquired, as they do not carry with -them any marks of -<span class="pagenum" id="Page_50">- 50 -</span> -the softness of the rock, but many of its complete -induration.</p> - -<p>The same phenomenon which is thus exemplified on a great scale in -the bowels of the earth, is often most beautifully exhibited in -single specimens of stone, and is accompanied with this remarkable -circumstance, that the <i>integrity</i> of the stone is not destroyed -by the shifts, whatever wounds had been made in it being healed, and -the parts firmly reunited to one another.<a id="FNanchor_15" href="#Footnote_15" class="fnanchor">[15]</a></p> - -<div class="footnote"> - -<p><a id="Footnote_15" href="#FNanchor_15" class="label">[15]</a> <span class="smcap"><a href="#Note_xi">Note xi.</a></span></p> - -</div> - -<p>43. Though such marks of violence as have been now enumerated are -common in some degree to all the strata, they abound most among the -primary, and point out these as the part of our globe which has been -exposed to the greatest vicissitudes. At their junction with the -secondary, or where they emerge, as it were, from under the latter, -phenomena occur, which mark some of those vicissitudes with astonishing -precision; phenomena of which the nature was first accurately explored, -and the consequences fully deduced, by the geologist whose system I am -endeavouring to explain. He observed, in several instances, that where -the primary schistus rises in beds almost vertical, it is covered by -horizontal layers of secondary sandstone, which last are penetrated by -the irregular -<span class="pagenum" id="Page_51">- 51 -</span> -tops of the schistus, and also involve fragments of that -rock, some angular, others round and smooth, as if worn by attrition. -From this he concluded, that the primary strata, after being formed at -the bottom of the sea, in planes nearly horizontal, were raised, so as -to become almost vertical, while they were yet covered by the ocean, -and before the secondary strata had begun to be deposited on them. He -also argued, that, as the fragments of the primary rock, included in -the secondary, are many of them rounded and worn, the deposition of -the latter must have been separated from the elevation of the former -by such an interval of time, as gave room for the action of waste and -decay, allowing those fragments first to be detached, and afterwards -wrought into a round figure.<a id="FNanchor_16" href="#Footnote_16" class="fnanchor">[16]</a></p> - -<div class="footnote"> - -<p><a id="Footnote_16" href="#FNanchor_16" class="label">[16]</a> <span class="smcap"><a href="#Note_xii">Note xii.</a></span></p> - -</div> - -<p>44. Indeed, the interposition of a breccia between the primary and -secondary strata, in which the fragments, whether round or angular, -are always of the primary rock, is a fact so general, and the quantity -of this breccia is often so great, that it leads to a conclusion more -paradoxical than any of the preceding, but from which, nevertheless, -it seems very difficult to withhold assent. Round gravel, when in -great abundance, agreeably to a remark already made, must necessarily -be considered as a production -<span class="pagenum" id="Page_52">- 52 -</span> -peculiar to the beds of rivers, or -the shores of continents, and as hardly ever formed at great depths -under the surface of the sea. It should seem, then, that the primary -schistus, after attaining its erect position, had been raised up to -the surface, where this gravel was formed; and from thence had been -let down again to the depths of the ocean, where the secondary strata -were deposited on it. Such alternate elevations and depressions of the -bottom of the sea, however extraordinary they may seem, will appear to -make a part of the system of the mineral kingdom, from other phenomena -hereafter to be described.</p> - -<p>45. On the whole, therefore, by comparing the actual position of the -strata, their erectness, their curvature, the interruptions of their -continuity, and the transverse stratification of the secondary in -respect of the primary, with the regular and level situation which -the same strata must have originally possessed, we have a complete -demonstration of their having been disturbed, torn asunder, and moved -angularly, by a force that has, in general, been directed from below -upwards. In establishing this conclusion, we have reasoned more from -the facts which relate to the <i>angular elevation</i> of the strata, -than from those which relate to their <i>absolute elevation</i>, or -their translation to a greater -<span class="pagenum" id="Page_53">- 53 -</span> -distance from the centre of the earth. -This has been done, because the appearances, which respect the absolute -lifting up of the strata are more ambiguous than those, which respect -the change of their angular position. The former might be accounted -for, could they be separated from the latter, in two ways, viz. either -by the retreat of the sea, or the raising up of the land; but the -latter can be explained only in one way, and force us of necessity to -acknowledge the existence of an expanding power, which has acted on the -strata with incredible energy, and has been directed from the centre -toward the circumference.</p> - -<p>46. When we are assured of the existence of such a power as this in the -mineral regions, we should argue with singular inconsistency, if we did -not ascribe to it all the other appearances of motion in those regions, -which it is adequate to produce. If nature in her subterraneous abodes -is provided with a force that could burst asunder the massy pavement -of the globe, and place the fragments upright upon their edges, could -she not, by the same effort, raise them from the greatest depths of the -sea, to the highest elevation of the land? The cause that is adequate -to one of these effects is adequate to them both together; for it is a -principle well known in mechanical philosophy, that the force which -<span class="pagenum" id="Page_54">- 54 -</span> -produces a parallel motion, may, according to the way in which it is -applied, produce also an angular motion, without any diminution of the -former effect. It would, therefore, be extremely unphilosophical to -suppose, that any other cause has changed the relative level of the -strata, and the surface of the sea, than that which has, in so many -cases, raised the strata from a horizontal to a highly inclined, or -even vertical situation: it would be to introduce the action of more -causes than the phenomena require, and to forget, that nature, whose -operations we are endeavouring to trace, combines the possession of -infinite resources with the most economical application of them.</p> - -<p>47. From all, therefore, that relates to the position of the strata, I -think I am justified in affirming, that their disturbance and removal -from the place of their original formation, by a force directed -from below upwards, is a fact in the natural history of the earth, -as perfectly ascertained as any thing which is not the subject of -immediate observation. As to the power by which this great effect has -been produced, we cannot expect to decide with equal evidence, but must -be contented to pass from what is certain to what is probable. We may, -then, remark, that of the forces in nature to which our experience -does in any degree extend, -<span class="pagenum" id="Page_55">- 55 -</span> -none seems so capable of the effect we -would ascribe to it, as the expansive power of heat; a power to which -no limits can be set, and one, which, on grounds quite independent of -the elevation of the strata, has been already concluded to act with -great energy in the subterraneous regions. We have, indeed, no other -alternative, but either to adopt this explanation, or to ascribe the -facts in question to some secret and unknown cause, though we are -ignorant of its nature, and have no evidence of its existence.</p> - -<p>We are therefore to suppose, that the power of the same subterraneous -heat, which consolidated and mineralized the strata at the bottom of -the sea, has since raised them up to the height at which they are now -placed, and has given them the various inclinations to the horizon -which they are found actually to possess.</p> - -<p>48. The probability of this hypothesis will appear greatly increased, -when it is considered, that, besides those now enumerated, there are -other indications of movement among the bodies of the mineral kingdom, -where effects of heat more characteristic than simple expansion are -clearly to be discovered. Thus, on examining the marks of disorder -and movement which are found among the strata, it cannot fail to be -observed, that notwithstanding -<span class="pagenum" id="Page_56">- 56 -</span> -the fracture and dislocation, of which -they afford so many examples, there are few empty spaces to be met -with among them, as far as our observation extends. The breaches and -separations are numerous, and distinct; but they are, for the most -part, completely filled up with minerals of a kind quite different -from the rock on each side of them, and remarkable for containing -no vestiges of stratification. We are thus led to consider the -unstratified minerals, the second of the divisions into which the whole -mineral kingdom, viewed geologically, ought to be distinguished. These -minerals are immediately connected with the disturbance of the strata, -and appear, in many instances, to have been the instruments of their -elevation.</p> - - -<hr class="chap x-ebookmaker-drop" /> - -<div class="chapter"> -<p><span class="pagenum" id="Page_57">- 57 -</span></p> - -<h2 class="nobreak" id="SECTION_II">SECTION II.</h2> -</div> - -<p class="caption3nb">OF THE PHENOMENA PECULIAR TO UNSTRATIFIED BODIES.</p> - - -<p class="caption3nb" id="sect2p1">1. <i>Metallic Veins.</i></p> - -<div class="fl_left"> -<span class="num_left">49.</span> <span class="vbig">T</span> -</div> - -<p><a id="sec_49"></a><span class="hidden">49. T</span>HE unstratified minerals exist either in veins, intersecting -the stratified, or in masses surrounded by them. Veins are of various -kinds, and may in general be defined, separations in the continuity of -a rock, of a determinate width, but extending indefinitely in length -and depth, and filled with mineral substances, different from the rock -itself. The mineral veins, strictly so called, are those filled with -crystallized substances, and containing the metallic ores.</p> - -<p>That these veins are of a formation subsequent to the hardening and -consolidation of the strata which they traverse, is too obvious to -require any proof; and it is no less clear, from the crystallized -and sparry structure of the substances contained in them, that these -substances must have concreted from a fluid state. Now, that this -fluidity was simple, like that of fusion by heat, and not compound, -like that of solution in a menstruum, is inferred from many phenomena. -It is inferred from the acknowledged -<span class="pagenum" id="Page_58">- 58 -</span> -insolubility of the substances -that fill the veins, in any one menstruum whatsoever; from the total -disappearance of the solvent, if there was any; from the complete -filling up of the vein by the substances which that solvent had -deposited; from the entire absence of all the appearances of horizontal -or gradual deposition; and, lastly, from the existence of close -cavities, lined with crystals, and admitting no egress to any thing but -heat.</p> - -<p>50. To the same effect may be mentioned those groups of crystals -composed of substances the most different, that are united in the same -specimen, all intersecting and mutually impressing one another. These -admit of being explained, on the supposition that they were originally -in fusion, and became solid by the loss of heat; a cause that acted -on them all alike, and alike impelled them to crystallize: But the -appearances of simultaneous crystallization seem incompatible with the -nature of deposition from a solvent, where, with respect 16 different -substances, the effects must take place slowly, and in succession.</p> - -<p>51. The metals contained in the veins which we are now treating of, -appear very commonly in the form of an ore, mineralized by sulphur. -Their union with this latter substance can be produced, as we know, by -heat, but hardly by the way of solution in a menstruum, and certainly -<span class="pagenum" id="Page_59">- 59 -</span> -not at all, if that menstruum is nothing else than water. The metals, -therefore, when mineralized by sulphur, give no countenance to the -hypothesis of aqueous solution; and still less do they give any when -they are found native, as it is called, that is, malleable, pure -and uncombined with any other substance. The great masses of native -iron found in Siberia and South America are well known; and nothing -certainly can less resemble the products of a chemical precipitation. -Gold, however, the most perfect of the metals, is found native most -frequently; the others more rarely, in proportion nearly to the -facility of their combination with sulphur. Of all such specimens it -may be safely affirmed, that if they have ever been fluid, or even -soft, they must have been so by the action of heat; for, to suppose -that a metal has been precipitated, pure and uncombined from any -menstruum, is to trespass against all analogy, and to maintain a -physical impossibility. But it is certain, that many of the native -metals have once been in a state of softness, because they bear on them -impressions which they could not have received but when they were soft. -Thus, gold is often impressed by quartz and other stones, which still -adhere to it, or are involved in it. Specimens of quartz, containing -gold and silver shooting through -<span class="pagenum" id="Page_60">- 60 -</span> -them, with the most beautiful and -varied ramifications, are every where to be met with in the cabinets of -the curious; and contain, in their structure, the clearest proof, that -the metal and the quartz have been both soft, and have crystallized -together. By the compactness, also, of the body which they form, they -show, that when they acquired solidity, it was by the concretion of the -whole mass, and not by such partial concretion as takes place when a -solvent is separated from substances which it held in solution.</p> - -<p>52. Native copper is very abundant; and some specimens of it have been -found crystallized. Here the crystallization of the metal is a proof -that it has passed from a fluid to a solid state; and its purity is a -proof that it did not make that transition by being precipitated from a -menstruum.</p> - -<p>53. Again, pieces of native manganese have been found possessing so -exactly the characters peculiar to that metal when reduced in our -furnaces, that it is impossible to consider them as deriving their -figure and solidity from any cause but fusion. The ingenious author -who describes these specimens, La Peyrouse, was so forcibly struck -with this resemblance, that he immediately drew the same conclusion -from it which is drawn here, attributing the only difference, -<span class="pagenum" id="Page_61">- 61 -</span> -which he remarked between the native and the artificial <i>regulus</i>, to -the different energy with which the same agent works when employed by -nature and by art.<a id="FNanchor_17" href="#Footnote_17" class="fnanchor">[17]</a></p> - -<div class="footnote"> - -<p><a id="Footnote_17" href="#FNanchor_17" class="label">[17]</a> Theory of the Earth, vol. i. p. 68. Journal de Phys. -Janvier, 1786.</p> - -</div> - -<p>54. All these appearances conspire to prove, that the materials which -fill the mineral veins were melted by heat, and forcibly injected, in -that state, into the clefts and fissures of the strata. These fissures -we must conceive to have arisen, not merely from the shrinking of the -strata while they acquired hardness and solidity, but from the violence -done to them, when they were heaved up and elevated in the manner which -has already been explained.<a id="FNanchor_18" href="#Footnote_18" class="fnanchor">[18]</a></p> - -<div class="footnote"> - -<p><a id="Footnote_18" href="#FNanchor_18" class="label">[18]</a> <span class="smcap"><a href="#Note_xiii">Note xiii.</a></span></p> - -</div> - -<p><a id="sec_55"></a>55. When these suppositions are once admitted, the other leading facts -in the history of metallic veins will be readily accounted for. Thus, -for instance, it is evident to what we must ascribe the fragments of -the surrounding rock that are often found immersed in the veins, and -encompassed on all sides by crystallized substances. These fragments -being no doubt detached by the concussion, which at once tore asunder -and elevated the strata, were sustained by the melted matter that -flowed at the same time upward -<span class="pagenum" id="Page_62">- 62 -</span> -through the vein. Large masses of rock -are often found in this manner completely insulated; one of these, -which M. De Luc has described with great accuracy, is no less than a -vast segment of a mountain.<a id="FNanchor_19" href="#Footnote_19" class="fnanchor">[19]</a></p> - -<div class="footnote"> - -<p><a id="Footnote_19" href="#FNanchor_19" class="label">[19]</a> Lettres Physiques, &c. tom. iii. P. 361.</p> - -</div> - -<p><a id="sec_56"></a>56. The immense violence which has accompanied the formation of mineral -veins, is particularly marked by the slips and shifts of the strata on -each side of them all tending to show what mighty changes have taken -place in those regions, which our imagination erroneously paints as -the abode of everlasting silence and rest. This shifting of the strata -is best observed, where the veins make a transverse section of beds of -rock, considerably inclined to the horizon. There it is common to see -the beds on one side of the vein slipped along from the corresponding -beds on the other side, and removed sometimes in a horizontal, -sometimes in an oblique direction. In this way, not only the strata -are shifted, but veins, which intersect one another, are also shifted -themselves. They are <i>heaved</i>, as it is called in the significant -language of the miners, and forced out of their direction. It is -impossible, in such a case, but to connect in the mind the formation -<span class="pagenum" id="Page_63">- 63 -</span> -of the vein, and the production of the slips which accompany it, and to -regard them as parts of the same phenomenon.</p> - -<p>57. Where these slips are horizontal, and exhibit great bodies of -strata carried from their place, while the parts of the transferred -mass remain undisturbed relatively to one another, they furnish a dear -proof, that this change of plaice has not arisen from the falling in -of the roofs of caverns, as some geologists suppose. The horizontal -direction, and the regularity of the movement, are incompatible with -the action of such a cause as this; and indeed it is highly interesting -to remark, in the midst of the signs of disturbance which prevail in -the bowels of the earth, that there reigns a certain symmetry and -order, which indicate the action of a force of incredible magnitude, -but slow and gradual in its effects. The parts of the mass moved are -undisturbed relatively to one another; what has been broken has been -cemented; the breaches of continuity have been filled up and healed; -and every where we see the operation of a cause that could unite as -well as separate. The twofold action of heat to expand and to melt, -could scarce be pointed out more clearly by any system of appearances.</p> - -<p>58. As a long period was no doubt required for the elevation of the -strata, the rents made -<span class="pagenum" id="Page_64">- 64 -</span> -in them are not all of the same date, nor the -veins all of the same formation. This is clear in the case of one vein -producing a shift or slip in another; for the vein which forces the -other out of its place, and preserves its own direction, is evidently -the more recent of the two, and must have had its materials in a -state of activity, when those of the other were inert. Sometimes, -also, at the intersection of two veins, we may trace the current of -the materials of the one, across those of the other; and here, of -consequence, the relative antiquity is determined just as in the former -instance.</p> - -<p><a id="sec_59"></a>59. The want of any appearance of stratification in mineral veins has -already been taken notice of. There is, however, to be observed, in -many instances, a tendency to a regular arrangement of the substances -contained in them; those of the same kind forming coats parallel to the -sides of the vein, and nearly of an equal thickness. This phenomenon -is considered as one of the strongest arguments in favour of the -Neptunian system, but has nothing in it, in the least incompatible -with that theory which ascribes the formation of veins to the action -of subterraneous heat. When melted matter from the mineral regions was -thrown up into the veins, that which was nearest to the sides would -soonest lose its heat. The similar substances, also, would unite while -<span class="pagenum" id="Page_65">- 65 -</span> -this process was going forward, and would crystallize, as in other -cases of congelation, from the sides toward the interior. There is the -more reason for supposing this to have been the case, that the same -sort of coating is often observed on the inside of close cavities, -which are, nevertheless, so constructed, as to afford a demonstration -that no chemical solvent was ever included in them, (<a href="#sec_74">§ 74.</a>) Some -veins, it must also be considered, may have been filled by successive -injections of melted matter, and this would naturally give rise to a -variety of separate incrustations.<a id="FNanchor_20" href="#Footnote_20" class="fnanchor">[20]</a></p> - -<div class="footnote"> - -<p><a id="Footnote_20" href="#FNanchor_20" class="label">[20]</a> See some farther remarks on this subject at <span class="smcap">Note -xiii</span>.</p> - -</div> - -<p>60. In the view now given of metallic veins, they have been considered -as traversing only the stratified parts of the globe. They do, -however, occasionally intersect the unstratified parts, particularly -the granite, the same vein often continuing its course across rocks -of both kinds, without suffering any material change; and, if we have -hitherto paid no attention to this circumstance, it is because the -order pursued in this essay required, that the relation of the veins -to stratified bodies should be first treated of. Besides, the facts -in the natural history of veins, whether contained in stratified or -unstratified -<span class="pagenum" id="Page_66">- 66 -</span> -rocks, are so nearly alike, that in a general view of -geology, they do not require to be distinguished. It is material to -remark, that, though metallic veins are found indiscriminately in all -the different kinds of rock, whether stratified or otherwise, they are -most abundant in the class of primary schisti. All the countries most -remarkable for their mines, and the mountains distinguished by the -name of metalliferous, are primary, and the instance of Derbyshire is -perhaps the most considerable exception to this rule that is known. -This preference, which the metals appear to give to the primary strata, -is very consistent with Dr Hutton's theory, which represents the rocks -of that order as being most changed from their original position, and -those on which the disturbing forces of the subterraneous regions have -acted most frequently, and with greatest energy. The primary strata are -the lowest, also, and have the most direct communication with those -regions from which the mineral veins derive all their riches.</p> - - -<p class="caption3nb" id="sect2p2">2. <i>Of Whinstone.</i></p> - -<p>61. Beside the veins filled with spar, and containing the metallic -ores, the strata are intersected by veins of whinstone, porphyry, and -granite, -<span class="pagenum" id="Page_67">- 67 -</span> -the characters of which are next to be examined.</p> - -<p>The term <i>whin</i>, or <i>whinstone</i>, with Dr. Hutton, like the -word <i>trap</i>, with the German mineralogists, denotes a class -of stones, comprehending several distinct species, or at least -varieties. The common <i>basalt</i>, the <i>wacken</i>, <i>mullen</i>, -and <i>crag</i> of Kirwan, the <i>grûnstein</i> of Werner, and the -<i>amygdaloid</i>, are comprehended under the name of whin. All these -stones have a tendency to a spathose structure, and discover at least -the rudiments of crystallization. They are, at the same time, without -any mark of stratification in their internal texture, as they are -also, for the most part, in their outward configuration; and, as the -different species here enumerated compose, not unfrequently, parts of -the same continuous rock, the change from one to another being made -through a series of insensible gradations, they may safely be regarded -by the geologist as belonging to the same <i>genus</i>.</p> - -<p><a id="sec_62"></a>62. Whin, though not stratified, exists in two different ways, that -is, either in veins, (called in Scotland <i>dykes</i>,) traversing -the strata like the veins already described, or in irregular masses, -incumbent on the strata, and sometimes interposed between them. In -both these forms, whinstone has nearly the same characters, and -<span class="pagenum" id="Page_68">- 68 -</span> -bears, in all its varieties, a most striking resemblance to the lavas -which have actually flowed from volcanoes on the surface of the earth. -This resemblance is so great, that the two substances have been often -mistaken for one another; and many rocks, which have been pronounced -to be the remains of extinguished volcanoes, by mineralogists of no -inconsiderable name, have been found, on closer examination, to be -nothing else than masses or veins of whinstone. This latter stone -is indeed only to be distinguished from the former, by a careful -examination of the internal characters of both; and chiefly from -this circumstance, that whinstone often contains calcareous spar and -zeolite, whereas neither of these substances is found in such lavas, as -are certainly known to have been thrown out by volcanic explosions.</p> - -<p>Now, from these circumstances of affinity between lava and whinstone, -on the one hand, and of diversity on the other, as the formation of -the one is known, it should seem that some probable conclusion may be -drawn concerning the formation of the other. The affinity in question -is constant and essential; the difference variable and accidental; -and this naturally leads to suspect, that the two stones have the -same origin; and that, as lava is certainly a production of fire, so -probably is whinstone.</p> - -<p><span class="pagenum" id="Page_69">- 69 -</span></p> - -<p>63. But, in order to see whether this hypothesis will explain the -diversity of the two substances, without which it will not be entitled -to much attention, we must remark, that the presence of carbonate of -lime in a body that has been fused, argues, agreeably to the principles -formerly explained, that the fusion was brought about under a great -compressing force, that is to say, deep in the bowels of the earth, or -in the great laboratory of the mineral regions. We are, therefore, to -suppose that the fusion of the whin was performed in those regions, -where the compression was sufficient to preserve the carbonic gas in -union with the calcareous earth, so that these two substances melted -together, and, on cooling, crystallized into spar. In the lavas, again, -thrown out by volcanic eruption, the fusion, as we know, wherever it -may begin, continues in the open air, where the pressure is only that -of the atmosphere: the calcareous earth, which, therefore, may have -been, in the form of a carbonate, among the materials of this lava, -must be converted into quicklime, and become infusible; hence the want -of calcareous spar in lavas that have flowed at the surface.</p> - -<p>Thus, whinstone is to be accounted a subterraneous, or <i>unerupted</i> -lava; and our theory has the advantage of explaining both the affinity -<span class="pagenum" id="Page_70">- 70 -</span> -and the difference between these stony bodies, without the introduction -of any new hypothesis. In the Neptunian system, the affinity of -whinstone and lava is a paradox which admits of no solution.</p> - -<p>64. The columnar structure sometimes found in that species of whinstone -called basaltes, is a fact which has given rise to much discussion; -and it must be confessed, that though one of the most striking and -peculiar characters of this fossil, it is not that which gives the -clearest and most direct information concerning its origin. One -circumstance, however, very much in favour of the opinion that basaltic -rocks owe their formation to fire, is, that the columnar form is -sometimes assumed by the lava actually erupted from volcanoes. Now, it -is certainly of no small importance, to have the synthetic argument -on our side, and to know, that basaltic columns can be produced by -fire; though, no doubt, to give absolute certainty to our conclusion, -it would be necessary to show, that there are in nature no other -means but this by which these columns can be formed. This sort of -evidence is hardly to be looked for; but since the power of fusion, -to produce the phenomena in question, is perfectly established, and -since the production of the same phenomena in the humid way is a -<span class="pagenum" id="Page_71">- 71 -</span> mere -hypothesis, if there be the least reason to suspect the action of -subterraneous heat as one of the causes of mineralization, every maxim -of sound philosophy requires that the basaltic structure, in all cases, -should be ascribed to it.</p> - -<p><a id="sec_65"></a>65. The Neptunists will no doubt allege, with <span class="smcap">Bergman</span>, that, -in the drying of starch, clay, and a few other substances, something -analogous to basaltic columns is produced. Here, however, a most -important difference is to be remarked, corresponding very exactly to -one of the characters which we have all along observed to distinguish -the products of aqueous, from those of igneous consolidation. The -columns formed by the substances just mentioned, are distant from -one another: they are separated by fissures which widen from the -bottom to the top, and which arise from the shrinking and drying of -the mass. In the basaltic columns, no such openings, nor vacuity of -any kind is found; the pillars are in contact, and, though perfectly -distinct, are so close, that the sharp edge of a wedge can hardly be -introduced between them. This is a great peculiarity in the basaltic -structure, and is strongly expressive of this fact, that the mass was -all fluid together, and that its parts took their new arrangement, -not in consequence of the separation of a fluid from a solid part, by -which great shrinking and much empty space -<span class="pagenum" id="Page_72">- 72 -</span> -might be produced; but in -consequence of a cause which, like refrigeration, acted equally on all -the parts of the mass, and preserved their absolute contact after their -fluidity had ceased.</p> - -<p><a id="sec_66"></a>66. A mark of fusion, or at least of the operation of heat, which -whinstone possesses in common with many other minerals, is its being -penetrated by pyrites, a substance, as has been already remarked, that -is of all others most exclusively the production of fire. Another -mark of fusion, more distinctive of whin, is, that both in veins and -in masses it sometimes includes pieces of sandstone, or of the other -contiguous strata, completely insulated, and having the appearance -of fragments of rock, floating in a fluid sufficiently dense and -ponderous to sustain their weight. Though these fragments have been -too refractory to be reduced into fusion themselves, they have not -remained entirely unchanged, but are, in general, extremely indurated, -in comparison of the rock from which they appear to have been detached.</p> - -<p><a id="sec_67"></a>67. Similar instances of extraordinary induration are observed in the -parts of the strata in contact with whinstone, whether they form the -sides of the veins, or the floors, and roofs of the masses into which -the whinstone is distributed. The strata whether sandy or argillaceous, -in such situations, are usually extremely hard and -<span class="pagenum" id="Page_73">- 73 -</span> -consolidated; the -former in particular lose their granulated texture, and are sometimes -converted into perfect jasper. This interesting remark was first made -by Dr Hutton, and the truth of it has been verified by a great number -of subsequent observations.</p> - -<p>68. To the same excellent geologist we are indebted for the knowledge -of an analogous fact, attendant on the passage of whinstone veins -through coal strata. As the beds of stone where they are in contact -with veins of whin, seem to acquire additional induration, so those -of coal, in like circumstances, are frequently found to have lost -their fusibility, and to be reduced nearly to the condition of coke, -or of charcoal. The existence of coal of this kind has been already -mentioned, and considered as a proof of the operation of subterraneous -heat. In the instances here referred to, that is, where the charring -of the coal is limited to those parts of the strata which are in -contact with the whin, or in its immediate vicinity, the heat is -pointed out as residing in the vein; and this is to be accounted for -only on the supposition of the melted whin, at a period subsequent to -the consolidation of the coal, having flowed through the openings of -the strata. The heat has been powerful enough, in many cases, to drive -off the bituminous matter of the coal, and to force it into colder and -more -<span class="pagenum" id="Page_74">- 74 -</span> -distant parts. Few facts, in the history of fossils, are more -remarkable than this, and none more directly assimilates the operations -of the mineral regions, with those that take place at the surface of -the earth.</p> - -<p>69. Again, the disturbance of the strata, wherever veins of whinstone -abound, if not a direct proof of the original fluidity of the -whinstone, is a clear indication of the violence with which it was -introduced into its place. This disturbance of the position of the -strata, by shifting, unusual elevation, and other irregularities, where -they are intersected by whinstone veins, is a fact so well known to -miners, that when they meet with any sudden change in the lying of the -<i>metals</i>, they are wont to foretell their approach to masses, -or veins of unstratified matter; and, in their figurative language, -point them out as the causes of the confusion with which they are so -generally accompanied.<a id="FNanchor_21" href="#Footnote_21" class="fnanchor">[21]</a> The mineral veins likewise, as well as the -strata, are often heaved and shifted by the veins of whinstone.</p> - -<div class="footnote"> - -<p><a id="Footnote_21" href="#FNanchor_21" class="label">[21]</a> A <i>Trouble</i> is the name which the colliers in this -country give to a vein of whinstone.</p> - -</div> - -<p>70. Whinstone of every species is found frequently interposed in -tabular masses, between beds of stratified rocks; and it then adds to -the -<span class="pagenum" id="Page_75">- 75 -</span> -indications of its igneous origin, already enumerated, some others -that are peculiar to it when in this situation. In such instances, it -is not uncommon to find the strata in some places, contiguous to the -whin, elevated, and bent with their concavity upward, so that they -appear clearly to have been acted on by a force that proceeded from -below, at the same time that they were softened, and rendered in some -degree flexible: it is needless to remark, that these effects can be -explained by nothing but the fusion of the whin; and that the great -force with which it was impelled against the strata, could be produced -by no cause but heat, acting in the manner that is here supposed.</p> - -<p>71. Again, if it be true that the masses of whin, thus interposed -among the strata, were introduced there, after the formation of the -latter, we might expect to find, at least in many instances, that the -beds on which the whinstone rests, and those by which it is covered, -are exactly alike. If these beds were once contiguous, and have been -only heaved up and separated by the irruption of a fluid mass of -subterraneous lava, their identity should still be recognised. Now, -this is precisely what is observed; it is known to hold in a vast -number of instances, and is strikingly exemplified in the rock of -<i>Salisbury Crag</i>, near Edinburgh.</p> - -<p><span class="pagenum" id="Page_76">- 76 -</span></p> - -<p>This similarity of the strata that cover the masses of whinstone, -to those that serve as the base on which they rest, and again the -dissimilitude of both to the interposed mass, are facts which I think -can hardly receive any explanation, on the principles of the Neptunian -theory. If these rocks, both stratified and unstratified, are to be -regarded as productions of the sea, the circumstances would require to -be pointed out, which have determined the whinstone, and the beds that -are all round it, to be so extremely unlike in their structure, though -formed at the same time, and in the immediate vicinity of one another; -as also those circumstances, on the other hand, which determined the -stratified deposits above and below the whinstone, to be precisely -the same, though the times of their formation must have been very -different. The homogeneous substances, thus, placed at a distance, and -the heterogeneous brought so closely together, are phenomena equally -unaccountable, in a theory that ascribes their origin to the operation -of the same element, and that necessarily dates their formation -according to the order in which they lie, one above another.</p> - -<p><a id="sec_72"></a>72. If, indeed, in these instances, the gradation were insensible, as -some have asserted it to be, between the strata and the interposed -mass, so that it was impossible to point out the line -<span class="pagenum" id="Page_77">- 77 -</span> -where the one -ended and the other began, whatever difficulties we might perceive in -the Neptunian theory, we should find it hard to substitute a better -in its room. But the truth seems to be, that, in the cases we are now -treating of, no such gradation exists; and that, though where the two -kinds of rock come into contact a change is often observed, by the -strata having acquired an additional degree of induration, yet the line -of separation is well defined, and can be precisely ascertained. This -at least is certain, that innumerable specimens, exhibiting such lines -of separation, are to be met with; and wherever care has been taken -to obtain a fresh fracture of the stone, and to remove the effects of -accidental causes, even where the two rocks are most firmly united, -and most closely assimilated, I am persuaded that no uncertainty has -ever remained as to the line of their separation. For these reasons, -it seems probable that the gradual transition of basaltes into the -adjoining strata, is in all cases imaginary, and is, in truth, a mere -illusion, proceeding from hasty and inaccurate observation.</p> - -<p>73. Another remarkable fact in the natural history of the whinstone -rocks, remains yet to be mentioned, and with it I shall conclude the -argument, as far as these rocks are concerned.</p> - -<p><span class="pagenum" id="Page_78">- 78 -</span></p> - -<p>Some of the species of whinstone are the common matrices of agates and -chalcedonies, which lie inclosed in them in the form of round nodules. -The original fluidity of these nodules is evinced by their figured, and -sometimes crystallized structure, and indeed is so generally admitted, -that the only question concerning them is, whether this fluidity -was the effect of heat or of solution. To answer this question, Dr -Hutton observes, that the formation of the concentric coats, of which -the agate is usually composed, has evidently proceeded from the -circumference toward the centre, the exterior coats always impressing -the interior, but never the reverse. The same thing also follows from -this other fact, that when there is any vacuity within the agate, it is -usually at the centre, and there too are found the regular crystals, -when any such have been formed. It therefore appears certain, that the -progress of consolidation has been from the circumference inwards, and -that the outward coats of the agate were the first to acquire solidity -and hardness.</p> - -<p><a id="sec_74"></a>74. Now, it must be considered that these coats are highly -consolidated; that they are of very pure siliceous matter, and are -utterly impervious to every substance which we know of, except light -and heat. It is plain, therefore, that whatever -<span class="pagenum" id="Page_79">- 79 -</span> at any time, during -the progress of consolidation, was contained within the coats already -formed, must have remained there as long as the agate was entire, -without the least possibility of escape. But nothing is found within -the coats of the agate save its own substance; therefore, no extraneous -substance, that is to say no solvent, was ever included within them. -The fluidity of the agate was therefore simple, and unassisted by any -menstruum.</p> - -<p>In this argument, nothing appears to me wanting, that is necessary to -the perfection of a physical, I had almost said of a mathematical, -demonstration. It seems, indeed, to be impossible that the igneous -origin of fossils could be recorded in plainer language, than by the -phenomenon which has just been described.</p> - -<p>75. The examination of particular specimens of agates and chalcedonies, -affords many more arguments of the same kind, which Dr Hutton used to -deduce with an acuteness and vivacity, which his friends have often -listened to with great admiration and delight.<a id="FNanchor_22" href="#Footnote_22" class="fnanchor">[22]</a> These, however, must -be passed over at present; and I have only further to remark, that a -series of the most interesting experiments, instituted by Sir <span class="smcap">James -Hall</span>, and published in the Transactions of the Royal Society of -Edinburgh,<a id="FNanchor_23" href="#Footnote_23" class="fnanchor">[23]</a> has removed the -<span class="pagenum" id="Page_80">- 80 -</span> -only remaining objection that could -be urged against the igneous origin of whinstone. This objection is -founded on the common observation, that when a piece of whinstone or -basaltes is actually melted in a crucible, on cooling, it becomes -glass, and loses its original character entirely; and from thence it -was concluded, that this character had not been originally produced by -fusion. The experiments above mentioned, however, have shown, in the -most satisfactory manner, that melted whin, by <i>regulated</i> or by -slow cooling, is prevented from assuming the appearance of glass, and -becomes a stony substance, hardly to be distinguished from whinstone or -lava.</p> - -<div class="footnote"> - -<p><a id="Footnote_22" href="#FNanchor_22" class="label">[22]</a> <span class="smcap"><a href="#Note_xvi">Note xvi.</a></span></p> - -<p><a id="Footnote_23" href="#FNanchor_23" class="label">[23]</a> vol. v. p. 43.</p> - -</div> - -<p>The experiments of another ingenious chemist, Dr <span class="smcap">Kennedy</span>, have -shown, that whinstone contains mineral alkali, by which, of course, -its fusion must have been assisted.<a id="FNanchor_24" href="#Footnote_24" class="fnanchor">[24]</a> Dr Hutton used to ascribe -its fusibility, in a great measure at least, to the quantity of iron -contained in it: both these causes have no doubt united to render it -more easily melted than the ordinary materials of the strata.</p> - -<div class="footnote"> - -<p><a id="Footnote_24" href="#FNanchor_24" class="label">[24]</a> Trans. R. S. Edin. vol. v. p. 85.</p> - -</div> - -<p>76. In a word, therefore, to conceive aright the origin of that class -of unstratified rocks, distinguished by the name of whinstone, we must -suppose, -<span class="pagenum" id="Page_81">- 81 -</span> that long after the consolidation of the strata, and during -the time of their elevation, the materials of the former were melted -by the force of subterraneous heat, and injected among the rents and -fissures of the rocks already formed. In this manner were produced -the veins or dikes of whinstone; and, where circumstances allowed -the stream of melted matter to diffuse itself more widely, tabular -masses were formed, which were afterwards raised up, together with the -surrounding strata, above the level of the sea, and have been since -laid open by the operation of those causes that continually change and -waste the surface of the land.</p> - -<p>These unstratified rocks are not, however, all the work of the same -period; they differ evidently in the date of their formation, and it is -not unusual, to find tabular masses of one species of whin, intersected -by veins of another species. Indeed, of all the fossil bodies which -compose the present land, the veins of whin appear to be the most -recently consolidated.<a id="FNanchor_25" href="#Footnote_25" class="fnanchor">[25]</a></p> - -<div class="footnote"> - -<p><a id="Footnote_25" href="#FNanchor_25" class="label">[25]</a> <span class="smcap"><a href="#Note_xiv">Note xiv.</a></span></p> - -</div> - -<p>Porphyry may so properly be regarded as a variety of whin, -distinguished only by involving crystallized feldspar, that, in a -geological sketch like the present, it is hardly entitled to a separate -article. Like the other kinds of -<span class="pagenum" id="Page_82">- 82 -</span> whin, it exists both in veins and -in tabular masses, having, no doubt, an origin similar to that which -has just been described. Porphyry, however, has the peculiarity of -being rarely found in any but the primary strata; it seems to be the -whinstone of the old world, or at least that which is of the highest -antiquity in the present. It no where, I believe, assumes a columnar, -or basaltic appearance, of any regularity; but this is also true of -many other varieties of whin, of all, indeed, except the most compact -and homogeneous. These differences are not so considerable as to -require our entering into any particular detail concerning the natural -history of this fossil.</p> - - -<p class="caption3nb" id="sect2p3">3. <i>Granite</i>.</p> - -<p><a id="sec_77"></a>77. The term Granite is used by Dr Hutton to signify an aggregate -stone, in which quartz, feldspar, and mica are found distinct from -one another, and not disposed in layers. The addition of hornblende, -schorl, or garnet, to the three ingredients just mentioned, is not -understood to alter the <i>genus</i> of the stone, but only to -constitute a specific difference, which it is the business of lithology -to mark by some appropriate character, annexed to the generic name of -granite.</p> - -<p><span class="pagenum" id="Page_83">- 83 -</span></p> - -<p>The fossil now defined exists, like whinstone and porphyry, both in -masses and in veins, though most frequently in the former. It is like -them unstratified in its texture, and is regarded here, as being also -unstratified in its outward structure.<a id="FNanchor_26" href="#Footnote_26" class="fnanchor">[26]</a> One ingredient which is -essential to granite, namely, quartz, is not contained in whinstone; -and this circumstance serves to distinguish these <i>genera</i> from -one another, though, in other respects, they seem to be united by a -chain of insensible gradations, from the -<span class="pagenum" id="Page_84">- 84 -</span> most homogeneous basaltes, to -granite the most highly crystallized.</p> - -<div class="footnote"> - -<p><a id="Footnote_26" href="#FNanchor_26" class="label">[26]</a> Those rocks that consist of the ingredients here -enumerated, if they have at the same time a schistose texture, or a -disposition into layers, are properly distinguished from granite, and -called Gneiss, or Granitic Schistus. But it has been questioned whether -a stone does not exist composed of these ingredients, and destitute -of a schistose texture, but yet divided into large beds, visible in -its external form. Dr Hutton supposes such a stone not to exist, or at -least not to constitute any such proportion of the mineral kingdom, as -to entitle it to particular consideration, in the general speculations -of geology.</p> - -<p>Whether this supposition is perfectly correct, may require to be -farther considered: this, however, is certain, that a rock, in all -respects conformable to it, composes a great proportion of what are -usually called the granite mountains. See <span class="smcap">Note xv</span>.</p> - -</div> - -<p>78. Granite, it has been just said, exists most commonly in masses; and -these masses are rarely, if ever, incumbent on any other rock: they are -the basis on which others rest, and seem, for the most part, to rise -up from under the ancient, or primary strata. The granite, therefore, -wherever it is found, is inferior to every other rock; and as it also -composes many of the greatest mountains, it has the peculiarity of -being elevated the highest into the atmosphere, and sunk the deepest -under the surface, of all the mineral substances with which we are -acquainted.</p> - -<p>Notwithstanding the circumstance of not being alternated with -stratified bodies, which constitutes a remarkable difference between -granite and whinstone, the affinity of these fossils is such as to make -the similarity of their origin by no means improbable. Accordingly, -in Dr Hutton's theory, granite is regarded as a stone of more recent -formation than the strata incumbent on it; as a substance which has -been melted by heat, and which, when forced up from the mineral -regions, has elevated the strata at the same time.</p> - -<p>79. That granite has undergone a change from a fluid to a solid -state, is evinced from the crystallized structure in which some of -its component -<span class="pagenum" id="Page_85">- 85 -</span> parts are usually found. This crystallization is -particularly to be remarked of the feldspar, and also of the schorl, -where there is any admixture of that substance, whether in slender -spiculæ, or in larger masses. The quartz itself is in some cases -crystallized, and is so, perhaps, more frequently than is generally -supposed. The fluidity of granite, in some former period of its -existence, is so evident from this, as to make it appear singular that -it should ever have been considered as a fossil that had remained -always the same, and one, into the origin of which it was needless to -inquire. If the regular forms of crystallization are not to be received -as proofs of the substance to which they belong having passed from -a fluid to a solid state, neither are the figures of shells and of -other supposed petrifactions, to be taken as indications of a passage -from the animal to the mineral kingdom; so that there is an end of -all geological theories, and of all reasonings concerning the ancient -condition of the globe. To an argument which strikes equally at the -root of all theories, it belongs not to this, in particular, to make -any reply.</p> - -<p>80. We shall, therefore, consider it as admitted, that the materials -of the granite were originally fluid; and, in addition to this, we -think it can easily be proved, that this fluidity was -<span class="pagenum" id="Page_86">- 86 -</span> not that of the -elements taken separately, but of the entire mass. This last conclusion -follows, from the structure of those specimens, where one of the -substances is impressed by the forms which are peculiar to another. -Thus, in the Portsoy granite,<a id="FNanchor_27" href="#Footnote_27" class="fnanchor">[27]</a> which Dr Hutton has so minutely -described, the quartz is impressed by the rhomboidal crystals of the -feldspar, and the stone thus formed is compact and highly consolidated. -Hence, this granite is not a congeries of parts, which, after being -separately formed, were somehow brought together and agglutinated; but -it is certain that the quartz, at least, was fluid when it was moulded -on the feldspar. In other granites, the impressions of the substances -on one another are observed in a different order, and the quartz gives -its form to the feldspar. This, however, is more unusual; the quartz -is commonly the substance which has received the impressions of all -the rest; and the spiculæ of schorl often shoot both across it and the -feldspar.</p> - -<div class="footnote"> - -<p><a id="Footnote_27" href="#FNanchor_27" class="label">[27]</a> Theory of the Earth, vol. i. p. 104.</p> - -</div> - -<p>The ingredients of granite were therefore fluid when mixed, or at least -when in contact with one another. Now, this fluidity was not the effect -of solution in a menstruum; for, in that case, one kind of crystal -ought not to impress another, but each of them should have its own -peculiar shape.</p> - -<p><span class="pagenum" id="Page_87">- 87 -</span></p> - -<p>81. The perfect consolidation of many granites, furnishes an argument -to the same effect. For, agreeably to what was already observed, in -treating of the strata, a substance, when crystallizing, or passing -from a fluid to a solid state, cannot be free from porosity, much -less fill up completely a space of a given form, if, at the same -time, any solvent is separated from it; because the solvent so -separated would still occupy a certain space, and, when removed by -evaporation or otherwise, would leave that space empty. The perfect -adjustment, therefore, of the shape of one set of crystallizing bodies, -to the shape of another set, as in the Portsoy granite, and their -consolidation into one mass, is as strong a proof as could be desired, -that they crystallized from a state of simple fluidity, such as, of all -known causes, heat alone is able to produce.</p> - -<p><a id="sec_82"></a>82. This conclusion, however, does not rest on a single class of -facts. It has been observed in many instances, that where granite and -stratified rocks, such as primary schistus, are in contact, the latter -are penetrated by veins of the former, which traverse them in various -directions. These veins are of different dimensions, some being of the -breadth of several yards, others of a few inches, or even tenths of an -inch; they diminish as they recede from the main body -<span class="pagenum" id="Page_88">- 88 -</span> of the granite, -to which they are always firmly united, constituting, indeed, a part of -the same continued rock.</p> - -<p>These phenomena, which were first distinctly observed by Dr Hutton, are -of great importance in geology, and afford a clear solution of the two -chief questions concerning the relation between granite and schistus. -As every vein must be of a date posterior to the body in which it is -contained, it follows, that the schistus was not super-imposed on -the granite, after the formation of this last. If it be argued, that -these veins, though posterior to the schisti, are also posterior to -the granite, and were formed by the infiltration of water in which the -granite was dissolved or suspended; it may be replied, <i>1mo</i>, -That the power of water to dissolve granite, is a postulatum of the -same kind that we have so often, and for such good reason, refused to -concede; and, <i>2do</i>, That in many instances the veins proceed -from the main body of the granite <i>upwards</i> into the schistus; -so that they are in planes much elevated in respect of the horizon, -and have a direction quite opposite to that which the hypothesis of -infiltration requires. It remains certain, therefore, that the whole -mass of granite, and the veins proceeding from it, are coeval, and both -of later formation than the strata.</p> - -<p><span class="pagenum" id="Page_89">- 89 -</span></p> - -<p>Now, this being established, and the fluidity of the veins, when they -penetrated into the schistus, being obvious, it necessarily follows, -that the whole granite mass was also fluid at the same time. But this -can have been brought about only by subterraneous heat, which also -impelled the melted matter against the superincumbent strata, with such -force as to raise them from their place, and to give them that highly -inclined position in which they are still supported by the granite, -after its fluidity has ceased. Thus a conclusion, rendered probable by -the crystallization of granite, is established beyond all contradiction -by the phenomena of granitic veins.<a id="FNanchor_28" href="#Footnote_28" class="fnanchor">[28]</a></p> - -<div class="footnote"> - -<p><a id="Footnote_28" href="#FNanchor_28" class="label">[28]</a> <span class="smcap"><a href="#Note_xv">Note xv.</a></span></p> - -</div> - -<p>83. With the granite, we shall consider the proof of the igneous origin -of all mineral substances as completed. These substances, therefore, -whether stratified or unstratified, owe their consolidation to the same -cause, though acting with different degrees of energy. The stratified -have been in general only softened or penetrated by melted matter, -whereas the unstratified have been reduced into perfect fusion.</p> - -<p>84. In this general conclusion we may distinguish two parts, which, in -their degree of certainty, differ perhaps somewhat from one another. -The first of these, and that which stands highest in point of evidence, -consists of two -<span class="pagenum" id="Page_90">- 90 -</span> propositions; namely, that the fluidity which preceded -the consolidation of mineral substances was <span class="smcap">simple</span>, that is, -it did not arise from the combination of these substances with any -solvent; and, next, that after consolidation, these bodies have been -raised up by an expansive force acting from below, and have by that -means been brought into their present situation. These two propositions -seem to me to be supported by all the evidence that is necessary to -constitute the most perfect demonstration.</p> - -<p>85. The other part of the general conclusion, that fire, or more -properly heat, was the cause of the fluidity of these mineral bodies, -and also of their subsequent elevation, is not perhaps to be considered -as a truth so fully demonstrated as the two preceding propositions; it -is, no doubt, a matter of <span class="smcap">theory</span>; or a portion of one of those -invisible chains by which men seek to connect in the mind the state -of nature that is present, with the states of it that are past; and -participates of that uncertainty from which our reasonings concerning -such causes as are not direct objects of perception, are hardly ever -exempted. That it participates of this uncertainty in a very slight -degree, will, however, be admitted, when it is considered that the -cause assigned has been proved sufficient for the effect; that the same -is not true of any other known cause; and -<span class="pagenum" id="Page_91">- 91 -</span> that this theory accounts, -with singular simplicity and precision, for a system of facts so -various and complex, as that which is presented by the natural history -of the globe.</p> - -<p>86. Neither can it be said that the existence of subterraneous heat is -a principle assumed without any evidence, but that of the geological -facts which it is intended to explain: on the contrary, it is proved by -phenomena within the circle of ordinary experience, namely, those of -hot springs, volcanoes, and earthquakes. These leave no doubt of the -existence of heat, and of a moving and expansive power, in the bowels -of the earth; so that the only questions are, at what depth is this -power lodged? to what extent, and with what intensity, does it act? -That it is lodged at a very considerable depth, is rendered probable by -the permanency of some of the preceding phenomena: from the earliest -times many fountains have retained their heat to the present day; and -volcanoes, though they become extinguished at length, have a very -long period allotted for their duration. The cause of earthquakes is -certainly a force that resides very deep under the surface, otherwise -the extent of the concussion could not be such as has been observed in -many instances.</p> - -<p>87. The intensity of volcanic fire, is another circumstance that -favours the opinion of its being -<span class="pagenum" id="Page_92">- 92 -</span> seated deep under the surface. That -this intensity is considerable, is certain from the experiments made -by Sir James Hall on the fusibility of whinstone and lava; from which -it appears, that the lowest temperature in which either of these -stones melt, is about 80° of Wedgewood's pyrometer. Some mineralogists -have indeed affirmed, that lava is melted, not by the intensity of -the heat applied to it, but in consequence of a certain combination -formed between it and bituminous substances, in a manner which they do -not attempt to explain, and which has indeed no analogy to any thing -that is known. That a hypothesis, formed in such direct opposition to -the most obvious principles of inductive reasoning, should have been -imagined by a philosopher who had examined the phenomena of Etna and -Vesuvius with much attention, and described them with great accuracy -and truth, is more wonderful than that it should have been adopted by -mineralogists, whose views of nature may have been confined within a -cabinet or a laboratory. It is, however, a hypothesis, which, having -never had any support but from other hypotheses, hardly merited the -direct refutation that it has received from the experiments just -mentioned.</p> - -<p>88. But, if the intensity of volcanic heat be such as is here -stated, it will be found very -<span class="pagenum" id="Page_93">- 93 -</span> difficult to account for a fire of -such activity, and of such long continuance in the same spot, by any -decomposition of mineral substances near the surface. In the place -where this combustion is supposed to exist, it must be remembered, -that there is no fresh supply of materials to replace those that have -been consumed, and that, therefore, the original accumulation of these -materials in one spot, must have been very unlike any thing that has -ever been observed concerning the disposition of minerals in the bowels -of the earth.</p> - -<p>89. If, on the other hand, we ascribe the phenomena of volcanoes to -the central heat, the account that may be given of them is simple, and -consistent with itself. According to all the appearances from which the -existence of such heat has been inferred above, it is of a nature so -far different from ordinary fire, that it may require no circulation -of air, and no supply of combustible materials to support it. It is -not accompanied with inflammation or combustion, the great pressure -preventing any separation of parts in the substances on which it acts, -and the absence of that elastic fluid without which heat seems to have -no power to decompose bodies, even the most combustible, contributing -to the unalterable nature of all the substances in the mineral regions. -There, of consequence, the -<span class="pagenum" id="Page_94">- 94 -</span> only effects of heat are fusion and -expansion; and that which forms the nucleus of the globe may therefore -be a fluid mass, melted, but unchanged by the action of heat.</p> - -<p>90. If, from the confines of this nucleus, we conceive certain fissures -and openings to traverse the solid crust, and to issue at the surface -of the earth, the vapours ascending through these may in time heat the -sides of the tubes through which they pass to a vast distance from the -lower extremities. It is, indeed, difficult to fix the limit to which -this distance may extend, on account of the great difference between -the rate at which heat moves when it has a fluid for its vehicle, and -when it is left to make its way alone through a solid body. In the -present case, the supply of heat is rapid, as being made by a vapour -ascending through a tube of solid rock; and the dissipation of it slow, -as arising from its transmission through the rock. The waste of heat is -therefore small, compared with the supply, and grows smaller at every -given point, the longer the stream of heated vapour has continued to -flow. Such a stream, therefore, though it may at first be condensed -within a small distance of its source, will in time reach higher -and higher, and may at last be able to carry its heat to an immense -distance from the place of its original derivation. Thus, it is easy -to -<span class="pagenum" id="Page_95">- 95 -</span> conceive, that vapours from the mineral regions may convey their -heat to reservoirs of water near the surface of the earth, and may in -that manner produce hot springs, and even boiling fountains, like those -of Rycum and Geyser.</p> - -<p>91. When, instead of a heated vapour, melted matter is thrown up -through the <i>shafts</i> or <i>tubes</i>, which thus communicate with -the mineral regions, veins of whinstone and basaltes are formed in the -interior of the earth. When the melted matter reaches to the surface, -it is thrown out in the form of lava, and all the other phenomena of -volcanoes are produced.</p> - -<p>Lastly, where melted matter of this kind, or vapours without being -condensed, have their progress obstructed, those dreadful concussions -are produced, which seem to threaten the existence even of the earth -itself. Though terrible, therefore, to the present inhabitants of the -globe, the earthquake has its place in the great system of geological -operations, and is part of a series of events, essential, as will more -clearly appear hereafter, to the general order, and to the preservation -of the whole.</p> - -<p>Such, according to this theory, are the changes which have befallen -mineral substances in the bowels of the earth; and though different -for the stratified and unstratified parts of those -<span class="pagenum" id="Page_96">- 96 -</span> substances, they -are connected together by the same <i>principle</i>, or explained by -the same <i>cause</i>. It remains to consider that part of the history -of both which describes their changes after their elevation to the -surface; and here we shall find new causes introduced, which are more -directly the subjects of observation, than those hitherto treated of; -causes, also, which act on all fossils alike, and alike prepare them -for their ultimate destination.</p> - - -<hr class="chap x-ebookmaker-drop" /> - -<div class="chapter"> -<p><span class="pagenum" id="Page_97">- 97 -</span></p> - -<h2 class="nobreak" id="SECTION_III">SECTION III.</h2> -</div> - -<p class="caption3nb">OF THE PHENOMENA COMMON TO<br /> -STRATIFIED AND UNSTRATIFIED BODIES.</p> - - -<div class="fl_left"> -<span class="num_left">92.</span> <span class="vbig">T</span> -</div> - -<p><a id="sec_92"></a><span class="hidden">92. T</span>HE series of changes which fossil bodies are destined to -undergo, does not cease with their elevation above the level of the -sea; it assumes, however, a new direction, and from the moment that -they are raised up to the surface, is constantly exerted in reducing -them again under the dominion of the ocean. The solidity is now -destroyed which was acquired in the bowels of the earth; and as the -bottom of the sea is the great laboratory, where loose materials are -mineralized and formed into stone, the atmosphere is the region where -stones are decomposed, and again resolved into earth.</p> - -<p>This decomposition of all mineral substances, exposed to the air, -is continual, and is brought about by a multitude of agents, both -chemical and mechanical, of which some are known to us, and many, no -doubt, remain to be discovered. Among the various aëriform fluids which -compose our atmosphere, one is already distinguished as the grand -principle of mineral decomposition; the others are not inactive, and -to them we must -<span class="pagenum" id="Page_98">- 98 -</span> add moisture, heat, and perhaps light; substances -which, from their affinities to the elements of mineral bodies, have a -power of entering into combination with them, and of thus diminishing -the forces by which they are united to one another. By the action of -air and moisture, the metallic particles, particularly the iron, which -enters in great abundance into the composition of almost all fossils, -becomes oxydated in such a degree as to lose its tenacity; so that the -texture of the surface is destroyed, and a part of the body resolved -into earth.</p> - -<p>93. Some earths, again, such as the calcareous, are immediately -dissolved by water; and though the quantity so dissolved be extremely -small, the operation, by being continually renewed, produces a slow -but perpetual corrosion, by which the greatest rocks must in time be -subdued. The action of water in destroying hard bodies into which it -has obtained entrance, is much assisted by the vicissitudes of heat -and cold, especially when the latter extends as far as the point of -congelation; for the water, when frozen, occupies a greater space than -before, and if the body is compact enough to refuse room for this -expansion, its parts are torn asunder by a repulsive force acting in -every direction.</p> - -<p>94. Besides these causes of mineral decomposition, the action of which -we can in some measure trace, there are others known to us only by -their effects.</p> - -<p><span class="pagenum" id="Page_99">- 99 -</span></p> - -<p>We see, for instance, the purest rock crystal affected by exposure -to the weather, its lustre tarnished, and the polish of its surface -impaired, but we know nothing of the power by which these operations -are performed. Thus also, in the precautions which the mineralogist -takes to preserve the fresh fracture of his specimens, we have a proof -how indiscriminately all the productions of the fossil kingdom are -exposed to the attacks of their unknown enemies, and we perceive how -difficult it is to delay the beginnings of a process which no power -whatever can finally counteract.</p> - -<p>95. The mechanical forces employed in the disintegration of mineral -substances, are more easily marked than the chemical. Here again water -appears as the most active enemy of hard and solid bodies; and, in -every state, from transparent vapour to solid ice, from the smallest -rill to the greatest river, it attacks whatever has emerged above the -level of the sea, and labours incessantly to restore it to the deep. -The parts loosened and disengaged by the chemical agents, are carried -down by the rains, and, in their descent, rub and grind the superficies -of other bodies. Thus water, though incapable of acting on hard -substances by direct attrition, is the -<span class="pagenum" id="Page_100">- 100 -</span> cause of their being so acted -on; and, when it descends in torrents, carrying with it sand, gravel, -and fragments of rock, it may be truly said to turn the forces of the -mineral kingdom against itself. Every separation which it makes is -necessarily permanent, and the parts once detached can never be united, -save at the bottom of the ocean.</p> - -<p>96. But it would far exceed the limits of this sketch, to pursue -the causes of mineral decomposition through all their forms. It is -sufficient to remark, that the consequence of so many minute, but -indefatigable agents, all working together, and having <i>gravity</i> -in their favour, is a system of universal decay and degradation, which -may be traced over the whole surface of the land, from the mountain -top to the sea shore. That we may perceive the full evidence of this -truth, one of the most important in the natural history of the globe, -we will begin our survey from the latter of these stations, and retire -gradually toward the former.</p> - -<p>97. If the coast is bold and rocky, it speaks a language easy to -be interpreted. Its broken and abrupt contour, the deep gulfs and -salient promontories by which it is indented, and the proportion which -these irregularities bear to the force of the waves, combined with -the inequality of hardness in the rocks, prove, that the present -<span class="pagenum" id="Page_101">- 101 -</span> -line of the shore has been determined by the action of the sea. The -naked and precipitous cliffs which overhang the deep, the rocks -hollowed, perforated, as they are farther advanced in the sea, and at -last insulated, lead to the same conclusion, and mark very clearly -so many different stages of decay. It is true, we do not see the -successive steps of this progress exemplified in the states of the same -individual rock, but we see them clearly in different individuals; -and the conviction thus produced, when the phenomena are sufficiently -multiplied and varied, is as irresistible, as if we saw the changes -actually effected in the moment of observation.</p> - -<p>On such shores, the fragments of rock once detached, become instruments -of further destruction, and make a part of the powerful artillery with -which the ocean assails the bulwarks of the land: they are impelled -against the rocks, from which they break off other fragments, and the -whole are thus ground against one another; whatever be their hardness, -they are reduced to gravel, the smooth surface and round figure of -which, are the most certain proofs of a <i>detritus</i> which nothing -can resist.</p> - -<p>98. Again, where the sea coast is flat, we have abundant evidence of -the degradation of the land in the beaches of sand and small gravel; -the sand banks and shoals that are continually -<span class="pagenum" id="Page_102">- 102 -</span> changing; the alluvial -land at the mouths of the rivers; the bars that seem to oppose their -discharge into the sea, and the shallowness of the sea itself. On -such coasts, the land usually seems to gain upon the sea, whereas, -on shores of a bolder aspect, it is the sea that generally appears -to gain upon the land. What the land acquires in extent, however, it -loses in elevation; and, whether its surface increase or diminish, the -depredations made on it are in both cases evinced with equal certainty.</p> - -<p><a id="sec_99"></a>99. If we proceed in our survey from the shores, inland, we meet -at every step with the fullest evidence of the same truths, and -particularly in the nature and economy of rivers. Every river appears -to consist of a main trunk, fed from a variety of branches, each -running in a valley proportioned to its size, and all of them together -forming a system of vallies, communicating with one another, and having -such a nice adjustment of their declivities, that none of them join the -principal valley, either on too high or too low a level; a circumstance -which would be infinitely improbable, if each of these vallies were not -the work of the stream that flows in it.</p> - -<p>If indeed a river consisted of a single stream, without branches, -running in a straight valley, it might be supposed that some great -concussion, -<span class="pagenum" id="Page_103">- 103 -</span> or some powerful torrent, had opened at once the channel -by which its waters are conducted to the ocean; but, when the usual -form of a river is considered, the trunk divided into many branches, -which rise at a great distance from one another, and these again -subdivided into an infinity of smaller ramifications, it becomes -strongly impressed upon the mind, that all these channels have been cut -by the waters themselves; that they have been slowly dug out by the -washing and erosion of the land; and that it is by the repeated touches -of the same instrument, that this curious assemblage of lines has been -engraved so deeply on the surface of the globe.</p> - -<p><a id="sec_100"></a>100. The changes which have taken place in the courses of rivers, are -also to be traced, in many instances, by successive platforms, of flat -alluvial land, rising one above another, and marking the different -levels on which the river has run at different periods of time. Of -these, the number to be distinguished, in some instances, is not less -than four, or even five; and this necessarily carries us back, like -all the operations we are now treating of, to an antiquity extremely -remote: for, if it be considered, that each change which the river -makes in its bed, obliterates at least a part of the monuments of -former changes, we shall be convinced, that -<span class="pagenum" id="Page_104">- 104 -</span> only a small part of the -progression can leave any distinct memorial behind it, and that there -is no reason to think, that, in the part which we see, the beginning is -included.<a id="FNanchor_29" href="#Footnote_29" class="fnanchor">[29]</a></p> - -<div class="footnote"> - -<p><a id="Footnote_29" href="#FNanchor_29" class="label">[29]</a> <span class="smcap"><a href="#Note_xvi">Note xvi.</a></span></p> - -</div> - -<p>101. In the same manner, when a river undermines its banks, it often -discovers deposits of sand and gravel, that have been made when it ran -on a higher level than it does at present. In other instances, the same -strata are seen on both the banks, though the bed of the river is now -sunk deep between them, and perhaps holds as winding a course through -the solid rock, as if it flowed along the surface; a proof that it must -have begun to sink its bed, when it ran through such loose materials as -opposed but a very inconsiderable resistance to its stream. A river, of -which the course is both serpentine and deeply excavated in the rock, -is among the phenomena, by which the slow waste of the land, and also -the cause of that waste, are most directly pointed out.</p> - -<p>102. It is, however, where rivers issue through narrow defiles among -mountains, that the identity of the strata on both sides is most easily -recognised, and remarked at the same time with the greatest wonder. On -observing the Potowmack, where it penetrates the ridge of the Allegany -mountains, or the Irtish, as it issues from the defiles of Altai, -there is no man, however -<span class="pagenum" id="Page_105">- 105 -</span> little addicted to geological speculations, -who does not immediately acknowledge, that the mountain was once -continued quite across the space in which the river now flows; and, if -he ventures to reason concerning the cause of so wonderful a change, -he ascribes it to some great convulsion of nature, which has torn the -mountain asunder, and opened a passage for the waters. It is only the -philosopher, who has deeply meditated on the effects which action long -continued is able to produce, and on the simplicity of the means which -nature employs in all her operations, who sees in this nothing but the -gradual working of a stream, that once flowed over the top of the ridge -which it now so deeply intersects, and has cut its course through the -rock, in the same way, and almost with the same instrument, by which -the lapidary divides a block of marble or granite.</p> - -<p>103. It is highly interesting to trace up, in this manner, the action -of causes with which we are familiar, to the production of effects, -which at first seem to require the introduction of unknown and -extraordinary powers; and it is no less interesting to observe, how -skilfully nature has balanced the action of all the minute causes of -waste, and rendered them conducive to the general good. Of this we -have a most remarkable instance, in the provision made for preserving -the soil, or the coat of vegetable -<span class="pagenum" id="Page_106">- 106 -</span> mould, spread out over the surface -of the earth. This coat, as it consists of loose materials, is easily -washed away by the rains, and is continually carried down by the rivers -into the sea. This effect is visible to every one; the earth is removed -not only in the form of sand and gravel, but its finer particles -suspended in the waters, tinge those of some rivers continually, and -those of all occasionally, that is, when they are flooded or swollen -with rains. The quantity of earth thus carried down, varies according -to circumstances; it has been computed, in some instances, that the -water of a river in a flood, contains earthy matter suspended in it, -amounting to more than the two hundred and fiftieth part of its own -bulk.<a id="FNanchor_30" href="#Footnote_30" class="fnanchor">[30]</a> The soil, therefore, is continually diminished, its parts -being transported from higher to lower levels, and finally delivered -into the sea. But it is a fact, that the soil, notwithstanding, remains -the same in quantity, or at least nearly the same, and must have done -so, ever since the earth was the receptacle of animal or vegetable -life. The soil, therefore, is augmented from other causes, just as -much, at an average, as it is diminished by that now mentioned; and -this augmentation evidently can proceed from nothing -<span class="pagenum" id="Page_107">- 107 -</span> but the constant -and slow disintegration of the rocks. In the permanence, therefore, -of a coat of vegetable mould on the surface of the earth, we have a -demonstrative proof of the continual destruction of the rocks; and -cannot but admire the skill, with which the powers of the many chemical -and mechanical agents employed in this complicated work, are so -adjusted, as to make the supply and the waste of the soil exactly equal -to one another.</p> - -<div class="footnote"> - -<p><a id="Footnote_30" href="#FNanchor_30" class="label">[30]</a> See Lehman, Traités de Phys. &c. tom. iii. p. 359. Note.</p> - -</div> - -<p>104. Before we take leave of the rivers and the plains, we must remark -another fact, often observed in the natural history of the latter, and -clearly evincing the former existence of immense bodies of strata, in -situations from which they have now entirely disappeared. The fact here -alluded to is, the great quantity of round and hard gravel, often to be -met with in the soil, under such circumstances, as prove, that it can -only have come from the decomposition of rocks, that once occupied the -very ground over which this gravel is now spread. In the chalk country, -for instance, about London, the quantity of flints in the soil is every -where great; and, in particular situations, nothing but flinty gravel -is found to a considerable depth. Now, the source from which these -flints are derived is quite evident, for they are precisely the same -with those contained in the chalk beds, wherever -<span class="pagenum" id="Page_108">- 108 -</span> these last are found -undisturbed, and from the destruction of such beds they have no doubt -originated. Hence a great thickness of chalk must have been decomposed, -to yield the quantity of flints now in the soil of these countries; for -the flints are but thinly scattered through the native chalk, compared -with their abundance in the loose earth. To afford, for example, such -a body of flinty gravel as is found about Kensington, what an enormous -quantity of chalk rock must have been destroyed?</p> - -<p><a id="sec_105"></a>105. This argument, which Dr Hutton has applied particularly to the -chalk countries, may be extended to many others. The great plain of -Crau, near the mouth of the Rhone, is well known, and was regarded -with wonder, even in ages when the natural history of the globe was -not an object of much attention. The immense quantity of large round -gravel-stones, with which this extensive plain is entirely covered, -has been supposed, by some mineralogists, to have been brought down -by the Durance, and other torrents, from the Alps; but, on further -examination, has been found to be of the same kind that is contained -in certain horizontal layers of pudding-stone, which are the basis of -the whole plain. It cannot be doubted, therefore, that the vast body of -gravel spread over it, has originated from the destruction of layers -<span class="pagenum" id="Page_109">- 109 -</span> -of the same rock, which may perhaps have risen to a great height above -what is now the surface. Indeed, from knowing the depth of the gravel -that covers the plain, and the average quantity of the like gravel -contained in a given thickness of rock, one might estimate how much of -the latter has been actually worn away. Whether data precise enough -could be found, to give any weight to such a computation, must be left -fer future inquiry to determine.<a id="FNanchor_31" href="#Footnote_31" class="fnanchor">[31]</a></p> - -<div class="footnote"> - -<p><a id="Footnote_31" href="#FNanchor_31" class="label">[31]</a> <span class="smcap"><a href="#Note_xvii">Note xvii.</a></span></p> - -</div> - -<p>106. In these instances, chalk and pudding-stone, by containing in -them parts infinitely less destructible than their general mass, have, -after they are worn away, left behind them very unequivocal marks of -their existence. The same has happened in the case of mineral veins, -where the substances least subject to dissolution have remained, -and are scattered at a great distance from their native place. Thus -gold, the least liable to decomposition of all the metals, is very -generally diffused through the earth, and is found, in a greater or -less abundance, in the sand of almost all rivers. But the native place -of this mineral is the solid rock, or the veins and cavities contained -in the rock, and from thence it must have made its way into the soil. -This, therefore, is another proof of the vast extent to which the -degradation of the land, and of -<span class="pagenum" id="Page_110">- 110 -</span> the rock, which is the basis of it, -has been earned; and consequently, of the great difference between -the elevation and shape of the earth's surface in the present, and in -former ages.</p> - -<p>107. The veins of tin furnish an argument of the same kind. The -ores of this metal are very indestructible, and little subject to -decomposition, so that they remain very long in the ground without -change. Where there are tin veins, as in Cornwall, the tin-stone or tin -ore is found in great abundance in such vallies and streams as have the -same direction with the veins; and hence the <i>streaming</i>, as it is -called, or washing of the earth, to obtain the tin-stone from it. Now, -if it be considered, that none of this ore can have come into the soil -but from parts of a vein actually destroyed, it must appear evident -that a great waste of these veins has taken place, and consequently of -the schistus or granite in which they are contained.</p> - -<p>108. These lessons, which the geologist is taught in flat and open -countries, become more striking, by the study of those Alpine tracts, -where the surface of the earth attains its greatest elevation. If we -suppose him placed for the first time in the midst of such a scene, -as soon as he has recovered from the impression made by the novelty -and magnificence of the spectacle before him, he begins to discover -the -<span class="pagenum" id="Page_111">- 111 -</span> footsteps of time, and to perceive, that the works of nature, -usually deemed the most permanent, are those on which the characters -of vicissitude are most deeply imprinted. He sees himself in the midst -of a vast ruin, where the precipices which rise on all sides with -such boldness and asperity, the sharp peaks of the granite mountains, -and the huge fragments that surround their bases, do but mark so many -epochs in the progress of decay, and point out the energy of those -destructive causes, which even the magnitude and solidity of such great -bodies have been unable to resist.</p> - -<p>109. The result of a more minute investigation, is in perfect unison -with this general impression. Whence is it, that the elevation -of mountains is so obviously connected with the hardness and -indestructibility of the rocks which compose them? Why is it, that a -lofty mountain of soft and secondary rock is no where to be found; and -that such chains, as the Pyrenees or the Alps, never consist of any but -the hardest stone, of granite for instance, or of those primary strata, -which, if we are to credit the preceding theory, have been twice heated -in the fires, and twice tempered in the waters, of the mineral regions? -Is it not plain that this arises, not from any direct connection -between the hardness of stones, and their height in the atmosphere, -<span class="pagenum" id="Page_112">- 112 -</span> -but from this, that the waste and <i>detritus</i> to which all things -are subject, will not allow soft and weak substances to remain long in -an exposed and elevated situation? Were it not for this, the secondary -rocks, being in position superincumbent on the primary, ought to be -the highest of the two, and should cover the primary, (as they no -doubt have at one time done,) in the highest as well as the lowest -situations, or among the mountains as well as in the plains.</p> - -<p>110. Again, wherefore is it, that among all mountains, remarkable for -their ruggedness and asperity, the rock, on examination, is always -found of very unequal destructibility, some parts yielding to the -weather, and to the other causes of disintegration, much more slowly -than the rest, and having strength sufficient to support themselves, -when left alone, in slender pyramids, bold projections, and overhanging -cliffs? Where, on the other hand, the rock wastes uniformly, the -mountains are similar to one another; their swells and slopes are -gentle, and they are bounded by a waving and continuous surface. The -intermediate degrees of resistance which the rocks oppose to the causes -of destruction, produce intermediate forms. It is this which gives to -the mountains, of every different species of rock, -<span class="pagenum" id="Page_113">- 113 -</span> a different habit -and expression, and which, in particular, has imparted to those of -granite that venerable and majestic character, by which they rarely -fail to be distinguished.</p> - -<p>111. The structure of the vallies among mountains, shows clearly to -what cause their existence is to be ascribed. Here we have first a -large valley, communicating directly with the plain, and winding -between high ridges of mountains, while the river in the bottom of it -descends over a surface, remarkable, in such a scene, for its uniform -declivity. Into this, open a multitude of transverse or secondary -vallies, intersecting the ridges on either side of the former, each -bringing a contribution to the main stream, proportioned to its -magnitude; and, except where a cataract now and then intervenes, -all having that nice adjustment in their levels, (99.) which is the -more wonderful, the greater the irregularity of the surface. These -secondary vallies have others of a smaller size opening into them; -and, among mountains of the first order, where all is laid out on the -greatest scale, these ramifications are continued to a fourth, and -even a fifth, each diminishing in size as it increases in elevation, -and as its supply of water is less. Through them all, this law is in -general observed, that where a higher valley joins a lower one, of the -two angles which -<span class="pagenum" id="Page_114">- 114 -</span> it makes with the latter, that which is obtuse is -always on the descending side; a law that is the same with that which -regulates the confluence of streams running on a surface nearly of -uniform inclination. This alone is a proof that the vallies are the -work of the streams; and indeed what else but the water itself, working -its way through obstacles of unequal resistance, could have opened or -kept up a communication between the inequalities of an irregular and -alpine surface?</p> - -<p>112. Many more arguments, all leading to the same conclusion, may -be deduced from the general facts, known in the natural history of -mountains; and, if the Oreologist would trace back the progress of -waste, till he come in sight of that original structure, of which -the remains are still so vast, he perceives an immense mass of solid -rock, naked and unshapely, as it first emerged from the deep, and -incomparably greater than all that is now before him. The operation -of rains and torrents, modified by the hardness and tenacity of the -rock, has worked the whole into its present form; has hollowed out -the vallies, and gradually detached the mountains from the general -mass, cutting down their sides into steep precipices at one place, -and smoothing them into gentle declivities at another. From this has -resulted a transportation of materials, which, both -<span class="pagenum" id="Page_115">- 115 -</span> for the quantity -of the whole, and the magnitude of the individual fragments, must seem -incredible to every one, who has not learned to calculate the effects -of continued action, and to reflect, that length of time can convert -accidental into steady causes. Hence fragments of rock, from the -central chain, are found to have travelled into distant vallies, even -where many inferior ridges intervene: hence the granite of Mont Blanc -is seen in the plains of Lombardy, or on the sides of Jura; and the -ruins of the Carpathian mountains lie scattered over the shores of the -Baltic.<a id="FNanchor_32" href="#Footnote_32" class="fnanchor">[32]</a></p> - -<div class="footnote"> - -<p><a id="Footnote_32" href="#FNanchor_32" class="label">[32]</a> <span class="smcap"><a href="#Note_xviii">Note xviii.</a></span></p> - -</div> - -<p>113. Thus, with Dr Hutton, we shall be disposed to consider those great -chains of mountains, which traverse the surface of the globe, as cut -out of masses vastly greater, and more lofty than any thing that now -remains. The present appearances afford no data for calculating the -original magnitude of these masses, or the height to which they may -have been elevated. The nearest estimate we can form is, where a chain -or group of mountains, like those of Rosa in the Alps, is horizontally -stratified, and where, of consequence, the undisturbed position of the -mineral beds enables us to refer the whole of the present inequalities -of the surface to the operation of waste or decay. These -<span class="pagenum" id="Page_116">- 116 -</span> mountains, -as they now stand, may not inaptly be compared to the pillars of earth -which workmen leave behind them, to afford a measure of the whole -quantity of earth which they have removed. As the pillars, (considering -the mountains as such,) are in this case of less height than they -originally were, so the measure furnished by them is but a limit, which -the quantity sought must necessarily exceed.</p> - -<p>114. Such, according to Dr Hutton's theory, are the changes which the -daily operations of waste have produced on the surface of the globe. -These operations, inconsiderable if taken separately, become great, by -conspiring all to the same end, never counteracting one another, but -proceeding, through a period of indefinite extent, continually in the -same direction. Thus every thing descends, nothing returns upward; the -hard and solid bodies every where dissolve, and the loose and soft no -where consolidate. The powers which tend to preserve, and those which -tend to change the condition of the earth's surface, are never <i>in -equilibrio</i>; the latter are, in all cases, the most powerful, and, -in respect of the former, are like living in comparison of dead forces. -Hence the law of decay is one which suffers no exception: The elements -of all bodies were once loose and unconnected, and to -<span class="pagenum" id="Page_117">- 117 -</span> the same state -nature has appointed that they should all return.</p> - -<p>115. It affords no presumption against the reality of this progress, -that, in respect of man, it is too slow to be immediately perceived: -The utmost portion of it to which our experience can extend, is -evanescent, in comparison with the whole, and must be regarded as the -momentary increment of a vast progression, circumscribed by no other -limits than the duration of the world. TIME performs the office of -integrating the infinitesimal parts of which this progression is made -up; it collects them into one sum, and produces from them an amount -greater than any that can be assigned.</p> - -<p>116. While on the surface of the earth so much is every where going to -decay, no new production of mineral substances is found in any region -accessible to man. The instances of what are called petrifactions, or -the formation of stony substances by means of water, which we sometimes -observe, whether they be ferruginous concretions, or calcareous, or, -as happens in some rare cases, siliceous stalactites, are too few -in number, and too inconsiderable in extent, to be deemed material -exceptions to this general rule. The bodies thus generated, also, are -no sooner formed, than they become subject to waste and dissolution, -like all the other hard substances in -<span class="pagenum" id="Page_118">- 118 -</span> nature; so that they but retard -for a while the progress by which they are all resolved into dust, and -sooner or later committed to the bosom of the deep.</p> - -<p>117. We are not, however, to imagine, that there is no where any means -of repairing this waste; for, on comparing the conclusion at which -we are now arrived, viz. that the present continents are all going -to decay, and their materials descending into the ocean, with the -proposition first laid down, that these same continents are composed -of materials which must have been collected from the decay of former -rocks, it is impossible not to recognise two corresponding steps of -the same progress; of a progress, by which mineral substances are -subjected to the same series of changes, and alternately wasted away -and renovated. In the same manner, as the present mineral substances -derive their origin from substances similar to themselves; so, from the -land now going to decay, the sand and gravel forming on the sea shore, -or in the beds of rivers; from the shells and corals, which in such -enormous quantities are every day accumulated in the bosom of the sea; -from the drift wood, and the multitude of vegetable and animal remains -continually deposited in the ocean: from all these we cannot doubt, -that strata are now forming in those regions, to -<span class="pagenum" id="Page_119">- 119 -</span> which nature seems -to have confined the powers of mineral reproduction; from which, after -being consolidated, they are again destined to emerge, and to exhibit a -series of changes similar to the past.<a id="FNanchor_33" href="#Footnote_33" class="fnanchor">[33]</a></p> - -<div class="footnote"> - -<p><a id="Footnote_33" href="#FNanchor_33" class="label">[33]</a> <span class="smcap"><a href="#Note_xix">Note xix.</a></span></p> - -</div> - -<p>118. How often these vicissitudes of decay and renovation have been -repeated, is not for us to determine: they constitute a series, of -which, as the author of this theory has remarked, we neither see the -beginning nor the end; a circumstance that accords well with what -is known concerning other parts of the economy of the world. In the -continuation of the different species of animals and vegetables that -inhabit the earth, we discern neither a beginning nor an end; and, -in the planetary motions, where geometry has carried the eye so far -both into the future and the past, we discover no mark, either of -the commencement or the termination of the present order.<a id="FNanchor_34" href="#Footnote_34" class="fnanchor">[34]</a> It is -unreasonable, indeed, to suppose, that such marks should any where -exist. The Author of nature has not given laws to the universe, which, -like the institutions of men, carry in themselves the elements of their -own destruction. He has not permitted, in his works, any symptom of -infancy or of old age, or any sign by which we may estimate either -their fixture or their past duration. He may put an end, as be no doubt -gave a beginning, -<span class="pagenum" id="Page_120">- 120 -</span> to the present system, at some determinate period; -but we may safely conclude, that this great <i>catastrophe</i> will not -be brought about by any of the laws now existing, and that it is not -indicated by any thing which we perceive.</p> - -<div class="footnote"> - -<p><a id="Footnote_34" href="#FNanchor_34" class="label">[34]</a> <span class="smcap"><a href="#Note_xx">Note xx.</a></span></p> - -</div> - -<p>119. To assert, therefore, that, in the economy of the world, we see -no mark, either of a beginning or an end, is very different from -affirming, that the world had no beginning, and will have no end. The -first is a conclusion justified by common sense, as well as sound -philosophy; while the second is a presumptuous and unwarrantable -assertion, for which no reason from experience or analogy can ever be -assigned. Dr Hutton might, therefore, justly complain of the uncandid -criticism, which, by substituting the one of these assertions for the -other, endeavoured to load his theory with the reproach of atheism -and impiety. Mr <span class="smcap">Kirwan</span>, in bringing forward this harsh and -ill-founded censure, was neither animated by the spirit, nor guided by -the maxims of true philosophy. By the spirit of philosophy, he must -have been induced to reflect, that such poisoned weapons as he was -preparing to use, are hardly ever allowable in scientific contest, as -having a less direct tendency to overthrow the system, than to hurt -the person of an adversary, and to wound, perhaps incurably, his mind, -his reputation, or his peace. -<span class="pagenum" id="Page_121">- 121 -</span> By the maxims of philosophy, he must -have been reminded, that, in no part of the history of nature, has any -mark been discovered, either of the beginning or the end of the present -<i>order</i>; and that the geologist sadly mistakes, both the object -of his science and the limits of his understanding, who thinks it his -business to explain the means employed by <span class="smcap">infinite wisdom</span> for -establishing the laws which now govern the world.</p> - -<p>By attending to these obvious considerations, Mr Kirwan would have -avoided a very illiberal and ungenerous proceeding; and, however he -might have differed from Dr Hutton as to the <i>truth</i> of his -opinions, he would not have censured their <i>tendency</i> with such -rash and unjustifiable severity.</p> - -<p>But, if this author may be blamed for wanting the temper, or neglecting -the rules, of philosophic investigation, he is hardly less culpable, -for having so slightly considered the scope and spirit of a work which -he condemned so freely. In that work, instead of finding the world -represented as the result of necessity or chance, which might be looked -for, if the accusations of atheism or impiety were well founded, we -see every where the utmost attention to discover, and the utmost -disposition to admire, the instances of wise and beneficent design -<span class="pagenum" id="Page_122">- 122 -</span> -manifested in the structure, or economy of the world. The enlarged -views of these, which his geological system afforded, appeared to Dr -Hutton himself as its most valuable result. They were the parts of it -which he contemplated with greatest delight; and he would have been -less flattered, by being told of the ingenuity and originality of his -theory, than of the addition which it had made to our knowledge of -<i>final causes</i>. It was natural, therefore, that he should be hurt -by an attempt to accuse him of opinions, so different from those which -he had always taught; and if he answered Mr Kirwan's attack with warmth -or asperity, we must ascribe it to the indignation excited by unmerited -reproach.</p> - -<p>120. But to return to the natural history of the earth: Though there -be in it no <i>data</i>, from which the commencement of the present -order can be ascertained, there are many by which the existence of -that order may be traced back to an antiquity extremely remote. The -beds of primitive schistus, for instance, contain sand, gravel, and -other materials, collected, as already shown, from the dissolution of -mineral bodies; which bodies, therefore, must have existed long before -the oldest part of the present land was formed. Again, in this gravel -we sometimes find pieces of sandstone, and of other compound rocks, by -which we are of course carried back a step farther, so as to reach -<span class="pagenum" id="Page_123">- 123 -</span> a -system of things, from which the present is the third in succession; -and this may be considered as the most ancient epocha, of which any -memorial exists in the records of the fossil kingdom.</p> - -<p>121. Next in the order of time to the consolidation of the primary -strata, we must place their elevation, when, from being horizontal, and -at the bottom of the sea, they were broken, set on edge, and raised to -the surface. It is even probable, as formerly observed, that to this -succeeded a depression of the same strata, and a second elevation, -so that they have twice visited the superior, and twice the inferior -regions. During the second immersion, were formed, first, the great -bodies of pudding-stone, that in so many instances lie immediately -above them; and next were deposited the strata that are strictly -denominated secondary.</p> - -<p>122. The third great event, was the raising up of this compound body of -old and new strata from the bottom of the sea, and forming it into the -dry land, or the continents, as they now exist.<a id="FNanchor_35" href="#Footnote_35" class="fnanchor">[35]</a> Contemporary with -this, we must suppose the injection of melted matter among the strata, -and the consequent formation of the crystallized and unstratified -rocks, namely, the granite, metallic veins, and veins of porphyry and -<span class="pagenum" id="Page_124">- 124 -</span> -whinstone. This, however, is to be considered as embracing a period -of great duration; and it must always be recollected, that veins are -found of very different formation; so that when we speak generally, it -is perhaps impossible to state any thing more precise concerning their -antiquity, than that they are posterior to the strata, and that the -veins of whinstone seem to be the most recent of all, as they traverse -every other.</p> - -<div class="footnote"> - -<p><a id="Footnote_35" href="#FNanchor_35" class="label">[35]</a> <span class="smcap"><a href="#Note_xxi">Note xxi.</a></span></p> - -</div> - -<p>123. In the fourth place, with respect to time, we must class the -facts that regard the detritus and waste of the land, and must -carefully distinguish them from the more ancient phenomena of the -mineral kingdom. Here we are to reckon the shaping of all the present -inequalities of the surface; the formation of hills of gravel, and -of what have been called tertiary strata, consisting of loose and -unconsolidated materials; also collections of shells not mineralised, -like those in Turaine; such petrifactions as those contained in the -rock of Gibraltar, on the coast of Dalmatia, and in the caves of -Bayreuth. The bones of land animals found in the soil, such as those -of Siberia, or North America, are probably more recent than any of the -former.<a id="FNanchor_36" href="#Footnote_36" class="fnanchor">[36]</a></p> - -<div class="footnote"> - -<p><a id="Footnote_36" href="#FNanchor_36" class="label">[36]</a> <span class="smcap"><a href="#Note_xxii">Note xxii.</a></span></p> - -</div> - -<p>124. These phenomena, then, are all so many marks of the lapse of -time, among which the principles of geology enable us to distinguish -a -<span class="pagenum" id="Page_125">- 125 -</span> certain order, so that we know some of them to be more, and others -to be less distant, but without being able to ascertain, with any -exactness, the proportion of the immense intervals which separate them. -These intervals admit of no comparison with the astronomical measures -of time; they cannot be expressed by the revolutions of the sun or of -the moon; nor is there any synchronism between the most recent epoch as -of the mineral kingdom, and the most ancient of our ordinary chronology.</p> - -<p>125. On what is now said is grounded another objection to Dr Hutton's -theory, namely, that the high antiquity ascribed by it to the earth, -is inconsistent with that system of chronology which rests on the -authority of the Sacred Writings. This objection would no doubt be of -weight, if the high antiquity in question were not restricted merely to -the globe of the earth, but were also extended to the human race. That -the origin of mankind does not go back beyond six or seven thousand -years, is a position so involved in the narrative of the Mosaic books, -that any thing inconsistent with it, would no doubt stand in opposition -to the testimony of those ancient records. On this subject, however, -geology is silent; and the history of arts and sciences, when traced -as high as any authentic monuments extend, refers -<span class="pagenum" id="Page_126">- 126 -</span> the beginnings of -civilization to a date not very different from that which has just been -mentioned, and infinitely within the limits of the most recent of the -epoch as, marked by the physical revolutions of the globe.</p> - -<p>On the other hand, the authority of the Sacred Books seems to be but -little interested in what regards the mere antiquity of the earth -itself; nor does it appear that their language is to be understood -literally concerning the <i>age</i> of that body, any more than -concerning its <i>figure</i> or its <i>motion</i>. The theory of Dr -Hutton stands here precisely on the same footing with the system of -<span class="smcap">Copernicus</span>; for there is no reason to suppose, that it was -the purpose of revelation to furnish a standard of geological, any -more than of astronomical science. It is admitted, on all hands, that -the Scriptures are not intended to resolve physical questions, or to -explain matters in no way related to the morality of human actions; -and if, in consequence of this principle, a considerable latitude of -interpretation were not allowed, we should continue at this moment to -believe, that the earth is flat; that the sun moves round the earth; -and that the circumference of a circle is no more than three times its -diameter.</p> - -<p>It is but reasonable, therefore, that we should extend to the -geologist the same liberty of speculation, -<span class="pagenum" id="Page_127">- 127 -</span> which the astronomer and -mathematician are already in possession of; and this may be done, by -supposing that the chronology of <span class="smcap">Moses</span> relates only to the -human race. This liberty is not more necessary to Dr Hutton than to -other theorists. No ingenuity has been able to reconcile the natural -history of the globe with the opinion of its recent origin; and -accordingly the cosmologies of Kirwan and De Luc, though contrived with -more mineralogical skill, are not less forced and unsatisfactory than -those of Burnet and Whiston.</p> - -<p>126. It is impossible to look back on the system which we have thus -endeavoured to illustrate, without being struck with the novelty and -beauty of the views which it sets before us. The very plan and scope -of it distinguish it from all other theories of the earth, and point -it out as a work of great and original invention. The sole object of -such theories has hitherto been, to explain the manner in which the -present laws of the mineral kingdom were first established, or began -to exist, without treating of the manner in which they now proceed, -and by which their continuance is provided for. The authors of these -theories have accordingly gone back to a state of things altogether -unlike the present, and have confined their reasonings, or -<span class="pagenum" id="Page_128">- 128 -</span> their -fictions, to a crisis which never has existed but once, and which never -can return. Dr Hutton, on the other hand, has guided his investigation -by the philosophical maxim, <i>Causam naturalem et assiduam quærimus, -non raram et fortuitam</i>. His theory, accordingly, presents us with -a system of wise and provident economy, where the same instruments are -continually employed, and where the decay and renovation of fossils -being carried on at the same time in the different regions allotted to -them, preserve in the earth the conditions essential for the support of -animal and vegetable life. We have been long accustomed to admire that -beautiful contrivance in nature, by which the water of the ocean, drawn -up in vapour by the atmosphere, imparts, in its descent, fertility -to the earth, and becomes the great cause of vegetation and of life; -but now we find, that this vapour not only fertilizes, but creates -the soil; prepares it from the solid rock, and, after employing it in -the great operations of the surface, carries it back into the regions -where all its mineral characters are renewed. Thus, the circulation -of moisture through the air, is a prime mover, not only in the annual -succession of the seasons, but in the great geological cycle, by which -the waste and reproduction of entire continents is circumscribed. -Perhaps a more striking view than this, of the wisdom -<span class="pagenum" id="Page_129">- 129 -</span> that presides -over nature, was never presented by any philosophical system, nor a -greater addition ever made to our knowledge of final causes. It is an -addition which gives consistency to the rest, by proving, that equal -foresight is exerted in providing for the whole and for the parts, -and that no less a care is taken to maintain the constitution of the -earth, than to preserve the tribes of animals and vegetables which -dwell on its surface. In a word, it is the peculiar excellence of this -theory, that it ascribes to the phenomena of geology an order similar -to that which exists in the provinces of nature with which we are best -acquainted; that it produces seas and continents, not by accident, -but by the operation of regular and uniform causes; that it makes -the decay of one part subservient to the restoration of another, and -gives stability to the whole, not by perpetuating individuals, but by -reproducing them in succession.</p> - -<p>127. Again, in the detail of this theory, and the ample induction on -which it is founded, we meet with many facts and observations, either -entirely new, or hitherto very imperfectly understood. Thus, the veins -which proceed from masses of granite, and penetrate the incumbent -schistus, had either escaped the observation of former mineralogists, -or the importance of the phenomenon had been entirely overlooked. Dr -<span class="pagenum" id="Page_130">- 130 -</span> -Hutton has described the appearances with great accuracy, and drawn -from them the most interesting conclusions. At the junction of the -primary and secondary strata, the facts which he has noted had been -observed by others; but no one I think had so fully understood the -language which they speak, or had so clearly perceived the consequences -that necessarily follow from them. He is the first who distinctly -pointed out the characters which distinguish whinstone from lava, and -who explained the true relation that subsists between these substances. -He also discovered the induration of the strata, in contact with veins -of whin, and the charring of the coal in their vicinity. His theory -also enabled him to determine the affinity of whinstone and granite -to one another, and their relation to the other great bodies of the -mineral kingdom.</p> - -<p>To the observations of the same excellent geologist, we are indebted -for the knowledge of the general and important fact, that all the hard -substances of the mineral kingdom, when elevated into the atmosphere, -have a tendency to decay, and are subject to a disintegration -and waste, to which no limit can be set but that of their entire -destruction; that no provision is made on the surface for repairing -this waste, and that there, no new fossil is produced; that the -formation of all the varied scenery which the -<span class="pagenum" id="Page_131">- 131 -</span> surface of the earth -exhibits, depends on the operation of causes, the momentary exertions -of which are familiar to us, though we knew not before the effects -which their accumulated action was able to produce. These are facts in -the natural history of the earth, the discovery of which is due to Dr -Hutton; and, should we lay all further speculation aside, and consider -the theory of the earth as a work too great to be attempted by man, we -must still regard the phenomena and laws just mentioned, as forming a -solid and valuable addition to our knowledge.</p> - -<p>128. If we would compare this theory with others, as to the invisible -agents which it employs, we must consider, that fire and water are the -two powers which all of them must make use of, so that they can differ -from one another only by the way in which they combine these powers. -In Dr Hutton's system, water is first employed to deposit and arrange, -and then fire to consolidate, mineralize, and lastly, to elevate -the strata; but with respect to the unstratified or crystallized -substances, the action of fire only is recognised. The system having -least affinity to this is the Neptunian, which ascribes the formation -of all minerals to the action of water alone, and extends this -hypothesis even to the unstratified rocks. Here, therefore, the action -of fire is entirely excluded; and the Neptunists -<span class="pagenum" id="Page_132">- 132 -</span> have certainly made a -great sacrifice to the love of truth, or of paradox, in rejecting the -assistance of so powerful an auxiliary.<a id="FNanchor_37" href="#Footnote_37" class="fnanchor">[37]</a></p> - -<div class="footnote"> - -<p><a id="Footnote_37" href="#FNanchor_37" class="label">[37]</a> <span class="smcap"><a href="#Note_xxiii">Note xxiii.</a></span></p> - -</div> - -<p>129. In the systems which employ the agency of the latter element, we -are to look for a greater resemblance to that of Dr Hutton, though -many and great marks of distinction are easily perceived. In the -cosmologies, for example, of <span class="smcap">Leibnitz</span> and <span class="smcap">Buffon</span>, -fire and water are both employed, as well as in this; but they are -employed in a reverse order. These philosophers introduce the action -of fire first, and then the action of water, which is to invert the -order of nature altogether, as the consolidation of the rocks must be -posterior to their stratification. Indeed, the theory of Buffon is -singularly defective: besides inverting the order of the two great -operations of stratification and consolidation, and of course giving no -real explanation of the latter, it gives no account of the elevation, -or highly inclined position of the strata; it makes no distinction -between stratified and unstratified bodies, nor does it offer any but -the most unsatisfactory explanation of the inequalities of the earth's -surface. This system, therefore, has but a very distant resemblance to -the Huttonian theory.<a id="FNanchor_38" href="#Footnote_38" class="fnanchor">[38]</a></p> - -<div class="footnote"> - -<p><a id="Footnote_38" href="#FNanchor_38" class="label">[38]</a> <span class="smcap"><a href="#Note_xxiv">Note xxiv.</a></span></p> - -</div> - -<p>130. The system of <span class="smcap">Lazzaro Moro</span> has been remarked as -approaching nearer to this theory -<span class="pagenum" id="Page_133">- 133 -</span> than any other; and it is certain, -that one very important principle is common to them both. The theory -of the Italian geologist was chiefly directed to the explanation of -the remains of marine animals, which are found in mountains far from -the sea; and it appears to have been suggested to him by the phenomena -of the <i>Campi Phlegræi</i>, and by the production of the new island -of <i>Santorini</i> in the Archipelago. He accordingly supposes, -that the islands and continents have been all raised up, like the -above-mentioned island, from the bottom of the sea, by the force of -volcanic fire: that these fires began to burn under the bottom of the -ocean, soon after the creation of the world, when as yet the ocean -covered the whole earth: that they at first elevated a portion of the -land; and in this primitive land no shells are found, as the original -ocean was destitute of fish. The volcanoes continuing to burn, under -the sea, after the creation of animated nature, the strata that were -then raised up by their action were full of shells and other marine -objects; and, from the violence with which they were elevated, arose -the contortions and inclined position which they frequently possess.<a id="FNanchor_39" href="#Footnote_39" class="fnanchor">[39]</a></p> - -<div class="footnote"> - -<p><a id="Footnote_39" href="#FNanchor_39" class="label">[39]</a> Dé Crostacei, et degli altri Marini Corpi, che si trovano -su' Monti: di Ant. Lazzaro Moro. Venezia. 1740.</p> - -</div> - -<p><span class="pagenum" id="Page_134">- 134 -</span></p> - -<p>This system is imperfect, as it makes no peculiar provision for the -consolidation of the strata, which, according to it, as well as the -Neptunian system, must be ascribed to the action, not of fire, but of -water. No account is given of the mineralization of the shells found -in the strata, or of the difference between them and the shells found -loose at the bottom of the sea; and no distinction is made between -stratified and unstratified substances. But, with all this, Lazzaro -Moro has certainly the merit of having perceived, that some other power -than that which deposited the strata, must have been employed for their -elevation, and that they have endured the action of a disturbing force.</p> - -<p>131. From this comparison it appears, that Dr Hutton's theory is -sufficiently distinct, even from the theories which approach to it most -nearly, to merit, in the strictest sense, the appellation of <i>new</i> -and <i>original</i>. There are indeed few inventions or discoveries, -recorded in the history of science, to which nearer approaches were not -made before they were fully unfolded. It therefore very well deserves -to be distinguished by a particular name; and, if it behoves us to -follow the analogy observed in the names of the two great systems, -which at present divide the opinions of geologists, we may join Mr -Kirwan in calling this the <span class="smcap">Plutonic System</span>. For -<span class="pagenum" id="Page_135">- 135 -</span> my own part, -I would rather have it characterized by a less splendid, but juster -name, that of the <span class="smcap">Huttonian Theory</span>.</p> - -<p>132. The circumstance, however, which gives to this theory its -peculiar character, and exalts it infinitely above all others, is -the introduction of the principle of pressure, to modify the effects -of heat when applied at the bottom of the sea. This is in fact the -key to the grand enigma of the mineral kingdom, where, while one -set of phenomena indicates the action of fire, another set, equally -remarkable, seems to exclude the possibility of that action, by -presenting us with mineral substances, in such a state as they could -never have been brought into by the operation of the fires we see at -the surface of the earth. These two classes of phenomena are reconciled -together, by admitting the power of compression to confine the volatile -parts of bodies when heat is applied to them, and to force them, -in many instances, to undergo fusion, instead of being calcined or -dissipated by burning or inflammation. In this hypothesis, which some -affect to consider as a principle gratuitously assumed, there appears -to me nothing but a very fair and legitimate generalization of the -properties of heat. Combustion and inflammation are chemical processes, -to which other conditions are required, besides the presence of a high -temperature. The -<span class="pagenum" id="Page_136">- 136 -</span> state of the mineral regions makes it reasonable -to presume, that these conditions are wanting in the bowels of the -earth, where, of consequence, we have a right to look for nothing but -expansion and fusion, the only operations which seem essential to -heat, and inseparable from the application of it, in certain degrees, -to certain substances. Though this principle, therefore, had no -countenance from analogy, the admirable simplicity, and the unity, -which it introduces into the phenomena of geology, would sufficiently -justify the application of it to the theory of the earth.</p> - -<p>As another excellence of this theory, I may, perhaps, be allowed to -remark, that it extends its consequences beyond those to which the -author of it has himself adverted, and that it affords, which no -geological theory has yet done, a satisfactory explanation of the -spheroidal figure of the earth.<a id="FNanchor_40" href="#Footnote_40" class="fnanchor">[40]</a></p> - -<div class="footnote"> - -<p><a id="Footnote_40" href="#FNanchor_40" class="label">[40]</a> <span class="smcap"><a href="#Note_xxv">Note xxv.</a></span></p> - -</div> - -<p>133. Yet, with all these circumstances of originality, grandeur, -and simplicity in its favour, with the addition of evidence as -demonstrative as the nature of the subject will admit, this theory -has probably many obstacles to overcome, before it meet the general -approbation. The greatness of the objects which it sets before us, -alarms the imagination; the powers which it supposes to be lodged -in the subterraneous regions; -<span class="pagenum" id="Page_137">- 137 -</span> a heat which has subdued the most -refractory rocks, and has melted beds of marble and quartz; an -expansive force, which has folded up, or broken the strata, and raised -whole continents from the bottom of the sea; these are things with -which, however certainly they may be proved, the mind cannot soon -be familiarized. The change and movement also, which this theory -ascribes to all that the senses declare to be most unalterable, raise -up against it the same prejudices which formerly opposed the belief -in the true system of the world; and it affords a curious proof, how -little such prejudices are subject to vary, that as Aristarchus, an -ancient follower of that system, was charged with impiety for moving -the everlasting Vesta from her place, so Dr Hutton, nearly on the same -ground, has been subjected to the very same accusation. Even the length -of time which this theory regards as necessary to the revolutions of -the globe, is looked on as belonging to the marvellous; and man, who -finds himself constrained by the want of time, or of space, in almost -all his undertakings, forgets, that in these, if in any thing, the -riches of nature reject all limitation.<a id="FNanchor_41" href="#Footnote_41" class="fnanchor">[41]</a></p> - -<div class="footnote"> - -<p><a id="Footnote_41" href="#FNanchor_41" class="label">[41]</a> <span class="smcap"><a href="#Note_xxvi">Note xxvi.</a></span></p> - -</div> - -<p>The evidence which must be opposed to all these causes of incredulity, -cannot be fully understood without much study and attention. -<span class="pagenum" id="Page_138">- 138 -</span> It -requires not only a careful examination of particular instances, but -comprehensive views of the whole phenomena of geology; the comparison -of things very remote with one another; the interpretation of the -<i>obscure</i> by the <i>luminous</i>, and of the <i>doubtful</i> by -the <i>decisive</i> appearances. The geologist must not content himself -with examining the insulated specimens of his cabinet, or with pursuing -the nice subtleties of mineralogical arrangement; he must study the -relations of fossils, as they actually exist; he must follow nature -into her wildest and most inaccessible abodes; and must select, for the -places of his observations, those points, from which the variety and -gradation of her works can be most extensively and accurately explored. -Without such an exact and comprehensive survey, his mind will hardly be -prepared to relish the true theory of the earth. "<i>Naturæ enim vis -atque majestas omnibus momentis fide caret, si quis modo partes atque -non totam complectatur animo</i>".<a id="FNanchor_42" href="#Footnote_42" class="fnanchor">[42]</a></p> - -<div class="footnote"> - -<p><a id="Footnote_42" href="#FNanchor_42" class="label">[42]</a> <span class="smcap">Plin.</span> Hist. Nat. lib. vii. Cap. i.</p> - -</div> - -<p id="sec_134">134. If indeed this theory of the earth is as well founded as we -suppose it to be, the lapse of time must necessarily remove all -objections to it, and the progress of science will only develope its -evidence more fully. As it stands at present, -<span class="pagenum" id="Page_139">- 139 -</span> though true, it must be -still imperfect; and it cannot be doubted, that the great principles -of it, though established on an immoveable basis, must yet undergo -many modifications, requiring to be limited, in one place, or to be -extended, in another. A work of such variety and extent cannot be -carried to perfection by the efforts of an individual. Ages may be -required to fill up the bold outline which Dr Hutton has traced with so -masterly a hand; to detach the parts more completely from the general -mass; to adjust the size and position of the subordinate members; and -to give to the whole piece the exact proportion and true colouring of -nature.</p> - -<p class="pmb4">This, however, in length of time, may be expected from the advancement -of science, and from the mutual assistance which parts of knowledge, -seemingly the most remote, often afford to one another. Not only -may the observations of the mineralogist, in tracts yet unexplored, -complete the enumeration of geological facts; and the experiments of -the chemist, on substances not yet subjected to his analysis, afford a -more intimate acquaintance with the nature of fossils, and a measure -of the power of those chemical agents to which this theory ascribes -such vast effects: but also, from other sciences, less directly -connected with the natural history -<span class="pagenum" id="Page_140">- 140 -</span> of the earth, much information may -be received. The accurate geographical maps and surveys which are now -making; the foundings; the obsevations of currents; the barometrical -measurements, may all combine to ascertain the reality, and to fix the -quantity of those changes which terrestrial bodies continually undergo. -Every new improvement in science affords the means of delineating more -accurately the face of nature as it now exists, and of transmitting, to -future ages, an account, which may be compared with the face of nature -as it shall then exist. If, therefore, the science of the present -times is destined to survive the physical revolutions of the globe, -the <span class="smcap">Huttonian Theory</span> may be confirmed by historical record; -and the author of it will be remembered among the illustrious few, -whose systems have been verified by the observations of succeeding -ages, supported by facts unknown to themselves, and established by -the decisions of a tribunal, slow, but infallible, in distinguishing -between truth and falsehood.</p> - - -<p><span class="pagenum" id="Page_141">- 141 -</span></p> - -<div class="figcenter" style="width: 400px;"> - <img src="images/bar_double_v3.png" width="400" height="15" alt="" /> -</div> - -<div class="chapter"> -<p><span class="pagenum" id="Page_143">- 143 -</span></p> -<h2 class="pmt4 pmb4 nobreak" id="NOTES_and_ADDITIONS"><span class="smcap">NOTES and ADDITIONS.</span></h2> -</div> - -<div class="figcenter" style="width: 400px;"> - <img src="images/bar_double_v4.png" width="400" height="15" alt="" /> -</div> - - - - -<div class="chapter"> -<h2 class="pmt4 pmb2 nobreak" id="Note_i"><span class="smcap">Note i. § 2.</span></h2> -</div> - -<p class="caption3nb"><i>Origin of calcareous rocks.</i></p> - -<div class="fl_left"> -<span class="num_left">135.</span> <span class="vbig">I</span> -</div> - -<p><a id="sec_135"></a><span class="hidden">134. I</span>T has been asserted, that Dr Hutton went farther than -is stated at § 2, and maintained all calcareous matter to be -<i>originally</i> of animal formation. This position, however, is so -far from being laid down by Dr Hutton, that it belongs to an inquiry -which he carefully avoided to enter on, as being altogether beyond the -limits of philosophical investigation.</p> - -<p>He has indeed no where treated of the <i>first origin</i> of any of the -earths, or of any substance whatsoever, but only of the transformations -which bodies have undergone since the present laws of nature were -established. He considered this last as all that a science, built on -experiment and observation, can possibly extend to; and willingly left, -to more presumptuous inquirers, the task of carrying their reasonings -beyond the boundaries of nature, and of unfolding the properties of -the chaotic fluid, with as much minuteness of detail, as if they were -describing -<span class="pagenum" id="Page_144">- 144 -</span> the circumstances of a chemical process which they had -actually witnessed.</p> - -<p>The idea of calcareous matter which really belongs to the Huttonian -Theory, is, that in all the changes which the terraqueous globe has -undergone in past ages, this matter existed, as it does now, either -in the form of limestone and marble, or in the composition of other -stones, or in the state of corals, shells, and bones of animals. It may -be true, that there is no particle of calcareous matter, at present -existing on the surface of the earth, that has not, at some time, made -a part of an animal body; but of this we can have no certainty, nor is -it of any importance that we should. It is enough to know, that the -rocks of marble and limestone contain in general marks of having been -formed from materials collected at the bottom of the sea; and of this -a single cockle-shell, or piece of coral, found included in a rock, is -a sufficient proof with respect to the whole mass of which it makes a -part.</p> - -<p>The principal object which Dr Hutton had in view when he spoke of the -masses of marble and limestone, as composed of the calcareous matter -of marine bodies,<a id="FNanchor_43" href="#Footnote_43" class="fnanchor">[43]</a> was to prove, that they had been all formed -at the bottom of -<span class="pagenum" id="Page_145">- 145 -</span> the sea, and from materials there deposited. His -general conclusion is, "That all the strata of the earth, not only -those consisting of such calcareous masses, but others superincumbent -upon these, have had their origin at the bottom of the sea, by the -collection of sand and gravel, of shells, of coralline and crustaceous -bodies, and of earths and clays variously mixed, or separated and -accumulated. This is a general conclusion, well authenticated by the -appearances of nature, and highly important in the natural history of -the earth."<a id="FNanchor_44" href="#Footnote_44" class="fnanchor">[44]</a></p> - -<div class="footnote"> - -<p><a id="Footnote_43" href="#FNanchor_43" class="label">[43]</a> Theory of the Earth, vol. i. p. 23, 24.</p> - -<p><a id="Footnote_44" href="#FNanchor_44" class="label">[44]</a> Theory of the Earth, vol. i. p. 26.</p> - -</div> - -<p>136. In his Geological Essays, Mr Kirwan says, that "some geologists, -as Buffon, and of late Dr Hutton, have excluded calcareous earth -from the number of the primeval, asserting the masses of it we at -present behold to proceed from shell-fish. But, in addition to the -unfounded supposition, that shell-fish, or any animals, possess the -power of producing any simple earth, these philosophers should have -considered, that, before the existence of any fish, the stony masses -that inclose the bason of the sea, must have existed; and, among -these, there is none in which calcareous earth is not found. Dr Hutton -endeavours to <i>evade</i> this argument, by supposing the world we now -inhabit to have arisen from the -<span class="pagenum" id="Page_146">- 146 -</span> ruins and fragments of an anterior, -without pointing at any original. If we are thus to proceed <i>in -infinitum</i>, I shall not pretend to follow him; but, if he stops any -where, he will find the same argument equally to occur."<a id="FNanchor_45" href="#Footnote_45" class="fnanchor">[45]</a></p> - -<div class="footnote"> - -<p><a id="Footnote_45" href="#FNanchor_45" class="label">[45]</a> Geol. Essays, p. 13.</p> - -</div> - -<p>The argument here employed would certainly be conclusive against any -one, who, in disputing about the <i>first origin</i> of things, should -deny that the calcareous is as ancient as any other of the simple -earths. But this has nothing to do with Dr Hutton's speculations, -which, as has been just said, never extended to the <i>first origin</i> -of substances, but were confined entirely to their changes; so that -what he asserts concerning the calcareous rocks, is no more than -that those which we now see have been formed from loose materials, -deposited at the bottom of the sea. It was not therefore in order to -<i>evade</i> Mr Kirwan's argument, as the preceding passage would lead -us to believe, that he supposed the world which we now inhabit to -have arisen from the ruin and waste of an anterior world; but it was -because this seemed to him a conclusion which necessarily followed from -the phenomena of geology, and it was a conclusion that he had deduced -long before he heard of Mr Kirwan's objections to his system. Instead -of an <i>evasion</i>, -<span class="pagenum" id="Page_147">- 147 -</span> therefore, any one who considers the subject -fairly, will see, in Dr Hutton's reasoning, nothing but the caution of -a philosopher, who wisely confines his theory within the same limits by -which nature has confined his experience and observation.</p> - -<p>It is nevertheless true, that Dr Hutton has sometimes expressed himself -as if he thought that the present calcareous rocks are all composed of -animal remains.<a id="FNanchor_46" href="#Footnote_46" class="fnanchor">[46]</a> This conclusion, however, is more general than the -facts warrant; and, from some incorrectness or ambiguity of language, -is certainly more general than he intended. The idea of calcareous -rocks, on which he argues throughout his whole theory, is precisely -that which is stated in the preceding article.</p> - -<div class="footnote"> - -<p><a id="Footnote_46" href="#FNanchor_46" class="label">[46]</a> Theory of the Earth, vol. i. p. 23.</p> - -</div> - - -<hr class="chap x-ebookmaker-drop" /> - -<div class="chapter"> -<h2 class="nobreak" id="Note_ii"><span class="smcap">Note ii. § 6.</span></h2> -</div> - -<p class="caption3nb"><i>Origin of coal.</i></p> - - -<p>137. The vegetable origin of coal seems to be sufficiently proved by -the reasoning in § 5. and 6.; and that reasoning will appear still -more satisfactory, from what is said at § 28. and 29., concerning the -consolidation of this fossil. Dr Hutton has treated both of the matter -of coal -<span class="pagenum" id="Page_148">- 148 -</span> and of its consolidation. Part. I. Chap. 8., of his Theory of -the Earth <a id="FNanchor_47" href="#Footnote_47" class="fnanchor">[47]</a>.</p> - -<div class="footnote"> - -<p><a id="Footnote_47" href="#FNanchor_47" class="label">[47]</a> Vol. i. p. 558, &c.</p> - -</div> - -<p>The notion, however, that coal is of vegetable origin, is not peculiar -to this theory, but has been for some time the prevailing opinion. -Buffon supposes this mineral to be formed from vegetable and animal -substances, the oil and fat of which have been converted into bitumen -by the action of acids.<a id="FNanchor_48" href="#Footnote_48" class="fnanchor">[48]</a> A fundamental mistake, however, is -committed by this author, and by M. <span class="smcap">Gensanne</span>, (author of the -natural history of Languedoc,) on whose observations he greatly relies, -in considering coal as consisting of bitumen united to earth, thus -omitting the only ingredient essential to coal, namely the carbon or -charcoal. This may truly be considered as the essential part, because -coal may exist without bitumen, as in the instance of blind coal, but -not without charcoal.</p> - -<div class="footnote"> - -<p><a id="Footnote_48" href="#FNanchor_48" class="label">[48]</a> Hist. Nat. des Mineraux. tom. i. p. 429, 4to edit.</p> - -</div> - -<p>Another theory of coal, very analogous to Dr Hutton's, is that of -<span class="smcap">Arduino</span>, professor of mineralogy at Venice, in which he -supposes it formed from vegetable and animal remains from the land -and sea, but chiefly from the latter.<a id="FNanchor_49" href="#Footnote_49" class="fnanchor">[49]</a> -<span class="pagenum" id="Page_149">- 149 -</span> This theory of coal is -contained in Dr Hutton's, in which the animal and vegetable remains -must be supposed to come both from the earth and the sea. It seems to -be without any good reason that Arduino considers the sea as the chief -source of these materials. His remarks, however, are very ingenious, -and deserving of attention.</p> - -<div class="footnote"> - -<p><a id="Footnote_49" href="#FNanchor_49" class="label">[49]</a> Saggio Fisico-mineralogico del Sig. Giov. Arduino; Atti -di Siena, tom. v. p. 228, 281, &c.</p> - -</div> - -<p>These accounts of the origin of coal are all nearly the same; it is -in what relates to the distinction between the common coal, in which -there is no ligneous structure, and those varieties of it in which that -structure is apparent, and again in explaining the consolidation of -both, that the theory laid down here is peculiar.</p> - -<p>138. Some other mineralogists refer one of the ingredients of coal -to the vegetable kingdom, but not the other. Unable to resist the -conviction which arises from the fibrous structure of parts of strata, -and even entire strata of coal, they have supposed, that wood, which -had been somehow buried in the earth, or perhaps deposited at the -bottom of the sea, had become impregnated with bitumen, which last, -however, they consider as of mineral origin. This appears to be the -opinion of Lehman; and also of some very late writers. There seems, -however, to be hardly less reason for referring the origin of one part -of coal to the vegetable or animal kingdom -<span class="pagenum" id="Page_150">- 150 -</span> than another. The two last -are certainly capable of furnishing both the carbonic and bituminous -parts; and therefore, to derive these from different sources, is at -least a very unnecessary complication of hypotheses.</p> - -<p>139. Another explanation of coal, very different from any of the -preceding, has lately been advanced and set up in opposition to the -Huttonian Theory. Mr Kirwan,<a id="FNanchor_50" href="#Footnote_50" class="fnanchor">[50]</a> the only mineralogist, I believe, who -has attempted to derive both the carbonic and bituminous matter of coal -from the mineral kingdom, distinguishes between wood coal and mineral -coal, and gives a theory entirely new of the formation of the latter. -Wood coal is that in which the ligneous structure is so apparent, as to -leave no doubt of its vegetable origin; mineral coal is that in which -no such structure can be discovered, and is the same which Dr Hutton -derives from the vegetable juices, and other remains, comminuted, -dispersed, carried into the sea, and there precipitated, so as to -unite with different proportions of earth, and to become afterwards -mineralized.</p> - -<div class="footnote"> - -<p><a id="Footnote_50" href="#FNanchor_50" class="label">[50]</a> Geol. Essays, essay vii. p. 290.</p> - -</div> - -<p>These two species of coal, which the Huttonian theory considers as -gradations of the same substance, Mr Kirwan regards as perfectly -distinct, constituting two minerals, of an origin -<span class="pagenum" id="Page_151">- 151 -</span> and formation -entirely different. He therefore endeavours to ascertain the -distinguishing characters of each, considered geologically.</p> - -<p><a id="sec_140"></a>140. But here the leading distinction, implied in all the rest, that -the two kinds of coal are never found in the same bed, but always in -different situations, and with different laws of stratification, is -expressly contradicted by matter of fact. Coal, as is said above, with -its ligneous texture quite apparent, and coal with no such structure -visible, are often found in the same seam, are brought up from the same -mine, and united in the same specimen. I have a specimen from a bed of -coal, in the Isle of Sky, found under a basaltic rock, consisting of a -ligneous part, which graduates into one in which there is no vestige -of a fibrous texture, and in which the surface is smooth and glossy, -with a fracture almost vitreous. The upper part of the specimen is -therefore perfect wood coal, and the under part perfect mineral-coal, -in the language of Mr Kirwan; at the same time that the transition from -the one to the other is made by insensible degrees. This specimen, -were it perfectly solitary, is sufficient to prove the identity -of the two species of coal we are now speaking of, and to show, -that the difference between them is accidental, not essential. The -specimen, however, is far from being solitary; the number of similar -<span class="pagenum" id="Page_152">- 152 -</span> -appearances is so great, as hardly to have escaped the observation -of any mineralogist. Mr Kirwan admits, that wood coal is often found -under basaltes;<a id="FNanchor_51" href="#Footnote_51" class="fnanchor">[51]</a> but what is essential to be remarked is, that, in -this instance, we have both the wood coal and the common mineral-coal, -lying under that rock, and the one passing gradually into the other -It appears, indeed, that many of the facts which Mr Kirwan produces, -in treating of what he calls <i>carboniferous</i> soils, are quite -inconsistent with the distinction he would make between wood-coal and -mineral coal.<a id="FNanchor_52" href="#Footnote_52" class="fnanchor">[52]</a></p> - -<div class="footnote"> - -<p><a id="Footnote_51" href="#FNanchor_51" class="label">[51]</a> Geol. Essays, p. 310.</p> - -<p><a id="Footnote_52" href="#FNanchor_52" class="label">[52]</a> <i>Ibid.</i> p. 311.</p> - -</div> - -<p>141. It is, however, true, that there are instances in which the wood -coal, or fossil wood, as it is usually called, forms entire beds, quite -unconnected with the ordinary coal, and stratified in some respects -differently. Such is the Bovey coal in Devonshire, the wood-coal in the -north of Ireland, and perhaps the Surturbrandt of Iceland. With respect -to the Bovey coal, it does by no means answer to one of Mr Kirwan's -remarks, viz. that late observations have ascertained, that no such -parallelism of the beds, as in mineral coal, nor even any distinct -number of strata is found. In the Bovey coal, the number of strata is -very well defined, by beds of clay regularly interposed; but as to the -extent of these -<span class="pagenum" id="Page_153">- 153 -</span> beds, the coal having been worked only at one place, -and by an open pit, without any extensive subterraneous excavation, -nothing is known with certainty.</p> - -<p>In the Bovey coal too, I must observe, though its beds have the -ligneous structure very distinct, the clay interposed between these -beds, which is but little indurated, contains a great deal of coaly -matter, in the form of thin flakes, interspersed through it. So far as -I know, there are no mineral reins nor shifts, nor any bed of indurated -stone, that accompany this coal; so that, though one can not doubt of -its vegetable origin, some doubt may be entertained concerning the -nature of the mineralizing operations, to which it has been subjected -The consideration of these, however, does not belong to the present -argument; and the peculiarities of this semi-mineralized coal, as it -may be called, have nothing to do with the general question, whether -wood coal and mineral coal are the same substance; about which -question, if the gradations are properly considered, I think, no -reasonable doubt can remain.</p> - -<p>142. One of Mr Kirwan's objections to the vegetable origin of coal, -is founded on this fact, that there is, in the museum at Florence, a -cellular sandstone, the cells of which are filled with genuine mineral -coal. "Could this (adds he) -<span class="pagenum" id="Page_154">- 154 -</span> have been originally wood?"<a id="FNanchor_53" href="#Footnote_53" class="fnanchor">[53]</a> The answer -to the interrogatory proposed here as a <i>reductio ad absurdum</i>, -is, that most undoubtedly it may have been wood. Sandstone with charred -wood, that is, with wood coal in it, is not an uncommon phenomenon in -coal countries. I have seen a specimen of this kind from the Hales -Quarry, near Edinburgh, consisting of a piece of charred wood, imbedded -in sandstone; the wood was much altered, but the remains of its fibrous -structure were distinctly visible. This affords a perfect commentary on -the specimen in the Florence cabinet.</p> - -<div class="footnote"> - -<p><a id="Footnote_53" href="#FNanchor_53" class="label">[53]</a> Geol. Essays, p. 321.</p> - -</div> - -<p>143. If then it be granted, as I think it must, that the two kinds of -coal we have been speaking of are of the same origin, it is not very -necessary to enter on a refutation of Mr Kirwan's theory with respect -to either of them. His account of the formation of mineral coal, -however, is so singular, that it cannot be passed over without remark.</p> - -<p>Mr Kirwan supposes, 1mo, That natural carbon was originally contained -in many mountains of the granite and porphyritic order, and also in -siliceous schistus; and might, by disintegration and decomposition, be -separated from the stony particles. 2do, That both petrol and carbon -are often contained in trap, since hornblende, -<span class="pagenum" id="Page_155">- 155 -</span> which has lately been -found to contain carbon, very frequently enters into its composition.</p> - -<p>"My opinion (adds he) is, that coal mines, or strata of coal, as well -as the mountains in which they are found, owe their origin to the -disintegration of primeval mountains, either now totally destroyed, -or whose height and bulk, in consequence of such disintegration, are -considerably lessened; and that these rocks, anciently destroyed, -contained most probably a far larger proportion of carbon and -petrol than those of the same denomination now contain, since their -disintegration took place at so early a period.<a id="FNanchor_54" href="#Footnote_54" class="fnanchor">[54]</a></p> - -<div class="footnote"> - -<p><a id="Footnote_54" href="#FNanchor_54" class="label">[54]</a> Geol. Essays, p. 328, &c.</p> - -</div> - -<p>"By the decomposition of these mountains, the feldspar and hornblende -were converted into clay; the bituminous particles, thus set free, -reunited, and were absorbed, partly by the argil, but chiefly by the -carbonaceous matter, with which they have the greatest affinity. The -carbonic and bituminous particles, thus united, being difficultly -miscible with water, and specifically heavier, sunk through the moist, -pulpy, incoherent argillaceous masses, and formed the lowest stratum," -&c.</p> - -<p>Such is Mr Kirwan's theory of the formation of coal, and nobody I think -will dispute the originality of it.</p> - -<p><span class="pagenum" id="Page_156">- 156 -</span></p> - -<p>144. To enter on a formal refutation of an opinion so loaded with -objections, would be a task as irksome as unnecessary. A few -observations will suffice.</p> - -<p>The notion of the great degradation of mountains, involved in this -hypothesis, is the part of it to which I am least disposed to object. -But I cannot help reminding Mr Kirwan, that the effects of waste are -not supposed less in this, than in Dr Hutton's theory; and that he has -assumed the very principle, of which that theory makes so much use, -though he has reserved to himself, as it should seem, the right of -denying it, when it does not accord with his system. It is indeed worth -while to compare what is said concerning the degradation of mountains, -in the above quotations, and still more fully in the book itself, with -what is advanced concerning their indestructibility, in another passage -of the same volume:<a id="FNanchor_55" href="#Footnote_55" class="fnanchor">[55]</a></p> - -<div class="footnote"> - -<p><a id="Footnote_55" href="#FNanchor_55" class="label">[55]</a> Page 436.</p> - -</div> - -<p>"All mountains are not subject to decay; for instance, scarce any of -those that consist of red granite. The stone of which the Runic rocks -are formed, have withstood decomposition for two thousand years, as -their characters evince," &c.</p> - -<p>"Basaltic pillars, in general, bid defiance to decay," &c. He goes on -to deny every step of the degradation of land, by which it is wasted, -<span class="pagenum" id="Page_157">- 157 -</span> -carried into the sea, and spread out over its bottom, though all these -are necessary <i>postulata</i> in his theory of the formation of coal. -One can be at no loss about estimating the value of a system, in which -such gross inconsistencies make a necessary part.</p> - -<p>145. The quantity of hornblende and siliceous schistus, necessary to -be decomposed, in order to produce the coal strata presently existing, -is enormous, and would lead to an estimate of what is worn away from -the primeval mountains, far exceeding any thing that Dr Hutton has -supposed. It is true, that Mr Kirwan, never at all embarrassed about -preserving a similitude between nature as she is now, and as she was -heretofore, lays it down, that the part of the primeval mountains -which is worn away, contained much more carbon than the part which is -left behind. This, however, is an arbitrary supposition; and since, -in this system, such suppositions are so easily admitted, why may we -not conceive, in the primeval mountains, a more copious source of -carbonic matter than hornblende or siliceous schistus? We have but -to imagine, that the <i>diamond</i> existed among these mountains in -such abundance, as to constitute large rocks. This stone being made up -of pure, or highly concentrated carbon, the adamantine summits of a -single ridge, by their -<span class="pagenum" id="Page_158">- 158 -</span> -decomposition, might afford a carbonic basis, -sufficient for the coal beds of all the surrounding plains.</p> - -<p>146. We may also object to Mr Kirwan, that the siliceous part of -the mountains has not been chemically dissolved; it has been only -abraded and worn away. Mechanical action has reduced the quartz to -gravel and sand, but has not produced on it any chemical change. -The carbon, therefore, could not be let loose. Experiment, indeed, -might be employed, to determine whether the siliceous matter of the -secondary, and of the primary strata contains this substance in the -same proportion.</p> - -<p>Again, a more fatal symptom can hardly be imagined in any theory, than -that, when the circumstances of the phenomena to be explained are <i>a -little</i> changed, the theory is under the necessity of changing <i>a -great deal</i>. Now, this is what happens to Mr Kirwan's theory, in -the attempt made to explain by it the stratum of coal described in the -<i>Annales de Chimie</i>,<a id="FNanchor_56" href="#Footnote_56" class="fnanchor">[56]</a> as cutting a mountain of argillaceous -strata in two, at about three-fourths of its height. This stratum, Mr -Kirwan says, must have been formed by <i>transudation</i> from the -superior part of the mountain,<a id="FNanchor_57" href="#Footnote_57" class="fnanchor">[57]</a> Besides that this is a gratuitous -supposition of a -<span class="pagenum" id="Page_159">- 159 -</span> -thing, without example, it involves in it an -absurdity, which becomes evident the moment the question is asked, -What occupied the place of the coal-bed before the transudation from -the upper part of the mountain? Has the <i>liquid coal</i>, as it -percolated through the upper strata, expelled any substance from the -place it now occupies? or has it been powerful enough to raise up, or -to float, as it were, the upper part of the mountain?</p> - -<div class="footnote"> - -<p><a id="Footnote_56" href="#FNanchor_56" class="label">[56]</a> Tom. xi. p. 272.</p> - -<p><a id="Footnote_57" href="#FNanchor_57" class="label">[57]</a> Geol. Essays, p. 338.</p> - -</div> - -<p>The situation of this bed of coal is not singular, and its formation -is easily explained on Dr Hutton's theory. It is part of a stratum of -coal, which has been deposited, like all others, at the bottom of the -sea; from whence certain causes, of very general operation, have raised -it up, together with the attending strata: these strata have since -been all cut down, and worn away by the operations of the surface; and -the mountain, with the coal stratum in the middle of it, is a part -of them which has been left behind. There is no wonder, that a coal -stratum should be found alternating with others, in a mountain, any -more than in the bowels of the earth, and no more need of a separate -explanation.<a id="FNanchor_58" href="#Footnote_58" class="fnanchor">[58]</a></p> - -<div class="footnote"> - -<p><a id="Footnote_58" href="#FNanchor_58" class="label">[58]</a> This stratum of coal, which is described by -<span class="smcap">Hassenfratz</span>, is remarkable for being in a mountain which rests -immediately on primary schistus and granite.</p> - -</div> - -<p><span class="pagenum" id="Page_160">- 160 -</span></p> - -<p>147. After all, it may be asked, for what purpose is it that so -many incongruous and ill supported hypotheses are thus piled on one -another? is it only to avoid ascribing the carbonic and bituminous -matter of coal to a substance in which we know with certainty that such -matter resides in great abundance, in order to derive it from other -substances, in which a subtle analysis has shown, that it exists in a -very small proportion? Such reasoning is so great a trespass on every -principle of common sense, not to say of sound philosophy, that, to -bestow any time on the refutation of it, is, in some degree, to fall -under the same censure.</p> - - -<hr class="chap x-ebookmaker-drop" /> - -<div class="chapter"> -<h2 class="nobreak" id="Note_iii"><span class="smcap">Note iii. § 7.</span></h2> -</div> - -<p class="caption3nb" id="Primate_mountains"><i>Primitive mountains.</i></p> - - -<p>148. The enumeration of the different kinds of primary schistus, at -§ 7, is not proposed as at all complete. It will be less defective, -however, if we add to it <i>talcose schistus</i>, and <i>lapis -ollaris</i> or <i>potstone</i>.<a id="FNanchor_59" href="#Footnote_59" class="fnanchor">[59]</a></p> - -<div class="footnote"> - -<p><a id="Footnote_59" href="#FNanchor_59" class="label">[59]</a> Kirwan's Mineralogy, vol. i. p. 155.</p> - -</div> - -<p>149. The rocks called here by the name of primary, were first -distinguished, as forming the -<span class="pagenum" id="Page_161">- 161 -</span> basis of all the great chains of -mountains, and as constituting a separate division of the mineral -kingdom, by J. G. <span class="smcap">Lehman</span>, director of the Prussian mines. See -his work, intituled, <i>Essai d'une Histoire Naturelle des Couches de -la Terre</i>.<a id="FNanchor_60" href="#Footnote_60" class="fnanchor">[60]</a> These rocks were regarded by Lehman as parts of the -original nucleus of the globe, which had undergone no alteration, but -remained now such as they were at first created; and, agreeably to -this supposition, he bestowed on them, and on the mountains composed -of them, the name of primitive. He remarks, nevertheless, their -distribution into beds, either perpendicular to the horizon, or highly -inclined, and the super-position of the secondary and horizontal -strata. However mineralogists may now differ in their theories from -Lehman, they must consider this distinction as a great step in the -science of geology, and very material to the right arrangement of the -natural history of the earth.</p> - -<div class="footnote"> - -<p><a id="Footnote_60" href="#FNanchor_60" class="label">[60]</a> Tom. iii. p. 239, &c. The French translation is in 1759, -but the original preface is dated at Berlin, 1756.</p> - -</div> - -<p>150. Several mineralogists have agreed with him in the supposition, -that these rocks are a part of the original structure of the globe, and -prior to all organized matter. Of this number is <span class="smcap">Pallas</span>;<a id="FNanchor_61" href="#Footnote_61" class="fnanchor">[61]</a> -and also <span class="smcap">De Luc</span>, who applies the term -<span class="pagenum" id="Page_162">- 162 -</span> <i>primordial</i> to -the rocks in question, and considers them as neither stratified nor -formed by water.<a id="FNanchor_62" href="#Footnote_62" class="fnanchor">[62]</a> In his subsequent writings, however, he admits -their formation from aqueous deposition, as the Neptunists do in -general, but holds them to be more ancient than organized bodies.</p> - -<div class="footnote"> - -<p><a id="Footnote_61" href="#FNanchor_61" class="label">[61]</a> Observations sur la Formation des Montagnes.</p> - -<p><a id="Footnote_62" href="#FNanchor_62" class="label">[62]</a> Lettres Phys. Sur l'Histoire de la Terre, tom. ii. p. -206.</p> - -</div> - -<p>151. <span class="smcap">Pini</span>, professor of natural history at Milan, has -denied the stratification of primitive mountains, in a memoir on the -mineralogy of St Gothard, and in another on the revolutions of the -globe.<a id="FNanchor_63" href="#Footnote_63" class="fnanchor">[63]</a> His reasonings are opposed by <span class="smcap">Saussure</span>,<a id="FNanchor_64" href="#Footnote_64" class="fnanchor">[64]</a> and are -certainly, in many respects, very open to attack. They proceed on a -comparison between the division of rocks, by what is called the planes -of their stratification, and their division by transverse fissures: -two things, which he thinks so much alike, that they ought not to be -referred to different causes; and, as the one cannot be regarded as -the effect of aqueous deposition, so neither should the other. This -is a very fallacious argument, because it confounds two things that -are essentially different; -<span class="pagenum" id="Page_163">- 163 -</span> and, instead of inquiring about a matter -of fact, inquires about its cause. The truth is, that the dispute -has arisen from not distinguishing the granite from the schistus -mountains, and from involving both under the name of primitive. -M. Pini seems to be in the right, when he holds the granite of St -Gothard to be unstratified; but it is without any good reason, that -he would extend the same conclusion to the schistus of that mountain. -<span class="smcap">Charpentier</span>, and Saussure, in his last two volumes, contend -even for the stratification of granite.<a id="FNanchor_65" href="#Footnote_65" class="fnanchor">[65]</a></p> - -<div class="footnote"> - -<p><a id="Footnote_63" href="#FNanchor_63" class="label">[63]</a> Memoria sulle Rivoluzioni del Globo Terrestre; Memorie -della Societa Italiana, tom. v. p. 222, &c.</p> - -<p><a id="Footnote_64" href="#FNanchor_64" class="label">[64]</a> Voyages aux Alpes, tom. iv. § 1881.</p> - -<p><a id="Footnote_65" href="#FNanchor_65" class="label">[65]</a> See <span class="smcap">Note xv.</span> on Granite.</p> - -</div> - -<p>As the consent, if not universal, is very general for the -stratification of the primary schistus, and the fact itself abundantly -obvious, in almost all the instances I have ever met with, I have not -considered it as necessary to enter here into any argument on this -subject.</p> - - -<hr class="chap x-ebookmaker-drop" /> - -<div class="chapter"> -<h2 class="nobreak" id="Note_iv"><span class="smcap">Note iv. § 8.</span></h2> -</div> - -<p class="caption3nb"><i>Primary strata not primitive.</i></p> - - -<p>152. An account of the facts referred to § 8, may be found in Hutton's -Theory, vol. i. -<span class="pagenum" id="Page_164">- 164 -</span> p. 332, &c. To what is there said, of the shells -contained in the primary limestone of Cumberland, I must add, that -I have since had an opportunity of verifying the conjecture, that -the limestone rock, in which the shells were found, near the head of -<i>Coniston</i> Lake, is part of the same body of strata, where shells -were found, in a quarry between Ambleside and Low-wood. The limestone -of that quarry contains several marine objects; it is in strata -declining about 10° from the perpendicular, toward the S. E., and forms -a belt, stretching across the country from N. E. to S. W.</p> - -<p>In a quarry where the argillaceous schistus, on the south side of this -limestone belt, is worked for pavement, are impressions of what I think -may safely be accounted marine objects; they have the form of shells, -are much indurated, and full of pyrites. They seem to be of the same -kind with the impressions said to be found in a slate quarry, near the -village of Mat in Switzerland.<a id="FNanchor_66" href="#Footnote_66" class="fnanchor">[66]</a></p> - -<div class="footnote"> - -<p><a id="Footnote_66" href="#FNanchor_66" class="label">[66]</a> Hutton's Theory, vol. i. p. 327.</p> - -</div> - -<p>Another spot, affording instances of shells in primary limestone, is -in Devonshire. On the sea shore on the east side of Plymouth Dock, -opposite to Stonehouse, I found a specimen of schistose micaceous -limestone, containing a shell -<span class="pagenum" id="Page_165">- 165 -</span> of the bivalve kind: it was struck -off from the solid rock, and cannot possibly be considered as an -adventitious fossil.</p> - -<p>Now, no rocks can be more decided primary than those about Plymouth. -They consist of calcareous strata, in the form either of marble or -micaceous limestone, alternating with varieties of the same schistus, -which prevails through Cornwall to the west, and extends eastward into -Dartmoor, and on the sea-coast, as far as the Berry-head. These all -intersect the horizontal plane, in a line from east to west nearly; -they are very erect, those at Plymouth being elevated to the north.</p> - -<p>Though, therefore, the remains of marine animals are not frequent among -the primary rocks, they are not excluded from them; and hence the -existence of shell-fish and zoophytes, is clearly proved to be anterior -to the formation even of those parts of the present land which are -justly accounted the most ancient.</p> - -<p>153. The rocks which contain sand or gravel, which are of a granulated -texture, must also be considered as carrying in themselves a testimony -of the most unequivocal kind, of their being derived from the -<i>detritus</i> and waste of former rocks. Now, the fact stated in the -text, concerning sand found in schistus, most justly accounted primary, -might be exemplified by actual -<span class="pagenum" id="Page_166">- 166 -</span> reference to many spots on the earth's -surface. A few such will be sufficient in this place.</p> - -<p>St Gothard is a central point, in one of the greatest tracts of primary -mountains on the face of the earth, yet arenaceous strata are found in -its vicinity. Between Ayrolo and the Hospice of St Gothard, Saussure -found a rock, composed of an arenaceous or granular paste, including -in it hornblende and garnets. He is somewhat unwilling to give the -name <i>gres</i> to this stone, which M. Besson had done; but he -nevertheless describes it as having a granulated structure.<a id="FNanchor_67" href="#Footnote_67" class="fnanchor">[67]</a></p> - -<div class="footnote"> - -<p><a id="Footnote_67" href="#FNanchor_67" class="label">[67]</a> Voyages aux Alpes, tom. iv. § 1822.</p> - -</div> - -<p>Among the most indurated rocks that compose the mountains of this -island, many are arenaceous. Thus, on the western coast of Scotland, -the great body of high and rugged mountains on the shores of Arafaig, -&c. from Ardnamurchan to Glenelg, consists, in a great measure, of a -granitic sandstone, in vertical beds. This stone sometimes occupies -great tracts; at other times it is alternated with the micaceous, or -other varieties of primary schistus; it occurs, likewise, in several of -the islands, and is a fossil which we hardly find described or named -by the writers on mineralogy. Much, also, of -<span class="pagenum" id="Page_167">- 167 -</span> a highly indurated, -but granulated quartz, is found in several places in Scotland, in -beds or strata, alternated with the common schistus of the mountains. -Remarkable instances of this may be seen on the north side of the ferry -of Balachulish, and again on the sea-shore at Cullen. At the latter, -the strata are remarkably regular, alternating with different species -of schistus. At the former, the quartz is so pure, that the stone has -been mistaken for marble.</p> - -<p>These examples are perhaps sufficient; but I must add, that in the -micaceous and talcose schisti themselves, thin layers of sand are -often found, interposed between the layers of mica or talc. I have -a specimen, from the summit of one of the highest of the Grampian -mountains, where the thin plates, of a talcky or asbestine substance, -are separated by layers of a very fine quartzy sand, not much -consolidated.</p> - -<p>The mountain from which it was brought, consists of vertical strata, -much intersected by quartz veins. It is impossible to doubt, in this -instance, that the thin plates of the one substance, and the small -grains of the other, were deposited together at the bottom of the sea, -and that they were alike produced from the degradation of rocks, more -ancient than any which now exist.</p> - -<p><span class="pagenum" id="Page_168">- 168 -</span></p> - -<p>154. In the Neptunian system, as improved by <span class="smcap">Werner</span>, an -attempt is made to take off the force of such instances as are produced -in § 8, 9, and 152, &c. by distinguishing rocks, as to their formation, -into three different orders, the primitive, the intermediate, and the -secondary, or, to speak more properly, into primary, secondary, and -tertiary. The same mineralogist distinguishes, among the materials of -these rocks, between what he terms chemical and mechanical deposits. -By mechanical deposits, are understood sand, gravel, and whatever -bears the mark of fracture and attrition; by chemical deposits, -those which are regularly crystallized, or which have a tendency to -crystallization, and in which the action of mechanical causes cannot -be traced. This distinction is founded in nature, and proceeds on real -and palpable differences; but the application made of it to the three -kinds of strata just enumerated, seems by no means entitled to the same -praise.</p> - -<p>The primitive rocks contain, it is said, none but chemical deposits, -and are entirely composed of them: the intermediate contain a mixture -of both, and also some vestiges of organized bodies: the secondary -consist almost entirely of the mechanical, or of the remains of such -bodies, with little of the chemical. The first of these, then, are held -to contain no mark or vestige -<span class="pagenum" id="Page_169">- 169 -</span> whatsoever of any thing more ancient -than themselves, and are, in the strictest sense, primeval, or formed -of the first materials, deposited by the immense ocean which originally -encompassed the globe.</p> - -<p>After them were formed the intermediate, mostly consisting of chemical -deposits, but containing also some animal remains, and some spoils from -the land, subjected to the various kinds of destruction, which even -then made a part of the order of nature. These rocks, it is alleged, -are chiefly argillaceous, are less indurated than the primary, and not -intersected by veins of quartz.</p> - -<p>The secondary were formed from the remains of the other two, and -contain more mechanical deposits than any other.</p> - -<p>This sketch of what I understand to be Werner's opinion concerning the -different formation of the strata, is chiefly taken from a view of his -system, in the <i>Journal de Physique</i> for 1800.</p> - -<p>155. The main objection to the distinction here made between the -primary and the intermediate strata, is founded on the facts that -have been just stated. The sandstone of St Gothard is from a country -having every character of a primary one in the highest perfection. The -instances I have mentioned from the Highlands of Scotland, are from -mountains, less elevated -<span class="pagenum" id="Page_170">- 170 -</span> -indeed than the Alps, but where the rock is -micaceous, talcose, or siliceous, in planes erect to the horizon, and -intersected by veins' of quartz. The shells from Plymouth are from a -rock, that Werner would, I think, admit to be truly primitive. Those -from the lakes, also, are from the centre of a country, occupied by -porphyry, schorl, hornstone-schistus, and many others, about the order -of which there can be no dispute. It is true, that in this tract -there are argillaceous strata, of the kind that might be accounted -intermediate, were they not interposed among those that are certainly -primary; and this very intermixture shows, how little foundation there -is for the distinction attempted to be made between the formation of -the one and of the other. If there is any principle in mineralogy, -which may be considered as perfectly ascertained, it is, that rocks -similarly stratified, and alternated with one another, are of the same -formation.</p> - -<p>Hence we conclude, that there is <i>no order of strata yet known</i>, -that does not contain proofs of the existence of more ancient strata. -We see nothing, in the strict sense, primitive. It must be understood, -that what is here said has no reference to granite, which I do not -consider as a stratified rock, and in which neither the remains of -organized bodies, nor sand, have I -<span class="pagenum" id="Page_171">- 171 -</span> -believe been ever found; though -some instances will be hereafter mentioned, where granite contains -fragments of other stone, viz. of different kinds of primary schistus.</p> - -<p>To the instances of sand involved in primary schistus, I might have -added many from the rocks of that order on the coast of Berwickshire, -of which mention is so often made in these Illustrations; but I wished -to draw the evidence from those rocks that are most unequivocally -primary, and to which the Wernerian distinction of <i>intermediate</i> -could not possibly be applied.</p> - -<p>If any one assert, as M. De Luc has done, that sand is a chemical -deposit, a certain mode of crystallization which quartz sometimes -assumes, let him draw the line which separates sand from gravel; and -let him explain why quartz, in the form of sand, is not found in -mineral veins, in granite, nor in basaltes, that is, in none of the -situations where the appearances of crystallization are most general -and best ascertained.</p> - - -<hr class="chap x-ebookmaker-drop" /> - -<div class="chapter"> -<h2 class="nobreak" id="Note_v"><span class="smcap">Note v. § 10.</span></h2> -</div> - -<p class="caption3nb"><i>Transportation of the materials of the strata.</i></p> - - -<p>156. The great transportation or <i>travelling</i> of the materials of -the strata, supposed by Dr Hutton, -<span class="pagenum" id="Page_172">- 172 -</span> has been treated as absurd by some -of his opponents, particularly De Luc and Kirwan. These philosophers -seem not to have observed, that their own system, and indeed every -system which derives the secondary strata from the primary, involves -a transportation of materials, hardly less than is supposed in the -Huttonian theory, and a degradation of the primeval mountains, in -many instances much greater. To form some notion of this degradation, -it must be recollected, that the primeval mountains, which furnished -the materials of the secondary strata in the plains, cannot have -stood in the place now occupied by these plains. This is obvious; and -therefore we must necessarily regard the secondary strata as derived -from the primitive mountains which are the nearest to them, and of -which a part still remains. This part is sufficient to define the -base of the original mountains; and the quantity of the secondary -strata which surround them may help us to make some estimate of their -height. Let us take, for instance, the extensive tract of secondary -country about Newcastle, where coal mines have been sunk through a -succession of secondary strata, to the depth of more than a thousand -feet. This secondary country may be considered as comprehending almost -the whole of the counties of Northumberland and Durham, and probably -as -<span class="pagenum" id="Page_173">- 173 -</span> extending very far under the part of the German Ocean which washes -their coasts; and the whole strata composing it must be derived, on the -hypothesis we are now considering, from the Cheviot Hills, on one side, -and from those in the high parts of Westmoreland and Cumberland on the -other, comprehending the Alston-Moor Hills, and the large group of -primary mountains, so well known from the sublime and romantic scenery -of the <i>Lakes</i>. Now, the mountains which stood on this base, had -not only to supply the materials for the tract already mentioned, on -the east, but had also their contingent to furnish to the plains on -the west and north; the Cheviots to Roxburghshire and Berwickshire; -the Northumberland mountains to the coal strata about Whitehaven, and -along the sea coast to Lancashire. On the whole, we shall not exceed -the truth, if we suppose, that the secondary strata, at the feet of -the above mountains, are six or seven times more extensive than the -base of the mountainous tract. If then we take the medium depth of -these secondary strata to be one thousand feet, it is evident, that -the mass of stone which composes them, if it were placed on the same -base with the primitive mountains, would reach to the height of six -thousand feet. This is supposing the mass to preserve the breadth of -its base uniformly to -<span class="pagenum" id="Page_174">- 174 -</span> the summit; but if it be supposed to taper, as -mountains usually do, we must multiply this six thousand by three, in -order to have the height of these primeval mountains, which, therefore, -were originally elevated not less than eighteen thousand feet; in -height, therefore, they once rivalled the Cordilleras, and are now but -poorly represented by the hills of Skidaw and Helvellyn. It were easy -to show, that this estimate is still below the result that strictly -follows from the Neptunian hypothesis; but it is unnecessary to -proceed further, than to prove, that the principle of the degradation -of mountains, is involved in that hypothesis to an excessive and -improbable degree; and that the supporters of it, have either been -guilty of the inconsistency of refusing to Dr Hutton the moderate use -of a principle, which they themselves employ in its utmost extent, or -of not having sufficiently adverted to the consequences of their own -system.</p> - -<p>157. The formation of secondary strata from the degradation of the -contiguous mountains, on close examination, is subject to many -other difficulties of the same kind. Mountains of secondary strata, -and nearly horizontal, are found in this island of the height of -three thousand feet. Such are Ingleborough, Wharnside, and perhaps -some others on the west of Yorkshire. The -<span class="pagenum" id="Page_175">- 175 -</span> whole chain, indeed, -for secondary mountains, is of great elevation. The strata are of -limestone, and of a very coarse-grained sandstone, alternating with it. -No mountains can more clearly point out, that the strata of which they -consist were once continued quite across the vallies which now separate -them; and hence, if the materials of those strata were indeed furnished -from any contiguous primitive mountains, the latter must have been, out -of all proportion, higher than any mountains now in Britain.</p> - -<p>158. Thus, a great degradation of the primitive mountains, and of -course a great travelling of their materials, is proved to make a -necessary part of the Neptunian theory. The extent of this travelling -or transportation may be rendered more evident, if we apply a similar -mode of reasoning to larger portions of the globe. The north-west of -Europe furnishes us an instance of a very extensive tract of secondary -country, comprehending the greater part of Britain, the whole of -Flanders and Holland, part of Germany, the northern provinces of -France, and probably the bed of the German Ocean, at least for a great -extent. Within this circle almost all is secondary, and on the sides -of it all round are placed ridges or groups of primitive mountains, -namely the mountains of Auvergne, -<span class="pagenum" id="Page_176">- 176 -</span> at least in part, and going round by -the east, the Alps, the Vosges, the Hartz, the Highlands and Western -Islands of Scotland, the hilly countries of Cumberland, Wales, and -Cornwall. This zone of primitive mountains, on the supposition of the -Neptunists, must have risen up in the form of islands in the great -ocean, that originally covered the earth, forming a kind of circular -Archipelago, including in its bosom a sea, which was from seven to -five hundred miles in diameter. Over the whole of this extent, the -<i>detritus</i> of the above mountains must have been carried, in order -to form the flat interjacent countries which are now exposed to our -view. Such then, even on their own supposition, is the extent to which -the Neptunists must admit that the materials of the primeval mountains -were transported by the ocean.</p> - -<p>159. This transportation of materials, may not be so great as that -which is involved in Dr Hutton's theory, but is such as should make -the enemies of his system consider, how nearly the principles they -<i>must</i> introduce, agree with those that they <i>would</i> reject. -This is one fact, out of many, which shows, that there is at present -a much nearer agreement between the systems of geology, than between -their authors.</p> - -<p><span class="pagenum" id="Page_177">- 177 -</span></p> - -<p>160. To these facts, demonstrating the great transportation of fossils -in some former conditions of the globe, we may add another, recognised -by all mineralogists. The animal exuviæ contained in limestone and -marble, are often known to belong to seas, extremely remote from the -countries where they are now found. In the chalk-beds of England, in -the limestones of France, a great proportion of the petrifactions -belong to the tropical seas, and appear to have been brought from the -vicinity of the equator. Buffon observes, that of the fossil shells -found in France, it has been disputed, whether the foreign are not -more numerous than the native; and, though he is himself of opinion -that they are not, it is evident that they must bear a considerable -proportion to the whole.<a id="FNanchor_68" href="#Footnote_68" class="fnanchor">[68]</a> In the petrifactions of Monte Bolca, near -Verona, where the impressions of fish are preserved between the laminæ -of a calcareous schistus, one hundred and five different species have -been enumerated, of which thirty-nine are from the Asiatic seas, three -from the African, eighteen from those of South, and eleven from those -of North America.<a id="FNanchor_69" href="#Footnote_69" class="fnanchor">[69]</a> Similar observations have been made on the marine -plants, and the impressions of vegetables, found in rocks, in different -parts of -<span class="pagenum" id="Page_178">- 178 -</span> Europe. At St Chaumont, near Lyons, is found an argillaceous -schistus, covering a bed of coal, every lamina of which is marked with -the impressions of the stem, leaf, or other part of some plant; and it -happens, says M. <span class="smcap">Fontenelle</span>, by an unaccountable destination -of nature, that not one of these plants is a native of France. They are -all ferns of different species, peculiar to the East Indies, or the -warmer climates of America. Here also was found the fruit of a tree, -which grows only on the coasts of Malabar and Coromandel.<a id="FNanchor_70" href="#Footnote_70" class="fnanchor">[70]</a></p> - -<div class="footnote"> - -<p><a id="Footnote_68" href="#FNanchor_68" class="label">[68]</a> Buffon, Théorie de la Terre, art. 8.</p> - -<p><a id="Footnote_69" href="#FNanchor_69" class="label">[69]</a> Saussure, Voyages aux Alpes, tom. iii. § 1535.</p> - -<p><a id="Footnote_70" href="#FNanchor_70" class="label">[70]</a> Mém. De l'Acad. Des Sciences, 1718, p. 3 and 287; and -1721, p. 89, &c.</p> - -</div> - -<p>The same holds of the bodies of amphibious animals which now make -a part of the fossil kingdom. The head and the bones of crocodiles -have been found in the island of Shepey, at the mouth of the Thames; -and the remains of an animal of the same species, but of a variety -now peculiar to the Ganges, have been discovered in the alum rocks -on the coast of Yorkshire.<a id="FNanchor_71" href="#Footnote_71" class="fnanchor">[71]</a> These proofs of the transportation -of -<span class="pagenum" id="Page_179">- 179 -</span> -materials by the sea, have the advantage of involving nothing -hypothetical, and of being equally addressed to the geologists of every -persuasion.</p> - -<div class="footnote"> - -<p><a id="Footnote_71" href="#FNanchor_71" class="label">[71]</a> Phil. Trans. vol. l. p. 688. <span class="smcap">Camper</span> denies that -the remains here mentioned belong to the crocodile, or any amphibious -animal, and refers them to the balænaæ. He passes the same judgment on -those fossil bones from St Peter's Mount, near Maestricht, which have -been supposed to belong to the crocodile; he looks on them as belonging -to whales, though of an unknown species. In this Mount, so famous for -its petrifactions, he finds many specimens of bones, which he thinks -belong to the turtle. Phil. Trans. vol lxxvi. p. 443. The opinion of an -author, so well skilled in comparative anatomy, must be regarded as of -great weight: if it takes from our argument in one part, it adds to it -in another, and the acquisition of the turtle makes up abundantly for -the loss of the crocodile.</p> - -</div> - -<p>On this subject I cannot help observing, that the accurate comparison -of the animal exuviæ of the mineral kingdom, with their living -archetypes, is not merely a curious inquiry, but is one that may lead -to important consequences, concerning the nature and direction of the -forces which have changed, and are continually changing, the surface of -the earth.</p> - -<p>161. These remarks I have thought it proper to add to the proofs of the -composition of the present from former strata, in order to show, that -the great transportation of materials involved in that supposition, is -not only conformable to the hypothesis of the Neptunists concerning -the secondary strata, but is also proved by the most direct evidence, -independently of all hypothesis. All this reasoning regards the ancient -state of -<span class="pagenum" id="Page_180">- 180 -</span> -the globe. Whether such a travelling of stony bodies makes -a part of the system now actually carrying on, will be considered in -another place.<a id="FNanchor_72" href="#Footnote_72" class="fnanchor">[72]</a></p> - -<div class="footnote"> - -<p><a id="Footnote_72" href="#FNanchor_72" class="label">[72]</a> See <span class="smcap">Note xix</span>.</p> - -</div> - - - -<hr class="chap x-ebookmaker-drop" /> - -<div class="chapter"> -<h2 class="nobreak" id="Note_vi"><span class="smcap">Note vi. § 13.</span></h2> -</div> - -<p class="caption3nb"><i>Mr Kirwan's notion of precipitation.</i></p> - - -<p>162. The Neptunist who has provided the means of dissolving the -materials of the strata, has only performed half his work, and must -find it a task of equal difficulty to force this powerful menstruum -to part with its solution. Mr Kirwan, aware in some degree of this -difficulty, has attempted to obviate it in a very singular way. First, -he ascribes the solution of all substances in water, or in what he -calls the chaotic fluid, to their being finely pulverised, or created -in a state of the most minute division. Next, as to the deposition, the -solvent being, as he acknowledges, very insufficient in quantity, the -precipitation took place, (he says,) on that account the more rapidly.</p> - -<p>If he means by this to say, that a precipitation without solution -would take place the sooner the more inadequate the menstruum was to -dissolve the whole, the proposition may be true; -<span class="pagenum" id="Page_181">- 181 -</span> but will be of no -use to explain the crystallization of minerals, (the very object he -has in view,) because to crystallization, it is not a bare subsidence -of particles suspended in a fluid, but it is a passage from chemical -solution to non-solution, or insolubility, that is required.</p> - -<p>If, on the other hand, he means to say, that the solution actually took -place more quickly, and was more immediately followed by precipitation, -because the quantity of the menstruum was insufficient, this is to -assert, that the weaker the cause, the more instantaneous will be its -effect.</p> - -<p>Of two propositions the one of which is nugatory, and the other absurd, -it is not material to inquire which the author had in view.</p> - - -<hr class="chap x-ebookmaker-drop" /> - -<div class="chapter"> -<h2 class="nobreak" id="Note_vii"><span class="smcap">Note vii. § 16.</span></h2> -</div> - -<p class="caption3nb"><i>Compression in the mineral regions.</i></p> - - -<p>163. It is worthy of remark, that the effects ascribed to compression -in the Huttonian Theory, very much resemble those which Sir <span class="smcap">Isaac -Newton</span> supposes to be produced in the sun and the fixed stars by -that same cause. "Are not," says he, "the sun and fixed stars great -earths, vehemently hot, whose heat is conserved by the greatness of -the bodies, and the mutual action -<span class="pagenum" id="Page_182">- 182 -</span> and reaction between them, and the -light which they emit; and <i>whose parts are kept from fuming away, -not only by their fixity, but also by the vast weight and density of -the atmospheres incumbent upon them, and very strongly compressing -them</i>."<a id="FNanchor_73" href="#Footnote_73" class="fnanchor">[73]</a></p> - -<div class="footnote"> - -<p><a id="Footnote_73" href="#FNanchor_73" class="label">[73]</a> Newton's Optics, Query 11.</p> - -</div> - -<p>164. The fact of water boiling at a lower temperature under a less -compression, is sufficient to justify the supposition, that bodies may -be made by pressure to endure extreme heat, without the dissipation -of their parts, that is, without evaporation or combustion. A further -<i>postulatum</i> is introduced in Dr Hutton's theory, namely, that -compound bodies, such as carbonate of lime, when the compression -prevents their separation, may admit of fusion, notwithstanding that -the fixed part may be infusible when separated from the volatile. This -assumption is supported by the analogical fact of the fusion of the -carbonate of barytes, as mentioned in the text.</p> - -<p>165. In a region where the action of heat was accompanied with such -compression as is here supposed, there could be no fire, properly so -called, and no combustion; this is admitted by Dr Hutton, and it is -therefore a fallacious argument which is brought against his theory, -from the impossibility of fire being maintained -<span class="pagenum" id="Page_183">- 183 -</span> in the bowels of the -earth. This impossibility is precisely what he supposes; and yet Mr -Kirwan's arguments are directed, not against the existence of heat in -the interior of the earth, but against the existence of burning and -inflammation.</p> - -<p>After taking notice,<a id="FNanchor_74" href="#Footnote_74" class="fnanchor">[74]</a> that Saussure had succeeded, though with -extreme difficulty, in melting a particle of limestone, so small as -to be visible only with a microscope, "what (adds he) must have been -the heat necessary to melt whole mountains of this matter? Judging by -all that we at present know of heat, such a high degree could only -be produced by the purest air, acting on an enormous quantity of -combustible matter. Now, <span class="smcap">Ehrman</span> observed, that the combustion -of two hundred and eighty cubic inches of air, acting on charcoal, was -not able to effect the fusion of one grain of Carrara marble; from -whence it is apparent, that all the air in the atmosphere, nor in ten -atmospheres, would not melt a single mountain of this substance, of -any extent, even if there were a sufficient quantity of inflammable -matter for it to act upon. Judging also of subterraneous heat by what -we know of that of volcanoes, no such heat exists: the highest they -in general produce, is that requisite for the fusion of the volcanic -glass called -<span class="pagenum" id="Page_184">- 184 -</span> -obsidian, which Saussure found not to exceed 115° of -Wedgewood; but basaltine, which requires 140° of Wedgewood, is never -melted in the lavas of Ætna. How little capable, then, would volcanic -heat be to effect the fusion of Carrara marble, which, according to -the same excellent author, would require a heat of upwards of 6300° -of Wedgewood, if this pyrometer could extend so far? And in what -circumstances does Dr Hutton suppose this astonishing heat to have -existed, and even still to exist, under the ocean, in the bowels of -the earth, where neither a sufficient quantity of pure air, nor of -combustible matter, capable of such mighty effects, can, with any -appearance of probability, be supposed to exist: and, without these, -such degrees of heat cannot even be imagined, without flying into the -region of chimeras."</p> - -<div class="footnote"> - -<p><a id="Footnote_74" href="#FNanchor_74" class="label">[74]</a> Geol. Essays, p. 453.</p> - -</div> - -<p>166. Now, this reasoning is not applicable to Dr Hutton's hypothesis -of subterraneous heat, because it is grounded on experiments, where -that very separation of the volatile and fixed parts takes place, which -is excluded in that hypothesis. When limestone or marble is exposed -to such heat as is here mentioned, or even to heat of a degree vastly -inferior, the carbonic gas is expelled, and the body is reduced to pure -lime; from the refractory nature of which, as we learn from the fact -relative -<span class="pagenum" id="Page_185">- 185 -</span> -to barytes, mentioned above, no conclusion can be drawn as to -the infusibility of the same substance, when combined with the carbonic -gas. The Carrara marble may require a heat of 6300° of Wedgewood, to -melt it in the open air, where the carbonic gas escapes from it; but -under such a pressure as would retain this gas, it cannot be inferred, -that it might not melt with the heat of a glass-house furnace. In like -manner, it may be true, that two hundred and eighty cubic inches of -air, acting on charcoal, cannot effect the fusion of one grain of this -marble, after its fixed air is driven off from it; but we cannot from -thence draw any inference, applicable to a case where the carbonic gas -is retained, and where the action of heat is independent of atmospheric -air.</p> - -<p>Nothing, therefore, can be more inconclusive than this reasoning, -as it proceeds on the supposition, that Dr Hutton's system admits -propositions, which in fact it expressly denies.</p> - -<p>167. Of the production and maintenance of heat, in circumstances -so different from those of ordinary experience, we can hardly be -expected to give any explanation; but we are not entitled, merely -on that account, to doubt of the existence of such heat. Mr Kirwan -thinks otherwise: "Judging," he says, "from all we at present know of -heat, such a high degree of it, (as will melt limestone,) could only -be produced by the purest -<span class="pagenum" id="Page_186">- 186 -</span> -air, acting on an enormous quantity of -combustible matter. Without these, such degrees of heat cannot even be -imagined, without flying into the region of chimeras."<a id="FNanchor_75" href="#Footnote_75" class="fnanchor">[75]</a></p> - -<div class="footnote"> - -<p><a id="Footnote_75" href="#FNanchor_75" class="label">[75]</a> Geol. Essays, p. 454.</p> - -</div> - -<p>Now, in the first place, the high degree of temperature which is -here understood, is probably not necessary to the purposes of -mineralization, as has just been shown; and, in the second place, it is -not <span class="smcap">fire</span>, in the usual sense of the word, but <span class="smcap">heat</span>, -which is required for that purpose; and there is nothing chimerical in -supposing, that nature has the means of producing heat, even in a very -great degree, without the assistance of fuel or of vital air. Friction -is a source of heat, unlimited, for what we know, in its extent, and -so perhaps are other operations, both chemical and mechanical; nor are -either combustible substances, or vital air, concerned in the heat -thus produced. So also the heat of the sun's rays in the focus of a -burning glass, the most intense that is known, is independent of the -substances just mentioned; and, though that heat certainly could not -calcine a metal, nor even burn a piece of wood, without oxygenous gas, -it would doubtless produce as high a temperature in the absence as in -the presence of that gas.</p> - -<p><span class="pagenum" id="Page_187">- 187 -</span></p> - -<p>It is true, that it is not by the solar rays that subterraneous heat -is produced; but still, from this instance, we see, that there is no -incongruity in supposing the production of heat to be independent of -combustible bodies, and of vital air. We are indeed, in all cases, -strangers to the origin of heat; philosophers dispute, at this moment, -concerning the source of that which is produced by burning; and much -more are they at a loss to determine, what upholds the light and heat -of the great luminary, which animates all nature by its influence. If -we would form any opinion on this object, we shall do well to attend -to the suggestions of that great philosopher, who was hardly less from -others by his doubts and conjectures, than by his most rigorous and -profound investigations. "May not great, dense, and fixed bodies, when -heated beyond a certain degree, emit light so copiously, as, by the -emission and reaction of its light, and the reflections and refractions -of its rays within its pores, to grow still hotter, till it comes to -a certain period of heat, such as is that of the sun? And, are not -the sun and fixed stars great earths, vehemently hot, whose heat is -conserved by the greatness of the bodies, and the mutual action and -reaction between them and the light which they emit?"<a id="FNanchor_76" href="#Footnote_76" class="fnanchor">[76]</a></p> - -<div class="footnote"> - -<p><a id="Footnote_76" href="#FNanchor_76" class="label">[76]</a> Newton's Optics, <i>ubi supra</i>.</p> - -</div> - -<p><span class="pagenum" id="Page_188">- 188 -</span></p> - -<p>168. Some recent experiments, seem to make the suggestions in this -query applicable to an opaque body like the earth, as well as to -luminous bodies, such as the sun and fixed stars. The radiation -of heat, where there is no light, was first rendered probable by -the experiments of M. <span class="smcap">Pictet</span> of Geneva;<a id="FNanchor_77" href="#Footnote_77" class="fnanchor">[77]</a> and the only -objections to which the conclusions from those experiments seemed -liable, are removed by the late very important discoveries of Dr -<span class="smcap">Herschel</span>.<a id="FNanchor_78" href="#Footnote_78" class="fnanchor">[78]</a> From these it appears, that heat is capable of -refraction and reflection, as well as light, so that it is not absurd -to suppose, that <i>the heat of great, dense, and faced bodies, may be -conserved by the greatness of the bodies, and the mutual action and -reaction between them and the heat which they emit</i>.</p> - -<div class="footnote"> - -<p><a id="Footnote_77" href="#FNanchor_77" class="label">[77]</a> Essai sur le Feu.</p> - -<p><a id="Footnote_78" href="#FNanchor_78" class="label">[78]</a> Phil. Trans. 1800, p. 84.</p> - -</div> - -<p>The existence of subterraneous heat is still further rendered probable -from the researches of <span class="smcap">Mairan</span>, which tend to show, that there -is another source of terrestrial heat besides the influence of the -solar rays.<a id="FNanchor_79" href="#Footnote_79" class="fnanchor">[79]</a></p> - -<div class="footnote"> - -<p><a id="Footnote_79" href="#FNanchor_79" class="label">[79]</a> Mém. de l'Acad. des Sciences, 1765, p. 143.</p> - -</div> - -<p>Whatever be the truth with regard to these conjectures, it is certain, -that the first and original source of heat is independent of burning. -Burning is an <i>effect</i> of the concentration of heat; -<span class="pagenum" id="Page_189">- 189 -</span> -and though, -by a certain reaction, it has the power of continuing and augmenting -that heat, it never can be regarded as its primary and material cause. -When, therefore, we suppose a source of heat, independent of fire and -of burning, we suppose what certainly exists in nature, though we -are not informed of the manner of its existence, nor of its place, -otherwise than from considering the phenomena of the mineral kingdom.</p> - -<p>169. Lastly, we are not entitled, according to any rules of -philosophical investigation, to reject a principle, to which we are -fairly led by an induction from facts, merely because we cannot give -a satisfactory explanation of it. It would be a very unsound view of -physical science, which would induce one to deny the principle of -gravitation, though he cannot explain it, or even though the admission -of it reduces him to great metaphysical difficulties. If indeed a -downright absurdity, or inconsistency with known and established facts, -be involved in any principle, it ought not to be admitted, however it -may seem calculated to explain other appearances. If, for instance, Dr -Hutton held, that combustion was carried on in a region where there -was no vital air, we should have said, that he admitted an absurdity, -and that a theory founded on such <i>postulata</i> was worse than -chimerical. But, if the only thing -<span class="pagenum" id="Page_190">- 190 -</span> -imputable to him is, that, being -led by induction to admit the fusion of mineral substances in the -bowels of the earth, he has assumed the existence of such heat as was -sufficient for this fusion, though he is unable to assign the cause -of it, I believe it will be found, that his system only shares in an -imperfection, which is common to all physical theories, and which the -utmost improvement of science will never completely remove.</p> - -<p>170. Thus, then, we are led, it must be allowed, into the <i>region of -hypothesis</i> and conjecture, but by no means into that of chimeras. -Indeed, the reproach of flying into the latter region, may be said to -come but ill from one, who has trode so often the crude consistence of -the chaos, and who delights to dwell beyond the boundaries of nature. -By sojourning there long, it is not impossible that the eye may become -so accustomed to fantastic forms, that the figures and proportions of -nature shall appear to it deformed and monstrous.</p> - - -<hr class="chap x-ebookmaker-drop" /> - -<div class="chapter"> -<h2 class="nobreak" id="Note_viii"><span class="smcap">Note viii. § 24.</span></h2> -</div> - -<p class="caption3nb"><i>Sparry structure of calcareous petrifactions.</i></p> - - -<p>171. When the shells and corals in limestone are quoted by -mineralogists, it is not always -<span class="pagenum" id="Page_191">- 191 -</span> considered in what state they are -found. In general, they have a sparry structure, very different -from that of the original shell or coral, of which, however, they -retain the figure with wonderful exactness, though probably sometimes -altered in size. Though sparry, they are often foliated, and preserve -their animal, in conjunction with their mineral, texture. Now, this -crystallization is a mark of some operation, quite different from any -that can be ascribed to the water in which these bodies had their -origin, and by which they were brought into their place. They were -impervious to water; and it cannot be said that their sparry structure -has been derived from the percolation of that fluid, carrying new -calcareous matter into their pores. We can account for the change -produced in them, I think, only by supposing them to have been softened -by heat, so as to permit their parts to arrange selves anew, and to -assume the characteristic organization of mineral substances.</p> - -<p>All shells have not the change effected on them that is here referred -to; those in chalk, for instance, retain very much their original form -in all respects. This is what we might expect from the very different -degree of intensity, with which the mineralizing cause has acted on -chalk, and on limestone or marble. In general, it is in the hardest -and most consolidated -<span class="pagenum" id="Page_192">- 192 -</span> -limestone, that the marine objects are most -completely changed into spar.</p> - -<p>It would be exceedingly interesting to examine, whether any of the -phosphoric acid remains united to shells of either of these kinds. We -might most readily expect it to be united, in a certain degree, to the -shells that are least mineralized.</p> - -<p>This experiment would enable us also to appreciate the force of Mr -Kirwan's argument against the finer marbles, such as the Carrara, -containing shells.<a id="FNanchor_80" href="#Footnote_80" class="fnanchor">[80]</a> This argument proceeds on an experiment, -mentioned in the <i>Turin Memoirs</i> for 1789, from which it appears, -that no phosphoric acid is found in pure limestone; and its absence, -Mr Kirwan says, cannot be attributed to fusion, as phosphoric acid is -indestructible by heat.</p> - -<div class="footnote"> - -<p><a id="Footnote_80" href="#FNanchor_80" class="label">[80]</a> Geol. Essays, p. 458.</p> - -</div> - -<p>He calls this a demonstration; but, in order to entitle it to that -name, it will be necessary, first, to prove, that phosphoric acid -exists in those limestones which evidently consist of shells in a -mineralized state. If these are found without phosphoric acid, it is -evident that the preceding argument fails entirely. If they are found -to contain that acid, it will then no doubt afford a probability, -though not a demonstration, that -<span class="pagenum" id="Page_193">- 193 -</span> -Carrara marble does not directly -originate from shells.</p> - -<p>That nature has some process, by which the above acid is separated -from the earth of bones, and probably also from the earth of shells, -is evident from the state in which the bones are found in the caves of -Bayreuth. Those that are the most recent, and least petrified, contain -most of the phosphoric acid. Where the petrifaction has proceeded far, -that acid is not found.</p> - -<p>172. Among many of the strata, such a fluidity has prevailed, as -to enable some of the substances included in them to crystallize. -Calcareous spar and siliceous crystals are often found in stratified -rocks, forming veins of secretion, or lining close cavities, included -on all sides by the uncrystallized rock. In the instances of gneiss, -and many species of marble, almost the whole matter of the stratum is -crystallized. This union of a stratified and crystallized structure -in the same substance, has a great affinity to that union of the -crystallized with the organic structure of shells and corals which has -just been mentioned; and both are doubtless to be referred to the same -cause.</p> - - -<hr class="chap x-ebookmaker-drop" /> - -<div class="chapter"> -<p><span class="pagenum" id="Page_194">- 194 -</span></p> - -<h2 class="nobreak" id="Note_ix"><span class="smcap">Note ix. § 81.</span></h2> -</div> - -<p class="caption3nb"><i>Petroleum, &c.</i></p> - - -<p>173. According to the theory of coal laid down above, its two chief -materials, charcoal and bitumen, being furnished by the vegetable and -animal kingdoms, both of the land and of the sea, have formed with one -another a new combination, by the action of subterraneous heat; but -have also, in some cases, been separated by that same action, where -the degree of compression necessary for their union, happened to be -wanting. The carbonic part, when thus separated from the bituminous, -forms an infusible coal, which burns without flame: the bituminous -part, when separated from the carbonic, is found in the various states -of naphtha, petroleum, asphaltes, and jet.</p> - -<p>The great resemblance of infusible or blind coal, to the residuum -obtained by the distillation of bituminous coal; and again, the -coincidence of the bitumens just named, with the volatile part, or -the matter brought over by such distillation, are strong arguments -in favour of this theory. The other facts in the natural history of -coal, serve to confirm the same conclusion; but it must be confessed, -that what -<span class="pagenum" id="Page_195">- 195 -</span> -we know of the pure bitumens, except the circumstance -just mentioned, is of a more ambiguous nature, and may be reconciled -with different theories. The drops of petroleum contained within the -cavities of the limestone, mentioned at § 31, are however strong facts -in confirmation of Dr Hutton's opinions, and they are furnished by the -substances purely bituminous. A careful examination would probably make -us acquainted with others of the same kind, for limestone is very often -the matrix in which petroleum and asphaltes are contained. The greatest -mine of asphaltes in Europe, that in the <i>Val de Travers</i> in the -territory of Neufchâtel, is in limestone, from which, though it in some -places exudes, it is in general extracted by the application of heat. -The strata for several leagues are impregnated with bitumen; and, if -examined with attention, would probably afford specimens similar to -those which have just been mentioned.</p> - -<p>174. It is a general remark, that, where petroleum is found, on -digging deeper, they come to asphaltes; and, at a depth still greater, -they discover coal. This probably does not hold invariably; but -it is certain, that most of the fountains of petroleum are in the -neighbourhood of coal strata. Petroleum and asphaltes are found in -great abundance in Alsace, in a bed of sand, between two beds of clay -or argillaceous -<span class="pagenum" id="Page_196">- 196 -</span> -schistus, and the same country also affords coal.<a id="FNanchor_81" href="#Footnote_81" class="fnanchor">[81]</a> -This is true likewise of the fossil pitch of Coal-Brookdale; and of the -petroleum found in St Catharine's Well, near Edinburgh. Auvergne<a id="FNanchor_82" href="#Footnote_82" class="fnanchor">[82]</a> -contains abundance of fossil pitch, which exudes, in the warm season, -from a rock impregnated with it through its whole mass. There are also -coal strata in the same country, not far distant.</p> - -<div class="footnote"> - -<p><a id="Footnote_81" href="#FNanchor_81" class="label">[81]</a> Encyclopédia, mot, <i>Asphalte</i>.</p> - -<p><a id="Footnote_82" href="#FNanchor_82" class="label">[82]</a> Voyage en Auvergne, par Lagrand, tom. i. p. 351.</p> - -</div> - -<p>A very satisfactory observation relating to this subject, has lately -been communicated from a country, with whose natural history we were -till of late entirely unacquainted. In the Burmha empire, petroleum is -dug up in an argillaceous earth, from the depth of seventy cubits. This -argillaceous earth, or schistus, lies under a bed of freestone; and -under all, about one hundred and thirty cubits from the surface, is a -bed of coal.<a id="FNanchor_83" href="#Footnote_83" class="fnanchor">[83]</a></p> - -<div class="footnote"> - -<p><a id="Footnote_83" href="#FNanchor_83" class="label">[83]</a> Asiatic Researches, vol. vi, art. 6. p. 130.</p> - -</div> - -<p>175. In the petroleum lake of the Island of Trinidad, described <i>Phil -Trans.</i> 1789, the petroleum evidently exudes from the rock, and -is collected in a variety of springs in the bottom, after which it -hardens, and acquires the consistency -<span class="pagenum" id="Page_197">- 197 -</span> of pitch. The manner, therefore, -in which petroleum exists in the strata, is very consistent with the -idea of its having been introduced in the form of a hot vapour.</p> - -<p>Even amber appears to have some relation to coal. It is found in the -unconsolidated earth in Prussia and Pomerania; but I am not sure -whether this earth is <i>travelled</i> or not. In the same earth where -the amber is found, there is often a mixture of coaly matter, which -burns in the fire; it is apparently fibrous, and has been considered as -a kind of fossil-wood.<a id="FNanchor_84" href="#Footnote_84" class="fnanchor">[84]</a></p> - -<div class="footnote"> - -<p><a id="Footnote_84" href="#FNanchor_84" class="label">[84]</a> Buffon, Hist. Nat. des Mineraux, tom. ii. p. 5.</p> - -</div> - -<p>These circumstances make out a connection between the purer bitumens -and ordinary coal; but do not, it must be acknowledged, establish any -thing with respect to the more immediate relation, supposed in this -theory to exist between them and blind coal. It is probable, indeed, -that, to discover any facts of that kind, the natural history of both -substances must be more carefully examined; the natural history of -blind coal, in particular, has hitherto been but little attended to.</p> - -<p>176. A fact is mentioned by Mr Kirwan, which must not be regarded as -less valuable for being adverse to this theory. It is, that neither -petroleum, nor any fossil bitumen, is found in the vicinity of the -Kilkenny coal, as might be expected, -<span class="pagenum" id="Page_198">- 198 -</span> -if that coal was deprived of -its bituminous part by subterraneous distillation.<a id="FNanchor_85" href="#Footnote_85" class="fnanchor">[85]</a> This, however, -admits of explanation. Though a general connection, on the above -hypothesis, might be expected between bitumens and infusible coal, we -cannot look for it in every instance. The heat which drove off the -bitumen from one part of a stratum of coal, may only have forced it to -a colder part of the same stratum; and thus, in separating it from one -portion of carbonic matter, may have united it to another. Blind coal -may therefore be found where no bitumen has been actually extricated. -In like manner, bitumen may have been separated, where the coal was -not reduced to the state of coke, as a part of the bitumen only may -have been driven off, and enough left to prevent the coal from becoming -absolutely infusible.</p> - -<div class="footnote"> - -<p><a id="Footnote_85" href="#FNanchor_85" class="label">[85]</a> Geol. Essays, p. 473.</p> - -</div> - -<p>It should be considered too, if the bitumen was really separated, and -forced, in the state of vapour, into some argillaceous or limestone -stratum, that this stratum may have been wasted and worn away long ago, -so that the bitumen it contained may have entirely disappeared. It does -not therefore necessarily follow, that, wherever we find blind coal, -there also we should discover some of the purer bitumens.</p> - - -<hr class="chap x-ebookmaker-drop" /> - -<div class="chapter"> -<p><span class="pagenum" id="Page_199">- 199 -</span></p> - -<h2 class="nobreak" id="Note_x"><span class="smcap">Note x. § 37.</span></h2> -</div> - -<p class="caption3nb"><i>The height above the level of the sea at which the marks of aqueous -deposition are now found.</i></p> - - -<p>177. We have two methods of determining the <i>minimum</i> of the -change which has happened to the relative level of the sea and land; -or for fixing a limit, which the true quantity of that change must -necessarily exceed. The one is, by observing to what height the regular -stratification of mountains reaches above the present level of the sea; -the other is, by determining the greatest height above that level, -at which the remains of marine animals are now found. Of these two -criteria, the first seems preferable, as the fact on which it proceeds -is most general, and least subject to be affected by accidental causes, -or such as have operated since the formation of the rocks. The results -of both, however, if we are careful to select the extreme cases, agree -more nearly than could have been expected.</p> - -<p>178. The mountain Rosa, in the Alps, is entirely of stratified rocks, -very regularly disposed, -<span class="pagenum" id="Page_200">- 200 -</span> -and nearly horizontal.<a id="FNanchor_86" href="#Footnote_86" class="fnanchor">[86]</a> The highest summit -of this mountain is, by Saussure's measurement, 2430 toises, or 14739 -English feet, above the level of the sea, or lower than the top of -Mont Blanc only by 20 toises, or 128 feet.<a id="FNanchor_87" href="#Footnote_87" class="fnanchor">[87]</a> This is, I believe, the -highest point on the earth's surface, at which the marks of regular -stratification are certainly known to exist; for though, by the account -of the same excellent mineralogist, Mont Blanc itself is stratified, -yet, as the rock is granite, the stratification vertical, and somewhat -ambiguous, it is much less proper than Monte Rosa for ascertaining the -limit in question.</p> - -<div class="footnote"> - -<p><a id="Footnote_86" href="#FNanchor_86" class="label">[86]</a> Voyages aux Alpes, tom. iv. § 2138.</p> - -<p><a id="Footnote_87" href="#FNanchor_87" class="label">[87]</a> <i>Ibid.</i> § 2135.</p> - -</div> - -<p>179. Again, in the new continent, we have an instance of shells -contained in a rock, not much lower than the summit of Monte Rosa. -This is one described by Don <span class="smcap">Ulloa</span>, near the quicksilver mine -of Guanca-Velica, in Peru. The height at which a specimen of these -shells, given by Ulloa to M. Le <span class="smcap">Gentil</span>, was found, was 2222 -1/3 toises, or 14190 feet English, above the level of the seas.<a id="FNanchor_88" href="#Footnote_88" class="fnanchor">[88]</a> -This height agrees with the preceding, within 549 feet, a quantity -comparatively small.</p> - -<div class="footnote"> - -<p><a id="Footnote_88" href="#FNanchor_88" class="label">[88]</a> See Hist. Acad. des Sciences, 1770. Phys. Générale, No. -7.</p> - -</div> - -<p><span class="pagenum" id="Page_201">- 201 -</span></p> - -<p>180. The last of the facts just mentioned is curiously commented on by -Mr Kirwan. As he has proved, he says, that the mountains higher than -8500 feet were all formed before the creation of fish, it follows, -that the shells found at Guanca-Velica, must have been carried there -by the deluge.<a id="FNanchor_89" href="#Footnote_89" class="fnanchor">[89]</a> Now, without objecting to the proof here referred -to, (though it seems very open to objection,) it is sufficient to -remark, that, if the shells at Guanca-Velica were carried there by the -deluge, or any other cause that operated after the formation of the -rock of which the mountain consists, they can make no part of that -rock, but must lie, like other adventitious fossils, loose and detached -on the surface, or at most externally agglutinated to the stone. This, -however, is certainly not the fact; for, in the account just quoted, -we read, that Don Ulloa told M. le Gentil, "qu'il avoit détaché ces -coquilles d'un banc fort épais." This seems plainly to indicate, -that the shells were included in a bed of rock; But, granting that -the expression is a little ambiguous, on turning to the <i>Mémoires -Philosophiques</i> of the same author, the difficulty is completely -removed, and it is made evident, that these shells are in fact -integrant parts of the rock. "On voit dans ces montagnes-là, (about -<span class="pagenum" id="Page_202">- 202 -</span> -Guanca-Velica, and particularly at that in which is the quicksilver -mine,) des coquilles entières, petrifiées et enfermées au milieu de la -roche, que les eaux de pluie mettent à decouvert. Ces coquilles font -corps avec la pierre; mais malgré cela, on remarque que la partie qui -fut coquille, se distingue par la couleur, la structure, la qualité de -la matière de tout autre corps pierreux qui l'enferme, et du massif qui -s'est fixé entre les deux ecailles,"<a id="FNanchor_90" href="#Footnote_90" class="fnanchor">[90]</a> &c. He goes on to say, that -one can distinguish marks of these shells having been worn, before they -were included in the stone.</p> - -<div class="footnote"> - -<p><a id="Footnote_89" href="#FNanchor_89" class="label">[89]</a> Geol. Essays, p. 54.</p> - -<p><a id="Footnote_90" href="#FNanchor_90" class="label">[90]</a> Mém. Philosophiques de Don Ulloa, Discours xvi. vol. i. -p. 364.</p> - -</div> - -<p>181. Thus it appears, that whatever proof any fossil shell affords, -that the rock in which it is found was formed under the sea, the -same is afforded by the fossil shells of Guanca-Velica; and we are, -therefore, perfectly entitled to conclude, that the relative level of -the sea and land has changed, since the formation of the latter, by -more than 14000 feet. The height assumed in § 37 is therefore much -under the truth; and the water, for which the Neptunists must provide -room in subterraneous caverns, might very well have been stated at -<span class="pagenum" id="Page_203">- 203 -</span> -more than a five-hundredth part of the whole mass of the earth.</p> - -<p>Thus also the argument by which the Neptunists would connect the -creation of fish with the beginning of the secondary mountains, falls -entirely to the ground. Indeed, it is strange that Mr Kirwan should -have supposed it possible, that the shells in question were loose -and unconnected with the rock, and had continued so, ever since the -deluge, in such elevated ground, where the torrents wear and cut -down the mountains with unexampled violence, and have hollowed out -<i>Quebradas</i> so much deeper and more abrupt than the glens or -vallies among other mountains. He had not, I believe, seen the passage -I have quoted from Ulloa; but the circumstances did not warrant the -shells in question to be regarded as extraneous and adventitious -fossils. A geologist should have known better than to suppose this -possible. When we see <span class="smcap">Voltaire</span> ascribing to accidental causes -the transportation of those shells which he had been told were often -found among the Alps, we can excuse in a Poet and a Wit, that ignorance -of the facts in mineralogy, which concealed from him the extreme -absurdity of his assertion; but when a Chemist or Mineralogist talks -and reasons in the same manner, we cannot consider him as entitled to -the same indulgence.</p> - - -<hr class="chap x-ebookmaker-drop" /> - -<div class="chapter"> -<p><span class="pagenum" id="Page_204">- 204 -</span></p> - -<h2 class="nobreak" id="Note_xi"><span class="smcap">Note xi. § 42.</span></h2> -</div> - -<p class="caption3nb"><i>Fracture and dislocation of the strata.</i></p> - - -<p>182. The greatest part of the facts relative to the fracture and -dislocation of the strata, belongs to the history of veins. The -instances of slips, where no new mineral substance is introduced -between the separated rocks, are what properly belong to this place. -The frequency of these, and their great extent, are well known wherever -mines have been wrought. In some of them no opening is left, but the -slipped strata remain contiguous; in other cases, there is introduced -an unconsolidated earth, often a clay, which may be supposed to have -come from above, arid very probably to have been carried down by the -water. In some such cases, however, there are not wanting appearances, -which show the matter in the slip to have been forced up from below, -as we find it to contain substances which could not have come from the -surface.<a id="FNanchor_91" href="#Footnote_91" class="fnanchor">[91]</a></p> - -<div class="footnote"> - -<p><a id="Footnote_91" href="#FNanchor_91" class="label">[91]</a> Unconsolidated earth contained between the sides of -a rock that has slipped, is frequent in Cornwall, and is called a -<i>Fleukan</i>. </p> - -</div> - -<p><span class="pagenum" id="Page_205">- 205 -</span></p> - -<p>183. A very remarkable fact of this kind occurred not long ago, in -digging the Huddersfield canal in Yorkshire; and a very distinct -account of it is given in the <i>Philosophical Transactions</i>, by -the engineer who directed the work. In carrying a tunnel into the -heart of a hill, the miners came to what is called in the description -a <i>fault</i>, <i>throw</i>, or <i>break</i>, or what we have here -called a shift, which was filled with <i>shale</i> set on edge, mixed -with softer earth, and in some places with small lumps of coal. The -fault or space filled with these materials, was in general about four -yards broad, and lay nearly in the direction of the tunnel, so that a -considerable extent of it was visible. Beside the shale, it contained a -<i>rib</i> of limestone, about four feet thick, which run parallel to -the sides of the <i>fault</i>, and about four feet from the southern -margin of it. On each side of this rib were found balls of limestone, -promiscuously scattered, and of various sizes, from an ounce to one -hundred pounds weight. The balls, when broken, were found to contain -some pyrites near their edges; they were not perfectly globular, but -flattened on the opposite sides, and similar to one another.<a id="FNanchor_92" href="#Footnote_92" class="fnanchor">[92]</a> At the -time when the account was written, about seventy yards of the rib had -been discovered.</p> - -<div class="footnote"> - -<p><a id="Footnote_92" href="#FNanchor_92" class="label">[92]</a> Phil. Trans. 1796, p. 350.</p> - -</div> - -<p><span class="pagenum" id="Page_206">- 206 -</span></p> - -<p>184. Now, it is certain, that neither this rib of limestone, nor the -balls that accompanied it, can have come from above, as there is no -limestone within twenty miles of the place where they were found. They -must, therefore, have been forced up from below, and no doubt belong -to some limestone strata, which lie there at a great depth under the -surface. The length of this fragment of rock, which, from the account, -one must suppose to have been entire, conveys no mean idea, either of -the intensity or regularity of the force by which it was brought into -its present situation. In veins, it is not uncommon to meet with stones -that appear to have come from a greater depth: but this is probably the -most remarkable instance of the same phenomenon, which has appeared in -a mere slip, and none, I think, can speak a language less liable to be -misunderstood.</p> - -<p>185. I shall here mention another mark of violent fracture, that has -been observed in rocks of breccia or pudding-stone, which, though not -of the same kind with the preceding, and of a nature quite peculiar, -belongs rather to this place than any other. In rocks of the kind, -just mentioned, it sometimes happens, that considerable portions are -separated from one another, as if by a mathematical plane, which had -cut right across all the quartzy pebbles in its -<span class="pagenum" id="Page_207">- 207 -</span> -way. None of the -pebbles are drawn out of their sockets, that is, out of the cement that -surrounds them, but are divided in two with a very smooth and even -fracture. The pebbles, in the instances which I have seen, were of -quartz, and other species of primary and much indurated rock.</p> - -<p>Lord <span class="smcap">Webb Seymour</span> and I observed pudding-stone rocks, -exhibiting, instances of this singular kind of fracture, near Oban, in -Argyleshire, about three years ago. The phenomenon was then entirely -new to us both; but I have since met with an instance of the same kind -in Saussure's last work. As the fact is of so particular a kind, I -shall state it in his own words: The place was on the sea shore, near -the little town of Alassio, between Nice and Genoa.</p> - -<p>"En passant entre ces blocs de breche, j'admirai quelques-uns -d'entr'eux, d'une grandeur considérable, et taillés en cubes, avec -la plus parfaite régularité. Il y avoit ceci de remarquable, c'est -que l'action de la pesanteur, qui avoit taillé ces cubes en rompant -leurs couches, avoit coupé tous les cailloux des breches à fleur de -la surface de la pierre, aussi nettement que si c'eût été une masse -molle qu'on eût tranchée verticalement avec un rasoir. Cependant parmi -ces cailloux, la plupart calcaires, il s'en trouvoit de très durs, de -petrosilex, par exemple, même de -<span class="pagenum" id="Page_208">- 208 -</span> -jade, qui étoient tranchées tout -aussi nettement que les autres."<a id="FNanchor_93" href="#Footnote_93" class="fnanchor">[93]</a></p> - -<div class="footnote"> - -<p><a id="Footnote_93" href="#FNanchor_93" class="label">[93]</a> Voyages aux Alpes, tom. iii. § 1731.</p> - -</div> - -<p>186. This description is no doubt accurate, though it involves in it -something of theory, viz. that the fracture was made by the weight of -the stone. This may indeed be true: the operation probably belongs -altogether to the surface, and is one with which the powers of the -mineral regions are not directly concerned. The phenomenon, however, -appears to me, on every supposition, very difficult to explain. In the -specimen which I brought from Oban, the smallest pieces of stone are -cut in two, as well as the largest. The consolidation and hardness of -the mass are very great, and the connection of the different fragments -so perfect, that it is no wonder the whole should break as one stone. -But still, that the fracture should be so exactly in one plane, and -without any shattering, is not a little enigmatical; if it is indeed -a fracture, it must be the consequence of an immense impulse, very -suddenly communicated.</p> - - -<hr class="chap x-ebookmaker-drop" /> - -<div class="chapter"> -<p><span class="pagenum" id="Page_209">- 209 -</span></p> - -<h2 class="nobreak" id="Note_xii"><span class="smcap">Note xii. § 43.</span></h2> -</div> - -<p class="caption3nb"><i>Elevation and inflection of the strata.</i></p> - - -<p>187. The evidence of the different formation of the primary and -secondary strata, and of the changes which the former have undergone, -is best seen at the points where those strata come into contact -with one another. Dr Hutton was not the first who observed these -junctions, though the first who rightly interpreted the appearances -which they exhibit. He has mentioned observations of this sort by De -Luc on the confines of the Hartz; by the author of the <i>Tableau -de la Suisse</i>, at the pass of Yetz; by Voight, in Thuringia; and -Schreiber, at the mountain of Gardette.<a id="FNanchor_94" href="#Footnote_94" class="fnanchor">[94]</a></p> - -<div class="footnote"> - -<p><a id="Footnote_94" href="#FNanchor_94" class="label">[94]</a> Theory of the Earth, vol. i. p. 410 to 453.</p> - -</div> - -<p>The leading facts to be remarked, are,</p> - -<p>I. The vertical or very upright position of the primary or lower strata.</p> - -<p>II. The superstratification of the secondary, in a position nearly -horizontal, so as to be at right angles to those on which they rest.</p> - -<p>III. The interposition of a breccia between them or, as happens in -many cases, the transition of the lowest of the secondary beds into a -<span class="pagenum" id="Page_210">- 210 -</span> -breccia, containing fragments sometimes worn, sometimes angular, of the -primary rock.</p> - -<p>This last is a phenomenon extremely general, and all our subsequent -information confirms Dr Hutton's anticipations concerning it. "It will -be very remarkable," he says, "if similar appearances, (such as those -of the breccia described by Voight,) are always found upon the junction -of the Alpine with the level countries."<a id="FNanchor_95" href="#Footnote_95" class="fnanchor">[95]</a> Saussure, in a part of his -work, not published when Dr Hutton wrote this passage, has attested the -generality of the fact with respect to the whole Alps, from the Tyrol -to the Mediterranean: "Un sait que l'on observe sans aucune exception, -ce sont les amas de débris, sous la forme de blocs, de breches, de -poudingues, de grès, de sable, ou amoncelés, et formant des montagnes, -ou des collines, dispersés sur le bord exterieur, ou même dans les -plaines qui bordent la chaine des Alpes."<a id="FNanchor_96" href="#Footnote_96" class="fnanchor">[96]</a></p> - -<div class="footnote"> - -<p><a id="Footnote_95" href="#FNanchor_95" class="label">[95]</a> Theory of the Earth, vol. i. p. 448.</p> - -<p><a id="Footnote_96" href="#FNanchor_96" class="label">[96]</a> Voyages aux Alpes, tom. iv. § 2330.</p> - -</div> - -<p>This passage is perfectly decisive as to the generality of the fact, -that the Alps, from the Tyrol to the Mediterranean, are bordered all -round by pudding-stones or breccias. At the same time, it is necessary -to remark, that M. Saussure, by enumerating loose blocks and sand, -along with pudding-stones, breccias and grit, confounds together things -which are extremely different, -<span class="pagenum" id="Page_211">- 211 -</span> -and which have had their origin at -periods extremely remote from one another. The consolidated rocks of -breccia, pudding-stone and grit, though they are indications of waste, -have received their present character at the bottom of the sea: the -loose blocks of stone, the sand and gravel, on the other hand, are the -effects of the waste now going forward on the surface of the land, and -are the materials out of which rocks of the three kinds just mentioned -may hereafter be composed. If so skilful a mineralogist as Saussure -is guilty of such inaccuracy, it must be ascribed to the confusion -necessarily arising from the system which he followed, and not to his -own want of discrimination.</p> - -<p>188. The same phenomenon, of a breccia circumscribing the primary -mountains, is met with in Scotland; and the Grampians, wherever they -are bounded by secondary strata, whether on the south or north, afford -examples of it. The breccia generally consists of the fragments of -the primary rock, most commonly rounded, but sometimes also angular, -united by a cement of secondary formation, and the whole disposed -in horizontal beds. It was on the constancy of this accompaniment -of the primary strata, and on the great quantity of highly polished -gravel often included in these breccias, that Dr Hutton grounded the -hypothesis of the double raising -<span class="pagenum" id="Page_212">- 212 -</span> -up and letting down of the ancient -strata. See § 43.</p> - -<p>189. As the spots where the primary and secondary rocks may be seen -in contact with one another are of great importance in geology, and -present to the senses the most striking monuments of the high antiquity -and great revolutions of the globe, it may be useful to point out such -of them as have been observed in this island. To those which Dr Hutton -has described, I have a few more to add, the result of some geological -excursions, which I made in company with the Right Honourable Lord -<span class="smcap">Webb Seymour</span>, to whose assistance I have been much indebted in -the prosecution of these inquiries.</p> - -<p>190. The most southern junction which we observed is at Torbay, where -the ancient schistus which prevails along the coast, from the Land's -End to that point, receives a covering of red horizontal sandstone, -the same which composes the greater part of Devonshire. The spot where -the immediate contact is visible, is on the shore, a little to the -south of Paynton; and one circumstance, which among many others serves -to distinguish the different formation of the two kinds of rock, is, -that the schistus, which is elevated here at an angle of about 45°, is -full of quartz veins, which veins are entirely confined -<span class="pagenum" id="Page_213">- 213 -</span> -to it, and do -not, in as far as we could observe, penetrate into the sandstone, in a -single instance. It is probable, that on the north shore of the bay, -the same line of junction is visible: we saw it at Babicomb Bay, still -more to the northward.</p> - -<p>191. From this place, the secondary strata of different kinds prevail -without interruption, along the coast of the British Channel, and -of the German Ocean, as far as Berwick upon Tweed, and for some -miles beyond it. The sea coast then intersects a primary ridge, the -Lammermuir Hills, which traverses Scotland from east to west, uniting, -near the centre of the country, with the metalliferous range of -Leadhills, and afterwards with the mountains of Galloway. The section -which the sea coast makes of the eastern extremity of this ridge, is -highly instructive, from the great disturbance of the primary strata, -and the variety of their inflections. The junction of these strata -with the secondary, on the south side, is near the little sea-port of -Eyemouth, but the immediate contact is not visible.</p> - -<p>On the north side of the ridge, the junction is at a point called the -<i>Siccar</i>, not far from Dunglass, the seat of Sir James Hall, -Baronet. By being well laid open, and dissected by the working of -the sea, the rock here displays the relation between the two orders -of strata to great -<span class="pagenum" id="Page_214">- 214 -</span> -advantage. Dr Hutton himself has described this -junction; <i>Theory of the Earth</i>, vol. i. p. 464.</p> - -<p>192. From the point just mentioned, the secondary strata continue as -far as Stonehaven, where the southern chain of the Grampian mountains -is intersected by the sea-coast. Here a great mass of pudding-stone -appears to lie on the primary strata, but their immediate contact has -not been observed.</p> - -<p>193. Going along the coast toward the north, the next junctions which -we saw were on the shore, one near Gardenston, and another near Cullen, -in Banffshire. The latter is very distinct; it is about a mile to -the westward of the rocks called <i>The Three Kings</i>, where a red -sandstone, the lower beds of which involve much quartzy gravel, lies -horizontally upon very regular, upright, and highly indurated strata. -Some of these strata are micaceous, and others of the granulated -quartz, mentioned in § 153.</p> - -<p>194. This last is, I believe, the most northern junction which has -been observed in our island. The western coast furnishes several more, -which however are not all visible. The line of separation, between -the primary schistus of the Grampians and the sandstone which covers -it, is intersected at its western extremity by the Frith of Clyde, -not far from Ardencaple in Dunbartonshire. The two kinds of stone can -be -<span class="pagenum" id="Page_215">- 215 -</span> -traced within a few yards of each other, but not to the actual -contact: the beds of sandstone nearest the schistus form as usual a -breccia, loaded with fragments of the primary rock. The secondary rock, -which begins here, continues for about fifty miles south, to Girvan in -Ayrshire, where the primary schistus again rises up, but is not seen in -contact with the secondary. It extends to the Mull of Galloway and the -shores of the Solway Frith.</p> - -<p>The Isle of Arran, however, not far distant from this part of the -coast, contains a junction at its northern extremity, where secondary -strata of limestone lie immediately on a primary micaceous schistus. -This is described by Dr Hutton, and was the first phenomenon of the -kind which he had an opportunity of examining.<a id="FNanchor_97" href="#Footnote_97" class="fnanchor">[97]</a> The junction is -visible but at one spot, and is not seen so distinctly as in some of -the instances just mentioned; but the great quantity of pudding-stone -near it, renders it more interesting than it would be otherwise. As the -greater part of this little island is surrounded by secondary strata, -other junctions might be expected to be visible.</p> - -<div class="footnote"> - -<p><a id="Footnote_97" href="#FNanchor_97" class="label">[97]</a> Theory of the Earth, vol. i. p. 429.</p> - -</div> - -<p>195. On the coast of England and Wales, from the Solway Frith to the -Land's End, though there are several alternations from secondary to -primary -<span class="pagenum" id="Page_216">- 216 -</span> -strata, I know not that any of them have been observed. At St -Bride's Bay, in Pembrokeshire, the primary and secondary strata are -seen very near their junction; but the precise line I believe is not -visible. The coal-pits in the secondary strata, approach here within a -few hundred yards of the primary. The secondary strata which commence -at this place, occupy both sides of the Bristol Channel, and meet the -Cornish schistus, which extends across the north of Devonshire to the -Quantock Hills, in a line that may be looked for on the sea coast, some -where between Watchett and Minehead.</p> - -<p>196. Besides the sea coast, the beds of rivers may be expected to -afford information on this subject. To the instances I have mentioned, -I have accordingly two others from the inland country to be added. One -of them is from the river Jed, a little way above Jedburgh, where the -secondary strata are seen lying horizontally on the primary, a section -of both being made by the bed of the river. The phenomena here are very -distinct, and strongly marked; Dr Hutton has described and represented -them in a plate.<a id="FNanchor_98" href="#Footnote_98" class="fnanchor">[98]</a> He has mentioned another junction, not far from -this, which he saw in the Tiviot. Both these belong to the same primary -ridge with the Siccar point.</p> - -<div class="footnote"> - -<p><a id="Footnote_98" href="#FNanchor_98" class="label">[98]</a> Theory of the Earth, vol. i. p. 430; also plate 3.</p> - -</div> - -<p><span class="pagenum" id="Page_217">- 217 -</span></p> - -<p>197. I shall mention only one other, which was discovered by Lord Webb -Seymour and myself, at the foot of the high mountain of Ingleborough, -in Yorkshire. As we went along the Askrig road from Ingleton, about a -mile and a half from the latter, an opening appeared in the side of -the hill, on the right, about one hundred yards from the road, formed -by a large stone, which lay horizontally, and was supported by two -others, standing upright. On going up to the spot, we found it was the -mouth of a small cave, the stone lying horizontally, being part of a -limestone bed, and the two upright stones, vertical plates of a primary -argillaceous schistus. The limestone bed, which formed the roof of the -cave, was nearly horizontal, declining to the south-east; the schistus -nearly vertical, stretching from north-west by west, to south-east by -east. The schistus, though close in contact with the limestone, seemed -to contain nothing calcareous, and did not effervesce with acids in the -slightest degree.</p> - -<p>As this cave is at the foot of Ingleborough, a cold wind, 24° below the -temperature of the external air, which issued from the mouth of it, -might very well be supposed to come from the inmost recesses of that -mountain. Ingleborough, which consists entirely of strata of limestone -and grit, nearly horizontal, and alternating with one another, rises -to the height of 1800 or 2000 feet -<span class="pagenum" id="Page_218">- 218 -</span> -above the spot where we now stood. -This, I believe, is the greatest thickness of secondary strata that -has ever been observed incumbent on the primary, and it is therefore -a geological fact highly deserving of attention. The country all -round, to a very great extent, is composed of limestone, with a few -beds of grit interposed, and forming, beside Ingleborough, some other -high mountains, such as Wharnside and Pennigant, all resting, it is -probable, on the same foundation.</p> - -<p>At the spot just described, no breccia appeared to be interposed -between the primitive and secondary rock; but we found a breccia at -another point of the same junction, not far distant. This was at a -cascade, in the river Greta, called Thornton Force, about two miles -and a half from the place just mentioned. The Greta here precipitates -itself from a horizontal rock of limestone; and, after a fall of -about eighteen or twenty feet, is received into a bason which it has -worked out in the primary schistus. This schistus is in beds almost -perpendicular; it exactly resembles that which has Just been described, -and stretches nearly in the same direction. On the south side of the -river a breccia was seen, lying upon the schistus, or rather, it might -be said, that the lowest beds of limestone contained in them many -rounded fragments of stone, which, on comparison, -<span class="pagenum" id="Page_219">- 219 -</span> -resembled exactly -the schistus underneath. The primary rock itself is here seven or eight -hundred feet above the level of the sea.</p> - -<p>The same schistus, somewhat lower down the valley, and nearer to -Ingleton, appears in large quantities, and is quarried for slate. Here, -however, the immediate junction of the limestone and schistus does not -appear.</p> - -<p>I have dwelt longer on the description of these appearances than on -any others of the same kind, because, from the great mass of secondary -strata which here covers the primary, the circumstances are such as we -cannot expect to see very often exemplified.</p> - -<p>198. The Lakes of Cumberland are much visited by travellers; and it may -be worth remarking, on that account, that, as the site of these lakes -is a patch of primary country, bounded on all sides by secondary, so, -in the rivers that run from the lakes, such junctions as we are now -treating of may be expected to be found. Under Dun-Mallet, on the side -toward Ulles Water, we observed a breccia, which was in horizontal -layers, and seemed to lie on the primary schistus, so that the whole -hill is perhaps a piece of more indurated breccia, or secondary rock, -which has resisted the wearing and washing down of the rivers better -than the rest.</p> - -<p>199. After ascertaining the fact of the disturbance of the strata, and -their removal from their -<span class="pagenum" id="Page_220">- 220 -</span> -original position, it is of consequence to -inquire into the direction of the force by which these changes have -been produced. Now, if the disturbed or elevated strata, were every -where in planes, without bending or sinuosity, it might perhaps be -hard to determine, whether that force had acted in the direction of -gravity, or in the opposite. Either supposition would account for the -appearances; and, as gravity is a known force, providing we can find -some place fit to receive the matter impelled downward by it, its -action would furnish the most probable solution of the difficulty.</p> - -<p>It is on this principle that the Neptunian system proceeds, imagining, -that certain great caverns or vacuities having been opened in the -interior of the globe, a great part of the waters which formerly -covered its surface, retired into them, and much of the solid rock also -sunk down at the same time. In this way, one extremity of a stratum -has been elevated, while the other has been depressed, and a certain -inclination to the horizon has been given to the whole of it. Thus one -cause serves two purposes; the vacuities in the interior of the earth -account, both for the depression of the sea, and the elevation of the -land; and the Neptunists, if the phenomena were all such as have been -now stated, might boast of a felicity of explanation, not very usual in -their system.</p> - -<p><span class="pagenum" id="Page_221">- 221 -</span></p> - -<p>But this appearance of success vanishes, when the elevation and -disturbance of the strata are more minutely examined, and are found -to include waving and inflection, in a great variety of forms. It -then becomes evident, that the beds of rock, at the time when they -were disturbed from their horizontal position, had not their present -hardness and rigidity, but were, in a certain degree at least, soft -and flexible. Without these qualities, they could not have received, -as they have often done, the curvature of a circle, not many feet, -nay, not many inches, in diameter; nor could they have been bent into -superficies, with their curvature in opposite directions, so that -the same surface is in one part convex, and in another concave, on -the same side, with a line of contrary flexure interposed. These are -appearances, not reconcilable with the mere falling in, and breaking -down of indurated rocks.</p> - -<p>200. The inflections and wavings that we are here speaking of, though -not peculiar to the primary strata, are found most frequently among -them, and are perfectly familiar to every one who his travelled among -mountains with any view to the study of geology. The following are a -few instances of this phenomenon out of a great number which might be -produced.</p> - -<p><span class="pagenum" id="Page_222">- 222 -</span></p> - -<p>Saussure, in describing the route from Geneva to Chamouni, mentions -many remarkable instances of the bending of the strata, and -particularly where the small stream of Nant d'Arpenaz forms a cascade, -by falling over the face of a perpendicular limestone rock. The strata -of this rock are bent into circular arches, extremely regular, and with -their concavity turned to the left. What deserves particularly to be -remarked, is, that a mountain behind the cascade has its strata bent -in a direction opposite to the former, or with their concavity to the -right. There is no doubt that the strata of both rocks are the same, so -that a vertical section of them would give a curve, in the figure of an -S.<a id="FNanchor_99" href="#Footnote_99" class="fnanchor">[99]</a> These circumstances are mentioned by Saussure, and from them we -may infer this other property of these strata, that their section by a -horizontal plane, must exhibit a system of straight lines, probably all -parallel to one another.</p> - -<div class="footnote"> - -<p><a id="Footnote_99" href="#FNanchor_99" class="label">[99]</a> Voyages aux Alpes, vol i. § 472; also, Theory of the -Earth, vol. ii. p. 30.</p> - -</div> - -<p>The same mineralogist describes the calcareous strata which compose -the mountain Axenberg, on the side of the Lake of Lucerne, as having -from top to bottom of the mountain the form of the letter S compressed, -(<i>ecrasée</i>) with their curvature in some places very great. -These inflections -<span class="pagenum" id="Page_223">- 223 -</span> -are repeated several times, and often in contrary -directions; the layers are sometimes broken, where their curvature is -greatest.<a id="FNanchor_100" href="#Footnote_100" class="fnanchor">[100]</a></p> - -<div class="footnote"> - -<p><a id="Footnote_100" href="#FNanchor_100" class="label">[100]</a> Voyages aux Alpes, tom. iv. § 1935.</p> - -</div> - -<p>On the side of the same lake, is another instance of bent strata, in a -mountain, of which the beds are horizontal in the lower part, but are -bent at one end upwards, in the form of the letter C. The horizontal -part is of great extent, and the rock is also calcareous,<a id="FNanchor_101" href="#Footnote_101" class="fnanchor">[101]</a></p> - -<div class="footnote"> - -<p><a id="Footnote_101" href="#FNanchor_101" class="label">[101]</a> <i>Ibid.</i> § 337.</p> - -</div> - -<p>The Montagne de la Tuile, near Montmelian, receives its name from the -beds of rock being incurvated in form of a tyle.<a id="FNanchor_102" href="#Footnote_102" class="fnanchor">[102]</a> Among secondary -mountains, the same kind of phenomena are observed, though less -frequently, and with less variety of inflection. The chain of Jura is -secondary, and the beds which compose it are of limestone, or of grit: -they are bent in such a manner, that in a transverse section of the -mountain, each layer would have the figure of a parabola.<a id="FNanchor_103" href="#Footnote_103" class="fnanchor">[103]</a></p> - -<div class="footnote"> - -<p><a id="Footnote_102" href="#FNanchor_102" class="label">[102]</a> <i>Ibid.</i> vol. iii. § 1182, and plate i.</p> - -</div> - -<div class="footnote"> - -<p><a id="Footnote_103" href="#FNanchor_103" class="label">[103]</a> <i>Ibid.</i> tom. i. § 334.</p> - -</div> - -<p>201. The Pyrenees furnish abundance of phenomena of the same kind, as -we learn from the <i>Essai sur la Mineralogie des Pyrenées</i>. The -<span class="pagenum" id="Page_224">- 224 -</span> -calcareous strata of the valley of Aspe, represented plate v. of that -work, deserve particularly to be remarked.</p> - -<p>202. Our own island abounds with examples of the bending and inflection -of the strata, especially the primary, and many of them very much -resembling those in the Alps and Pyrenees. On the top of the mountain -of <i>Ben-Lawers</i>, in Perthshire, there is a rock, the face of -which exhibits a section of a great number of thin equidistant layers, -bent backwards and forwards like those described by Saussure; and -this unequivocal proof of the rock having once existed in the state -of a flexible and tenacious paste, is rendered more striking, by the -great elevation of the spot, and the ruggedness and induration, both -of the stone itself, and of every thing that surrounds it. Many other -mountains in this tract consist of a schistus, which is talcose rather -than micaceous, and subject, in a remarkable degree, to the sort of -sinuosity and inflection here treated of.</p> - -<p>The appearances of the primary strata on the coast of Berwickshire, -have been already mentioned, as affording much valuable instruction in -geology. They also exemplify the waving and inflection of the strata -on a large scale, and with great variety. A section of some of them -<span class="pagenum" id="Page_225">- 225 -</span> -is given by Dr Hutton, in his <i>Theory of the Earth</i>, vol. i. from -a drawing made by Sir James Hall. The nature of the curve superficies -into which the schistus is bent, is the better understood from this, -that, besides transverse sections from north to south, the deep -indentures which the sea has made, and the projecting points of rock, -exhibit many longitudinal sections, in a direction from east to west.</p> - -<p>203. The dock-yards at Plymouth are in several places cut out of a -solid rock of primary schistus, singularly incurvated. The inflections -are seen there to great advantage, being exhibited in three sections, -at right angles to one another, transverse, longitudinal and horizontal.</p> - -<p>204. From these instances, to which it were easy to add many more, two -conclusions may be drawn. The first of these is very obvious, viz. -that the strata must have been pliant and soft when they acquired -their present form. The bending of an indurated bed of stone into an -arch of great curvature, and without fracture, as in the preceding -examples, is a physical impossibility. Saussure has indeed observed a -fracture to accompany the bending, in one or two cases; but it is an -uncommon phenomenon, and, where it happens, must no doubt be understood -to indicate an imperfect flexibility. Now, if it be granted that the -strata were at any time -<span class="pagenum" id="Page_226">- 226 -</span> -soft and flexible, since their complete -formation, it will be found impossible to deny their having been -softened by the application of heat.</p> - -<p>205. The second conclusion, alluded to above, results from a property, -which belongs very generally, if not universally, to the inflections of -the strata. This consists in their curvature being simple, or in one -dimension only, like a cylindric superficies, not double, or in two -dimensions, like the superficies of a sphere or spheroid. This may be -otherwise expressed by saying, that the sections of the bent strata, -by a horizontal plane, are straight lines, parallel to one another. On -this account, every such stratum seems as if it were bent over all axis -and the axes of all these different bendings, for a great extent of -country, are nearly parallel.</p> - -<p>The truth of this is evident, where the strata are seen both -transversely and longitudinally. It holds remarkably of the primary -schistus on the coast of Berwickshire; where the beds of rock, if -cut transversely, by a vertical plane, exhibit the figures of very -complicated curves, with various maxima and minima, and points of -contrary flexure; but, if they are cut by a horizontal plane, the -section will produce nothing but straight lines, nearly parallel.</p> - -<p><span class="pagenum" id="Page_227">- 227 -</span></p> - -<p>206. The constancy of the direction of the primary strata, when -estimated by their intersection with the horizontal plane, is often -very remarkable. Their elevation and flexure are subject to great and -sudden changes, so as to pass not only from greater to less, but from -one side to the opposite, within a small distance; but the horizontal -line in which they <i>stretch</i>, usually preserves the same bearing -to a great extent. The general direction of the primary strata, in -the south part of Scotland, is from E.N.E. to W.S.W.; and the same -is nearly true of those which compose the ridge of the Grampians on -the north, and the hills of Cumberland and Westmoreland toward the -south, though between the schistus of these three tracts, there is no -communication at the surface, each being entirely separated from the -one next it, by the interposition of secondary strata. I have already -mentioned the observations of Lord Webb Seymour and myself, at the -foot of Ingleborough; and it appears from them, that the vertical -schistus on which that mountain rests, though it still preserves an -eastern and western direction, varies several points from that of the -more northern strata. The strata of Wales return more to the first -mentioned direction, and those of Devonshire and Cornwall agree with -it very nearly. In all this, it will be easily conceived, -<span class="pagenum" id="Page_228">- 228 -</span> -that I do -not mean to speak with absolute precision, or to deny the existence of -great local irregularities. The result given is only a kind of average, -deduced from observations hardly susceptible of great exactness, and -not yet sufficiently multiplied to give to the conclusion all the -accuracy it may attain.</p> - -<p>207. This tendency of the primary strata to take a uniform direction, -has also been observed in other countries. Saussure remarked in the -Alps, that the beds of schistus are generally parallel to the chains of -mountains composed of them;<a id="FNanchor_104" href="#Footnote_104" class="fnanchor">[104]</a> and this remark is probably applicable -to all mountains consisting of primary strata. The general direction, -therefore, of the schistus of the Alps, must be confined between W. -10° S. and W. 40° S. In the Pyrenees, the direction of the strata is -about W.N.W.<a id="FNanchor_105" href="#Footnote_105" class="fnanchor">[105]</a> If Saussure's rule may be depended on, the schistus -of the Altaic, and most of the other great chains in the old continent, -are in directions that run considerably to the south of west. The -Urals, and perhaps some other of the northern chains, are however -entirely different. In the Urals, as we learn not only from the general -direction of the chain, but from a section of it in the 10th volume -<span class="pagenum" id="Page_229">- 229 -</span> -of -the Nova Acta of Petersburgh (Tab. 12,) the direction of the strata is -nearly from N. to S. This last is probably the direction in the great -chains of South America; so that the uniformity of direction in the -primary strata, which some mineralogists would extend to those of the -whole earth, is certainly imaginary, though there can be no doubt that -it extends over very large portions of the earth's surface.<a id="FNanchor_106" href="#Footnote_106" class="fnanchor">[106]</a></p> - -<div class="footnote"> - -<p><a id="Footnote_104" href="#FNanchor_104" class="label">[104]</a> Voyage aux Alpes, tom. i. § 577.</p> - -<p><a id="Footnote_105" href="#FNanchor_105" class="label">[105]</a> Essai sur la Mineralogie des Pyrenées.</p> - -<p><a id="Footnote_106" href="#FNanchor_106" class="label">[106]</a> It is perhaps unnecessary to observe, that the two -propositions, that the intersections of the strata with the horizon -are parallel lines; and that they are lines which reserve the same -bearing with respect to the points of the compass; are nearly the same -thing for tracts of moderate extent, but for large portions of the -earth's surface are extremely different. If, for instance, the belt -of primary vertical schistus, which traverses the south of Scotland, -were to be produced eastward in the same plane, from its northern -extremity, where its direction is E.N.E. and its latitude 55° 57', it -would cut the meridian always less obliquely as it advanced, till, -having increased it longitude about 26° 28', it would be at right -angles to the meridian, and its direction of consequence due east and -west. This would happen in the parallel of 58° 51', (on the shore of -the Gulf of Finland, near Revel,) the strata being now extended about -880 G. miles from the Siccar Point. Conversely, vertical strata, having -the same bearing with respect to the meridian, may be in planes very -much inclined to one another. A stratum which bears east and west in -Cornwall, and one that does the same at the east end of the Altaic, -will be in planes, which, if produced, would cut one another at right -angles. All this is sufficiently plain from the doctrine of the -sphere, and is mentioned here merely as a caution to prevent too hasty -conclusions from being drawn from any correspondence of bearing among -the strata of remote countries.</p> - -<p>For the sake of those who would deduce the medium bearing of any body -of strata from a number of observations, it may be proper to take -notice, that the true average is not to be found by simply taking -an arithimetical mean among all the observations. A more exact way -is to work by the traverse table, as in keeping a ship's reckoning, -(supposing the distance run to be always unity,) and to compute from -the observed bearings the amount of all the southing or northing, and -also all the easting and westing. The sum of all the latter, divided -by the sum of all the former, is the tangent of the angle which the -general direction of the strata makes with the meridian.</p> - -</div> - -<p><span class="pagenum" id="Page_230">- 230 -</span></p> - -<p>208. The tendency of the primary strata to remain straight in the -horizontal direction, and to be bent in the vertical, is a phenomenon -which points very directly to the causes from whence it has arisen. A -surface of simple curvature, or a surface straight in one direction, -is -<span class="pagenum" id="Page_231">- 231 -</span> -what the application of forces to different points of a plane, -which is flexible, though with a certain degree of rigidity, will -naturally produce. The supposition, therefore, that these strata were -once flat and horizontal, and were impelled upward from that situation -before they had become rigid or hard, will explain their having the -kind of curvature which removes them as little as possible from their -original condition. But no other hypothesis affords any reason why -they should have that curvature more than any other. From the falling -in of roofs of caverns, we might expect fracture and dislocation, -without any order or regularity; but certainly no bending or sinuosity, -nor any symmetrical arrangement. If, as some mineralogists allege, -the curvature, as well as inclination of the strata, arose from the -irregularities of the bottom on which they were deposited, why is the -former in one dimension only, and why is it not in every direction, -like that of hills and valleys, or the actual surface of the earth? -Or, lastly, if the whole structure of the primitive mountains is an -effect of crystallization, and if these mountains are now such as -they have ever been from the time of their consolidation, whence is -it, that, in their bendings the law just mentioned is so constantly -observed? Indeed, the idea of ascribing the inflections of the strata -to crystallization, though suggested -<span class="pagenum" id="Page_232">- 232 -</span> -by Saussure,<a id="FNanchor_107" href="#Footnote_107" class="fnanchor">[107]</a> and since -become a favourite system with several mineralogists, appears to me -in the highest degree unsatisfactory and illusive. The purpose for -which crystallization is here introduced, is not to give a specific -figure to a particular substance, but to arrange the substances which -it has formed and figured, according to certain rules; a work which -we know not how it is to perform, and in which we have no experience -of its power. Accordingly, this principle does not account, in any -way whatever, for the circumstances which attend the inflection of -the strata, for the simple curvature which they affect, nor for that -parallelism of their layers, which, in all their bendings, is so -accurately preserved. It does, indeed, so little serve to explain -these facts, that, were the appearances completely reversed; did the -strata assume the most complex, instead of the most simple curvature; -instead of equidistant, were they converging, or alternately receding -and approaching to one another; the theory of crystallization might -be equally applied to them. The state of the phenomena is a matter of -perfect indifference to such a theory as this; all things are explained -by it with the same facility; the straight and -<span class="pagenum" id="Page_233">- 233 -</span> -the crooked, the square -and the round, the moveable and the immoveable. Is it not evident that -such an explanation is a mere word; or, if any thing more than a word, -an expression of our ignorance, so awkward and indirect, as to deprive -us of whatever credit might have been gained by a plain and candid -avowal of it?</p> - -<div class="footnote"> - -<p><a id="Footnote_107" href="#FNanchor_107" class="label">[107]</a> Voyages aux Alpes, tom. i. § 475.</p> - -</div> - -<p>It should never be forgotten, that a theory which accounts for <i>any -thing</i>, and a theory which accounts for <i>nothing</i>, stand -precisely on the same footing, and ought to be banished from all parts -of philosophy, as they have been from those sciences which are justly -honoured with the name of accurate. The animated orbs of Aristotle, -and the vortices of Des Cartes, have long ceased to be mentioned in -physical astronomy; the first, because, they accounted for every thing -alike; the second, because, when they accounted for one thing, they -never could be made to account for another. Both theories, therefore, -have very properly been rejected; and, when geology shall undergo a -similar purification, the principle we have been considering will not -be the only sacrifice required of the Neptunian system.</p> - -<p>209. An appearance observed in some kinds of primary schistus, which -clearly indicates their deposition by water, and in planes very -different from those in which we now see them, though it might have -been introduced before, is also -<span class="pagenum" id="Page_234">- 234 -</span> -much connected with the present -argument. This appearance consists of small wavings or undulæ on the -surface of the plates of schistus, precisely similar to these marks -which are left by the sea on a gently inclining beach of sand, at the -ebbing of the tide. All the species of schistus do not seem to afford -instances of these wavings. The rocks which do so, are, I think, -chiefly of the argillaceous kind, but often highly indurated; so that -the laminæ containing the impressions are not to be torn asunder but -with great difficulty. Instances of it abound in the schistus of -Berwickshire, and are also not unfrequent in that of Galloway. All must -agree about the agent which produced these marks; it could be no other -than the sea; but it must have been the sea acting on loose, small and -round particles, lying on a surface which was nearly horizontal.</p> - -<p>210. Dr Hutton's theory is no where stronger, than in what relates -to the elevation and inflection of the strata; points in which all -others are so egregiously defective. The phenomena to be connected -are here extremely various, and even in appearance contradictory: -the horizontally of one part of the strata; the inclined or vertical -position of another; the perfect planes in which one set are extended; -the breaking and -<span class="pagenum" id="Page_235">- 235 -</span> -dislocation found in a second; the inflection and -sinuosity of a third; and almost every where the utmost rigidity and -induration, combined with appearances of the greatest softness and -flexibility; the preservation of a parallelism of superficies in the -midst of so much irregularity, and the assumption of a determinate -species of curvature, under circumstances the most dissimilar; all -these appearances were to be connected with one another, and with -the consolidation of the strata, and this is done by the twofold -hypothesis, of aqueous deposition, and the action of subterraneous -heat. When these circumstances are fairly considered, and when the -shifts which other systems are put to on this occasion are remembered, -I think it will be granted, that few attempts at generalization have -been more successful, than that which has been made by the Huttonian -Theory.</p> - -<p>211. To the fact of the elevation of the strata, the study of geology -is much indebted. The stratified form of a great proportion of the -earth's surface, gives to minerals that organization and regularity, -which makes their disposition an object of science, and their inclined -position serves to bring that organization into view, from far greater -depths than we can ever reach by artificial excavations. If, for -instance, the termination of strata, that make with the horizon -<span class="pagenum" id="Page_236">- 236 -</span> -an angle of 30°, lying one over another, is seen for a horizontal distance -of two miles; then it is certain, that if these strata have that extent -under ground, which may be reasonably supposed, the thickness of the -whole mass, measured by a line perpendicular to its stratification, is -half the horizontal distance, or amounts to one mile. It would also -require a pit to be sunk from the uppermost of these strata, to the -depth of (2 miles × tan 30°, =) 6093 feet before it could intersect the -undermost; and therefore, if we suppose the same stratum to preserve -the same character for the extent of some miles, we obtain the same -information from inspecting the edge-seams, and see in reality as far -into the bowels of the earth, as if we had sunk a perpendicular shaft -to the depth of 6000 feet.</p> - -<p>In general, the length of the horizontal line drawn across the strata, -from the lowest in position to the highest, multiplied into the sine of -the inclination of the strata to the horizon, gives the thickness of -the whole, measured perpendicularly to the plane of the stratification: -and the same horizontal distance, multiplied into the tangent of the -inclination, gives the actual depth at which the lowest stratum would -meet a perpendicular to the horizon, drawn from the highest extremity -of the upper stratum.</p> - -<p><span class="pagenum" id="Page_237">- 237 -</span></p> - -<p>In many cases, the extent of stratified materials admitting of such -an examination as this, is much greater than has now been supposed. -M. Pallas describes a range of hills on the south-east side of the -peninsula of the Tauride, which is cut down perpendicularly toward the -sea, and offers a complete section of the parallel beds of a primary, -or, as he calls it, an ancient limestone, inclined at an angle of -45° to the horizon; and this section continues for the length of 130 -<i>versts</i>, or about 86 English miles. The beds are so regular, -that M. Pallas compares them to the leaves of a book.<a id="FNanchor_108" href="#Footnote_108" class="fnanchor">[108]</a> The height -of these hills does not exceed 1200 feet, but the real height of the -uppermost stratum above the undermost, is 86 × √½ = 86 × 5/7 = 61 -miles nearly.</p> - -<div class="footnote"> - -<p><a id="Footnote_108" href="#FNanchor_108" class="label">[108]</a> See Nova Acta Acad. Petropol. tom. x. (1792,) p. 257.</p> - -</div> - -<p>If therefore we conceive that there is no shift in all this great -system of strata, we in reality are enabled, by means of it, to see no -less than 61 miles into the interior of the earth, nearly a 65th part -of the radius of the globe. It is true, that we can hardly suppose so -great a body of strata to have been raised without shifting, so that -we must diminish this depth considerably; but were it reduced even to -one-half it -<span class="pagenum" id="Page_238">- 238 -</span> -will appear, that men see much farther into the interior -of the globe than they are aware of, and that geologists are reproached -without reason for forming theories of the earth, when all that they -can do is but to make a few scratches on its surface. Art indeed can do -little more; but nature supplies the deficiency, and makes discoveries -to the attentive observer, on the same great scale with her other -operations.</p> - -<p>The simplest account that can be given of the vast body of parallel and -highly inclined strata just mentioned, is, that it consists of the ends -of horizontal strata, or of strata not greatly inclined, that have been -forced up when they were all soft and flexible. This is a much more -conceivable supposition than Pallas's, viz. that the greater part of -this mass has sunk down into some vast cavern in the interior of the -earth.</p> - - -<hr class="chap x-ebookmaker-drop" /> - -<div class="chapter"> -<p><span class="pagenum" id="Page_239">- 239 -</span></p> - -<h2 class="nobreak" id="Note_xiii"><span class="smcap">Note xiii. § 53.</span></h2> -</div> - -<p class="caption3nb"><i>Metallic Veins.</i></p> - - -<p>212. The large specimens of native iron found in Siberia and Peru, -mentioned above, § 51, are among the most curious facts in the natural -history of metals. It has been doubted, however, by some, whether they -really belong to natural history, or are not rather to be accounted -artificial productions. If they had been found in the heart of rocks, -or in the midst of metallic veins, no doubt of this sort could possibly -have been entertained; but, as they lie quite on the surface, in the -middle of flat countries, and at a distance from any known vein of -metal, the conjecture that they may be artificial, and the remains of -the iron founderies of ancient and unknown nations, is at first sight -not entirely destitute of probability. This probability, however, will -appear to be the less, the more carefully the specimens are examined. -The metal is too perfect, and the masses too large, to have been melted -in the furnaces, or to have been transported by the machinery, of a -rude people. The specimen in South America weighs 300 quintals, or -about 15 tons, and is -<span class="pagenum" id="Page_240">- 240 -</span> -soft and malleable.<a id="FNanchor_109" href="#Footnote_109" class="fnanchor">[109]</a> The Siberian specimen, -described by Pallas, is also very large; it is soft and malleable, and -full of round cavities, containing a substance, which, on examination, -has been found to be chrysolite.<a id="FNanchor_110" href="#Footnote_110" class="fnanchor">[110]</a> Now, it is certainly quite -impossible, that, in an artificial fusion, so much chrysolite could -have come by any means to be involved in the iron; but, if the -fusion was natural, and happened in a mineral vein, the iron and the -chrysolite were both in their native place, and their meeting together -has nothing in it that is inexplicable.</p> - -<div class="footnote"> - -<p><a id="Footnote_109" href="#FNanchor_109" class="label">[109]</a> Phil. Trans. 1788, p. 37. also p. 183, &c.</p> - -<p><a id="Footnote_110" href="#FNanchor_110" class="label">[110]</a> Kirwan's Mineralogy, vol. ii. art. Native Iron.</p> - -</div> - -<p>213. Some circumstances in the description of the specimen in South -America, such as the impressions of the feet of men and of birds on its -surface, are not to be accounted for on any hypothesis, and certainly -require more careful investigation. It is said, that this iron is -very little subject to rust, and the analysis of a piece of it by -<span class="smcap">Proust</span> makes it probable, that it owes this quality to its -union with nickel.<a id="FNanchor_111" href="#Footnote_111" class="fnanchor">[111]</a> It appears, also, that the country of Chaco, -where this specimen was found, affords many others of the same kind, -one of which is mentioned in the description above referred to. That -<span class="pagenum" id="Page_241">- 241 -</span> -country lies on the east side of the Plata, and is a plain extremely -level, and of vast extent, without any appearance of mineral veins; -but such veins may nevertheless exist undiscovered, in a tract subject -to periodical inundations, and where the native rock is covered with -alluvial earth and gravel to a great depth. The veins maybe washed -away, and the more durable substances, such as those pieces of native -iron, may be left behind; and, though they must be of a formation -extremely ancient, according to this hypothesis, they may not have been -very long on the surface.</p> - -<div class="footnote"> - -<p><a id="Footnote_111" href="#FNanchor_111" class="label">[111]</a> Annales de Chimie, tom. xxxv. Messidor, p. 47.</p> - -</div> - -<p>214. Specimens of native iron have been found, less remarkable than the -preceding for their size, but in circumstances that excluded all idea -of artificial fusion. Of this sort was <span class="smcap">Margraaf's</span> specimen -of native iron, the first of the kind that was known; it consisted -of small bits of soft and malleable iron, found in the heart of a -brown iron-stone.<a id="FNanchor_112" href="#Footnote_112" class="fnanchor">[112]</a> This makes it certain, that native iron is a -natural production, and the mere circumstance of great magnitude, in -the specimens before mentioned, does not entitle us to doubt of their -having that same origin. It is a circumstance, besides, not in the -least material to this argument; the smallest -<span class="pagenum" id="Page_242">- 242 -</span> -piece of native iron -being as much a proof of fusion as the greatest; and the specimen -of Margraaf being just as conclusive in favour of the Huttonian -Theory, as those of Pallas or De Celis, supposing their reality in -mineral productions to be completely established. À metal malleable -and ductile, in ever so small a quantity, cannot be the result of -precipitation from a menstruum, without a very particular combination -of circumstances. Such a metal, can the other hand, can be readily -produced by igneous fusion; so that here the negative and affirmative -parts of the inductive argument may both be regarded as complete.</p> - -<div class="footnote"> - -<p><a id="Footnote_112" href="#FNanchor_112" class="label">[112]</a> Kirwan's Mineralogy, vol. ii. p. 156.</p> - -</div> - -<p>215. Mr Kirwan, in order to account for the magnitude of the two large -specimens mentioned above, supposes, that small pieces of native iron -(about the formation of which he appears to have no difficulty) have -been originally agglutinated by petroleum, and left bare, when the -surrounding stony or earthy masses either withered or were washed -off.<a id="FNanchor_113" href="#Footnote_113" class="fnanchor">[113]</a> This is no doubt the most singular of all the opinions which -have been advanced on the subject; and, as it borrows nothing from -analogy, it admits of no proof, and requires no refutation. None but a -chemist of eminence could have ventured with -<span class="pagenum" id="Page_243">- 243 -</span> -impunity on an assertion -so inconsistent with all the phenomena and principles of his science.</p> - -<div class="footnote"> - -<p><a id="Footnote_113" href="#FNanchor_113" class="label">[113]</a> Geol. Essays, p. 405.</p> - -</div> - -<p>216. A remark of the same author, on the subject of the native gold -found in the county of Wicklow in Ireland, is entitled to more -attention. "That these lumps of native gold," he says, "were never in -fusion, is evident from their low specific gravity, and the grains of -sand found in the midst of them. I found the specific gravity of a lump -of the size of a nutmeg to be only 12800, whereas, after fusion, it -became 18700."<a id="FNanchor_114" href="#Footnote_114" class="fnanchor">[114]</a></p> - -<div class="footnote"> - -<p><a id="Footnote_114" href="#FNanchor_114" class="label">[114]</a> <i>Ibid.</i> p. 402.</p> - -</div> - -<p>This argument is plausible; but, I think, nevertheless inconclusive. -The sand found in the gold, accounts, at least in part, for its -lightness. It is only by repeated fusions that any of the metals is -brought to its utmost purity and highest specific gravity; and on no -supposition can the melting of gold in the mineral regions, be very -likely to separate it from heterogeneous substances. That quartzy -sand should be found in it, after such a process, is naturally to be -expected. The impressions which the quartz crystals have left on the -Wicklow gold, would be received as a full proof of the fusion of that -metal, if geologists always regulated -<span class="pagenum" id="Page_244">- 244 -</span> -their theories by the principles -which determine the belief of ordinary men.</p> - -<p>217. Don Rubin de Celis, in the paper referred to above, mentions some -masses of silver found at Quantajaia, and also some dust of platina, in -terms that excite a strong desire to have more information concerning -them. They are considered by him as effects of volcanic fire; so we -may conclude, that they contain evident marks of fusion, and would in -this system be ascribed to that heat, from which volcanic fire is but a -partial and accidental derivation.</p> - -<p>218. The state also in which gold and silver are often found pervading -masses of quartz, and shooting across them in every direction, -furnishes a strong argument for the igneous origin, both of the metal -and the stone. From such specimens, it is evident, that the quartz -and the metal crystallized, or passed from a fluid to a solid state, -at the same time; and it is hardly less clear, that this fluidity did -not proceed from solution in any menstruum: For the menstruum, whether -water or the <i>chaotic fluid</i>, to enable it to dissolve the quartz, -must have had an alkaline impregnation; and, to enable it to dissolve -the metal, it must have had, at the same time, an acid impregnation. -But these two opposite qualities could not reside in the same subject; -the add and alkali would unite together, and, -<span class="pagenum" id="Page_245">- 245 -</span> -if equally powerful, -form a neutral salt, (like sea-salt,) incapable of acting either on -the metallic or the siliceous body. If the acid was most powerful, the -compound salt might act on the metal, but not at all upon the quartz; -and if the alkali was most powerful, the compound might act on the -quartz, but not at all on the metal. In no case, therefore, could it -act on both at the same time. Fire or heat, if sufficiently intense, -is not subject to this difficulty, as it could exercise its force with -equal effect on both bodies.</p> - -<p>219. The simultaneous consolidation of the quartz and the metal is -indeed so highly improbable, that the Neptunists rather suppose, that -the ramifications in such specimens as are here alluded to, have been -produced by the metal defusing itself through <i>rifts</i> already -formed in the stone.<a id="FNanchor_115" href="#Footnote_115" class="fnanchor">[115]</a> But it may be answered, that between the -channels in which the metal pervades the quartz, and the ordinary -cracks or fissures in stones, there is no resemblance whatever: That -a system of hollow tubes, winding through a stone, (as the tubes in -question, must have been, according to this hypothesis, before they -were filled by the metal,) is itself far more inconceivable than the -thing which it is intended to explain; -<span class="pagenum" id="Page_246">- 246 -</span> -and lastly, that if the stone -was perforated by such tubes, it would still be infinite to one that -they did not all exactly join, or inosculate with one another.</p> - -<div class="footnote"> - -<p><a id="Footnote_115" href="#FNanchor_115" class="label">[115]</a> Geol. Essays, p. 401.</p> - -</div> - -<p>220. The compenetration, as it may be called, of two heterogeneous -substances, has here furnished a proof of their having been melted by -fire. The inclusion of one heterogeneous substance within another, -as happens among the spars and drusens, found so commonly in mineral -veins, often leads to a similar conclusion. Thus, from a specimen of -chalcedony, including in it a piece of calcareous spar, Dr Hutton -has derived a very ingenious and satisfactory proof, that these two -substances were perfectly soft at the same time, and mutually affected -each other at the moment of their concretion.<a id="FNanchor_116" href="#Footnote_116" class="fnanchor">[116]</a></p> - -<div class="footnote"> - -<p><a id="Footnote_116" href="#FNanchor_116" class="label">[116]</a> Theory of the Earth, vol. i. p. 93.</p> - -</div> - -<p>Each of these substances has its peculiar form, which, when left to -itself, it naturally assumes; the spar taking the form of rhombic -crystals, and the chalcedony affecting a mammalated structure, or a -superficies composed of spherical segments, contiguous to one another. -Now, in the specimen under consideration, the spar is included in the -chalcedony, and the peculiar figure of each is impressed on the other; -the angles and planes of the spar are indented into the chalcedony, -<span class="pagenum" id="Page_247">- 247 -</span> -and the spherical segments of the chalcedony are imprinted on the -planes of the spar. These appearances are consistent with no notion of -consolidation that does not involve in it the simultaneous concretion -of the whole mass; and such concretion cannot arise from precipitation -from a solvent, but only from the congelation of a melted body. This -argument, it must be remarked, is not grounded on a solitary specimen, -(though if it were it might still be perfectly conclusive,) but on a -phenomenon of which there are innumerable instances.</p> - -<p>221. According to this theory, veins were filled by the injection of -fluid matter from below; and this account of them, which agrees so -well with the phenomena already described, is confirmed by this, that -nothing of the substances which fill the veins is to be found any where -at the surface. It is not with the veins as with the strata, where, in -the loose sand on the shore, and in the shells and corals accumulated -at the bottom of the sea, we perceive the same materials of which these -strata are composed. The same does not equally hold of metallic veins: -"Look," says Dr Huston, "into the sources of our mineral treasures? Ask -the miner from whence has come the metal in his veins? Not from the -earth or air above, not from the strata which the vein traverses: these -do not contain an atom -<span class="pagenum" id="Page_248">- 248 -</span> -of the minerals now considered. There is but -one place from whence these minerals may have come; this is the bowels -of the earth; the place of power and expansion; the place from whence -has proceeded that intense heat, by which loose materials have been -consolidated into rocks, as well as that enormous force, by which the -regular strata have been broken and displaced."<a id="FNanchor_117" href="#Footnote_117" class="fnanchor">[117]</a></p> - -<div class="footnote"> - -<p><a id="Footnote_117" href="#FNanchor_117" class="label">[117]</a> Theory of the Earth, vol. i. p. 130.</p> - -</div> - -<p>222. The above is a very just and natural reflection; but if, instead -of interrogating the miner; we consult the Neptunist, we will receive -a very different reply. As this philosopher never embarrasses himself -about preserving a uniformity in the course of nature, he will tell -us, that though it may be true, that neither the air, the upper part -of the earth's surface, nor even the sea, contain at present any thing -like the materials of the veins, yet the time was when these materials -were all mingled together in the chaotic mass, and constituted one -vast fluid, encompassing the earth; from which fluid it was, that the -minerals were precipitated and deposited in the clefts and fissures of -the strata.</p> - -<p>223. It is alleged, in proof of this hypothesis, that mineral veins are -found to be less rich as they go farther down, whereas they ought to -be richer if they were filled by the projection of -<span class="pagenum" id="Page_249">- 249 -</span> -melted matter from -below. But the fact, that mines are less rich as they descend farther, -though it may hold in some instances, is not general, and may therefore -be supposed to arise from local causes, such as are, in respect of us, -accidental, and beyond the limits to which our theories can be expected -to reach. Thus the mines of Mexico and Peru are said to be subject -to the preceding rule; but in the mines of Derbyshire and Cornwall, -the very contrary is understood to take place. Besides, what we are -pleased to call the riches of a mine, are riches relatively to us, and -relatively to a distinction which nature does not recognise. The spars -and veinstones which are thrown out in the rubbish of our mines, may be -as precious in the eyes of nature, as conducive to the great objects -of her economy, and are certainly as characteristic of mineral veins, -as the ores of silver or gold, to which we attach so great a value. -Unless the former are in smaller quantity, or less highly crystallized -at great than at small depths, which I believe is not alleged, no -conclusion can be drawn from substances, which occupy in general but a -small proportion of any vein, and, in their dissemination through it, -do not seem to be always guided by the same law.</p> - -<p><a id="sec_224"></a>224. Again, if the veins were filled by deposition from above, we ought -to discover in them -<span class="pagenum" id="Page_250">- 250 -</span> -such horizontal stratification as is the effect of -deposition from water, and we should perceive no marks of the materials -having been introduced with violence into their place. The Neptunists -cannot object to the trial of their theory by these two frets.</p> - -<p>As to the first, it is acknowledged, that there is a certain regular -disposition of the substances in mineral veins, as stated <a href="#sec_59">§ 59</a>, but it -is one which has hardly any thing in common with the real phenomena -of stratification. It consists in the distribution of the principal -substances in coats parallel to the sides of the vein, each substance -forming a separate coat. In a vein, for instance, containing quartz, -fluor, calcareous spar, lead, &c. we might expect to find a lining of -quartz crystals, applied immediately to the walls of the mine, and -following exactly the irregularities of their surface; next, perhaps, -a coat of fluor, then of calcareous spar, and last of lead ore in the -centre of the vein, the same order being observed on the opposite -side. These successive coats, it is material to remark, are not in -planes, but in uneven surfaces, of which the inequalities are evidently -determined by those of the walls, that is, of the rock which forms -the sides of the vein; neither are they horizontal, but are parallel -to the walls, whether these be perpendicular or inclined. Here, -therefore, -<span class="pagenum" id="Page_251">- 251 -</span> -there is no appearance of the action of that statical law -which has directed the arrangement of the other strata, and which tends -to make the plane of every stratum deposited by water perpendicular -to the direction of gravity. The coating of the veins has therefore -been performed under the conduct of some other power than that which -presides over aqueous deposition. If, as the Neptunists maintain, the -materials in the veins were deposited by water, in the most perfect -tranquillity, it is wonderful that we do not find those materials -disposed in horizontal layers, across the vein, instead of being -parallel to its sides; and it seems very unaccountable, that the common -strata, deposited as we are told while the water was in a state of -great agitation, have so rigorously obeyed the laws of hydrostatics, (<a href="#sec_38">§ -38</a>.) and acquired a parallelism in the planes of their stratification, -which approaches so often to geometrical precision; while the materials -of the veins, in circumstances so much more favourable for doing the -same, have done nearly the reverse, and taken a position, often at -right angles to that which hydrostatical principles require. This is a -paradox which the Neptunian system has created, and which therefore it -is not very likely to resolve.</p> - -<p>225. Mere words should have little power to mislead, in a science which -treats of sensible objects, -<span class="pagenum" id="Page_252">- 252 -</span> -such as are always easily subjected to -the examination of sight or of touch; yet there is some appearance -as if the Neptunists were misled in this, and other instances, -by the term <i>stratification</i>. Though an incrustation on the -perpendicular face of a rock has very little affinity to a stratum, -such as we are accustomed to see deposited by water, yet the same name -being once imposed on both, mineralogists have proceeded to reason -concerning them, as if they were precisely the same thing, and were -both to be ascribed to the same cause. Indeed every perpendicular or -highly inclined bed of stone, is inexplicable as an effect of aqueous -deposition, in a system, unprovided, as the Neptunian is,<a id="FNanchor_118" href="#Footnote_118" class="fnanchor">[118]</a> with -the means of raising up such beds from a horizontal into a vertical -position. This observation may also be extended to all cases of -vertical stratification. Water cannot directly arrange its deposits -in planes highly inclined, and therefore I have often wondered to see -the Neptunists contending so eagerly for the stratification of certain -rocks, such as granite, which, being vertical, or highly inclined, -was much less friendly to their system than the entire absence of all -stratification would have been. I was disposed to admire their candour, -when the -<span class="pagenum" id="Page_253">- 253 -</span> -use which they made of the fact convinced me, that I ought -only to wonder at their inconsequential reasoning. The Huttonian Theory -is, indeed, the only one which possesses the means of reconciling the -elevation of the strata with their horizontal deposition, and which is -entitled to consider stratification, in whatever plane it may be, as -originally the work of the ocean. The geologists who attach themselves -exclusively to the action of water, will never be able to extend the -dominion of that element so far as Dr Hutton has done, by combining it -with fire.</p> - -<div class="footnote"> - -<p><a id="Footnote_118" href="#FNanchor_118" class="label">[118]</a> <a href="#sec_224">See preceding note.</a></p> - -</div> - -<p>226. But, though the Neptunian system were provided with engines, -powerful enough to raise up strata from a level to a vertical plane, -this would avail nothing in the present instance; since, on no -supposition, can the incrustations on the perpendicular sides of a -vein have ever been horizontal. On no supposition, therefore, can -these incrustations be received as a proof of aqueous deposition: it -may indeed be certainly inferred from them, that the matter which they -consist of was fluid at the time of their formation; but the absence of -all appearance of a horizontal disposition, in any part of the vein, -amounts nearly to a demonstration, that this fluidity did not proceed -from solution in a menstruum. We must therefore conceive the coats -to have been formed during the refrigeration of the -<span class="pagenum" id="Page_254">- 254 -</span> -melted matter -injected from the mineral regions into the clefts and fissures of the -strata. (<a href="#sec_59">§ 59.</a>)</p> - -<p>227. Mineral veins, particularly at their intersections with one -another, contain abundant marks of the most violent and repeated -disturbance (<a href="#sec_56">§ 56.</a>). Not to mention that they owe their first formation -to the fracture and displacing of rocks already consolidated, it -appears, that they have originated at very different periods, and -that the birth of each has been accompanied with convulsions, which -shook the foundations of the earth. In Cornwall, for instance, the -principal veins, and those which they distinguish particularly by the -name of <i>Lodes</i>, have nearly the same direction with the strata -or vertical schistus, extending from about E. N. E. to W. S. W. These, -however, are often intersected nearly at right angles by other mineral -veins, called <i>Cross Courses</i>, and this hardly ever happens -without the latter moving, or, as it is called, heaving the former out -of their direction. This plainly indicates, that the cross courses -are of later origin than the others, and that their formation was -accompanied with such a force, as must, in many substances, have moved -the whole body of rock which constitutes the promontory of Cornwall, -and probably much more, for several yards, in a horizontal direction. -Sometimes, also, both the longitudinal -<span class="pagenum" id="Page_255">- 255 -</span> -and the cross vein are forced -out of their place by a third. These disturbances arise not only from -mineral veins, but from veins of porphyry and granite, the production -of which has been attended with no less violence than of the others.</p> - -<p>228. What is here said of Cornwall, is the history, in some degree, of -all mineral countries whatever. The great horizontal <i>translation</i> -which has thus accompanied the formation of veins; the movement -impressed on such vast bodies of rock, and the frequent renewal of -these immense convulsions; are not to be explained by the mild and -tranquil dominion of the watery element. They require the utmost power -that is known any where to exist, and were it not for the admonitions -of the volcano and the earthquake, we might doubt if even subterraneous -heat itself possessed an energy adequate to these astonishing effects.</p> - -<p>229. From the <i>heaving</i> of one vein by another, it is evident, -that there was a force of protrusion in the direction of one of them, -that acted at the time of its formation. This force cannot be accounted -for on the supposition that veins were produced by the mere shrinking -of the strata; for the rocks could not, in that case, have been rent -asunder, and impelled forward at the same time. It appears most likely, -that fissures -<span class="pagenum" id="Page_256">- 256 -</span> -in the strata were made, at least in many instances, -and the matter poured into them, nearly at the same time, both being -effects of the same cause, the expansive force of subterraneous heat.</p> - -<p>230. It is remarked, at <a href="#sec_56">§ 56</a>, that the shifting of the strata is best -observed where the veins make a transverse section of beds of rock, -considerably inclined to the horizon. It is also true, that in some -cases the near approach of the strata to the level, may make the shifts -produced by the veins very easy to be discovered. Thus in Derbyshire, -where the mineral veins are in secondary strata, nearly horizontal, -there is almost no instance in which the corresponding strata are not -observed to be on different levels, on the opposite sides of the same -vein.</p> - -<p>231. The fact described by De Luc, and referred to at <a href="#sec_55">§ 55</a>, may, for -what we know of it, admit of being explained in two ways. The great -wedge of rock which appears to be insulated between two branches of the -same vein, may either be a mass that has been broken off, and sustained -by the melted matter that flowed all around it; or, it may be a mass -of rock contained between two veins that are in reality distinct, and -of different formation. Whether this last supposition is the truth, -would probably be evident from a careful examination of both -<span class="pagenum" id="Page_257">- 257 -</span> -parts of the vein; as some difference of character cannot fail to be the -consequence of different formation. If no such difference is observed, -the two branches must be supposed to belong to the same vein, and the -only probable explanation of the insulation of so large a mass of rock -will be by the first mentioned supposition. This fact, therefore, -notwithstanding the great attention M. De Luc has bestowed on it, -still requires further examination, before it can be decided whether -it inclines to the Huttonian Theory, as on the first supposition, or -is, as on the latter hypothesis, equally balanced between it and the -<i>Wernerian</i>.</p> - -<p>232. Whatever be the case with this fact, the general one of pieces of -rock being found insulated in veins, is certainly favourable to the -notion of an injected and ponderous fluid having originally sustained -them. Where, as happens in some instances, the stones contained in -the veins have no affinity to any of the rocks above, they cannot -be supposed to have come any how but from below, and to have been -carried up by the matter of the vein. The instance from the slip at the -Huddersfield Canal has been already mentioned.</p> - -<p>233. The preceding observations have been principally directed against -that theory of veins which supposes them to have been filled by -deposition -<span class="pagenum" id="Page_258">- 258 -</span> -from water. There is another theory maintained by some -of the Neptunists, that the metals in veins were introduced there by -infiltration.<a id="FNanchor_119" href="#Footnote_119" class="fnanchor">[119]</a> This opinion is sufficiently refuted by the fact, -that rarely any metallic ore is found out of the vein, or in the rock -on either side of it, and least of ail where the vein is richest. -This is inconsistent with the notion of the ore being carried into -the vein by water percolating through the adjacent rocks, unless some -satisfactory reason is assigned, which determined the water to leave -the ore in the vein and no where else. Besides, this hypothesis does -not account for the formation of the spars and veinstones which fill -the vein, and which appear clearly to have been brought there at the -same time with the ore, and no doubt by the same cause.</p> - -<div class="footnote"> - -<p><a id="Footnote_119" href="#FNanchor_119" class="label">[119]</a> Geol. Essays, p. 401.</p> - -</div> - -<p>234. The veins, properly so called, are indefinitely extended; but -there are also thin plates of spar, and of crystals of different -kinds, often found included in rocks, and shut in on all sides, -to which the name of veins is commonly applied. These last ought -certainly to be distinguished from the former, and may not improperly -be called <i>Plate Veins</i> or <i>Lenticular Veins</i>, the plate or -cake of spar of which they consist having very often the form of a -lens, though, -<span class="pagenum" id="Page_259">- 259 -</span> -as may be supposed, considerably irregular. Either of -these terms being derived entirely from external characters, has the -advantage of involving nothing theoretical.</p> - -<p>The lenticular veins are certainly not formed like the usual mineral -veins, by injection, since they are shut in, on all sides, by the solid -rock. When they are found, therefore, in stratified rocks, such as -have not themselves been melted, we must conceive them to be composed -of materials more fusible than the surrounding rock, so that they -have been brought into fusion by a degree of heat which the rest of -the rock was able to resist, and, on cooling, have assumed a sparry -structure. When they are found in rocks, of which the whole has been -fluid, they must be considered as component parts of that mass, which, -by an elective attraction, have united with one another, and separated -themselves from the substances to which they had less affinity.</p> - -<p>The veins of this kind seem to be connected with those called in -Derbyshire <i>Pipe Veins</i>, in which the ores of metals are sometimes -found. The pipe veins, indeed, are not in all cases completely -insulated, but sometimes communicate with the veins properly called -mineral. I am too little acquainted, however, with their natural -history, to Be able to say with certainty to -<span class="pagenum" id="Page_260">- 260 -</span> -which of the two species -they ought to be referred.</p> - - -<hr class="chap x-ebookmaker-drop" /> - -<div class="chapter"> -<h2 class="nobreak" id="Note_xiv"><span class="smcap">Note xiv. § 75.</span></h2> -</div> - -<p class="caption3nb"><i>On Whinstone.</i></p> - - -<p>235. To the facts and reasonings given above, I shall, in this note, -add a few remarks, tending to show, that whinstone is not of volcanic, -nor of aqueous, but certainly of igneous origin.</p> - -<p>It is asserted, (<a href="#sec_62">§ 62,</a>) that carbonate of lime and zeolite are often -contained in whinstone, but never in lava, and that this circumstance -may sometimes serve to distinguish these stones from one another. -With respect to carbonate of lime, in particular, it seems evident, -that this substance cannot enter into the original composition of -any lava, because the same heat which melted the lava, would, where -there was no greater pressure than the weight of the atmosphere, expel -the carbonic acid and produce quicklime. Notwithstanding this, rocks -containing carbonate of lime, have often been considered as lavas, -into the pores and cavities of which, calcareous matter having been -carried by the infiltration of water, had crystallized into spar. -Thus <span class="smcap">Spallanzani</span>, -<span class="pagenum" id="Page_261">- 261 -</span> -in his account of the Euganean Hills, in -Lombardy, describes some of the rocks as abounding at their surface, -and even in their interior, with air-bubbles of various sizes, from -such as are hardly perceptible, to some that are half an inch in -diameter; and which, he says, are all of an oval figure, with their -longest diameters in the same direction. This he considers as a proof -that the rock is a genuine lava; for the air-bubbles prove the stone to -have had its fluidity from fire; and by their elongation in the same -direction they prove, that the mass when fluid was also in motion. -Spallanzani adds, that <i>many of these cavities are filled with -crystals of the carbonate of lime, an effect of the infiltration of -water</i>.<a id="FNanchor_120" href="#Footnote_120" class="fnanchor">[120]</a></p> - -<div class="footnote"> - -<p><a id="Footnote_120" href="#FNanchor_120" class="label">[120]</a> Voyages dans les deux Siciles, tom. iii. p. 157. Edit. -de Faujas de St Fond.</p> - -</div> - -<p>236. Though the argument here advanced for the igneous origin of the -rock may be admitted as conclusive, the introduction of calcareous -spar into it by infiltration must still be questioned. Lava, except -in a state of decay or decomposition, is not readily penetrated by -water; and, if it were, the filling of cavities with spar, by means -of the water percolating through them, would still be subject to many -difficulties, (§12.). Besides, whinstone rocks are frequently found -<span class="pagenum" id="Page_262">- 262 -</span> -so full of calcareous spar, or of zeolite, that they would become porous -to such a degree, if the cavities filled with these latter substances -were all empty, that they could hardly sustain their own weight, and -much less that of the great masses of rock incumbent on them. In such -cases, it is certain, that the crystallized substances were part of the -original composition of the rock. The truth is, that the infiltration -of the water is a mere gratuitous assumption, introduced for the -purpose of explaining the existence of carbonated lime in a stone which -had endured the action of intense heat: and this assumption ought of -course to be rejected, if the phenomenon can be explained by a theory, -that is in other respects conformable to nature. The spar, then, may be -considered as a proof, that the rocks in question are to be numbered -with those unerupted lavas which have flowed deep in the bowels of the -earth, and under a great compressing force. This is the more probable, -that the Euganean Hills, like some whinstone hills in our own country, -have, in certain places, a covering of slaty and calcareous strata -incumbent on them, even at their summits,<a id="FNanchor_121" href="#Footnote_121" class="fnanchor">[121]</a> so that the torrent -of melted stone, of which they are admitted to consist, cannot have -flowed from the mouth of a volcano. I do -<span class="pagenum" id="Page_263">- 263 -</span> -not mean to say, that there -are among these hills no vestiges of volcanic explosion. I am very -far from having <i>data</i> sufficient for drawing this conclusion; -but I believe it may be safely affirmed, that the bulk of them is no -more composed of volcanic lava, than the basaltes of Staffa, or of the -Giant's Causeway.</p> - -<div class="footnote"> - -<p><a id="Footnote_121" href="#FNanchor_121" class="label">[121]</a> Phil. Trans. 1775, p. 34.</p> - -</div> - -<p>237. But, besides the evidence deduced from calcareous spar and -zeolite, against the rocks containing them being real lava, there are -other marks, even less equivocal perhaps, that distinguish the lavas -which we suppose to have flowed in the mineral regions, from those -which have actually flowed on the surface. These are what we collect -from the disposition, the organization, or, as we may say, the physical -geography of whinstone countries, unlike, in so many respects, to that -of volcanic countries. The shape of whinstone hills; their large flat -terraces, rising one above another; their perpendicular faces, and the -correspondence of their heights even at considerable distances; have -nothing similar to them in the irregular torrents of volcanic lavas. -The phenomena of the former are also on a scale of magnitude very far -exceeding the latter, and clearly indicate, that though both have been -produced by fire, it has been by fire in very different circumstances, -and regulated by very different laws. The structure of the two kinds -of -<span class="pagenum" id="Page_264">- 264 -</span> -rock agrees, in many respects, and so does their chemical analysis; -but their disposition and arrangement are so dissimilar, that they -cannot be supposed to be of the same formation.</p> - -<p>238. This argument, I believe, was first stated by Mr Strange, in a -letter to Sir <span class="smcap">John Pringle</span>, published in the 65th volume of -the <i>Philosophical Transactions</i>.<a id="FNanchor_122" href="#Footnote_122" class="fnanchor">[122]</a> That intelligent observer, -after visiting the countries in Europe most remarkable either for -burning, or for what are accounted, extinguished volcanoes, and -examining them with a very discriminating eye, remained convinced, that -there are two distinct species of rock, which both owe their origin -to fire; but to fire acting in circumstances and situations extremely -different. The first is the common volcanic lava; the other, to which -he gives the name of a basaltine rock, comprehends such rocks as the -Giant's Causeway, the basaltes of the Vivarais, of the Euganean Hills, -&c. and differs in nothing from that which is called here by the name -of whinstone. Mr Strange conceived, that the one of these kinds of -stone could, no more than the other, be accounted the work of aqueous -deposition, but was led to the distinction just mentioned, by observing -the organization -<span class="pagenum" id="Page_265">- 265 -</span> -and arrangement in the rocks of the latter kind, and -comparing them with the disorder and ruin that every where mark the -footsteps of volcanic fire He does not pretend to determine the nature -of the fire to which the basaltine rocks owe their formation, nor the -circumstances in which it has acted: he is satisfied with the negative -conclusion, that it is not volcanic; and his paper affords a specimen -of what is perhaps rare in any of the sciences, and certainly most rare -of all in geology, viz. a philosophic induction carried just as far as -the facts will bear it out, and not a single step beyond that point.</p> - -<div class="footnote"> - -<p><a id="Footnote_122" href="#FNanchor_122" class="label">[122]</a> Account of Two Giants' Causeways in the Venetian State, -&c. by John Strange, Esq. Phil. Trans. vol. lxv. (1775,) p. 5, &c.</p> - -</div> - -<p>239. Several other hints contained in this paper are highly deserving -of notice; for we not only find in it the notion of a formation of -basaltic rocks, igneous though not volcanic, but also that of their -simultaneous crystallization,<a id="FNanchor_123" href="#Footnote_123" class="fnanchor">[123]</a> together with the suggestion, that -granite and basalt are of the same origin,<a id="FNanchor_124" href="#Footnote_124" class="fnanchor">[124]</a> These opinions had not, -I believe, occurred at that time to any mineralogist except Dr Hutton, -nor had they been communicated by him to any but a few of his most -intimate friends; so that Mr Strange has without doubt all the merit -of a first discoverer. Indeed, without the knowledge of -<span class="pagenum" id="Page_266">- 266 -</span> -the principle -of compression, such as it is laid down by Dr Hutton, it was hardly -possible for him to proceed further than he has done. He remarked -the unburnt limestone that lies on the tops of some of the Euganean -basaltes, and seems to have been aware of the great difficulty, which -it was reserved for the Huttonian Theory to overcome. His letter -contains also some excellent general remarks on the rocks of the -Vivarais and Velay, which he had visited, before FAUJAS DE ST FOND had -published his curious and elaborate description of these countries.</p> - -<div class="footnote"> - -<p><a id="Footnote_123" href="#FNanchor_123" class="label">[123]</a> Phil. Trans, <i>ubi supra</i>, p. 17.</p> - -<p><a id="Footnote_124" href="#FNanchor_124" class="label">[124]</a> <i>Ibid.</i> p. 36 and 37.</p> - -</div> - -<p>240. The cause of the peculiar structure which has just been observed -to distinguish whinstone from volcanic countries, is easily assigned -in the Huttonian Theory. According to that theory, the whinstone rocks -were formed, in the bowels of the earth, of melted matter poured into -the rents and openings of the strata. They were cast, therefore, -in those openings, as in a mould; and received the impression and -character of the rocks by which they were surrounded. Hence the tabular -masses of whinstone, which when soft have been interposed between -strata, and compressed by their weight, so as almost to have themselves -acquired the appearance of stratification. Hence the perpendicular -faces of the same rocks, produced by their being abutted when -<span class="pagenum" id="Page_267">- 267 -</span> -yet soft, against the abrupt sides of the strata. The rocks which formed -those moulds have, in many cases, entirely disappeared; in others, a -part still remains, surrounding, or even covering, the basaltes, as in -the Euganean Hills, in those of the Val di Noto in Sicily, the rocks -near Lisbon,<a id="FNanchor_125" href="#Footnote_125" class="fnanchor">[125]</a> and in different parts of Great Britain.</p> - -<div class="footnote"> - -<p><a id="Footnote_125" href="#FNanchor_125" class="label">[125]</a> Recherches sur les Volcans Eteints du Vivarais; Lettre du -Dolomieu, p. 443.</p> - -</div> - -<p>Above all, the veins of whinstone which intersect the strata, are the -completest proofs of the theory here given of these rocks, and the most -inconsistent, in all respects, with the hypothesis of their volcanic -origin.</p> - -<p>241. If these <i>criteria</i> are applied to what are called -extinguished volcanoes, I have no doubt that many which have been -reckoned of that number, will be found to derive their origin more -directly from the fire of the mineral regions. The basaltic rocks -of the Vivarais, I am well persuaded, belong to this class; and I -conclude that they do so, not only from the account of them given by -Mr Strange, but from the description of Faujas himself, who, though -under the influence of the opposite theory, seems very fair and -accurate in his description of phenomena. The most unequivocal mark -of real whinstone rock, and of a formation in the strictest -<span class="pagenum" id="Page_268">- 268 -</span> -sense mineral, is where veins of that kind of rock intersect the strata. Now, -in a letter to Buffon, on the streams of lava found in the interior -of certain calcareous rocks in the lower Vivarais, Faujas describes -what can be accounted nothing else but a vein or dike of whinstone, -accompanied with several of its most remarkable and characteristic -appearances: "Figurez-vous un courant de lave, de la nature du basalte -noir, dur et compacte, qui a percé à travers les masses calcaires, et -s'est fait jour dans quelques parties, paroissant et disparoissant -alternativement: Cette coulée de matière volcanique s'enfonce sous -une partie de la ville, bâtie sur le rocher; elle reparoit dans la -cave d'un maréchal, se cache et se montre encore de temps en temps en -descendant dans le vallon, &c. Ce qu'il y a d'admirable, c'est que la -lave forme deux branches bien extraordinaires, dont l'une s'éleve sur -la crête du rocher, tandis que l'autre coupe horizontalement de grands -bancs calcaires escarpés, qui sont à découvert, et bordent le chemin.</p> - -<p>"Quels efforts n'-a-t-il pas fallu pour forcer cette lave se prendre -une telle direction, et se percer cette suite de rochers calcaires? -Si cette longue coulée de lave avoit eu 200 ou 300 toises de largeur, -je ne serois pas surpris qu'un torrent de matière en fusion de ce -volume eut pu produire, des effets extraordinaires et violens; -<span class="pagenum" id="Page_269">- 269 -</span> -<i>mais -figurez-vous, Monsieur, que dans les endroits les plus larges, elle n'a -tout-au-plus qu'environ 12 ou 15 pieds; elle n'en a que 3 ou 4 dans -certaines parties</i>".<a id="FNanchor_126" href="#Footnote_126" class="fnanchor">[126]</a></p> - -<div class="footnote"> - -<p><a id="Footnote_126" href="#FNanchor_126" class="label">[126]</a> Volcains Eteints du Vivarais, p. 328, &c.</p> - -</div> - -<p>This narrow stream is to be traced across the strata for more than a -league and a half; and the whole appeared to Faujas so marvellous, -that he says he almost doubted the testimony of his senses. He would -have done much better, however, to have doubted the conclusions of his -theory; for it was by them that the phenomena before him were rendered -so mysterious and incredible. While he continued to regard what is -described above as a stream of melted lava, which had descended from -the top of one mountain, and climbed up the sides of the opposite, like -water in a conduit pipe, piercing occasionally through vast bodies of -solid rock, it is no wonder that he considered as marvellous what is -indeed physically impossible. Had his belief in the volcanic theory -permitted him to see in all this, not a superficial current, but one of -indefinite depth, he would have beheld the object divested, not of what -was curious and interesting, but of what was incredible or absurd, and -reduced to the same class of things with mineral veins. That it belongs -really to this class, and is no more than a vein or dike -<span class="pagenum" id="Page_270">- 270 -</span> -of whinstone, -intersecting the strata to an unknown depth, and most probably, like -other veins, communicating with the mineral regions, cannot be doubted -by any one who has studied the subject of basaltine rocks, through -any other medium than the volcanic theory. The ramifications which -run from it into the calcareous rock, contrived, Faujas says, just as -if on purpose to perplex mineralogists, is one of the well known and -characteristic appearances of basaltic veins.</p> - -<p>242. It can hardly be doubted, that the lava described by the same -author as heaving up a mass of granite,<a id="FNanchor_127" href="#Footnote_127" class="fnanchor">[127]</a> and including pieces of -it, is a rock of real whinstone. The same may be said of many others; -and, though I pretend not to affirm that there is nothing volcanic in -the Vivarais, I must say, that nothing decidedly volcanic appears in -the description of that country, but many things that are certainly of -a very different origin.</p> - -<div class="footnote"> - -<p><a id="Footnote_127" href="#FNanchor_127" class="label">[127]</a> Volcains Eteints du Vivarais, fol. p. 365, &c.</p> - -</div> - -<p>In the present state of geological science, a skilful mineralogist -could hardly employ himself better, than in traversing those ambiguous -countries, where so much has been ascribed to the ancient operation -of volcanic fire, and marking out what belongs either clearly to the -erupted -<span class="pagenum" id="Page_271">- 271 -</span> -or unerupted lavas, and what parts are of doubtful formation, -containing no mark by which they may be referred to the one of these -any more than the other. Such a work would contribute very materially -to illustrate the natural history of the earth.</p> - -<p>243. One of the most ingenious attempts to support the volcanic -theory, is the system of <i>submarine volcanoes</i>, imagined by the -celebrated mineralogist <span class="smcap">Dolomieu</span>. The phenomenon that led to -this hypothesis, was what he had observed in the hills near Lisbon, and -still more remarkably in those of the Val di Noto in Sicily, where the -basaltine rocks had regular strata incumbent on them, and in some cases -interposed or alternated with them.<a id="FNanchor_128" href="#Footnote_128" class="fnanchor">[128]</a> It seemed from this evident, -that the strata were of later formation than the stone on which they -rested; and as they must, on every supposition, be held to be deposited -by water, it was concluded, that the lava which they covered had been -thrown out by volcanoes at the bottom of the sea; that the strata had -afterwards been deposited on this lava; and that, in some cases, there -had been frequent -<span class="pagenum" id="Page_272">- 272 -</span> -alternations of these eruptions and depositions.<a id="FNanchor_129" href="#Footnote_129" class="fnanchor">[129]</a></p> - -<div class="footnote"> - -<p><a id="Footnote_128" href="#FNanchor_128" class="label">[128]</a> Mémoire de Deodate de Dolomieu, sur les Volcains -Eteints du Val di Noto, en Sicile. Journal de Phys. tom. xxv. (1784. -Septembre.) p. 191.</p> - -<p><a id="Footnote_129" href="#FNanchor_129" class="label">[129]</a> Near Vizini, in the Val di Noto, Dolomieu tells us, that -he counted eleven beds, alternately calcareous and volcanic, in the -perpendicular face of a hill, which at a distance appeared like a piece -of cloth, striped black and white; <i>ubi supra</i>. He has since made -similar observations in the Vicentine and in Tyrol. Journal de Phys. -tom. xxxvii. (1790), partie 2, p. 200.</p> - -</div> - -<p>244. Though this hypothesis does certainly deliver the system of -the Volcanists from one great difficulty, it is itself liable to -insurmountable objections. I shall just mention some of the principal.</p> - -<p>1. The regular and equidistant strata that we often see covering the -tops of whinstone or basaltic rocks, could not have been deposited in -the oblique and very much inclined position which they now occupy.</p> - -<p>This is remarkable in the strata which cover the basaltic rock of -Salisbury <i>Craig</i>, near Edinburgh, at its northern extremity. The -strata are very regular, and must have been deposited in a plane nearly -horizontal; yet the surface of the basaltes on which they now rest is -very much inclined, dipping rapidly to the north-east. The necessity of -a horizontal deposition in strata, which, though not now horizontal, -have their -<span class="pagenum" id="Page_273">- 273 -</span> -planes nearly parallel to one another, has been proved at § -38.</p> - -<p>2. If there is any truth in the principles established above, even the -strata themselves have not been consolidated without the action of -fire. By Dolomieu's system, therefore, the consolidation of the strata -which cover the basaltes is not accounted for.</p> - -<p>3. There are no means furnished by the hypothesis of submarine -volcanoes for bringing the basalt, and the strata which cover it, -above the level of the sea. If it is said that the waters of the sea -have been drained off, the objections are all incurred that have been -stated at <a href="#sec_37">§ 37</a>.<a id="FNanchor_130" href="#Footnote_130" class="fnanchor">[130]</a> If it is said, that the rocks themselves have been -elevated by a force, impelling them upwards, we say, that the existence -of such a force, when admitted, furnishes another means of explaining -the whole phenomenon, namely, that of the injection of melted matter -among the strata, the same that is used in the Huttonian Theory.</p> - -<div class="footnote"> - -<p><a id="Footnote_130" href="#FNanchor_130" class="label">[130]</a> Dolomieu adopts this supposition; he thinks, that the -surface of the sea must have been formerly 500 or 600 toises above its -present level. <i>Ibid.</i> p. 196.</p> - -</div> - -<p>4. The phenomena of basaltic veins are not in the least explained by -the hypothesis of submarine volcanoes. That hypothesis, then, even -if the foregoing objections were removed, does -<span class="pagenum" id="Page_274">- 274 -</span> -not serve to explain -all the facts respecting the rocks of this genus, and wants, of -consequence, one of the most important characters of a true theory. -It must be allowed, however, that it makes a considerable approach to -such a theory, and that the submarine volcanoes of Dolomieu, have an -affinity to the unerupted lavas of Dr Hutton.</p> - -<p>245. Though in these remarks I have endeavoured to expose the errors -of the volcanic system, I cannot but consider that system as coming -infinitely nearer to the truth than the Neptunian. It has the merit -of distinguishing an order of rocks, which bears no marks of aqueous -formation, and in which the crystallized, sparry, or lava-like -structure, bespeaks their primeval fluidity, and refers their origin -to fire. The Neptunian system, on the other hand, strives to confound -the most marked distinction in the mineral kingdom, and to explain -the formation, both of the stratified and unstratified rocks, by -the operation of the same element. Though chargeable with this -inconsistency, it has become the prevailing system of geology; and the -arguments which support it are therefore entitled to attention.</p> - -<p>246. It will no doubt be thought singular, that the same mineralogist, -whom we have just seen exerting his ingenuity in defence of the -<span class="pagenum" id="Page_275">- 275 -</span> -volcanic system, should now appear equally strenuous in defence of the -Neptunian. Though Dolomieu contends for the volcanic origin of some -basaltic rocks, he does not admit that all basaltes is volcanic, nor -even all of igneous formation. Thus he states, that he had examined at -Rome some of the most ancient monuments of art, executed in basaltes, -brought from Upper Egypt, and that he could discover no mark of the -action of fire in any of them.<a id="FNanchor_131" href="#Footnote_131" class="fnanchor">[131]</a></p> - -<div class="footnote"> - -<p><a id="Footnote_131" href="#FNanchor_131" class="label">[131]</a> Journal de Physique, tome xxxvii. (1790,) partie 2, p. -193.</p> - -</div> - -<p>On the contrary, he found that some of them consisted of green -basaltes, which changes its colour to a bronze, when exposed even to a -moderate heat, and which therefore, he argues, can never have endured -any strong action of fire.</p> - -<p>The answer to this argument is very plain, if we admit the effects -ascribed by Dr Hutton to the compression which necessarily takes place -in the mineral regions. If indeed the heat in those regions resembled -exactly that of our fires at the surface, it would not be easy to deny -the above conclusion, which therefore certainly holds good against -the volcanic origin of the Egyptian basaltes. But there is no reason -why, under strong compression, the colouring matter -<span class="pagenum" id="Page_276">- 276 -</span> -of these stones -might not be fixed, and indestructible by heat, though it can be easily -volatilized or consumed when such compression is removed. This argument -then is against the volcanic; but not against what has been called the -<i>Plutonic</i> formation of basaltes.</p> - -<p>247. As to the other marks of fire which Dolomieu sought for and did -not find in the above mentioned stones, we are not exactly informed -in what they consisted. If the crystallized or spathose texture that -belongs to this description of stones was wanting, the specimens were -not to be considered as of the real basaltic or whinstone genus, -whatever their name or history may seem to indicate. If they did -possess that texture, they had the only mark of an igneous origin that -could be expected, supposing that origin to have been in the bowels of -the earth. No part, therefore, of the observations of this ingenious -mineralogist, can be considered as inconsistent with the theory of -basaltic rocks which has been laid down above.</p> - -<p>248. Bergman had before reasoned on this subject precisely in the same -manner, but from better data, as the stones from which he derived -his argument were in their native place: "Trap," says that ingenious -author, (that is whinstone,) "is found in the stratified mountains -of West Gothland, in a way that deserves -<span class="pagenum" id="Page_277">- 277 -</span> -to be described. The lower -stratum, which is several Swedish miles in circuit, (10½ of these -miles make a degree,) is an arenaceous stone, horizontal, resting on -granite, and having its particles agglutinated by clay. The stratum -above this is calcareous, full of the petrifactions of marine animals, -and above this is the trap. These three kinds of rock compose the -greater part of the mountains just mentioned, though there are some -other beds, particularly very thin beds of marl and of clay, which -separate the middle stratum, both from that which is under it and -over it, and are frequently so penetrated with bitumen that they -burn in the fire. This schistus is black; when burnt it becomes red, -and afterwards, when washed with water, affords alum. How can it be -supposed," he adds, "that the trap has ever been violently heated, -while the shistus on which it is incumbent retains its blackness, which -however it loses by the action even of a very weak fire?"<a id="FNanchor_132" href="#Footnote_132" class="fnanchor">[132]</a></p> - -<div class="footnote"> - -<p><a id="Footnote_132" href="#FNanchor_132" class="label">[132]</a> Bergman de Productis Volcaniis, Opuscula, tom. iii. p. -214, &c.</p> - -</div> - -<p>The answer to this argument is already given. The reasoning, as -in the former instance, is conclusive only against the action of -volcanic fire, or fire at the surface; but not against the action of -heat deep in the bowels of the earth, and under -<span class="pagenum" id="Page_278">- 278 -</span> -the pressure of the -superincumbent ocean. In such a situation, the bituminous schistus -might be in contact with the melted basalt, and yet there might be no -evaporation of the volatile, nor combustion of the inflammable parts. -It does not, however, always happen, that the bituminous substances, or -substances alterable by fire, which are found in contact with basaltes, -are without any mark of having endured the operation of fire. Instances -in which such operation is apparent are given above, <a href="#sec_30">§ 30</a>; and more -will be added in the conclusion of this note.</p> - -<p>249. The same mineralogist founds another argument for the aqueous -formation of whin or trap on the existence of that stone in the form -of veins, included in primeval rocks: "Invenitur hoc saxum (trap) in -Suecia pluribus locis, sæpeque in montibus primævis, angustas implens -venas, adeo subtilis structuræ, ut particulæ sint impalpabiles, et, dum -niger est, genuinum efficit lapidem Lydium. In hisce montibus, nulla -adsunt ignis subterranei vestigia."<a id="FNanchor_133" href="#Footnote_133" class="fnanchor">[133]</a></p> - -<div class="footnote"> - -<p><a id="Footnote_133" href="#FNanchor_133" class="label">[133]</a> Opuscula, <i>ubi supra</i>.</p> - -</div> - -<p>The phenomena here described, namely, a vein of compact whinstone -traversing a primary rock, is, without doubt, as incapable of being -explained by the operation of a volcano, as it is -<span class="pagenum" id="Page_279">- 279 -</span> -by that of aqueous -deposition. It is, however, a most complete proof of the original -softness of the substance of which the veins consist, and affords one -of the strongest possible arguments for such an operation of fire as is -supposed in the present theory. The main arguments, therefore, which -have been proposed as subversive of the igneous origin of basaltes, are -only subversive of their formation by one modification of fire, viz. -of fire acting near the surface; and thus the weapons which directly -pierce the armour of the Volcanist, and inflict a mortal wound, are -easily turned aside by the superior temper of the <i>Plutonic</i> mail.</p> - -<p>250. An argument founded on facts very similar to some of the -preceding, and leading to the same conclusion, is employed by the -mineralogist to whom the Neptunian system owes its chief support. -Werner, in his observations on volcanic rocks and on basaltes, has -rested his proof of the aqueous formation of the latter, on their -interposition between beds of stone in mountains regularly stratified, -and obviously formed by water. He describes an instance of this in -the basaltic hill of <i>Scheibenberg</i>; and the facts, though most -of them are not uncommon, are highly deserving of attention. Near the -top of this hill, and above the basaltic rock which composes the body -of it, he tells us, that -<span class="pagenum" id="Page_280">- 280 -</span> -there was a sand-pit; a circumstance which -he appears to consider as not a little singular. It was, however, at -the bottom of the hill, that he met with the appearances which chiefly -attracted his notice: "First," says he; "or lowest, was a thick bank of -quartzy sand, above that a bed of clay, then a bed of the argillaceous -stone called wacke; and upon this last rested the basaltes." "When I -saw," adds he, "the three first beds running almost horizontally under -the basaltes, and forming its base; the sand becoming finer above, then -argillaceous, and at last changing into real clay, as the argil was -converted into wacke in the superior part; and, lastly, the wacke into -basaltes; in a word, when I found a perfect transition from pure sand -to argillaceous sand, from the latter to a sandy clay, and from this -sandy clay, through many gradations, to a fat clay, to wacke, and at -last basaltes, I was irresistibly led to conclude, that the basaltes, -the wacke, the clay, and the sand, are all of one and the same -formation; and that they are all the effect of a chemical precipitation -during one and the same submersion of this country."<a id="FNanchor_134" href="#Footnote_134" class="fnanchor">[134]</a></p> - -<div class="footnote"> - -<p><a id="Footnote_134" href="#FNanchor_134" class="label">[134]</a> "Combien je fus surpris de voir en arrivant au -fond, un epais <i>banc de sable quartzeux</i>, puis au-dessus une -<i>couche d'argile</i>, enfin une couche de la pierre argileuse -nommée <i>Wacke</i>, et sur celle-ci reposer le <i>basalte</i>. -Quand je vis les trois premiéres couches s'enfoncer <i>presqu' -horizontalement sous le basalte</i>, et former ainsi sa <i>base</i>; -le sable devenir plus fin au-dessus, puis argileux, et se changer -enfin en vraie argile, comme l'argile se convertissoit en wacke dans -sa partie supérieure; et finalement la wacke en basalte; en un mot, -de trouver ici une <i>transition parfaite</i> du <i>sable pur</i> au -<i>sable argileux</i>, de celui-ci à <i>l'argile sablonneuse</i>, et -de <i>l'argile sablonneuse</i>, par plusieurs gradations, à l'argile -<i>grasse</i>, à la <i>wacke</i> et enfin au <i>basalte</i>.</p> - -<p>"A cette vue, je fus sur le champ et irrésistiblement entrainé à -penser, (comme l'auroit été sans doute tout connoisseur impartial -frappé des conséquences de ce phénomène;) je fus, dis je, -irrésistiblement entrainé aux id es suivantes: Ce <i>basalte</i>, cette -<i>wacke</i>, cette <i>argile</i>, et ce <i>sable, sont d'une seule -et même formation</i>; ils sont tous l'effet d'une <i>precipitation -par voie humide</i> dans une seule et même submersion de cette -contrée; les eaux qui la couvroient alors transportoient d'abord -le <i>sable</i>, puis deposoient l'<i>argile</i>, et changoient -peu-à-peu leur précipitation en <i>wacke</i>, et enfin en vraie -<i>basalte</i>.—Journal de Physique, tom. xxxviii. (1791,) Partie i. -p. 415.</p> - -</div> - -<p><span class="pagenum" id="Page_281">- 281 -</span></p> - -<p>First, as to the sand on the top of this basaltic hill, it is most -probably the remains of certain sandstone strata that originally -covered the basaltic part, but are now worn away. We are therefore to -consider this as an instance of a basaltic rock, interposed between -strata that are undoubtedly of marine origin. In this, however, there -is nothing inconsistent with Dr Hutton's theory of basaltes; on the -contrary, it is -<span class="pagenum" id="Page_282">- 282 -</span> -one of the principal facts on which that theory is -founded. It has indeed been argued by some mineralogists, that bodies -thus contiguous must owe their origin to the same element, and that -a mineral substance cannot be of more recent formation than that -which lies above it. But the maxim, that a fossil must have the same -origin with those that surround it, does not hold, unless they have a -certain similarity of structure. It is, for instance, the want of this -similarity, that authorizes us to assign different periods of formation -to mineral veins, and to the rocks in which they are included.</p> - -<p>In a succession of strata, no one can doubt, that the lowest were the -first formed, and the others in the order in which they lie; but, when -between two strata of sandstone or of limestone we find an intermediate -rock, so different as to resemble lava, and to have nothing schistose -or stratified in its composition, the same instrument cannot be -supposed to have been employed in the formation of both; nor is there -any reason why we may not suppose, that the intermediate body was -interposed between the other two, by some action subsequent to their -formation. It was thus that Dolomieu concluded, when he saw a lava-like -stone interposed between calcareous strata in the Val di Noto, that, -though -<span class="pagenum" id="Page_283">- 283 -</span> -contiguous, these two rocks could not possibly be of the same -formation; and thus far it is certain, that every unprejudiced observer -must agree with him.</p> - -<p>251. But the circumstance on which Werner seems to lay the greatest -stress, is the gradual transition from the sand to the basalt, through -the intermediate steps of clay and wacke; this gradual transition he -considers as a direct proof, that they are all of the same formation.</p> - -<p>A gradual transition of one body into another, can only be said to -take place, when it is impossible to define their common boundary, or -to determine the line where the one begins and the other ends. Now, -if this be the proper notion of gradual transition, I must say, that -after much careful examination, I have never seen an instance, in which -such a transition takes place between whinstone and the contiguous -strata. The <i>line</i> of separation, though in some places less -evident than in others, has, on the whole, been marked out with great -precision; and, though the stones have been firmly united, or, as -one may say, welded one upon another, yet, when a fresh fracture was -obtained, the stratified and unstratified parts have rarely failed to -be distinguished. The fresh fracture is indeed often necessary, for -many species of whinstone -<span class="pagenum" id="Page_284">- 284 -</span> -get by decomposition a granulated texture at -the surface, so as hardly to be distinguished from real sandstone.</p> - -<p>Some of the kinds of primary schistus also, particularly the -argillaceous, when much indurated, have in their structure a -considerable resemblance to whinstone; they are slightly granular, or -laminated, and have a tendency to a sparry texture. Where it happens -that this sort of schistus and whinstone are contiguous, it is natural -to expect, that their common boundary will be traced with difficulty, -and in many parts will be quite uncertain. Still, however, if a careful -examination is made; if the effects of accidental causes are removed; -and, above all, if the more ambiguous instances are compared with the -more decisive, and interpreted by them, though single specimens may be -doubtful, we will hardly ever find that any uncertainty remains with -respect to entire rocks.</p> - -<p>252. This general fact, which I state on much better authority than -that of my own observations, viz. on those of Dr Hutton, is not given -as absolutely without exception. The theory of whinstone which has -been laid down here, leads us indeed to look for some such exceptions. -It is certain, that the basis of whinstone, or the material out of -which it is prepared by the action -<span class="pagenum" id="Page_285">- 285 -</span> -of subterraneous heat, is clay in -some state or other, and probably in that of argillaceous schistus. -It follows, of consequence, that argillaceous schistus may by heat be -converted into whinstone, or the material out of which is prepared by -the action of subterraneous heat, is clay in some state or other, and -probably in that of argillaceous schistus. It follows, of consequence, -that argillaceous schistus may by heat be converted into whinstone. -When, therefore, melted whinstone has been poured over a rock of such -shistus, it may, by its heat, have converted a part of that rock into -a stone similar to itself; and thus may now seem to be united, by -an insensible gradation, with the stratum on which it is incumbent; -and phenomena of this kind may be expected to have really happened, -though but rarely, as a particular combination of circumstances seems -necessary to produce them. Hence it is evident, that stones may -graduate into one another, without being of the same formation; and -that it is fallacious to conclude, from the insensible transition -of one kind of rock into another, without any other circumstance of -affinity, that they have both the same origin.</p> - -<p>I am disposed, therefore, to make some limitation to what is said -in <a href="#sec_72">§ 72</a>, where I have expressed an absolute incredulity as to such -transitions as are here referred to. The great skill and experience -of the mineralogist who has described the strata at Scheibenberg, do -not allow us to doubt of his exactness, though some of the appearances -are such as decomposition and wearing might well enough be supposed to -produce. -<span class="pagenum" id="Page_286">- 286 -</span> -The fairest way is to take Mr Werner's observations just as -they are given us, and to try whether they cannot be explained without -the assistance of his theory. In effect, the wacken which he describes, -rests, it would seem, on an unconsolidated bed of clay; and it may be -supposed, that a part of this bed has been converted into wacken by -the heat of the incumbent mass, and has thus produced the apparent -gradation from the one substance to the other. As the appearances of -the rocks of Scheibenberg seem to be considered by Werner as furnishing -a very strong, and even an unexpected confirmation of his system, I -cannot help thinking, that an explanation of them, on the principles -of Dr Hutton, without any straining or forcing of those principles, -contributes not a little toward extending the empire of the latter over -all the phenomena of geology.</p> - -<p>253. Another fact, which has been much infilled on of late, in proof -of the aqueous formation of basaltic rocks, is that shells are found -in them. Of the reality of this fact, however, or at least of the -instances hitherto produced, great doubts I think may be reasonably -entertained. The specimens of the supposed basaltes, with shells -included in them, that are chiefly relied on, are found at Portrush in -Ireland, a rocky promontory to the westward of the Giant's Causeway, -and separated from it by a -<span class="pagenum" id="Page_287">- 287 -</span> -considerable body of calcareous strata. -Some of these specimens were brought to Edinburgh about a year ago, -and were supposed, I believe, to contain an irrefragable proof of the -Neptunian origin of the basaltic promontory where they were found. I -went to see these specimens in company with Lord Webb Seymour and Sir -James Hall; and, on examining them carefully, we were all of opinion, -that the stones which contained the shells, or the impressions of the -shells, were no part of the real basaltes. They were all very compact, -and had all more or less of a siliceous appearance, such as that of -chert; they had nothing of a sparry or crystallized structure; their -fracture was conchoidal, and but slightly uneven. In two of them, one -of which bore the impression of a <i>cornu ammonis</i>, the schistose -texture might be distinctly perceived. A specimen which accompanied -them, but in which there was no shell, served very exactly to explain -the relation between these stones and the true basaltes. Part of this -specimen was a true basalt, and the rest a sort of hornstone, exactly -the same with that in which the shells were, and not unlike the jasper -that is under the whinstone of Salisbury Crag, and in contact with -it; so that on the whole it was evident, that the rock containing the -shells is the schistus or stratified stone, which serves as the base of -the basaltes, -<span class="pagenum" id="Page_288">- 288 -</span> -and which has acquired a high degree of induration, by -the vicinity of the great ignited mass of whinstone.</p> - -<p>This solution of the difficulty has since been confirmed by -observations made on the spot by Dr Hope, who discovered two or three -alternations of the basaltic rock, with the beds of the schistus in -which the shells are contained.</p> - -<p>254. This also explains some observations of Spallanzani, made in -the island of Cerigo, on the coast of Greece, the Cythæra of the -ancients.<a id="FNanchor_135" href="#Footnote_135" class="fnanchor">[135]</a> The base of that island is limestone; but it abounds -also in unstratified rocks, which the Italian naturalist supposes to -be of volcanic origin; but which, if I mistake not, we would regard -as whinstone, or perhaps porphyry; and they are said to contain -oyster-shells and pectinites of a large size, perfectly mineralized. -These petrifactions, however, Spallanzani says, are not contained -in the lava that has actually flowed, but in stones which have only -endured a slighter action of fire. Without the commentary afforded by -the Portrush specimens, it would be difficult to make out any thing -very precise from this description. By help of the information derived -from those specimens, we may conclude, that the condition of the -shells -<span class="pagenum" id="Page_289">- 289 -</span> -in them, and in the rocks of Cerigo, is perfectly alike; and -that, in both cases, the shells are involved in parts of the rock which -are truly stratified, but which have been, in some degree, assimilated -to the basaltes by the heat which they have endured. Spallanzani would -probably have used exactly the same terms which he employs in speaking -of Cerigo, if he had been required to describe the petrified shells at -Portrush.</p> - -<div class="footnote"> - -<p><a id="Footnote_135" href="#FNanchor_135" class="label">[135]</a> Journal de physique, tom. xlviii. (1798,) p. 278.</p> - -</div> - -<p>255. In the instances just mentioned, the petrified marine objects are -not found in the real whinstone; but if they were found in it, when it -borders on stratified rocks containing such objects, the thing would -not be at all surprising, nor furnish any argument against the igneous -consolidation of the stone. If a torrent of melted matter was poured -in among the strata, by a force which at the same time broke up and -disordered those strata, nothing could be more natural, than that this -matter should contain fragments of them, and of the objects peculiar to -them.</p> - -<p>In one instance, mentioned by Mr Strange, this seems actually to have -taken place. In the Veronese, a country remarkable for a mixture of -limestone strata, containing marine objects, with volcanic or basaltine -hills, he assures us, that he had seen a mass of stone, which had -<span class="pagenum" id="Page_290">- 290 -</span> -evidently concreted from fusion, in which the marine fossil bodies, -originally, as he supposes, contained in the strata, were perfectly -distinguishable, though variously disfigured.<a id="FNanchor_136" href="#Footnote_136" class="fnanchor">[136]</a> It may be, that -in this, as in the foregoing examples, it was not real basaltes, or -real lava, which contained the shells, but the conterminal rock; but, -supposing it to be as Mr Strange represents it, there appears to be -no inconsistency between the phenomenon, and the igneous origin of -the rock in which the shells were included. Here, however, it should -be remarked, that the presence of great pressure, to prevent the -conversion of the shells into quicklime, seems absolutely necessary; -and that the phenomenon of these basaltic petrifactions, requires the -application of heat to have been deep under the surface of the earth.</p> - -<div class="footnote"> - -<p><a id="Footnote_136" href="#FNanchor_136" class="label">[136]</a> Phil. Trans. 1775, p. 25.</p> - -</div> - -<p>256. The phenomena we have been considering, have been selected as the -most unfavourable to the igneous origin of basaltic rocks; and we have -seen, that when duly examined, they are not at all inconsistent with -it. We are now to take a view of some appearances, that seem quite -irreconcilable with the aqueous formation of these rocks.</p> - -<p><span class="pagenum" id="Page_291">- 291 -</span></p> - -<p>Where whinstone rocks are found in masses, bounded by the strata, -and insulated among them, they subject the Neptunian system to great -difficulties. For, supposing it true that this stone may be produced by -the precipitation and crystallization of mineral substances dissolved -in water, yet it seems unaccountable, that this effect has been so -local and limited in extent, as often to be confined to an irregular -figure of a few acres, while, all round, the substances deposited -have had no tendency to crystallization, and have been formed into -the common secondary strata. The rock of Salisbury <i>Craig</i>, for -instance, is a mass of whinstone, having a perpendicular face eighty -or ninety feet high toward the west, and extending from north to south -with a circular sweep about 900 yards. The whole of this rock rests on -regular beds of secondary sandstone, not horizontal, but considerably -depressed toward the north-east: the rock is loftiest in the middle, -and decreases in thickness toward each end, terminating at its northern -extremity in a kind of wedge. It is covered at top, toward that -extremity, with regular beds of sandstone, perfectly similar to those -on which it is incumbent; and it is not improbable, that this covering -formerly extended over the whole.</p> - -<p><span class="pagenum" id="Page_292">- 292 -</span></p> - -<p>Now, what cause can have determined the column of water, which rested -on the base at present occupied by this rock, to deposit nothing but -the materials of whinstone, while the water on the south, west, and -north, was depositing the materials of arenaceous and marly strata? -Wherefore, within this small space, was the precipitate every where -<i>chemical</i>, to use the language of Werner, while close to it, on -either side, it was entirely <i>mechanical?</i> Why is there, in this -case, no gradation? and why is a mere mathematical line the boundary -between regions where such different laws have prevailed? Whence -also, we may ask, has the basaltic deposit been abruptly terminated -toward the west, so as to produce the steep face which has just been -mentioned? The operation of currents, or of any motion that can take -place in a fluid, will furnish no explanation whatever of these -phenomena; yet they are phenomena far from being peculiar to a single -hill; they are among the most general and characteristic appearances -in the natural history of whinstone mountains; and a geological -theory which does not account for them, is hardly entitled to any -consideration.</p> - -<p>257. The basaltic rock, just described, is also covered, at least -partly, with strata perfectly similar -<span class="pagenum" id="Page_293">- 293 -</span> -to those that lie under it. -Now, it appears altogether unaccountable, that after the water had -done depositing the materials of the whin on the spot in question, -the former order was so quickly resumed, and a deposition of sand, -and of the other materials of the strata, took place just as before. -All this is quite unintelligible; and the principles of the Neptunian -system seem here to stand as much in need of explanation, as any of the -appearances which they are intended to account for.</p> - -<p>258. The unequal thickness, and great irregularity in the surface -of the whinstone mass, here treated of, and of many rocks of the -same kind, is also a great objection to the notion of their aqueous -formation. This seems to have been perceived by Werner, in the instance -of the rocks formerly mentioned; and he endeavours to explain it, by -supposing, that much of these rocks has been destroyed by waste and -decomposition, so that an irregularity of their surface, and want of -correspondence has been given to them, which they did not originally -possess. In the instance of Salisbury <i>Craig</i>, however, we have a -proof, that the great irregularity of surface, and the inequality of -thickness, do not always arise from these causes. The thinnest part -of that rock, toward its northern extremity, is -<span class="pagenum" id="Page_294">- 294 -</span> -still covered by the -strata in their natural place, and has been perfectly defended by them -from every sort of wearing and decay. The cuneiform shape, therefore, -which this rock takes at its extremities, and the great difference of -its thickness at them and in the middle, is a part of its original -constitution, and can be attributed to nothing casual, or subsequent to -its consolidation.</p> - -<p>The same may be said of many other basaltic rocks, where an inequality -of thickness, most unlike to what belongs to aqueous deposits, is known -to exist in beds of whinstone that are still deep under the surface. -Thus the toadstone of Derbyshire, even where it has a thick covering of -strata over it, has been found, by the sinking of perpendicular shafts, -to vary from the thickness of eighteen yards to more than sixty, within -the horizontal distance of less than a furlong. Nothing of this kind -is ever found to take place in those beds of rock which are certainly -known to originate from aqueous deposition, and no character can more -strongly mark an essential difference of formation.</p> - -<p>259. We have had frequent occasion to consider the characters of -those masses of whinstone which are so often found interposed between -stratified rocks. These have been found in general very adverse to the -Neptunian system; and -<span class="pagenum" id="Page_295">- 295 -</span> -two of them which yet remain to be mentioned, -are even more so than any of the rest.</p> - -<p>Where a bed or tabular mass of whinstone is interposed between strata, -and wherever an opportunity offers of seeing its termination, if the -strata under it are not broken, it may be remarked, that they do not -abut themselves bluff and abrupt against the whin. On the contrary, -if we mark the course of the stratum which covers the whinstone, and -of that which is the base of it, we shall find they converge toward -one another, the interposed mass growing thinner and thinner, like a -wedge. When the latter terminates, the two former come in contact, and -have no stratum interposed between them. Thus the roof and base of the -whinstone rock are contiguous beds, that appear as if they had been -lifted up and bent, and separated by an interposed mass. Had the whole -been an effect of simultaneous deposition, the regular strata must have -been abruptly terminated by the whin, like two courses of different -forts of masonry where they meet with one another.</p> - -<p>260. From this wedge-form of the whinstone masses, and in general from -the irregularity of their surfaces, another conclusion follows, similar -to the preceding, and one which has been already mentioned. Where the -surface of the interposed -<span class="pagenum" id="Page_296">- 296 -</span> -mass is greatly inclined to the horizon, the -strata which rest on this inclined plane, are nevertheless as exactly -parallel to that plane, and to one another, as if they were really -horizontal. It is certain, therefore, that they were not deposited on -the same inclined plane on which they now rest; for, if so, they would -have been still nearly horizontal, and by no means parallel to the -inclined side of the whinstone. This follows from the nature of aqueous -deposition, as already explained.</p> - -<p>We have a remarkable instance of the phenomenon here referred to, -in the rock of Salisbury <i>Craig</i>, of which mention has been so -often made, and in which almost every circumstance is united, that can -serve to elucidate the natural history of basaltic rocks. The north -end of that rock is in the figure of a wedge, with its inclined side -considerably steep, and covered by strata of grit, perfectly regular, -and parallel to the surface on which they lie. The inspection of them -will convince any one, that they were not deposited by the water, -on a bottom so highly inclined as that on which they now rest. They -are of a structure very schistose; their layers very thin; so that -any inaccuracy of their parallelism would be readily observed. The -appearances of the horizontal deposition of these strata, are indeed -so clear, and so impossible -<span class="pagenum" id="Page_297">- 297 -</span> -to be misunderstood, that the followers -of the Huttonian system would not risk much, if they were to leave the -whole theory of whinstone to the decision of this single fact, and -should agree to abandon that theory altogether, if the Neptunists can -shew any physical or statical principle, on which the deposition now -described can possibly have been made; or will point out the rule, by -which nature has given a structure so nicely stratified to arenaceous -beds deposited on a surface so highly inclined. If no such principle -can be pointed out, though we cannot conclude that the Huttonian Theory -is true, we certainly may conclude that the Neptunian is false.</p> - -<p>261. Proofs of the igneous formation of whinstone, still more direct, -are derived from the induration of the contiguous strata; from their -disturbance when interfered by veins of whinstone; and from the -charring of the coal which happens to be in contact with these veins. -These are considered above at § <a href="#sec_66">66</a>, <a href="#sec_67">67</a>, &c.; and it is particularly -taken notice of at <a href="#sec_66">§ 66</a>, that pieces of sandstone are sometimes found -as if floating in the whinstone, and, at the same time, greatly altered -in their texture. One of the best and most unequivocal instances of -this sort which I have seen, is to be found on the south side of -<i>Arthur's Seat</i>, near Edinburgh. The rock -<span class="pagenum" id="Page_298">- 298 -</span> -which composes the -upper part of the hill, on that side, is a whinstone breccia, such as -we have many examples of, and, I believe, very much resembling what is -called a <i>lava brecciata</i> by the volcanic geologists. The stony fragments -included in this compound mass, are for the greater part rounded; -and some of them are of whinstone, others of porphyry, strongly -characterized by rectangular maculæ of feldspar, and many seem to be -of sandstone, but so considerably altered, as to leave it at least -disputable whether they really are so or not. In one part, however, -where the face of the rock is nearly perpendicular, a narrow ridge is -seen standing out from the rest, and of a different colour, being more -entirely covered with moss than the rock round about it, and, as may -be presumed from that circumstance, less liable to decomposition. On -examination I found, that this ridge does not consist of whinstone, but -of a very hard and highly consolidated sandstone. It appears to be the -edge of a stratum, of the thickness of about nine or ten inches, and of -the height of fifteen or sixteen feet. It is not perfectly straight, -but slightly waved, its general direction being nearly vertical; and -it is on both sides firmly embraced by the whinstone. When broken, it -appears that this sandstone resembles in colour, and in every thing -<span class="pagenum" id="Page_299">- 299 -</span> -but its greater consolidation, and more vitreous structure, the common -grit found at the bottom of the hill, and over all the adjacent plain.</p> - -<p>262. If all these circumstances are put together, there appears but -one conclusion that can be drawn from them. We have here the manifest -marks of some power which could lift up this fragment of rock from its -native place, distant at least several hundred yards from its present -situation, place it upright on its edge, encompass it with a solid -rock, of a nature quite heterogeneous to itself, and bestow on it, at -the same time, a great addition of solidity and induration. If the mass -in which this stone is now imbedded, be supposed to have been once in -fusion, and forcibly thrown up from below, invading the strata, and -carrying the fragments along with it, the whole phenomena now described -admit of an explanation, and all the circumstances accord perfectly -with one another; but, without this supposition, they are so many -separate prodigies, which have no connection with one another, nor with -any thing that is known. It is indeed impossible, that the effects of -motion and heat can be more clearly expressed than they are here, or -the subject in which these powers resided more distinctly pointed out.</p> - -<p><span class="pagenum" id="Page_300">- 300 -</span></p> - -<p>263. The preceding facts being susceptible but of one interpretation, -are on that account extremely valuable. The phenomena of Salisbury -<i>Craig</i>, near the same place, are almost equally free from -ambiguity. The basaltic rock which forms that precipice, rests on -arenaceous or marly strata; and these, in their immediate contact with -the former, afford an instance of what is mentioned <a href="#sec_67">§ 67</a>, namely, the -conversion of the strata in such situations into a kind of petrosilex, -or even jasper. The line which separates the one rock from the other, -is, at the same time, so well defined, as, in the eyes even of the most -determined Neptunist, to exclude all idea of insensible gradation.</p> - -<p>264. The same rock affords some remarkable instances of the disturbance -of the strata contiguous to the whinstone. The beds of the former are -bent upwards in several places; and, at one in particular, form an -arch, with its convexity downward, so as to make it evident, that the -force which produced this bending was directed from below upwards.</p> - -<p>265. It is, however, where whinstone takes the form of veins, -intersecting the strata, that the induration of the latter is most -conspicuous. The coast of Ayrshire, and the opposite coast of -<span class="pagenum" id="Page_301">- 301 -</span> -Arran, exhibit these veins in astonishing variety and abundance. The -strata are, in many instances, so <i>reticulated</i> by the veins, -and intersected at such small distances, that it seems necessary to -suppose, that the fissures in them were hardly sooner made than filled -up. This at least is true, if the veins are to be accounted all of the -same formation; and, in the greatest number of instances by far, there -is no mark of the one being posterior to the other.</p> - -<p>266. The induration of the sides of these veins, in some cases, has -been such, that the sides have become more durable than the vein -itself; so that the whinstone has been worn away by the washing of the -waves, and has left the sides standing up, with an empty space, like a -<i>ditch</i>, between them. One of these I remarked on the south side -of Brodick Bay, in Arran, which, where it met the face of an abrupt -cliff was not less than forty or fifty feet in depth.</p> - -<p>267. I shall pass over whatever argument might be drawn in favour -of our system, from the slender ramifications of the veins, and -the varieties of their sizes, from a few inches to many fathoms in -diameter, and also from the connection which they often appear to have -with the great tabular masses of basaltes; and shall only -<span class="pagenum" id="Page_302">- 302 -</span> -add a few -remarks on the charring of coal in the vicinity of veins or masses -of whinstone. The connection between the charring of coal and the -presence of whinstone, was first observed by Dr Hutton; and, as far as -opportunities of verifying the observation have yet occurred, appears -to be a fact no less general than it is curious and interesting. In the -coal mines of Scotland, it certainly holds remarkably, particularly in -those about Saltcoats in Ayrshire, where a whinstone dike is known to -stretch across the whole of the coal country, and to be every where -accompanied with blind or uninflammable coal. At Newcastle, dikes of -the same kind are met with, and one, in particular, in what is called -the <i>Walker</i> Colliery, has proved the action of subterraneous fire, to -the satisfaction of mineralogists nowise prejudiced in favour of the -Huttonian system.</p> - -<p>The coal found under basaltes, in the Island of Sky, has been already -mentioned, <a href="#sec_140">§ 140</a>. To what was said concerning the fibrous structure of -the parts of that fossil in immediate contact with the whin, it may be -added, that it is also charred in those parts, so as to have hardly -any flame when it is burnt, though further down it is of the nature of -ordinary coal. Indeed, if there be any truth in Mr Kirwan's general -remark, -<span class="pagenum" id="Page_303">- 303 -</span> -that it is common to find wood coal under basaltes, it must -be understood to arise from this, that the coal in contact with the -basaltes is frequently charred, and its fibrous structure, by that -means, rendered more visible.</p> - -<p>268. It has been objected to the supposition of coal having its -bituminous part driven off by the heat of the whinstone, that this -ought not, on Dr Hutton's principles, to happen in the mineral -regions. But it may be replied, as has been done above, that the local -application of heat might certainly produce this effect, and might -drive off the volatile ports from a hotter to a colder part of the -same stratum. The bitumen has not been so volatilized and expanded as -entirely to escape from the mineral regions; but it has been expelled -from some parts of a mass, only to be condensed and concentrated in -others. This supposition coincides exactly with the appearances.</p> - -<p>269. The native or fossil coke which accompanies whinstone, has been -distinguished into two varieties. The first is the most common, in -which, though the coal is perfectly charred, it is solid, and breaks -with a smooth and shining surface. The second is also perfect charcoal, -but is very porous and spongy. This substance is much rarer than the -other. Dr Hutton mentions an -<span class="pagenum" id="Page_304">- 304 -</span> -instance of it at the mouth of the river -Ayr, where there is a whinstone dike.<a id="FNanchor_137" href="#Footnote_137" class="fnanchor">[137]</a> I had the satisfaction of -visiting it along with him. It was in the bed of the river, below -the high water mark; the specimens had the exact appearance of a -<i>cinder</i>.</p> - -<div class="footnote"> - -<p><a id="Footnote_137" href="#FNanchor_137" class="label">[137]</a> Theory of the Earth, vol. i. p. 611.</p> - -</div> - -<p>In the banks of the same river, some miles higher up, he found a piece -of coal, belonging to a regular stratum, involved in whinstone, and -extremely incombustible. It consumed very slowly in the fire, and -deflagrated with nitre like plumbago. This be considered as the same -fossil which has been described under the name of <i>plombagine</i>. -Near it, and connected with the same vein of whinstone, was a real and -undoubted plumbago.</p> - -<p>From these circumstances he also concluded, that plumbago is the -extreme of a gradation, of which fossil-coal is the beginning, and is -nothing else than this last reduced to perfect charcoal This agrees -with the chemical analysis, which shows plumbago to be composed -of carbon, combined with iron.</p> - -<p>In confirmation of this theory, he mentions a specimen, in his -possession, of steatical whinstone, from Cumberland, containing -nodules of a very perfect and beautiful plumbago; and he also takes -notice of a mine of this -<span class="pagenum" id="Page_305">- 305 -</span> -last, in Ayrshire, which, on the authority of -Dr Kennedy, who has examined it with great care, I can state as being -contained, or enveloped in whinstone; and I hope the public will soon -be favoured with a particular description of this very interesting -spot, by the same ingenious and accurate observer.</p> - -<p>270. Thus the mineralogical and chemical discoveries agree in -representing coal, blind coal, plombagine, plumbago, as all -modifications of the same substance, and as exhibiting the same -principle, carbon, in a state of greater or less combination. As -the last and highest term of this series should be placed the -<i>diamond</i>; but we are yet unacquainted with the matrix of this -curious fossil, and its geological relation to other minerals. When -known, they will probably give to this substance the same place in the -geological, as in the chemical arrangement: in the mean time, it is -hardly necessary to remark, how well all the preceding facts agree with -the hypothesis of the igneous formation of whinstone, and how anomalous -and unconnected they appear, according to every other theory.</p> - -<p>271. Notwithstanding all this accumulated and unanswerable evidence -for the igneous formation of basaltes, a great objection would still -remain to our theory, were it not for the very accurate and conclusive -experiments concerning -<span class="pagenum" id="Page_306">- 306 -</span> -the fusion of this fossil, referred to above, § -75. A strong prejudice against the production of any thing like a real -stone by means of fusion, had arisen, even among those mineralogists, -who were every day witnesses of the stony appearance assumed by -volcanic lava. They still maintained, on the authority of their own -imperfect experiments, that nothing but glass can ever be obtained -by the melting of earths or of stones, in whatever manner they are -combined.</p> - -<p>An ingenious naturalist, after describing a block of basaltes, in which -he discovered such appearances, as inclined him to admit its igneous -consolidation, rejects that hypothesis, merely from the imaginary -inability of fire to give to any substance a stony character: "Quelque -mélange,"says he, "de terres que l'on suppose, quelque soit le degré -de feu que l'on imagine, quelque soit le tems que l'on emploie, il est -très certain que l'on n'obtiendra pas, par le seul fluide igné, ni -basalte, ni rien qui lui ressemble."<a id="FNanchor_138" href="#Footnote_138" class="fnanchor">[138]</a></p> - -<div class="footnote"> - -<p><a id="Footnote_138" href="#FNanchor_138" class="label">[138]</a> Journal de Phys. tom. xlix. (1799,) p. 36.</p> - -</div> - -<p>Sir James Hall's experiments have completely demonstrated the contrary -of what is here asserted: they have added much to the evidence of the -Huttonian system; and, independently of -<span class="pagenum" id="Page_307">- 307 -</span> -all theory, have narrowed the -circle of prejudice and error.</p> - - -<hr class="chap x-ebookmaker-drop" /> - -<div class="chapter"> -<h2 class="nobreak" id="Note_xv"><span class="smcap">Note xv. § 83.</span></h2> -</div> - -<p class="caption3nb"><i>On Granite.</i></p> - - -<p class="caption3nb">1. <i>Granite Veins.</i></p> - -<p>272. It is said above, <a href="#sec_77">§ 77</a>, that granite is found in unstratified -masses, and in veins. In the former of these conditions, it constitutes -entire mountains, and forms the central ridge of many of the greatest -chains that traverse the surface of the earth. It is the granite of -this kind that has been most generally described by travellers and -mineralogists. The veins have not been so much attended to, though -they are of peculiar importance for ascertaining the relation between -granite and other fossils.</p> - -<p>273. Though Dr Hutton was the first geologist who explained the nature -of granite veins, and who observed with attention the phenomena -which accompany them, he is not the first who has mentioned them. M. -Besson found veins of this kind in the Limoges, in an argillaceous -schistus, and unconnected, as far as appeared, with any large mass of -granite.<a id="FNanchor_139" href="#Footnote_139" class="fnanchor">[139]</a></p> - -<div class="footnote"> - -<p><a id="Footnote_139" href="#FNanchor_139" class="label">[139]</a> Journal de Phys. tom. xxix. p. 89.</p> - -</div> - -<p><span class="pagenum" id="Page_308">- 308 -</span></p> - -<p>Saussure met with granite veins in the Valorsine, but did not see them -distinctly. He ascribed them to infiltration.<a id="FNanchor_140" href="#Footnote_140" class="fnanchor">[140]</a> The date of this -observation is in 1776: He afterwards discovered similar appearances at -Lyons.<a id="FNanchor_141" href="#Footnote_141" class="fnanchor">[141]</a></p> - -<div class="footnote"> - -<p><a id="Footnote_140" href="#FNanchor_140" class="label">[140]</a> Voyage au Alpes, tom. i. § 598, 599.</p> - -<p><a id="Footnote_141" href="#FNanchor_141" class="label">[141]</a> <i>Ibid.</i> § 601.</p> - -</div> - -<p>Werner also, in enumerating the substances of which veins are formed, -reckons granite as one of them.</p> - -<p>274. Veins of granite may be considered as of two kinds, according as -they are connected, or not connected apparently with any large mass of -granite, it is probable, that these two kinds of veins only differ in -appearance, and that both are connected with masses of the same rock, -though that connection is visible in some instances, and invisible in -others. The distinction, however, whatever it be with respect to the -thing observed, is real with respect to the observer; and, as it is -right, in a description of facts, to avoid every thing hypothetical, I -shall speak of these veins separately.</p> - -<p>275. Veins of granite, having no communication, so far as can be -discovered, with any mass of the same rock, are found in the Western -Islands of Scotland, peculiarly in that of Coll, -<span class="pagenum" id="Page_309">- 309 -</span> -where they traverse -the beds of gneiss and hornblende schistus, which compose the main -body of the island. They are sometimes several fathoms in thickness, -obliquely intersecting the planes of the strata just mentioned, which -are nearly vertical. In these veins the feldspar is predominant; it is -very highly crystallized, and of a beautiful flesh colour. Many smaller -veins are also to be met with in the same place; but no large mass of -granite is found, either in this or the adjacent island of Tiree.</p> - -<p>276. The Portsoy granite, of which mention has been already made, § -80, also constitutes a vein or dike, traversing a highly indurated -micaceous schistus, about a mile to the eastward of the little town -of Portsoy, and not visibly connected with any large mass of the same -kind. More dikes than one of this granite have been observed near the -same spot.</p> - -<p>A similar granite is likewise found inland, in the neighbourhood of -Huntly, about eighteen miles south of Portsoy; but whether in the shape -of a vein or a mass, I have not been able to learn.</p> - -<p>277. Veins of granite are also frequent in Cornwall, where they are -known by the name of <i>lodes</i>, the same name which is applied in -that country to metallic veins. The granite veins frequently -<span class="pagenum" id="Page_310">- 310 -</span> -intersect -the metallic, and are remarkable for producing shifts in them, or -for throwing them out of their natural direction. The mineral veins, -particularly those that yield copper and tin, run nearly from east -to west, having the same direction with the beds of the rock itself, -which is a very hard schistus. The granite lodes, as also those of -porphyry, called <i>elvan</i> in Cornwall, are at right angles nearly -to the former; and it is remarked, that they generally heave the -mineral veins, but that the mineral veins seldom or never heave the -cross-veins. In this country, therefore, the veins of granite and -porphyry are posterior in formation to the metallic veins. These veins -of granite may perhaps be connected with the great granitic mass that -runs longitudinally through Cornwall, from Dartmoor to the Land's End. -This much is certain, that their directions in general are such, that, -if produced, they would intersect that mass, nearly at right angles.</p> - -<p>278. The granite veins in Glentilt, where Dr Hutton made his first -observations on this subject, are not, I believe, visibly connected -with any large mass of the same rock.<a id="FNanchor_142" href="#Footnote_142" class="fnanchor">[142]</a> The bed of the river Tilt, -in the distance of little more than a mile, -<span class="pagenum" id="Page_311">- 311 -</span> -is intersected by no -less than six very powerful veins of granite, all of them accompanied -with such marks of disorder and confusion in the strata, as indicate -very strongly the violence with which the granite was here introduced -into its place. These veins very probably belong to the great mass -of granite which is known to form the central ridge of the Grampians -further to the north; but they are several miles distant from it, and -the connection is perhaps invisible in the present state of the earth's -surface.</p> - -<div class="footnote"> - -<p><a id="Footnote_142" href="#FNanchor_142" class="label">[142]</a> Trans. Royal Society Edin. Vol iii. p. 77, &c.</p> - -</div> - -<p>279. The second kind of granite vein, is one which proceeds visibly -from a mass of that rock, and penetrates into the contiguous strata. -The importance of this class of veins, for ascertaining the relation -between granite and other mineral bodies, has been pointed out, § -82; and by means of them it has been shown, that the granite, though -inferior in position, is of more recent formation than the schistus -incumbent on it; and that the latter, instead of having been quietly -deposited on the former, has been, long after its deposition and -consolidation, heaved up from its horizontal position, by the liquid -body of granite forcibly impelled against it from below.</p> - -<p>It has been alleged, in order to take off the force of the argument -derived from granite -<span class="pagenum" id="Page_312">- 312 -</span> -veins, that these veins are formed by -infiltration, though, to give any probability to this supposition, -it would be necessary to show, that water is able to dissolve the -ingredients of granite; and even if this could be done, the direction -which the veins have, in many instances, rising up from the granite, -is a proof, as remarked <a href="#sec_82">§ 82</a>, that they cannot be the effect of -infiltration.</p> - -<p>Another objection has been thrown out, namely, that the veins here -referred to are not of true granite, according to the definition -which mineralogists have given of that substance. The force of a -fact, however, is not to be lessened by a change of names, or the -use of arbitrary definitions. The general fact is, that the granitic -mass, and the vein proceeding from it, constitute one continuous, -and uninterrupted body, without any line of separation between them. -The geological argument turns on this circumstance alone; and it is -no matter whether the rock be a syenite, a granitelle, or a real -granite. The phenomenon speaks the same language, and leads to the same -conclusion, whatever be the technical terms the mineralogist employs in -describing it.</p> - -<p>280. It must, however, be admitted, that a difference of character is -often to be observed between the granite mass and the veins proceeding -<span class="pagenum" id="Page_313">- 313 -</span> -from it; sometimes the substances in the latter are more highly -crystallized than in the former; sometimes, but more rarely, they are -less crystallized, and, in some instances, an ingredient that enters -into the mass seems entirely wanting in the vein. These varieties, -for what we yet know, are not subject to any general rule; but they -have been held out as a proof, that the masses and the veins are not -of the same formation. It may be answered, that a perfect similarity -between substances that, on every hypothesis, must have crystallized -in very different circumstances, is not always to be looked for; but -the most direct answer is, that this perfect similarity does sometimes -occur, insomuch that, in certain instances, no difference whatsoever -can be discovered between the mass and the vein, but they consist of -the same ingredients, and have the same degree of crystallization. Some -instances of this are just about to be remarked.</p> - -<p>281. A strong objection to the supposed origin of granitic veins -from infiltration, and indeed to their formation in any way but by -igneous fusion, arises from the number of fragments of schistus, often -contained, and completely insulated in those veins. How these fragments -were introduced into the fissures of the schistus, and sustained till -they were surrounded -<span class="pagenum" id="Page_314">- 314 -</span> -by the matter deposited by water, is very hard -to be conceived; but if they were carried in by the melted granite, -nothing is more easily understood.</p> - -<p>The following are some of the places where the phenomena of granite -veins may be distinctly seen.</p> - -<p>282. The island of Arran, remarkable for collecting into a very small -compass a great number of the most interesting facts of geology, -exhibits many instances of the penetration of schistus by veins of -granite. A group of granite mountains occupies the northern extremity -of the island, the highest of which, Goatfield, rises nearly to the -height of 3000 feet, and on the south side is covered with schistus -to the height of 1100. From thence, the line of junction, or that -at which the granite emerges from under the schistus, winds, so far -as I was able to observe, round the whole group of mountains, with -many wavings and irregularities, rising sometimes to a greater, and -descending sometimes to a much lower level, than that just mentioned. -Along this line, particularly on the south, wherever the rock is laid -bare, and cut into by the torrents, innumerable veins of granite are to -be seen entering into the schistus, growing narrower as they advance -into it; and being directed, in very many cases, from -<span class="pagenum" id="Page_315">- 315 -</span> -below upwards, -they are precisely of the kind which the infiltration of water could -not produce, even were that fluid capable of dissolving the substances -which the vein consists of. From this south face of the mountain, and -from the bed of a torrent that intersects it very deeply, Dr Hutton -brought a block of schistus, of several hundred weight, curiously -penetrated by granite veins, including in them many insulated fragments -of the schistus.</p> - -<p>From this point, the common section of the granite and schistus -descends towards the west side of the mountain, and is visible at the -bottom of a deep glen, (Glen-Rosa,) which detaches Goatfield from the -hills farther to the west. The junction is laid bare at several places -in the bed of the river which runs in the bottom of this glen; and in -all of them exhibits, in a greater or less degree, the appearances of -disturbance and violence which have accompanied the injection of the -granite veins. Many circumstances render this spot interesting to a -geologist, and, among others, an intersection of the granite, a little -above its junction with the schistus, by a dike or vein of very compact -whinstone.</p> - -<p>The same line of junction is found on the opposite, or north-east, side -of the mountain, -<span class="pagenum" id="Page_316">- 316 -</span> -where it is intersected by another little river, the -Sannax, which on this side determines the base of the mountain. This -junction is no less remarkable than the other two.</p> - -<p>The island of Arran contains, I have no doubt, many other spots where -these phenomena are to be seen; but I have had no opportunity of -observing them, nor do I find that Dr Hutton met with any others in his -visit to this island.</p> - -<p><a id="sec_283"></a>283. Another series of granite veins is found in Galloway, which was -first discovered by Dr Hutton and his friend Mr Clerk, and afterwards -more fully explored by Sir James Hall and Mr Douglas, the present Earl -of Selkirk. The two last traced the line of separation between a mass -of granite and the schistus incumbent upon it, all round a tract of -country, about eleven miles by seven, extending from the banks of Loch -Ken westward; and in all this tract they found, "that wherever the -junction of the granite with the schistus was visible, veins of the -former, from fifty yards, to the tenth of an inch in width, were to be -seen running into the latter, and pervading it in all directions, so -as to put it beyond all doubt, that the granite of these veins, and -consequently of -<span class="pagenum" id="Page_317">- 317 -</span> -the great body itself, which was observed to form with -the veins one uninterrupted mass, must have flowed in a soft or liquid -state into its present position."<a id="FNanchor_143" href="#Footnote_143" class="fnanchor">[143]</a> I have only farther to add, that -some of these veins are remarkable for containing granite, not sensibly -different, in any respect, from the mass from which they proceed.</p> - -<div class="footnote"> - -<p><a id="Footnote_143" href="#FNanchor_143" class="label">[143]</a> Trans. Royal Society Edin. vol. iii. p. 8.</p> - -</div> - -<p>284. In Invernessshire, between Bernera and Fort Augustus, the same -phenomena occur on the north side of Loch Chloney, where some granite -mountains rise from under the schistus. In travelling near this place, -Lord Webb Seymour and myself were advertised of our approach to a -junction of granite and schistus, by finding among the loose stones on -the road many pieces of schistus, intersected with veins of feldspar -and granite. We walked along this junction for more than a mile; and -toward the east end, where the road leaves it, we saw, in the bed of -a stream that runs into Loch Chloney, many beautiful specimens of -granitic veins pervading the schistus, and branching out into very -minute ramifications.</p> - -<p>285. The last instance I have to mention from my own observation, is -at St Michael's -<span class="pagenum" id="Page_318">- 318 -</span> -Mount in Cornwall. That mount is entirely of granite, -thrust up from under a very hard micaceous schistus, which surrounds -it on all sides. At the base of it, on the west side, a great number -of veins run off from the granite, and spread themselves like so many -roots fixed in the schistus: they are seen at low water. In the smaller -veins, the granite is of very minute, though distinct parts; in the -larger, it is more highly crystallized, and is undistinguishable from -the mass of the hill.</p> - -<p>Besides the above, Cornwall probably affords many other instances of -the same kind, which I have not had an opportunity to examine. Such -instances may in particular be looked for at the Land's End, where a -promontory, consisting of a central part of granite, and covered by -a micaceous schistus on both sides of it, is cut transversely by the -sea coast, and the contact of the granite and schistus of course twice -exposed to view.</p> - -<p>286. Scotland also affords other examples of granite veins, and some -of them have been actually described. Mr Jameson has taken notice of -some which he saw in the bottom of the river Spey, at Glen Drummond, in -Badenach, and has represented them in an engraving.<a id="FNanchor_144" href="#Footnote_144" class="fnanchor">[144]</a><span class="pagenum" id="Page_319">- 319 -</span> They traverse -the strata in various directions, and inclose pieces of the micaceous -schistus; and, from the great number of loose blocks which he found, -exhibiting portions of such veins, it is probable, that they are very -numerous in this quarter. The same mineralogist mentions some instances -of similar veins in the Shetland Isles.<a id="FNanchor_145" href="#Footnote_145" class="fnanchor">[145]</a></p> - -<div class="footnote"> - -<p><a id="Footnote_144" href="#FNanchor_144" class="label">[144]</a> Mineralogy of the Scottish Isles, vol. ii. p. 3.</p> - -<p><a id="Footnote_145" href="#FNanchor_145" class="label">[145]</a> <i>Ibid.</i> p. 216.</p> - -</div> - -<p>In Ross-shire, Sir George Mackenzie has observed a great variety of -granite veins, some of them of large size. One of them, in particular, -not far from Coul, when first discovered, was supposed to be a -single mass, rising from under the schistus; but, on a more careful -examination, has been found to be a part of a great system of veins -which intersects the micaceous schistus of this tract in various -directions.</p> - -<p>287. The granite veins are not the only proof that this stone is more -recent than some other productions of the mineral kingdom. Specimens -of granite are often found, containing round nodules of other stones, -as, for example, of gneiss or micaceous schistus. Such is the specimen -of granite containing gneiss, which Werner himself is said to be in -possession of, and -<span class="pagenum" id="Page_320">- 320 -</span> -to consider as a proof, that the schistus is of -greater antiquity than the granite. Such also seemed to me some pieces -of granite, which I met with in Cornwall, near the Land's End; and -others which I saw in Ayrshire, in loose blocks, on the sea coast -between Ayr and Girvan. It is impossible to deny that the containing -stone is more modern than the contained. The Neptunists indeed admit -this to be true, but allege, that all granite is not of the same -formation; and that, though some granite is recent, the greater part -boasts of the highest antiquity which belongs to any thing in the -fossil kingdom. This distinction, however, is purely hypothetical; it -is a fiction contrived on purpose to reconcile the fact here mentioned -with the general system of aqueous deposition, and has no support from -any other phenomenon.</p> - - -<p id="Granite_of_Portsoy" class="caption3nb">2. <i>Granite of Portsoy.</i></p> - -<p>288. The granite of Portsoy is one of the most singular varieties of -this stone, and is remarkable for this circumstance, that the feldspar -is the substance which has assumed the figure of its proper crystal, -and has given its form -<span class="pagenum" id="Page_321">- 321 -</span> -to the quartz, so that the latter is impressed -both with the acute and obtuse angles belonging to the rhombic figure -of the former. The angular pieces of quartz thus moulded on the -feltspar, and ranged by means of it in rows, give to this stone the -appearance of rude alphabetical writing.</p> - -<p>Now, Dr Hutton argued, that substances precipitated from a solution, -and crystallizing at liberty, cannot be supposed to impress one another -in the manner here exemplified; and that they could do so only when -the whole mass acquired solidity at the same time, or at the same time -nearly.<a id="FNanchor_146" href="#Footnote_146" class="fnanchor">[146]</a> Such simultaneous consolidation can be produced in no way -that we know of, but by the cooling of a mass that has been in fusion.</p> - -<div class="footnote"> - -<p><a id="Footnote_146" href="#FNanchor_146" class="label">[146]</a> Theory of the Earth, vol. i. P. 104.</p> - -</div> - -<p>289. A granite, brought from Daouria by M. <span class="smcap">Patrin</span>, and -described by him in the Journal de Physique for 1791, p. 295, under the -name of <i>pierre graphique</i>, seemed to Dr Hutton to have so great -a resemblance to the granite of Portsoy, that he ventured to consider -them both as the same stone, and as both containing quartz moulded on -feltspar.<a id="FNanchor_147" href="#Footnote_147" class="fnanchor">[147]</a> It should seem, however, -<span class="pagenum" id="Page_322">- 322 -</span> from further explanations, -which M. Patrin has since given, but Dr Hutton was mistaken in his -conjecture, and that, in the <i>pierre graphique</i> of the former -mineralogist, the quartz gives its form to the feltspar, preserving in -its crystals their natural angle of 120 degrees<a id="FNanchor_148" href="#Footnote_148" class="fnanchor">[148]</a> It is impossible, -I think, to doubt of the accuracy of this statement; and the graphical -stone of Portsoy must therefore be admitted to differ materially from -that of Daouria. They are not, however, without some considerable -affinity, besides that of their outward appearance; for, though the -quartz in the former is generally moulded on the feltspar, the feldspar -is also occasionally impressed by the quartz, and sometimes even -included in it. They may be considered as varieties of the same species -of granite; and the <i>pierre graphique</i> of Corsica is probably a -third variety, different from them both.</p> - -<div class="footnote"> - -<p><a id="Footnote_147" href="#FNanchor_147" class="label">[147]</a> Trans. Royal Society Edin. vol. iii. p. 83.</p> - -<p><a id="Footnote_148" href="#FNanchor_148" class="label">[148]</a> Journal Britainnique, (of Geneva,) 1798, vol. viii. -Sciences et Arts, p. 78.</p> - -</div> - -<p>290. It would seem, however, that all these stones lead exactly to the -same conclusion. M. Patrin describes his specimen as containing quartz -crystals, that are for the most part only <i>cases</i>, having their -interior filled with feltspar "Le feltspath -<span class="pagenum" id="Page_323">- 323 -</span> -en masse contient des -crysteaux quartzeux, qui n'ont le plus souvent que la carcasse, et dont -l'interieur est rempli de feltspath; souvent il manque à ces carcasses -quelques unes de leurs faces, et souvent la section de cette pierre -dans un sens transversal aux crysteaux, presente une suite de figures -qui sont des portions d'hexagones, et qui ne resemblent pas mal à des -caractères Hebraiques."<a id="FNanchor_149" href="#Footnote_149" class="fnanchor">[149]</a></p> - -<div class="footnote"> - -<p><a id="Footnote_149" href="#FNanchor_149" class="label">[149]</a> Journal Britannique, <i>Ibid.</i></p> - -</div> - -<p>These imperfect hexagonal cases of quartz, filled with feldspar, -certainly indicate the crystallization of substances, which all -assumed their solidity at the same time, and, in doing so, constrained -the figures of one another. To use the words of Dr Hutton, "whether -crystallizing quartz inclose a body of feltspar, or concreting feltspar -determine the shape of fluid quartz, particularly if we have, as is -here the case, two solid bodies including and included, it amounts to -a demonstration, that those bodies have concreted from a fluid state -of fusion, have not crystallized, in the manner of salts, from a -solution."<a id="FNanchor_150" href="#Footnote_150" class="fnanchor">[150]</a></p> - -<div class="footnote"> - -<p><a id="Footnote_150" href="#FNanchor_150" class="label">[150]</a> Trans. Royal Society Edin. <i>ubi supra</i>, p. 84.</p> - -</div> - -<p>291. The quartz in granite so generally receives the impressions of -all the other substances, -<span class="pagenum" id="Page_324">- 324 -</span> -particularly of the feldspar and schorl, -and appears to be so passive a body, that it has been doubted by some -mineralogists, whether in this stone it ever assumes its own figure, -except where cavities afford room for its crystallization. But it -is certain that, beside the Daourian granite just mentioned, there -are others, in which the quartz is completely crystallized. Of this -sort are some specimens, found in a granite vein on the west side of -the hill of St Agnes, in Cornwall. The vein traverses the primitive -schistus, of which that hill consists, from south to north nearly: -the stone is much decomposed, and the feldspar in general is almost -reduced to the state of clay. In this decomposed mass, quartz crystals -are found, having the shape of double hexagonal pyramids, perfectly -regular and complete. The side of the hexagon, which is the base of the -two opposite pyramids, varies from half a tenth to a tenth of an inch -in length, and is the same with the altitude of each of the pyramids. -In some few specimens, the two pyramids do not rest on the same base, -but are separated by a very short, though regular, hexagonal prism. -The surfaces of these crystals are rough, and somewhat opaque, with -slender spiculæ of schorl frequently traversing them. This roughness -is occasioned by slight -<span class="pagenum" id="Page_325">- 325 -</span> -furrows on the surface of the crystal, very -regularly disposed, and parallel to one another, being without doubt -impressions from the thin plates of the feldspar, which surrounded -the crystal, and slightly indented it. They very much resemble some -impressions, remarked by Dr Hutton in the granite of Portsoy, and -ascribed by him also to a similar cause. He has represented these in -his Theory of the Earth, vol. i. plate ii. fig. 4. The action and -reaction of two crystallizing bodies, hardly admits of a stronger and -more unequivocal expression, than in these two instances.</p> - -<p>Where the granite was little decomposed, the quartz was not easily -disengaged from the mass it was imbedded in, and often broke in pieces -before it could be extricated. The crystallization of the quartz, -therefore, would not have been discovered, but for the decomposition of -the feltspar; and it is probable, that similar crystallizations exist -in many granites where they are not perceived.</p> - -<p>292. Some mineralogists are inclined to think, that the regular -crystallization of quartz is to be found only in what they call -secondary granites, or in those that are of a formation subsequent -to the great masses which constitute the granite mountains. It is -indeed true, that in the instances -<span class="pagenum" id="Page_326">- 326 -</span> -given here, both from Cornwall and -Daouria, the granites containing quartz crystals are from veins that -intersect the primary schistus, and are therefore, on every hypothesis, -of a formation subsequent to that schistus. But it does not follow -from thence, that they are less ancient than the great masses of -unstratified granite; with these last they are most probably coëval, -nor can there be any reason for thinking the crystallization of quartz -a mark of more recent formation than that of feltspar.</p> - - -<p class="caption3nb" id="Stratification">3. <i>Stratification of Granite.</i></p> - -<p>293. What are the various modes in which granite exists, is a question -not absolutely decided among mineralogists. 1. That it exists as -a schistose stone of a fissile texture, in gneiss and <i>veined -granite</i>, is on all hands admitted, though in this state the name of -granite is generally withheld from it. 2. That it exists often without -any indication of a fissile texture, and altogether unstratified, is -likewise acknowledged. 3. That it is found in veins, intersecting -the strata, has been shown above. The only mode of its existence -subject to dispute, is that in which it is said to be stratified in -its outward -<span class="pagenum" id="Page_327">- 327 -</span> -configuration, but not schistose in its texture. On this -point mineralogists do not perfectly agree: Dr Hutton did not think -that this was a state in which granite ever appears. When not schistose -in its structure, he supposed it to be unstratified altogether; and -he considered it as a body which, like whinstone, was originally in -a state of igneous fusion, and, in that condition, injected among -the strata. The school of Werner, on the other hand, maintain, that -granite, if not always, is generally stratified, and disposed in beds, -sometimes horizontal, though more frequently vertical, or highly -inclined.</p> - -<p>In forming an opinion where there are great authorities on opposite -sides, a man must trust chiefly to his own observations, and ought -to esteem himself fortunate if these lead to any certain conclusion. -Mine incline me to differ from Dr Hutton, on the one hand, and from -the Neptunists, on the other, as they convince me, that granite does -form strata where it has no character of gneiss; and, at the same -time, induce me to suspect, that the stratification ascribed by the -Neptunists to the granite mountains, is, in many instances, either an -illusion, or at least something very different from what, in other -stones, is accounted stratification.</p> - -<p><span class="pagenum" id="Page_328">- 328 -</span></p> - -<p>294. The first example I ever saw of granite that was stratified, -and yet had no character of gneiss, was at Chorley Forest, in -Leicestershire. The greater part of that forest has for its base a -hornstone schistus, primary and vertical; and, on its eastern border, -particularly near Mount Sorrel, are beds of granite, holding the same -direction with those of the schistus. The stone is a real granite; -it has nothing in its internal structure of a schistose or fissile -appearance; and its beds, which it is material to remark, are no -thicker than those of the hornstone strata in the neighbourhood. This -granite is remarkable, too, for being close to the secondary sandstone -strata; I did not see their contact, but traced them within a small -distance of one another; so that I think it is not likely that any body -of rock intervenes. At the same time that I state my belief of this -rock of granite being in regular strata, I must acknowledge, that a -very intelligent mineralogist, who viewed these rocks at the same time, -and whose eye was well practised in geological observation, remained in -doubt concerning them.</p> - -<p>295. Another instance of a real granite, disposed in regular beds, but -without any character of gneiss, is one which I saw in Berwickshire, -in Lammermuir, near the village of Priestlaw. The little river of -Fassnet cuts the beds across, -<span class="pagenum" id="Page_329">- 329 -</span> -and renders it easy to observe their -structure. The beds are not very thick; they run from about S.S.W. to -N.N.E. like the schistus on either side of them. I was in company with -Sir James Hall when I saw these rocks; we examined them with a good -deal of attention, and traced them for more than a mile in the bed of -the river; and, if I mistake not, our opinions concerning them were -precisely the same.</p> - -<p>296. What exists in two instances may exist in many, and, after these -observations, I should be guilty of great inconsistency, in refusing -to assent to the accounts of Pallas, De Luc, Saussure, and many other -mineralogists, who so often represent granite as formed into strata. -In some cases, however, it is certain, that the stratification they -describe is extremely unlike that in the two instances just mentioned, -and indeed very unlike any thing that is elsewhere known by the name -of stratification. For example, the stratification must be very -ambiguous, and very obscurely marked, that was not discovered till -after a series of observations, continued for more than twenty years, -by a very skilful and distinguishing mineralogist. Yet such undoubtedly -is the stratification of Mont Blanc, and of the granite mountains in -its neighbourhood, as it escaped the eyes of Saussure, in the repeated -visits which he made to them, during a period of -<span class="pagenum" id="Page_330">- 330 -</span> -no less extent than -has just been mentioned. It was not till near the conclusion of those -labours, to which the geologists of every age will consider themselves -as highly indebted, that, having reached the summit of Mont Blanc, he -perceived, or thought that he perceived, the stratification of the -granite mountains. The <i>Aiguilles</i> or Needles which border the -valley of Chamouni, and even Mont Blanc itself, appeared to be formed -of vast tabular masses of granite, in position nearly vertical, and so -exactly parallel, that he did not hesitate to call them by the name of -strata. Till this moment, these same mountains, viewed from a lower -point, had been regarded by him as composed of great plates of rock, -nearly vertical indeed, but applied, as it were, round an axis, and -resembling the leaves of an artichoke;<a id="FNanchor_151" href="#Footnote_151" class="fnanchor">[151]</a> and the fissures by which -they are separated from one another, had been considered as effects of -waste and degradation. "But now," (says he, speaking of the view from the -top of Mont Blanc,) "I was fully convinced, that these mountains -are entirely composed of vast plates of granite, perpendicular to -the horizon, and directed from N.E. to S.W. Three of these plates, -separated from each other, formed -the -<span class="pagenum" id="Page_331">- 331 -</span> -top of the <i>Aiguille du -Midi</i>, and other similar plates, decreasing gradually in height, -compose its declivity to the south."<a id="FNanchor_152" href="#Footnote_152" class="fnanchor">[152]</a></p> - -<div class="footnote"> - -<p><a id="Footnote_151" href="#FNanchor_151" class="label">[151]</a> Voyages aux Alpes, tom. ii. § 910, &c.</p> - -<p><a id="Footnote_152" href="#FNanchor_152" class="label">[152]</a> Voyages aux Alpes, tom. iv. § 1996.</p> - -</div> - -<p>297. Saussure was so strongly impressed with the appearances of what -he accounted regular stratification, such as water only can produce, -and such as must have been in the beginning horizontal, that, placed -as he now was, on one of the highest points of the earth's surface, he -formed the bold conception, that the summit on which he was standing -had been once buried under the surface, to the depth at least of half -the diameter of the mountain, and horizontally distant from its present -place by a line not less than the whole height of the mountain; the -granite beds which compose that mountain, having been raised by some -enormous power from their horizontal position, and turned as on an -axis, till they were brought into the vertical plane. In this notion, -which suits so well with the nature of mountains really composed of -vertical strata, and which does credit to the extent of Saussure's -views, it is wonderful that he did not see the overthrow of the -geological system be had adopted, which is provided with no means -whatsoever of explaining these great effects.</p> - -<p><span class="pagenum" id="Page_332">- 332 -</span></p> - -<p>Such, then, were the ideas suggested to Saussure, by viewing the -mountains of the Alps from the highest of their summits. His great -experience, his accurate knowledge of the objects before him, and the -power he had acquired of dissipating those illusions, to which, in -viewing mountainous tracts, the eye is peculiarly subject, all conspire -to give great weight to his opinion. Yet, as this opinion is opposed -by that which he himself had so long entertained, before it can be -received with perfect confidence, it will require to be verified by new -observations. It seems certain, that the beds of rock here described, -differ from all ordinary strata, both horizontal and vertical, in the -circumstance of their vast thickness, three of them being so large as -to form the main body of a mountain. Their parallelism cannot easily -be ascertained; and they have at best but a very slight resemblance to -such beds as water is known to produce.</p> - -<p>298. Their parallelism is difficult to be ascertained; for, on account -of the magnitude and inaccessibility of the objects, it is impossible -to place the eye in any situation, where it shall not be much nearer -to one part of the planes whereof the parallelism is to be estimated, -than to another. Indeed, one can perceive a cause -<span class="pagenum" id="Page_333">- 333 -</span> -which may have -rendered the parallelism of the plates of granite which compose the -<i>aiguilles</i>, more accurate in appearance than in reality, when -viewed from a point so elevated as the summit of Mont Blanc. For, even -on the supposition that the comparison of those plates to leaves of -artichokes was just, and that the planes of their separation converged -toward one another, in ascending to the top, when they were viewed -from a point more elevated than that top, this convergency would -be diminished, and, by the force of the perspective, might even be -converted into parallelism. We cannot at present ascertain what effect -this cause of deception may have actually produced.</p> - -<p>299. The observations of Saussure concerning the stratification -of granite, are not, however, in all instances, liable to these -objections; and it seems to be on much less exceptionable grounds -that he pronounces the granite of St Gothard to be stratified. The -gneiss and micaceous schistus which constitute the lower part of that -mountain, are succeeded by a granite without any schistose appearance, -but divided into large plates, exactly parallel to the beds of the -former gneiss. These he regards as real strata. On studying them in -detail, he says, considerable irregularities were to be observed, but -not greater than in the case -<span class="pagenum" id="Page_334">- 334 -</span> -of limestone or micaceous schistus.<a id="FNanchor_153" href="#Footnote_153" class="fnanchor">[153]</a> -It may be inferred from this, that these plates of granite are not so -thick but that they admit of comparison with beds that are known with -certainty to be of aqueous formation, and I am therefore disposed to -believe, that the granite of St Gothard, in this part at least, is -stratified. The transition from gneiss to granite en masse, is not -uncommon, as Saussure has observed in other instances, and as we are -just about to consider more particularly.</p> - -<div class="footnote"> - -<p><a id="Footnote_153" href="#FNanchor_153" class="label">[153]</a> Voyages aux Alpes, tom. iv. § 1830.</p> - -</div> - -<p>300. In the mountains of our own country, some difficulties concerning -the stratification of granite have also occurred. In Arran, for -instance, the mountain of Goatfield, which I have mentioned above -as affording an instance of granite sending out many veins into -the schistus, and rivetted, as it were, by means of them to the -superincumbent rock, when I visited it, with, a view of verifying -on the spot the interesting observations which Dr Hutton had there -made, appeared to me to be without any vestige of stratification in -its granitic part, as did also the whole group of mountains to which -it belongs. It was, therefore, not without a good deal of surprise, -that I lately read, in an account of that island, by a very accurate -and ingenious mineralogist, -<span class="pagenum" id="Page_335">- 335 -</span> -that Goatfield consists of stratified -granite.<a id="FNanchor_154" href="#Footnote_154" class="fnanchor">[154]</a> The impression which the appearance of that mountain -made on my mind, is just the reverse; and though I saw large tabular -masses, sometimes nearly vertical, separated by fissures, they -appeared to be much too irregular, too little extended in length and -height, and vastly too much in thickness, to be reckoned the effects -of stratification. For all this, I would by no means be understood -to set my observations in opposition to those of Mr Jameson. In my -visit to Arran, I did not direct my inquiries much toward this point; -the general appearance of the rocks did not suggest the necessity of -doing so, and I was not perfectly aware how much the stratification of -granite had been insisted on by some mineralogists; so that I applied -myself entirely to study some other of the interesting phenomena which -this little island offers in so great abundance. I therefore carry -my confidence in the appearances which seemed to indicate a want of -stratification in the granite of Arran no further than to remain -sceptical both as to Mr Jameson's conclusions and my own, till an -opportunity -<span class="pagenum" id="Page_336">- 336 -</span> -shall occur of verifying the one or the other by actual -observation.</p> - -<div class="footnote"> - -<p><a id="Footnote_154" href="#FNanchor_154" class="label">[154]</a> Mineralogy of the Scottish Isles, vol. i. p. 35, 36.</p> - -</div> - -<p>301. The stratification of granite, though it made no part of Dr -Hutton's system, does by no means embarrass his theory with any new -difficulty. Rocks, of which the parts are highly crystallized, are -already admitted as belonging to the strata, and are exemplified in -marble, gneiss, and veined granite. In the two last, we have not only -stratification, but a schistose, united with a crystallized structure, -and the effects of deposition by water, and of fluidity by fire, are -certainly no where more singularly combined. The stratification of -these substances is therefore more extraordinary than even that of the -most highly crystallized granite. Neither the one nor the other can be -explained but by supposing, that while such a degree of fluidity was -produced by heat, as enabled the body when it cooled to crystallize, -the whole mass was kept in its place by great pressure acting on all -sides, so that the shape was preserved as originally given to it by -the sea. As we cannot, however, suppose, that the intensity of the -heat, or the fusibility of the substance through all the parts of a -stratum, were precisely the same, we may expect to find in the same -stratum, or in the same body of strata, that in some parts the marks -of stratification are -<span class="pagenum" id="Page_337">- 337 -</span> -completely obliterated while in others they -remain entire. It is thus that <i>veined granite</i>, of what I think -should be called granitic schistus, often graduates into granite <i>in -mass</i>, that is, granite without any schistose or fissile texture. -Saussure says, that to be veined or not veined, is an affection of -granite, that seems, in many cases, accidental;<a id="FNanchor_155" href="#Footnote_155" class="fnanchor">[155]</a> as, in the midst -of rocks of that substance, most clearly fissile, large portions appear -without any vestige of stratification. Of this phenomenon, which is -frequent in the Alps, instances are also to be met with in the granite -rocks of Scotland, and the adjacent isles; and I know that Dr Hope, -in a mineralogical excursion which he lately made among the Hebrides, -observed many interesting and curious examples of it. Indeed, when -rocks were so much fused as to crystallize, and so compressed, at the -same time, as to remain stratified, they were evidently on the verge of -change; two opposite forces were very nearly balanced, and each carried -as far as it could go without entirely overcoming the other; so that -a small alteration in the conditions may have made a great alteration -in the effects. Hence a sudden transition from a stratified to -<span class="pagenum" id="Page_338">- 338 -</span> -an unstratified texture, which is only found in rocks highly crystallized, -and such as have endured the most violent action of the mineralizing -powers.</p> - -<div class="footnote"> - -<p><a id="Footnote_155" href="#FNanchor_155" class="label">[155]</a> Voyages aux Alpes, tom. iv. § 2143.</p> - -</div> - -<p>302. Now, though the stratification of granite, or the mixture of the -stratified with the unstratified rocks of that genus, is not only -reconcilable with the principles of the Huttonian geology, but might -even have been deduced as a corollary from those principles, before -it was actually observed, it may be considered as inconsistent with -the theory of granitic veins that has just been given. A stratum, -though soft or fluid, could not invade the surrounding strata with -violence, nor send out veins to penetrate into them. It might, if, -strongly compressed by another stratum less fluid than itself, fill up -any fissures or cracks that were in that other, but this would hardly -produce, such large veins, and of such considerable length, as often: -penetrate from the granite into the schistus, nor could it give rise -to any appearance of disturbance. If, therefore, veins were found -proceeding from such stratified granite as that of Chorley Forest or -Lammermuir, I should think, that the explanation of them was still a -<i>desideratum</i> in geology. The Neptunian theory of infiltration -would indeed be as applicable to -<span class="pagenum" id="Page_339">- 339 -</span> -them as to any other veins; for it is -but little affected by the condition of the phenomena to be explained. -Indeed, it is very difficult to set any limits to the explanations -which this theory affords; and it would certainly puzzle a Neptunist, -to assign any good reason why infiltration has not produced veins of -one schistus running into another, or veins of schistus running into -granite, as well as of granite running into, schistus. He will find it -a hard task to restrain the activity of his theory, and to confine its -explanations to those things that really exist.</p> - -<p>303. As the Huttonian system cannot boast of theories of equal -versatility, it would be not a little embarrassed to account for veins -of great magnitude proceeding from a rock distinctly stratified, and -accompanied with marks of having disturbed the rocks through which they -pass. I am, however, inclined to believe, that this embarrassment will -never occur; and that the granite veins do not proceed from the rocks -that are really stratified, but from such as have never been deposited -by water, and where the appearances of stratification, if there are -any, are altogether illusory. This anticipation, however, requires to -be verified by future observation; and it remains to be seen, whether -granitic veins ever accompany real granitic strata, or are peculiar to -those in -<span class="pagenum" id="Page_340">- 340 -</span> -which the appearances of regular beds are either ambiguous, -or are entirely wanting. The decision of this question is an object -highly worthy of the attention of geologists.</p> - -<p>304. An argument, directed at once against the igneous origin and -unstratified nature of all granite, is given in a work already -mentioned. "If granite had flowed from below, how does it happen, that, -after it had burst through the strata of micaceous schistus, &c. it did -not overflow the neighbouring country? If this hypothesis were true, -Mont Blanc could never have existed."<a id="FNanchor_156" href="#Footnote_156" class="fnanchor">[156]</a></p> - -<div class="footnote"> - -<p><a id="Footnote_156" href="#FNanchor_156" class="label">[156]</a> Mineralogy of the Scottish Isles, vol. ii. p. 166.</p> - -</div> - -<p>A theory is never more unfairly dealt with, than when those parts -are separated which were meant to support one another, and each left -to stand or fall by itself. This, however, is precisely what is done -in the present instance; for Dr Hutton's theory of granite would -not deserve a moment's consideration, if it were so inartificially -constructed, as to suppose that granite was originally fluid, and yet -to point out no means of hindering this fluid from diffusing itself -over the strata, and settling in a horizontal plane. The truth is, that -his theory, at the same time that it conceives this stone to have -<span class="pagenum" id="Page_341">- 341 -</span> -been in fusion, supposes it to have been, in that state, injected among the -strata already consolidated; to have heaved them up, and to have been -formed in the concavity so produced, as in a mould. Thus Mont Blanc, -supposing that it is unstratified, is understood to consist of a mass -that was melted by subterraneous heat under the strata, and being -impelled upwards by a force, that may stand in some comparison with -that which projected the planets in their orbits, heaved up the strata -by which it was covered, and in which it remained included on all sides.</p> - -<p>305. The covering of strata, thus raised up, may have been burst -asunder at the summit, where the curvature and elevation were the -greatest; but the melted mass underneath may have already acquired -solidity, or may have been sustained by the beds of schistus incumbent -on its sides. This schistus, forming the exterior crust, was -immediately acted on by the causes of waste and decomposition, which -have long since stripped the granite of a great part of its covering, -and are now exercising their power on the central mass. That even Mont -Blanc itself, as well as other unstratified mountains, was once covered -with schistus, will appear to have in it nothing incongruous, when we -consider the height to which the schistus still rises on its sides, -or in the adjacent mountains; -<span class="pagenum" id="Page_342">- 342 -</span> -and when we reflect, that, from the -appearances of waste and degradation which these mountains exhibit, it -is certain, that the schistus must have reached much higher than it -does at present.</p> - -<p>It is obvious, therefore, that when the corresponding parts are brought -together, and placed in their natural order, no room is left for the -reproach, that this system is inconsistent with the <i>existence</i> of -granite mountains. I have no pleasure in controversial writing; and, -notwithstanding the advantages which a weak attack always gives to a -defender, I cannot but regret, that Dr Hutton's adversaries have been -so much more eager to refute than to understand his theory.</p> - -<div class="figcenter" style="width: 156px;"> - <img src="images/bar_blob.png" width="156" height="13" alt="" /> -</div> - -<p>306. A remark which Dr Hutton has made on the quantity of granite that -appears at the surface, compared with that of other mineral bodies, -has been warmly contested. Having affirmed, that the greater part of -rocks bear marks of being formed from the waste and decomposition of -other rocks, he alleges that granite, (a stone which does not contain -such marks) does not, for as much as appears from actual observation, -make up a tenth, nor perhaps -<span class="pagenum" id="Page_343">- 343 -</span> -even a hundredth part of the mineral -kingdom.<a id="FNanchor_157" href="#Footnote_157" class="fnanchor">[157]</a> Mr Kirwan contends, that this is a very erroneous -estimate, and that the quantity of granite visible on the surface, far -exceeds what is here supposed.<a id="FNanchor_158" href="#Footnote_158" class="fnanchor">[158]</a> The question is certainly of no -material importance to the establishment of Dr Hutton's theory: it is -evident, too, that an estimation, which varies so much as from a tenth -to a hundredth part, cannot have been meant as any thing precise; yet -it may not be quite superfluous to show, that the truth probably lies -nearer to the least than the greatest of the limits just mentioned.</p> - -<div class="footnote"> - -<p><a id="Footnote_157" href="#FNanchor_157" class="label">[157]</a> Theory of the Earth, vol. i. p. 211.</p> - -<p><a id="Footnote_158" href="#FNanchor_158" class="label">[158]</a> Geol. Essays, p. 480.</p> - -</div> - -<p>307. Though granite forms a part, generally the central part, of all -the great chains of mountains, it usually occupies a much less extent -of surface than the primary schistus. Thus in the Alps, if a line be -drawn from Geneva to Ivrea, it will be about eighty-five geographical -miles in length, and will measure the breadth of this formidable -chain of mountains, at the place of its greatest elevation. Now, from -the observations of Saussure, who crossed the Alps exactly in this -direction, it may be collected, that less than nine miles of this line, -or not above a tenth part of it, in the immediate vicinity of Mont -Blanc, is occupied by granite.</p> - -<p><span class="pagenum" id="Page_344">- 344 -</span></p> - -<p>308. In some sections of the Alps, no granite at all appears. Thus, in -the route from Chambery to Turin, across Mont Cenis, which measures by -the road not less than ninety miles, no granite is found, at least of -that kind which is distinctly in mass, and different from gneiss or -veined granite.<a id="FNanchor_159" href="#Footnote_159" class="fnanchor">[159]</a></p> - -<div class="footnote"> - -<p><a id="Footnote_159" href="#FNanchor_159" class="label">[159]</a> Voyages aux Alpes, tom. iii. § 1190, &c.</p> - -</div> - -<p>309. In some other places of the same mountains, the granite is more -abundant. A line from the lake of Thun, along the course of the Aar, -and over the mountains to the upper end of Lago Maggiore, crosses a -very elevated tract, and passes by the sources of the Rhone, the Rhine, -and the Tessino, which last runs into the Po. A good deal of granite is -discovered here, in the mountains of Grimsel and St Gothard; but by far -the greater part of it is the veined granite, the granite in mass being -confined chiefly to the north side of the Grimsel. Both together do not -occupy more than one-third of the line, and therefore the latter less -than one-sixth.</p> - -<p>310. The essay on the mineralogy of the Pyrenees, by the Abbé -<span class="smcap">Palasso</span>, contains a mineralogical chart of those mountains. -From this chart I have found, by computation, that the granite does not -occupy one-fifth of the horizontal -<span class="pagenum" id="Page_345">- 345 -</span> surface on the north side of the -ridge, reckoning from one end of it to the other. Indeed, many great -tracts, even of the central parts of the Pyrenees, contain no granite -whatsoever; and not a few of the highest mountains consist entirely of -calcareous schistus. A large deduction should be made from the fraction -1/5 on account of the substances unknown, which, from the construction -of the chart, are often confounded with the granitic tract.</p> - -<p>311. I might add other estimations of the same kind, all confessedly -rude and imperfect, but still conveying, by means of numbers, a better -idea of the limit to which our knowledge approximates, than could be -done simply by words; and, on the whole, it would appear, that if we -state the proportion of granite to schistus to be that of one to four, -we shall certainly do no injustice to the extent of the former.</p> - -<p>It remains to form a rough estimate from maps, and from the accounts -of travellers, of what proportion of the earth's surface consists -of primary, and what of secondary rocks. After supplying the want -of accurate measurement by what appeared to me the most probable -suppositions, I have found, that about 1/18 of the surface of the old -continent may be conceived to be occupied by primitive mountains; of -which, -<span class="pagenum" id="Page_346">- 346 -</span> if we take one-fifth, we have 1/90 for the part of the surface -occupied by granite rocks, which differs not greatly from the least of -the two limits assigned by Dr Hutton.</p> - -<p>312. In estimating the granite of Scotland, Dr Hutton has certainly -erred considerably in defect,<a id="FNanchor_160" href="#Footnote_160" class="fnanchor">[160]</a> and Mr Kirwan, who always differs -from him, is here nearest the truth; though he is right purely by -accident, as the information on which he proceeds is vague and -erroneous.</p> - -<div class="footnote"> - -<p><a id="Footnote_160" href="#FNanchor_160" class="label">[160]</a> Dr Hutton in this case no doubt made a very loose -estimate. He says, the granite does not perhaps occupy more than a -500dth part of the whole surface. The whole surface of Scotland is not -much more than 23,000 geographical miles, the 500dth part of which is -exactly 46; and this is exceeded by the granite in Kirkcudbrightshire -done, as may be gathered from what is said <a href="#sec_283">§ 283</a>.</p> - -</div> - -<p>The places in Scotland where granite is found, are very well known; but -the extent of some of the most considerable of them is not accurately -ascertained. In the southern parts, except the granite of Galloway, -which is found in two pretty large insulated tracts, there is no -other of any magnitude. The granite of the north extends over a large -district. If we suppose a line to be drawn, from a few miles -<span class="pagenum" id="Page_347">- 347 -</span> south -of Aberdeen to a few miles south of Fort William, it will mark out -the central chain of the Grampians in its full extent, passing over -the most elevated ground, and by the heads of the largest rivers, -in Scotland. Along this line there are many granite mountains, and -large tracts in which granite is the prevailing rock. There are, -however, large spaces also in which no granite appears, though, if we -were permitted to speak theoretically, and if the question did not -entirely relate to a matter of observation, we might suppose, that, -in no part of this central ridge is the granite far from the surface, -notwithstanding that in some places it may be covered by the schistus.</p> - -<p>313. A great part of the Grampian mountains is on the south side of the -line just mentioned, but hardly any granite is found in this division -of them, except such veins as those of Glentilt. On the north side of -the line, the granite extends in various directions; and, if from Fort -William a line is drawn to Inverness, the quadrilateral figure, bounded -on two sides by these lines, and on the other two by the sea, will be -found to contain much granite, and many districts consisting entirely -of that stone. This is in fact the great granite country of Scotland: -it is a large tract, containing about 3170 square geographical -miles, or about a seventh -<span class="pagenum" id="Page_348">- 348 -</span> part of the whole: but the proportion of -it occupied by granite cannot at present be ascertained with any -exactness, nor will, till some mineralogist shall find leisure to -examine the courses of the great rivers, the Dee, the Spey, &c. which -traverse this country. If we call it one-fourth of the whole surface, -its extent is certainly not underrated, and will amount to 790 square -miles nearly; to which adding 150, as a very full allowance for all the -other granite contained in Scotland, exclusive of the isles, we shall -have 940 square miles, between a twenty-fourth and twenty-fifth part of -the surface of the whole.</p> - -<p>This computation, it must be observed, aims at nothing precise, but I -think it is such, that a more accurate survey would rather diminish -than increase the proportion assigned in it to the granite rock.</p> - -<p>314. This result may perhaps fall as much short of Mr Kirwan's notion, -as it exceeds the estimate made by Dr Hutton. If it shall not, and if -the former has, in this instance, come nearest the truth, it cannot be -ascribed to the accuracy of his information, or the soundness of the -principles which directed his research. Mr <span class="smcap">Williams</span>, whom he -quotes, was a miner, of great skill and experience in some branches -of his profession, to which, if he had confined himself, he might -have written a book full of useful -<span class="pagenum" id="Page_349">- 349 -</span> information. What he says on the -subject of granite, is, in the main I believe just; but it is far too -general to authorize the conclusion which Mr Kirwan derives from it. -Dr Ash, for whose judgment I have great respect, cannot, I think, have -meant, when he used the expression granitic rocks, to describe granite -strictly so called. He says, in the passage quoted by Mr Kirwan, that -"from Galloway, Dumfries, and Berwick, there is a chain of mountains, -commonly schistose, but often also granitic." Now, the fact is, that -the great belt of primary rock, here alluded to, which traverses the -south of Scotland, consists of vertical schistus of various kinds; -but except in Galloway, and again in Lammermuir, near Priestlaw, it -appears, as already mentioned, to contain no granite whatsoever. If the -German mineralogist quoted by Mr Kirwan, when he says that the Grampian -mountains consist of micaceous limestone, gneiss, porphyry, argillite, -and granite, alternating with one another, means only to affirm that -all these stones are found in the Grampians, he is certainly in the -right, and the catalogue might easily be enlarged; but, if he either -means to say, that these are nearly in equal abundance, or that the -granite is commonly found in strata alternating with other strata, I -must say, that these are propositions -<span class="pagenum" id="Page_350">- 350 -</span> quite contrary to any thing -I have ever seen or heard of those mountains. But it is probable -that this is not meant, and that the fault lies in understanding -the expressions much too literally. Mr Kirwan accuses Dr Hutton of -not knowing where to look for the granite; not aware of how much, -notwithstanding any error committed in the present estimate, he was -skilled in the art of mineralogical observation; an art, which those -who have not practised do not always know how to appreciate. But, -however imperfect Mr Kirwan's knowledge of this subject has been, -he has here had the good fortune to correct a mineralogist of very -superior information. The mere disposition to oppose is not always -without its use: no man is in every thing free from error, and, to -controvert indiscriminately all the opinions of any individual, is an -infallible secret for being sometimes in the right.</p> - - -<hr class="chap x-ebookmaker-drop" /> - -<div class="chapter"> -<h2 class="nobreak" id="Note_xvi"><span class="smcap">Note xvi. § 100.</span></h2> -</div> - -<p class="caption3nb"><i>Rivers and Lakes.</i></p> - - -<p>315. Rivers are the causes of waste most visible to us, and most -obviously capable of -<span class="pagenum" id="Page_351">- 351 -</span> producing great effects. It is not, however, in -the greatest rivers, that the power to change and wear the surface of -the land is most clearly seen. It is at the heads of rivers, and in the -feeders of the larger streams, where they descend over the most rapid -slope, and are most subject to irregular or temporary increase and -diminution, that the causes which tend to preserve, and those that tend -to change the form of the earth's surface, are farthest from balancing -one another, and where, after every season, almost after every flood, -we perceive some change produced, for which no compensation can be -made, and something removed which is never to be replaced. When we -trace up rivers and their branches toward their source, we come at -last to rivulets, that run only in time of rain, and that are dry, at -other seasons. It is there, says Dr Hutton, that I would wish to carry -my reader, that he may be convinced, by his own observation, of this -great; fact, <i>that the rivers have, in general, hollowed out their -valleys</i>. The changes of the valley of the main river are but slow; -the plain indeed is wasted in one place, but is repaired in another, -and we do not perceive the place from whence the repairing matter has -proceeded. That which the spectator sees here, does not therefore -immediately suggest to him what has been the state of things before -the valley was -<span class="pagenum" id="Page_352">- 352 -</span> hollowed out. But it is otherwise in the valley of the -rivulet; no person can examine it without seeing, that the rivulet -carries away matter which cannot be repaired, except by wearing away -some part of the surface of the place upon which the rain that forms -the stream is gathered. The remains of a former state are here visible; -and we can, without any long chain of reasoning, compare what has been -with what is at the present moment. It requires but little study to -replace the parts removed, and to see nature at work, resolving the -most hard and solid masses, by the continued influences of the sun and -atmosphere.<a id="FNanchor_161" href="#Footnote_161" class="fnanchor">[161]</a> We see the beginning of that long journey, by which -heavy bodies travel from the summit of the land to the bottom of the -ocean, and we remain convinced, that, <i>on our continents, there is no -spot on which a river may not formerly have run</i>.<a id="FNanchor_162" href="#Footnote_162" class="fnanchor">[162]</a></p> - -<div class="footnote"> - -<p><a id="Footnote_161" href="#FNanchor_161" class="label">[161]</a> Theory of the Earth, vol. ii. 294.</p> - -<p><a id="Footnote_162" href="#FNanchor_162" class="label">[162]</a> <i>Ibid.</i> p. 296.</p> - -</div> - -<p>316. The view thus afforded of the operations, in their nascent state, -which have shaped out and fashioned the present surface of the land, -is necessary to prepare us for following them to the utmost extent -of their effects. From these effects, the truth of the proposition, -that rivers have cut and formed, not -<span class="pagenum" id="Page_353">- 353 -</span> the beds only, but the whole of -the valleys, or rather system of valleys, through which they flow, is -demonstrated on a principle which has a close affinity to that on which -chances are usually calculated, <a href="#sec_99">§ 99</a>. In order to conceive rightly -the course of a great river, and the communication subsisting between -the main trunk and its remotest branches, let us take the instance -of the Danube and cast our eyes on one of the maps constructed by -<span class="smcap">Marsigli</span>, for illustrating the natural history of that great -river.<a id="FNanchor_163" href="#Footnote_163" class="fnanchor">[163]</a> When it is considered, that over all the vast and uneven -surface, which reaches from the Alps to the Euxine, and from the -mountains of Crapack to those of Hæmus, a regular communication is kept -up between every point and the line of greatest depression, in which -the river flows, no one can hesitate to acknowledge, that it is the -agency of the waters alone which has opened them a free passage through -all the intricacies of this amazing labyrinth. In effect, suppose this -communication to be interrupted, and that some sudden operation of -nature were to erect a barrier of mountains to oppose the Theise or the -Drave, as they rolled their waters to the Danube. From this what could -possibly result, but the damming up of those rivers till -<span class="pagenum" id="Page_354">- 354 -</span> their waters -were deep, or high enough to find a vent, either under the bases or -over the tops of the opposing ridge. Thus there would be formed immense -lakes and immense cataracts, which, by filling up what was too low, and -cutting down what was too high, would in time restore such a uniform -declivity of surface as had before prevailed. Just so in the times that -are past, whatever may have been the irregularities of the surface at -its first emerging from the sea, or whatever irregularities may have -been produced in it by subsequent convulsions, the slow action of the -streams would not fail in time to create or renew a system of valleys -communicating with one another, like that which we at present behold. -Water, in all circumstances, would find its way to the lowest point; -though, where the surface was quite irregular, it would not do so till -after being dammed up in a thousand lakes, or dashed in cataracts over -a thousand precipices. Where neither of these is the case; and where -the lake and the cataract are comparatively rare phenomena; there we -perceive that constitution of a surface, which water alone, of all -physical agents, has a tendency to produce; and we must conclude, that -the probability of such a constitution having arisen from another -cause, is, to the probability of its -<span class="pagenum" id="Page_355">- 355 -</span> having arisen from the running of -water, in such a proportion as unity bears to a number infinitely great.</p> - -<div class="footnote"> - -<p><a id="Footnote_163" href="#FNanchor_163" class="label">[163]</a> Histoire du Danube, tom. i. tab. 34.</p> - -</div> - -<p>317. The courses of many rivers retain marks that they once consisted -of a series of lakes, which have been converted into dry ground, by the -twofold operation of filling up the bottoms, and deepening the outlets. -This happens, especially, when successive terraces of gravelly and -flat land are found on the banks of a river, <a href="#sec_100">§ 100</a>. Such platforms, or -<i>haughs</i> as they are called in this country, are always proofs -of the waste and <i>detritus</i> produced by the river, and of the -different levels on which it has run; but they sometimes lead us -farther, and make it certain, that the great mass of gravel which forms -the successive terraces on each side of the river, was deposited in -the basin of a lake. If, from the level of the highest terrace, down -to the present bed of the river, all is alluvial, and formed of sand -and gravel, it is then evident, that the space as low as the river now -runs must have been once occupied by water; at the same time, it is -dear, that water must have stood, or flowed as high at least, as the -uppermost surface of the meadow. It is impossible to reconcile these -two facts, which are both undeniable, but by supposing a lake, or body -of stagnant water, to have here occupied a great hollow, (which by us -must be held as one of the original -<span class="pagenum" id="Page_356">- 356 -</span> inequalities of the globe, because -we can trace it no farther back,) and that this hollow, in the course -of ages, has been filled up by the gravel and alluvial earth brought -down by the river, which is now cutting its channel through materials -of its own depositing. There is no great river that does not afford -instances of this, both in the hilly part of its course, and where it -descends first from thence into the plain. Were there room here for the -minuter details of topographical description, this might be illustrated -by innumerable examples.</p> - -<p>318. It is said above, that the water must have run or stood, in -former times, as low as the present bottom of the river; but there is -often clear evidence, that it has run or stood much lower, because the -alluvial land reaches far below the present level of the river. This is -known to hold in very many instances, where it has happened that pits -have been sunk to considerable depths on the banks of large rivers. By -that means, the depth of the alluvial ground, under the present bed of -the river, has been discovered to be great; and from this arises the -difficulty, so generally experienced, of finding good foundations for -bridges that are built over rivers in large valleys, or open plains, -the ground being composed of travelled materials to an unknown depth, -without any thing like the native -<span class="pagenum" id="Page_357">- 357 -</span> or solid strata. In such cases, it -is evident, that formerly the water must have been much lower, as well -as much higher, than its present level, and this is only consistent -with the notion, that the place was once occupied by a deep lake.</p> - -<p>319. If, following the light derived from these indications, we go -back to the time when the river ran above the highest of those levels -at which it has left any traces of its operations, we shall see it -composed of a series of lakes and cataracts, from which, by the -filling up of the one, and the wearing down of the other, the waters -have at length worked out to themselves a quiet and uninterrupted -passage to the ocean. We may, indeed, on good evidence, go back still -farther than the succession of such meadows or terraces, as are above -mentioned, will carry us, and may consider the whole valley, or -trough of the river, as produced by its own operations. The original -inequalities of the surface, and the disposition of the strata, must -no doubt have determined the water courses at first; but this does not -hinder us from considering the rivers as having modified and changed -those inequalities, and as the proximate causes of the shape and -configuration which the surface has now assumed.</p> - -<p>320. From this gradual change of lakes into rivers, it follows, that -a lake is but a temporary and accidental condition of a river, which -is -<span class="pagenum" id="Page_358">- 358 -</span> every day approaching to its termination; and the truth of this is -attested, not only by the lakes that have existed, but also by those -that continue to exist. Where any considerable stream enters a lake, -a flat meadow is usually observed increasing from year to year. The -soil of this meadow is disposed in horizontal strata: the meadow is -terminated by a marsh; which marsh is acquiring solidity, and is soon -to be converted into a meadow, as the meadow will be into an arable -field. All this while the sediment of the river makes its way slowly -into the lake, forming a mound or bank under the surface of the water, -with a pretty rapid slope toward the lake. This mound increases by the -addition of new earth, sand, and gravel, poured in over the slope; and -thus the progress of filling up continually advances.</p> - -<p>321. In small lakes, this progress may easily be traced; and will be -found singularly conspicuous in that beautiful assemblage of lakes, -which so highly adorns the mountain scenery of Westmoreland and -Cumberland. Among these a great number of instances appear, in which -lakes are either partially filled up, or have entirely disappeared. In -the Lake of Keswick, we not only discover the marks of filling up at -the upper end, which extend far into Borrowdale, from which valley a -small river flows into the lake; but we have the clearest proof, that -this lake was once -<span class="pagenum" id="Page_359">- 359 -</span> united to that of Bassenthwaite, and occupied the -whole valley from Borrowdale to Ouse-Bridge. These two lakes are at -present joined only by a stream, which runs from the former into the -latter, and their continuity is interrupted by a considerable piece of -alluvial land, composed of beds of earth and gravel, without rock, or -any appearance of the native strata. This separation, therefore, seems -no other than a <i>bar</i>, formed by the influx of two rivers, that -enter the valley here from opposite sides, the Greata from the east, -and Newland's water from the west. The surface of this meadow is at -present twelve or fifteen feet at least above the level of either lake -and a quantity of water of that depth must therefore have been drawn -off by the deepening of the issue at Ouse-Bridge, through which the -water of both lakes passes, in its way to the ocean.</p> - -<p>Many more examples, similar to this, may be collected from the same -lakes; there are indeed few places from which, in this branch of -geology, more information may be collected.</p> - -<p>322. The larger lakes exemplify the same progress. Where the Rhone -enters the Lake of Geneva, the beach has been observed to receive an -annual increase; and the Portus Valesiæ, now Port Valais, which is at -present half a league from the lake, was formerly close upon its bank. -Indeed, the sediments of the Rhone appear clearly to -<span class="pagenum" id="Page_360">- 360 -</span> have formed the -valley through which it runs, to a distance of about three leagues at -least from the place where the river now discharges itself into the -lake. The ground there is perfectly horizontal, composed of sand and -mud, little raised above the level of the river, and full of marshes. -The deposition made by the Rhone after it enters the lake, is visible -to the eye; and may be seen falling down in clouds to the bottom.</p> - -<p>The great lakes of North America are undergoing the same changes, and, -it would seem, even with more rapidity. As the rivers, however, which -supply these vast reservoirs, are none of them very great, the filling -up is much less remarkable than the draining off of the water, by the -deepening of the outlet. An intelligent traveller has remarked, that -in Lake Superior itself the diminution of the waters is apparent, -and that marks can be discovered on the rocks, of the surface having -been six feet higher than it is at present. In the smaller lakes this -diminution is still more evident.<a id="FNanchor_164" href="#Footnote_164" class="fnanchor">[164]</a> In some of those far inland, the -ground all round appeared to the same traveller to be the deposit from -the rivers, of which the lakes themselves may be considered as a mere -expansion.<a id="FNanchor_165" href="#Footnote_165" class="fnanchor">[165]</a></p> - -<div class="footnote"> - -<p><a id="Footnote_164" href="#FNanchor_164" class="label">[164]</a> Mackenzie's Voyages through the Continent of North -America to the Frozen and Pacific Oceans, p. xlii. and xxxvi.</p> - -<p><a id="Footnote_165" href="#FNanchor_165" class="label">[165]</a> <i>Ibid.</i> p. 122.</p> - -</div> - -<p><span class="pagenum" id="Page_361">- 361 -</span></p> - -<p>323. In order to give uniform declivities to the rivers, the lakes -must not only be filled up or drained, but the cataract, wherever -there is one, must be worn away. The latter is an operation in all -cases visible. The stream, as it precipitates itself over the rocks, -hurries along with it, not only sand and gravel, but occasionally large -stones, which grind and wear down the rock with a force proportioned -to their magnitude and acceleration. The smooth surface of the rocks -in all waterfalls, their rounded surface, and curious excavations, -are the most satisfactory proofs of the constant attrition which they -endure; and, where the rocks are deeply intersected, these marks -often reach to a great height above the level on which the water now -flows. The phenomena, in such instances, are among the arguments best -calculated to remove all incredulity respecting the waste which rivers -have produced, and are continuing to produce. They suffer no doubt to -remain, that the height and asperity of every waterfall are continually -diminishing; that innumerable cataracts are entirely obliterated; that -those which remain are verging toward the same end, and that the Falls -of Montmorenci and Niagara must ultimately disappear.</p> - -<p>324. Though there can be no doubt of the justness of the preceding -conclusions, when applied -<span class="pagenum" id="Page_362">- 362 -</span> to lakes in general, some apparent -exceptions occur, in which the progress of draining and filling up -seems to have been suspended, or even to have gone in a contrary -direction. These exceptions consist of the lakes which appear to -have received a greater quantity of materials than was sufficient to -have filled them up. Such, for example, is the Lake of Geneva, which -receives the Rhone descending from the Valais, one of the deepest and -longest valleys on the surface of the earth. Now, if this valley, or -even a large proportion of it, had been excavated by the Rhone itself, -as our theory leads us to suppose, the lake ought to have been entirely -filled up, because the materials brought down by the river seem to be -much greater than the lake, on any reasonable supposition concerning -its original magnitude, can possibly have received. What, then, it -may be said, has become of all that the Rhone has brought down and -deposited in it? The lake, at this moment, retains, in some places, the -depth of more than 1000 feet; and yet, of all that the Rhone carries -into it, nothing but the pure water issues. If it has been continuing -to diminish, both in superficial extent and in depth, from the time -when the Rhone began to run into it, what must have been its original -dimensions?</p> - -<p><span class="pagenum" id="Page_363">- 363 -</span></p> - -<p>I cannot pretend to remove entirely the difficulty which is here -stated; yet I think the following remarks may go some length in doing -so.</p> - -<p><a id="sec_325"></a>325. It is certain, that from the present state of the Lake of Geneva, -and of the ground round it, we can hardly draw any inference as to its -original dimensions. Saussure has traced, with his usual skill, the -marks of the course of the Rhone, on a level greatly above the present; -and, by observations on the side of Mont Saleve, has found proofs of -the running of water, at least 200 toises above the present superficies -of the lake. But, if ever the superficies of the lake stood at this -height, or at this height nearly, though we can conjecture but little -concerning the state of the adjacent country, which no doubt was also -on a higher level, the lake may very well be supposed to have been of -far greater dimensions than it is now. It may have occupied the whole -space from Jura to Saleve, and included the Lake of Neufchâtel; so -that it may have been of magnitude sufficient to receive the spoils of -the Valais, which, as the surface of its waters lowered, may have been -washed away and carried down to the sea. Thus it may have afforded a -temporary receptacle for the <i>debris</i> of the Alps, and may have -served for an <i>entrepot</i>, as it were, where those <i>debris</i> -were -<span class="pagenum" id="Page_364">- 364 -</span> deposited, before they were carried to the place of their -ultimate destination.</p> - -<p>326. But the great depth which the lake has at present, still remains -to be explained, because no mud or gravel could be carried beyond the -gulf, of a thousand feet deep, which was here ready to receive it. The -reality of this difficulty must be acknowledged; and some cause seems -to act, if not in the generation, yet certainly in the preservation of -lakes, with which we are but little acquainted We can indeed imagine -some causes of that kind to occur in the course of the degradation -of the land, which may produce new lakes, or increase the dimensions -of the old. The wearing away of a stratum, or body of strata, may -lay bare, and render accessible to the water, some beds of mineral -substances soluble in that fluid. The district, for instance, in -Cheshire, which contains rock-salt, extends over a tract of fourteen or -fifteen miles, and is covered by a thick stratum of clay, more or less -indurated, which defends the salt from the water at the surface, and -preserves the whole mass in a state of dryness. Should this covering be -broke open by any natural convulsion, or should it be worn away, as it -must be in the progress of the general detritus, the water would gain -admission to the saline strata, -<span class="pagenum" id="Page_365">- 365 -</span> would gradually dissolve them, and -form of course a very deep and extensive lake, where all was before dry -land. This event is not only possible, but it should seem, that in the -course of things it must necessarily happen.</p> - -<p>327. Something of this kind may have taken place in the track of the -Rhone, and may have produced the Leman Lake. It is not impossible, -that, at a very remote period, the Rhone descended from the Alps -without forming any lake, or at least any lake of which the remains are -now existing; and this supposition, which is more probable than that of -<a href="#sec_325">§ 325</a>, we shall soon find to be conformable to appearances of another -kind. The river may have wore away the secondary limestone strata over -which it took its course after it left the schistus of the mountains; -and, in doing so, may have reached some stratum of a saline nature, and -this being washed out, may have left behind it a lake, which is but -modern compared with many of the revolutions that have happened on the -surface of the earth.<a id="FNanchor_166" href="#Footnote_166" class="fnanchor">[166]</a></p> - -<div class="footnote"> - -<p><a id="Footnote_166" href="#FNanchor_166" class="label">[166]</a> There are salt springs at Bex, near Aigle, about ten -miles from the head of the lake: saline strata, therefore, are probably -at no great distance.</p> - -</div> - -<p>This explanation is no doubt hypothetical; but it is proposed in one -of those cases, in -<span class="pagenum" id="Page_366">- 366 -</span> which hypothetical reasonings are warranted by -the strictest rules of philosophical investigation. It is proposed -in a case, where the causes visible to man seem inadequate to the -effect, and where we must therefore have recourse to an agent that is -invisible. If the operations ascribed to this agent are conformable to -the analogy of nature, it is all that can in reason be required.</p> - -<p>328. Another circumstance may also influence the generation and -preservation of lakes; but it is also one with which we are but little -acquainted. The strata, and indeed the whole body of mineral substances -which forms the basis of our land, have been raised up from the bottom -of the sea, by a progress that should seem in general to have been -gradual and slow. Appearances, however, are not wanting, which show, -that this progress is not uniform; and that both rising and sinking in -the surface of the land, or in the rocks which are the base of it, have -happened within a period of time, which is by no means of great extent. -In this progress, the elevations and depressions may not be the same -for every spot. They may be partial, and one part of a stratum, or body -of strata, may rise to a greater height, or be more depressed, than -another. It is not impossible, that this process may affect the depth -of -<span class="pagenum" id="Page_367">- 367 -</span> lakes, and change the relative level of their sides and bottom.</p> - -<p>329. All lakes, however, do not involve the difficulty which the -preceding conjectures are intended to remove. The great lakes of North -America do not, for instance, receive their supply from very large -rivers. Of course, it is not from a tract great in comparison of -themselves, that the waste and detritus is brought down into them; and -it seems not at all wonderful, that, without being filled up, they have -been able to receive it. The same, in a degree at least, is true of -many other lakes.</p> - -<p>It should also be considered, that we may err greatly in the estimate -we make of the materials actually carried down and deposited in any -lake. To judge of their entire amount, we should know the original -form of the inequalities on the earth's surface; of the quantity of -depression which existed, independently of the rivers; and though, -in general, these original inequalities may be overlooked, and the -present considered as made by the running of water, yet, in particular -instances, this may be far from true. The Valais, for example, which -we consider as the work of the Rhone, may, when the Alps rose out of -the sea, have included many depressions of the surface, which the river -joined together, and, from being a series of lakes, formed into one -great valley. -</p> - -<p><span class="pagenum" id="Page_368">- 368 -</span></p> - -<div class="figcenter" style="width: 156px;"> - <img src="images/bar_blob.png" width="156" height="13" alt="" /> -</div> - -<p>330. The mouths by which rivers on bold rocky coasts discharge their -waters into the sea, afford a very striking confirmation of the -conclusions concerning the general system of waste and degradation -which have been drawn above. At these mouths we usually see, not only -the bed of the river, but frequently a considerable valley, cut out -of the solid rock, while that rock preserves its elevation, and its -precipitous aspect, wherever it is not intersected by a run of water. -No convulsion that can have torn asunder the rocks; no breach that can -have been made in them, antecedent to the running of the waters, will -account for the circumstance of every river finding a corresponding -opening, by which it makes its way to the sea; for that opening being -so nearly proportional to the magnitude of the river, and for such -breaches never occurring but where streams of water are found.</p> - -<p>331. The actual survey of any bold and rocky coast, will make this -clearer than any general statement can possibly do. Let us take, for an -example, the coast of the British Channel, from Torbay to the Land's -End, which is faced by a continued rampart of high cliffs, formed -of much indurated and primeval rock. If we consider the breaches in -this rampart, at the mouths -<span class="pagenum" id="Page_369">- 369 -</span> of the Dart, of the Plym and Tamer, of -the river at Fowey, of the Fal, the Hel, &c. it will appear perfectly -clear, that they have been produced by their respective streams. Where -there is no stream, there is no breach in the rock, no softening in -the bold and stern aspect which this shore every where presents to the -ocean. If we look at the smaller streams, we find them working their -way through the cliffs at the present moment; and we see the steps by -which the larger valleys of the Dart and the Tamer have been cut down -to the level of the sea. If we would have still clearer evidence, that -no breaches made antecedently to the running of the rivers have opened -a way for them, we need only look to the opposite side, or northern -shore, of the same promontory, where we also find a series of outlets, -all originating in the ridge of the country, and becoming deeper as -they approach the sea, but altogether unconnected with the openings -on the south side; and this could hardly have been the case, had they -been the effects of previous concussions, or of any peculiarity in the -original structure of the rocks.</p> - -<p>332. In contemplating such coasts as these, when we go back to the -time when the rivers ran upon a level as high as the highest of the -cliffs on the sea shore, we must suppose, that the land then extended -many miles farther into what is -<span class="pagenum" id="Page_370">- 370 -</span> now occupied by the sea. When at -Plymouth, for instance, the Tamer and the Plym flowed on the level of -Mount Edgecombe or of Staten Heights, if the rivers ran with a moderate -declivity into the sea, the coast must have advanced many miles beyond -its present line. Thus the land, when higher, was also more extended, -and the limits of our island in that ancient state, were doubtless very -different from these by which it is at present circumscribed.</p> - -<p>If with the same views we consider any other of the bold coasts which -the map of the world presents us with, we shall quickly remark, that -wherever a deep intersection of the sea is made into the land, as on -the western shores of our own island, or on those of Norway, a river -runs in at the head of it, and points out by what means such inlets -are formed, viz. by the united powers of the sea and of the land, the -waters of the latter having opened the way by which those of the former -have penetrated so far into the country.</p> - -<p>333. It is not meant assuredly to deny the irregularities of the sea -coast, as it may have originally existed; these irregularities no doubt -determined the initial operations of that waste and decay, by which, in -process of time, they were themselves entirely effaced. The line of -<span class="pagenum" id="Page_371">- 371 -</span> -our coasts may be compared to one of those curves, which are sometimes -treated of in the higher geometry, where the ordinates are functions, -not only of, their abscissæ, but also of the time elapsed since a -certain epocha. The form of the curve at that epocha, or when the time -began to flow, corresponds to the original form of the sea coast, on -its emerging from the ocean, and before the powers of wasting and decay -had begun to act upon it. To speak strictly, the original figure, in -both cases, influences all the subsequent; but the farther removed from -it in point of time, the less is that influence; so that, in physical -questions, and for the purpose of such approximations as suit the -imperfection of our knowledge, the consideration of the original figure -may be wholly left out.</p> - - -<hr class="chap x-ebookmaker-drop" /> - -<div class="chapter"> -<h2 class="nobreak" id="Note_xvii"><span class="smcap">Note xvii. § 105.</span></h2> -</div> - -<p class="caption3nb"><i>Remains of Decomposed Rocks.</i></p> - - -<p>334. <span class="smcap">The</span> plain of Crau was the <i>Campus Lapideus</i> of the -ancients; and, as mythology always seeks to connect itself with the -extraordinary facts in natural history, it was said to be the spot -where Hercules, fighting with the sons -<span class="pagenum" id="Page_372">- 372 -</span> of Neptune, and being in want -of weapons, was supplied from heaven by a shower of stones: hence it -was called <i>Campus Herculeus</i>.</p> - -<p>This plain is on the east side of the Rhone, between Salon and Aries: -it is of a triangular form, about twenty square leagues in extent, and -is covered almost entirely with quartzy gravel. This immense collection -of gravel has been supposed by some to have been brought down by the -Durance from the Alps of Dauphine; by others it has been ascribed to -the Rhone; and by many to the sea, as being a work too great for any -river. The explanation mentioned above, <a href="#sec_105">§ 105</a>, namely, that the loose -gravel on the plain arises from the decomposition of a great stratum -of pudding-stone, which is the basis of the whole, is the opinion of -Saussure, and is founded on his own observations.<a id="FNanchor_167" href="#Footnote_167" class="fnanchor">[167]</a></p> - -<div class="footnote"> - -<p><a id="Footnote_167" href="#FNanchor_167" class="label">[167]</a> See Voyages aux Alpes, tom. iii. § 1592 et 1597. See -also on this subject a Memoir by Lamanon, Journal de Physique, tom. -xxii. p. 477; and another by M. De Servieres, <i>ibid.</i> p. 270.</p> - -</div> - -<p>335. The theories that have been contrived for explaining the -phenomena of the plain of Crau, afford an instance of the necessity -of generalizing our observations before we can explain a particular -appearance: in other words, they prove -<span class="pagenum" id="Page_373">- 373 -</span> the truth of Lord Bacon's -maxim, That the explanation of a phenomenon should not be sought for -from the study of that phenomenon alone, but from the comparison of it -with others. One of the theories of this plain is, that the breccia, -which is the base of it, is formed from the consolidation of the loose -gravel of the plain, by water percolating through it, and carrying some -cementing substance along with it, or some <i>lapidific juice</i>, -as it is called. And indeed, whether the gravel is formed from the -breccia, or the breccia from the gravel, is a question which probably -could never be resolved by the mere examination of the plain itself. -But the question is very soon decided, when we compare what is observed -here with other appearances in the natural history of the earth's -surface, and consider how much more frequent the decomposition of -solids is, than their reconsolidation, in any place above the level of -the sea.</p> - -<p>336. The argument for the decomposition of stony substances which is -afforded by the state of this singular plain, may be confirmed by -the appearances observed in many extensive tracts of land all over -the world, and especially in some parts of Great Britain. The road -to Exeter from Taunton Dean, between the latter and Honiton, passes -over a large heath or down, considerably elevated above the plain of -Taunton. The rock -<span class="pagenum" id="Page_374">- 374 -</span> which is the base of this heath, as far as can be -discovered, is limestone, and over the surface of it large flints, in -the form of gravel, are very thickly spread. There is no higher ground -in the neighbourhood from which this gravel can be supposed to have -come, nor any stream that can have carried it, so that no explanation -of it remains, but that it is formed of the flints contained in beds -of limestone, which are now worn away. The flints on the heath are -precisely of the kind found in limestone; many of them are not much -worn, and cannot have travelled far from the rock in which they were -originally contained. It seems certain, therefore, that they are the -<i>debris</i> of limestone strata, now entirely decomposed, that once -lay above the strata which at present form the base of this elevated -plain, and probably covered them to a considerable height. This -explanation carries the greater probability with it, that any other -way of accounting for the fact in question, as the travelling of the -gravel from higher grounds, or the immersion of the surface under -the sea, will imply changes in the face of the country, incomparably -greater than are here supposed. Our hypothesis seems to give the -<i>minimum</i> of all the kinds of change that can possibly account for -the phenomenon.</p> - -<p><span class="pagenum" id="Page_375">- 375 -</span></p> - -<p>337. The same remarks may be made on the high plain of Blackdown, which -the road passes over in going from Exeter to the westward. The flints -there are disseminated over the surface as thickly as in the other -instance, and can be explained only on the same supposition.</p> - -<p>Again, in the interior of England, beginning from about Worcester -and Birmingham, and proceeding north-east through Warwickshire, -Leicestershire, Nottinghamshire, as far as the south of Yorkshire, a -particular species of highly indurated gravel, formed of granulated -quartz, is found every where in great abundance. This same gravel -extends to the west and north-west, as far as Ashburn in Derbyshire, -and perhaps still farther to the north. The quantity of it about -Birmingham is very remarkable, as well as in many other places; and the -phenomenon is the more surprising, that no rock of the same sort is -seen in its native place. It is such gravel as might be expected in a -mountainous country, in Scotland, for instance, or in Switzerland, but -not at all in the fertile and secondary plains of England.</p> - -<p>This enigma is explained, however, when it is observed, that the basis -of the whole tract just described is a red sandstone, often containing -in it a hard quartzy gravel, perfectly similar to that which has just -been mentioned. From -<span class="pagenum" id="Page_376">- 376 -</span> the dissolution of beds of this sandstone, which -formerly covered the present, there can be no doubt that this gravel -is derived. But, as the gravel is in general thinly dispersed through -the sandstone, and abounds only in some of its layers, it should -therefore seem, that a vast body of strata must have been worn away and -decomposed, before such quantities of gravel as now exist in the soil -could have been let loose.</p> - -<p>338. I have said, that a rock capable of affording such gravel as -this, is not to be found in the tract of country just mentioned. -This however, is not strictly true; for in Worcestershire, between -Bromesgrove and Birmingham, about seven miles from the latter, a rock -is found consisting of indurated strata, greatly elevated, and without -doubt primitive, from the detritus of which such gravel as we are -now speaking of might be produced. These strata seem to rise up from -under the secondary, where they are intersected by the road; and, for -as much as appears, are not of great thickness, so that they cannot -have afforded the materials of this gravel directly, though they may -have done so indirectly, or through the medium of the red sandstone; -that is to say, a primary rock of which they are the remains, may have -afforded materials for the gravel in the sandstone; and this sandstone -may in its turn have afforded the materials -<span class="pagenum" id="Page_377">- 377 -</span> of the present soil, and -particularly the gravel contained in it.</p> - -<p>339. Pudding-stones being very liable to decomposition, have probably, -in most countries, afforded large proportion of the loose gravel now -found in the soil The mountains, or at least hills, of this rock, which -are found in many places, prove the great extent of such decomposition. -Mount Rigi, for instance, on the side of the Lake of Lucerne, is -entirely of pudding-stone, and is 742 toises in height, measured from -the level of the lake. By the descriptions given of it, as well as -of other hills of the same kind in Switzerland, we may, without due -attention, be led to suppose that they are entirely formed of loose -gravel. Even M. Saussure's description is chargeable with this fault, -though, when attended to, it will be found to contain a sufficient -proof, that this hill is composed of real pudding-stone.<a id="FNanchor_168" href="#Footnote_168" class="fnanchor">[168]</a> The -nature of the thing also, would be sufficient to convince us, that a -hill, more than 4000 feet in height, could not consist of loose and -unconsolidated materials.</p> - -<p>If, then, we regard Mount Rigi as the remains of a body of -pudding-stone strata, we must conclude, that these strata were -originally more extensive, and the adjacent valleys and plains will -<span class="pagenum" id="Page_378">- 378 -</span> -serve, in some degree, to measure the quantity of them which time has -destroyed.</p> - -<div class="footnote"> - -<p><a id="Footnote_168" href="#FNanchor_168" class="label">[168]</a> Voyages aux Alpes, tom. iv. § 1941.</p> - -</div> - -<p>340. If the theory of unstratified mountains, namely those of -whinstone, porphyry, and granite, be admitted as laid down above, it -will furnish a measure of the destruction which has taken place in the -stratified rocks, and of the vast depredations which have been made -upon them since they were raised up from the bottom of the sea. Like -every other measure, however, of wasting, by a thing that is itself -subject to waste, it can only give a <i>minimum</i>, or a limit which -the quantity wasted must necessarily exceed.</p> - -<p>The abrupt face of a whinstone rock must be understood as an evidence, -that some body of strata which supported it when fluid, remained -in contact with it, when it was become solid; and if this part of -the mould in which the whinstone was cast, has disappeared, it must -generally be ascribed to the operation of waste and decomposition. Such -a face, for instance, as that which Salisbury <i>Craig</i> presents to -the west, viz. a perpendicular wall of whinstone, about ninety feet -high, raised on a body of sandstone strata of the height of about -300 feet, can have been produced only by having been abutted against -some stratified rock, equally abrupt, -<span class="pagenum" id="Page_379">- 379 -</span> and of the same elevation with -itself. Of this rock no part remains.</p> - -<p>The basaltic rock of Edinburgh Castle is nearly in the same state. Its -perpendicular sides on the south, west, and north, are now disengaged -from the strata by which they were once encompassed.</p> - -<p>341. The granite mountains also, where they are quite unstratified, -give rise to the same conclusion. Those central chains which we find -in so many instances towering above the schistus which cover their -sides, have probably been once completely enveloped by the latter; -and, on this supposition, an estimate may sometimes be formed of the -original height of such mountains. In these estimations, however, some -uncertainty must arise, from our being unable to distinguish between -the effects which are to be ascribed to the fracture and dislocation -that took place when the compound body of stratified and unstratified -rocks was raised up from the bottom of the sea, and the effects -produced by the subsequent waste and decomposition at the surface. In -this, as in many other instances, we are not always able to separate -between the original inequalities of the surface, and those which -wearing has produced.</p> - -<p>342. It would be important to ascertain the rate at which the elevation -of mountains decreases, and -<span class="pagenum" id="Page_380">- 380 -</span> this is what we may perhaps expect to -be accomplished, by the progress of geological science, and the -multiplying of accurate observations. It has been supposed, that the -Pyrenees diminish about ten inches in a century; but what confidence is -to be put in this estimate, I am unable to determine.<a id="FNanchor_169" href="#Footnote_169" class="fnanchor">[169]</a></p> - -<div class="footnote"> - -<p><a id="Footnote_169" href="#FNanchor_169" class="label">[169]</a> Essai sur la Mineralogie des Pyrenées, p. 87.</p> - -</div> - -<p>A very unequivocal mark of the degradation of mountains is often to -be met with in the heaps of loose stones found on their tops. These -stones, it is obvious, cannot have come from any other place by natural -means, and they are accordingly always sharp and angular, and have none -of the characters of transported rocks. They are said sometimes to -have been brought by men's hands; but this is highly improbable, their -quantity is often so considerable, and the difficulty of transportation -so great. Where any purpose was to be served by heaping them together, -men have availed themselves of the stones that they found ready -prepared on the summit, and have constructed from them cairns, which -have served as signals, useful in their pastoral, and sometimes in -their military occupations.</p> - - -<hr class="chap x-ebookmaker-drop" /> - -<div class="chapter"> -<p><span class="pagenum" id="Page_381">- 381 -</span></p> - -<h2 class="nobreak" id="Note_xviii"><span class="smcap">Note xviii. § 112.</span></h2> -</div> - -<p class="caption3nb"><i>Transportation of Stones, &c.</i></p> - - -<p>343. <span class="smcap">Nature</span> supplies the means of tracing with considerable -certainty the migration of fossil bodies on the surface of the -earth, as only the more indurated stones, and those most strongly -characterized, can endure the accidents that must befal them in -travelling to a distance from their native place.</p> - -<p>It is a fact very generally observed, that where the valleys among -primitive mountains open into huge plains, the gravel of those plains -consists, of stones, evidently derived from the mountains. The nearer -that any spot is to the mountains, the larger are the gravel stones, -and the less rounded is their figure; and, as the distance increases, -this gravel, which often forms a stratum nearly level, is covered -with a thicker bed of earth or vegetable soil. This progression has -particularly been observed in the valleys of Piémont and the plains of -Lombardy, where a bed of gravel forms the basis of the soil, from the -foot of the Alps to the shores of the Hadriatic.<a id="FNanchor_170" href="#Footnote_170" class="fnanchor">[170]</a><span class="pagenum" id="Page_382">- 382 -</span> We may collect -from <span class="smcap">Guettard</span>, that a similar gradation is found in the gravel -and earth which cover the great plain of Poland, from Mount Krapack to -the Baltic.<a id="FNanchor_171" href="#Footnote_171" class="fnanchor">[171]</a> The reason of this gradation is evident; the farther -the stones have travelled, and the more rubbing they have endured, the -smaller they grow, the more regular is the figure they assume, and the -greater the quantity of that finer detritus which constitutes the soil. -The washing of the rains and rivers is here obvious; and each of the -three quantities just mentioned, if not directly proportional to the -distance which the stones have migrated from their native place, may -be said, in the language of geometry, to be at least proportional to a -certain function of that distance.</p> - -<div class="footnote"> - -<p><a id="Footnote_170" href="#FNanchor_170" class="label">[170]</a> Voyages aux Alpes, tom. iii. § 1315.</p> - -<p><a id="Footnote_171" href="#FNanchor_171" class="label">[171]</a> Mém. Acad. des Sciences, 1762, p. 234, 293, &c.</p> - -</div> - -<p>344. The immense quantity of <i>cailloux roulés</i>, or rounded -gravel, collected in the immediate vicinity of mountainous tracts, -has led some geologists to suppose the existence of ancient currents, -which descended from the mountains, in a quantity, and with a -<i>momentum</i>, of which there is no example in the present state -of the world. Thus Saussure imagines, that the hill of Supergue, -near Turin, which is formed of gravel, can only be explained by -supposing such currents -<span class="pagenum" id="Page_383">- 383 -</span> as are just mentioned, or what he terms a -<i>debacle</i>, to have taken place at some former period.<a id="FNanchor_172" href="#Footnote_172" class="fnanchor">[172]</a> If, -however, we ascribe to the mountains a magnitude and elevation vastly -greater than that which they now possess; if we regard the valleys -between them as cut out by the rivers and torrents from an immense -rampart of solid rock, neither materials sufficiently great, nor agents -sufficiently powerful, will appear to be wanting, for collecting bodies -of gravel and other loose materials, equal to any that are found on the -surface of the earth. The necessity of introducing a <i>debacle</i>, or -any other unknown agent, to account for the transportation of fossils, -seems to arise from underrating the effects of action long continued, -and not limited by such short periods as circumscribe the works, and -even the observations, of men.</p> - -<div class="footnote"> - -<p><a id="Footnote_172" href="#FNanchor_172" class="label">[172]</a> Voyages aux Alpes, tom. iii. § 1303.</p> - -</div> - -<p>345. The supply of gravel and <i>cailloux roulés</i>, for the plains -extended at the feet of primitive mountains, is doubtless in many cases -much increased by the pudding-stone, interposed between the secondary -and the primary strata. The beds of pudding-stone contain gravel -already formed on the shores of continents, that ceased to exist before -the present were produced; and the cement of -<span class="pagenum" id="Page_384">- 384 -</span> this gravel, yielding -easily to the weather, allows the stones included in it to be washed -down by the torrents, and scattered over the plains. I know not if -the hill of Supergue above mentioned, is not in reality a mass of the -pudding-stone which forms the border of the Alps, and of which the -materials have suffered no transportation since the time of their last -consolidation. This at least is certain, that Saussure, notwithstanding -his accuracy, has sometimes confounded the loose gravel on the surface -with that which is consolidated into rock; an inaccuracy which is to be -charged, as I have elsewhere observed, rather against his system than -himself.</p> - -<p>346. The loose stones found on the sides of hills, and the bottoms -of valleys, when traced back to their original place, point out with -demonstrative evidence the great changes which have happened since the -commencement of their journey; and in particular serve to show, that -many valleys which now deeply intersect the surface, had not begun to -be cut out when these stones were first detached from their native -rocks. We know, for instance, that stones under the influence of such -forces as we are now considering, cannot have first descended from one -ridge, and then ascended on the side of an opposite ridge. But the -granite -<span class="pagenum" id="Page_385">- 385 -</span> of Mont Blanc has been found, as mentioned above, on the sides -of Jura, and even on the side of it farthest from the Alps. Now, in -the present state of the earth's surface, between the central chain of -the Alps, from which these pieces of granite must have come, and the -ridge of Mont Jura, besides many smaller valleys, there is the great -valley of the Rhone, from the bottom of which, to the place where they -now lie, is a height of not less than 3000 feet. Stones could not, by -any force that we know of, be made to ascend over this height. We must -therefore suppose, that when they travelled from Mont Blanc to Jura, -this deep valley did not exist, but that such an uniform declivity, as -water can run on with rapidity, extended from the one summit to the -other. This supposition accords well with what has been already said -concerning the recent formation of the Leman Lake, and of the present -valley of the Rhone.</p> - -<p>347. We can derive, in a matter of this sort, but little and from -calculation; yet we may discover by it, whether our hypothesis -transgresses materially against the laws of probability, and is -inconsistent with physical principles already established. The -horizontal distance from Mont Jura to the granite mountains, at the -head of the Arve, may be accounted fifty geographic -<span class="pagenum" id="Page_386">- 386 -</span> miles. Though -we suppose Mont Blanc, and the rest of those mountains, to have been -originally much higher than they are at present, the ridge of Jura must -have been so likewise; and though probably not by an equal quantity, -yet it is the fairest way to suppose the difference of their height to -have been nearly the same in former ages that it is at present, and -it may therefore be taken at 10,000 feet. The declivity of a plane -from the top of Mont Jura to the top of Mont Blanc, would therefore be -about one mile and three quarters in fifty, or one foot in thirty; an -inclination much greater than is necessary for water to run on, even -with extreme rapidity, and more than sufficient to enable a river or -a torrent to carry with it stones or fragments of rock, almost to any -distance.</p> - -<p>Saussure, in relating the fact that pieces of granite are found among -the high passes near the summits of Mont Jura, alleges, that they are -only found in spots from which the central chain of the Alps may be -seen. But it should seem that this coincidence is accidental, because, -from whatever cause the transportation of these blocks has proceeded, -the form of the mountains, especially of Mont Jura, must be too much -changed to admit of the supposition, that the places of it from which -Mont Blanc is now -<span class="pagenum" id="Page_387">- 387 -</span> visible, are the same from which that mountain was -visible when these stones were transported hither. It may be, however, -that the passes which now exist in Mont Jura are the remains of valleys -or beds of torrents, which once flowed westward from the Alps; and it -is natural, that the fragments from the latter mountains should be -found in the neighbourhood of those ancient water-tracks.</p> - -<p>348. Saussure observed in another part of the Alps, that where the -Drance descends from the sides of Mont Velan and the Great St Bernard, -to join the Rhone in the Valais, the valley it runs in lies between -mountains of primary schistus, in which no granite appears, and yet -that the bottom of this valley, toward its lower extremity, is for -a considerable way covered with loose blocks of granite.<a id="FNanchor_173" href="#Footnote_173" class="fnanchor">[173]</a> His -familiar acquaintance with all the rocks of those mountains, led him -immediately to suspect, that these stones came from the granite chain -of Mont Blanc, which is westward of the Drance, and considerably higher -than the intervening mountains. This conjecture was verified by the -observations of one of his friends, who found the stones in question to -agree exactly with a -<span class="pagenum" id="Page_388">- 388 -</span> rock at the point of Ornes, the nearest part of -the granite chain.</p> - -<div class="footnote"> - -<p><a id="Footnote_173" href="#FNanchor_173" class="label">[173]</a> Voyages aux Alpes, tom. ii. § 1022.</p> - -</div> - -<p>In the present state of the surface, however, the valley of Orsiere -lies between the rocks of Ornex and the valley of the Drance, and would -certainly have intercepted the granite blocks in their way from the one -of these points to the other, if it had existed at the time when they -were passing over that tract. The valley of Orsiere, therefore, was not -formed, when the torrents, or the glaciers transported these fragments -from their native place.</p> - -<p>Mountainous countries, when carefully examined, afford so many facts -similar to the preceding, that we should never have done were we -to enumerate all the instances in which they occur. They lead to -conclusions of great use, if we would compare the machinery which -nature actually employs in the transportation of rocks, with the -largest fragments of rock which appear to have been removed, at some -former period, from their native place.</p> - -<p>349. For the moving of large masses of rock, the most powerful engines -without doubt which nature employs are the glaciers, those lakes or -rivers of ice which are formed in the highest valleys of the Alps, -and other mountains of the first order. These great masses are in -perpetual -<span class="pagenum" id="Page_389">- 389 -</span> motion, undermined by the influx of heat from the earth, and -impelled down the declivities on which they rest by their own enormous -weight, together with that of the innumerable fragments of rock with -which they are loaded. These fragments they gradually transport to -their utmost boundaries, where a formidable wall ascertains the -magnitude, and attests the force, of the great engine by which it was -erected. The immense quantity and size of the rocks thus transported, -have been remarked with astonishment by every observer,<a id="FNanchor_174" href="#Footnote_174" class="fnanchor">[174]</a> and -explain sufficiently how fragments of rock may be put in motion, even -where there is but little declivity, and where the actual surface of -the ground is considerably uneven. In this manner, before the valleys -were cut out in the form they now are, and when the mountains were -still more elevated, huge fragments of rock may have been carried to a -great distance; and it is not wonderful, if these same masses, greatly -diminished in size, and reduced to gravel or sand, have reached the -shores, or even the bottom, of the ocean.</p> - -<div class="footnote"> - -<p><a id="Footnote_174" href="#FNanchor_174" class="label">[174]</a> The stones collected on the <i>Glacier de Miage</i>, -when Saussure visited it, were in such quantity as to conceal the ice -entirely. Voyages aux Alpes, tom. ii. § 854.</p> - -</div> - -<p>350. Next in force to the glaciers, the torrents are the most powerful -instruments employed in -<span class="pagenum" id="Page_390">- 390 -</span> the transportation of stones. These, when -they descend from the sides of mountains, and even where the declivity -of their course is not very great, produce effects which nothing but -direct experience could render credible. The fragments of rock which -oppose the torrent, are rendered specifically lighter by the fluid -in which they are immersed, and lose by that means at least a third -part of their weight: they are, at the same time, impelled by a force -proportional to the square of the velocity with which the water rushes -against them, and proportional also to the quantity of gravel and -stones which it has already put in motion. Perhaps, after taking all -these circumstances into computation, in the midst of a scene perfectly -quiet and undisturbed, a philosopher might remain in doubt as to the -power of torrents to move the enormous bodies of rock which are seen -in the bottom of the narrow valleys or deep glens of a mountainous -country; but his incredulity, says an experienced traveller, will -cease altogether, if he has been surprised by a storm in the midst of -some Alpine region; if he has seen the number and impetuosity of the -cataracts which rushed down the sides of the mountains, and beheld the -ruin which accompanied them; and if, when the tempest was passed, he -has viewed those meadows, -<span class="pagenum" id="Page_391">- 391 -</span> which a few hours before were covered with -verdure, now buried under heaps of stones, or overwhelmed by masses of -liquid mud, and the sides of the mountains cut by deep ravines, where -the track of the smallest rivulet was not before to be discovered.<a id="FNanchor_175" href="#Footnote_175" class="fnanchor">[175]</a></p> - -<div class="footnote"> - -<p><a id="Footnote_175" href="#FNanchor_175" class="label">[175]</a> See an account of a thunder storm near Bareges, in the -Essai sur la Mineralogie des Pyrenées, p. 134.</p> - -</div> - -<p>It is but rarely, however, even on occasions like these, that such -vast masses of rock can be seen actually in motion, as are often found -on the surface, apparently removed to a great distance from their -native place. The magnitude of these is so great, in many instances, -that their transportation cannot be explained without supposing, -that the surface was very different when these transportations took -place from what it is at present; that the elevation of the mountains -was greater, and the ground smoother and more uniform, at least in -some directions. If these suppositions are admitted, and they are -countenanced, as we have already seen, by almost every phenomenon in -geology, the difficulties which present themselves here will not appear -insurmountable.</p> - -<p>351. One of the largest blocks of granite that we know of, is on the -east side of the lake of -<span class="pagenum" id="Page_392">- 392 -</span> Geneva, called <i>Pierre de Gouté</i>, -about ten feet in height, with a horizontal section of fifteen by -twenty.<a id="FNanchor_176" href="#Footnote_176" class="fnanchor">[176]</a> Another block not far from it, and nearly of the same -size, has some remains of schistus attached to it. These stones very -much resemble those which have fallen from the <i>Aiguilles</i>, in the -valley of Chamouni. The distance from their present situation to those -<i>Aiguilles</i> is about thirty English miles, with many mountains -and valleys at present interposed. By whatever means, therefore, these -blocks were transported, their motion must have been over a surface -of much more uniform declivity than the present. If the surface was -without great inequalities, and its general declivity about one foot -in thirty, as already computed, the glaciers, in the first place, and -the torrents afterwards, may have served for the transportation even of -these rocks.</p> - -<div class="footnote"> - -<p><a id="Footnote_176" href="#FNanchor_176" class="label">[176]</a> Voyages aux Alpes, tom. i. § 308.</p> - -</div> - -<p>352. Again, in the narrow vale or glen which separates the Great from -the Little Saleve, the strata are all calcareous, but a great number -of loose blocks of granite and primary schistus are scattered over the -surface. A block of the former, near the lower end of the valley, is -about the size of 1200 cubic feet. Two other large blocks of the same -kind of stone rest on a base of horizontal -<span class="pagenum" id="Page_393">- 393 -</span> limestone, elevated two -or three feet above the rest of the surface. This elevation arises -no doubt from the protection which the stones have afforded to the -calcareous beds on which they lie, so that these beds do not wear away -so fast as those which are fully exposed to the weather. But it is -surely to take a very limited view of the operations on the surface, -to suppose, with Saussure, that the parts of the calcareous rock under -these stones has suffered no waste whatsoever, so that the stones -remain now in the identical spot where they were placed by the great -<i>debacle</i> which brought them down from the high Alps.<a id="FNanchor_177" href="#Footnote_177" class="fnanchor">[177]</a> For -my part, I have no doubt that the Arve, which is still at no great -distance, when it ran on a higher level, and in a line different -from the present, aided by the glaciers and superior elevation of -the mountains, was an engine sufficiently powerful for effecting the -transportation of these stones.</p> - -<div class="footnote"> - -<p><a id="Footnote_177" href="#FNanchor_177" class="label">[177]</a> <i>Ibid.</i> § 227.</p> - -</div> - -<p>353. These phenomena are not peculiar to the Alps, but prevail, in -a greater or less degree, in the vicinity of all primary or granite -mountains. In the island of Arran, a fragment of the same kind with -that which constitutes the upper part of Goatfield, is found on the sea -shore, at least three miles from the nearest granite rock, and -<span class="pagenum" id="Page_394">- 394 -</span> with -a bay of the sea intervening. Its dimensions are not far from those -of the <i>pierre de gouté</i>. In some former state of the granitic -mountains in that island, the declivity from the top of Goatfield may -have been very uniform, and more rapid than it is at present.</p> - -<p>354. Besides glaciers and torrents, which have no doubt been the -principal instruments in producing these changes, other causes -may have occasionally operated. Large stones, when once detached, -and resting on an inclined plane, from the effects of waste and -decomposition, may advance horizontally, at the same time that they -descend perpendicularly, and this will happen though they be not urged -by any torrent, or any thing but their own weight; for the surface -of the ground, as it wastes, remains higher under the stone, and for -a little way round it, than at a greater distance, on account of the -protection which it receives from the stone, as in the instances at -Saleve, just mentioned. The stone itself also becomes rounded at the -bottom; and thus the surface in contact with the ground is diminished -in extent, and the two surfaces rendered convex towards one another. It -must therefore happen, that the support, continually weakening, will at -length give way, and the stone incline or roll toward the lower side, -and may even roll considerably, -<span class="pagenum" id="Page_395">- 395 -</span> if its centre of gravity has been high -above its point of support, and if its surface has had much convexity: -Thus the horizontal may very far exceed the perpendicular motion; -and, in the course of ages, the stone may travel to a great distance. -A stone, however, which travels in this manner, must diminish as it -proceeds, and must have been much greater in the beginning than it is -at present.</p> - -<p>355. This kind of motion may be aided by particular circumstances. -When a stone rests on an inclined plane, so as to be in a state not -very remote from equilibrium, if a part be taken away from the upper -side, the equilibrium will be lost, and the stone will thereby be put -in motion. That stones which lie on other stones, may, by wearing, -be brought very near an equilibrium, is proved by what are called -<i>rocking-stones</i>, or in Cornwall <i>Logan stones</i>, which have -sometimes been mistaken for works of art; but are certainly nothing -else than stones, which have been subjected to the universal law -of wasting and decay, in such peculiar circumstances, as nearly to -bring about an equilibrium of that stable kind, which, when slightly -disturbed, re-establishes itself.<a id="FNanchor_178" href="#Footnote_178" class="fnanchor">[178]</a> The Logan stone at -<span class="pagenum" id="Page_396">- 396 -</span> the Land's -End, is a mass of granite, weighing more than sixty tons, resting -on a rock of granite, of considerable height, and close on the sea -shore. The two stones touch but in a small spot, their surfaces being -considerably convex towards one another. The uppermost is so nearly -in an equilibrium, that it can be made to vibrate by the strength -of a man, though to overset it entirely would require a vast force. -This arises from the centre of gravity of the stone being somewhat -lower than the centre of curvature of that part of it on which it -has a tendency to roll; the consequence of which is, that any motion -impressed on the stone, forces its centre of gravity to rise, (though -not very considerably,) by which means it returns whenever the force -is removed, and vibrates backward and forward, till it is reduced to -rest. Were it required to remove the stone from its place, it -<span class="pagenum" id="Page_397">- 397 -</span> might be -most easily done, by cutting off a part from one side, or blowing it -away by gunpowder; the stone would then lose its balance, would tumble -from its pedestal, and might roll to a considerable distance. Now, what -art is here supposed to perform, nature herself in time will probably -effect. If the waste on one side of this great mass shall exceed that -on the opposite in more than a certain proportion, and it is not likely -that that proportion will be always maintained, the equilibrium of the -Logan stone will be subverted, never to return. Thus we perceive how -motion may be produced by the combined action of the decomposition and -gravitation of large masses of rock.</p> - -<div class="footnote"> - -<p><a id="Footnote_178" href="#FNanchor_178" class="label">[178]</a> I do not presume so far as to say, that all -rocking-stones are produced by natural means: I have not sufficient -information to justify that assertion; but the great size of that -at the Land's End, its elevated position, and the approaches toward -something of the same kind which are to be seen in other parts of that -shore, prove that it is no work of art. They who ascribe it to the -Druids, do not consider the rapidity with which the Cornish granite -wastes, nor think how improbable it is, that the conditions necessary -to a rocking-stone, whether produced by nature or art, should have -remained the same for sixteen or seventeen hundred years.</p> - -</div> - -<p>356. Besides the gradual waste to which stones exposed to the -atmosphere are necessarily subject, those of a great size appear to be -liable to splitting, and dividing into large portions, no doubt from -their weight. This may be observed in almost all stones that happen to -be in such circumstances as we are now considering; and from this cause -the subversion of their balance may be more sudden, and of greater -amount, than could be expected from their gradual decay.</p> - -<p>Thus, if to the wasting of a stone at the bottom, we add the accidents -that may befal it in the wasting of its sides, we see at least the -physical possibility of detached stones being put in -<span class="pagenum" id="Page_398">- 398 -</span> motion, merely -by their own weight. It is indeed remarkable, that some of the largest -of these stones rest on very narrow bases. Those at the foot of -Saleve touch the ground only in a few points: The Boulder stone of -Borrowdale is supported on a narrow ridge like the keel of a ship, and -is prevented from tumbling by a stone or two, that serve as a kind -of shores to prop it up. Very unexpected accidents sometimes happen -to disturb the rest of such fragments of rock as have once migrated -from their own place. Saussure mentions a great mass of <i>lapis -ollaris</i><a id="FNanchor_179" href="#Footnote_179" class="fnanchor">[179]</a> that lies detached on the side of a declivity in the -valley of Urseren, in the canton of Uri. The people use this stone as -a quarry, and are working it away on the upper side, in consequence of -which it will probably be soon overset, and will roll to the bottom of -the valley.</p> - -<div class="footnote"> - -<p><a id="Footnote_179" href="#FNanchor_179" class="label">[179]</a> Voyages aux Alpes, tom. iv. § 1851.</p> - -</div> - -<p>357. In many instances it cannot be doubted, that stones of the kind -here referred to are the remains of masses or veins of whinstone or -granite, now worn away, and that they have travelled but a very short -way, or perhaps not at all, from their original place. Many of the -large blocks of whinstone which we find in this country, sometimes -single, and sometimes scattered -<span class="pagenum" id="Page_399">- 399 -</span> in considerable abundance over a -particular spot, are certainly to be referred to this cause. But the -most remarkable examples of this sort are the stones found at the Cape -of Good Hope, on the hill called <i>Paarlberg</i>, which takes its name -from a chain of large round stones, like the pearls of a necklace, that -passes over the summit. Two of these, placed near the highest point, -are called the Pearl and the Diamond, and were mentioned several years -ago in the Philosophical Transactions.<a id="FNanchor_180" href="#Footnote_180" class="fnanchor">[180]</a> From a more recent account, -these stones appear to be a species of granite, though the hill on -which they lie is composed of sandstone strata.<a id="FNanchor_181" href="#Footnote_181" class="fnanchor">[181]</a> The Pearl is a -naked rock, that rises to the height of 400 feet above the summit of -the hill; the Diamond is higher, but its base is less, and it is more -inaccessible.</p> - -<div class="footnote"> - -<p><a id="Footnote_180" href="#FNanchor_180" class="label">[180]</a> Vol. lxviii. p. 102.</p> - -</div> - -<div class="footnote"> - -<p><a id="Footnote_181" href="#FNanchor_181" class="label">[181]</a> Barrow's Travels into Southern Africa, p. 60.</p> - -</div> - -<p>From the above stones forming a regular chain, as well as from the -immense size of the two largest, it is impossible to suppose that they -have been moved; and it is infinitely more probable, that they are -parts of a granite vein, which runs across the sandstone strata, and -of which some parts have resisted the action of the weather, while the -rest have yielded to it. The -<span class="pagenum" id="Page_400">- 400 -</span> whole geological history of this part of -Africa seems highly interesting, since, as far as can be collected from -the accounts of the ingenious traveller just mentioned, it consists -of horizontal beds of sandstone or limestone, resting immediately on -granite, or on primary schistus. Loose blocks of granite are seen in -great abundance at the foot of the Table Mountain, and along the sea -shore.</p> - -<div class="figcenter" style="width: 156px;"> - <img src="images/bar_blob.png" width="156" height="13" alt="" /> -</div> - -<p>358. The system which accounts for such phenomena as have been -considered in this and some of the preceding notes, by the operation of -a great deluge, or <i>debacle</i>, as it is called, has been already -mentioned. In Dr Hutton's theory, nothing whatever is ascribed to such -accidental and unknown causes; and, though their existence is not -absolutely denied, their effects, whatever they may have been, are -alleged to be entirely obliterated, so that they can be referred to -no other class but that of mere possibilities. A minute discussion, -however, of the question, Whether there are, on the surface of the -earth, any effects that require the interposition of an extraordinary -cause, would lead into a longer digression than is suited to this -place. I shall briefly state what appear to be the principal -<span class="pagenum" id="Page_401">- 401 -</span> -objections to all such explanations of the phenomena of geology.</p> - -<p>359. The general structure of valleys among mountains, is highly -unfavourable to the notion that they were produced by any single great -torrent, which swept over the surface of the earth. In some instances, -valleys diverge, as it were from a centre, in all directions. In -others, they originate from a ridge, and proceed with equal depth and -extent on both sides of it, plainly indicating, that the force which -produced them was <i>nothing</i>, or evanescent at the summit of that -ridge, and increased on both sides, as the distance from the ridge -increased. The working of water collected from the rains and the snows, -and seeking its way from a higher to a lower level, is the only cause -we know of, which is subject to this law.</p> - -<p>360. Again, if we consider a valley as a space, which perhaps with many -windings and irregularities, has been hollowed out of the solid rock, -it is plain, that no force of water, suddenly applied, could loosen -and remove the great mass of stone which has actually disappeared. -The greatest column of water that could be brought to act against -such a mass, whatever be the velocity we ascribe to it, could not -break asunder and displace beds of rock many leagues in length, and -in continuity with -<span class="pagenum" id="Page_402">- 402 -</span> the rock on either side of them. The slow working -of water, on the other hand, or the powers that we see every day in -action, are quite sufficient for this effect, if time only is allowed -them.</p> - -<p>361. Some valleys are so particularly constructed, as to carry with -them a still stronger refutation of the existence of a <i>debacle</i>. -These are the longitudinal valleys, which have the openings by which -the water is discharged, not at one extremity, but at the broadside -Such is that on the east side of Mont Blanc, deeply excavated on the -confines of the granite and schistus rock, and extending parallel to -the beds of the latter, from the Col de la Segne to the Col de Ferret; -its opening is nearly in the middle, from which the Dora issues, and -takes its course through a great valley, nearly at right angles to the -chain of the Alps, and to the valley just mentioned. From the structure -of these valleys, Saussure has argued very justly against Buffon's -hypothesis, concerning the formation of valleys by currents at the -bottom of the sea.<a id="FNanchor_182" href="#Footnote_182" class="fnanchor">[182]</a> It affords indeed a complete refutation of that -hypothesis: and it affords one no less complete of the system which -Saussure himself seems on some occasions so much inclined to support. -For if it be said, that this valley was cut out by the -<span class="pagenum" id="Page_403">- 403 -</span> current of a -<i>debacle</i>, that current must either have run in the direction of -the valley of Ferret, or in that of the Dora, which issues from it. If -it had the direction of the first, it could not cut out the second; -and if it had the direction of the second, it could not cut out the -first. Besides, the force which excavated this valley must have been -<i>nothing</i> at the two extreme points, viz. at the Col de la Segne -and the Col de Ferret, and must have increased with the distance from -each. It can have been produced, therefore, only by the running of two -streams in opposite directions, on a surface that was but slightly -uneven, these streams at meeting taking a new direction, nearly at -right angles to the former. A clearer proof could hardly be required -than is afforded in this case, that what is now a deep valley was -formerly solid rock, which the running of the waters has gradually worn -away; and that the waters, when they began to run, were on a level as -high, at least, as the tops of those mountains by which the valley is -bounded toward the lower side.</p> - -<div class="footnote"> - -<p><a id="Footnote_182" href="#FNanchor_182" class="label">[182]</a> Voyage aux Alpes, tom. ii. § 920.</p> - -</div> - -<p>362. Longitudinal valleys, with the water bursting out transversely -from their sides, like the preceding, are by no means confined to -mountains of the first order. We have a very good example, though -on a small scale, of a valley of this sort, within a few miles of -Edinburgh. -<span class="pagenum" id="Page_404">- 404 -</span> The Pentland Hills form a double ridge, separated by a -small longitudinal valley, that runs from N. E. to S. W., the water of -which issues from an opening almost in the middle, and directed towards -the south. This, therefore, is not the work of any great torrent, which -overwhelmed the country; for no one direction, which it is possible -to assign to such a torrent, will afford an explanation, both of the -valley and its outlet.<a id="FNanchor_183" href="#Footnote_183" class="fnanchor">[183]</a></p> - -<div class="footnote"> - -<p><a id="Footnote_183" href="#FNanchor_183" class="label">[183]</a> In Scotland there is one valley, of a kind that I -believe is extremely rare in any part of the world, in accounting for -which, the hypothesis of a torrent or <i>debacle</i> might, if any -where, be employed to advantage. This is the valley which extends -across the island, from Inverness to Fort William, or from sea to sea, -being open at both ends, and very little elevated in the middle. It is -nearly straight, and of a very uniform breadth, except that towards -each end it widens considerably. The bottom, reckoning transversely, is -flat, without any gradual slope from the sides towards the middle. From -the sides the mountains rise immediately, and form two continued ridges -of great height, like ramparts or embankments on each side of a large -fossé. A great part of the bottom of this singular valley is occupied -by lakes, namely, Loch Ness, Loch Oich, and Loch Lochy. Its length is -about sixty-two miles, and the point of partition from which the waters -run different ways, viz. north-east to the German Ocean, and south-west -to the Atlantic, is between Loch Oich and Loch Lochy; and, by the -estimation of the eye, I should hardly think that it is elevated more -than ten or fifteen feet above the surface of either lake. The country -on both sides is rugged and mountainous, and the streams which descend -from thence into the valley, either fall directly into the lakes, or -turn off almost at right angles when they enter the valley. Though -the bottom of this valley, therefore, is every where alluvial, with -the exception, perhaps, of a few rocks which appear at the surface, -it is certainly not excavated by the rivers which now flow in it. The -direction of the valley, it is to be observed, is the same with that of -the vertical strata which compose the mountain on either side.</p> - -<p>Here, then, we have a valley, not cut out by the working of any streams -which now appear; and we may therefore make trial of the hypothesis of -a <i>debacle</i>. This, however, will afford us no assistance; because, -if we suppose what is now hollow to have been once occupied by the -same kind of rock which is on either side, no force of torrents can -have suddenly loosened and removed from its place a body of such vast -magnitude. A greater column of water, than one having for its base a -transverse section of the valley, could not act against it, and this -would have to overcome the cohesion and inertia of a column of rock -of the same section, and of the length of sixty-two miles. It is not -hazarding much to affirm, that no velocity which could be communicated -to water, not even that which it could acquire by falling from an -infinite height, could give to it a force in any degree adequate to -this great effect.</p> - -<p>The explanation of this valley, which appears to me the most probable, -is the following. It will be shown hereafter, that there is good reason -to suppose, that, in most parts of our island, the relative level of -the sea and land has been in past ages considerably higher than it is -at present. In such circumstances, this valley may have been under -the surface of the sea, the highest part of it being scarcely 100 -feet above that level at present. It may have been a kind of sound, -therefore, or strait, which connected the German Sea with the Atlantic; -and the strong currents, which, on account of the different times -of high water in these two seas, must have run alternately up and -down this strait, may have produced that flatness of the bottom, and -straightness of the sides, and that widening at the extremities, which -are mentioned above. In this way, too, some difficulties are removed -relative to Loch Ness, which is so deep as hardly to be consistent with -the indefinite length of the period of waste that must be ascribed to -the mountains on each side of it. Its depth is said, where greatest, -not to be less than 180 fathoms. According to this hypothesis, it may, -at no very distant period, have been a part of the bottom of the sea.</p> - -</div> - -<p><span class="pagenum" id="Page_405">- 405 -</span></p> - -<p>363. They who maintain the existence of the <i>debacle</i>, will no -doubt allege, that though these -<span class="pagenum" id="Page_406">- 406 -</span> valleys were not cut out by means of -it, yet others may. But it must be recollected, that if -<span class="pagenum" id="Page_407">- 407 -</span> some of the -greatest and deepest valleys on the face of the earth, such as that -just mentioned, on the east side of Mont Blanc, are thus shown to be -the work of the daily wasting of the surface, what other inequalities -can be great enough to require the interposition of a more powerful -cause? If a <i>dignus vindice nodus</i> does not exist here, in what -part of the natural history of the earth is it likely to be found?</p> - -<p>364. The large masses of rock so often met with at a distance -from their original place, are one of the arguments used for the -<i>debacle</i>. It has, however, been shown, that, supposing a form -of the earth's surface considerably different from the present, -especially, supposing the absence of the valleys which the rivers -have gradually cut out, the transportation of such stones is not -impossible, even by such powers as nature employs at present. Now, -without the supposition that the surface was more continuous, and -that its present inequalities did not exist, no force of torrents, -whatever their velocity and magnitude may have been, could have -produced this transportation. No force of water could raise a stone -like the <i>pierre de goutté</i> from the bottom of a -<span class="pagenum" id="Page_408">- 408 -</span> valley, to the -top of a steep hail. Indeed, if we suppose a great fragment of rock to -be hurried along on a horizontal or an inclined plane, by the force -of water, the moment it comes to a deep valley, and has to rise up -over an ascent of a certain steepness, it will remain at rest; the -water itself will lose its velocity, and the heavy bodies which it -carried with it will proceed no farther. Thus, therefore, we have the -following dilemma. If the surface is not supposed to have had a certain -degree of uniformity in past times, a <i>debacle</i> is insufficient -for the transportation of stones: If it is supposed to have had that -uniformity, a <i>debacle</i> is unnecessary.</p> - -<p>365. Another fact, which has been supposed favourable to the opinion -of the action of great torrents at some former period, is, that in -countries like that round Edinburgh, where whinstone hills rise up from -among secondary strata, a remarkable uniformity is observed in the -direction of their abrupt faces. Thus, in the country just mentioned, -the steep faces generally front the west, whiles in the opposite -direction, the slope is gentle, and the hills decline gradually into -the plain. Hence it is supposed, that a torrent, sweeping from west to -east, has carried off the strata from the west side of these hills, -but, being obstructed by the whinstone rock, -<span class="pagenum" id="Page_409">- 409 -</span> has left the strata on -the east side in their natural place.</p> - -<p>But, besides that no force which can ever be ascribed to a torrent -could have removed at once bodies of strata 300 or 400 feet, nay even -800 or 1000 in thickness, which must have been the case if this were -the true explanation of the fact, there is a circumstance which may -perhaps enable us to explain these phenomena without the assistance of -any extraordinary cause. The secondary strata in which the whinstone -hills are found in this part of Scotland, are not horizontal, but rise -or <i>head</i> towards the west, dipping towards the east. The side, -therefore, of the whinstone hills which is precipitous, is the same -with that towards which the strata rise. Now, from the manner in which -these hills are supposed to have been elevated, the strata are likely -to have been most broken and shattered towards that side, while, on -the opposite, they had the support of the whinstone rock. They would -become a prey, therefore, more easily to the common causes of erosion -and waste on the upper side than on the lower. The streams that flowed -from the higher grounds would wear them on the former most readily; and -the action of these streams would be resisted by the superior hardness -of the whinstone, just as the great torrent of the <i>debacle</i> is -supposed to have been.</p> - -<p><span class="pagenum" id="Page_410">- 410 -</span></p> - -<p>It should also be observed, that this fact of the uniform direction of -the abrupt faces of mountains, is often too hastily generalized. In -primitive countries, it is no farther observed than by the steep faces -of the mountains being most frequently turned toward the central chain. -In Scotland, as soon as you leave the flat country, and enter the -Highlands, the scarps of the hills face indiscriminately all the points -of the compass, and are directed as often to the east as to the west.</p> - -<p>366. Where the strata are nearly horizontal, they afford the most -distinct information concerning the direction and progress of the -wasting of the land. The inclined position of the strata, which in all -other cases must enter for so much into our estimate of the causes -which have produced the present inequality of the earth's surface, -disappears there entirely; and the whole of that inequality is to be -ascribed to the operations at the surface, whether they have been -sudden or gradual. A very important fact from a country of this sort, -is related by <span class="smcap">Barrow</span>, in his Travels into Southern Africa. The -mountains about the Cape of Good Hope, and as far to the north as that -ingenious traveller prosecuted his journey, are chiefly of horizontal -strata of sandstone and limestone, exhibiting the appearance, on their -abrupt sides, of regular layers of masonry, of towers, fortifications, -&c. Now, -<span class="pagenum" id="Page_411">- 411 -</span> among all these mountains, he observed, that the high or -steep sides look constantly down the rivers, while the sloping or -inclined sides have just the opposite direction. When, in travelling -northward, he passed the line of partition, where the waters from -running south take their direction to the north, he found, that the -gradual slope, which had hitherto been turned to the north, was now -turned to the south: The abrupt aspect of the mountains, in like -manner, from facing the south, was directed to the north; so that, -in both cases, the hills turned their backs on the line of greatest -elevation.<a id="FNanchor_184" href="#Footnote_184" class="fnanchor">[184]</a></p> - -<div class="footnote"> - -<p><a id="Footnote_184" href="#FNanchor_184" class="label">[184]</a> Barrow's Travels into Southern Africa, p. 245.</p> - -</div> - -<p>It is evident, therefore, that the form of this land has been -determined by the slow working of the streams. The causes which -produced the effects here described, began their action from the line -of greatest elevation, and extended it from thence on both sides, in -opposite directions. This is the most precise character that can mark -the alluvial operations, and distinguish them from the overwhelming -power of a great <i>debacle</i>.</p> - -<p>367. Lastly, if there were any where a hill, or any large mass composed -of broken and shapeless stones, thrown together like rubbish, and -neither worked into gravel nor disposed with any regularity, we must -ascribe it to some other cause -<span class="pagenum" id="Page_412">- 412 -</span> than the ordinary <i>detritus</i> and -wasting of the land. This, however, has never yet occurred; and it -seems best to wait till the phenomenon is observed, before we seek for -the explanation of it.</p> - -<p>368. These arguments appear to me conclusive against the necessity of -supposing the action of sudden and irregular causes on the surface of -the earth. In this, however, I am perhaps deceived: neither Pallas, -nor Saussure, nor Dolomieu, nor any other author who has espoused -the hypothesis of such causes, has explained his notions with any -precision; on the contrary, they have all spoken with such reserve and -mystery, as seemed to betray the weakness, but may have concealed the -strength of their cause. I have therefore been combating an enemy, that -was in some respects unknown; and I may have supposed him dislodged, -only because I could not penetrate to his strongholds. The question, -however, is likely soon to assume a more determinate form. A zealous -friend of Dr Hutton's theory, has lately<a id="FNanchor_185" href="#Footnote_185" class="fnanchor">[185]</a> declared his approbation -of the hypothesis which has here been represented as so adverse to that -theory; and, from his ability and vigour of research, it is likely to -receive every improvement of which it is susceptible.</p> - -<div class="footnote"> - -<p><a id="Footnote_185" href="#FNanchor_185" class="label">[185]</a> Trans. Royal Society Edin. vol. v. p 68.</p> - -</div> - - -<hr class="chap x-ebookmaker-drop" /> - -<div class="chapter"> -<p><span class="pagenum" id="Page_413">- 413 -</span></p> - -<h2 class="nobreak" id="Note_xix"><span class="smcap">Note xix. § 117.</span></h2> -</div> - -<p class="caption3nb"><i>Transportation of Materials by the Sea.</i></p> - - -<p>369. <span class="smcap">The</span> existence of the great and extensive operations, -by which the spoils of the land are carried all over the ocean, and -spread out on the bottom of it, may be supposed to require some further -elucidation. We must attend, therefore, to the following circumstances.</p> - -<p>When the detritus of the land is delivered by the rivers into the sea, -the heaviest parts are deposited first, and the lighter are carried -to a greater distance from the shore. The accumulation of matter -which would be made in this manner on the coast, is prevented by the -farther operation of the tides and currents, in consequence of which -the substances deposited continue to be worn away, and are gradually -removed farther from the land. The reality of this operation is -certain; for otherwise we should have on the sea shore a constant and -unlimited accumulation of sand and gravel, which, being perpetually -brought down from the land, would continually increase on the shore, if -nature did not employ some machinery for removing the -<span class="pagenum" id="Page_414">- 414 -</span> advanced part -into the sea, in proportion to the supply from behind.</p> - -<p>The constant agitation of the waters, and the declivity of the -bottom, are no doubt the causes of this gradual and widely extended -deposition. A soft mass of alluvial deposit, having its pores filled -with water, and being subject to the vibrations of a superincumbent -fluid, will yield to the pressure of that fluid on the side of the -least resistance, that is, on the side toward the sea, and thus will -be gradually extended more and more over the bottom. This will happen -not only to the finer parts of the detritus, but even to the grosser, -such as sand and gravel. For suppose that a body of gravel rests on -a plane somewhat inclined, at the same time that it is covered with -water to a considerable depth, that water being subject not only to -moderate reciprocations, but also to such violent agitation as we see -occasionally communicated to the waters of the ocean; the gravel, -being rendered lighter by its immersion in the water, and on that -account more moveable, will, when the undulations are considerable, -be alternately heaved up and let down again. Now, at each time that -it is heaved up, however small the space may be, it must be somewhat -accelerated in its descent, and will hardly settle on the same point -where it rested before. Thus it will gain a little -<span class="pagenum" id="Page_415">- 415 -</span> ground at each -undulation, and will slowly make its way towards the depths of the -ocean, or to the lowest situation it can reach. This, as far as we may -presume to follow a progress which is not the subject of immediate -observation, is one of the great means by which loose materials of -every kind are transported to a great distance, and spread out in beds -at the bottom of the ocean.</p> - -<p>370. The lighter parts are more easily carried to great distances, -being actually suspended in the water, by which they are very gradually -and slowly deposited. A remarkable proof of this is furnished from an -observation made by Lord Mulgrave, in his voyage to the North Pole. -In the latitude of 65° nearly, and about 250 miles distant from the -nearest land, which was the coast of Norway, he sounded with a line of -688 fathoms, or 4098 feet; and the lead, when it struck the ground, -sunk in a soft blue clay to the depth of ten feet.<a id="FNanchor_186" href="#Footnote_186" class="fnanchor">[186]</a> The tenuity -and fineness of the mud, which allowed the lead to sink so deep into -it, must have resulted from a deposition of the lighter kinds of -earth, which being suspended in the water, had been carried to a great -distance, and were now without doubt -<span class="pagenum" id="Page_416">- 416 -</span> forming a regular stratum at the -bottom of the sea.</p> - -<div class="footnote"> - -<p><a id="Footnote_186" href="#FNanchor_186" class="label">[186]</a> Phipps's Voyage, p. 74, 141.</p> - -</div> - -<p>371. The quantity of detritus brought down by the rivers, and -distributed in this manner over the bottom of the sea, is so great, -that several narrow seas have been thereby rendered sensibly shallower. -The Baltic has been computed to decrease in depth at the rate of -forty inches in a hundred years. The Yellow Sea, which is a large -gulf contained between the coast of China and the peninsula of Corea, -receives so much mud from the great rivers that run into it, that it -takes its colour, as well as its name, from that circumstance; and the -European mariners who have lately navigated it, observed, that the -mud was drawn up by the ships, so as to be visible in their wake to a -considerable distance.<a id="FNanchor_187" href="#Footnote_187" class="fnanchor">[187]</a> Computations have been made of the time -that it will require to fill up this gulf, and to withdraw it entirely -from the dominion of the ocean: but the data are not sufficiently exact -to afford any precise result, and are no doubt particularly defective -from this cause, that much of the earth carried into the gulf by the -rivers, must be carried out of it by the currents and tides, and -the finer parts wafted probably to great distances -<span class="pagenum" id="Page_417">- 417 -</span> in the Pacific -Ocean.<a id="FNanchor_188" href="#Footnote_188" class="fnanchor">[188]</a> The mere attempt, however, towards such a computation, -shows how evident the progress of filling up is to every attentive -observer; and, though it may not ascertain the measure, it sufficiently -declares the reality of the operations, by which the waste of the -present continents is made subservient to the formation of new land.</p> - -<div class="footnote"> - -<p><a id="Footnote_187" href="#FNanchor_187" class="label">[187]</a> Staunton's Account of the Embassy to China, vol. i. p. -448.</p> - -</div> - -<div class="footnote"> - -<p><a id="Footnote_188" href="#FNanchor_188" class="label">[188]</a> Perouse, in sailing along the coast of China, from -Formosa to the strait between Corea and Japan, though generally -fifty or sixty leagues from the land, had soundings at the depth of -forty-five fathoms, and sometimes at that of twenty-two. Atlas du -Voyage de la Perouse, No. 43.</p> - -</div> - -<p>372. Sandbanks, such as abound in the German Ocean, to whatever they -owe their origin, are certainly modified, and their form determined, -by the tides and currents. Without the operation of these last, banks -of loose sand and mud could hardly preserve their form, and remain -intersected by many narrow channels. The formation of the banks on the -coast of Holland, and even of the Dogger Bank itself, has been ascribed -to the meeting of tides, by which a state of tranquillity is produced -in the waters, and of consequence a more copious deposition of their -mud. Even the great bank of Newfoundland seems to be determined in its -extent by the -<span class="pagenum" id="Page_418">- 418 -</span> action of the Gulf stream. In the North Sea, the current -which sets out of the Baltic, has evidently determined the shape of -the sandbanks opposite to the coast of Norway, and produced a circular -sweep in them, of which it is impossible to mistake the cause.</p> - -<p>In proof of the action here ascribed to the waters of the sea, in -transporting materials to an unlimited extent, we may add the well -known observation, that the stones brought up by the lead from the -bottom of the sea, are generally round and polished, hardly ever sharp -and angular. This could never happen to stones that were not subject to -perpetual attrition.</p> - -<p>373. Currents are no doubt the great agents in diffusing the detritus -of the land over the bottom of the sea. These have been long known to -exist; but it is only since the later improvements in navigation, that -they have been understood to constitute a system of great permanence, -regularity, and extent, connected with the trade winds, and other -circumstances in the natural history of the globe. The Gulf stream was -many years since observed to transport the water, and the temperature -of the tropical regions into the climates of the north; and we are -indebted to the researches of Major <span class="smcap">Rennell</span>, for the knowledge -of a great system of currents, of which it is only a part. That -geographer, who is so eminent -<span class="pagenum" id="Page_419">- 419 -</span> for enriching the details of his science -with the most interesting facts in history or in physics, has shown, -that along the eastern coast of Africa, from about the mouth of the Red -Sea, a current fifty leagues in breadth sets continually towards the -south-west.<a id="FNanchor_189" href="#Footnote_189" class="fnanchor">[189]</a> It doubles the Cape of Good Hope, runs from thence -north-west, preserving on the whole the direction of the coast, but -reaching so far into the ocean, that, about the parallel of St Helena, -its breadth exceeds 1000 miles. From thence, as it approaches the line, -its direction is more nearly east; and meeting in the parallel of 3° -north, with a current which has come along the western coast of Africa -from the north, the two united stretch across the Atlantic, in a line -somewhat south of west, and in a very wide and rapid stream. This -stream meets the American land at Cape St Roque, where it is joined -by another coming up along the eastern shore of that continent, and -directed towards the north. They proceed northward together till they -enter the Gulf of Florida, from which being as it were reflected, they -form the Gulf stream, passing along the coast of North America, and -stretching across the Atlantic to the British Isles. From thence the -current turns to the south, and, proceeding down -<span class="pagenum" id="Page_420">- 420 -</span> the coast of Spain -and Africa, meets the stream ascending from the south, as already -described, and thus continues in perpetual circulation. The velocity of -these currents is not less remarkable than their extent. At the Cape -of Good Hope, the rate is thirty nautical miles in twenty four hours; -in some places forty five; and under the line seventy seven. When the -Gulf stream issues from the Straits of Bahama, it runs at the rate of -four miles an hour, and proceeds to the distance of 1800 miles, before -its velocity is reduced to half that quantity. In the parallel of 38°, -near 1000 miles from the above strait, the water of the stream has been -found ten degrees warmer than the air.</p> - -<div class="footnote"> - -<p><a id="Footnote_189" href="#FNanchor_189" class="label">[189]</a> Geography of Herodotus, p. 672.</p> - -</div> - -<p>374. The course of the Gulf stream is so fixed and regular, that -nuts and plants from the West Indies are annually thrown ashore on -the Western Islands of Scotland. The mast of a man of war, burnt at -Jamaica, was driven several months afterwards on the Hebrides,<a id="FNanchor_190" href="#Footnote_190" class="fnanchor">[190]</a> -after performing a voyage of more than 4000 miles, under the direction -of a current, which, in the midst of the ocean, maintains its course as -steadily as a river does upon the land.</p> - -<div class="footnote"> - -<p><a id="Footnote_190" href="#FNanchor_190" class="label">[190]</a> Pennant's Arctic Zoology, Introd. p. 70.</p> - -</div> - -<p>The great system of currents thus traced through the Atlantic, has no -doubt phenomena -<span class="pagenum" id="Page_421">- 421 -</span> corresponding to it in the Indian and Pacific Oceans, -which the industry of future navigators may discover. The whole appears -to be connected with the trade winds, the figure of our continents, the -temperature of the seas themselves, and perhaps with some inequalities -in the structure of the globe. The disturbance produced by these causes -in the equilibrium of the sea, probably reaches to the very bottom of -it, and gives rise to those counter currents, which have sometimes been -discovered at great depths under the surface.<a id="FNanchor_191" href="#Footnote_191" class="fnanchor">[191]</a></p> - -<div class="footnote"> - -<p><a id="Footnote_191" href="#FNanchor_191" class="label">[191]</a> Histoire Naturelle de Buffon, Supplément, tom. ix. p. -479. 8vo.</p> - -</div> - -<p>The great transportation of materials that must result from the -action of these combined currents is obvious, and serves not a little -to diminish our wonder, at finding the productions of one climate -so frequently included among the fossils of another. Amid all the -revolutions of the globe, the economy of nature has been uniform, in -this respect, as well as in so many others, and her laws are the only -thing that have resisted the general movement. The rivers and the -rocks, the seas and the continents, have been changed in all their -parts; but the laws which direct those changes, and the rules -<span class="pagenum" id="Page_422">- 422 -</span> to which -they are subject, have remained invariably the same.</p> - -<p>375. Objections have been made to that translation of materials by the -waters of the ocean which is supposed in this theory, particularly -by Mr Kirwan, in his Geological Essays; and, though I might perhaps -content myself with the remark already made, that the Neptunian system -involves suppositions concerning the transportation of solid bodies by -the sea, in the early ages of the world, as wonderful as those which, -according to our theory, are common to all ages, I am unwilling to -remain satisfied with a mere <i>argumentum ad hominem</i>, where the -fallacy of the reasoning is so easily detected.</p> - -<p>376. One of Mr Kirwan's objections to the deposition of materials at -the bottom of the sea, is thus stated: "<span class="smcap">Frisi</span> has remarked, in -his mathematical discourses, that if any considerable mass of matter -were accumulated in the interior of the ocean, the diurnal motion of -the globe would be disturbed, and consequently it would be perceptible; -a phenomenon, however, of which no history or tradition gives any -account."<a id="FNanchor_192" href="#Footnote_192" class="fnanchor">[192]</a></p> - -<div class="footnote"> - -<p><a id="Footnote_192" href="#FNanchor_192" class="label">[192]</a> Geol. Essays, p. 441.</p> - -</div> - -<p>The appeal made here to Frisi is singularly unfortunate, as that -philosopher has demonstrated -<span class="pagenum" id="Page_423">- 423 -</span> the very contrary of Mr Kirwan's -position, and has proved, that the disturbance given to the diurnal -motion by the causes here referred to may be real, but cannot be -perceptible. Having investigated a formula expressing the law which all -such disturbances must necessarily observe, he concludes, "Hàc autem -formulâ manifestum fiet, ex iis omnibus variationibus quæ in terrestri -superficie observari solent, montium et collium abrasione, dilapsu -corporum ponderosiorum in inferiores telluris sinus, nullam oriri -posse variationem <i>sensibilem</i> diurni motûs. Nam si statuamus -data aliqua annorum periodo terrestrem superficiem ad duos usque pedes -abradi undique, eam vero materiæ quantitatem ad profunditatem pedum -1000 dilabi; erit omne quod inde orietur incrementum velocitatis diurni -motûs 30000/(19638051)<sup>2</sup> = 1/12855068184."<a id="FNanchor_193" href="#Footnote_193" class="fnanchor">[193]</a></p> - -<div class="footnote"> - -<p><a id="Footnote_193" href="#FNanchor_193" class="label">[193]</a> Frisii Opera, tom. iii. p. 269.</p> - -</div> - -<p>Here, it is evident, that Frisi admits those very changes on the -surface which we are contending for, and shows, that their tendency is -to accelerate the earth's diurnal motion, but, by a quantity so small, -that, in a space of time amounting at least to 200 years, the increase -of the diurnal motion would only be such a part of the -<span class="pagenum" id="Page_424">- 424 -</span> whole as the -preceding fraction is of unity.<a id="FNanchor_194" href="#Footnote_194" class="fnanchor">[194]</a></p> - -<div class="footnote"> - -<p><a id="Footnote_194" href="#FNanchor_194" class="label">[194]</a> The time requisite for taking away by waste and erosion -two feet from the surface of all our continents, and depositing it at -the bottom of the sea, cannot be reckoned less than 200 years. The -fraction 1/12855068184, reduced to parts of a day, is 1/148554 of a -second; so that it would require 200 years to shorten the length of -the day, by the above fraction of a second; and therefore it would -require 148554 times 200 years, or 29710800 years, to diminish it an -entire second. The accumulated effect, however, of all the diminutions -during that period, would amount to much more: and if we had any -perfectly uniform standard to compare the motion of the earth with, -its difference from that standard would increase as the squares of the -time, and the total acceleration would amount to one second in 77080 -years. Whatever relation this bears to the age of the globe itself, it -exceeds more than ten times the age of any historical record.</p> - -<p>Though Frisius concludes, as is stated here, that the acceleration -produced in the diurnal motion of the earth, is far too inconsiderable -to become the object of astronomical observation, he makes a -supposition difficult to be reconciled with this conclusion, namely, -that the acceleration has had a sensible effect on the figure of the -earth, or rather of the sea, having increased the centrifugal force, -and thereby accumulated the waters under the equator, in the present, -more than in former ages. Such an accumulation, he thinks agreeable -to certain appearances that have been observed respecting the ancient -level of the sea. These appearances will be afterwards considered: it -is sufficient to remark here, that though the fraction, expressing the -increment of the centrifugal force, must be double that which expresses -the acceleration, it must be too small to have any perceptible effect -in elevating the sea, except after an immense interval of time; and the -compensations which arise from other causes, probably must prevent it -from becoming sensible in any length of time whatsoever.</p> - -</div> - -<p><span class="pagenum" id="Page_425">- 425 -</span></p> - -<p>377. The instance just given may serve as one of many, to shew what -confidence is to be placed in that indigested mass of facts and -quotations which Mr Kirwan, without discrimination, and without -discussion, has brought together from all quarters. He has no -intention, I believe, to deceive his readers; but we may judge, from -this specimen, of the precautions he has taken against being deceived -himself.</p> - -<p>In some respects, the result of Frisi's investigation must be -considered as imperfect. If there were no relative motion in the parts -of our globe, but that by which things descend from a higher to a lower -level, a continual acceleration of its rotation, though extremely slow, -would take place, as above computed. But as, in the interior of the -earth, there are undoubtedly motions of a tendency opposite to those on -the surface, and directed from the centre towards the -<span class="pagenum" id="Page_426">- 426 -</span> circumference, -they must produce a retardation in the diurnal revolution; and from -this must arise an inequality, not uniformly progressive in the same -direction, but periodical, and confined within certain limits, as the -causes are by which it is produced.<a id="FNanchor_195" href="#Footnote_195" class="fnanchor">[195]</a></p> - -<div class="footnote"> - -<p><a id="Footnote_195" href="#FNanchor_195" class="label">[195]</a> Even in the descent of bodies from a higher to a lower -level at the surface of the earth, the whole tendency is not to -increase the velocity of the earth's rotation, and many compensations -take place, which, when the matter is considered only in general, -are necessarily overlooked. This will appear evident, if we reflect, -that it is not simply the approach of a body towards the centre of -the earth, or its removal from that centre, which tends to disturb -the rotation of the earth; but its approach to the axis of the earth, -or its removal from that axis. The velocity with which a particle of -matter revolves, whether on the surface, or in the interior of the -globe, is proportional to its distance from the axis of rotation; -and therefore, when a body comes nearer to the axis, it loses a part -of the motion which it had before; which part, of consequence, is -communicated to the whole mass of the earth, and therefore tends to -increase the velocity with which it revolves. The contrary happens when -a body recedes from the axis; for it then receives an addition to its -velocity, which, of course, is taken away from the rotatory motion of -the earth.</p> - -<p>Hence, bodies moving in a horizontal plane, may increase or diminish -the swiftness of the diurnal motion, according as they move towards the -poles or towards the equator; and those which descend from a higher to -a lower level, disturb the earth's rotation, much more in consequence -of their horizontal, than of their perpendicular motion. The Ganges, -for instance, though its source is probably elevated no less than -7000 feet above the level of the sea, tends to retard the earth's -rotation, by bringing its waters, and the mud contained in them, from -the parallel of 31° to that of 22°, and so increasing their distance -from the earth's axis by more than 1/12 th part. Had the Ganges flowed -towards the north, as the Nile does, its effect would have been just -the contrary.</p> - -<p>In the same manner, a stone descending from the top of a mountain, may -accelerate or retard the earth's rotation, according to the direction -in which it descends. If it descend on the side of the elevated pole, -it will then produce acceleration, because its distance from the axis -will be diminished; but if it descend on the side of the depressed -pole, and if the direction in which it is moved, be over a line less -inclined, than a line drawn from the same point to the depressed pole, -it will then produce a retardation, because its distance from the axis -will be increased.</p> - -<p>Let us suppose, for example, that the top of Mount Blanc is in latitude -45° 49′, and that its height is 2450 toises above the level of the sea. -The point at which a line drawn from the top of this mountain, parallel -to the earth's axis, will meet the superficies of the sea, (supposing -that superficies continued inland from the Mediterranean), must be -about 2382 toises in horizontal distance, or about 2½ minutes south -of the summit, that is, in the parallel of 45° 46½′; and if this -parallel be continued all round the globe, the points of the earth's -surface between it and the equator, are all more distant from the -earth's axis than the top of Mount Blanc is; whereas all the points -to the north of it are nearer to that axis. A stone, therefore, from -the top of Mount Blanc, if carried any where to the south of the above -parallel, will retard the earth's diurnal motion; but if carried any -where to the north of the same line, will accelerate that motion.</p> - -<p>The same quantity of matter, however, carried an equal distance -toward the pole, and toward the equator, from any point, will lose -more velocity in the former case than it will gain in the latter, as -easily follows from the nature of circle. Therefore, supposing an equal -dispersion of the detritus of a mountain in all directions, the parts -that go toward the pole will most disturb the diurnal motion; and hence -a balance on their side, or in favour of acceleration, as already -observed.</p> - -</div> - -<p><span class="pagenum" id="Page_427">- 427 -</span></p> - -<p>378. Mr Kirwan's second objection is founded on the misapprehension -of a well-known fact in -<span class="pagenum" id="Page_428">- 428 -</span> the natural history of the earth. "Rivers," -says this author, "do not carry into the sea the spoils which they -bring from the land, but employ them in the formation of deltas of -low alluvial land at their mouths, according to what Major Rennell -has proved." The fact of the formation of <i>deltas</i> from the -spoils which the rivers carry from -<span class="pagenum" id="Page_429">- 429 -</span> the higher grounds, is perfectly -ascertained; and the detail into which Major Rennell has entered in -the passage referred to by Mr Kirwan, does credit to the acuteness and -accuracy of that excellent geographer. But it is not there asserted, -that rivers employ <i>all</i> the materials which they carry with them, -in the formation of those deltas, and deliver none of them into the -sea. On the contrary, they carry from the <i>delta</i> itself mud and -earth, which they can deposit no where but in the sea; and it is this -circumstance chiefly that limits the increase of those alluvial lands, -and makes them either cease to increase, or makes them increase very -slowly after a certain period, though the supply of earth from the -higher grounds remains nearly the same. To make Mr Kirwan's argument -conclusive, it would be necessary to prove, that <i>all</i> the mud -carried down by the Nile or the Ganges, was deposited on the low -lands before these rivers enter the sea; a thing so obviously absurd, -that nothing but his haste to obtain a conclusion unfavourable to the -Plutonic system, could have prevented him from perceiving it<a id="FNanchor_196" href="#Footnote_196" class="fnanchor">[196]</a>.</p> - -<div class="footnote"> - -<p><a id="Footnote_196" href="#FNanchor_196" class="label">[196]</a> The instance mentioned in the Geological Essays, from -the travels of the Abbé Fortis, concerning urns thrown into the -Adriatic, upwards of 1400 years ago, and not yet covered with mud, -must be explained from peculiar circumstances, or local causes, with -which we are unacquainted, as it makes against the deposition of earth -near the shore, and in narrow seas; a general fact which, I think, -every body admits.</p> - -</div> - -<p><span class="pagenum" id="Page_430">- 430 -</span></p> - -<p>379. A remark which Major Rennell has made concerning the mouths of -rivers, in his Geography of Herodotus, deserves Mr Kirwan's attention, -though perhaps he may not be able to put on it an interpretation quite -so favourable to his system. The remark is, that the mouths of great -rivers are often formed on principles quite opposite to one another, -so that some of them have a real delta or triangle of flat land at -their mouths, while others have an estuary, or what may not improperly -be called a <i>negative</i> delta. Of the latter kind are some of the -greatest rivers in the world, the Plata, the Oroonoko and the Maranon, -and by far the greatest number of our European rivers. Nobody can -doubt, that the three rivers just named carry with them as much earth -as the Nile, or the Euphrates, or any other river in the world. All -this they have deposited in the sea, and committed to the currents, -which sweep along the shore of the American continent, and by these -they have been spread out over the unlimited tracts of the ocean.</p> - -<p><span class="pagenum" id="Page_431">- 431 -</span></p> - -<p>Indeed, nothing can be more just than Dr Hutton's observation, that -where low land is formed at the mouths of rivers, there the rivers -bring down more than the sea is able to carry away; but that where -such land is not formed, it is because the sea is able to carry off -immediately all the deposit which it receives.</p> - -<p>380. Mr Kirwan has denied on another principle the power of the sea to -carry to a distance the materials delivered into it: "Notwithstanding," -says he, "many particles of earth are by rivers conduced to the sea, -yet <i>none are conveyed in any distance</i>, but are either deposited -at their mouths, or rejected by currents or by tides; and the reason -is, because the tide of flood is always more impetuous and forcible -than the tide of ebb, the advancing waves being pressed forward by -the countless number behind them, whereas the retreating are pressed -backward by a far smaller number, as must be evident to an attentive -spectator; and hence it is that all floating things cast into the sea, -are at last thrown on shore, and not conveyed into the mid regions of -the sea, as they should be if the reciprocal undulations of the tides -were equally powerful "<a id="FNanchor_197" href="#Footnote_197" class="fnanchor">[197]</a></p> - -<div class="footnote"> - -<p><a id="Footnote_197" href="#FNanchor_197" class="label">[197]</a> Kirwan's Geol. Essays, p. 439.</p> - -</div> - -<p><span class="pagenum" id="Page_432">- 432 -</span></p> - -<p>381. But if the <i>attentive spectator</i>, instead of trusting to a -vague impression, or listening to some crude theory of undulations, -reflects on one of the most simple facts respecting the ebbing and -flowing of the tides, he will be very little disposed to acquiesce in -the above conclusion. He has only to consider, that the flowing of the -tide requires just six hours, and the ebbing of it likewise six hours; -so that the same body of water flows in upon the shore, and retreats -from it, in the same time. The quantity of matter moved, therefore, and -the velocity with which it is moved, are in both cases the same; and it -remains for Mr Kirwan to show in what the difference of their force can -possibly consist.</p> - -<p>The force with which the waves usually break upon our shores, does not -arise from the velocity of the tide being greater in one direction -than in another. In the main ocean, the waves have no progressive -motion, and the columns of water alternately rise and fall, without -any other than a reciprocating motion: a kind of equilibrium takes -place among the undulations, and each wave being equally acted upon by -those on opposite sides, remains fixed in its place. Near the shore -this cannot happen; the water on the land side from its shallowness -being incapable -<span class="pagenum" id="Page_433">- 433 -</span> of rising to the height necessary to balance the -great undulations which are without. The water runs, therefore, as it -were, from a higher to a lower level, spreading itself towards the -land side. This produces the breakers on our shores, and the surf -of the tropical seas. A rock or a sandbank coming within a certain -distance of the surface, is sufficient, in any part of the ocean, to -obstruct the natural succession of undulations; and, by destroying the -mutual reaction of the waves, to give them a progressive instead of a -reciprocating motion.</p> - -<p>382. It is, however, but from a small distance, that the waves are -impelled against the shore with a progressive motion. The border of -breakers that surrounds any coast is narrow, compared with the distance -to which the <i>detritus</i> from the land is confessedly carried; the -water, while it advances at the surface, flows back at the bottom; -and these contrary motions are so nearly equal, that it is but a very -momentary accumulation of the water that is ever produced on any shore.</p> - -<p>If it were otherwise, and if it were true that the sea throws out every -thing, and carries away nothing, we should have a constant accumulation -of earth and sand along all shores whatsoever, at least wherever a -stream ran into the sea. -<span class="pagenum" id="Page_434">- 434 -</span> This, as is abundantly evident, is quite -contrary to the fact.</p> - -<p>So, also, the bars formed at the mouths of rivers, after having -attained a certain magnitude, increase no farther, not because they -cease to receive augmentations from the land, but because their -diminution from the sea, increasing with their magnitude, becomes at -length so great, as completely to balance those augmentations. When -properly examined, therefore, the phenomena, which have been proposed -as most inconsistent with the indefinite transportation of stony -bodies, afford very satisfactory proofs of that operation.</p> - -<p>383. It is true, that bodies which float in the water, when carried -along on the tops of the waves towards a shelving beach, having -acquired a certain velocity, are thrown farther in upon the land than -the distance they would have floated to, if they had been simply -sustained by the water. The depth of water, therefore, at the place -where they take the ground, is not likely to be such as to float them -again, and to carry them out towards the sea. They are, therefore, left -behind; and this produces an appearance of a force impelling floating -bodies towards the land, much greater and more general than really -takes place.</p> - -<p><span class="pagenum" id="Page_435">- 435 -</span></p> - -<p>These observations may serve to show, how unsound the principles are -from which Mr Kirwan's conclusions are deduced: they are perhaps more -than is necessary for that purpose: it might have been sufficient to -observe, that the increase of land on the sea shore is limited, though -the augmentation from the land is certainly indefinite, a proof that -the diminution from the sea is constant and equal to the increase.</p> - -<p>384. "Mariners," says Mr Kirwan, "were accustomed, for some centuries -back, to discover their situation, by the kind of earth or sand brought -up by their sounding plummets; a method which would prove fallacious, -if the surface of the bottom did not continue invariably the same."<a id="FNanchor_198" href="#Footnote_198" class="fnanchor">[198]</a></p> - -<div class="footnote"> - -<p><a id="Footnote_198" href="#FNanchor_198" class="label">[198]</a> Geol. Essays, p. 440.</p> - -</div> - -<p>The fact here stated, that mariners, when navigation was more imperfect -than it is now, had very frequent recourse to this method, and that -they still use it occasionally, is very true. But from this, the only -inference that can be fairly deduced is, that the changes at the bottom -of the sea are very slow, and the variation but little; not merely -from one year to another, but even from one century to another. The -rules by which the mariner judged of his position from the quality of -the earth which the lead brought up, and which were deduced no -<span class="pagenum" id="Page_436">- 436 -</span> doubt -from observations made at no very great distance of time, might be -sufficient for his purpose, though a slow change had been all the while -going forward. Such observations could at best have little accuracy, -and could not be affected by small variations. It is the slowness of -the change, that makes the experience of one age applicable, in this, -as in innumerable other instances, to the observations of the next. If -a long interval is taken, we will look in vain for the same uniformity -of results. A pilot, who would at present judge of his position in -the German Ocean, by comparing his soundings with those taken by -<span class="smcap">Pytheas</span>, (supposing them known) in his navigation of that -sea, more than 2000 years ago, could hardly be expected to determine -his latitude and longitude with great exactness; and I know not if the -most zealous advocate for the immutability of the earth's surface, -would be willing to trust his safety in a ship that was guided by such -antiquated rules.</p> - - -<hr class="chap x-ebookmaker-drop" /> - -<div class="chapter"> -<p><span class="pagenum" id="Page_437">- 437 -</span></p> - -<h2 class="nobreak" id="Note_xx"><span class="smcap">Note xx. § 118.</span></h2> -</div> - -<p class="caption3nb"><i>Inequalities in the Planetary Motions.</i></p> - - -<p>385. The assertion that, in the planetary motions, we discover no mark, -either of the commencement or termination of the present order, refers -to the late discoveries of <span class="smcap">La Grange</span> and <span class="smcap">La Place</span>, -which have contributed so much to the perfection of physical astronomy. -From the principle of universal gravitation, these mathematicians have -demonstrated, that all the variations in our system are periodical; -that they are confined within certain limits; and consist of alternate -diminution and increase. The orbits of the planets change not only -their position, but even their magnitude and their form: the longer -axis of each has a slow angular motion; and, though its length remains -fixed, the shorter axis increases and diminishes, so that the form of -the orbit approaches to that of a circle, and recedes from it by turns. -In the same manner, the obliquity of the ecliptic, and the inclination -of the planetary orbits, are subject to change; but the changes are -small, and, being first in one direction, and then in the opposite, -<span class="pagenum" id="Page_438">- 438 -</span> -they can never accumulate so as to produce a permanent or a progressive -alteration. Thus, in the celestial motions, no room is left for the -introduction of disorder; no irregularity or disturbance, arising from -the mutual action of the planets, is permitted to increase beyond -certain limits, but each of them, in time, affords a correction for -itself. The general order is constant, in the midst of the variation -of the parts; and, in the language of La Place, there is a certain -mean condition, about which our system perpetually <i>oscillates</i> -performing small vibrations on each side of it, and never receding -from it far.<a id="FNanchor_199" href="#Footnote_199" class="fnanchor">[199]</a> The system is thus endowed with a stability, which -can refill the lapse of unlimited duration; it can only perish by an -external cause, and by the introduction of laws, of which at present no -vestige is to be traced.</p> - -<div class="footnote"> - -<p><a id="Footnote_199" href="#FNanchor_199" class="label">[199]</a> Exposition du Systéme du Monde, par La Place, Livre iv. -chap. 6. p. 199. 2d edit.</p> - -</div> - -<p>386. The same <i>calculus</i> to which we are indebted for these -sublime conclusions, informs us of two circumstances, which mark -the law here treated of as an effect of wise design, to the entire -exclusion both of necessity and chance. One of these circumstances -consists in the planetary motions being all in the same direction, or -all <i>in consequentia</i> as it is called by the astronomers. -<span class="pagenum" id="Page_439">- 439 -</span> This is -essential to the compensation and stability above mentioned:<a id="FNanchor_200" href="#Footnote_200" class="fnanchor">[200]</a> had -one planet circulated round the sun in a direction from east to west, -and another in a direction from west to east, the disturbances they -would have produced on one another's motion would not necessarily have -been periodical; their irregularities might have continually increased, -and they might have deviated in the course of ages from their original -condition, beyond any limits that can be assigned.</p> - -<div class="footnote"> - -<p><a id="Footnote_200" href="#FNanchor_200" class="label">[200]</a> La Place, <i>ibid.</i></p> - -</div> - -<p>The other circumstance, on which the stability of our system depends, -is the small eccentricity of the planetary orbits, or their near -approach to circles. Were their orbits very eccentric, an opening -would be given to progressive change, that might so far increase, as -to prove the destruction of the whole. But neither the movement of all -the planets in the same direction, nor the small eccentricity of their -orbits, can be ascribed to accident, since that either of these should -happen by chance, in as many instances as there are planets, both -primary and secondary, is almost infinitely improbable. Again, that -any necessity in the nature of things should have either determined -the <i>direction</i> of the planetary motions, or proportioned the -<i>quantity</i> of them -<span class="pagenum" id="Page_440">- 440 -</span> to the intensity of the central force, cannot -be admitted, as these are things unavoidably conceived to be quite -independent of one another. It remains, therefore, that we consider the -laws, which make the disturbances in our system correct themselves, and -by that means give firmness and permanence to it, as a proof of the -consummate wisdom with which the whole is constructed.</p> - -<p>387. The geological system of Dr Hutton, resembles, in many respects, -that which appears to preside over the heavenly motions. In both, we -perceive continual vicissitude and change, but confined within certain -limits, and never from a certain, mean condition, which is such, that, -in the lapse of time, the deviations from it on the one side, must -become just equal to the deviations from it on the other. In both, a -provision is made for duration of unlimited extent, and the lapse of -time has no effect to wear out or destroy a machine, constructed with -so much wisdom. Where the movements are all so perfect, their beginning -and end must be alike invisible.</p> - - -<hr class="chap x-ebookmaker-drop" /> - -<div class="chapter"> -<p><span class="pagenum" id="Page_441">- 441 -</span></p> - -<h2 class="nobreak" id="Note_xxi"><span class="smcap">Note xxi. § 122.</span></h2> -</div> - -<p class="caption3nb"><i>Changes in the apparent Level of the Sea.</i></p> - - -<p><a id="sec_388"></a>388. In speaking of the natural epochs marked out by the phenomena -of the mineral kingdom, we have supposed a greater simplicity, and -separation of effects from one another, than probably takes place in -nature. We have, for instance, abstracted, in speaking of the waste -and degradation of the land, from that elevation which may have been -carried on at the same time. This appeared necessary to be done, in -order to simplify as much as possible the view that was to be given of -the whole; but there can be no doubt, that, while the land has been -gradually worn down by the operations on its surface, it has been -raised up by the expansive forces acting from below. There is even -reason to think, that the elevation has not been uniform, but has been -subject to a kind of oscillation, insomuch, that the continents have -both ascended and descended, or have had their level alternately raised -and depressed, independently of all action at the surface, and this -<span class="pagenum" id="Page_442">- 442 -</span> -within a period comparatively of no great extent.</p> - -<p>It will be easily understood, that the facts we are going to state, -each taken singly, prove nothing more than a change of the line in -which the surface of the sea intersects the surface of the land, -leaving it uncertain to which of the two the change ought really to be -ascribed. Taken in combination, however, these facts may determine what -each of them separately cannot ascertain. I shall first, therefore, -mention some of the principal observations relative to the change above -mentioned, and shall then compare them, in order to discover whether it -is most probable that this change has been produced by the motion of -the land or of the sea.</p> - -<p>389. If we begin with examining the coasts of our own island, we shall -find clear evidence every where, that the sea once reached higher up -upon the land than it does at present. The marks of an ancient sea -beach are to be seen beyond the present limits of the tide, and beds -of sea shells, not mineralized, are found in the loose earth or soil, -sometimes as high as thirty feet above the present level of the sea. -Some of these on the shores of the Frith of Forth are very well known, -and have been often mentioned. Indeed, on the shores of that frith, -many monuments appear, which would seem to carry the -<span class="pagenum" id="Page_443">- 443 -</span> difference -between the present and the ancient level of the sea, to more than -forty feet. The ground on which the Botanic Garden of Edinburgh is -situated, after a thin covering of soil is removed, consists entirely -of sea sand, very regularly stratified, with layers of a black -carbonaceous matter, in thin lamellæ, interposed between them. Shells I -believe are but rarely found in it, but it has every other appearance -of a sea beach. The height of this ground above the present level of -the sea is certainly not less than forty feet.</p> - -<p>390. On almost every part of the coast where the rocks do not rise -quite abrupt and precipitous from the sea, similar marks of the -lowering of the sea, or the rising of the land, may be observed. On the -shores opposite to ours, the same appearances are remarked. The author -of the Lettre Critique to M. de Buffon, tells us, that he had found -the bottom of a bason at Dunkirk, which he had reason to think was dug -about 950 years ago, ten feet and a half above the present low water -mark, though it must have been originally under it. The bottom of this -bason is in the native chalk. From this, the same author concludes, -that the sea at Dunkirk lowers its level at the rate of an inch nearly -in seven years. The observation was made in -<span class="pagenum" id="Page_444">- 444 -</span> 1762, (Lettre à M. le -Comte de Buffon, &c. p. 55.)<a id="FNanchor_201" href="#Footnote_201" class="fnanchor">[201]</a></p> - -<div class="footnote"> - -<p><a id="Footnote_201" href="#FNanchor_201" class="label">[201]</a> In the county of Suffolk, near Wood Bridge, at the -distance of seven or eight miles from the sea, are the Crag-pits, in -which prodigious quantities of sea shells are discovered, many of them -perfect and quite solid, (Pennant's Arctic Zoology, Introd. p. 6.) -Lincolnshire affords various proofs of the same kind; but some other -circumstances in the appearance of that coast, just about to be taken -notice of, indicate changes of a more complicated nature.</p> - -</div> - -<p>391. The shores of the Low Countries, and of Holland, have been often -instanced in proof of the same kind of changes, and it has been -supposed, that, independently of those artificial barriers which at -present exclude the waters of the ocean from overflowing a great part -of this tract, nature herself has brought it nearer to the surface -than it had formerly been. It is indeed certain, that those countries, -to a very great extent inland, have either been under the sea at some -period, by no means remote if compared with the great revolutions of -the globe, or that they are entirely alluvial, and of the same sort -with the Deltas formed at the mouths of rivers. The relative changes, -however, of the sea and land on this tract, have been differently -represented, and I am unwilling, -<span class="pagenum" id="Page_445">- 445 -</span> on that account, to found any -argument on them.</p> - -<p>392. If we proceed farther to the north, to the shores of the Baltic -for instance, we have undoubted evidence of a change of level in the -same direction as on our own shores. The level of this sea has been -represented as lowering at so great a rate as 40 inches in a century. -Celsius observed, that several rocks which are now above water, -were not long ago sunken rocks, and dangerous to navigators; and he -particularly took notice of one, which, in the year 1680, was on the -surface of the water, and in the year 1791 was 20½ Swedish inches -above it. From an inscription near Aspô, in the lake Melar, which -communicates with the Baltic, engraved, as is supposed, about five -centuries ago, the level of the sea appears to have sunk in that time -no less than 13 Swedish feet.<a id="FNanchor_202" href="#Footnote_202" class="fnanchor">[202]</a> All these facts, with many more -which it is unnecessary to enumerate, make the gradual depression, -not only of the Baltic, but of the whole northern ocean, a matter of -certainty.</p> - -<div class="footnote"> - -<p><a id="Footnote_202" href="#FNanchor_202" class="label">[202]</a> Frisii Opera, tom. iii. p. 274.</p> - -</div> - -<p>393. Supposing these changes of level between the sea and land to be -sufficiently ascertained, the supposition which at first occurs is, -that the motion -<span class="pagenum" id="Page_446">- 446 -</span> has been in the sea rather than in the land, and that -the former has actually descended to a lower level. The imagination -naturally feels less difficulty in conceiving, that an unstable fluid -like the sea, which changes its level twice every day, has undergone a -permanent depression in its surface, than that the land, the <i>terra -firma</i> itself, has admitted of an equal elevation. In all this, -however, we are guided much more by fancy than reason; for, in order to -depress or elevate the absolute level of the sea, by a given quantity, -in any one place, we must depress or elevate it by the same quantity -over the whole surface of the earth; whereas no such necessity exists -with respect to the elevation or depression of the land. To make -the sea subside 30 feet all round the coast of Great Britain, it is -necessary to displace a body of water 30 feet deep over the whole -surface of the ocean. The quantity of matter to be moved in that way is -incomparably greater than if the land itself were to be elevated; for -though it is nearly three times less in specific gravity, it is as much -greater in bulk, as the surface of the ocean is greater than that of -this island.</p> - -<p>394. Besides, the sea cannot change its level, without a proportional -change in the solid bottom on which it rests. Though there be reason to -suppose -<span class="pagenum" id="Page_447">- 447 -</span> that such changes in the bottom do actually take place, yet -they are probably much slower and more imperceptible than those which -we are here considering. It is evident, therefore, that the simplest -hypothesis for explaining those changes of level, is, that they proceed -from the motion, upwards or downwards, of the land itself, and not -from that of the sea. As no elevation or depression of the sea can -take place, but over the whole, its level cannot be affected by local -causes, and is probably as little subject to variation as any thing to -be met with on the surface of the globe.</p> - -<p>395. Other observations, however, made on different shores from the -preceding, give greater certainty to this conclusion, and make it -clear, that the motion or change which we are now treating of is not to -be ascribed to the sea itself.</p> - -<p>The observations just mentioned prove, that the level of the North -Sea is lower now than it was heretofore; but it appears, that in the -Mediterranean, the opposite takes place. Very accurate observations -made by <span class="smcap">Manfredi</span>, render it certain, that the superficies of -the Hadriatic was higher about the middle of the last century, than -toward the beginning of the Christian era.</p> - -<p>Some repairs that were carrying on in the cathedral church of Ravenna, -in the year 1731, -<span class="pagenum" id="Page_448">- 448 -</span> afforded him an opportunity of observing, that the -ancient, and probably original, pavement, was four feet and a half -below the present, and nearly a foot under the level of the sea at high -water.<a id="FNanchor_203" href="#Footnote_203" class="fnanchor">[203]</a> Now, when the church was built, this cannot have been the -position of the pavement, relatively to the level of the sea, for it -would have subjected the floor to be under water twice in twenty-four -hours, and must have done so the more unavoidably, because at that -time (the beginning of the fifth century) the walls of Ravenna were -washed by the sea. The fact that this pavement is under the high-water -mark, by the quantity just mentioned, was ascertained by actual -levelling. This result was confirmed by similar facts, observed by -<span class="smcap">Zendrini</span> at Venice.</p> - -<div class="footnote"> - -<p><a id="Footnote_203" href="#FNanchor_203" class="label">[203]</a> Commentarii Academiæ Bononiensis, tom. ii. pars 1ma, p. -237, &c. and pars 2da, p. 1. &c.</p> - -</div> - -<p>396. Manfredi himself attributes all this to the elevation of the -surface of the sea, and has entered into a long calculation to -ascertain at what rate that surface may be supposed to rise, on account -of the earth and sand brought down by the rivers, and spread out over -the bottom of the sea. But as the fact of the rise of the level -<span class="pagenum" id="Page_449">- 449 -</span> of the -sea is not general, and as the contrary is observed in the north seas, -as already proved, this hypothesis will not explain the apparent rise -in the level of the Hadriatic.</p> - -<p>397. Though a local subsidence, or settling of the ground, could hardly -account for this change, the pavement being perfect in its level, and -the walls of the cathedral without any shake, yet a subsidence that -has extended to a great tract, as to the whole of Italy, if the mass -moved has continued parallel to itself, and changed its place slowly, -will agree very well with the appearances. The facts here stated are -also the more deserving of attention, that about Ravenna, the land, at -the same time that it has sunk in its level, has extended its surface, -and has encroached on the sea. Since the time of <span class="smcap">Augustus</span>, -the line of the coast has been carried farther out by about three -miles.<a id="FNanchor_204" href="#Footnote_204" class="fnanchor">[204]</a> This last is the undoubted effect of the degradation of the -land by the rivers; and here we have very clear evidence of the forces, -both under and above the surface, producing their respective effects -at the same time, so that while the surface is raised by earth brought -down by the rivers, every given point in -<span class="pagenum" id="Page_450">- 450 -</span> the ground is depressed and -let down to a lower level.<a id="FNanchor_205" href="#Footnote_205" class="fnanchor">[205]</a></p> - -<div class="footnote"> - -<p><a id="Footnote_204" href="#FNanchor_204" class="label">[204]</a> Manfredi, <i>ibid.</i></p> - -<p><a id="Footnote_205" href="#FNanchor_205" class="label">[205]</a> On the coast of Dalmatia also, the rising of the level -of the sea has been remarked, particularly at the ruins of Diocletian's -palace of Spalatro.</p> - -</div> - -<p>398. On the southern coast of Italy similar facts have been observed. -<span class="smcap">Breislac</span>, in his <i>Topographia Fisica della Campagnia di -Roma</i>,<a id="FNanchor_206" href="#Footnote_206" class="fnanchor">[206]</a> from certain appearances in the Gulfs of Baja and -Naples, concludes, that at the beginning of the Christian era, the -level of the sea was lower on that part of the coast than it is -now. The facts which he mentions are the following: <i>1mo</i>, The -remains of an ancient road are now to be seen in the Gulf of Baja -at a considerable distance from the land. <i>2do</i>, Some ancient -buildings belonging to Porto Giulio are at present covered by the sea. -<i>3tio</i>, Ten columns of granite at the foot of Monte Nuovo, which -appear to have belonged to the Temple of the Nymphs, are also nearly -covered by the sea. <i>4to</i>, The pavement of the Temple of Serapis -is now somewhat lower than the high water mark, though it cannot be -supposed that this edifice when built was exposed to the inconvenience -of having its floor frequently under water. <i>5to</i>, The ruins of a -palace, -<span class="pagenum" id="Page_451">- 451 -</span> built by Tiberius in the island of Caprea, are now entirely -covered by the sea.</p> - -<div class="footnote"> - -<p><a id="Footnote_206" href="#FNanchor_206" class="label">[206]</a> Cap. vi. p. 300.</p> - -</div> - -<p>Thus, it appears that the level of the sea is sinking in the more -northern latitudes, and rising in the Mediterranean, and it is evident -that this cannot happen by the motion of the sea itself. The parts -of the ocean all communicating with one another, cannot rise in one -place and fall in another; but, in order to maintain a level surface, -must rise equally or fall equally over the whole of its extent. If, -therefore, we place any confidence in the preceding observations, and -they are certainly liable to no objection, either from their own nature -or the character of the observers, we must consider it as demonstrated, -that the relative change of level has proceeded from the elevation or -depression of the land itself. This agrees well with the preceding -theory, which holds, that our continents are subject to be acted upon -by the expansive forces of the mineral regions; that by these forces -they have been actually raised up, and are sustained by them in their -present situation.</p> - -<p>399. According to some other facts stated by the same ingenious -author, it appears, that on the coast of Italy the progress of the -sea in ascending, or of the land in descending, has not -<span class="pagenum" id="Page_452">- 452 -</span> been uniform -during the period above mentioned, but that different oscillations -have taken place; so that, from about the beginning of the Christian -era, till some time in the middle ages, the sea rose to be sixteen -feet higher than at present, from which height it has descended till -it became lower than it is now, and from that state of depression it -is now rising again. Breislac infers this from two facts, which he -combines very ingeniously with the preceding, viz. the remains of some -ancient buildings, at the foot of Monte Nuovo, five or six feet above -the present level of the sea, in which are found the shells of some -of those little marine animals that eat into stone: And again, the -marble columns of the temple of Serapis, which are also perforated -by pholades, to the height of sixteen feet above the ground. All -these changes Breislac ascribes to the motion of the sea itself; a -supposition which, as we have seen, cannot possibly be admitted, since -nothing can permanently affect the level of the sea in one place, which -does not affect it in all places whatsoever.</p> - -<p>400. Appearances, which indicate such alternations as have just been -mentioned in the level of the sea, are to be met with on some other -coasts. In England, on the coast of Lincolnshire, the remains of a -forest have been observed, which are -<span class="pagenum" id="Page_453">- 453 -</span> now entirely covered by the -sea.<a id="FNanchor_207" href="#Footnote_207" class="fnanchor">[207]</a> The submarine stratum which contains the remains of this -forest, can be traced into the country to a great distance, and is -found throughout all the fens of Lincolnshire. The stratum itself is -about four feet thick; it is covered in some places by a bed of clay -sixteen feet thick, and under it for twenty feet more is a bed of soft -mud, like the scourings of a ditch, mixed with shells and silt.</p> - -<div class="footnote"> - -<p><a id="Footnote_207" href="#FNanchor_207" class="label">[207]</a> Phil. Trans. 1799, p. 145.</p> - -</div> - -<p>Here then we have a stratum which must have been once uppermost on the -surface of the dry land, though one part of it is now immersed under -the sea, and another covered with earth, to the depth of sixteen feet. -A change of level in the sea itself will not explain these appearances: -they can only be explained by supposing the whole tract of land to -have subsided, which is the hypothesis adopted by the author of the -description in the Transactions, M. <span class="smcap">Corria de Serra</span>; the -subsidence, however, is not here understood to arise from the mere -yielding of some of the strata immediately underneath, but is conceived -to be a part of that geological system of alternate depression and -elevation of the surface, which probably extends to the whole mineral -kingdom. To reconcile all the different -<span class="pagenum" id="Page_454">- 454 -</span> facts, I should be tempted to -think, that the forest which once covered Lincolnshire, was immersed -under the sea by the subsidence of the land to a great depth, and at a -period considerably remote; that when so immersed, it was covered over -with the bed of clay which now lies on it, by deposition from the sea, -and the washing down of earth from the land; that it has emerged from -this great depth till a part of it has become dry land; but that it is -now sinking again, if the tradition of the country deserves any credit, -that the part of it in the sea is deeper under water at present than -it was a few years ago. This might also serve to reconcile, in some -measure, the phenomena of this submarine forest with the appearances -which indicate an extension of the land on the coast of Lincolnshire. -Indeed the extension of the land is no direct proof, either of its own -elevation, or of the depression of the sea, as we may conclude from the -instance of Ravenna already mentioned.</p> - -<p>401. We have concluded from the facts stated above, that the level of -the sea rises in the Mediterranean, and sinks in the more northern -latitudes; and thence some have suspected, that the level of the sea -had in general a tendency to rise towards the equator, and to sink -towards -<span class="pagenum" id="Page_455">- 455 -</span> the poles. This is the notion of Frisi, as has been already -remarked, and he suggests, that this rise of the sea may be owing to a -slight acceleration in the earth's diurnal motion. But there are facts -which show, that between the tropics the relative level of the sea -and land has sunk, and is lower at present than it was at some former -period, probably not extremely remote. The opinion of Frisi, therefore, -is unsupported by observation, and, as has been already shown, cannot -be justified from theory.</p> - -<p>Between the tropics, islands are formed from the mere accumulation -of coral; and it is the peculiarity of those regions, to produce -rocks that have not passed through the usual process of mineral -consolidation.<a id="FNanchor_208" href="#Footnote_208" class="fnanchor">[208]</a> The islets, however, which are thus formed, must -have their bases laid on a solid rock, though perhaps at a great -depth; and it is not probable, that after they are once raised above -the surface of the sea, they can still rise farther, except by some -elevation of the rock which serves as their foundation.<a id="FNanchor_209" href="#Footnote_209" class="fnanchor">[209]</a><span class="pagenum" id="Page_456">- 456 -</span> Now, -at Palmerston island, which comprehends nine or ten low islets, that -may be reckoned the heads of a great reef of coral rock, Captain -Cook informs us of his having seen, "far beyond the reach of the -sea, even in the most violent storms, elevated coral rocks, which, -on examination, appeared to have been perforated in the same manner -that the rocks are that now compose the outer edge of the reef. This -evidently shows," he adds, "that the sea had formerly reached so far; -and some of these perforated rocks were almost in the centre of the -island."<a id="FNanchor_210" href="#Footnote_210" class="fnanchor">[210]</a></p> - -<div class="footnote"> - -<p><a id="Footnote_208" href="#FNanchor_208" class="label">[208]</a> Dr Foster, in his Voyage round the World, (vol. ii. p. -146,) gives an instance in the South Sea Islands, where the surface of -the island, though entirely a coral rock, was raised forty feet above -the level of the sea.</p> - -<p><a id="Footnote_209" href="#FNanchor_209" class="label">[209]</a> A very curious account of the formation of such islands -is given by A. Dalrymple, Esq., in the Philosophical Transitions, vol. -lvii. p. 394.</p> - -<p><a id="Footnote_210" href="#FNanchor_210" class="label">[210]</a> Cook's Third Voyage, vol i. p. 221.</p> - -</div> - -<p>The same excellent navigator, giving an account of the peninsula at -Cape Denbigh, remarks: "It appeared to me, that this peninsula must -have been an island in remote times; for there were marks of the sea -having flowed over the isthmus."</p> - -<p>402. We are here touching on one of those subjects, where we feel much -the want of accurate and ancient observations, and where it is not from -the infancy, but the maturity of science that any thing approaching -to certainty can be looked for. The utmost that we can expect at -present, -<span class="pagenum" id="Page_457">- 457 -</span> is an anticipation, which future ages must certainly modify -and correct. The best thing, in the mean time, that can be done for the -advancement of this branch of geological knowledge, is to ascertain -with exactness the relative level of the sea, and of such points upon -the land as can be distinctly marked, and pointed out to succeeding -ages. This is not so easy as it may at first appear. Where every object -changes, it is difficult to find a measure of change, or a fixed point -from which the computation may begin. The astronomers already feel -this inconvenience, and when they would refer their observations to -an immoveable plane, that shall preserve its position the same in all -ages, they meet with difficulties, which cannot be removed but by a -profound mathematical investigation.</p> - -<p>In geology, we cannot hope to be delivered from this embarrassment in -the same manner; and we have no resource but to multiply observations -of the difference of level; to make them as exact as possible, and -to select points of comparison that have a chance of being long -distinguished. The improvements in barometrical measurements, which -give such facility to the determination of heights, along with so -considerable a degree of accuracy, will furnish an accumulation of -facts that must one day be of great value to the geologist.</p> - - -<hr class="chap x-ebookmaker-drop" /> - -<div class="chapter"> -<p><span class="pagenum" id="Page_458">- 458 -</span></p> - -<h2 class="nobreak" id="Note_xxii"><span class="smcap">Note xxii. § 123.</span></h2> -</div> - -<p class="caption3nb"><i>Fossil Bones.</i></p> - - -<p>403. The remains of organized bodies, at present included in the solid -parts of the globe, may be divided into three classes. The first -consists of the shells, corals,-and even bodies of fish, and amphibious -animals, which are now converted into stone, and make integrant -parts of the solid rock. All these are parts of animals that existed -<i>before the formation of the present land</i>, or even of the rocks -whereof it consists. These remains have been already treated of, and -the evidence which they furnish must ever be regarded as of the utmost -importance in the theory of the earth. The second class consists of -remains, which, by the help of stalactitical concretions, are converted -into stone. These are the exuviæ of animals, which existed on the -very same continents on which we now dwell, and are no doubt the most -ancient among their inhabitants, of which any monument is preserved. In -comparison of the first class, they must, nevertheless, be considered -as of very modern origin.</p> - -<p>404. The third class consists of the bones of animals found in the -loose earth or soil; these have not acquired a stony character, and -their nature -<span class="pagenum" id="Page_459">- 459 -</span> appears to be but little changed, except by the progress -of decomposition and of mouldering into earth. No decided line can be -drawn between the antiquity of this and the preceding class, as there -may be between the preceding and the first. In some instances, the -objects of this third class may be coeval with those of the second; in -general, they must be accounted of later origin, as they are certainly -not preserved in a manner so well fitted for long continuance.</p> - -<p>405. The animal remains of the second class, are generally found in -the neighbourhood of limestone strata, and are either enveloped or -penetrated by calcareous, or sometimes ferruginous matter. Of this -sort are the bones found in the rock of Gibraltar, and on the coast -of Dalmatia. The latter are peculiarly marked for their number, and -the extent of the country over which they are scattered, leaving it -doubtful whether they are the work of successive ages, or of some -sudden catastrophe that has assembled in one place, and overwhelmed -with immediate destruction, a vast multitude of the inhabitants of the -globe. These remains are found in greatest abundance in the islands of -Cherso and Osero ; end always in what the Abbé <span class="smcap">Fortis</span> calls -an <i>ocreo-stalactitic earth</i>. The bones are often in the state -of mere splinters, the broken and confused relics of various animals, -concreted with fragments of marble -<span class="pagenum" id="Page_460">- 460 -</span> and lime, in clefts and chasms of -the strata.<a id="FNanchor_211" href="#Footnote_211" class="fnanchor">[211]</a> Sometimes human bones are said to be found in these -confused masses.</p> - -<div class="footnote"> - -<p><a id="Footnote_211" href="#FNanchor_211" class="label">[211]</a> Travels into Dalmatia, p. 449.</p> - -</div> - -<p>406. A very remarkable collection of bones in this state is found -in the caves of Bayreuth in Franconia. Many of these belong, as is -inferred with great certainty from the structure of their teeth, to -a carnivorous animal of vast size, and having very little affinity -to any of those that are now known. The bones are found in different -states, some being without any stalactitical concretion, and having -the calcareous earth still united to the phosphoric acid, so that -they belong to the third, rather than the second, of the preceding -divisions. In others, the phosphoric acid has wholly disappeared, and -given place to the carbonic.</p> - -<p>The number of these bones, accumulated in the same place, is matter of -astonishment, when it is considered, that the animals to which they -belonged were carnivorous, so that more than two can never have lived -in the same cavern at the same time. The caves of Bayreuth seem to have -been the den and the tomb of a whole dynasty of unknown monsters, that -issued from this central spot to devour the feebler inhabitants of the -woods, during a long succession of ages, before -<span class="pagenum" id="Page_461">- 461 -</span> man had subdued the -earth, and freed it from all domination but his own.</p> - -<p>407. The fossil bones of the second and third class, but chiefly of the -third, have now afforded matter of conjecture and discussion for more -than a century. The facts with respect to them are very numerous and -interesting, but can be considered here only very generally.</p> - -<p>The remains of this kind, consist of the bones only of large animals, -so that they have generally been compared with those of the elephant, -the rhinoceros, the hippopotamus, or other animals of great size The -bones of smaller animals have also been found, but much more rarely -than the other. It is usually remarked, that the bones thus discovered -in the earth are larger than those of the similar living animals.</p> - -<p>Another general fact concerning these remains, is, that they are found -in all countries whatsoever, but always in the loose or travelled -earth, and never in the genuine strata. Since the year 1696, when the -attention of the curious was called to this subject, by the skeleton -of an elephant dug up in Thuringia, and described by Tentzelius,<a id="FNanchor_212" href="#Footnote_212" class="fnanchor">[212]</a> -there is hardly a country in Europe which has not afforded instances -of the -<span class="pagenum" id="Page_462">- 462 -</span> same kind. Fossil bones, particularly grinders and tusks of -elephants, have been found in other places of Germany, in Poland, -France, Italy, Britain, Ireland, and even Iceland.<a id="FNanchor_213" href="#Footnote_213" class="fnanchor">[213]</a> Two countries, -however, afford them in greater abundance by far than any other part of -the known world; namely, the plains of Siberia in the old continent, -and the flat grounds on the banks of the Ohio in the new.<a id="FNanchor_214" href="#Footnote_214" class="fnanchor">[214]</a></p> - -<div class="footnote"> - -<p><a id="Footnote_212" href="#FNanchor_212" class="label">[212]</a> Phil. Trans. vol. xix. p. 757.</p> - -<p><a id="Footnote_213" href="#FNanchor_213" class="label">[213]</a> A grinder of an elephant found in Iceland, is described -by <i>Bartholinus</i>, Acta Hafniens. vol. i. p. 83.</p> - -<p><a id="Footnote_214" href="#FNanchor_214" class="label">[214]</a> The fossil bones on the Ohio are described in two papers -by Mr P. Collinson, Phil. Trans. vol. lvii. p. 464 and 468.</p> - -</div> - -<p>408. When the bones in Siberia were first discovered, they were -supposed to belong to an animal that lived under ground, to which they -gave the name of the <i>mammouth</i>; and the credit bestowed on this -absurd fiction, is a proof of the strong desire which all men feel -of reconciling extraordinary appearances with the regular course of -nature. Much skill, however, in natural history was not required to -discover that many of the bones in question resembled those of the -elephant, particularly the grinders and the tusks of that animal. -Others resembled the bones of the rhinoceros; and a head of that kind, -having the -<span class="pagenum" id="Page_463">- 463 -</span> hide preserved upon it, was found in Siberia, and is still -in the imperial cabinet at Petersburgh.</p> - -<p>Pallas has described the fossil bones which he found in the museum at -Petersburgh, on his being appointed to the superintendence of it, and -enumerates, not only bones that belong, in his opinion, to the elephant -and rhinoceros, but others that belong to a kind of buffalo, very -different from any now known, and of a size vastly greater.<a id="FNanchor_215" href="#Footnote_215" class="fnanchor">[215]</a> He has -also described, in another very curious memoir, the bones of the same -kind that he met with in his travels through the north-east parts of -Asia.</p> - -<div class="footnote"> - -<p><a id="Footnote_215" href="#FNanchor_215" class="label">[215]</a> Novi Comment Petrop. tom. xiii. (1768,) p. 436, and tom. -xvii. p. 576, &c.</p> - -</div> - -<p>The fossil bones found on the banks of the Ohio, resemble in many -things those of Siberia; like them they are contained in the soil or -alluvial earth, and never in the solid strata; like them too they are -no otherwise changed from their natural state, than by being sometimes -slightly calcined at the surface; they are also of great size, and in -great numbers, being probably the remains of several different species.</p> - -<p>409. Two inquiries concerning these bones have excited the curiosity -of naturalists; first, to discover among the living tribes at present -inhabiting -<span class="pagenum" id="Page_464">- 464 -</span> the earth, those to which the fossil remains may with the -greatest probability be referred; and, secondly, to find out the cause -why these remains exist in such quantities, in countries where the -animals to which they belong, whatever they be, are at present unknown. -The solution of the first of these questions, is much more within our -reach than the second, and at any rate must be first sought for.</p> - -<p>On the authority of so eminent a naturalist as Pallas, the bones from -Siberia may safely be referred to the elephant, the rhinoceros, and -buffalo, as mentioned above, though perhaps to varieties of them with -which we are not now acquainted. With respect to the bones of North -America, the question is more doubtful, for they have this particular -circumstance attending them, viz. that along with the thighbones, -tusks, &c. which might be supposed to belong to the elephant, grinders -are always found of a structure and form entirely different from -the grinders of that animal.<a id="FNanchor_216" href="#Footnote_216" class="fnanchor">[216]</a> Some naturalists, particularly M. -<span class="smcap">Daubenton</span>, referred these grinders to the hippopotamus; but -Dr W. <span class="smcap">Hunter</span> appears to have proved, in a very satisfactory -manner, that they cannot -<span class="pagenum" id="Page_465">- 465 -</span> have belonged to either of the animals just -mentioned, but to a <i>carnivorous</i> animal of enormous size, the -race of which, fortunately for the present inhabitants of the earth, -seems now to be entirely extinct.<a id="FNanchor_217" href="#Footnote_217" class="fnanchor">[217]</a> The foundation of Dr Hunter's -opinion is, that in these grinders the enamel is merely an external -covering; whereas, in the elephant, and other animals destined to live -on vegetable food, the enamel is intermixed with the substance of the -tooth.<a id="FNanchor_218" href="#Footnote_218" class="fnanchor">[218]</a></p> - -<div class="footnote"> - -<p><a id="Footnote_216" href="#FNanchor_216" class="label">[216]</a> See Mr Collinson's papers, above referred to. Phil. -Trans. vol. lvii.</p> - -<p><a id="Footnote_217" href="#FNanchor_217" class="label">[217]</a> Phil. Trans. vol. lviii. p. 3, &c.</p> - - -<p><a id="Footnote_218" href="#FNanchor_218" class="label">[218]</a> A fossil grinder in the collection of <span class="smcap">John -Macgowan</span>, Esq. of Edinburgh, answers nearly to Mr Collinson's -description, and is very well represented by the figure which -accompanies it. This grinder weighs four pounds one-fourth avoirdupois; -the circumference of the <i>corona</i> is eighteen inches; the coat of -enamel is one-fourth of an inch thick; there are five double teeth; in -Mr Collinson's specimen there are only four.</p> - -</div> - -<p>410. Though this argument appears to be of considerable weight, yet -<span class="smcap">Camper</span>, who was greatly skilled in comparative anatomy, -and who had studied this subject with particular attention, was of -opinion, that these grinders belong to a species of elephant. This -opinion he states in a letter to Pallas, who had found grinders and -other bones of this same animal, on the western -<span class="pagenum" id="Page_466">- 466 -</span> declivity of the Ural -mountains.<a id="FNanchor_219" href="#Footnote_219" class="fnanchor">[219]</a> Camper denies that the animal is carnivorous, because -the <i>incisores</i>, or canine teeth, are wanting; and he argues -farther, from the weight of the head, which may be inferred from the -weight of the grinders, that the neck must have been short, and the -animal must have been furnished with a <i>proboscis</i>. He afterwards -abandoned the latter hypothesis, and gave it as his opinion that -the <i>incognitum</i> was neither carnivorous, nor a species of the -elephant.<a id="FNanchor_220" href="#Footnote_220" class="fnanchor">[220]</a></p> - -<div class="footnote"> - -<p><a id="Footnote_219" href="#FNanchor_219" class="label">[219]</a> Acta Acad. Petrop. tom. i. (1777,) pars posterior, p. -213, &c.</p> - -<p><a id="Footnote_220" href="#FNanchor_220" class="label">[220]</a> <i>Ibid.</i> tom. ii. (1784,) p. 262.</p> - -</div> - -<p>411. Nevertheless, <span class="smcap">Cuvier</span>, in a <i>mémoire</i> read before the -National Institute of Paris, maintains, that the fossil bones of the -new Continent, as well as most of those of the old, belong to certain -species of the elephant; of which, at least, two do not now exist, and -are only known from remains preserved in the ground. He distinguishes -them thus:<a id="FNanchor_221" href="#Footnote_221" class="fnanchor">[221]</a></p> - -<div class="footnote"> - -<p><a id="Footnote_221" href="#FNanchor_221" class="label">[221]</a> Mémoires de l'Institut National, Sciences Physiques, -tom. ii. p. 19, &c.</p> - -</div> - -<p><i>Elephas mammonteus</i>,—<i>maxillâ obtusiore, lamellis molarium -tenuibus, rectis</i>.</p> - -<p><i>Elephas Americanus</i>,—<i>molarities multicuspidibus, lamellis -post detritionem quadric-lobatis</i>.</p> - -<p>The latter species, which is meant to include the <i>animal -incognitum</i>, is said to have lived, not -<span class="pagenum" id="Page_467">- 467 -</span> only in America, but in -many parts of the old Continent. Yet some late inquiries into the -structure of the teeth of graminivorous animals, and particularly of -the elephant, make it very improbable that the <i>incognitum</i> has -belonged to this genus.<a id="FNanchor_222" href="#Footnote_222" class="fnanchor">[222]</a> The grinders of the elephant have been -found to consist of three substances, enamel, bone, and what is called -the <i>crusta petrosa</i>, applied in layers, or folds contiguous to -one another; and no vestige of this structure appears in the grinders -of the unknown animal of the Ohio.<a id="FNanchor_223" href="#Footnote_223" class="fnanchor">[223]</a><span class="pagenum" id="Page_468">- 468 -</span> At the same time, Dr Hunter's -assertion, that this animal was carnivorous, is rendered doubtful, not -only by the want of <i>canine</i> teeth, but also from the resemblance -between its grinders and those of the wild boar, which Mr Home has -observed to be considerable.<a id="FNanchor_224" href="#Footnote_224" class="fnanchor">[224]</a> The grinder of the boar is similar -to that of the elephant, in the extent of the masticating surface, but -not at all in the internal structure; and the same is true of the tooth -of the <i>animal incognitum</i>, so that a considerable probability -is established, that it and the boar are of the same genus, and both -destined to live occasionally either on animal or vegetable food.</p> - -<div class="footnote"> - -<p><a id="Footnote_222" href="#FNanchor_222" class="label">[222]</a> See Mr Home's Observations on the Teeth of Graminivorous -Animals, Phil. Trans. 1799. Also, an Essay on the Structure of the -Teeth, by Dr Blake.</p> - -<p><a id="Footnote_223" href="#FNanchor_223" class="label">[223]</a> In a paper inserted in the fourth volume of the American -Philosophical Transactions, an account is given of two different -grinders that are found at the Salt Licks near the Ohio. One of them -resembles the grinder of the elephant, and may have belonged to the -<i>Elephas Americanus</i> of Cuvier; the other agrees pretty nearly -with the grinder of Dr Hunter's <i>animal incognitum</i>. The author -of the paper thinks that the <i>animal incognitum</i> was not wholly -carnivorous, as the incisores, or canine teeth, are never found. At the -Great Bone Lick, bones of smaller animals, particularly of the buffalo -kind, have been discovered. The saline impregnation of the earth at -these Licks must no doubt have contributed to the preservation of the -bones. Trans. American Phil. Soc. vol. iv. (1799,) p. 510, &c.</p> - -<p><a id="Footnote_224" href="#FNanchor_224" class="label">[224]</a> Observations on the Grinding Teeth of the wild boar and -<i>animal incognitum</i>. Phil. Trans. 1801, p. 319.</p> - -</div> - -<p>412. Another <i>animal incognitum</i> found in South America has -been described by Cuvier, and appears to be of a different genus -from the <i>incognitum</i> of the North. Thus, if we include the two -<i>incognita</i> of America, the <i>elephas mammonteus</i>, the unknown -buffalo of Pallas, and the great animal of Bayreuth, we have at least -five distinct genera, or species of the animal kingdom, which existed -on our continents formerly, but do not exist on them now. The number is -probably much greater: Pallas mentions fossil horns of a gazelle, of -an unknown species; and horns of deer are often found, that cannot be -referred to any species now existing. Those extinct -<span class="pagenum" id="Page_469">- 469 -</span> races have been -remarkable for their size: some of the ancient elephants appear to have -been three times as large as any of the present.<a id="FNanchor_225" href="#Footnote_225" class="fnanchor">[225]</a></p> - -<div class="footnote"> - -<p><a id="Footnote_225" href="#FNanchor_225" class="label">[225]</a> Camper, Nov. Acta Petrop. tom. ii. (1784) p. 257.</p> - -</div> - -<p>413. The inhabitants of the globe, then, like all the other parts -of it, are subject to change. It is not only the individual that -perishes, but whole <i>species</i>, and even perhaps <i>genera</i>, -are extinguished. It is not unnatural to consider some part of this -change as the operation of man. The extension of his power would -necessary subvert the balance that had before been established between -the inhabitants of the earth, and the means of their subsistence. Some -of the larger and fiercer animals might indeed dispute with him, for -a long time, the empire of the globe; and it may have required the -arm of a Hercules to subdue the monsters which lurked in the caves of -Bayreuth, or roamed on the banks of the Ohio. But these, with others -of the same character, were at length exterminated: the more innocent -species fled to a distance from man; and being forced to retire into -the most inaccessible parts, where their food was scanty, and their -migration checked, they may have degenerated from, the size and -strength of their ancestors, and some species may have been entirely -extinguished.</p> - -<p>But besides this, a change in the animal kingdom seems to be a part of -the order of nature, -<span class="pagenum" id="Page_470">- 470 -</span> and is visible in instances to which human power -cannot have extended. If we look to the most ancient inhabitants of the -globe, of which the remains are preserved in the strata themselves, -we find in the shells and corals of a former world hardly any that -resemble exactly those which exist in the present. The species, except -in a few instances, ate the same, but subject to great varieties. The -vegetable impressions on slate, and other argillaceous stones, can -seldom be exactly recognised; and even the insects included in amber -are different from those of the countries in which the amber is found.</p> - -<p>414. Supposing, then, the changes which have taken place in the -qualities and habits of the animal creation, to be as great as those -in their structure and external form, we can have no reason to wonder -if it should appear that some have formerly dwelt in countries from -which the similar races are now entirely banished. The power of living -in a different climate, of enduring greater degrees of cold or of -heat, or of subsisting on different kinds of food, may very well have -accompanied the other changes. Though one species of elephant may -now be confined to the southern parts of Asia, another may have been -able to endure the severer climates of the north; and the same may -be true of the buffalo or the rhinoceros. In all this no physical -<span class="pagenum" id="Page_471">- 471 -</span> -impossibility is involved; though whether it is a probable solution of -the difficulty concerning the origin of these animal remains, can only -be judged of from other circumstances.</p> - -<p>415. If we consider attentively the facts that respect the Siberian -fossil bones, there will appear insurmountable objections to every -theory that supposes them to be exotic, and to have been brought into -their present situation from a distant country.</p> - -<p>The extent of the tract through which these bones are scattered, is a -circumstance truly wonderful. Pallas assures us,<a id="FNanchor_226" href="#Footnote_226" class="fnanchor">[226]</a> that there is not -a river of considerable size in all the north of Asia, from the Tanais, -which runs into the Black Sea, to the Anadyr, which falls into the Gulf -of Kamtchatka, in the sides or bottom of which bones of elephants and -other large animals have not been found. This is especially the case -where the rivers run in plains through gravel, sand, clay, &c.; among -the mountains, the bones are rarely discovered. The extent of the tract -just mentioned exceeds four thousand miles; and how the bones could -be distributed over all that extent, by any means but by the animals -having -<span class="pagenum" id="Page_472">- 472 -</span> lived there, it seems impossible to conceive. No torrent nor -inundation could have produced this effect, nor could the bones brought -in that way have been laid together so as to form complete skeletons.</p> - -<div class="footnote"> - -<p><a id="Footnote_226" href="#FNanchor_226" class="label">[226]</a> De Reliquiis Animalium exoticorum, per Asiam Borealem -repertis.—"Nov. Comment Petrop. tom. xvii. (1772,) p. 576.</p> - -</div> - -<p>416. One fact recorded by the same author, seems calculated to remove -all uncertainty. It is that of the carcase of a rhinoceros, almost -entire, and covered with the hide, found in the earth in the banks of -the river Wilui, which falls into the Lena below Jakutsk.<a id="FNanchor_227" href="#Footnote_227" class="fnanchor">[227]</a> Some of -the muscles and tendons were actually adhering to the head when Pallas -received it. The head, after being dried in an oven, is still preserved -in the museum at Petersburgh. The preservation of the skin and muscles -of this natural mummy, as Pallas calls it, was no doubt brought -about by its being buried in earth that was in a state of perpetual -congelation; for the place is in the parallel of 64°, where the ground -is never thawed but to a very small depth below the surface.</p> - -<div class="footnote"> - -<p><a id="Footnote_227" href="#FNanchor_227" class="label">[227]</a> Pallas <i>ubi supra</i>, p. 586. Also, Voyages de -Pallas, tom. iv. p. 131.</p> - -</div> - -<p>But by what means can we account for the carcase of a rhinoceros being -buried in the earth, on the confines of the polar circle? Shall we -ascribe it to some immense torrent, which, sweeping across the deserts -of Tartary, and the mountains of Altai, transported the productions of -India -<span class="pagenum" id="Page_473">- 473 -</span> to the plains of Siberia, and interred in the mud of the Lena -the animals that had fed on the banks of the Barampooter or the Ganges? -Were all other objections to so extraordinary a supposition removed, -the preservation of the hide and muscles of a dead animal, and the -adhesion of the parts, while it was dragged for 2000 miles over some -of the highest and most rugged mountains in the world, is too absurd -to be for a moment admitted. Or shall we suppose that this carcase has -been floated in by an inundation of the sea, from some tropical country -now swallowed up, and of which the numerous islands of the Indian -Archipelago are the remains? The heat of a tropical climate, and the -putrescence naturally arising from it, would soon, independently of -all other accidents, have stripped the bones of their covering. Indeed -this <i>instantia singularis</i>, as in every sense it may properly be -called, seems calculated for the express purpose of excluding every -hypothesis but one from being employed to explain the origin of fossil -bones. It not only excludes the two which have just been mentioned, -but it excludes also that of Buffon, viz. that these bones are the -remains of animals which lived in Siberia, when the arctic regions -enjoyed a fine climate, and a temperature like that which southern Asia -now possesses. From the preservation of the flesh and hide of this -rhinoceros, it is plain, that when the body was buried in the -<span class="pagenum" id="Page_474">- 474 -</span> earth, -the climate was much the same that it is now, and the cold sufficient -to resist the progress of putrefaction.</p> - -<p>Pallas takes notice of the inconsistency of the state of this skeleton, -with the hypothesis of Buffon; but he does not observe that the -inconsistency is equally great between it and his own hypothesis, the -importation of the fossil bones by an inundation of the sea, and that -flesh or muscle must have been entirely consumed long before it could -be carried by the waves to the parallel of 64°, from any climate which -the rhinoceros at present inhabits.</p> - -<p>417. The presence of petrified marine objects in places where some of -the fossil bones are found, is no proof that the latter have come from -the sea, though it is produced as such both by Pallas himself, and -afterwards by Kirwan. These marine bodies are the shells and corals -that have been parts of calcareous rocks, from which being detached -by the ordinary progress of disintegration, they are now contained in -the beds of sand or gravel where the animal remains are buried. They -have nothing in common with these remains; they are real stones, and -belong to another, and a far more remote epochs. Such objects being -found in the same place where the bones lie, argues only that the -strata in the higher grounds, from which the gravel has come, are -calcareous; and nothing can show in a stronger -<span class="pagenum" id="Page_475">- 475 -</span> light the necessity of -distinguishing the different condition of fossil bodies, united by the -mere circumstance of contiguity, before we draw any inference as to -their having a common origin. If the marine remains were in the same -condition with the bones; if they were in no respect mineralized; then -the conclusion, that both had been imported by the sea, would have -great probability; but without that, their present union must be held -as casual, and can give no insight into the origin of either.</p> - -<p>418. On the whole, therefore, no conclusion remains, but that these -bones have belonged to species of elephants, rhinoceros, &c. which -inhabited the very countries where their remains are now buried, and -which could endure the severity of the Siberian climate. The rhinoceros -of the Wilui certainly lived on the confines of the Polar Circle, and -was exposed to the same cold while alive, by which, when dead, its body -has been so long, and so curiously preserved.</p> - -<p>These animals may also have lived occasionally farther to the south, -among the valleys between the great ranges of mountains that bound -Siberia on that side. Fossil bones are but rarely found in these -valleys, probably because they have been washed down from thence into -the plains. We must observe, too, that those animals may have migrated -with the seasons, and by that means avoided the rigorous -<span class="pagenum" id="Page_476">- 476 -</span> winter of the -high latitudes. The dominion of man, by rendering such migration to -the larger animals difficult or impossible, must have greatly changed -the economy of all those tribes, and narrowed the circle of their -enjoyments and existence. The heaps in which the fossil bones appear to -be accumulated in particular places, especially in North America, have -a great appearance of being connected with the migrations of animals, -and the accidents that might bring multitudes of them into the same -spot.</p> - -<p>What holds of Siberia and of North America, is applicable, <i>a -fortiori</i>, to all the other places where animal remains are found -in the same condition. Thus we are carried back to a time when many -larger species of animals, now entirely extinct, inhabited the earth, -and when varieties of those that are at present confined to particular -situations, were, either by the liberty of migration, or by their -natural constitution, accommodated to all the diversities of climate. -This period, though beyond the limits of ordinary chronology, is -posterior to the great revolutions on the earth's surface, and the -latest among geological epochs.</p> - - -<hr class="chap x-ebookmaker-drop" /> - -<div class="chapter"> -<p><span class="pagenum" id="Page_477">- 477 -</span></p> - -<h2 class="nobreak" id="Note_xxiii"><span class="smcap">Note xxiii. § 128.</span></h2> -</div> - -<p class="caption3nb"><i>Geology of</i> <span class="smcap">Kirwan</span> <i>and</i> <span class="smcap">De Luc</span>.</p> - - -<p>419. The two champions of the Neptunian system, who have distinguished -themselves most by their hostility to Dr <span class="smcap">Hutton</span>, are <span class="smcap">De -Luc</span> and <span class="smcap">Kirwan</span>. They have carried on their attack nearly -on the same plan, and have employed against their antagonist the -weapons both of theology and science. With a spirit as injurious to the -dignity of religion, as to the freedom of philosophical inquiry, they -have disregarded a maxim enforced by the authority of Bacon, and by all -our experience of the past; "<i>Tanto magis hæc vanitas inhibenda venit -et coërcenda, quia, ex divinorum et humanorum male-sana admixtione, non -solum educitur philosophia phantastica, sed etiam religio hæretica. -Itaque salutare admodum est, si mente sobriâ, fidei tantum dentur quæ -fidei sunt</i>."<a id="FNanchor_228" href="#Footnote_228" class="fnanchor">[228]</a></p> - -<div class="footnote"> - -<p><a id="Footnote_228" href="#FNanchor_228" class="label">[228]</a> The whole passage is deserving of attention, and it -seems as if the prophetic spirit of Bacon had addressed it to the -cosmologists of the present day. "<i>Pessima enim res errorem</i> -<span class="smcap">apotheosis</span>, <i>et pro peste intellectús habenda est, si vanis -accedat veneratio. Huic autan vanitati nonnulli ex modernis summâ -levitate ita indulserunt, ut, in primo capitolo</i> <span class="smcap">Geneseos</span>, -<i>et aliis Scripturis Sacris, philosophiam naturalem fundari conati -sunt:</i> Inter <span class="smcap">viva</span> quærentes <span class="smcap">mortua</span>.—"Nov. Organum, lib. i. -aphor. 65</p> - -</div> - -<p><span class="pagenum" id="Page_478">- 478 -</span></p> - -<p>Proceeding, accordingly, in direct opposition to rules that, have never -yet been violated with impunity, and mistaking the true object of a -theory of the earth, they carry back their inquiries to a period prior -to the present series of causes and effects, where, having neither -experience nor analogy to direct them, they pretend to be guided by -a superior light. They would have us to consider their geological -speculations as a commentary on the text of <span class="smcap">Moses</span>; they -endeavour to explain the action of creative power, and, with indiscreet -curiosity, would tear off the veil which the hand of the prophet has -so wisely respected. But the veil cannot be torn off, and all that is -behind it must be to man as that which never has existed.</p> - -<p>420. M. De Luc has nevertheless treated very diffusely of the history -of the solar system, previous to the establishment of the present laws -of nature, and has dwelt on it with great complacency, and singular -minuteness of detail. His tenth letter to <span class="smcap">La Metherie</span> has the -following title:</p> - -<p>"On the History of the Earth, from the time when that planet was -penetrated by <i>light</i>, till the appearance of the sun; a portion -of time which includes the origin of heat, and of the figure of the -earth; of its primeval strata, of the ancient sea, of our continents, -as the bottom of -<span class="pagenum" id="Page_479">- 479 -</span> that sea, of the great chains of mountains, and of -vegetation."<a id="FNanchor_229" href="#Footnote_229" class="fnanchor">[229]</a></p> - -<div class="footnote"> - -<p><a id="Footnote_229" href="#FNanchor_229" class="label">[229]</a> Journal de Physique, tom. 37. (1790,) partie 2de, p. -332. As I may not have done justice to this extraordinary title, -it may be right to present it in the original. "Sur l'Histoire -de la <span class="smcap">Terre</span>, depuis que cette planette fut penetrée de -<span class="smcap">lumiere</span>, jusqu'à l'apparition du <span class="smcap">soleil</span>; espace de -tems qui renferme les <span class="smcap">origines</span> de la <i>chaleur</i>, et de -la <i>figure</i> de notre globe; de ses <i>couches primordiales</i>, -de <i>l'ancienne mer</i>, de nos <i>continens</i>, comme fond de -cette mer, de leurs grandes chaînes de <i>montagnes</i>, et de la -<i>vegetation</i>."</p> - -</div> - -<p>I must confess that I am unacquainted with every thing of this letter -but the title; and could not easily be prevailed on to follow any man -who professedly goes out of nature in search of knowledge; who pretends -to give the history of our planetary system when there was no sun, -and to enumerate the events which took place between the existence of -that luminary, and the existence of light. The absurdity of such an -undertaking admits of no apology; and the smile which it might excite, -if addressed merely to the fancy, gives place to indignation when it -assumes the air of philosophic investigation.</p> - -<p>421. It sets, however, in a strong light, the inconsistencies that may -be observed in the intellectual character of the same individual, to -consider that the author of this strange and inconsistent -<span class="pagenum" id="Page_480">- 480 -</span> reverie, is, -nevertheless, an excellent observer, and well skilled in experimental -inquiries. It will hardly be believed that he who writes the history of -the earth before the formation of the sun, is versed in the principles -of inductive reasoning; and that he has added much to the stock of -geological knowledge, having observed accurately, and described with -great perspicuity and candour. His <i>Lettres Physiques</i> are full -of valuable and just observations, though accompanied with reasonings -that do not seem always entitled to the same praise; and in another -work he has succeeded where many men of genius had failed, and has -made considerable improvements in a branch of the mathematics, -without borrowing almost any assistance from the principles of that -science.<a id="FNanchor_230" href="#Footnote_230" class="fnanchor">[230]</a></p> - -<div class="footnote"> - -<p><a id="Footnote_230" href="#FNanchor_230" class="label">[230]</a> Essai sur les Modifications de l'Atmosphere.</p> - -</div> - -<p>422. Some of the same observations apply to Mr Kirwan. His Geological -Essays have also for their object to explain the first origin of -things; and to say that he has not succeeded, in an attempt where no -man ever can succeed, implies no reproach on the execution of his -work, whatever it may do on the design. We have indeed no criterion by -which the execution of it can be estimated: what would in any other -place be a blemish, may be here deserving of praise; and if the work -is full of confusion and -<span class="pagenum" id="Page_481">- 481 -</span> perplexity, these are qualities inherent in -the subject which it is intended to describe. It were, no doubt, to -be wished, that after emerging into the regions of day, Mr Kirwan had -been as successful in copying the beauty and simplicity of nature, as -in representing the disorder and inconsistency of the chaotic mass. -But his cosmology is without unity in its principles, or consistency -in its parts; the causes introduced, are, for the most part, such as -will account for one set of appearances just as well as for another; -or, if any of them is likely to prove inadequate to the effect ascribed -to it, a new and arbitrary hypothesis is always ready to come to its -assistance. The information given is seldom exact: a multitude of facts -brought together, without the order and discussion essential to precise -knowledge; and an infinity of quotations, amassed without criticism or -comparison, afford proofs of extensive reading, but of the most hasty -and superficial inquiry. Thus we have seen passages from <span class="smcap">Ulloa</span> -and <span class="smcap">Frisi</span>, produced in support of opinions, which, when fairly -stated, they had the most direct tendency to overthrow.</p> - -<p>423. In one respect, the geological writings of Kirwan are far inferior -to De Luc's: They are evidently the productions of a man who has not -seen nature with his own eyes; who has studied -<span class="pagenum" id="Page_482">- 482 -</span> mineralogy in cabinets, -or in books only; but who has seldom beheld fossils in their native -place. With the balance in his hand, and the external characters of -<span class="smcap">Werner</span> in his view, he has examined minerals with diligence, -and has discovered many of those marks which serve to ascertain their -places, in a system of artificial arrangement. But to <i>reason</i> and -to <i>arrange</i> are very different occupations of the mind; and a man -may deserve praise as a mineralogist, who is but ill qualified for the -researches of geology.</p> - -<p>424. The same hurry and impatience are visible in the manner in which -his argument against Dr Hutton is usually conducted. He has seldom been -careful to make himself master of the opinions of his adversary; and -what he gives as such, and directs his reasonings against, have often -no resemblance to them whatsoever. Without any intention to deceive -others, but deceived himself, he usually begins with misrepresenting Dr -Hutton's notions, and then proceeds to the refutation of them. In this -imaginary contest, it will readily be supposed, that he is in general -successful: when a man has the framing both of his own argument, and -that of his antagonist, he must be a very unskilful logician if he does -not come off with the advantage.</p> - -<p><span class="pagenum" id="Page_483">- 483 -</span></p> - -<p>425. It is but justice, however, to the Neptunists, to acknowledge, -that they are not all liable to the censure of beginning their -researches from a period antecedent to the existence of the laws of -nature. This absurdity does not, so far as I know, infect the system of -Werner. That mineralogist has not proposed to explain the first origin -of things, though he has supposed, at some former period, a condition -of the globe very unlike the present, viz. the entire submersion of the -solid under the fluid part.</p> - - -<hr class="chap x-ebookmaker-drop" /> - -<div class="chapter"> -<h2 class="nobreak" id="Note_xxiv"><span class="smcap">Note xxiv. § 129.</span></h2> -</div> - -<p class="caption3nb"><i>System of</i> <span class="smcap">Buffon</span>.</p> - - -<p>426. The affinity of Dr Hutton's theory to that of Buffon, is nothing -more than what arises from their making use of the same agents, viz. -fire and water, in producing the present condition of the earth's -surface. In almost all other respects the two theories are extremely -different. The order in which those agents are employed in them, is -directly opposite, as has already been remarked; Buffon introducing the -action of fire first, and of water only in the second place, to waste -and destroy mineral bodies, -<span class="pagenum" id="Page_484">- 484 -</span> and afterwards to dispose them anew, and -arrange them into strata. He makes no provision for the consolidation -of these strata, nor any for their angular elevation; he has no means -of explaining the unstratified rocks; nor any, but one extremely -imperfect, for explaining the inequalities of the earth's surface.</p> - -<p>Again, Buffon mistook, in some degree, the true object of a theory of -the earth; and though he did not go back, like the geologists just -named, to a time when the laws of nature were not fully established, -he begins from a condition of things too unlike the present to be the -basis of any rational speculation. He does not, indeed, undertake to -examine the state of our planetary system before the sun existed; for -from such extravagance, even when most disposed to indulge his fancy, -he would surely have revolted. But he treats of the world, when the -earth and the planets had just ceased to be a part of the sun, and were -newly detached from the body of that luminary.<a id="FNanchor_231" href="#Footnote_231" class="fnanchor">[231]</a></p> - -<div class="footnote"> - -<p><a id="Footnote_231" href="#FNanchor_231" class="label">[231]</a> According to Buffon, the granite is the true solar -matter, unchanged but by its congelation.</p> - -</div> - -<p>This hypothesis concerning the origin of the planets, contrived chiefly -to account for the circumstance -<span class="pagenum" id="Page_485">- 485 -</span> of their motion being all in the -same direction, and in other respects not only unsupported, but even -inconsistent with the principle of gravitation, has nothing in common -with a theory, confined as Dr Hutton's is, within the field which must -for ever bound our inquiries, and not venturing to speculate about the -earth, when in a condition totally different from the present.</p> - -<p>427. In what relates to the future, the two systems are not more like -than in what relates to the past Buffon represents the cooling of our -planet, and its loss of heat, as a process continually advancing, and -which has no limit, but the final extinction of life and motion over -all the surface, and through all the interior, of the earth. The death -of nature herself is the distant but gloomy object that terminates -our view, and reminds us of the wild fictions of the Scandinavian -mythology, according to which, <i>annihilation</i> is at last to extend its -empire even to the gods. This dismal and unphilosophic vision was -unworthy of the genius of Buffon, and wonderfully ill suited to the -elegance and extent of his understanding. It forms a complete contrast -to the theory of Dr Hutton, where nothing is to be seen beyond the -continuation of the present order; where no latent seed of evil -threatens final destruction to the whole; and where the -<span class="pagenum" id="Page_486">- 486 -</span> movements are -so perfect, that they can never terminate of themselves. This is surely -a view of the world more suited to the dignity of <span class="smcap">Nature</span>, and -the wisdom of its <span class="smcap">Author</span>, than has yet been offered by any -other system of cosmology.</p> - -<p>428. I have often quoted Buffon in, the course of these -<i>Illustrations</i>, and most commonly for the purpose of combating -his opinions; but I am very sensible, nevertheless, of the obligations -under which he has laid all the sciences connected with the natural -history of the earth.</p> - -<p>The extent and variety of his knowledge, the justness of his -reasonings, the greatness of his views, his correct taste, and manly -eloquence, qualified him, better, perhaps, than any other individual, -to compose the History of Nature. The errors into which he Has fallen, -are almost all the unavoidable consequences of the circumstances in -which he was placed; and if their amount is estimated by the proportion -that they bear to the general excellence of the work, they will be -reckoned but of small account. Buffon began to write when many parts -of natural history had made but little progress; when the quantity -of authentic information was small, and when scientific and correct -description was hardly to be found. Many of the greatest and most -important facts in geology were quite unknown, -<span class="pagenum" id="Page_487">- 487 -</span> and scarcely any part -of the mineral kingdom had been accurately surveyed; and, with such -materials as this state of things afforded, it is not wonderful if some -parts of the edifice he erected have not proved so solid and durable -as the rest. Had he appeared somewhat later; had he been farther -removed from the time when reasonings <i>a priori</i> usurped the -place of induction; and had he been as willing to correct the errors -into which he had been betrayed by imperfect information, as he was -ingenious in defending them, his work would probably have reached as -great perfection, as it is given for any thing without the sphere of -the accurate sciences to attain. If he had examined the natural history -of the earth more with his own eyes, and been as careful to delineate -it with fidelity as force; if he had listened with greater care to -the philosophers around him; had he attended to the demonstrations of -<span class="smcap">Newton</span> more, and despised the arrangements of <span class="smcap">Linnæus</span> -less; he would have produced a work, as singular for its truth as for -its beauty, and would have gone near to merit the eulogy pronounced -by the enthusiasm of his countrymen, <span class="smcap">Majestati Naturæ par -ingenium</span>.</p> - - -<hr class="chap x-ebookmaker-drop" /> - -<div class="chapter"> -<p><span class="pagenum" id="Page_488">- 488 -</span></p> - -<h2 class="nobreak" id="Note_xxv"><span class="smcap">Note xxv. § 130.</span></h2> -</div> - -<p class="caption3nb"><i>Figure of the Earth.</i></p> - - -<p>429. That the earth is a spheroidal body, compressed at the poles, -or elevated at the equator, is a fact established by many accurate -experiments; and though these experiments do not exactly coincide, as -to the degree of oblateness which they give to that spheroid, they -agree sufficiently to put it beyond all dispute, that the earth, though -solid, has nearly the same figure which it would assume if fluid, in -consequence of its rotation on its axis.</p> - -<p>Now, it is not at all obvious, to what physical cause this phenomenon -is to be ascribed. The earth, as it exists at present, has none of the -conditions that render the assumption of the figure of equilibrium in -any way necessary to it. Constituted as it is, its parts cohere with -forces incomparably too great to obey the laws of statical pressure, -or to assume any one figure rather than another, on account of the -centrifugal tendency which results from its revolution on its axis. -There is no necessity that its superficies should be every where level, -or perpendicular to the direction of gravity, nor that every two -columns, -<span class="pagenum" id="Page_489">- 489 -</span> standing on the same base, any where within it, and reaching -from thence to any two points of the surface, should be of such weights -as precisely to balance one another. Neither of these, indeed, is at -all conformable to fact. They are, however, the very suppositions on -which the determination of the spheroid of equilibrium is founded; and -as they certainly do in no degree belong to the earth, it seems strange -that the result deduced from them should be in any way applicable to -it. This coincidence remains, therefore, to be explained; and it must -greatly enhance the merit of any geological system, if it can connect -this great and enigmatical phenomenon with the other facts in the -natural history of the earth.</p> - -<p>430. To establish such a connection, has, accordingly, been a favourite -object with geologists, whether they have embraced the Neptunian or -Volcanic theory: both have thought that they were entitled to suppose -the primeval fluidity of the globe, the one by water, and the other -by fire; and in whatsoever way that fluidity was produced, the result -of it could be no other than the spheroidal figure of the whole mass, -agreeably to the laws of hydrostatics. If in this fluid state the earth -was homogeneous, the spheroid would be accurately elliptical, and the -compression at the poles would be 1/230 of the radius of -<span class="pagenum" id="Page_490">- 490 -</span> the equator; -if the fluid was denser toward the centre, the flattening would be -less: and in either case, the body, as it acquired solidity, may be -supposed to have retained its spheroidal figure with little variation. -But though the fluidity of the earth will account for the phenomenon -of its oblate figure, it may reasonably be questioned, whether this -fluidity can be admitted, in consistency with other appearances. -According to what is established above, none of the appearances in the -mineral kingdom indicate more than a partial fluidity in any former -condition of the earth. The present strata, made up as they are of the -ruins of former strata, though softened by heat, have not been rendered -fluid by it, and have even possessed their softness in parts, and in -succession, not altogether, nor at the same time.</p> - -<p>The unstratified, and more crystallized substances, were cast in the -bosom of others, which were solid at the time when they were fluid. In -all this, therefore, there is no indication of a fluidity prevailing -through the whole mass, or even over the whole surface of the earth, -and therefore nothing that can explain the spheroidal figure which it -has acquired. The supposition, then, of the entire body of the earth, -or even of its external crust, having been fluid, though it might -account for the compression at -<span class="pagenum" id="Page_491">- 491 -</span> the poles, does not connect that fact -with the other facts in the natural history of the globe, and fails, -therefore, in the point most essential to a theory. It is liable, also, -to other objections, whether it be conceived to have proceeded from -fire or from water; whether it has happened on the principles of Buffon -or of Werner.</p> - -<p>431. First, let us suppose that the fluidity of the earth, or of the -external crust of it, at least to a certain depth, proceeded from a -solution of the whole in the waters of the ocean; and, waving all the -objections that have been stated to this hypothesis, on account of -the absolute insolubility of many mineral substances in water, let us -suppose them all soluble in a certain degree, and let us compute the -quantity of the menstruum, which, on the suppositions most favourable -to the system, must have been required to this great geologico-chemical -operation.</p> - -<p>The siliceous earth, though not soluble in water <i>per se</i>, yet, -after being dissolved in that fluid by means of an alkali, was found by -Dr Black, in his analysis of the Geyser water, to remain suspended in -a quantity of water, between 500 and 1000 times its own weight. This -is one of the facts most favourable to the Neptunian theory; and that -every advantage may be given to that theory, we shall take the least of -the numbers just mentioned, and suppose that siliceous -<span class="pagenum" id="Page_492">- 492 -</span> earth may be -dissolved or suspended in 500 times its weight of water.</p> - -<p>Taking this for the extreme degree of insolubility of mineral -substances, (though there are many of which the insolubility is -absolute, or, to speak in the language of calculation, infinitely -great,) we may suppose the insolubility of all the rest, or the -quantities of water in which they are dissolved, to be ranged in a -descending scale from 500 to 0, the extreme degree of deliquescence. -Then, taking the arithmetical mean between these extremes, it will give -us 250, as the proportion of water in which mineral substances may at -an average be dissolved. But this average is much less than the truth; -for the quantity of siliceous earth is great in comparison of any of -the rest, and the mineral substances that are extremely soluble in -water are but in a small quantity; therefore, when we suppose mineral -bodies, at a medium, to be soluble in 250 times their own weight of -water, we make a supposition extremely favourable to the Neptunian -system.</p> - -<p>432. This is the proportion between the <i>weight</i> of the solvent, -and of the substances held in solution: to have the proportion of their -<i>bulks</i>, we may suppose the specific gravity of mineral bodies in -general to be to that of water as 5 to 2, and then we have the ratio -of bulks, that of -<span class="pagenum" id="Page_493">- 493 -</span> 250 × 5 to 2 × 1, or of 625 to 1. It follows, then, -that minerals in general cannot be supposed soluble in less than 625 -times their bulk of water.</p> - -<p>433. Again, it must be allowed to the Neptunists, that the fluidity -of the whole earth is not necessary to account for its assuming the -spheroidal figure. It is sufficient if the whole of that crust or shell -of matter was fluid, which is contained between the actual surface -of the terrestrial spheroid, and the surface of the sphere inscribed -within it; that is, of the sphere which has for its diameter the polar -axis of the earth. The whole of the minerals which compose this shell, -must at least have been dissolved in water, and have formed the chaotic -mass of Mr Kirwan. The volume of the water required for this was not -less than 625 times the bulk of the spheroidal shell that has just been -mentioned.</p> - -<p>But, assuming the difference between the polar axis and the equatorial -diameter to be 1/300 of the latter, which is the supposition most -agreeable to the phenomena, it is easy to show that the magnitude of -the above spheroidal shell, or the difference between the solid content -of the earth, and the sphere inscribed in it, is greater than 1/151 and -less than 1/150 of the whole earth; so -<span class="pagenum" id="Page_494">- 494 -</span> that the earth is less than 151 -times the spheroidal shell.</p> - -<p>The volume of the water, therefore, necessary to hold in solution the -materials of this shell, is to the volume of the whole earth as 625 -to 151, or in a greater ratio than that of four to one: and such, -therefore, at the very least, is the quantity of water which Mr Kirwan -supposes, after it ceased to act in its chemical capacity, to have -retired into caverns in the interior of the earth. Thus the Neptunists, -in their account of the spheroidal figure of the earth, are reduced -to a cruel dilemma, and are forced to choose between a physical and a -mathematical impossibility.</p> - -<p>If we would inquire whether the opinion of the igneous origin of -minerals, as commonly received by the Vulcanists, is capable of -affording a better solution of this difficulty, the theory of M. de -Buffon is the first that presents itself.</p> - -<p>434. That philosopher considers the existence of the spheroidal figure -as a proof that the whole of the earth must have been originally fluid; -and as the fluidity of the whole can only be ascribed to fusion, he has -supposed that the earth was originally a mass of melted matter struck -off from the sun by the collision of a comet; and that this mass, when -made to revolve on its -<span class="pagenum" id="Page_495">- 495 -</span> axis, put on a spheroidal figure, which it has -retained, though now cooled down to congelation.</p> - -<p>This system need not be considered in detail; the foundation of it is -laid in such defiance of the principles of geometry and mechanics, that -the architect, notwithstanding all the fertility of his invention, and -all the resources of his genius, was never able to give any solidity to -the structure.</p> - -<p>But it will be said, that we may take a part of the system, without -venturing on the whole, and may suppose that the earth, or at least -the external crust of it, has been fluid by fire, though we do not -inquire into the cause of this fire, or into the manner in which it was -produced.</p> - -<p>It is indeed true, that, when this is done, we have not the same sort -of absurdity to encounter that we met with in the Neptunian system, and -that the Volcanic theory does not, like it, come into direct collision -with an axiom of geometry. There are, nevertheless, great objections -to it; for though all the phenomena of the mineral kingdom attest a -fluidity of igneous origin, yet it is a fluidity that was never more -than partial; and though it has been over all the earth, has been over -it in succession only. Besides, we are not entitled -<span class="pagenum" id="Page_496">- 496 -</span> to assume the -existence, and again the disappearance of such a great quantity of -heat, without assigning some cause for the change.</p> - -<p>435. Since, then, neither the hypothesis of the Neptunists or the -Vulcanists, affords any good explanation of the figure of the earth, or -such a one as can connect it with the other appearances in its natural -history, it remains to inquire, whether the system that supposes a -partial and successive fluidity, like Dr Hutton's, has any resource for -explaining this great phenomenon.</p> - -<p>Of this subject Dr Hutton has not treated; and when I was first made -acquainted with his system, it appeared to me a very serious objection -to it, that it did not profess to give an explanation of so important -a fact as the oblate figure of the earth. On considering the matter -more closely, however, I found that there were principles contained -in it from which a very satisfactory solution (and, I think, the only -satisfactory solution) of that difficulty might be deduced. This -solution I shall endeavour to explain, in as far, at least, as is -necessary for the purpose of general illustration.</p> - -<p>It is laid down in Dr Hutton's theory, that the surface of the earth is -perpetually changed by the <i>detritus</i> of the land; and that from -the -<span class="pagenum" id="Page_497">- 497 -</span> materials thus afforded, new horizontal strata are perpetually -formed at the bottom of the sea. If this be true, and if the -alternations of decay and renovation have been often repeated, it is -certain, that the figure of the earth, whatever it may have originally -been, must be brought at length to coincide with the spheroid of -equilibrium.</p> - -<p>436. Here it is necessary to remark, that the expressions, <i>figure -of the earth</i>, and <i>surface of the earth</i> are each of them -occasionally taken in two different senses.</p> - -<p>The surface of the earth, in its most obvious sense, is that which -bounds the whole earth, and includes all its inequalities; it is a -surface extremely irregular, rising to the tops of the mountains, -descending to the bottoms of the valleys, and having the continuity -of its curvature often interrupted, or suddenly changed. This may be -called the <i>actual</i> surface, and the figure bounded by it, the -<i>actual</i> figure, of the earth.</p> - -<p>The surface of the earth, in another sense, is one that is every where -horizontal, and is the same which water assumes when at rest.</p> - -<p>This superficies is determined by the circumstance of its being -constantly perpendicular to the direction of gravity; it is the surface -marked out by levelling, and may be supposed to be continued from the -sea, through the -<span class="pagenum" id="Page_498">- 498 -</span> interior of the land, till it meet the sea again. The -figure bounded by this horizontal surface, may properly be called the -<i>statical</i> figure of the earth.</p> - -<p>When it is said that the figure of the earth is an oblate spheroid, it -is the statical, not the actual figure which is meant; and the degrees -of the meridian which astronomers measure, are also referred to the -superficies of the former.</p> - -<p>437. Suppose now a body like the earth, but with its actual figure -infinitely more irregular, having a sea circumfused around it, the -water will descend into the lowest situations, and will so arrange -itself, that its surface shall be perpendicular every where to the -plumb-line, or to the direction of gravity, in which state only it can -remain at rest. The figure of the superficies which the sea must thus -take will be of a continuous curvature, and will return into itself; -though it may, if the actual figure is very irregular, be far either -from a sphere or a spheroid. If, however, we suppose the solid parts -of this mass subject to be dissolved or worn away, and carried down to -the ocean, there will be a tendency to give to the whole body the same -figure that it would have assumed, if it had been entirely fluid, and -subject to the -<span class="pagenum" id="Page_499">- 499 -</span> laws of hydrostatics. This tendency is the result of -two principles.</p> - -<p>438. Let us suppose the body just described to have no rotation, so -that the particles of it are actuated only by the forces of cohesion -and of attraction.</p> - -<p>It is then clear, that every particle taken away by attrition from -the parts above the level of the sea, and deposited under the surface -of it, makes the general figure more compact, bringing the remoter -parts nearer to the centre of gravity of the whole; so that, in time, -if the body is homogeneous, all the points of the surface will become -equally distant from that centre. Thus the <i>actual</i> figure changes -continually, and approaches nearer to the <i>statical</i>.</p> - -<p>While this change is going forward in the actual figure, there is -another produced on the statical, that tends very much to accelerate -the final coincidence, of the two.</p> - -<p>The effect of the inequalities of the land, that rise above the -horizontal surface, is, by their attraction, to render the parts of -that surface immediately under them, more convex, <i>cæteris paribus</i>, than -the rest. Again, where there are parts of extraordinary depth in the -sea, that is, where the solid and denser parts are far removed from the -surface of the ocean, the curvature of the superficies -<span class="pagenum" id="Page_500">- 500 -</span> of the sea is -thereby diminished, and that superficies is rendered less convex than -it would be if the sea were shallower. These propositions are both -capable of strict mathematical demonstration. Hence the taking away of -any particle of matter from the top of a mountain tends to diminish the -curvature of the horizontal surface under the mountain, where it is -greatest; and the deposition of the same particle at the bottom of the -sea, tends to increase the curvature of this superficies where it is -least. The general tendency, therefore, being to increase the curvature -where it is least, and to diminish it where it is greatest, must be -to bring about an uniform curvature throughout, that is, a spherical -figure. Thus, by the waste and subsequent stratification of the land, -the direction of gravity is continually altered; it is more and more -concentrated, and the figure brought nearer to that which a fluid would -assume.</p> - -<p>439. If now we suppose the body to revolve on its axis, all other -things remaining as before, the surface bounding the sea will become -different from what it was in the former case, and will be more swelled -out toward the middle or equatorial regions. The land above the level -of the sea will still, as before, be worn down and deposited in the -bottom of the sea, so as to form strata nearly parallel to its surface: -the tendency, therefore, -<span class="pagenum" id="Page_501">- 501 -</span> is to render the real figure of the planet -nearer to the statical. At the same time the <i>statical</i> figure is -changed, as explained above; so that the two figures mutually approach, -and the limit, or ultimate figure to which they tend, is one over which -the ocean might be diffused every where to the same depth, for then the -causes of change would entirely cease. But this figure is no other than -the spheroid of equilibrium, which, therefore, is the effect which the -waste and reconsolidation of the land would necessarily produce, if the -process were continued indefinitely, without interruption. In this, as -in many other instances, when a body is subject to the action of causes -by which its form is <i>gradually</i> changed, the figure best adapted -to resist those changes, is the figure which the changes themselves -ultimately produce.</p> - -<p>Also, whatever be the irregularities of density, the tendency to a -change of figure will not cease till the body is moulded into that -particular spheroid which admits of being covered with water every -where to the same depth.<a id="FNanchor_232" href="#Footnote_232" class="fnanchor">[232]</a> Thus -<span class="pagenum" id="Page_502">- 502 -</span> it appears, that a solid of an -irregular figure, and of irregular density, provided it be in part -covered with water; and be at the same time subject to waste above the -surface of the sea, and reconsolidation under it, has a tendency to -acquire, in time, the same figure that it would have acquired had it -been entirely fluid.</p> - -<p><span class="pagenum" id="Page_503">- 503 -</span></p> - -<div class="footnote"> - -<p><a id="Footnote_232" href="#FNanchor_232" class="label">[232]</a> In the same manner as a transition is thus made from an -irregular figure to a spheroid of equilibrium, so, if the actual figure -were at first more simple than the spheroid, it would still be changed -into this last by degrees.</p> - -<p>Let us conceive, for instance, that the earth is at rest, and is a -perfect sphere of solid matter, surrounded by an ocean every where of -equal depth, for example, of one mile. Then, if a rotatory motion be -communicated to it, so that it shall revolve on its axis in twenty-four -hours, in consequence of the centrifugal force, the water circumfused -about the sphere will immediately rise up under the equator, and will -become part of a spheroidal surface, (not elliptical, but nearly so,) -the equatorial diameter of which is greater than the polar axis, in the -ratio of 588 to 577 By this means the water will be accumulated at the -equator to the depth of nearly 2.5 miles, and form a zone surrounding -the earth, and extending about 37° on each side of the equator. The -remainder of the surface will be left dry, forming two vast circumpolar -continents, that reach 53° on every side of the poles, and that are -elevated in the middle more than four miles above the level of the sea.</p> - -<p>Such would be the state of our globe, on the hypothesis above laid -down; and, if there were no waste or destruction of the land, this -order of things would be permanent, and neither the solid nor fluid -part of the mass could ever acquire any other figure than that which -has been described. But, if the same laws be supposed to regulate the -action of the atmosphere in those circumstances, that do actually -regulate it according to the present constitution of the globe, the -vapours raised up from the surface of the sea, would be carried by the -winds over the land, where they would be condensed and precipitated in -rain. Thus, all the agents of destruction would be let loose on the two -great circumpolar continents; rivers would be formed; the land would -become deeply intersected by ravines; those ravines would gradually -open into wide valleys; the masses of greatest resistance would be -shaped into hills and mountains: and from a superficies originally -smooth and uniform, the same inequalities would be produced which at -present diversify the surface of the earth.</p> - -<p>While the parts of the sphere without the spheroid are thus continually -diminished, the loose earth and sand washed down from them, will be -deposited at the bottom of the sea, and will form strata parallel -to the surface of the superincumbent water. The actual and statical -figure are thus brought nearer one another; and, at the same time the -statical is changed, on the principle already explained, (the change in -the direction of gravity,) and is made continually to approximate to a -state, which when it has attained, no farther change can take place, -viz. an oblate elliptic spheroid, of which the surface is perpendicular -to the direction of gravity, having the equatorial diameter to the -polar axis in the ratio of 230 to 229.</p> - -</div> - -<p><span class="pagenum" id="Page_504">- 504 -</span></p> - -<p>440. In the preceding reasonings, we have supposed the process of decay -and subsequent stratification to be carried on without interruption, -till the whole of the land is covered by the sea. This supposition is -useful for explaining the nature of the forces which have determined -the figure of the earth; but there is no reason to think that it has -ever been realized in its full extent, the elevation of strata from the -bottom of the sea interrupting the progress, and producing new land -in one place, as the old decays in another. The very same land also, -which is wasted at its surface, may perhaps be lifted up by the forces -that are placed under it; or it may be let down, undergoing alterations -of its level, from causes that we do not perceive, but of which the -action is undoubted, (<a href="#sec_388">§ 388.</a>) But notwithstanding these interruptions, -the general tendency to produce in the earth a spheroidal figure may -remain, and more may be done by every revolution, to bring about the -attainment of that figure than to cause a deviation from it. This -figure, therefore, though never likely to be perfectly acquired, will -be the <i>limiting</i> or <i>asymptotic</i> figure, if it may be so -called, to which the earth will continually approach.</p> - -<p>441. If the preceding conclusions are just, and if the figure of -equilibrium is only an asymptotic figure, to which that of the earth -may approximate, -<span class="pagenum" id="Page_505">- 505 -</span> but cannot perfectly attain, we are not to be -surprised if considerable deviations from it are actually observed. -This has accordingly happened, insomuch, that the results deduced from -the most accurate measurement of degrees of the meridian, differ from -one another, in the oblateness they give to the earth, by nearly one -half of the quantity to be determined. When we compare the degrees -measured in France, and in some other countries of Europe, with -those measured in Peru, we obtain for the compression at the poles, -less than 1/300 of the radius of the earth. But when we compare the -degrees measured in France with one another, and with those lately -measured in England, we find that they are best represented by a -spheroid that has its compression 1/150 of its semi-axis.<a id="FNanchor_233" href="#Footnote_233" class="fnanchor">[233]</a> There -is reason to think, therefore, that the meridians are not elliptical; -and other observations seem to show, that they are not even similar -to one another; or that the earth is not, strictly speaking, a solid -of revolution; so, also, the comparison of the degree measured at -the Cape of Good Hope, with those measured on the -<span class="pagenum" id="Page_506">- 506 -</span> opposite side of -the equator, creates a suspicion, that the northern and southern -hemispheres are not perfectly alike, and that the earth is not equally -compressed at the Arctic and the Antarctic poles. These irregularities, -though they do not affect the general fact of the earth's compression -at the poles, show that the true statical figure is but imperfectly -attained; and though this may be accounted for, without having recourse -to the principles involved in our theory, it is in a manner very -unsatisfactory, and, by help of suppositions, not at all consistent -with the original fluidity ascribed to the whole mass, or to the -exterior crust of the earth.</p> - -<div class="footnote"> - -<p><a id="Footnote_233" href="#FNanchor_233" class="label">[233]</a> Exposition du Systéme du Monde, par La Place, p. 61, 2d -edit.</p> - -</div> - -<p>442. As the principles here laid down explain how a solid body may -attain very nearly the figure which a fluid would acquire in order to -preserve its parts in equilibrium; and since the oblate figure belongs -to other of the planets as well as the earth, and the globular to all -the great bodies of the universe, this suggests an analogy that goes -deep into the economy of nature, and extends far beyond the limits -within which the mineralogist is wont to confine his speculations.</p> - -<p>443. That no very irregular figure is found among the planetary bodies, -may therefore be considered as a proof of the universality of that -system of waste and reconsolidation that we have -<span class="pagenum" id="Page_507">- 507 -</span> been endeavouring to -trace in the natural history of the earth. A farther proof of the same -arises from considering, that for every given mass of matter, having a -given period of rotation, there are two different spheroids that answer -the conditions of establishing an equilibrium among its parts, the one -near to the sphere, and the other very distant from it, and so oblate -as to have a lenticular form. Thus the earth, supposing it homogeneous, -might either be in equilibrium, by means of the figure which it -actually has, or of one in which the polar was to the equatorial -diameter as 1 to 768. The same is true of the other planets; and yet we -no where find that this highly compressed spheroid is actually employed -by nature. The reason, no doubt, is, that in so oblate a spheroid, the -equilibrium between the gravitating and the centrifugal force is of -the kind that does not re-establish itself when disturbed; so that the -parts let loose, and not kept in their place by firm cohesion, would -fly off altogether. In such a body, the waste at the surface would -lead to an entire change of form, and therefore the constitution here -supposed could not be permanent.</p> - -<p>444. In the system of Saturn, we have a great deviation from the -general order, which, nevertheless, has led to a very unexpected -verification of some of the conclusions deduced above. A -<span class="pagenum" id="Page_508">- 508 -</span> principle -extremely like that which is the basis of all the foregoing reasonings, -led one of the greatest philosophers of the present age to discover -the revolution of Saturn's ring on its axis, and even to determine -the velocity of that revolution, such as it has been since found by -observation. <span class="smcap">La Place</span>, laying it down as a maxim, that nothing -in nature can exist, where there are causes of change, not balanced -or compensated by other causes,<a id="FNanchor_234" href="#Footnote_234" class="fnanchor">[234]</a> concluded, that the-parts of the -ring must be held from falling down to the body of the planet by some -other force than their mere cohesion to one another. Were it otherwise, -every particle detached from the ring, by any means, must descend in a -straight line, almost perpendicular to the surface of Saturn; and the -final destruction of the ring must be inevitable. The only force that -could balance this effect of gravitation, seemed to be a centrifugal -force, arising from the rotation of the ring on an axis passing through -its centre, and perpendicular to its plane. La Place proceeded to -inquire what celerity of rotation was adequate to this effect, and -found that one of ten hours and a quarter would be required, which is -almost precisely the time afterwards determined by Dr <span class="smcap">Herschel</span> -from actual observation. If, with this -<span class="pagenum" id="Page_509">- 509 -</span> rotation, the ring is a solid -annulus generated by the rotation of a very flat ellipsis about a given -point in its greater axis, coinciding with the centre of Saturn, it may -be so constituted, that the attraction of Saturn, combined with the -centrifugal force, may produce a force perpendicular to its surface, -and may enable detached parts to remain at rest, animals, for instance, -to walk on its surface, and fluids to be <i>in equilibrio</i>. The -system of Saturn is thus fortified against the lapse of time, as -effectually as that of the earth itself; and the means by which this is -accomplished, seem to prove, that the weapons which time employs, are -in both cases the same, viz. the slow wearing and decomposition of the -solid parts. This slow wearing may have produced the figure by which -its action is most effectually resisted.</p> - -<div class="footnote"> - -<p><a id="Footnote_234" href="#FNanchor_234" class="label">[234]</a> La Place, <i>ubi supra</i>, p. 242.</p> - -</div> - -<p>445. Thus Dr Hutton's theory of the earth comes at last to connect -itself with the researches of physical astronomy. The conclusion to be -drawn from this coincidence is to the credit of both sciences. When two -travellers, who set out from points so distant as the mineralogist and -the astronomer, and who follow routes so different, meet at the end of -their journey, and agree in their report of the countries through which -they have passed, it affords no slight presumption, that they have kept -the right way, -<span class="pagenum" id="Page_510">- 510 -</span> -and that they relate what they have actually seen.</p> - - -<hr class="chap x-ebookmaker-drop" /> - -<div class="chapter"> -<h2 class="nobreak" id="Note_xxvi"><span class="smcap">Note xxvi. § 133.</span></h2> -</div> - -<p class="caption3nb"><i>Prejudices relating to the Theory of the Earth.</i></p> - - -<p>446. Among the prejudices which a new theory of the earth has to -overcome, is an opinion, held, or affected to be held, by many, that -geological science is not yet ripe for such elevated and difficult -speculations. They would, therefore, get rid of these speculations, -<i>by moving the previous question</i>, and declaring that at present -we ought to have no theory at all. We are not yet, they allege, -sufficiently acquainted with the phenomena of geology; the subject is -so various and extensive that our knowledge of it must for a long time, -perhaps for ever, remain extremely imperfect. And hence it is, that the -theories hitherto proposed have succeeded one another with so great -rapidity, hardly any of them having been able to last longer than the -discovery of a new fact, or a fact unknown when it was invented. It has -proved insufficient to connect this fact with the phenomena already -known, and has therefore been justly abandoned. In this manner, they -say, have passed away the theories of Woodward, Burnet, Whiston, and -even of Buffon; -<span class="pagenum" id="Page_511">- 511 -</span> and so will pass, in their turn, those of Hutton and -Werner.</p> - -<p>447. This unfavourable view of geology, ought not, however, to be -received without examination; in science, presumption is less hurtful -than despair, and inactivity is more dangerous than error.</p> - -<p>One reason of the rapid succession of geological theories, is the -mistake that has been made as to their object, and the folly of -attempting to explain by them the first origin of things. This mistake -has led to fanciful speculations that had nothing but their novelty to -recommend them, and which, when that charm had ceased, were rejected -as mere suppositions, incapable of proof. But if it is once settled, -that a theory of the earth ought to have no other aim but to discover -the laws that regulate the changes on the surface, or in the interior -of the globe, the subject is brought within the sphere either of -observation or analogy; and there is no reason to suppose, that man, -who has numbered the stars, and measured their forces, shall ultimately -prove unequal to this investigation.</p> - -<p>448. Again, theories that have a rational object, though they be false -or imperfect in their principles, are for the most part approximations -to the truth, suited to the information at the -<span class="pagenum" id="Page_512">- 512 -</span> time when they were -proposed. They are steps, therefore, in the advancement of knowledge, -and are terms of a series that must end when the real laws of nature -are discovered. It is, on this account, rash to conclude, that in the -revolutions of science, what has happened must continue to happen, -and because systems have changed rapidly in time past, that they must -necessarily do so in time to come.</p> - -<p>He who would have reasoned so, and who had seen the ancient physical -systems, at first all rivals to one another, and then swallowed up by -the Aristotelian; the Aristotelian physics giving way to those of Des -Cartes; and the physics of Des Cartes to those of Newton; would have -predicted that these last were also, in their turn, to give place to -the philosophy of some later period. This is, however, a conclusion -that hardly any one will now be bold enough to maintain, after a -hundred years of the most scrupulous examination have done nothing but -add to the evidence of the <span class="smcap">Newtonian System</span>. It seems certain, -therefore, that the rise and fall of theories in times past, does not -argue, that the same will happen in the time that is to come.</p> - -<p>449. The multifarious and extremely diversified object of geological -researches, does, no doubt, render the first steps difficult, and -may very -<span class="pagenum" id="Page_513">- 513 -</span> well account for the instability hitherto observed in such -theories; but the very same thing gives reason for expecting a very -high degree of certainty to be ultimately attained in these inquiries.</p> - - -<p>Where the phenomena are few and simple, there may be several different -theories that will explain them in a manner equally satisfactory; -and in such cases, the true and the false hypotheses are not easily -distinguished from one another. When, on the other hand, the phenomena -are greatly varied, the probability is, that among them, some of those -<i>instantiæ crucis</i> will be found, that exclude every hypothesis -but one, and reduce the explanation given to the highest degree of -certainty. It was thus, when the phenomena of the heavens were but -imperfectly known, and were confined to a few general and simple facts, -that the Philolaic could claim no preference to the Ptolemaic system: -The former seemed a possible hypothesis; but as it performed nothing -that the other did not perform, and was inconsistent with some of our -most natural prejudices, it had but few adherents. The invention of the -telescope, and the use of more accurate instruments, by multiplying -and diversifying the facts, established its credit; and when not only -the general laws, but also the inequalities, and disturbances of -<span class="pagenum" id="Page_514">- 514 -</span> the -planetary motions were understood, all physical hypotheses vanished, -like phantoms, before the philosophy of <span class="smcap">Newton</span>. Hence the -number, the variety, and even the complication of facts, contribute -ultimately to separate truth from falsehood; and the same causes which, -in any case, render the first attempts toward a theory difficult, make -the final success of such attempts just so much the more probable.</p> - -<p>This maxim, however, though a general encouragement to the prosecution -of geological inquiries, does not amount to a proof that we are yet -arrived at the period when those inquiries may safely assume the form -of a theory. But that we are arrived at such a period, appears clear -from other circumstances.</p> - -<p>450. It cannot be denied, that a great multitude of facts, respecting -the mineral kingdom, are now known with considerable precision; and -that the many diligent and skilful observers, who have arisen in the -course of the last thirty years, have produced a great change in the -state of geological knowledge. It is unnecessary to enumerate them all; -<span class="smcap">Ferber</span>, <span class="smcap">Bergman</span>, <span class="smcap">De Luc</span>, <span class="smcap">Saussure</span>, -<span class="smcap">Dolomieu</span>, are those on whom Dr Hutton chiefly relied; and -it is on their observations and his own that his system is founded. -If it be said, that only a small part of the earth's surface has yet -been surveyed, and described -<span class="pagenum" id="Page_515">- 515 -</span> with such accuracy as is found in the -writers just named, it may be answered, that the earth is constructed -with such a degree of uniformity, that a tract of no very large extent -may afford instances of all the leading facts that we can ever observe -in the mineral kingdom. The variety of geological appearances which -a traveller meets with, is not at all in proportion to the extent of -country he traverses; and if he take in a portion of land sufficient -to include primitive and secondary strata, together with mountains, -rivers, and plains, and unstratified bodies in veins and in masses, -though it be not a very large part of the earth's surface, he may find -examples of all the most important facts in the history of fossils. -Though the labours of mineralogists have embraced but a small part of -the globe, they may therefore have comprehended a very large proportion -of the phenomena which it exhibits; and hence a presumption arises, -that the outlines, at least, of geology have now been traced with -tolerable truth, and are not susceptible of great variation.</p> - -<p>451. When the phenomena of any class are in general ambiguous, and -admit of being explained by different or even opposite theories; if few -of those exclusive facts are known, which admit but of one or a few -solutions, then we have no right to expect much from our endeavours to -generalise, except the knowledge -<span class="pagenum" id="Page_516">- 516 -</span> of the points where our information -is most deficient, and to which our observations ought chiefly to be -directed. But that many of the exclusive and unambiguous instances are -known, in the natural history of the globe, I think is evident from the -reasoning in the foregoing pages, where so many examples have occurred -of appearances that give the most direct negative to the Neptunian -system, and exclude it from the number of possible hypotheses, by -which the phenomena of geology can be explained. The abundance of such -instances is an infallible sign, that the mass of knowledge is in that -state of fermentation, from which the true theory may be expected to -emerge.</p> - -<p>452. Another indication of the same kind, is the near approach that -even the most opposite theories make, in some respects, to one another. -There are so many points of contact between them, that they appear -to approximate to an ultimate state, in which, however unwillingly, -they must at last coincide. That ultimate form, too, which all these -theories have a tendency to put on, if I am not deceived, is no other -than that of the Huttonian theory.</p> - -<p>453. The first example I shall take from the system of Saussure. It is -to be regretted, that this excellent geologist has no where given us a -complete account of his theory. Some of the -<span class="pagenum" id="Page_517">- 517 -</span> leading principles of it -are, however, unfolded in the course of his observations, and enable us -to form a notion of its general outline. It was evidently far removed -from the system of subterraneous heat, and seems, especially in the -latter part of the author's life, to have been very much accommodated -to the prevailing system of <span class="smcap">Werner</span>. Nevertheless, with so -little affinity between their general views, Saussure and Hutton agree -in that most important article which regards the elevation of the -strata. Saussure plainly perceived the impossibility of the strata -being formed in the vertical situations which so many of them now -occupy; and he takes great pains to demonstrate this impossibility, -from some facts that have been referred to above. He also believed that -this elevation had been given to strata that were originally level, by -a force directed upwards, or by the <i>refoulement</i> of the beds, not -by their falling in, as is the opinion of De Luc and some other of the -Neptunists.</p> - -<p>Now, whoever admits this principle, and reasons on it consistently, -without being afraid to follow it through all its consequences, must -unavoidably come very close to the Huttonian theory. He must see, that -a power which, acting from below, produced this great effect can never -have belonged to water, unless rarefied -<span class="pagenum" id="Page_518">- 518 -</span> into steam by the application -of heat. But if it be once admitted that heat resides in the mineral -regions, the great objection to Dr Hutton's system is removed; and -the theorist, who was furnished with so active and so powerful an -agent, would be very unskilful in the management of his own resources, -if he did not employ it in the work of consolidating as well as in -that of raising up the strata. A little attention will show, that it -is qualified for both purposes; though insuperable objections must, -no doubt, offer themselves, where the effects of compression are -not understood. We may safely conclude, then, that the accurate and -ingenious Geologist of Geneva ought to have been a <i>Plutonist</i>, -in order to give consistency to the principles which he had adopted, -and to make them coalesce as parts of one and the same system. If he -embraced an opposite opinion, it probably was from feeling the force of -those objections that arise from our discovering nothing in the bowels -of the earth like the remains left by combustion, or inflammation, at -its surface. The secret by which these seeming contradictions are to be -reconciled, was unknown to this mineralogist, and he has accordingly -decided strongly against the action of fire, even in the case of those -unstratified substances that have the greatest affinity to volcanic -lava.</p> - -<p><span class="pagenum" id="Page_519">- 519 -</span></p> - -<p>454. The theoretical conclusions of another accurate and skilful -observer, Dolomieu, furnish a still more remarkable example of a -tendency to union between systems professedly hostile to one another.</p> - -<p>This ingenious mineralogist, observing the interposition of the basalt -between stratified rocks, so that it had not only regular beds of -sandstone for its base, but was also covered with beds of the same -kind, saw plainly that these appearances were inconsistent with the -supposition of common volcanic explosions at the surface. He therefore -conceived, that the volcanic eruption had happened at the bottom of -the sea, (the level of which, in former ages, had been much higher -than at present,) and that the materials afterwards deposited on the -lava, had been in length of time consolidated into beds of stone. It -is evident, that this notion of submarine volcanoes, comes very near, -in many respects, to Dr Hutton's explanation of the same appearances. -If the only thing to be accounted for were the phenomenon in question, -it cannot be denied that Dolomieu's hypothesis would be perfectly -sufficient; but Dr Hutton, to whom this phenomenon was familiar, and -who, like Dolomieu, conceived the basalt to have been in fusion, was -convinced that the retreat of the sea was not a fact well attested by -geological appearances, and -<span class="pagenum" id="Page_520">- 520 -</span> if admitted, was inadequate to account for -the facts usually explained by it. He conceived, therefore, that such -lava as the preceding had flowed not only at the bottom of the sea, -but in the bowels of the earth, and having been forced up through the -fissures of rocks already formed, had heaved up some of these rocks, -and interposed itself between them. This agrees with the other facts in -the natural history both of the basaltes and the strata.</p> - -<p>It is plain, that, in this, there is a great approach of the two -theories to one another: both maintain the igneous origin of basaltes, -and its affinity to lava; both acknowledge that this lava cannot have -flowed at the surface, and that the strata which cover it have been -formed at the bottom of the sea. They only differ as to the mode in -which the submarine or subterraneous volcano produced its effect, and -that difference arises merely from the one geologist having generalized -more than the other. Dolomieu sought to connect the basalt with the -lavas that proceed from volcanic explosions at the surface; Dr Hutton -sought not only to connect these two appearances with one another, but -also with the other phenomena of mineralogy, particularly with the -veins of basaltes, and the elevation of the strata.</p> - -<p><span class="pagenum" id="Page_521">- 521 -</span></p> - -<p>455. In another point, the coincidence of Dolomieu's opinions and Dr -Hutton's is still more striking. The former has remarked, that many -of the extinguished volcanoes are in granite countries, and that, -nevertheless, the lavas that they have erupted contain no granitic -stones. There must be, therefore, says he, something under the granite, -and this last is not, at least in all cases, to be considered as the -basis of the mineral kingdom, or as the body on which all others rest. -In this system, therefore, granite is not always a primordial rock, any -more than in Dr Hutton's.</p> - -<p>But Dolomieu makes a still nearer advance to the Huttonian theory; for -he supposes, that under the solid and hard crust of the globe, there is -a sphere of melted stone, from which this basaltic lava was thrown up. -The system of subterraneous heat is here adopted in its utmost extent, -and in that form which is considered as the most liable to objection, -viz. the existence of it at the present moment, in such a degree as to -melt rocks, and keep them in a state of fusion. In this conclusion, the -two theories agree perfectly; and if they do so, it is only because -the nature of things has forced them into union, notwithstanding the -dissimilitude of their fundamental principles.</p> - -<p><span class="pagenum" id="Page_522">- 522 -</span></p> - -<p>This ought to be considered as a strong proof, that the phenomena -known to mineralogists are sufficient to justify the attempts to form -a theory of the earth, and are such as lead to the same conclusions, -where there was not only no previous concert, but even a very marked -opposition. I have already observed, that there is a greater tendency -to agree among geological theories, than among the authors of those -theories.</p> - -<p>456. Another circumstance worthy of consideration is, that in the -search which the Neptunists have made, for facts most favourable to the -aqueous formation of minerals, we find hardly any of a kind that was -unknown to the author of the system here explained. The appearances on -which <span class="smcap">Werner</span> grounds his opinion with respect to basaltes, -and by which he would exclude the action of fire from any share in the -formation of it, are all comprehended in the alternation of that rock -with beds, or strata obviously of aqueous origin. Now these appearances -were well known to Dr Hutton, and are easily explained by his theory, -provided the effects of compression are admitted. From this, and the -other circumstances just observed, I am disposed to think, that the -great facts on which every geological system must depend, are now -known, and that it is not too bold an anticipation to say, that a -theory of the earth, which -<span class="pagenum" id="Page_523">- 523 -</span> explains all the phenomena with which we -are at present acquainted, will be found to explain all those that -remain to be discovered.</p> - -<p>457. The time indeed was, and we are not yet far removed from it, -when one of the most important principles involved in Dr Hutton's -theory was not only unknown, but could not be discovered. This was -before the causticity produced in limestone by exposure to fire was -understood, and when it was not known that it arose from the expulsion -of a certain aerial fluid, which before was a component part of the -stone. It could not then be perceived, that this aerial part might be -retained by pressure, even in spite of the action of fire, and that in -a region where great compression existed, the absence of causticity -was no proof that great heat had not been applied. The discoveries of -Dr <span class="smcap">Black</span>, therefore, mark an era, before which men were not -qualified to judge of the nature of the powers that had acted in the -consolidation of mineral substances. Those discoveries were, indeed, -destined to produce a memorable change in chemistry, and in all the -branches of knowledge allied to it; and have been the foundation of -that brilliant progress, by which a collection of practical rules, and -of insulated facts, has in a few years risen to the rank of a very -perfect science. But even before they had explained the nature of -carbonic -<span class="pagenum" id="Page_524">- 524 -</span> gas, and its affinity to calcareous earth, I am not sure but -that Dr Hutton's theory was, at least, partly formed, though it must -certainly have remained, even in his own opinion, exposed to great -difficulties. His active and penetrating genius soon perceived, in the -experiments of his friend, the solution of those difficulties, and -formed that happy combination of principles, which has enabled him to -explain the most enigmatical appearances in the natural history of the -earth.</p> - -<p>As we are not yet far removed from the time when our chemical knowledge -was too imperfect to admit of a satisfactory explanation of the -phenomena of mineralogy, so it is not unlikely that we are approaching -to other discoveries that are to throw new light on this science. It -would, however, be to argue strangely to say, that we must wait till -those discoveries are made before we begin any theoretical reasonings. -If this rule were followed, we should not know where the imperfections -of our science lay, nor when the remedies were found out, should we -be in a condition to avail ourselves of them. Such conduct would not -be caution, but timidity, and an excess of prudence fatal to all -philosophical inquiry.</p> - -<p>458. The truth, indeed, is, that in physical inquiries, the work of -theory and observation must -<span class="pagenum" id="Page_525">- 525 -</span> go hand in hand, and ought to be carried -on at the same time, more especially if the matter is very complicated, -for there the clue of theory is necessary to direct the observer. -Though a man may begin to observe without any hypothesis, he cannot -continue long without seeing some general conclusion arise; and to -this nascent theory it is his business to attend, because, by seeking -either to verify or to disprove it, he is led to new experiments, -or new observations. He is led also to the very experiments and -observations that are of the greatest importance, namely, to those -<i>instantiæ crucis</i>, which are the <i>criteria</i> that naturally -present themselves for the trial of every hypothesis. He is conducted -to the places where the transitions of nature are most perceptible, -and where the absence of former, or the presence of new circumstances, -excludes the action of imaginary causes. By this correction of his -first opinion, a new approximation is made to the truth; and by the -repetition of the same process, certainty is finally obtained. Thus -theory and observation mutually assist one another; and the spirit -of system, against which there are so many and such just complaints, -appears, nevertheless, as the animating principle of inductive -investigation. The business of sound philosophy is not to extinguish -this spirit, but to restrain and direct its efforts.</p> - -<p><span class="pagenum" id="Page_526">- 526 -</span></p> - -<p>459. It is therefore hurtful to the progress of physical science to -represent observation and theory as standing opposed to one another. -Bergman has said, "Observationes veras quàm ingeniosissimas fictiones -sequi præstat; naturæ mysteria potius indagare quàm divinare."</p> - -<p>If it is meant by this merely to say, that it is better to have facts -without theory, than theory without facts, and that it is wiser to -inquire into the secrets of nature, than to guess at them, the truth -of the maxim will hardly be controverted. But if we are to understand -by it, as some may perhaps have done, that all theory is mere fiction, -and that the only alternative a philosopher has, is to devote himself -to the study of facts unconnected by theory, or of theory unsupported -by facts, the maxim is as far from the truth, as I am convinced it is -from the real sense of Bergman. Such an opposition between the business -of the theorist and the observer, can only occur when the speculations -of the former are vague and indistinct, and cannot be so embodied as to -become visible to the latter. But the philosopher who has ascended to -his theory by a regular generalization of facts, and who descends from -it again by drawing such palpable conclusions as may be compared with -experience, furnishes the infallible means of distinguishing between -<i>perfect science</i> and <i>ingenious fiction</i>. Of a geological -theory -<span class="pagenum" id="Page_527">- 527 -</span> that has stood this double test of the analytic and synthetic -methods, Dr Hutton has furnished us with an excellent instance, in his -explanation of granite. The appearances which he observed in that stone -led him to conclude, that it had been melted, and injected while fluid, -among the stratified rocks already formed. He then considered, that if -this is true, veins of granite must often run from the larger masses of -that stone, and penetrate the strata in various directions; and this -must be visible at those places where these different kinds of rock -come into contact with one another. This led him to search in Arran and -Glentilt for the phenomena in question; the result, as we have seen, -afforded to his theory the fullest confirmation, and to himself the -high satisfaction which must ever accompany the success of candid and -judicious inquiry.</p> - -<p>460. It cannot, however, be denied, that the impartiality of an -observer may often be affected by system; but this is a misfortune -against which the want of theory is not always a complete security. -The partialities in favour of opinions are not more dangerous than -the prejudices against them; for such is the spirit of system, and so -naturally do all men's notions tend to reduce themselves into some -regular form, that the very belief that there can be no theory, becomes -a theory itself, and may have no inconsiderable -<span class="pagenum" id="Page_528">- 528 -</span> sway over the mind -of an observer. Besides, one man may have as much delight in pulling -down, as another has in building up, and may choose to display his -dexterity in the one occupation as well as in the other. The want -of theory, then, does not secure the candour of an observer, and it -may very much diminish his skill. The discipline that seems best -calculated to promote both, is a thorough knowledge of the methods of -inductive investigation; an acquaintance with the history of physical -discovery; and the careful study of those sciences in which the rules -of philosophising have been most successfully applied.</p> - - -<p class="caption3nb gesperrt">FINIS.</p> - - -<hr class="chap" /> - -<hr class="tb" /> - - -<div class="transnote"> - -<p class="caption3nb">Transcriber Note</p> - -<p>Minor typos corrected. 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