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diff --git a/43320.txt b/43320.txt deleted file mode 100644 index 4eac5cb..0000000 --- a/43320.txt +++ /dev/null @@ -1,11448 +0,0 @@ -The Project Gutenberg EBook of The Wonder Book of Volcanoes and Earthquakes, by -Edwin J. Houston - -This eBook is for the use of anyone anywhere 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 - - -Title: The Wonder Book of Volcanoes and Earthquakes - -Author: Edwin J. Houston - -Release Date: July 27, 2013 [EBook #43320] - -Language: English - -Character set encoding: ASCII - -*** START OF THIS PROJECT GUTENBERG EBOOK THE WONDER BOOK OF VOLCANOES *** - - - - -Produced by Chris Curnow, Diane Monico, and the Online -Distributed Proofreading Team at http://www.pgdp.net (This -file was produced from images generously made available -by The Internet Archive) - - - - - - - - - - - -THE WONDER BOOK OF - -VOLCANOES AND EARTHQUAKES - -[Illustration: MOUNT VESUVIUS IN ERUPTION] - - - - -THE -WONDER BOOK -OF -VOLCANOES AND EARTHQUAKES - -BY -Professor EDWIN J. HOUSTON, Ph.D. - -NEW YORK -FREDERICK A. STOKES COMPANY -Publishers - - - - -Copyright, 1907, by -FREDERICK A. STOKES COMPANY - -_All rights reserved_ - -_October, 1907_ - - - - -ACKNOWLEDGMENTS - - -We take this opportunity of acknowledging the courtesy of the -following publishers, who have helped us in connection with the -illustrations of this book:-- - -Henry Holt and Company ("Physiography," by Rollin D. Salisbury). - -D. Appleton and Company (Figs. 13, 35, 39, 40, 41, 42, 43, 44, 45 and -46, "Volcanoes: What They Are and What They Teach," by J. W. Judd; -Fig. 15, "Principles of Geology," by Sir C. Lyell). - -The American Book Company ("Manual of Geology," by James Dwight Dana). - -G. P. Putnam's Sons ("Earthquakes in the Light of the New Seismology," -by C. E. Dutton). - -The Clarendon Press ("Geology: Chemical, Physical, and -Stratigraphical," by Joseph Prestwich). - - THE PUBLISHERS. - - - - -CONTENTS - - -CHAPTER PAGE - -I. THE VOLCANIC ERUPTION OF KRAKATOA IN 1883 1 - -II. SOME EFFECTS OF THE ERUPTION OF KRAKATOA 12 - -III. THE VOLCANIC ISLAND OF HAWAII 26 - -IV. THE VOLCANIC ISLAND OF ICELAND 46 - -V. VESUVIUS 58 - -VI. OTHER VOLCANOES OF THE MEDITERRANEAN 73 - -VII. ORIZABA, POPOCATEPETL, IXTACCIHUATL, AND - OTHER VOLCANOES OF MEXICO 85 - -VIII. COSEGUINA AND OTHER VOLCANOES OF CENTRAL AMERICA 91 - -IX. THE VOLCANIC MOUNTAINS OF SOUTH AMERICA 97 - -X. VOLCANOES OF THE UNITED STATES 105 - -XI. THE CATASTROPHE OF MARTINIQUE AND THE VOLCANIC - ISLANDS OF THE LESSER ANTILLES 117 - -XII. SOME OTHER NOTED VOLCANIC MOUNTAINS 125 - -XIII. JORULLO, A YOUNG VOLCANIC MOUNTAIN 130 - -XIV. MID-OCEAN VOLCANIC ISLANDS 137 - -XV. SUBMARINE VOLCANOES 141 - -XVI. DISTRIBUTION OF THE EARTH'S VOLCANOES 148 - -XVII. VOLCANOES OF THE GEOLOGICAL PAST 153 - -XVIII. LAPLACE'S NEBULAR HYPOTHESIS 157 - -XIX. THE EARTH'S HEATED INTERIOR, THE CAUSE OF VOLCANOES 165 - -XX. SOME FORMS OF LAVA 178 - -XXI. MUD VOLCANOES AND HOT SPRINGS 193 - -XXII. THE VOLCANOES OF THE MOON 207 - -XXIII. EARTHQUAKES 219 - -XXIV. SOME OF THE PHENOMENA OF EARTHQUAKES 231 - -XXV. THE EARTHQUAKE OF CALABRIA IN 1783 245 - -XXVI. THE GREAT LISBON EARTHQUAKE OF 1755 252 - -XXVII. THE EARTHQUAKE OF CUTCH, INDIA, IN 1819 257 - -XXVIII. THE SAN FRANCISCO EARTHQUAKE OF APRIL 18, 1906 262 - -XXIX. SOME OTHER NOTABLE EARTHQUAKES 269 - -XXX. SODOM AND GOMORRAH AND THE CITIES OF THE PLAIN 281 - -XXXI. INSTRUMENTS FOR RECORDING AND MEASURING EARTHQUAKE - SHOCKS 290 - -XXXII. SEAQUAKES 296 - -XXXIII. THE DISTRIBUTION OF EARTHQUAKES 303 - -XXXIV. THE CAUSES OF EARTHQUAKES 308 - -XXXV. EARTHQUAKES OF THE GEOLOGICAL PAST--CATACLYSMS 319 - -XXXVI. THE KIMBERLY DIAMOND FIELDS AND THEIR VOLCANIC - ORIGIN 326 - -XXXVII. THE FABLED CONTINENT OF ATLANTIS 335 - -XXXVIII. PLATO'S ACCOUNT OF ATLANTIS 344 - -XXXIX. NATURE'S WARNING OF COMING EARTHQUAKES 364 - - - - -FULL PAGE ILLUSTRATIONS - - - PAGE - -MT. VESUVIUS IN ERUPTION Frontispiece - -STONES AND LAVA THROWN UPWARDS--ERUPTION OF - MOKUAWEOWEO, HAWAII, JULY 4-21, 1899 fac. 36 - -COTOPAXI 102 - -THE LAVA FLOW OF THE CRATER OF KILAUEA, HAWAIIAN ISLANDS 184 - -A SAN FRANCISCO PAVEMENT TORN BY THE EARTHQUAKE 266 - - - - -ILLUSTRATIONS IN TEXT - - -FIG. PAGE - -1. THE SUNDA ISLANDS 3 - -2. KRAKATOA BEFORE THE ERUPTION 4 - -3. KRAKATOA AFTER THE ERUPTION 4 - -4. VOLCANIC DUST AS IT APPEARS UNDER THE MICROSCOPE 19 - -5. THE HAWAIIAN ISLANDS 27 - -6. HAWAII 29 - -7. PANORAMA OF MOKUAWEOWEO 35 - -8. VIEW OF THE CRATER OF KILAUEA FROM THE VOLCANO HOUSE 35 - -9. CRATER OF KILAUEA 40 - -10. SECTIONS OF KILAUEA AT DIFFERENT PERIODS 42 - -11. ICELAND 47 - -12. THE MEDITERRANEAN 59 - -13. THE VOLCANIC DISTRICT AROUND VESUVIUS 60 - -14. MT. ETNA 77 - -15. STROMBOLI, VIEWED FROM THE NORTHWEST, APRIL, 1874 79 - -16. MEXICO AND CENTRAL AMERICA 86 - -17. SOUTH AMERICA 98 - -18. THE UNITED STATES 106 - -19. PANORAMA FROM THE MESA AT THE EDGE OF MT. TAYLOR 110 - -20. VOLCANIC NECKS, EDGE OF MESA AT MT. TAYLOR 111 - -21. THE LESSER ANTILLES 118 - -22. GRAHAM'S ISLAND--A RECENT VOLCANIC ISLAND 143 - -23. ALEUTIAN ISLANDS 146 - -24. MAP OF THE WORLD, SHOWING LOCATION OF ACTIVE AND - RECENTLY EXTINCT VOLCANOES 150 - -25. VOLCANIC VESICLES 183 - -26. THREAD-LACE SCORIAE FROM KILAUEA 185 - -27. THREAD-LACE SCORIAE FROM KILAUEA 185 - -28. FROST-LIKE LAVA CRYSTALS 187 - -29. FROST-LIKE LAVA CRYSTALS 187 - -30. BASALTIC COLUMNS, ISLE OF CYCLOPS, ITALY 188 - -31. COLUMNAR AND NON-COLUMNAR BASALT 189 - -32, 33. DRIBLET CONES 190 - -34. LAVA STALACTITES 191 - -35. CRATER OF THE GREAT GEYSER OF ICELAND 202 - -36. GIANT GEYSER 203 - -37. BEE HIVE 203 - -38. BEE HIVE GEYSER OF ICELAND 205 - -39. HEAVY STONE OBELISKS TWISTED BY CALABRIAN EARTHQUAKE - OF 1783 229 - -40. CIRCULAR HOLLOW FORMED BY CALABRIAN EARTHQUAKE 239 - -41. SECTION OF CIRCULAR HOLLOW FORMED BY CALABRIAN - EARTHQUAKE 239 - -42. MAP OF THE CALABRIAN EARTHQUAKE OF 1783 246 - -43. FISSURES CAUSED BY THE CALABRIAN EARTHQUAKE 249 - -44. MAP SHOWING DISTRICT VISITED BY THE EARTHQUAKE OF - CUTCH OF 1819 258 - -45. SINDREE BEFORE THE EARTHQUAKE OF 1819 259 - -46. SINDREE AFTER THE EARTHQUAKE OF 1819 260 - -47. MAP OF WESTERN COAST OF CALIFORNIA SHOWING POSITION - OF SAN FRANCISCO 263 - -48. NEW ZEALAND 274 - -49. MAP SHOWING REGION AFFECTED BY THE CHARLESTON - EARTHQUAKE OF 1886 277 - -50. SYRIA 282 - -51. COMPLEX RECORD OF SEISMOGRAPH 293 - -52. LONG DISTANCE SEISMOGRAM 293 - -53. VICENTINI VERTICAL PENDULUM 294 - -54. VICENTINI PENDULUM AND RECORDER 295 - -55. DAVISON'S EARTHQUAKE MAP OF JAPAN 306 - - - - -THE WONDER BOOK OF - -VOLCANOES AND EARTHQUAKES - - - - -THE WONDER BOOK OF VOLCANOES - -AND EARTHQUAKES - - - - -CHAPTER I - -THE VOLCANIC ERUPTION OF KRAKATOA IN 1883 - - -Krakatoa is a little island in the Straits of Sunda, about thirty -miles west of the island of Java, and nearly the same distance east -of the island of Sumatra. It is uninhabited and very small, measuring -about five miles in length and less than three miles in width. Its -total area is only thirteen square miles. This little piece of land -made itself famous by what took place on it during the month of -August, 1883. - -Krakatoa is one of the many islands that form the large island chain -known as the Sunda Islands. The most important islands of this chain -are Sumatra, Java, Sumbawa, Flores, and Ceram. Between Sumatra and -Java, the largest two of these islands, there is a channel called the -Straits of Sunda that connects the waters of the Indian Ocean with -those of the Pacific Ocean. The Straits of Sunda is an important piece -of water that forms one of the great highways to the East. Shipping -is, therefore, always to be found in its waters. - -As can be seen by the map, Krakatoa is not far from the Equator, -being situated in lat. 6 deg. 7' S. and long. 105 deg. 26' E. from Greenwich. -Since there are about sixty-nine miles in every degree of latitude, -Krakatoa is about 420 miles south of the Equator, and is about -twenty-five miles from Java. Java is part of the Dutch East Indies, -which includes Java, Celebes, the Spice Islands, and parts of Borneo -and Sumatra. Batavia, the principal seaport of Java, near the -northwest coast, is a great shipping centre, visited by vessels from -nearly all parts of the world. It has, however, no harbor, but is -approached from the ocean by means of a canal two miles in length, the -sides of which are provided with massive brick walls. Besides Batavia, -which is situated about one hundred English miles east of Krakatoa, -there are many smaller towns or villages, the most important of which -is Anjer, a thriving seaport town, where sailing vessels obtain their -supplies of food and fresh water. Before the eruption of Krakatoa, -Anjer was provided with a strong, stone lighthouse. - -Java is especially noted for its production of coffee, in which it is -second only to Brazil. Its area is about the same as that of the State -of New York. Java is one of the most densely populated parts of the -world, containing nearly four times as many people as the whole State -of New York. - -These facts about the situation and surroundings of Krakatoa are -necessary to an understanding of the wonderful thing that happened on -it during the month of August, 1883. In that month Krakatoa suffered a -most tremendous explosive volcanic eruption, for it is a volcano. - -[Illustration: FIG. 1. THE SUNDA ISLANDS] - -A volcano is a mountain or hill, generally conical in shape, having -at the top a nearly central opening, called a _crater_, from which -at times melted rock and lava, vapor and gases escape. The lava -either flows down the side of the mountain in a liquid condition, or -is thrown upwards into the air. If the distance the lava is thrown -upwards is sufficiently great the melted matter solidifies before it -falls to the earth. In such cases the largest fragments form what are -called _volcanic cinders_, the smaller pieces, _volcanic ashes_, and -the extremely small particles, _volcanic dust_. If, however, the lava -is thrown to a comparatively small height, it is still melted when it -falls, and is then known as _volcanic drops_ or _driblets_. - -[Illustration: FIG. 2. KRAKATOA BEFORE THE ERUPTION] - -It is not surprising that Krakatoa is a volcanic island, since it lies -in one of the most active belts of volcanic islands in the world, and -near the coasts of the most active of these islands; i. e., Java. -This belt, as shown in the map, includes, besides the Sunda Island -chain, parts of Gilolo, Celebes, Mindanao and the Philippine Islands. -These islands lie between Asia on the northwest and Australia on the -southeast. - -[Illustration: FIG. 3. KRAKATOA AFTER THE ERUPTION] - -There is no other part of the world with, perhaps, the single -exception of Japan, where so many active volcanoes are crowded in -so small a space. The island of Java, small as it is, has nearly -fifty volcanoes, of which at least twenty-eight are active. They are -situated in a lofty range running from east to west, some of the -peaks of which are more than 10,000 feet above the level of the sea. -Volcanic eruptions are so frequent that the island is seldom free from -them. - -As will be seen from the map shown in Fig. 2, Krakatoa consists of -three groups of volcanic mountains, the southern group giving the name -of Krakatoa to the island. Strictly speaking, this mountain was called -_Rakata_, but as it is now generally known as Krakatoa, it would be -unwise to attempt to call it by any other name. The central mountain -or group of mountains is known as Danan, and consists largely of part -of an old crater. The group of mountains which lies near the northern -end of the island was known as Perboawatan. From the centre of this -latter group of mountains are several old lava streams consisting -of a variety of lava resembling a dark-colored glass, known to -mineralogists as _obsidian_, or _volcanic glass_. - -Although Krakatoa was always a volcano, yet between the years 1680 and -1883, it was in the condition of a sleeping or extinct volcano. There -had been a severe explosive eruption in the year 1680, that caused -great loss of life and property, but ever since that time all activity -had ceased and it seemed that the volcano would never again burst out. -In other words, it was generally regarded as a trustworthy, sedate, -quiet, inoffensive and perfectly safe volcano, that had become extinct. - -The long continued quiet of Krakatoa was broken on the 20th of May, -1883, when the inhabitants of Batavia on the island of Java were -terrified by noises like the firing of great guns, that were first -heard between ten and eleven o'clock in the morning. These noises -were accompanied by the shaking of the ground and buildings. The -sleeping volcano of Krakatoa was evidently growing restless, but no -great damage was done and soon all was again quiet. The disturbances -were merely the forerunner of the terrible eruption soon to follow, -and confidence was soon restored. But suddenly, on Sunday, August -26th, 1883, almost without any further warnings, Krakatoa burst into -terrible activity and began an explosive eruption that has never been -equalled in severity in the memory of man. - -That memorable Sunday of August 26th, 1883, came during a season of -the year known as the _dry monsoon_, a name given the season of the -periodical winds from the Indian Ocean. Batavia, and the surrounding -country, greatly needed rain, for in this part of the world it seldom -rains from April to October, although the air is very moist and damp. -For this reason the beginning of the wet season is always welcomed. -When, therefore, the rumbling sounds of the approaching catastrophe of -Krakatoa were heard in Batavia, the people, believing that the noises -were due to peals of thunder, rejoiced, for all thought they heralded -an earlier setting in of the wet monsoon. But when the rumbling -sounds increased and reports were heard like heavy artillery, it was -clear that the sounds were the beginning of a volcanic eruption, a -phenomenon with which they were only too well acquainted, but, as -volcanic eruptions were far from being uncommon in Java, no one was -very greatly frightened. - -But this time the noises increased to such an extent that the people -became alarmed. Throughout the night the appalling sounds continued -and were accompanied by shakings of the earth sufficiently strong to -shake the houses violently. Sleep was out of the question. Many of -the people left their houses and remained all night in the open air, -fearing the shocks would bring the houses down over their heads. - -The morning instead of heralding the dawn of a beautiful tropical day, -with its bright, cheerful sunlight, brought with it skies covered -with gray clouds that completely hid the sun. The rumbling sounds, -however, had decreased, and the people were beginning to congratulate -themselves that the dangers were over, when suddenly, the sky grew -darker, and there began a shower of ashes that soon covered the -streets and houses of the city. About seven o'clock on the morning of -August 27th, a most tremendous crash was heard. The sky rapidly became -so dark that it was soon necessary to light the lamps in the houses -of Batavia, and some of the neighboring towns in the western part of -Java. In addition to this the air was filled with vapor, while every -now and then earthquake shocks were again felt. These shocks were -accompanied by terrific noises like those produced by the explosion of -heavy artillery. The noises rapidly increased in number and intensity -until they produced a nearly continuous roar, the nature of which it -is almost impossible to describe since it is probable that such sounds -had never been heard before by man. It is a curious fact, which, I -believe, has never been satisfactorily explained, that in most cases -the people in the immediate neighborhood of the volcano, as, for -example, those on board vessels in the Straits of Sunda, did not hear -the terrific noises at all. Possibly they were too loud and simply -gave a single inward impetus to the drum of the ear and then held it -in position. - -Probably some of my readers may remember that witty description given -by Dr. Oliver Wendell Holmes of an alleged effort made by all the -people of the world to find out whether or not there is a man in the -moon. This wonderful plan was as follows: - -Careful calculations were made to ascertain when it would be the same -time over all the earth so that all the people of the earth could -simultaneously shout at the top of their voices. In this way it was -hoped that the man in the moon, if there were such a person, would -notice the noise. - -The story goes on to tell how when the time approached for the great -experiment, and all were ready to shout as loud as they could, that -each person reasoning to himself or herself, that amid so great a -noise no one could notice whether his or her voice was omitted, -determined to remain silent, so as to be able to hear the noise and -the better to observe what the man in the moon would do when the sound -reached him. The result was that every person on the earth remained -silent and simply listened, so that the earth was never so quiet -before. - -Had Oliver Wendell Holmes, or any other person conceiving the witty -idea, lived during the time of the great explosive eruption of -Krakatoa, on that memorable August 27th, 1883, he might have taken -the opportunity of observing the man in the moon, had he not been -frightened by what was occurring, for certainly never before were -such tremendous or terrifying sounds produced, for these sounds, as -we shall see shortly, were actually heard for distances of more than -3,000 miles from the volcano. - -There were two different kinds of waves produced in the air by the -tremendous forces at work in the eruption of Krakatoa; namely, -atmospheric waves and sound waves. - -The atmospheric waves showed their presence in the air by means of -changes produced in the atmospheric pressure. Now, while these -changes cannot readily be felt by man, yet their presence can be -easily shown by the use of instruments called _barometers_. - -There are in different parts of the world, buildings called -_meteorological observatories_, that are provided, among other -instruments, with recording barometers. These instruments caught -the great atmospheric waves that were produced by the eruption of -Krakatoa. In this manner, the astounding fact was learned that the -waves starting from the volcano travelled no less than seven times -around the world. When we say astounding, it must not be understood -that the formation of such waves was at all contrary to the known laws -of physics. On the contrary, provided the force of the eruption was -sufficiently great, such waves must have been produced in the great -aerial ocean. The astonishing, or wonderful thing, was that the force -setting up these waves was so great that it caused them to move seven -times around the globe. - -The atmospheric waves were so powerful that it will be worth our while -to describe them in detail. Starting from the volcano of Krakatoa, -as a centre, these waves moved outwards in all directions, becoming -gradually larger and larger until they reached a point halfway round -the globe, or 180 deg. from Krakatoa. The waves did not, however, stop -here, but continued moving onward, now growing smaller and smaller -until they reached a point in North America, immediately opposite -Krakatoa. Such a point on a globe is called an _antipodal point_.[1] -The waves did not stop at this point, but again advanced moving toward -Krakatoa, growing larger and larger until they again reached a point -halfway around the globe, or 180 deg. from Krakatoa, when they again -continued moving but now continually growing smaller and smaller, -until they reached Krakatoa. Here they again began moving completely -around the globe, and this was continued for as many as seven times. -It must not be supposed that the waves ceased on the seventh time -around. On the contrary, they, probably, kept on moving for many -additional times, but they were then so feeble that even the sensitive -recording barometers were unable to detect their presence. - -There was another kind of waves in the atmosphere that did not require -barometers for their detection. These were the sound waves, and can -readily be detected by the human ear. - -Now, in the case of the great eruption of Krakatoa, the intensity of -the sounds was so great that the sounds could be heard distinctly at -distances of several thousand miles from Krakatoa. - -The sound waves so closely resembled the explosion of artillery that -at Acheen, a port on the northern coast of Sumatra, 1,073 miles from -Krakatoa, the authorities, believing that an attack was being made on -the port, placed all their troops under arms to repel the invaders. -The sounds were also distinctly heard at Bangkok, in Siam, a distance -of 1,413 miles from the volcano. They were also heard at the Chagos -Islands, a group of islands situated in the Indian Ocean about 2,267 -miles from Krakatoa. - -Two steamers at Singapore, 522 miles distant, were despatched to find -the vessel that was believed to be firing guns as distress signals. - -The sounds were distinctly heard in parts of South Australia, 2,100 -miles distant, and in Western Australia, at 1,700 miles distance. - -But it will be unnecessary to give any further details of the great -distances at which these sounds were actually heard. It will suffice -to say that they were heard as far off as about 3,000 miles. - -It is difficult to picture to one's self such great distances. -Assuming the greatest distances to be in the neighborhood of 3,000 -miles, it would be as if a sound produced, say, in Boston, New York, -or Philadelphia, was so loud that it could be heard in Amsterdam, -London, or Paris. - -Some idea of the intensity of these sounds can be had from the fact -that in Batavia, when, in accordance with usage, a gun was fired from -one of the forts at eight o'clock in the morning, two hours before the -greatest intensity of the sounds had been reached, the sound of the -gun could scarcely be heard above the continuous roar. - -While, of course, the principal reason the sound waves were carried -so far was the great force causing the eruption, yet these distances -were increased by the fact that the explosion occurred in a region -almost entirely surrounded by great bodies of water. The waves could, -therefore, be readily carried along the surface of the sea. Had there -been a high mountain wall, like the Andes of South America, on one -side of the volcano they would probably have been shut off in this -direction a short distance from where they were produced. - - - - -CHAPTER II - -SOME EFFECTS OF THE ERUPTION OF KRAKATOA - - -Besides the sound waves in the air, there were waves in the waters of -the ocean. Suddenly, without any warning, the people of Batavia were -surprised by a huge wave that, crossing the Straits of Sunda, entered -the ship canal before referred to as connecting the city with the -ocean, and, rising above the brick wall, poured over the surrounding -country. - -Although Batavia was 100 English miles from Krakatoa, yet after -travelling this distance the wave was sufficiently strong to enter -the city and flood its streets with water to a depth of several feet. -Fortunately, the loss of life was small in the city of Batavia, but -very great in the surrounding towns and villages. - -The ocean waves varied in height at different times of the eruption. -The greatest were from fifty to eighty feet high. Just imagine the -effect of a wave twice the height of an ordinary house. The waves -caused great damage to the shipping in the neighborhood. In one -instance, a vessel was carried one and a half miles inland and left on -dry land thirty feet above the level of the sea. - -The total loss of life by the waves has been estimated at 35,000 -people; besides this, of course, there was a great amount of property -destroyed. The greatest loss was in the immediate neighborhood of -Krakatoa. Gigantic waves swept over the lowlands lying near the -shores of Sumatra and Java, where over areas several miles in width -nearly everything was destroyed, the houses, trees, and people being -swept away and the surface of the land greatly changed. The towns of -Karang and Anjer, as well as numerous smaller villages, were almost -completely destroyed. - -The seaport town of Anjer, by far the most important of the above -towns, was almost completely swept away. The heavy stone lighthouse -was so completely obliterated that no traces of its heavy stone -foundations could afterwards be found. The Rev. Phillip Neale, -formerly a British chaplain at Batavia, from whose account of the -eruption of Krakatoa some of the above facts have been taken, tells -of the brave action of the keeper of the lighthouse at Anjer. Besides -his work as lighthouse keeper, to see that the light was constantly -burning during the night, he was charged with telegraphing to Batavia -the names of all passing vessels. On the fateful morning of the great -catastrophe, observing that the sun did not rise, he kept the light of -the lighthouse burning, and, notwithstanding the danger to which he -was exposed, continued at his post in order to send word to Batavia of -the passing of an English steamer. While doing this the lighthouse was -swept away and the brave man perished. - -The following verbal account of the destruction of the port of Anjer -was given by a Dutch pilot stationed at Anjer. This description is -quoted by the Rev. Mr. Neale from an article prepared by him for -publication in "The Leisure Hour." - - "I have lived in Anjer all my life, and little thought the - old town would have been destroyed in the way it has. I am - getting on in years, and quite expected to have laid my - bones in the little cemetery near the shore, but not even - that has escaped and some of the bodies have actually been - washed out of their graves and carried out to sea. The - whole town has been swept away, and I have lost everything - except my life. The wonder is that I escaped at all. I can - never be too thankful for such a miraculous escape as I had. - - "The eruption began on the Sunday afternoon. We did - not take much notice at first, until the reports grew - very loud. Then we noticed that Krakatoa was completely - enveloped in smoke. Afterwards came on the thick darkness, - so black and intense that I could not see my hand before - my eyes. It was about this time that a message came - from Batavia inquiring as to explosive shocks, and the - last telegram sent off from us was telling you about - the darkness and smoke. Towards night everything became - worse. The reports became deafening, the natives cowered - down panic-stricken, and a red, fiery glare was visible - in the sky above the burning mountain. Although Krakatoa - was twenty-five miles away, the concussion and vibration - from the constantly repeated shocks were most terrifying. - Many of the houses shook so much that we feared every - minute would bring them down. There was little sleep for - any of us that dreadful night. Before daybreak on Monday, - on going out of doors, I found the shower of ashes had - commenced, and this gradually increased in force until at - length large pieces of pumice stone kept falling around. - About six A. M. I was walking along the beach. - There was no sign of the sun, as usual, and the sky had a - dull, depressing look. Some of the darkness of the previous - day had cleared off, but it was not very light even then. - Looking out to sea I noticed a dark, black object through - the gloom, travelling towards the shore. - - "At first sight it seemed like a low range of hills rising - out of the water, but I knew there was nothing of the kind - in that part of the Sunda Strait. A second glance--and a - very hurried one it was--convinced me that it was a lofty - ridge of water many feet high, and worse still, that it - would soon break upon the coast near the town. There was - no time to give any warning, and so I turned and ran for - my life. My running days have long gone by, but you may - be sure that I did my best. In a few minutes I heard the - water with a loud roar break upon the shore. Everything - was engulfed. Another glance around showed the houses - being swept away and the trees thrown down on every side. - Breathless and exhausted I still pressed on. As I heard - the rushing waters behind me, I knew that it was a race - for life. Struggling on, a few yards more brought me to - some rising ground, and here the torrent of water overtook - me. I gave up all for lost, as I saw with dismay how high - the wave still was. I was soon taken off my feet and borne - inland by the force of the resistless mass. I remember - nothing more until a violent blow aroused me. Some hard, - firm substance seemed within my reach, and clutching it, - I found I had gained a place of safety. The waters swept - past, and I found myself clinging to a cocoanut palm-tree. - Most of the trees near the town were uprooted and thrown - down for miles, but this one fortunately had escaped and - myself with it. - - "The huge wave rolled on, gradually decreasing in height - and strength until the mountain slopes at the back of - Anjer were reached, and then, its fury spent, the water - gradually receded and flowed back into the sea. The sight - of those receding waters haunts me still. As I clung to - the palm-tree, wet and exhausted, there floated past the - dead bodies of many a friend and neighbor. Only a mere - handful of the population escaped. Houses and streets were - completely destroyed, and scarcely a trace remains of where - the once busy, thriving town originally stood. Unless you - go yourself to see the ruin you will never believe how - completely the place has been swept away. Dead bodies, - fallen trees, wrecked houses, an immense muddy morass and - great pools of water, are all that is left of the town - where my life has been spent. My home and all my belongings - of course perished--even the clothes I am wearing are - borrowed--but I am thankful enough to have escaped with my - life and to be none the worse for all that I have passed - through." - -As is common in cases of earthquake waves a great depression in the -level of the sea occurred at places great distances from Krakatoa. For -example, at the harbor of Ceylon, the water receded so far that for -about three minutes the boats were left high and dry, and then a huge -wave carried them with it as it rushed over the land. - -Perhaps one of the best evidences of the immense power of ocean waves -is to be seen in the massive blocks of white coral rock that were -washed up by the waves, on parts of the coast of Java for distances of -from two to three miles from the ocean. Many of these blocks weighed -from twenty to thirty tons. Indeed, some of them reached the weight of -from forty to fifty tons. - -It is probable that the island of Krakatoa and its neighboring smaller -islands formed portions of a huge cone about eight miles in diameter, -that has been broken up at some very remote but unknown time by, -perhaps, a greater catastrophe than that of August, 1883. - -In the Straits of Sunda the water was raised fifty feet to eighty -feet above the ordinary level, and produced tremendous destruction -especially on the coasts of Java and Sumatra, sweeping away many -villages and drowning many thousands of people. The wave had a -velocity of progression of nearly 400 miles per hour, or eight times -faster than an ordinary express train. - -When it is said that the _velocity of progression of the wave_ was -nearly 400 miles per hour, it is not meant that a body floating on -the ocean, such, for example, as a ship, would have been carried -forward at this high velocity, but would merely rise and fall in a -to-and-fro swing to about the height of the wave; that is, fifty to -eighty feet according to what may have been the height. As in the -case of the sound waves these motions of water covered or passed over -nearly all the waters of the earth. The waves progressing toward the -west, crossed the Indian Ocean reaching to the coast of Hindostan, and -Madagascar, and sweeping around the southern part of Africa, finally -reached the coasts of France and England, as well as the eastern part -of North and South America. Sweeping towards the east, they reached -the coasts of Australia, New Zealand, and crossing the vast Pacific -Ocean were felt at Alaska and the western coasts of North and South -America. - -But besides the enormous waves caused by the eruption, there were -marked changes in the level of the land. Large portions of the coast -of Sumatra and Java were almost annihilated, much of the original -surface near the coast being submerged, and places that were formerly -dry land are now covered with water to a depth of from 600 to 900 feet. - -The enormous amount of material thrown into the air by the forces -of the eruption is especially characteristic of this phenomenon. -Such quantities of pumice stone and ashes fell from the clouds that, -sinking in the water and collecting on the bed of the channel, they -changed the depth of the water, so as to render navigation dangerous. -Indeed, the Sebesi Channel, lying on the north of the island of -Krakatoa was completely blocked by a huge bank of volcanic material, -portions of which projected above the water, forming two smaller -islands. These, however, have since been washed away by the waves. - -We will not attempt to give at present any explanations as to the -causes of this great volcanic eruption, since the different theories -as to the cause of volcanoes will be better understood when other -volcanic eruptions have been described. It is sufficient here to say -that if a large quantity of water should have suddenly reached a -great mass of molten rock, frightful explosive eruptions would have -occurred, and if the island was resting on a submerged crater its -sudden disappearance may be explained. - -Another great wonder connected with the explosive eruption of Krakatoa -was the enormous heights to which the fine dust was thrown up into -the air. It has been asserted that during the most intense of these -eruptions the particles reached elevations of perhaps more than -twenty-five miles above the level of the sea. Carried by the winds, -the fine particles remained suspended in the air for many months, -and gave rise to magnificent sunlight effects, such as early dawn, -lengthened twilights, lurid skies, and gorgeous sunsets of a reddish -tint. There were also caused curious haloes, as well as green and blue -moons. - -The fine dust particles consisted of minute crystals of feldspar and -other minerals, and when examined under the microscope presented the -appearance shown in Fig. 4. - -These mineral substances permitted a portion of the light to pass -through them, thus producing wonderful optical effects in the -atmosphere either because they acted like minute prisms and so -produced rainbow colors, or because they turned the rays of light out -of their course as to produce what is called interference by color -effects of a nature similar to the colors seen in mother-of-pearl, -rainbow coal, or in the wing cases of many beetles. The explanations -of these phenomena are too difficult for a book of this character. - -An explosive volcanic eruption is a very terrifying and wonderful -phenomenon. Frightful roaring sounds are suddenly heard, the earth -shakes for many miles around, when suddenly a vast quantity of molten -rock, and sometimes huge stones, are thrown out of the crater high up -into the air. So great is the force that throws these materials out -of the opening that heavy masses of rocks often are ejected very much -faster than the projectiles from the largest guns that are used in any -of the navies of the world. - -[Illustration: FIG. 4. VOLCANIC DUST AS IT APPEARS UNDER THE -MICROSCOPE] - -As the molten lava cools and falls in the form of prodigious clouds -of ashes, cinders and dust, for many miles around the volcano, even -the light of the sun is obscured, and one cannot see the hand before -the face. Some of the materials in these clouds are so light that they -remain suspended in the air for many hours, often indeed for many -days, and sometimes even for years. The heavier particles, however, -soon begin to fall, and before long the earth's surface both around -the volcano, and often at considerable distances from it, is covered -with a thick layer of ashes. - -The sounds accompanying a volcanic eruption are often terrifying. Amid -shakings and tremblings of the earth's crust, known as earthquakes, -there are occasionally heard noises like the explosion of huge guns. -Sometimes these sounds follow one another so rapidly that they produce -an almost continuous roar. Through the roar of the explosion a -curious crackling noise can be heard, due to the fragments of stone -hurled out of the crater striking against one another, especially as -the stones which are thrown out of the crater and have commenced to -fall back again to the earth, are struck by others that are still -rising. - -Immense quantities of ashes, stones, vapor and gases are thrown -upwards for great distances into the air, while, at the same time, a -lava stream pours over the lowest side of the crater. As the column -of ashes and cinders reaches its greatest height in the air, it -begins to spread outward on all sides, rapidly growing like a huge -dark mushroom. This soon shuts out the light of the sun, and from it -showers of red hot ashes and cinders fall to the earth. - -It would be extremely dangerous to be on the side of the volcanic -mountain during an explosive eruption; for, even should you escape -falling into an opening in the side of the mountain, you might be -killed by the huge stones that are constantly falling on all sides -around the opening, or might be buried under the vast showers of red -hot ashes that are poured down from the dense clouds overhanging the -mountain, or suffocated by clouds of sulphur vapor that rush down its -sides. - -When at a safe distance the sight is certainly magnificent. There is -no light from the sun. All would be in pitch darkness but for the -reddish glare thrown upwards by the red hot lava, by the glowing -showers of ashes that are being rained down on the sides of the -mountain, or by terrific lightning flashes, due to the discharge of -the immense quantities of electricity produced by the forces of the -eruption. - -Naturally a great volcanic eruption can cause a considerable loss of -life and property. When a large lava stream begins to flow down the -sides of the mountain, it cannot be stopped, and should it flow toward -a village or town it is likely to destroy the town completely. Besides -this, the vegetation of the country for many miles around is destroyed -by the showers of red hot ashes that fall from the sky. The houses of -neighboring cities are similarly ruined by the great conflagrations -thus set up. Further destruction is also caused by large streams of -mud that rush down the slopes of the mountain, or by huge waves set -up in the ocean. If the volcano is situated, as most volcanoes are, -near the coast, the showers of ashes and falling stones may set fire -to vessels in the neighborhood, or the progress of such vessels may be -seriously retarded by layers of ashes or pumice stone that float on -the surface. Sometimes these layers are so thick as actually to bring -ships to a complete standstill. - -It must not be supposed that volcanoes are in a constant state of -eruption. On the contrary, nearly all volcanoes, after an eruption, -become _quiet_ or _inactive_. The air soon clears by the ashes -settling, and the sunlight again appears. A crust forms over the -surface of the lava, which rapidly becomes hard enough to permit one -to walk over it safely. The vegetation, which has been destroyed by -the hot ashes, again springs up, and, if the volcano happens to be -situated within the tropics, where there is an abundance of moisture, -the land soon again becomes covered by a luxuriant vegetation. Most of -the people, who have escaped sudden death during the eruption, return -to the ruins of their houses; for it is a curious fact that no matter -how great has been a volcanic eruption, or how far-reaching the ruin, -the survivors, as a rule, do not appear to hesitate to return to their -old neighborhood. In a few years the fields are re-cultivated, the -villages are rebuilt, and the people apparently forget they are living -over a slumbering volcano, which may at any time again burst forth in -a dangerous eruption. - -A volcano that throws out molten rock, vapor and gases is known as an -_active volcano_. An active volcano, however, is only correctly said -to be in a state of eruption when the quantity of the molten rock, -lava or vapor it throws out is greatly in excess of the ordinary -amount. - -Sometimes the volcanic activity so greatly decreases that the molten -rock or lava no longer rises in the crater, but, on the contrary, -begins to sink, so that the top of the lava in the crater is often -at a considerable distance below its edges. The lava then begins to -harden on the surface, and, if the time is sufficient, the hardened -part extends for a considerable distance downward. In this way the -opening connecting the crater with the molten lava below becomes -gradually closed, the volcano being thus shut up, or corked, just as a -bottle is tightly closed by means of a cork driven into the opening at -its top so as to prevent the escape of the liquid it contains. - -It may sound queer to say that a volcano has its crater so corked up -as to prevent the escape of the lava, but the idea is nevertheless -correct and helpful. To realize the size of these huge volcanic corks -one must remember that the craters of some volcanoes are several miles -across. A volcano thus choked or corked up is said to be _extinct_. - -When we speak of an extinct volcano we do not mean that the volcano -will never again become active. A volcano does not cease to erupt -because there are no more molten materials in the earth to escape, but -simply because its cork or crust of hardened lava has been driven in -so tightly that the chances of its ever being loosened again seem to -be very small. But small as the chances may seem we must not forget -that the volcano may at any time become active, or go into its old -business of throwing out materials through its crater. A volcano in -an extinct condition is not unlike a steam boiler, the safety valve -of which has been firmly fixed in place. If the steam continues to be -generated in the boiler, it is only a matter of time when the boiler -will blow up, and the explosion will be all the greater because the -safety valve did not allow the steam to escape earlier. - -Sometimes an intermediate class of volcanoes called _dormant_ is -introduced between active volcanoes on the one hand and extinct -volcanoes on the other. The name dormant volcano, or, as the word -means, _sleeping volcano_, is objectionable, since it might lead one -to think that an extinct volcano is not sleeping but dead, and this is -wrong. - -Since the plug of hardened lava in the volcanic crater is generally at -a much lower level than the top of the crater, the crater will soon -become filled to a greater or less depth with water, produced either -by the rain, or by the melting of the snow that falls on the top of -the mountain. Crater lakes, often of very great depths, are common in -extinct volcanoes. - -Of course, when an extinct volcano again becomes active, two things -must happen if the eruption is explosive. In the first place, the -force of the explosion must be sufficiently great to loosen the -stopper or plug of hardened lava which stops it. In doing this the -mass is broken into a number of fragments that are thrown forcibly -upwards into the air. After rising often for great heights they soon -fall again on the sides of the mountain. - -But besides the breaking up of the stopper, the lake in the crater of -the volcano is thrown out along with the cinders or ashes, producing -very destructive flows of what are called aqueous lava or mud streams. -These streams flow down the sides of the mountain, carrying with them -immense quantities of both the ashes thrown out during the eruption, -or those that have collected around the sides of the crater during -previous eruptions. Very frequently, these streams of aqueous lava -produce greater destruction than the molten lava. - -If you have ever watched common ants at work clearing out or enlarging -their underground homes, in a piece of smooth gravel walk in your -garden, you can form some idea why the mountain immediately around a -volcanic crater is conical in shape. If the colony of ants happens -to be fairly large, you can see an almost unbroken stream of these -industrious little animals, each bearing in its mandibles a small -grain of sand or gravel brought up from some place below the surface. - -Carrying it a short distance from the opening, it throws it on the -ground, rapidly returning for another load. In this way there is -heaped up around all sides of the opening a pile of sand or gravel, -the outward slopes of which gives the pile a conical form. You have, -probably, noticed that the steepness of the slopes depends on the size -of the grains; for the larger these grains the sharper or steeper the -slopes, the very fine grains producing flat mounds or cones. - -It is the same with a volcanic cone. The materials that are thrown -upwards into the air, falling again on the mountain, collect around -the crater on all sides, thus giving it the characteristic cone-like -shape of the volcanic mountain. Where nothing occurs to disturb -the formation of the cone its height above the level of the sea -will gradually increase. Very frequently, however, during explosive -eruptions, a large part of this cone will be blown away by the -force of the eruption only to be again built up during some later -eruption. Indeed, in the case of volcanic islands, the force of a -great volcanic eruption is sometimes so great that not only is a large -volcanic mountain blown entirely away, but a hole is left, where it -had been standing, that extends further downwards below the level -of the sea than the top of the mountain extended previously above -it. The above are some, but by no means all, the wonders attending -volcanic eruptions. We shall refer to others in subsequent chapters in -describing particular eruptions. - - - - -CHAPTER III - -THE VOLCANIC ISLAND OF HAWAII - - -The volcanic island of Hawaii, the largest of the Sandwich Island -chain, is situated in the mid Pacific, south of the Tropic of -Cancer. As shown in Fig. 5, this island chain consists of Hawaii, -Maui, Molokai, Oahu, Kauai, Nihau, and about eight large islands, -together with numerous small islands, extending in a general northwest -direction from Hawaii to Nihau, a distance of about 400 miles. Like -most volcanic islands they lie in more or less straight lines, -probably along fissures, in this case in two nearly parallel lines. -The island of Nihau, however, is an exception, the direction of the -greatest length being almost straight across the two parallel lines. - -The Sandwich Islands lie 2,000 miles from San Francisco in deep water, -between 2,000 and 3,000 fathoms, or between 12,000 and 18,000 feet in -depth. This island chain consists of great volcanic mountains, that -had, at one time, fifteen active volcanoes of the first class. These -are now all extinct but three, and all of these are on the island of -Hawaii. - -In his report to the United States Geological Survey for 1882-83, -Dutton states that the summit of Mt. Haleakala on East Maui is 10,350 -feet above the sea level. Oahu has peaks on its eastern side 2,900 -feet high, and peaks on the western side 3,850 feet high. The summit -of Kauai is probably 6,200 feet above the sea. - -[Illustration: FIG. 5. THE HAWAIIAN ISLANDS _From U. S. -Geological Survey_] - -It can be shown by deep-sea soundings that all these volcanic piles -are the summits of a gigantic mountain mass that rises abruptly from -the bed of the Pacific. There are reasons for believing that this -submarine chain continues for many hundreds of miles in the same -direction beyond Kauai. - -The extinct volcano, Haleakala, on East Maui appears to have been in -eruption at a much later day than Mt. Kea, which is also an extinct -volcano. But the natives have no traditions of any eruptions. - -The volcanoes on the other islands have been extinct for a very long -time judging from the extent of their erosion. Dutton is of the -opinion that the western islands of the chain have been extinct for -much longer times than the remaining islands. - -The Sandwich Islands, also known as the Hawaiian Islands, are one of -the colonial possessions of the United States. The island of Hawaii is -about 2,000 miles from San Francisco. Honolulu, on the island of Oahu, -the principal seaport of the chain, has a pleasant climate, and is an -important coaling station for warships, commercial vessels, whalers, -and trading ships generally. - -The principal product of the island is sugar cane. - -The island of Hawaii, as shown in map, Fig. 6, consists of five -volcanic mountains and some small coral reefs. These mountains are: -Mt. Kea, on the north, 13,805 feet in height; Mt. Haulalai, in the -west central part of the island, 8,273 feet in height; Mt. Loa, in the -south central part of the island, 13,675 feet in height; Mt. Kilauea, -twenty miles east of the crater of Loa, 4,040 feet high at the Volcano -House, and 4,158 feet on the highest point on the west, and Kohala, -5,505 feet in height, running through the northwestern part of the -island, and the Kohala mountains in the northwestern part. - -[Illustration: FIG. 6. HAWAII _From Dana's Manual of -Geology_] - -Of these mountains, Mt. Loa and Kilauea are the only active volcanoes, -and are in frequent eruption. Mt. Haulalai was in eruption during -1804. Mt. Kea has not been active during historical times, while Mt. -Kohala has been inactive for so long a time that its slopes are deeply -gullied wherever the rivers flow down them. - -As you can see from the map, Hawaii is very large. It has a length of -ninety-three miles from north to south, and a breadth of eighty miles -from east to west, its area is about 6,500 square miles. With the -exception of small patches of coral reefs, Hawaii is formed entirely -of lava, and is the largest pile of lava in the world with the single -exception of Iceland. - -Where the islands of the Hawaiian chain have coral reefs extending -off their coasts, excellent harbors are found in the deep waters -between the islands and the reefs. Hawaii, however, has no extended -reefs of this character, and, consequently, no first-class harbors. -Hilo, on the eastern coast, is the best harbor, and is, therefore, the -principal settlement. - -A very brief examination of the map of Hawaii will show you that there -are no rivers on the island, except on the sides exposed to the wind, -that is, on the northern and northeastern slopes. Since the yearly -rainfall on Hawaii is large, being in the neighborhood of a hundred -inches, you will understand that considerable rain water falls on the -island. In those parts of the island where it does not run off the -surface it must drain downward through the loose piles of broken rocks -or cinders. A rainfall of one hundred inches a year means that if all -the rain which falls on each square foot of surface was collected -in a flat vessel one foot square with vertical sides it would fill -the vessel to the depth of one hundred inches, or over eight feet. -The drainage of the rainwater downwards through these parts of the -island, must, therefore, be large. - -Another curious fact you can notice on the map, is that the lava -streams of the past fifty years from Mt. Loa indicated by heavy -dotted lines, in no cases begin at the crater, but start at fairly -considerable distances from it. Later on in this chapter we shall -explain the reason for this curious fact. - -Since practically the whole of Hawaii has been formed from the streams -of lava that have flowed at one time or another, you can understand -how great these flows must have been. But to do this fully you must -not only take into consideration the portions of the island that -lie above the ocean and reach into the air at its greatest height -to 13,805 feet above its surface, you must also remember that this -mountain rises from a deep ocean, so that if all the water were -removed, you would see Hawaii towering up above the former level -of the sea to the height of about 31,000 feet, or higher than Mt. -Everest, the highest point on the earth above the present sea level. -This would be, approximately, five and eight-tenths miles. You can -understand, therefore, how great the flow of lava must have been. - -We shall begin the description of Hawaii with the active volcano of -Mt. Loa, or, as it is sometimes called in Hawaii, "The White Mountain." - -You will remember that the eruption of Krakatoa was of the explosive -type. Practically no melted rock or lava escaped from the crater. -Indeed, if it had escaped it would not have been seen; for, not only -the cone near the crater, but also much of the mountain itself was -blown completely out of sight and covered by the waters of the ocean. - -The eruptions of Mt. Loa are of an entirely different type. In Loa -there are no explosions, the eruptions being what are called the -non-explosive or quiet volcanic eruption type. It will be necessary to -explain some of the peculiarities of this kind of eruptions. - -There is a great difference in the liquidity or the ease with which -different kinds of lava flow. Some lava is very thick or viscid, -or is sticky like thick molasses or tar, and therefore flows very -sluggishly. Other lava is thin or mobile, more closely resembling -water in the ease with which it flows. Now, in the case of a volcanic -mountain of fairly considerable height, where the lava possesses -marked liquidity, the lava as it rises from great depths in the tube -of the volcano seldom flows over the top or rim of the crater. This is -not because the force that brings the lava up is unable to carry it -a few thousand feet higher, so that it can run over the brim of the -crater, but because the walls of the volcanic mountains are unable to -stand the great pressure which the mass of liquid lava exerts against -their sides. - -It can be shown that a column of liquid lava 500 feet high, will exert -a pressure on the walls of the crater of about 625 pounds to the -square inch. Therefore, in very high volcanic mountains, long before -the lava can reach the edge of the crater and overflow, the pressure -becomes so great, that cracks or fissures are made in the sides of -the mountain, through which the lava is quietly discharged; when, of -course, the level of the lava in the crater falls considerably. In -volcanoes of the explosive type, no matter what may be the condition -of lava, should a large quantity of water suddenly find an entrance to -a large body of molten lava at some distance below the surface, the -lava would be suddenly thrown explosively into the air, where being -chilled, it would afterwards descend in showers of ashes, cinders, or -volcanic dust. - -In some volcanic mountains such as Mt. Loa, the crater, instead -of being situated at the top of a conical pass of ashes or other -material, consists of a pit-like depression, generally occupying a -level tract or plain at the top of the mountain. This pit is known -as a _caldera_, or _caldron_, or what you might, perhaps, call a -huge kettle or boiler. The pit has more or less vertical sides that -extend downwards for unknown depths to the place from which the lava -comes. The vertical walls of the caldera are not, however, smooth, but -exhibit numerous horizontal ledges, that mark places where portions of -the floor of the caldera were situated at different times. - -At the bottom of the large pit or caldera on the summit of Mt. Loa -can be seen the level floor formed of hardened lava. This floor is -surrounded by vertical walls on which can be seen the broken edges of -the old lake bed. - -Captain Dutton, in a paper on Hawaiian volcanoes, prepared for the -United States Geological Survey, and published in its Fourth Annual -Report for 1882-83, thus describes the appearance at the great crater -as it was in 1882. - - "The summit of Mauna Loa (Mt. Loa), is a broad and large - platform about five miles in length and four miles in - width, within which is sunken the great caldera called - Mokuaweoweo. The distance from the point where we first - reach the summit to the brink of the pit is about a mile - and a half. The surface of the platform is much more rugged - than the slopes just ascended. It is riven with cracks, and - small faults,[2] and piles of shattered rock are seen on - every hand. Nowhere is there to be seen the semblance of - a cinder cone. Doubtless many eruptions have broken forth - from the various fissures on this summit, but only here - and there can insignificant traces of such catastrophes - be definitely distinguished. The absence of fragmental - ejecta (broken rock that are thrown out) is extraordinary. - The shattered blocks, slabs, and spalls (chips) which - everywhere cumber the surface appear to have resulted from - the spontaneous shivering and shattering of the lava sheets - by their own internal tensions as they cooled. - -Fig. 7, taken from Dutton's report, gives the general shape of this -great caldera. Dutton's description of the same is as follows: - - "The length of the main caldera is a little less than - three miles and its width about a mile and three-quarters. - Its floor, viewed from above, appears to be composed of a - series of flat surfaces occupying two distinct levels, the - higher upon the surface of the black ledge, the lower lying - within the ledge. Upon the western side is a small cinder - cone standing close upon the border of the black ledge. - It is the only one visible, either within the caldera or - upon the surrounding summit. Its height is about 125 or 130 - feet. It was seen in operation, throwing up steam, clots of - lava, and lapilli (some of the larger pieces of fragmentary - lava) in the year 1878. The only other diversifications of - the floor are many cracks which traverse it, the larger of - which are distinctly visible from above. Some of them are - considerably faulted. There is no difficulty in recognizing - the fact that the whole floor has been produced by the - sinkage of the lava beds which once continued over the - entire extent of the depression, their undersides having - been melted off most probably by the fires beneath. The - lava beds in the immediate vicinity of the brink upon the - summit platform wear the aspect of some antiquity. They - have become brown and carious by weathering, and, although - no soil is generated, little drifts of gravel are seen - here and there mixed with pumice. Since the caldera was - formed there is no indication that the lavas have anywhere - overflowed its rim. And yet it is a very strange fact that - within a half mile, and again within a mile to a mile and - a half, lavas have been repeatedly erupted within the last - forty years from the summit platform, and have outflowed - at points situated from 700 to 900 feet above the level of - the lava lake within. Traces may also be seen, at varying - distances back of the rim, of very many eruptions in which - the rocks betoken great recency, although no dates can be - assigned to their occurrence." - -[Illustration: FIG. 7. PANORAMA OF MOKUAWEOWEO _From U. S. -Geological Survey_] - -[Illustration: FIG. 8. VIEW OF THE CRATER OF KILAUEA FROM THE -VOLCANO HOUSE _From U. S. Geological Survey_] - -During his visit to this great pit, Captain Dutton succeeded in -climbing down the almost vertical walls on the side of the crater, -and, reaching the surface of the hardened lake, walked over it. It -must have required no little courage to thus venture on the thin -floor of a lake which he knew was filled to great depths with red hot -boiling lava, for he was walking over the surface of a slumbering -volcano, that might at almost any moment awaken, and opening, swallow -him and his companions. Through enormous cracks in the floor, he could -feel the heat from the molten mass, while, through the same openings -came suggestive whiffs of sulphur vapor. - -During the eruption of this mountain, on January 23d, 1859, the light -from the glowing lava streams was bright enough to read fine print at -Hilo, a distance of thirty-five miles. - -During the eruption of 1852, a stream of white-hot lava was thrown up -into the air from one of the fissures to a height of from 300 to 400 -feet. - -[Illustration: STONES AND LAVA THROWN UPWARDS--ERUPTION OF -MOKUAWEOWEO, HAWAII, JULY 4-21, 1899 _From a Stereograph, -Copyright, by Underwood & Underwood_] - -When an eruption takes place in Mt. Loa the column of lava slowly -rises in the crater, threatening to overflow its lowest edges, but -before this can take place the pressure becomes so great that some -portion of the mountain below the crater is fractured and the lava -quietly escapes. - -During some conditions of the mountain every fifteen or twenty minutes -a column of highly glowing lava is shot upwards like a fountain to -a height of 500 feet and over, falling back into the lake in fiery -spray. Unusual heights of these streams are generally followed by an -eruption. - -These curious jets of molten rock certainly cannot be due to the -pressure of higher columns of lava, since the crater itself is near -the top of a high plain. They are believed to be due to steam formed -by the penetration of the rain water that falls on this part of the -mountain. - -You can now understand why the lava streams escaping from Mt. Loa as -shown on the map, in Fig. 6, do not begin at the level of the crater; -for the discharge of the lava does not take place over the rim of -the crater, but through the cracks or fissures formed further down -the sides of the mountains. It must not be supposed, however, that -the fissures are limited to the sides of the mountain where they can -be seen. They probably occur in many places below the surface of the -water on some part of the bed of the ocean. - -The crevices that are formed in this manner in the sides of the -mountain vary greatly in size, some being so narrow that the lava -scarcely flows through them at all but simply fills up the crevice, -hardens on cooling, and mends the cracks in the mountains, in the way -that a crack is mended in a piece of china by the use of glue or in -a wall of masonry by mortar. Through the largest crevices or cracks, -however, large lava streams may continue to flow often for several -weeks, or even longer. - -Sometimes, especially towards the close of the eruptive flow, the -lava may escape disruptively, so that small cones are formed along -the lines of the fissures. Cones of this character are called lateral -cones, and in the case of a volcanic island, where the lava flows out -below the level of the water, the lateral cones sometimes project -above the water and form volcanic islands or dangerous shoals that -impede navigation. - -When the lava pours out of a crevice in the side of the mountain, a -river of molten rock rushes down the slopes, at first like a torrent, -but on reaching the more nearly level ground, it spreads out in great -lava lakes or fields, the surface of which takes on the characteristic -black appearance of basalt, a certain kind of glass, for the lavas of -Mt. Loa are generally basaltic. After an eruption the hardened floor -of lava in the caldera, being no longer supported by the liquid mass -formerly below it, falls in, leaving a large cavity with only the -edges of the old floor clinging to the sides of the pit. - -It will be interesting to give a short account of some of the great -lava streams that have been poured out at different times from Mt. Loa. - -In the great eruption of August 11th, 1855, the lava escaped through -fissures from two to thirty inches in width. Then, flowing in a -continuous stream, it did not stop until it was within five miles of -Hilo. - -In the eruption of January 23d, 1859, the lava stream flowed towards -the northwest on the east side of Haulalai, reaching the sea in eight -days. - -The eruption of March 27th, 1868, was characterized by severe -earthquake shocks, one of which, occurring on the second of April, -destroyed many houses and produced huge fissures in the earth. These -shocks produced great earthquake waves that reached distant coasts. - -Mt. Kilauea, lies at a lower level towards the east. This crater is -situated at 4,040 feet above the level of the sea, and is nearly 6,000 -feet below the caldera on the top of Mt. Loa. - -Fig. 8, taken from the United States Geological Survey, Fourth -Annual Report, for 1882-83, shows a view of Kilauea from the Volcano -House. Dutton gives the following description of the appearance of -Halemaumau, the pit crater or caldera of Kilauea. - - "In front of us and right beneath our feet, over the crest - of a nearly vertical wall, more than 700 feet below, is - outspread the broad floor of the far-famed Kilauea. It - is a pit about three and a half miles in length, and two - and a half miles in width, nearly elliptical in plan and - surrounded with cliffs, for the most part inaccessible to - human foot, and varying in altitude from a little more than - 300 feet to a little more than 700 feet. The altitude of - the point on which we stand is about 4,200 feet above the - sea.... - - "The object upon which the attention is instantly fixed - is a large chaotic pile of rocks, situated in the centre - of the amphitheatre, rising to a height which by an - eye estimate appears to be about 350 to 400 feet. From - innumerable places in its mass volumes of steam are poured - forth and borne away to the leeward by the trade wind. The - color of the pile is intensely black.... - - "Around it spreads out the slightly undulated floor of the - amphitheatre, as black as midnight. To the left of the - steaming pile is an opening in the floor of the crater, - within which we behold the ruddy gleams of boiling lava. - From numerous points in the surrounding floor clouds of - steam issue forth and melt away in the steady flow of the - wind. The vapors issue most copiously from an area situated - to the right of the central pile, and in the southern - portion of the amphitheatre. Desolation and horror reign - supreme. The engirdling walls everywhere hedge it in. But - upon their summits, and upon the receiving platform beyond, - are all the wealth and luxuriance of tropical vegetation - heightening the contrast of the desolation below...." - -[Illustration: FIG. 9. CRATER OF KILAUEA _From Dana's Manual -of Geology_] - -Fig. 9 represents the pit-like crater of Kilauea as it appeared after -the eruption of 1886. Here, as will be seen, there are several lakes -of lava, the largest of which is known as Halemaumau. The eruption of -1886, like all the eruptions of Kilauea, consisted of the escape of -the lava from an opening on the side of the mountain below the crater, -and a sinking in of the hardened floor of the crater. The figure also -shows the position of the New Lake that lies east of Halemaumau. The -extent and appearance of each of these lakes are constantly changing, -both as to height and area. - -Dutton gives the following description of the appearance of the lake -of lava, and some curious phenomena that occur on its surface. He is -describing the general appearance of the pool of molten lava covered -as it is with a hardened black crust: - - "The surface of the lake is covered over with a black - solidified crust showing a rim of fire all around its edge. - At numerous points at the edge of the crust jets of fire - are seen spouting upwards, throwing up a spray of glowing - lava drops, and emitting a dull, simmering sound. The heat - for the time being is not intense. Now and then a fountain - breaks out in the middle of the lake and boils freely for a - few minutes. It then becomes quiet, but only to renew the - operation at some other point. Gradually the spurting and - fretting at the edges augment. A belch of lava is thrown - up here and there to the height of five or six feet, and - falls back upon the crust. Presently, near the edge, a - cake of the crust cracks off, and one edge of it bending - downwards descends beneath the lava, and the whole cake - disappears, disclosing a naked surface of liquid fire. - Again it coats over and turns black. This operation is - repeated edgewise at some other part of the lake. Suddenly - a network of cracks shoots through the entire crust. Piece - after piece of it turns its edge downwards and sinks with - a grand commotion, leaving the whole pool a single expanse - of liquid lava. The lake surges feebly for awhile, but soon - comes to rest. The heat is now insupportable, and for a - time it is necessary to withdraw from the immediate brink." - -It is very curious to think of cakes of hardened lava floating on the -surface of molten lava, but, of course, this is just as natural as -cakes of ice floating on the surface of water; for a cake of hardened -lava is, as you will understand, only a cake of frozen lava, and, -being lighter than the molten lava, must, of course, float on its -surface. - -The disappearance of these cakes of frozen lava and their remelting is -still more curious, and can be explained as follows: The frozen or -solidified mass of black basalt is a trifle lighter than the lava on -which it is floating only while its temperature is high, and therefore -expanded by heat. As soon as it cools, its density increases, and when -it becomes a little greater than that of the liquid lava, it begins to -sink and soon disappears. - -[Illustration: FIG. 10. SECTIONS OF KILAUEA AT DIFFERENT -PERIODS _From Dana's Manual of Geology_] - -Professor Dana, who has made a careful study of the phenomena of -Kilauea, shows in Fig. 10, a cross section of Kilauea at different -times. Before the eruption of 1823, the depth of the crater was from -800 to 1,000 feet. At the eruption the bottom 600 to 800 feet, making -the depth of Kilauea over this deeper central part about 1,500 feet. -The varying depths at different dates are clearly marked on the -drawing. - -The eruptions of Kilauea generally occur as follows: - -First there is a slow rising of the lava in the crater. This rising -continues until the pressure is so great that the mountain is ruptured -at some lower place. Next a discharge of the lava and a sinking to a -level in the conduit that will depend on the position of the crevice. -Then a gradual falling in of the hardened floor of the lake, a portion -of the horizontal walls remaining on the sides of the caldera. - -The eruption of Kilauea, however, has not always been of the quiet -type. There was an eruption in the year 1789 that would appear to -have been of the explosive variety. The following account is given by -Dana as taken from a history of the Sandwich Islands by the Rev. I. -Dibble, published in 1843: - -"The army of Keoua, a Hawaiian chief, being pursued by Kamehamoha, -were at the time near Kilauea. For two preceding nights there had -been eruptions, with ejections of stones and cinders. The army of -Keoua set out on their way in three different companies. The company -in advance had not proceeded far before the ground began to shake and -rock beneath their feet, and it became quite impossible to stand. -Soon a dense cloud of darkness was seen to rise out of the crater, -and, almost at the same instant, the thunder began to roar in the -heavens and the lightning to flash. It continued to ascend and spread -around until the whole region was enveloped, and the light of day -was entirely excluded. The darkness was the more terrific, being -made visible by an awful glare from streams of red and blue light, -variously combined through the action of the fires of the pit and the -flashes of lightning above. Soon followed an immense volume of sand -and cinders, which were thrown to a great height, and came down in a -destructive shower for many miles around. A few of the forward company -were burned to death by the sand, and all of them experienced a -suffocating sensation. The rear company, which was nearest the volcano -at the time, suffered little injury, and after the earthquake and -shower of sand had passed over, hastened on to greet their comrades -ahead on their escape from so imminent a peril. But what was their -surprise and consternation to find the centre company a collection -of corpses! Some were lying down, and others were sitting upright, -clasping with dying grasp their wives and children, and joining noses -(the mode of expressing affection) as in the act of taking leave. So -much like life they looked that at first they supposed them merely -at rest, and it was not until they had come up to them and handled -them that they could detect their mistake." Mr. Dibble adds: "A blast -of sulphurous gas, a shower of heated embers, or a volume of heated -steam would sufficiently account for this sudden death. Some of the -narrators who saw the corpses, affirm that though in no place deeply -burnt, yet they were thoroughly scorched." As you will see in Chapter -XI, this sudden and awful death due to highly heated air and dust -particles, caused even a greater loss of life in the catastrophic -eruption of Pelee, in Martinique on May 8, 1902. - -By reason of its situation at a lower level on the slopes of Mt. Loa, -Kilauea was at one time thought to be one of the craters lower down -on the slopes of Loa. This was the opinion of Professor Dana when he -examined the district in 1840. Since this time the region has been -more carefully studied, and Mt. Loa and Kilauea, are now generally -regarded as separate and independent volcanoes, neither of which acts -as a safety valve for the other. - -We shall not attempt in this chapter to say anything concerning the -sources or places from where these great supplies of lava have been -drawn. This will be left to some subsequent chapter, after we have -described still other volcanoes. - -The outlines of mountains like Mt. Loa or Kilauea differ greatly from -mountains like Vesuvius; their slopes, like the slopes of all other -Hawaii volcanoes, have an inclination which does not exceed 10 deg. -The lava streams, therefore, as they flow down the mountains, move -more slowly than they would were the slopes more precipitous, as in -mountains like Vesuvius. - -There have been many eruptions of Kilauea. That which occurred in the -year 1840, was of great magnitude (see map, Fig. 6), and began in a -fissure southwest of the crater. The principal eruption, however, -broke out about twelve miles from the sea coast, and about twenty-five -miles east of Kilauea. Here an enormous mass of lava forming a stream -nearly three miles wide reached the ocean at Nanawale. - -When an eruption takes place on Mt. Loa through a fissure at the -height of 10,000 to 13,000 feet the length of the lava streams is -frequently as great as twenty-five to thirty miles. Often the lava -though hardening at the surface will continue to flow underneath -through huge tunnels, of which the top and sides are composed of -solidified parts of the same lava stream. After the flow has ceased -long hollow tunnels often remain. If the lower end of such a tunnel -containing molten lava is momentarily closed, the pressure of the -lava above may not only burst through the obstruction, but may even -throw the lava upwards in jets 300 to 700 feet high. Probably most of -you have seen illumined fountains where jets of water are beautifully -lighted up by different colored electric lights placed below them. -Such fountains, however, can but poorly compare either in beauty or -grandeur with these wonderful lava fountains, common on the slopes of -Mt. Loa during an eruption. - - - - -CHAPTER IV - -THE VOLCANIC ISLAND OF ICELAND - - -The island of Iceland consists of a number of volcanic mountains some -of which are still active. As can be seen from the map, shown in -Fig. 11, Iceland lies in the North Atlantic Ocean, immediately below -the Arctic Circle, about 250 miles east of Greenland, and 600 miles -west of Norway. Its length from east to west is about 300 miles, and -its breadth about 200 miles, its total area, including the adjacent -islands, being more than 40,000 square miles. - -Were all the water removed from the North Atlantic Ocean, it would be -seen that Iceland rests on the bed of the Atlantic, on a submarine -plateau or highland; for, in this part of the ocean the water is only -from 1,500 to 3,000 feet deep. This submarine plateau extends as far -as Norway on the east, Greenland on the north, and the island of Jan -Mayen on the northeast. Immediately north of the plateau the ocean -suddenly drops to a depth of 12,000 to 15,000 feet. - -[Illustration: FIG. 11. ICELAND] - -Toward the south the plateau extends with but few interruptions -through the middle of the ocean to a shoal known as the _Dolphin -Shoal_, as far as lat. 25 deg. N. This part of the ocean, which can only -relatively be called a shoal, is not generally deeper than 9,600 feet, -although in some places the water is more than 12,000 feet deep. On -each side of the Dolphin Shoal the water is much deeper, being in -places 15,000 feet on the east, while on the west there are depths -as great as from 17,000 to 21,000 feet. - -This sunken plateau, possibly including the shallower plateau on the -north, is believed by some to be the remains of the fabled continent -of _Atlantis_, to which we shall refer in another part of this book. - -The coast line of Iceland is unbroken on the southeast, but the -remainder of the coast is deeply indented with bays or fiords in which -are many excellent harbors. - -Iceland is liable to frequent earthquake shocks and volcanic -eruptions. From careful records that have been preserved in the -history of the island, we learn that since the beginning of the -twelfth century there have practically never been intervals longer -than forty years, and more generally not longer than twenty years, -in which there has not been a great earthquake or a great volcanic -eruption. These volcanic eruptions are often very protracted. For -example, one eruption of the volcano Hecla continued for six years -without ceasing. Sir Charles Lyell, the great English geologist, -writes as follows about Iceland: - - "Earthquakes have often shaken the whole island at once, - causing great changes in the interior, such as the sinking - down of hills, the rending of mountains, the desertion of - rivers by their channels, and the appearance of new lakes. - New islands have often been thrown up near the coast, some - of which still exist, while others have disappeared, either - by subsidences or the action of the waves. - - "In the interval between eruptions innumerable hot springs - afford vent to the subterranean heat, and solfataras - discharge copious streams of inflammable matter. The - volcanoes in different parts of the island are observed, - like those of the Phlegraean Fields, Italy, to be in - activity by turns, one vent often serving for a time as a - safety valve for the rest. Many cones are often thrown - up in one eruption and in this case they take a linear - direction, running generally from southeast to northwest." - -The volcanic eruptions of Iceland belong for the greater part to the -fissure type. During a volcanic eruption in Iceland the ground is -split in fissures or cracks, generally parallel to each other, and -varying in width from a few inches to several yards. These fissures -extend for great distances across the country. The lava quietly wells -out along the fissures not unlike the way quiet spring waters flow -from their reservoirs. - -According to Dr. Th. Thoroddsen, the Icelandic geologist, there are -two systems of fissures extending through Iceland, from southwest to -northeast in the southern part of the island, and from north to south -in the northern part. Where two lines of fissures cross each other the -points of intersection may be especially active. - -Dr. Th. Thoroddsen arranges the volcanoes of Iceland under three -heads, i. e., _cone-shaped volcanoes_; _lava cones_; and _chains of -craters_, the last being the commonest. Out of 107 volcanoes examined -by him in Iceland, eight were of the Vesuvian type, or were built up -of layers of lava and volcanic ashes; sixteen were of the lava-cone -type, similar to Mt. Loa, of the Hawaiian Islands, and the remaining -eighty-three were of the type of crater chains. - -The volcano of Snaefell Joekul, 4,710 feet above the level of the -ocean, is built up of alternate layers of lava and hardened volcanic -mud. It is not, however, a true cone-shaped mountain. - -The largest volcano in Iceland, the Dyngjufkoell, with its immense -crater of Askja, has an area of some twenty-five square miles. In its -form it resembles Snaefell. - -Volcanoes of the lava-cone type have been built up entirely of lava -and have a slight angle of inclination. These volcanoes range in size -from small hillocks to the largest mountains on the island. Their -cones generally stand on a base of wide circumference and frequently -rise to great heights, the top being occupied by a caldera, or pit -crater like that on Mt. Loa or Kilauea. - -Volcanoes of the type of chain-craters follow the natural fissures in -the crust. These craters are generally low, seldom being more than 350 -feet high. - -There are also seen in Iceland caldron-shaped depressions that have -been formed by explosive eruptions. One of the best instances of such -craters is Viti, on the side of Mt. Krafla. This crater was formed by -the sudden eruption of May 17th, 1724. - -The lava sometimes quietly runs out of the entire length of the -fissure without forming any cone. This was the case of a great fissure -known as the Eldgja Chasm. Here three lava streams covered an area of -270 square miles. - -As the lava comes out of the fissures, it generally produces long -ramparts of slags, and blocks of lava that are piled up on either side -of the fissure. Sometimes a line of low cones is built up. These cones -consist of heaps of slag, cinders, and blocks of lava. Their craters -are not rounded as in the case of volcanoes of the Vesuvian type, but -are oblong, or have their greatest diameter extending in a direction -of the fissure. - -Icelandic lava as it escapes from the fissures is peculiar in that -it is very viscid or plastic and can be readily drawn out into long -threads that can be spun into ropes. When such lava runs down the -sides of a steep slope, it often splits on cooling into separate -blocks. Where it runs over flat, level ground, however, it spreads -uniformly on all sides, producing vast level lava deserts that are as -flat as the surface of a well built floor. - -There are many rivers in the north and the west of Iceland. Now, as -the lava streams flow out of the fissures they enter the channels of -the rivers so that the streams of water must find new paths to the -sea, and this operation may be repeated again and again. Often the -time between eruptions is long enough to give the rivers opportunity -to cut deep channels or gorges in their new channels; but on the next -escape of the lava these gorges and valleys are again filled with the -molten rock, and the rivers must begin their channel cutting all over. - -You will note the frequent use of the word Joekul, as Snaefell Joekul, -Skaptar Joekul, Orefa Joekul, etc. The name Joekul means a large mass of -ice, or a mountain that is continually covered with snow, for example, -Snaefell Joekul, is a beautifully shaped, snow-covered mountain -situated on a point of land on the western coast of the island, -extending out nearly fifty miles into the sea, between the Faxa Fiord -and the Briela Fiord. It is a very conspicuous object, being visible -to passing ships at considerable distances from the island. Orefa -Joekul is the highest mountain in Iceland. Skaptar Joekul is one of the -active volcanoes of Iceland. - -There can be no doubt that Iceland has been formed entirely by lava -thrown up from the bottom of a submarine plateau, until it extended -above the surface of the waters. To make an island entirely of lava -with an area of 40,000 square miles, must, of course, have required -many cones or craters that continued to pour forth lava for periods of -time much longer than those during which man has lived on the earth. - -The surface of Iceland is far from attractive. The interior is -practically a vast lava desert, covered with snow-clad mountains or -Joekuls. There is no plant life except in marshy lands near the coasts, -and even here scarcely enough grass is raised to feed the few cattle -and horses owned by the inhabitants. There is no agriculture, owing -to the very short summers, so that all grain is brought from Europe. -Every now and then the grass crop is destroyed by accumulation of -Polar ice on the northern and western coasts. Such failures are always -attended by great famines, when many of the people die. - -Should you ever visit Iceland you would probably be surprised to hear -the people speaking about their forests. You might go over all the -coasts of the island without seeing anything larger than a birch bush, -not much higher than six feet. These are what the Icelanders like to -speak of as their forest trees, and I suppose there is no harm done, -if one only understands just what they mean by "trees." - -While, however, Iceland has practically no trees, yet it has no -difficulty in obtaining a plentiful supply of timber, since in the -deep fiords or bays on the western and southern coasts there can -always be found much drift timber brought there by the ocean currents -from the forests of America. - -The principal town or settlement in Iceland is Reykjavik, the capital -of the island, on the southwestern coast; this is the chief trading -place on the island. Thingvalla is also an important town. - -The lavas that form the entire mass of Iceland were thrown out both -before and since the glacial age. It is the opinion of Geikie that -these outflows have continued uninterruptedly since that age to the -present time. It is known that the lavas of Iceland were thrown out -both before and after the glacial age, because during the glacial age, -deep cuttings or groovings were made on the surface of the earth by -the glaciers as they slowly moved over it. Now lava beds containing -the glacial scratches have been found and resting on them are other -lava streams. The scratched lavas must, therefore, have been thrown -out before the glacial age, and the second lavas after that age. - -Let us now examine some of the more active volcanoes of Iceland and -their eruptions. We will begin with the well-known volcano of Skaptar -Joekul. - -The following description of this volcano has been taken from a book -on Iceland by E. Henderson, published in Boston, 1831. Skaptar Joekul -lies in the south central part of Iceland about forty odd miles from -the coast. It takes its name from the Skaptar River, down whose -channel the lava flowed its entire distance of forty miles from the -ocean. Skaptar Joekul consists of about twenty conical hills lying -along one of the fissures that extends from northeast to southwest. - -It appears from Henderson's account that people living in the -neighborhood of Skaptar Joekul were greatly alarmed by repeated -earthquakes that were felt at different times from the first to the -eighth of June, 1783. These earthquake shocks increased in number and -violence, so that the people left their homes and awaited in terror -the coming catastrophe. On the morning of the eighth a prodigious -cloud of dense smoke darkened the air, and the surrounding land soon -became covered with ashes, pumice, and brimstone. As is common with -eruptions in Iceland, that have been preceded by long periods of rest, -the heat produced by the escaping lava and the sulphurous gases, -melted such quantities of ice that great floods were produced in the -rivers. - -On the 10th of June vast torrents of lava that had been escaping -from the craters entered the valley of the Skaptar River, and -commenced flowing through its channel. Immense quantities of steam -were produced, and, in less than twenty-four hours, the river was -completely dried up, for the lava had collected in the channel, -which in many places flows between high rocks from 400 to 600 feet -in height and nearly 200 feet in breadth, and had not only filled -the river to its brink, but had overflowed the adjacent fields to a -considerable extent, and flowing along the cultivated banks of the -river destroyed all the farms in its path. - -On gaining the outlet, where the channel of the Skaptar emerged -into the plain, it might have been supposed that the burning flood -would have at once spread over the low fields, which lay immediately -before it, but, contrary to all expectations, this flow was for a -time stopped by an immense unfathomed abyss in the river's bed, into -which it emptied itself with great noise. When this chasm was at -last filled, the lava increased by fresh flows, rose to a prodigious -height, and breaking over the cooled mass, proceeded south towards the -plain. - -In the meantime the thunder and lightning, together with subterranean -roars, continued with little or no intermission. - -On the 18th of June, 1783, another dreadful eruption of red hot lava -came from the volcano. This flowed with great velocity and force over -the surface of the cooling stream that had been thrown out principally -on the tenth of the month. Floating islands consisting of masses of -flaming rock were seen on the surface of the lava stream, and the -water that had been banked up on both sides of the stream was thrown -into violent boiling. - -In the meantime people living along the Hverfisfloit, the next largest -river to the east of the Skaptar, had not yet been visited by the -lava streams. It is true that their vegetation had been destroyed by -showers of red hot stone and ashes, and that both atmosphere and water -were filled with poisonous substances. The land had also been plunged -in utter darkness, so that it was scarcely possible at noonday to -distinguish a sheet of white paper held up at the window from the -blackness of the wall on either side. But the molten lava streams had -not yet reached the people of this valley and they hoped that the -eruption would soon be over, and that the lava flow would continue to -follow the Skaptar. On the 3d of August, however, they were alarmed by -seeing steam escaping from the River Hverfisfloit, and soon all its -water was dried up, and a fresh lava flow poured down upon them. As in -the case of the Skaptar, the melted rock completely filled the empty -channel to the brink, and then overflowing, covered the low grounds on -both sides, so that by the ninth of August it had reached the open and -level country near its mouth and in the course of a few hours spread -itself for a distance of nearly six miles across the plain. This flow -continued after the end of August, and, indeed, even as late as the -month of February, 1784, when a new eruption took place in this part -of the country. - -Hecla, another well-known volcano in Iceland, situated about thirty -miles from the southern coast, consists of three peaks, the central of -which is the highest. Its craters form vast hollows on the sides of -these peaks, and at the time of the eruption in 1766 were covered with -snow. Hecla is believed to have been an active volcano long before -Iceland was inhabited. No less than twenty-three eruptions have been -recorded between A. D. 1004 and the great eruption of 1766-68. - -Volcanic history frequently repeats itself. There had been no great -eruption of Hecla for a period of about twelve years, and the people -living in the neighborhood were congratulating themselves on the -belief that the mountain was becoming actually extinct, and that -therefore they need not trouble themselves about eruptions. Others, -however, more farseeing, pointed out the fact that the lakes and -rivers in the vicinity did not freeze, and that the amount of water -they contained was greatly decreased. - -The following description of the great eruption of Hecla that was -remarkable both for its violence, as well as for the time during which -it continued, is taken from Symington's "Sketches of Faroe Islands and -Iceland": - - "On the 4th of April, 1766, there were some slight shocks - of an earthquake, and early next morning a pillar of sand, - mingled with fire and red hot stones, burst with a loud - thundering noise from its summit. Masses of pumice, six - feet in circumference, were thrown to the distance of ten - or fifteen miles, together with heavy magnetic stones, - one of which, eight pounds weight, fell fourteen miles - off, and sank into ground still hardened by the frost. The - sand was carried towards the northwest, covering the land, - 150 miles round, four inches deep, impeding the fishing - boats along the coast, and darkening the air, so that at - Thingore, 140 miles distant, it was impossible to know - whether a sheet of paper was white or black. At Holum, 155 - miles to the north, some persons thought they saw the stars - shining through the sand-cloud. About mid-day, the wind - veering round to the southeast, conveyed the dust into the - central desert, and prevented it from totally destroying - the pastures. On the 9th of April, the lava first appeared, - spreading about five miles towards the southwest, and on - the 23d of May, a column of water was seen shooting up in - the midst of the sand. The last violent eruption was on the - 5th of July, the mountains, in the interval, often ceasing - to eject any matter; and the large stones thrown into the - air were compared to a swarm of bees clustering around the - mountain-top; the noise was heard like loud thunder forty - miles distant, and the accompanying earthquakes were more - severe at Krisuvik, eighty miles westward, than at half the - distance on the opposite side. The eruptions are said to - be in general more violent during a north or west wind than - when it blows from the south or east, and on this occasion - more matter was thrown out in mild than in stormy weather. - Where the ashes were not too thick, it was observed that - they increased the fertility of the grass fields, and - some of them were carried even to the Orkney Islands, the - inhabitants of which were at first terrified by what they - considered showers of black snow." - -The largest volcano in Iceland is Dyngjufjoll. This has on its summit -the gigantic crater of Askja, some twenty-five square miles in area. -This crater is of the intermediate form; the most general form of -volcanoes on the island consisting of a number of craters that closely -follow fissures. - -Professor Johnstrup, in a report to the Danish Government, on this -volcano, states that the valley of Askja has been gradually filled -by repeated flows of lava from enormous craters on the edge of the -mountain. In many places the surface of the earth is covered with -bright red pumice stone that was thrown out during an eruption March -29th, 1875. Some of these craters are filled with steam that escapes -with an almost deafening roar. The surprising feature of this eruption -was the immense quantity of pumice stone that escaped. - -The volcanoes in the Nyvatus Oraefi are entirely different. This -barren plain is thirty-five miles in length and thirteen miles in -breadth. Suddenly on the 18th of February, 1875, a volcano appeared in -the centre, and four other craters were formed at subsequent dates. -The mass of lava that was thrown out of these openings has been -estimated at 10,000,000,000,000 cubic feet, or eighteen times the -estimated mass of lava that has been emitted from Vesuvius between -1794 and 1855. This lava is basalt. - - - - -CHAPTER V - -VESUVIUS - - -The old Greeks and Romans had but little knowledge of volcanoes. They -only knew the volcanic mountains in the Mediterranean Sea. Here there -are three volcanic regions:--one in the neighborhood of Naples; one -including Sicily and the neighboring islands, and the other that of -the Grecian Archipelago. - -Some idea can be had of these three regions from a map of the -Mediterranean shown in Fig. 12. The principal volcanoes are Vesuvius, -Etna, Stromboli, and Vulcano, a mountain, by the way, that gave its -name to all volcanic mountains. In this chapter we will describe the -volcano of Vesuvius, the most active, though by no means the largest -of the volcanoes of the Mediterranean. - -But, before doing this, it will be well first to describe briefly the -volcanic districts surrounding Vesuvius. - -As shown in Fig. 13, this district includes Vesuvius, Procida, and -Ischia. - -[Illustration: FIG. 12. THE MEDITERRANEAN] - -Ischia is a small island measuring about five miles from east to west, -and three miles from north to south. There were such terrific volcanic -eruptions on this island long before the Christian Era, that several -Greek colonies were forced to abandon it. A colony established long -afterwards, about 380 B. C., by the king of Syracuse also -had to depart. Strabo, the Grecian geographer (born about 63 B. -C.), states that, according to tradition, terrific earthquakes -occurred on the island a little before his time, and its principal -mountain threw out large quantities of molten rock, which flowed into -the sea. At the time of this eruption there were earthquake waves in -the sea, the waters of which slowly receded, leaving large portions -of the bottom uncovered, and rushing, afterwards, violently over -the land, caused great destruction. It was during this disturbance, -so Strabo asserts, that the island of Procida was formed by being -violently torn from Ischia. - -[Illustration: FIG. 13. THE VOLCANIC DISTRICT AROUND VESUVIUS] - -The Phlegraean Fields was a name given by the ancients to some of the -lowlands in the neighborhood of Naples; they were believed to be under -the special protection of the Roman gods. When the frequent earthquake -shocks shook these fields, the Roman people believed that conflicts -were taking place between their gods and slumbering giants confined in -the regions below the surface. - -It is more than probable that Mt. Vesuvius has always been the centre -of these volcanic disturbances. Long before the Christian Era, -however, Vesuvius, or Somma, the name given to the old crater that -then occupied the summit of the mountain, had been an extinct crater. -Indeed, it had been so quiet that the people who lived on its slopes -did not appear to know they were living on the slopes of a slumbering -volcano. Their knowledge of volcanic mountains must have been very -limited, for this mountain with the huge pit at its summit had all -the appearance of a volcanic crater. When they climbed to the top of -the mountain, which, of course, they frequently did to look after the -vineyards they were cultivating on the slopes, and looked down into -the deep pit from the rocks on its edge, they could see at the bottom -of a great central pit three miles in diameter, a lake, with room here -and there to enable one to walk along its borders. The walls of the -precipice were covered with luxuriant vines. - -When we say that none of the people even suspected that Vesuvius had -ever been in a state of eruption, we must except some of their learned -men. For both Diodorus Siculus, a native of Sicily, who lived about -10 B. C., and wrote an Universal History, containing some -forty volumes, of which only about one-third remain, and Strabo, the -Geographer, pointed out in a general manner, that Vesuvius, and much -of the surrounding country, looked as if it had been eaten by fire. -Then, too, a Roman philosopher who lived between A. D. 1 and -A. D. 64, spoke of Vesuvius being "a channel for the eternal -fire!" - -Let us now endeavor to obtain some idea of the appearance of this -region a short time before A. D. 79, when Vesuvius burst -forth in a terrific eruption. The slopes of the mountain were covered -with the rich vegetation that characterizes this part of Italy. -When most volcanic ashes and lava have been exposed for some time to -the atmosphere they make a very fertile soil. Now, this soil on the -slopes of Vesuvius made the vineyards that covered the mountain slopes -and the fields for miles around its base, bear very plentifully, -so that the people lived very comfortably. Here and there on the -slopes of the mountain large towns like Herculaneum and Pompeii had -long been established, while, in the distance, was the large city of -Naples. Besides these there were numerous populous towns and villages -scattered here and there over the plain or on the lower mountain slope. - -You have all probably read of the Roman gladiator, Spartacus. -Spartacus was a Thracian by birth, and while a shepherd had been taken -prisoner by the Romans and sold to a trainer of gladiators at Capua. -Chaffing under the tyranny of the Romans, who forced him to fight in -the arena with men and beasts, he revolted against his masters, and -with a band of some seventy followers, fled to a mountain fastness in -the crater of Vesuvius. Proud Rome sent a few men to recapture him, -with scourges for his punishment, but they were beaten by Spartacus. -Every day dissatisfied men like himself escaped from the Romans and -joined his ranks. Rome sent a larger body of men against Spartacus, -but they also were beaten. At last, recognizing the gravity of the -position, the Roman Praetor, Clodius, was sent against Spartacus with -an army of some three thousand men. Clodius caught Spartacus in the -crater and guarded the only space by which it seemed possible for -Spartacus to escape. Using the vines that covered the precipitous -walls of the crater, Spartacus did escape, and falling unexpectedly -on the armies of Clodius, routed them. After this victory, Spartacus -with an army of over 100,000 men overran southern Italy, and sacked -many of the cities of the Roman Campania. During this time Spartacus -defeated one Roman army after another, until finally, in the year 71 -B. C., Crassus was sent against him and vainly endeavored -to conquer him. Being unsuccessful, Crassus urged the Roman Senate -to recall Lucullis from Asia and Pompey from Spain, and finally poor -Spartacus was cut down in a fight he made against Crassus and Lucullis. - -But let us come to the great eruption of Vesuvius in A. D. -79. The people living on the slopes of Vesuvius were not without -plenty of warnings of the dreadful catastrophe that was coming. As -early as A. D. 63 there was a great earthquake that shook the -country far beyond Naples. In Pompeii, then a flourishing city, the -Temple of Isis was so much damaged that it had to be rebuilt. - -Even if the earthquake shocks had not foretold the coming eruption, -there were other signs. The height of water in the wells decreased. -Springs that had never before been known to fail, dried up completely. -These changes, as we well know, were due to the red hot lava being -slowly forced up from great depths into the tube connected with the -crater. - -The earthquake shocks continued at irregular intervals for sixteen -years, until, on the 25th of August, A. D. 79, about one -o'clock in the afternoon, Vesuvius burst forth in the terrible -eruption that destroyed the towns of Pompeii and Herculaneum. Pompeii -was a seaport town situated near the mouth of the River Sarno, -about fifteen miles southeast of Naples. It was a beautiful place, -containing many splendid temples. Its people for the greater part -lived luxuriously, for Pompeii was the summer resort of the richer -people of Naples, some of whom lived there during the hottest months -of the year. - -Herculaneum, the other town, was nearer Naples, only five miles from -the city. It was also, like Pompeii, a beautiful town, and contained -many splendid buildings. In each town there were magnificent baths and -a large theatre. The inhabitants spent so much of their time in the -open air, or in the baths, that it was not necessary for them to build -very large houses. The houses, however, were well built, and though -generally consisting of practically a single story, were provided with -all the luxuries that great wealth could command. - -On August 25th, A. D. 79, severe earthquake shocks again -visited this part of the world and Vesuvius suddenly threw up from -its crater an immense column of black smoke, which, rising high in -the air, spread out in the form of a huge mushroom, or, perhaps, more -like the umbrella pine tree of the neighborhood. Rapidly spreading on -all sides, the smoke soon completely shut out the light of the sun, -and wrapped the earth in an inky darkness, except for a red glare from -columns of molten rock that rushed out of the crater. - -From the dark cloud immense quantities of red hot stones, pumice, and -volcanic ashes descended on the earth. At the same time there fell -a deluge of rain, caused by the sudden condensation of the enormous -amount of water vapor that was thrown out from the crater during the -eruption. Fortunately, very few of the people were killed in either of -the cities of Pompeii and Herculaneum, although some bodies were found -in the ruins. Most of the people escaped through the darkness and -gloom, continuing to flee from the city for at least three days. - -Both cities were covered so deep with ashes or mud that the tops of -the tallest buildings were no longer visible. Pompeii was buried by -showers of ashes or volcanic cinders, and Herculaneum mainly by vast -floods of aqueous lava. - -So completely were these cities covered that their very existence was -at last forgotten. It is true that Titus, who was then Emperor of -Rome, endeavored to clear away the ashes and rebuild Pompeii, but the -task was so great that he finally abandoned it. - -During the year 1592, the architect Fontana, while superintending the -building of an aqueduct, came across some ancient buildings. At a much -later date, in 1713, some workmen, while digging a well in the village -of Portici, uncovered three marvellously beautiful marble statues. In -the year 1738, the same well was dug deeper, when traces of the old -theatre of Herculaneum were discovered. Some effort was then made to -excavate the city and many of the public buildings and private houses -were uncovered, and statues, mosaics, wall paintings, and charred -manuscripts of papyrus were found. A few of these have been unrolled -and deciphered, but owing to the difficulty of doing this, without -destroying them, the greatest number still remain unread. - -In 1860, the Italian Government began a systematic excavation of the -buried cities, and now both Pompeii and Herculaneum are thrown open to -the sunlight so that one can walk through the old streets, and look -into the houses, in which, before A. D. 79, the people lived -so happily. - -Many interesting stories are told about the discoveries that were -made during the government excavations. The skeleton of one of the -inhabitants was found grasping a money bag. He might have escaped, -but had gone back to get his money. He got it, but remained with it. -In another place, the skeletons of a number of people were found in -an underground room or cellar of a house, where were also found some -mouldy bread and empty water flasks. Instead of leaving the city, -which they might have done, they had retreated to the underground -room for safety, but the fine volcanic dust drifted in and suffocated -them. - -The younger Pliny, the historian, has given an excellent account of -some features of this great eruption. It appears that his uncle was -stationed with the Roman fleet, in the Bay of Naples, at the time of -the eruption. He describes the dark cloud of ashes that was formed -over Vesuvius. He refers to the rapidity with which it spread, and -to the showers of ashes, cinders, and stones that it rained down on -the earth. His uncle, the elder Pliny, landed on the coast, and was -afterwards killed by a cloud of sulphurous vapor that swept down the -side of the mountain. - -The following letter from the younger Pliny, describing his flight -with his mother from Misenum, is quoted from Dana's "Characteristics -of Volcanoes." - - "It was now seven o'clock [on the morning of August 25th], - but the light was still faint and doubtful. The surrounding - buildings had been badly shaken, and although we were in - an open spot [a little yard between his uncle's house and - the sea], the space was so small that the danger of a - catastrophe from falling walls was great and certain. Not - till then did we make up our minds to go from the town.... - When we were free from the buildings we stopped. There we - saw many wonders and endured many terrors. The vehicles we - had ordered to be brought out kept running backward and - forward, though on level ground; and even when blocked - with stones they would not keep still. Besides this, we - saw the sea sucked down and, as it were, driven back by - the earthquake. There can be no doubt that the shore had - advanced on the sea, and many marine animals were left high - and dry. On the other side was a dark and dreadful cloud, - which was broken by zigzag and rapidly vibrating flashes of - fire, and yawning showed long shapes of flame. These were - like lightning, only of greater extent.... - - "Pretty soon the cloud began to descend over the earth - and cover the sea. It enfolded Capreae and hid also the - promontory of Misenum." ... The flight was continued. - "Ashes now fell, yet still in small amount. I looked - back. A thick mist was close at our heels, which followed - us, spreading out over the country, like an inundation." - ... Turning from the roar in order to avoid the fleeing, - terror-stricken throng, they rested. "Hardly had we sat - down when night was over us--not such a night as when there - is no moon and clouds cover the sky, but such darkness as - one finds in close-shut rooms. One heard the screams of - women, the fretting cries of babes, and shouts of men.... - - "Little by little it grew light again. We did not think - it the light of day, but a proof that the fire was coming - nearer. It was indeed fire, but it stopped afar off; and - then there was darkness again, and again a rain of ashes, - abundant and heavy, and again we rose and shook them off, - else we had been covered and even crushed by the weight.... - At last the murky vapor rolled away, in disappearing smoke - or fog. Soon the real daylight appeared; the sun shone out, - of a lurid hue, to be sure, as in an eclipse. The whole - world which met our frightened eyes was transformed. It was - covered with ashes white as snow." - -Young Pliny and his mother returned to Misenum, and survived the -perils to which they were exposed. - -It was during this eruption that a large part of the old crater was -blown off the mountain by the tremendous force at work. - -There have been many eruptions of Vesuvius since the great eruption -of A. D. 79. One of these occurred during the reign of Severus, -A. D. 203. It was during this eruption that an additional part of the -old crater of Somma was blown away. - -Another great eruption occurred A. D. 472. Then great -quantities of volcanic dust were thrown up into the air, and falling, -covered practically all parts of Europe, producing darkening of the -sun and great fear as far as the city of Constantinople. - -But what was perhaps a still greater eruption occurred during December -of 1631. This eruption spread great quantities of ashes over the -country for hundreds of miles around, and great streams of mud rushed -down the slopes of the mountain. Buccini gives the following account -of this eruption: - - "The crater was five miles in circumference, and about - 1,000 paces deep. Its sides were covered with brushwood, - and at the bottom there was a plain on which cattle grazed. - In the woody parts wild boars frequently harbored. In one - part of the plain, covered with ashes, were three small - pools, one filled with hot but bitter water; another with - water saltier than the sea, and a third with water that - was hot but tasteless. But at length these forests and - grassy plains were consumed, being suddenly blown into the - air and their ashes scattered to the winds. In December, - 1631, seven streams of lava poured at once from the crater - and overflowed several villages, on its flanks, and at the - foot of the mountain. Reisna, partly built over the ancient - city of Herculaneum, was consumed by the fiery torrent. - Great floods of mud were as destructive as lava. This is - no unusual occurrence during these catastrophes for such - is the violence of the rains produced by the evolution of - aqueous vapors that torrents of water descend the cone and - become charged with impalpable volcanic dust, and rolling - among ashes, acquire sufficient consistency to deserve the - ordinary appellation of aqueous lava." - -Of course, you will understand that we have given only a few of -the most notable of the eruptions of Mt. Vesuvius. Since the yea -A. D. 1500 there have been no less than fifty-six recorded -eruptions, that of the year 1857 being especially violent. - -Omitting these eruptions we at last come to the great recent eruption -of 1872. - -Fortunately, the eruption of 1872, as well as still more recent -eruptions that have occurred, have been more accurately described than -have most volcanic eruptions, for the Italian Government, recognizing -the value to the natives of Italy of a knowledge of what was going on -at the crater of Vesuvius, has maintained for the past thirty years -an observatory on the western part of the mountain. This observatory -has been placed in charge of Prof. Luigi Palmieri, a well-known -student of volcanoes and earthquakes. At this place records are kept -of the behavior of the volcano, of all earthquake disturbances, as -well as other phenomena. At the same time, by the use of photography, -excellent pictures have been obtained showing the appearance of the -sky during an eruption. - -Vesuvius had been in a quiet state from November, 1848, to the year -1871, when small quantities of lava flowed continuously for several -months. Again, early in 1872, other quiet eruptions of lava continued -for weeks at a time. Finally, on April 26th, of that year, a violent -explosive eruption occurred. The following account has been taken from -Palmieri's report, entitled, "The Eruption of Vesuvius in 1872." - -On April 23d the recording earthquake instruments, the seismographs, -were greatly affected. On the evening of the 24th lava streams flowed -down the cone in various directions. These streams were continued -on the 25th and the 26th, so that on the night of the 26th the -observatory lay between two streams of molten lava that threw out so -much heat that the glass windows in the observatory were cracked, -and a scorching smell was quite perceptible in the rooms. The cone -of the mountain was deeply fissured, lava escaping freely from all -the fissures, so that the molten rock appeared to ooze from over its -entire surface, or as Palmieri expressed it, "Vesuvius sweated fire." - -This great cracking or fissuring of the cone was accompanied by the -opening of two large craters at the summit, that discharged, with a -great noise, immense clouds of steam, dust, lapilli, and volcanic -bombs. These latter are very curious and consist of masses of soft -lava that are thrown high into the air by the outrushing columns of -steam. Being rotated or spun, as they rise in the air, they assume a -spherical shape. Some of these volcanic bombs were thrown to a height -estimated by Palmieri to have been nearly 4,000 feet above the top of -the mountain. When the height of a projectile is known, the velocity -with which it left the opening from which it was projected or thrown -can be estimated, so that the volcanic bombs must have left the crater -at a velocity of about 600 feet per second. - -On the 27th, in the evening, the lava streams ceased flowing, but the -dust and lapilli continued to fall during the 28th and the 29th. On -the 30th the detonations decreased and by the 1st of May the eruption -was entirely over. - -Palmieri calculated that the quantity of molten rock thrown out during -this eruption was sufficient to cover an area of about 1.8 square -miles to an average depth of about thirteen feet. - -As we can see from the above descriptions, the volcanic activity of -Vesuvius is characterized by long periods of rest followed by periods -of activity. The periods of rest are measured by years, and often by -centuries; the periods of activity by days or hours. - -But Vesuvius was not to have a long period of rest after its eruption -of 1872. On the contrary, shortly after the great disaster of -Martinique in 1906, it again became active, and on the 5th of April, -1906, began throwing large blocks of lava out of its central cone, and -on the next day began to throw out large streams of lava, which, on -April 7th, destroyed a village in the neighborhood. At the same time -rumbling sounds were heard, and violent earthquake shocks shattered -the windows of the houses. - -Professor Matteucci, the present director of the Vesuvius Observatory, -made the following report on April the 8th. - - "The eruption of Vesuvius has assumed extraordinary - proportions. Yesterday and last night the activity of the - crater was terrific, and is increasing. The neighborhood - of the observatory is completely covered with lava. - Incandescent rocks are being thrown up by the thousands, to - a height of 2,400 feet or even 3,000 feet, and falling back - form a large cone. Another stream of lava has appeared.... - The noise of the explosion and of the rocks striking - together is deafening. The ground is shaken by strong and - continuous seismic movements, and the seismic instruments - [instruments employed to record the time, direction, and - intensity of earthquake movements] threaten to break. It - will probably be necessary to abandon the observatory, - which is very much exposed to the shocks. The telegraph is - interrupted, and it is believed the Funicular railroad has - been destroyed." - -On April 9th Matteucci made the following report: - - "The explosive activity of Vesuvius, which was so great - yesterday, and was accompanied by very powerful electric - discharges, diminished yesterday afternoon. During the - night the expulsion of rocks ceased, but the emission of - sand increased, completely enveloping me and forming a - red mass from six to ten centimeters deep, which carried - desolation into these elevated regions. Masses of sand - gliding along the earth, created complete darkness until - seven o'clock. Several blocks of stone broke windows in the - observatory. Last night the earthquake shocks were stronger - and more frequent than yesterday, and displaced the seismic - apparatus. Yesterday afternoon and this morning, torrents - of sand fell." - -On April 10th Matteucci sent the following report: - - "Last night was calm, except for a few explosions of - considerable force from time to time. At four o'clock this - morning the explosions became more violent. The seismic - instruments recorded strong disturbances." - -The eruption of Vesuvius of 1906 was especially noted for the great -quantities of sand and ashes thrown out of the crater. The amount -of sand that fell on the roof of the market house at Monti Olivetto -was so great that the roof fell in. In this eruption there were some -six lava streams that poured down the mountain. The most formidable -of these was that which descended towards Torre Annunziata. Here it -stopped just short of the wall of the cemetery outside of the town. - -During this eruption of Vesuvius, as in previous eruptions, clouds of -volcanic dust collected in the air, shutting off the light of the sun. -Naples was in a state of semi-darkness. The roofs of the houses were -covered to a depth of several inches with an exceedingly fine reddish -dust. In some places this dust had drifted into heaps fully a yard in -depth. - - - - -CHAPTER VI - -OTHER VOLCANOES OF THE MEDITERRANEAN - - -The relative positions of the other volcanic mountains of the -Mediterranean Sea; i. e., Etna, Stromboli, and the volcanoes of the -Santorin group of the Grecian Archipelago, are shown in the map, Fig. -12. - -We will begin with the volcanic mountain of Etna, under which, -according to mythology, the angry gods had buried the rebellious -Typhoon. - -Etna is situated on the island of Sicily, immediately southwest of -Italy. It is a much larger mountain than Vesuvius, rising, as it -does, from a circular base about eighty-seven miles around, to a -height of 10,840 feet above the level of the Mediterranean. It forms -a conspicuous object when seen either from the Mediterranean, or from -distant parts of Italy. - -The height of Etna is so great that its slopes can be divided into -three distinct climatic zones or belts. The lowest of these lies -between the sea and a height of 2,500 feet. In this zone the mountain -slopes are covered with cultivated fields, olive groves, orchards, -and vineyards. The middle zone lies between 2,500 feet and 6,270 -feet. This zone is covered with forests of chestnuts, oaks, beeches, -and cork trees. The third and highest zone includes the rest of the -mountain, and may be called the desert zone, since it is a sterile -region, covered with huge blocks of lava and scoriae, and terminating, -in the higher portions, in a snow-covered plain, from which the -central cone rises. - -Etna is continually sending up columns of steam and sulphur vapor. -Every now and then it starts in eruption, throwing out large -quantities of lava either from the crater on its summit, or from -some of the 200 smaller cones or craters that occupy portions of its -slopes. On account, probably, of its height the eruptions are most -frequently on the sides. Etna affords a magnificent example of a huge -volcanic pile of the Vesuvian type, which has been slowly built up -by the gradual accumulation of materials that have escaped from its -craters. - -One of the most interesting features of the higher regions of Etna is -an immense chasm rent in a side of the cone near the summit, and known -as the Val del Bove. This chasm forms a vast amphitheater. - -The great force that removed such an immense mass of matter from -the cone could not have been the eroding power of water, since the -materials of the cone are too porous to permit streams of any size to -rush down the slopes. The force is most probably to be found in some -explosive eruption of the mountain, when a portion of the crater was -suddenly blown off, just as was done in Vesuvius when a large part of -the old crater of Somma was blown away. What is especially interesting -about the Val del Bove is the opportunity it affords for studying the -interior structure of the mountain, for it practically enables one to -enter to almost the heart of this great volcano. - -The Val del Bove has the shape of a great pit five miles in diameter. -It has almost vertical walls, the height of which varies with their -position. Those which reach highest up the mountain vary from 3,000 to -4,000 feet in height. - -Like Vesuvius, Etna has been split or fissured into great crevices -that have been filled with lava during the many eruptions of its -central crater. On hardening, these lava streams form what are known -as dikes. As the sides of the mountain are worn away by erosion, the -dikes, being harder than the rest of the cone, project from its sides -like huge walls. An excellent opportunity for seeing them is afforded -in the walls of the Val del Bove. - -Sir Charles Lyell, the English geologist, who has carefully studied -Mt. Etna, asserts that this mountain began to be formed during a -geological period known as the Tertiary Age, through a crater that -opened on the floor of the Mediterranean Sea. The material thus -thrown out, collected around the crater and produced a mountainous -pile that gradually emerged above the level of the sea, and on fresh -materials continuing to be thrown out, at length reached its present -height. It would appear that at some former time in its history, there -were two vents near the top of the mountain, the second crater being -formed immediately under the Val del Bove. Soon, however, the second -and lower crater was closed, the upper one alone remaining active. -The mountain, therefore, continued to be slowly raised in the air by -the materials brought out through this opening. Then came the great -explosive eruption during which the side of the mountain was blown off -to form the great chasm of the Val del Bove. - -Because of its almost constant activity, Mt. Etna must have been -well known to the ancients, who described some of its most violent -eruptions. The following brief notes concerning these eruptions have -been taken from Lyell. - -According to Diodorus Siculus, an eruption that occurred before the -Trojan war, caused the people living in districts near the mountain to -seek new homes. Thucididies, the Greek historian, states that in the -sixth year of the Peloponnesian war, which would be about the spring -of 425 B. C., a lava stream caused great destruction in the -neighborhood of Campania, this being the third eruption that had -occurred in Sicily since it had been settled by the Greeks. - -Seneca, during the first century of the Christian Era, calls the -attention of Lucullus to the fact that during his time Mt. Etna had -lost so much of its height that it could no longer be seen by boatmen -from points at which it had before been readily visible. - -But passing by these very early eruptions of Etna we come to the great -eruption of 1669. This eruption was preceded by an earthquake that -destroyed many houses in a town situated in the lower part of the -forest zone, about twenty-five miles below the summit of the mountain, -and ten miles from the sea at Catania. During this eruption two deep -fissures were opened near Catania. From these such quantities of sand -and scoriae were thrown out, that, in the course of three or four -months, a double cone was formed 450 feet high, which is now known as -Monte Rosso. But what was most curious was the sudden opening, with -a loud crash, of a fissure six feet broad reaching down to unknown -depths that extended in a somewhat crooked course to within a mile -of the summit of Etna. This great fissure was twelve miles in length -and emitted a most vivid light. Five other parallel fissures of -considerable length opened, one after another, throwing out vapor, -and emitting bellowing sounds which were heard at a distance of forty -miles. These fissures were afterwards filled with molten rock, and in -this manner were formed the long dikes of porphyry and other rocks -that are seen to be passing through some of the older lavas of Mt. -Etna. - -[Illustration: FIG. 14. MT. ETNA _From Map of State and -Government_] - -The great lava streams which flowed down the side of the mountain -during this eruption, destroyed fourteen towns and villages, and -at length reached Catania. A great wall had been raised around this -city to prevent the lava from entering it. The molten rock, however, -accumulated, until it rose to the top of the wall, which was sixty -feet high, and then pouring over it in a fiery cascade, overwhelmed -part of the city. It is said that during the first part of its -journey, the lava streams moved over thirteen miles in twenty days, -or at the rate of 162 feet an hour. Beyond this, after the lava had -thickened by cooling, it had a velocity of only twenty-two feet per -hour. - -Fig. 14 represents a plan of Mt. Etna reduced from a map by the -Italian Government. During the eruption of 1865, a rent was made in -the mountain extending from Mount Frumento (B in the preceding map) -for one and one-half miles, and six cones from 300 to 350 feet in -height were formed along the fissure. - -During the eruption of 1874, great fissures three miles in length were -formed in the mountain. - -There exists on the slopes of Mt. Etna vast subterranean grottoes -formed by the sudden conversion into steam of great quantities of -water that were overwhelmed by the molten mass. These immense volumes -of steam produced enormous bubbles in the molten lava. When the lava -hardened irregular grottoes were left. Lyell describes one of these as -follows: - - "Near Nicolosi, not far from Monte Rosso, one of these - great openings may be seen, called the _Fossa della - Palomba_, 625 feet in circumference at its mouth and - seventy-eight deep. After reaching the bottom of this, we - enter another dark cavity, and then others in succession, - sometimes descending precipices by means of ladders. At - length, the vaults terminate in a great gallery ninety feet - long, and from fifteen to fifty broad, beyond which there - is still a passage, never yet explored, so that the extent - of these caverns remains unknown. The walls and roofs of - these great vaults are composed of rough bristling scoriae - of the most fantastic forms." - -Besides the eruptions mentioned there have been many others, such as -those of 1811, 1819, and 1852. The last of these was greater than any -eruption except that of 1669. It began in August, 1852, and continued -until May, 1853, and was remarkable for the immense quantity of lava -thrown out. - -[Illustration: FIG. 15. STROMBOLI, VIEWED FROM THE NORTHWEST, -APRIL, 1874] - -We come now to the volcano of Stromboli. Stromboli, one of the Lipari -islands, is situated about sixteen miles west of the Straits of -Messina. Its general appearance is shown in Fig. 15. The form of the -mountain is that of an irregular four-sided pyramid, which rises about -3,090 feet above the level of the Mediterranean, and stands on the -bottom of the sea in water about 3,000 feet deep. - -If you carefully examine the appearance of Stromboli, as shown in the -preceding figure, you will notice that the flat cloud which hangs over -the island is made up of a number of globular masses of vapor, formed -during the peculiar action of the volcano. - -When examined by night Stromboli presents a still more curious -appearance. Since the mountain stands alone, its height permits it to -be seen readily at sea for distances of at least a hundred miles. At -night a curious glow of red light may be seen on the lower surfaces of -the cloud. This light is not continuous, but increases in intensity -from a faint glow to a fairly bright red light, then gradually -decreases, and finally dies away completely. After awhile the light -again appears, again gradually decreases, and disappears, and this -continues until the rising sun prevents the red glow from being any -longer visible. Stromboli, therefore, acts not unlike the flashing -lighthouses so common on the sea coasts of all parts of the world. -Indeed, it is actually used by sailors in the Mediterranean for the -purpose of showing them their direction. For this reason Stromboli is -commonly called "The Lighthouse of the Mediterranean." - -As Judd remarks, from whom much of the information concerning some of -the volcanic districts of the Mediterranean has been obtained, the -flashing light of Stromboli differs from that of the ordinary flashing -light in two important respects; viz., in the intervals that elapse -between the successive flashes, and in the intensity of the light -emitted. As you know, it is necessary that the different lighthouses -placed near one another on a coast must have their lights of such a -nature that they can be readily distinguished. In order to do this, -the flashing light has been devised. In flashing lighthouses, the -lights only appear at intervals, one lighthouse being distinguished -from another in its neighborhood by the intervals between successive -flashes, or, sometimes, indeed, by the color of some of the flashes. -Now, in the case of Stromboli, the intervals between the successive -glowings of the red lights are very irregular, varying between one and -twenty flashes per second. Moreover, the intensity of the light also -varies greatly from time to time. - -You naturally inquire as to the cause of these flashes of light that -are emitted by Stromboli. If, as Judd suggests, you should climb to -the summit of the mountain, during the daytime, and look down the -inside of the crater, you could see its black slag bottom crossed by -many cracks and fissures. From most of the smaller fissures the vapor -of water is quietly escaping. This vapor rises in the air in which it -soon disappears. There are, however, larger cracks on the bottom of -the crater from which, at more or less regular intervals, masses of -steam are emitted with loud snorting puffs not unlike those produced -by a locomotive. From some of the openings molten matter is seen -slowly oozing out, collecting in parts of the crater and moving up and -down in a heaving motion. Every now and then a bubble is formed on -the surface of this liquid. The bubble swells to a gigantic size, and -suddenly bursts. The steam it contained escapes, carrying fragments of -scum which are thrown high into the air. The masses of steam, formed -below the surface of the sticky, boiling, lava, in endeavoring to -escape, force their way through the mass, blow huge bubbles, which, -on bursting, produce the roaring sounds that are heard, and throwing -great columns of vapor in the air, produce the rounded masses of -clouds you can see floating high up in the air over the mountain. At -the same time the scum is partially removed from the red hot surface, -its light illumines the lower surface of the overhanging cloud, which -flings it back again to the earth. With the bursting of each bubble, -and the clearing of the scum from the surface of the red hot mass, -the light begins, increases in intensity, and then as the scum again -begins to collect on the surface, decreases, and finally disappears, -and not until the bursting of the next bubble is it again visible. - -But let us make a study of some of the peculiarities of Vulcano, -another of the Lipari islands, which lies north of Sicily. - -Vulcano affords a curious example of a volcano that has been harnessed -by man, or made to do work for him. All volcanoes bring from inside -of the earth different kinds of chemical substances, in the form of -vapors, gases, or molten materials. Now, these materials acting on -one another, produce chemical substances some of which, such as sal -ammoniac, sulphur, and boracic acid, possess commercial value. This is -especially true in the case of Vulcano, and since the eruptions are -not generally violent, a chemical works has actually been erected by -a Scotch firm on the side of the mountain, where the materials are -collected from the crevices. - -This effort to harness a volcano was for a time so successful that -the same people contemplated the building of great leaden chambers -over the principal fissure at the bottom of the crater, so that the -large volumes of ejected vapors might be condensed and collected. But -Vulcano, like all other volcanoes, could not be relied on continually -to keep the peace. One day it suddenly burst forth more fiercely than -usual, so that the workmen were compelled to abandon the factory and -fly down the mountain for their lives, but not, however, before some -of them were severely injured by the explosions. - -Vulcano is an instance of a volcano in an almost exhausted or dormant -condition. It has had, however, many eruptions during the past few -centuries, some of which have been very violent, for example, that of -1783, and that of 1786. - -There still remains to be considered the volcanic region of the -Santorin group of the Grecian Archipelago. The island of Santorin -or Thera, is the southernmost of the Cyclades. It is an exceedingly -curious island, being a submerged volcano, with most of the top of the -crater remaining above the waters, so that the entire island has the -shape of an irregular circle or crescent broken at several points. -Its formation is, probably, due to the gradual sinking of a volcanic -mountain until its crater has been almost completely submerged, only -the higher parts of the edges of the crater being left above the -surface of the waters. Suppose, for example, a mountain like Vesuvius -at the time the crater Somma existed, was sunk below the level of the -Mediterranean until only the highest parts of the crater remained -above the waters. If, now, one or more volcanic eruptions occurred, -producing craters or volcanic islands inside the submerged rim, you -would have a condition of affairs seen in the island of Santorin. - - - - -CHAPTER VII - -ORIZABA, POPOCATEPETL, IXTACCIHUATL, AND OTHER VOLCANOES OF MEXICO - - -While some of the volcanoes of Mexico are still in an active -condition, most of them are either only slightly active or are dormant -or extinct. Humboldt, the celebrated traveller and geographer, states -that there are only four active volcanic mountains in Mexico; namely, -Popocatepetl, Tuxtula, Colima, and Jorullo. But there are many others, -among which may be mentioned Orizaba, Ixtaccihuatl, Xinantecatl, -Tuxtula, Cofre de Perote, and Colima. - -Of course, you can understand that, since extinct volcanoes may at any -time become active, in parts of the world where communication with the -interior is not good, many volcanic mountains that have been regarded -as extinct may have broken out temporarily, during historical times, -without their eruptions having been recorded. - -It was at one time thought that Popocatepetl was the highest mountain -in North America. More recent measurements, however, have shown that -there are at least three other mountains in this part of the world, -that are much higher. One of these is the active volcano of Orizaba -that we will now briefly describe. - -[Illustration: FIG. 16. MEXICO AND CENTRAL AMERICA] - -Orizaba is situated in the north central part of Mexico, about -seventy-five miles west of Vera Cruz. Its ancient Aztec name was -Cittaltepetl, or _Star Mountain_. The height of the mountain is -18,200 feet. Like all high tropical mountains whose summits are -snow-clad, one would pass through the same changes in climate, in -going from its base to its summit, as in going along the earth's -surface from the equator to the poles. Near the base of the mountain -will be found a tropical climate, above that a temperate climate, -while in still higher regions, the climate of the Arctic region. - -According to Russell, from whose work on the volcanoes of North -America much of the information concerning the volcanoes of Mexico -and Central America has been condensed, Orizaba has three craters on -its summit. The last recorded eruption took place about the middle of -the Eighteenth Century. The mountain is now in a dormant or extinct -condition, as may be seen from the fact that its three craters are for -the greater part filled with snow. - -Orizaba, like Etna, and many other volcanoes, has deep fissures -extending through its sides. Through these, lava streams have flowed -during times when it was active. There are also found on the slopes -of this mountain many cones of a type known as _parasitic cones_. -These cones are not caused by materials that have been brought to the -surface during an eruption, but have been formed by the steam passing -through lava streams that have come out of the crater during other -eruptions. - -Popocatepetl, or, as the word means, _The Smoking Mountain_, is the -second highest mountain in Mexico. According to recent measurements -made by the Mexican Government, its height is 17,876 feet. -Popocatepetl is situated on the edge of the great plateau of Mexico, -forty miles southeast of the City of Mexico. It is a conical mountain, -and is a magnificent object when seen from the City of Mexico, rising, -as it does, fully 10,000 feet from the elevation of the city, while on -the east it towers for nearly 18,000 feet above the level of the sea. -This splendid mountain is poetically described by Russell: - - "Seen from the basal plains, it sweeps up in one grand - curve to nearly its full height,--a collossus of three and - a quarter miles in elevation, white with everlasting frost - on its summit, and bathed in the green of palms, bananas, - oranges, and mangoes, at its base. Evergreen oaks and - pines encircle its middle height, and above them, before - the ice itself is reached, occur broad areas of loose sand - into which the lavas have been changed by weathering. Soft - wreaths of sulphurous vapor may at times be seen curling - over the crest of the summit crater,--gentle reminders that - the days of volcanic activity are not yet necessarily over." - -Popocatepetl takes its name, _The Smoking Mountain_ from the fact that -gases and vapor are continually being emitted from its summit crater. -It has a conical peak with a depression or crater on its summit. -The bottom of the crater is crossed by fissures from which small -quantities of steam escape, not, however, sufficient to melt all the -snow which covers the slopes of the mountain to a depth of from eight -to ten feet. A small lake of hot water has collected in the crater -from the water derived from the melting snow. This water, sinking -through the porous materials in the cone, is the source of a great -number of large hot springs that occur around the base of the mountain. - -Reclus states that the first to climb to the top of Popocatepetl was -one of Cortez' officers, 1519. - -Another snow-capped volcano, which rising from the plain of Mexico is -in clear view of the city, is Ixtaccihuatl (Ets-tak'-se-wat-el), or as -the word means in the ancient Aztec, _The White Woman_. This mountain, -as measured by Heilprin, is 16,960 feet in height. Ixtaccihuatl is -now in so dormant a condition that many who have climbed to the top -assert that it is not a volcano at all, since they find no crater on -its summit. Nor are there any signs of volcanic heat, the summit being -snow clad during summer. The conical form of the mountain, however, -and the fact that the entire mountain is formed of volcanic rocks, -show beyond doubt that it is an extinct volcano, whose crater has most -probably been completely filled in by the washing away of its sides. - -Xinantecatl is another extinct volcanic mountain situated about forty -miles southwest of the City of Mexico. It is about 16,500 feet high. -Its name means in the ancient Aztec language, _The Naked Lord_. It is -also sometimes known as the Nevado de Toluca, or _The Snow of Toluca_. -On the top of the peak are two craters filled with lakes of fresh -water. Russell states that the larger of these lakes is about thirty -feet in depth and contain a peculiar species of fish. - -Tuxtula is another volcano of Mexico, situated on the western coast -of the Gulf of Mexico, about eighty miles southeast of Vera Cruz. It -was an active volcano in 1664, when it threw out molten lava. It then -became dormant until March, 1793, when its long rest was broken by one -of the grandest explosive eruptions of modern times. This eruption -rivalled in energy the great explosive eruption which blew off the -summit of Coseguina, in Central America, in 1835. As is common in the -case of explosive eruptions, volcanic dust and scoriae were blown high -into the air, and, being carried by the winds, fell on the roofs of -houses and on the land at a distance of 150 miles. - -There have been a number of less violent eruptions of Tuxtula since -1835. Tuxtula is a comparatively low mountain, being only 4,960 feet -high, because much of the mountain was blown away by the eruption of -1793. - -As Russell points out, it is not safe to infer that because an eroded -mountain is not lofty it cannot be young or energetic, since the very -energy of some of its eruptions may, as in the case of Tuxtula, blow -away a large part of the mountain. A low mountain, with an unusually -large crater, generally means a mountain that has been visited by a -great explosive eruption. - -Another extinct volcano known as the Cofre de Perote is situated on -the eastern coast of Mexico, east of Ixtaccihuatl, about thirty miles -north of Orizaba. It takes its name Cofre de Perote which means the -Coffin of Perote, from its peculiar box-like shape. It was called in -the Aztec language "Nauhcampatepetl," or the _Four-Ridged Mountain_. -Cofre de Perote is in a dormant or extinct condition. - -We will conclude this brief description of the volcanoes of Mexico -with the volcano of Colima, a mountain about 5,500 feet high situated -on the western coast of Mexico. - -Colima has been active of recent years, eruptions having occurred in -1869, 1872, 1873, and 1885. During these eruptions lava escaped from -lateral openings in the sides of the mountain, these openings being -termed by the natives the _Sons of Colima_. - - - - -CHAPTER VIII - -COSEGUINA AND OTHER VOLCANOES OF CENTRAL AMERICA - - -Central America has a great number of volcanoes extending along nearly -all its western coast, or on the Pacific side of the country. - -Central America consists of a high plain or table-land sloping gently -towards the northeast, but terminating abruptly on the southwest. In -the opinion of geologists this table-land consists of the surface of a -huge tilted block of the earth's crust, or, perhaps, more probably, of -a series of such blocks, that are limited on the southwest by a narrow -belt of intersecting fractures. It is in these fractures that scores -of volcanoes are situated, together with active craters, solfataras, -and hot springs. The volcanoes are mainly of the Vesuvian type. There -are so many volcanoes in this part of the world that it will be -possible to describe but a few of them. - -We will begin with the volcano of Coseguina, situated on the Pacific -coast of Nicaragua. Its appearance is that of a conical mountain with -the top cut off, and suggests that it is most probably an explosive -volcano which has had the top blown away during some of its great -eruptions. - -Coseguina is celebrated by reason of its tremendous eruption of 1835. -Before the still more tremendous explosive eruption of Krakatoa in -1883, described in the first two chapters of this book, Coseguina -shared with Sombawa, on the island of Sumatra, as being the foremost -of explosive volcanoes. - -It had been estimated that before its eruption of 1835, Coseguina had -a height of perhaps 10,000 feet, but so much of it was blown away by -this eruption that it now is a little less than 4,000 feet. - -The following description of the great eruption of Coseguina in 1835 -has been condensed from an account prepared by Squier, published in -1850. - -You will note in reading this brief account how closely many of the -phenomena resemble those that occurred during the eruption of Krakatoa -in 1833. - -The eruption of Coseguina was heralded on the morning of January 20th, -1835, by several loud explosions that were heard for a distance of -some 300 miles around the crater of the volcano. Then followed an ink -black cloud formed directly over the mountain, which gradually spread -on all sides shutting off the light of the sun, except for a sickly -yellowish light. Fine sand was thrown from this cloud, which made it -both difficult and painful to breathe. For two whole days the cloud -continued to grow denser, the explosions louder and more frequent, -and the rain of sand thicker. On the third day the explosions were -strongest and the darkness greatest. - -The amount of sand that fell from the cloud was so great that people -left their houses, fearing the roofs would be crushed in by the great -weight. This sand fell in large quantities over an area more than -1,500 miles in diameter, or, quoting the language of Squier: - - "The noise of the explosions was heard nearly as far" - (1,500 miles). "And the Superintendent of Belize, eight - hundred miles distant, mustered his troops, under the - impression that there was a naval action off the harbor. - All nature seemed overawed; the birds deserted the - air, and the wild beasts their fastnesses, crouching, - terror-stricken and harmless, in the dwellings of men. - The people for a hundred leagues grouped, dumb with - terror, amidst the thick darkness, bearing crosses on - their shoulders and stones on their heads in penitential - abasement and dismay. Many believed that the day of doom - had come, and crowded in the tottering churches, where, in - the pauses of the explosions, the voices of the priests - were heard in solemn invocation to Heaven. The brightest - lights were invisible at the distance of a few feet; and - to heighten the terror of the scene, occasional lightnings - traversed the darkness, shedding a lurid glare over the - earth. This continued for forty-three hours, and then - gradually passed away." - -It appears that the eruption of Coseguina was followed by violent -earthquake shocks and other evidences of volcanic energy over extended -regions. For example, there were fearful earthquakes along the Andes, -the worst of which occurred on February 20th, and continued at the -rate of three or four a day up to March 6th, and, less frequently, -to March 17th. It was during one of these earthquakes that the city -of Concepcion, Chile, was so completely destroyed, that but a single -house remained. - -The same brilliant sunsets and sunrises occurred in different parts -of the world after the eruption of Coseguina, due to the presence of -large quantities of volcanic dust that followed the great eruption of -Krakatoa. - -The cause of this great explosive eruption of Coseguina was most -probably the same as that which is believed to have caused the -eruption of Krakatoa, namely, a large volume of water suddenly gaining -access to a mass of liquid lava. - -Volcan del Fuego is another of the many volcanoes of Central America. -It is situated as one of a group of volcanoes on the highest summit -of the Isthmus. This volcanic mountain has a regular cone with -regular slopes on all sides, except on the north, where a table-like -projection, about 1,000 feet below the summit, is all that remains of -a vast cone, the summit of which was blown away, according to Russell, -in prehistoric times, just as was the crater of Somma on Vesuvius. - -There have been in Central America, since the time of the Spanish -conquest, some fifty volcanic eruptions sufficiently great to have -been recorded. Some idea of the activity of Fuego during this time -may be had from the fact that of all these eruptions some twenty were -those of Fuego. At the present time, however, the volcano is dormant -and apparently almost extinct. - -The recorded eruptions of Fuego are nearly all of the explosive type. -Among the most violent were those that occurred during 1526, 1541, -and 1581. During 1582, 1585, and 1586, there were eruptions nearly -every month, the most terrible being near Christmas day in 1586. Other -memorable eruptions occurred in 1614, 1623, 1686, and 1705, and at -other dates down to August 17th, 1860, from which date to the present -time the volcano has been quiet. - -We will conclude this brief description of the volcanoes of Central -America with that of Volcan de Agua, or, as the word means, _The Water -Volcano_. It is situated in Guatemala near the coast, and is one of -the mountains that occupies the plateau on which Fuego is situated. - -The Volcan de Agua is one of the most remarkable volcanoes in Central -America, standing, as it does, nearly alone, and rising to an -elevation of 3,350 metres (10,988 ft.), above the level of the sea. It -has been extinct for a long time. - -It has been supposed by some, from its name, that this is a volcano -that throws out water. Others believe that the name comes from the -water produced by the melting of the snow that is collected on the -sides of the mountain. Now there almost always escapes from the -craters of volcanoes during violent eruptions immense quantities of -water vapor, which, condensing, fall as vast showers of rain that -often deluge the surrounding country. In snow-clad mountains, the -escape of lava is often attended by floods caused by the rapid melting -of the snow. The water volcano did not, however, take its name from -either of these facts, but rather because at the time of the Spanish -invasion, the crater of the mountain was occupied by a large lake, and -that during an earthquake in 1541 the wall of the crater was broken, -when the lake was poured as an immense stream of water down the side -of the mountain, overwhelming a village which was situated on this -slope. That this was the correct origin of the same may be seen from -the fact that the crater at the present time still shows the remains -of its former lake basin, and that on the sides of the broken rim an -immense ravine can be seen through which the water poured down on the -village below. - -Daubeny describes this volcano as follows: - - "The Volcan de Agua (Water-Volcano) is of enormous height, - being covered with eternal snow, in the latitude of 14 deg. - Captain Basil Hall estimates it at more than 14,000 feet, - but a recent traveller states it at 12,600. It has the form - of a blunted cone clothed with perpetual verdure to its - summit. The crater is from forty to sixty yards in depth, - and about 150 in diameter,--the sides and bottom strewed - with masses of rock, apparently showing the effects of - boiling water or of fire. - - "By a deluge of water from this volcano in 1527, the - original city of Guatemala was overwhelmed; and the next - built, called the Old City, _La Antiqua_, was ruined by an - earthquake in 1773. The present capital is situated at a - distance of eight leagues from the mountain." - -Another volcano in this part of the country is described by Daubeny as -follows: - - "Massaya, near the lake of that name, was one of the most - active vents at the time of the first discovery of the - country. Its flames were visible twenty-five miles off. Its - crater was only twenty or thirty paces in diameter; but - the melted lava 'seethed and rolled in waves as high as - towers.' A story is told of a Dominican who imagined the - fluid lava was melted gold, and descended into the crater - with an iron ladle to carry some away; but the ladle, it is - said, melted, and the monk escaped with difficulty." - - - - -CHAPTER IX - -THE VOLCANIC MOUNTAINS OF SOUTH AMERICA - - -The volcanoes of South America are limited to the Andes Mountain -System that stretches like a huge wall along the entire western side -of the continent. The names of the more important of these volcanoes -are marked on the map of South America, shown in Fig. 17. As will be -seen, this huge mountain wall reaches from Patagonia on the south to -the Isthmus of Panama on the north. The arrangement of the volcanoes -in South America is of the linear type. The craters follow one another -in more or less straight lines, or are situated along the lines of -great fissures that lie near the ocean. You must not, however, suppose -that there is a continuous chain of active volcanic mountains from the -Isthmus of Panama to the southern part of the continent. According to -Lyell, from lat. 2 deg. N., or from the north of Quito, to lat. 43 deg. S. or -south of Chile, a total distance including 45 deg. of latitude, there is a -succession of districts with active and extinct volcanoes, or at least -with volcanoes that have been quiet during the last three centuries. - -[Illustration: FIG. 17. SOUTH AMERICA] - -Lyell traces the volcanoes of South America as follows: - - "The principal line of active vents which have been seen in - eruption in the Andes extends from lat. 43 deg. 28' S., ... to - lat. 30 deg. S.; to these thirteen degrees of latitude succeed - more than eight degrees, in which no recent volcanic - eruptions have been observed. We then come to the volcanoes - of Bolivia and Peru, extending six degrees from S. to N., - or from lat. 21 deg. S. to lat. 15 deg. S. Between the Peruvian - volcanoes and those of Quito another space intervenes of no - less than fourteen degrees of latitude, in which there is - said to be but few active volcanoes as far as is yet known. - The volcanoes of Quito then succeed, beginning about 100 - geographical miles south of the equator, and continuing - for about 150 miles north of it, when there occurs another - undisturbed region of more than six degrees of latitude, - after which we arrive at the volcanoes of Guatemala, or - Central America, north of the Isthmus of Panama." - -Of course, you must not understand that there are no extinct volcanoes -in these gaps. On the contrary, according to Daubeny, we find, -beginning on the north in the United States of Colombia, the lofty -volcano of Tolima. According to Daubeny's book published in 1848, -Tolima was then constantly emitting steam and sulphur gases from its -summit. Tolima is situated in the easternmost of the three mountain -ranges that extend through this section of the country. It is, -therefore, at a comparatively great distance from the ocean. Tolima -was in eruption in 1595. It again burst out in 1826. - -Coming now to Ecuador we find that this, the smallest of the South -American Republics, contains numerous great volcanic mountains. - -Some of the principal volcanic mountains are Chimborazo, 20,498 feet -above the sea; Antisana, 18,880 feet; Cotopaxi, 19,660 feet; Pichincha -(17,644 feet in 1848, Daubeny), El Altar, 16,383 feet. - -These all lie in South America on the plateau of Quito. As Baron -Alexander von Humboldt has pointed out, the volcanic mountains of -Quito are arranged in two parallel chains that extend side by side -for a distance of over 500 miles north into the State of Colombia, -including between them the high plateaus of Quito and Lacumbia. -According to Whymper, however, who has recently studied this part of -South America, there is a succession of basins between the mountains, -but there is no such thing as a single valley in the interior of -Ecuador. The extinct volcanoes of Cayamba, Antisana, and Chimborazo -are the most important. On all three mountains there are old lava -streams on their sides. Although no craters can be seen on their -summits, yet it is almost certain they once had craters. There is -plenty of room on the summit of Antisana for a cone as great as that -of Cotopaxi. Whymper is of the opinion that the snow domes that form -the summit of Chimborazo were at one time two of the highest points of -the rim of the old crater. - -Nearly due south of Quito is the great volcanic cone of El Altar. -Like all the peaks of this high plateau, El Altar rises to a great -height above the sea, being at the present time 16,383 feet above the -sea. This mountain has an enormous crater that appears to be dormant -or extinct, and is covered with snow. According to the traditions of -Indians, El Altar, or, as they call it, _Capac Urcu_ or _The Chief_, -was the highest mountain near the equator, being much higher than -Chimborazo. But during a prodigious eruption that occurred before the -discovery of America, and continued uninterruptedly for eight years, -the height of the mountain was considerably reduced. According to -Boussingault, the fragments of the cone of this celebrated mountain -are now spread for great distances around the mountain on the -surrounding lowlands. - -Pichincha in Ecuador, an extinct volcano, is situated almost -immediately on the equator. It has a height as measured by Whymper by -the barometer, of 15,918 feet above the Pacific. The summit is covered -by blocks of pumice. Several species of lichens are found at this -elevation. According to Daubeny, Pichincha was extinct prior to 1539, -when it became active. There were also eruptions in 1577, 1587, and -1668. It was also in activity during 1831. - -Cayamba, another volcanic mountain of Ecuador, lies to the east of -Pichincha, a short distance north of the equator. Its height is 19,186 -feet. It is nearly extinct. - -Cotopaxi, 19,680 feet, is another volcanic mountain of the high -plateau of Quito. Cotopaxi is still active. Its slopes are covered -with snow down to a height of about 14,800 feet. Between the lower -edge of this snow line and the lower slopes of the mountain, there -lies a zone of naked rock. - -According to Whymper, the eruption of Cotopaxi, in 1877, was preceded -by an unusual degree of activity in the earlier parts of the year. -This, however, did not cause any alarm until June 25th, 1877, when, -shortly after midday, an eruption, attended by tremendous subterranean -roars, began, and an immense black column shot up into the air for -about twice the height of the cone. This eruption was clearly visible -at Quito, for the wind blew the ashes towards the Pacific. At this -time the summit had not changed its appearance, but towards 6:30 -A. M., on the next day, another enormous column of ashes -rose from the crater. The ashes and cinders were first carried due -north by the winds, and then, spreading out in all directions, were -subsequently distributed through the air all over the country. At -Quito, as early as 8 A. M., the sky assumed the appearance it -generally has at twilight, and the darkness increased until midday, -when it became as dark as at midnight. Indeed, it was so dark that one -could not see his hand before his face. - -During this eruption, as is very common in the eruptions of the -snow-clad mountains of South America, a flood of water, due to the -rapid melting of the snow and ice on the summit, rushed down the -mountain slopes at 10 o'clock A. M., on the 26th of the -month, almost immediately after the appearance of a stream of lava -that began to flow down the mountain. In a few moments the mountain -was completely shut off from view by immense columns of steam and -smoke. At first, a low, moaning sound was heard, which rapidly -increased to a roar, when a deluge of mud, mingled with huge blocks of -ice and stones, swept down the mountain, leaving a desert in its path. -It is estimated that at some places this stream moved with a velocity -of fifty miles per hour. - -The general appearance of Cotopaxi is shown in the accompanying -reproduction from the painting by Frederick E. Church in the Lenox -Library, New York. - -According to Whymper, who made an ascent of Cotopaxi in 1880, the -crater on the summit has the form of an immense amphitheatre, 2,300 -feet across from north to south, and 1,650 feet from east to west. -Its crest is irregular and notched. The crater is surrounded by -perpendicular cliffs. The western side of the volcano is irregular. -Barometric measurements gave the height of this volcano at 19,498 -feet. Its height as taken by La Condamine, during the early parts of -the last century, was 19,605 feet, so that, according to Whymper, -assuming as would seem probable, that this difference in height has -not all been due to errors in measurements, the volcano has grown or -increased in height during the last century and a half. - -Chimborazo, 20,498 feet, is another lofty mountain on the plateau of -Quito. This volcano is situated in lat. 1 deg. 30' S., and is not at the -present time in an active condition. It is, however, formed entirely -of volcanic material. Its upper portions are covered with a layer of -snow to a level of some 2,600 feet below the summit. - -[Illustration: COTOPAXI _From a Painting by Frederick E. -Church in the Lenox Collection of the New York Public Library. By -Permission_] - -Chimborazo has an enormous volcanic summit, which, when seen from the -Pacific, when the air is especially clear after the long rains of -winter, is a most splendid sight. Whymper, who ascended the mountain, -says: - - "When the transparency of the air is increased and its - enormous circular summit is seen projected upon the deep - azure of blue of the Equatorial sky, it represents a - magnificent sight. The great rarity of the air through - which the top of the Andes is seen adds much to the - splendor." - -Whymper says, that as far as records are concerned, there have been no -eruptions of Chimborazo, which has apparently been an extinct volcano -for many years. Its crater has been completely buried by a thick cap -of ice on its summit, while what lava streams exist on the mountain -are either covered by large glaciers, or have been removed by erosion, -or hidden by vegetation. - -Chimborazo possesses less of the conical outline than Cotopaxi. There -are steep cliffs towards the summit that have been named by Whymper -"the northern and southern walls." They seem to him to have been -formed by the violent upheavals of the explosive eruptions that have -blown away portions of the cone. - -There are other volcanoes in this district, but the above are all we -have space for describing. - -According to Lyell, the volcano of Rancagua, in Chile, lat. 34 deg. 15' -S., is continually throwing up ashes and vapors like Stromboli. -Indeed, a year seldom passes in Chile without some earthquake shocks. -Of these shocks those which came from the side nearest the sea are -most violent. The town of Copiapo was laid waste by these shocks -during the years 1773, 1796, and 1819, in both instances after -intervals of twenty-three years. - -Since the volcanic mountains of South America are snow-covered the -occurrences of volcanic eruptions are apt to be attended by great -floods caused by the rapid melting of the snow, as well as sometimes -by the breaking of huge subterranean cavities that are filled with -water. - -According to Lyell, the volcanoes of Peru rise from a plateau from -17,000 to 20,000 feet above the sea. One of the principal volcanoes -of Peru is Arequipa, whose summit is 18,877 feet above the level of -the sea. The mountain takes its name from the city of Arequipa, which -is situated not far from its base. It is an active volcano. Another -volcano, Viejo, is found in lat. 16 deg. 55' S. - -According to Lyell, there are active vents extending through Chile to -the island of Chiloe to lat. 30 deg. N. - -Aconcagua, west of Valparaiso, in lat. 32 deg. 39' S., 23,000 feet in -height, the highest mountain in South America, is still in an active -condition. According to Scrope, when the city of Mendoza was destroyed -by an earthquake, that killed 10,000 people, in March, 1861, it is -probable that Aconcagua was in eruption. - -There are many other active volcanoes in Chile, extending as far south -as the volcanoes of Patagonia, north of the Straits of Magellan as -well as others of Tierra del Fuego. - - - - -CHAPTER X - -VOLCANOES OF THE UNITED STATES - - -For some readers this may be a surprising chapter heading, for it is a -general impression that there are no volcanoes in the United States. -It is true that practically all of the volcanoes of this country are -dormant or extinct. They have, however, at one time been exceedingly -active, and, if reports are correct, some of them were active during -comparatively recent times. - -Nearly all of the volcanoes of the United States lie west of the -meridian of Denver. These volcanoes belong to two distinct types, -either the Vesuvian type with built up cones, or the plateau or -fissure type already referred to. - -The following brief description of the volcanoes of the United States -has been collated, for the greater part, from Wallace's excellent book -on the volcanoes of North America. - -Crossing the United States on the Southern Pacific Railroad one's -attention is caught, in Arizona, by a magnificent group of mountains -known as the San Francisco Mountains. The highest peak of these -mountains reaches 12,562 feet above the level of the sea, and 5,700 -feet above the surface of the plateau on which the mountains stand. - -[Illustration: FIG. 18. THE UNITED STATES] - -According to G. K. Gilbert, the San Francisco Mountain group is formed -of a variety of lava known as trachyte, that is of comparatively -recent ejection, possibly of a geological age called the Tertiary. The -lava forming the mountains escaped through a number of crater cones, -some of which can still be seen in the neighborhood. Some of these -craters are now in almost as perfect a condition as the day they were -formed. Indeed, to one looking at them from a neighboring elevation, -they appear so fresh, and so little affected by the climate, that one -might almost believe that the lava had just flowed out of the craters, -and has not yet hardened. Nevertheless, geologists are sure they have -been formed long before man appeared on the earth. In one of these -craters a lake of fresh water has collected. - -Another extinct volcano of the United States is Mt. Taylor in New -Mexico, nearly east of the San Francisco Mountains. This mountain -rises from the surface of a high table-land, or, as it is called -in this part of the world, a _mesa_. The surface of the plateau is -covered with a thick lava stream from which Mt. Taylor rises to -a height of 11,390 feet above the level of the ocean. This mesa, -or table-land, is forty-seven miles in length from northwest to -southeast, and about twenty-three miles in breadth. Its general -elevation is about 8,200 feet. The plateau rises about 2,000 feet -above the surface of the level land that surrounds it. All these -2,000 feet have been removed by erosion. The table-land from which -Mt. Taylor rises has not been eroded by the action of the rain, -rivers, and other weathering agencies like the surface of the country -surrounding it, because of a covering of lava that has been spread -over its surface to a depth of about 300 feet. - -Mt. Taylor is formed almost entirely of lava that has escaped through -a single opening and has built up a high cone around it. The volcano -is now quite extinct, so that the original form of the mountain has -been greatly changed by erosion. - -You will remember, when we were discussing the general subject of -volcanoes, in the beginning of this book, that we spoke of volcanic -mountains being bottled up after an eruption, by the hardening of -the lava which remained in the crater and the tube that connects the -crater with the place from which the lava had been derived. We then -spoke of this hardened mass being known as a _volcanic plug_, or -stopper, explaining how the volcano could never again erupt through -its old crater unless it could develop sufficient force to blow out or -remove this stopper. - -Now besides the crater at the top of Mt. Taylor there were several -others in the eroded region surrounding the mesa, or high table-land, -from which Mt. Taylor rises. When, therefore, the erosion which -removed the 2,000 feet of rocks on all portions of the old mesa that -were not protected by the coating of lava, these old mountain plugs -were too hard to be worn away or eroded, and were, therefore, left -projecting into the air like vast pyramids. - -If you should ever visit Mt. Taylor and should go to the eastern -border of this mesa, and look over the eroded plain, you would see in -the lowlands a part of the places from which the 2,000 feet of matter -have been slowly eroded. Dutton describes the beautiful panorama that -is to be seen as follows: - - "The edge of the mesa suddenly descends by a succession of - ledges and slopes, nearly 2,000 feet into the rugged and - highly diversified valley-plain below. The country beneath - is a medley of low cliffs and bluffs, showing the browns - and pale yellows of the Cretaceous sandstones and shales. - Out of this confused patchwork of bright colors rise - several objects of remarkable aspect. They are apparently - inaccessible eyries of black rock, and at a rough guess, by - comparison with the known altitudes of surrounding objects, - their heights above the mean level of the adjoining plain - may range from 800 to 1,500 feet. The blackness of their - shade may be exaggerated by contrast with the brilliant - colors of the rocks and soil out of which they rise, but - their forms are even more striking." - -These black piles are the _necks_ or lava plugs of extinct volcanoes. -They rise above the level of the plain because, being harder than -the surrounding rocks, they have resisted erosion. In some cases -these necks or plugs have been converted by shrinkage, on cooling, -into beautiful columns, somewhat of the type of the basaltic columns -of the Giant's Causeway. It would be difficult to count the number -of volcanic necks that can be seen near the edge of the mesa. One's -attention is at once attracted to some dozen of these piles, which are -especially striking on account of their great size, and ominous black -color, but the number is by no means limited to this dozen. There are -hundreds of them. - -Fig. 19 gives some idea of a part of the view from the edge of the -mesa, and Fig. 20 the appearance of two of these volcanic necks. - -But besides high volcanic mountains such as the San Francisco -Mountains and Mt. Taylor, there are, in different parts of the United -States, to be found fragments of huge craters from which, in the -geological past, immense quantities of lava have escaped. In some -instances these craters are but fragments of huge craters, that, like -the crater of Mt. Somma, in Vesuvius, have been nearly completely -blown away by some unrecorded explosion during the far past. - -[Illustration: FIG. 19. PANORAMA FROM THE MESA AT THE EDGE OF MT. -TAYLOR _From U. S. Geological Survey_] - -A crater of this type, known as Ice Springs Crater, is situated in the -desert valley west of the Wahsatch Mountains, some 125 miles south -of Salt Lake City, Utah. This crater is especially interesting from -the fact that it occupies a position on a plain that was formed by -the deposition of sediment in an immense lake that covered this part -of the United States very long before man lived on the earth. We -are alluding to Lake Bonneville, a lake that existed in a geological -time known as the Glacial Epoch. This lake occupied the territory now -filled by the Great Salt Lake of Utah, but towards the close of the -Glacial Epoch it was immensely larger than it is now. This can be -shown not only by the presence of shore lines, that are clearly marked -on the sides of the surrounding mountains, but also by the ancient -lake beaches, and deltas, that are common in the district, so that -instead of there being the comparatively limited area of Great Salt -Lake as marked on the maps of to-day there was a lake that had an area -of 19,750 square miles, that covered an area on which at least 200,000 -people dwell. - -[Illustration: FIG. 20. VOLCANIC NECKS, EDGE OF MESA AT MT. -TAYLOR _From U. S. Geological Survey_] - -A similar lake, known as Lake Lehontan, existed at the same time, -covering large areas in the western parts of Nevada. - -Coming now to Ice Springs Craters in Utah, we find here three small -craters formed of scoriae and lapilli (volcanic ashes consisting of -small angular stony fragments). Near them lies a fragment of a much -larger crater known as the Crescent. In some respects this crater was -not unlike the crater of Somma that surrounded Mt. Vesuvius. It was -not, however, as large, having a diameter of only 2,200 feet. From -these craters streams of basalt flowed until they covered considerable -areas. - -A still more recent crater known as Tabernacle Crater is situated -four miles south of the Ice Springs Crater. Tabernacle Crater takes -its name from the building known in Salt Lake City as the Tabernacle. -According to Gilbert, this crater was formed at a time when Lake -Bonneville stood at a comparatively low level, or when the water was -only from fifty to seventy-five feet above the bottom of the valley -on which the crater now stands. At that time an explosive volcanic -eruption occurred on the bottom of the lake, and the rim of the -crater, built up by this explosion, was gradually pushed above the -surface of the lake, so as to shut out its waters. - -Extinct volcanic craters, not unlike those of Utah, occur also near -Ragtown, in Nevada, in a district known as the Carson Valley Desert, -in one of the broadest areas of what was once Lake Lahontan. Ragtown -is twenty-two miles southwest of Wadsworth on the Central Pacific -Railroad. At the present time there are two circular depressions or -volcanic craters filled with pools of strongly alkaline water known -as the Ragtown Pond, or Soda Lake. The large lake covers an area of -268-1/2 acres. Its greatest diameter is over 4,000 feet. Without going -into a detailed description it will suffice to say that the larger -crater probably was destroyed by an explosive volcanic eruption. - -Another intensely alkaline lake that fills an extinct volcanic crater -is the Mono Lake, situated in Mono Valley in California at the eastern -base of the Sierra Nevadas. It has an area of about 200 square miles. -The centre of the lake has two small islands named Pacha and Negit. -Immediately south of Mono Lake are a number of craters that occupy -portions of what was once apparently a fissure extending in a general -north and south direction. The highest of these craters are in the -neighborhood of 2,500 feet. - -But leaving these inconspicuous craters, let us briefly examine some -of the higher mountain peaks of the United States that are of volcanic -origin. One of the most conspicuous of these is Mt. Shasta. This -mountain is situated in California, at the northern end of the Sierra -Nevadas. It has a height of 14,350 feet. It is a snow-clad mountain of -a conical form, and is a conspicuous object in the landscape, because -it stands alone. - -Mt. Shasta is a double-coned mountain. Besides the cone on its summit -there is a well-developed cone known as Shastina on the western side -of the mountain, 2,000 feet lower than the main summit. - -There are well-defined lava streams on the slopes of Mt. Shasta. One -of these, which issued from the southern side of the mountain at -an elevation of 5,500 feet, divided into two streams. One of these -streams is twelve miles in length. The other entered the canyon of the -Sacramento River, thus displacing the water. - -Coming now to the Cascade Mountains, in Oregon and Washington, we -will find in them a number of giant peaks of volcanic origin. The -most important of these are in regular order from south to north, as -follows: Mt. Pitt, 9,760 feet; Mt. Mazana, 8,223; Mt. Union, 7,881; -Mt. Scott, 7,123; Three Sisters, Mt. Jefferson, 10,200, and Mt. Hood, -11,225, in Oregon; Mt. Adams, 9,570; Mt. St. Helen's, 9,750; Mt. -Rainier, 14,525, and Mt. Baker in Washington, 10,877. - -Nearly all these mountains have craters either on their summits or on -their sides. They are extinct volcanic mountains, that were, for the -most part, thrown up during the Tertiary Geological Period, so that -they have all been greatly affected by erosion. - -One of the most remarkable of the above volcanic mountains is Mt. -Mazana, in Oregon. This mountain has on its summit an approximately -circular cavity from five to six miles in diameter, that is occupied -by a lake of water known as Crater Lake. This lake is 6,239 feet above -the level of the sea, and has a depth of 1,975 feet. It is surrounded -by nearly vertical walls ranging from 900 to 2,200 feet deep, so that -the vast caldera of which this great depression consists has a depth -of at least 4,000 feet. - -Mt. Pitt, situated about sixty miles north of Mt. Shasta, in southern -Oregon, has a regularly shaped volcanic cone, and the remnant of a -crater at its summit. The Three Sisters and Mt. Jefferson lie to -the north of Mt. Pitt. Like the others they are ancient volcanic -mountains. But little is accurately known concerning them. - -Mt. Hood, 11,225 feet high, rises from the crest of the Cascade -range in Northwest Oregon, about twenty-five miles south of the -Columbia River. Mt. Hood is an exceedingly majestic mountain. At its -summit there are only portions of the walls of the original crater. -When ascended in 1888, streams of sulphur vapor were escaping from -fumaroles on its northeastern slopes, at an elevation of 8,500 feet -above the sea. - -Mt. Adams and Mt. St. Helen's lie to the north of Mt. Hood. Mt. Adams -about sixty miles to the north, and beyond this, Mt. St. Helen's. -Accurate information concerning the summit of Mt. Adams is still -lacking. Mt. St. Helen's in Washington has more of a conical summit. -Russell states that according to frontiersmen, St. Helen's has been -in a state of activity within the past fifty years. A French-Canadian -asserts that the mountain was in actual eruption during the winter of -1841-43, that at this date the light from the volcano was sufficiently -bright to enable one to see and pick up a pin in the grass at midnight -near his cabin some twenty miles distant. Mt. St. Helen's was ascended -in 1889, when fumaroles were found on the northeast side. - -Mt. Rainier in Washington is plainly visible from Puget Sound. It is -a most magnificent mountain. The summit has a bowl-shaped crater, of -an almost perfectly circular form. The inside of the crater, when -last ascended, was filled to within thirty or thirty-five feet of its -rim with ice and snow. There was, however, evidences of heat, since -numerous jets of steam were seen issuing from its interior rim. - -Mt. Baker, Washington, is the northernmost of the volcanoes of the -Cascade Mountains, south of the boundary line between the United -States and Canada. But little is known of this mountain. The summit -appears as a conical peak from Puget Sound, so that its form would -seem to show that it is of volcanic origin. According to Gibbs, -officers of the Hudson Bay Company, as well as the Indians, declared -that Mt. Baker was in eruption in 1843, when it broke out at the same -time as Mt. St. Helen's, covering the country with ashes. - -There are but few volcanoes in the Rocky Mountains which extend from -north to south through the United States at a considerable distance to -the east of the Sierra Nevadas and Cascade Ranges. The Spanish Peaks, -situated in the southeastern part of Colorado about sixty miles south -of Pueblo, are the remains of ancient volcanoes. Two of the most -prominent of these peaks rise from 12,720 to 13,620 feet above the sea. - -We shall make no effort to attempt to describe the volcanic mountains -that may exist in those portions of the Rocky Mountain Ranges or the -Cascade Range lying in Canada. Comparatively little is known of them, -but inasmuch as volcanic activity has been manifested in Alaska, it -would seem highly improbable, as Russell remarks, that volcanoes -should suddenly cease at the northern boundaries of the United States -and then begin again at the most southern part of Alaska. It will be -sufficient to say that Mt. Edgecome, situated on an island in the -neighborhood of Sitka, is of volcanic origin, and that the Aleutian -Islands, beginning at Alaska on the east at the head of Cook's Inlet, -extend westward through the Peninsula of Alaska to the Peninsula of -Kamtschatka for a distance of nearly 1,600 miles. This belt, which -is called by Russell "the Aleutian Volcanic Belt," contains numerous -volcanoes that are known to have been active in historical times. - -Mt. Wrangell, on the Copper River, 200 miles northeast of the head -of Cook's Inlet, is a lofty volcanic mountain that is said to have -been in eruption in 1819, and at the time of last report was still -throwing out columns of steam. While much remains to be ascertained -about the volcanoes of the Aleutian Islands, it would appear that -there are active volcanoes on twenty-five of these islands, on which -some forty-eight craters have been found. Eruptions are common in the -district. - - - - -CHAPTER XI - -THE CATASTROPHE OF MARTINIQUE AND THE VOLCANIC ISLANDS OF THE LESSER -ANTILLES - - -The West Indies Island chain consists of two groups of islands; i. e., -the Greater Antilles, including Cuba, Jamaica, Hayti, and Porto Rico, -on the west, and the chain of the Lesser Antilles on the east. - -The Lesser Antilles consists of two parallel chains, the westernmost -of which is for the greater part mountainous with peaks several -thousand feet in height. All these islands are volcanic. The chain -on the east consists of low, calcareous rocks, or rocks consisting -largely of lime. - -In the western chain the islands beginning on the south are, Grenada, -St. Vincent, St. Lucia, Martinique, Dominica, Guadeloupe, Montserrat, -Nevis, and St. Eustace, while in the calcareous chain are found the -Tobago, Barbadoes, and others. - -Prior to 1902, the greatest volcanic eruption in this part of the -world occurred on the island of St. Vincent, with the volcano of -Soufriere. Although the forces displayed were exceedingly great, yet -they become insignificant when compared with the appalling eruption -that took place in Martinique only a short time ago; namely, May the -8th, 1902, when the volcano of Mt. Pelee, situated on the northwestern -part of the island, burst into an eruption so terrible that in -destruction of life it far exceeded the eruption of Krakatoa, although -the amount of energy causing the eruption was much smaller. - -[Illustration: FIG. 21. THE LESSER ANTILLES] - -Heilprin, in a book called "Mt. Pelee and the Tragedy of Martinique," -from whom most of the information of this chapter has been obtained, -calls attention to the fact that before the eruption of Pelee there -were plenty of warnings for those intelligent enough to note them. For -two or three weeks prior to May 8th, 1902, the volcanic activity of -Pelee had been rapidly increasing, the mountain throwing out clouds -of ashes and sulphurous vapors from its crater. By April 25th the -sulphurous vapors had so increased in quantity as to make breathing -difficult in St. Pierre. The ashes fell on the surrounding country and -by the 2d of May had so covered the streets of St. Pierre as to stop -traffic. - -Three days later, May 6th, shortly before noon, an avalanche of mud -poured down the slopes of the mountain with the rapidity of an express -train. These torrents of mud and water deluged the towns and villages -in the neighborhood. The activity of Mt. Pelee increased until the -morning of May 8th, 1902, when, almost at exactly 8 A. M., an -eruption occurred, so terrible in its effects that in two minutes the -city of St. Pierre was almost completely destroyed. - -St. Pierre, the principal town of Martinique, is situated on the -island of Martinique, on the northwestern coast, about ten miles -southwest of Mt. Pelee. St. Pierre was settled as far back as 1635. It -is situated on an open roadstead without any harbor. - -That there were many points of resemblance between the position of St. -Pierre and the destroyed city of Pompeii will be recognized as the -description of the catastrophe is given. - -St. Pierre was a beautiful city, and formed the natural outlet to one -of the richest districts in Martinique for the production of sugar -cane and cocoa. It contained many fine houses, the homes of planters, -wealthy bankers, merchants, and shippers, who, besides their regular -houses in the city, had constructed handsome villas on heights on the -outskirts of the city. The houses were to a great extent one or two -stories in height, and were in many cases surrounded by fine gardens. -The city extended along the coast for about two miles. The streets -were well lighted. - -The eruption of Mt. Pelee on May 8th, 1902, was of a very unusual -character, containing a feature that--with the exception of a volcanic -eruption of Soufriere, a volcanic mountain on the neighboring island -of St. Vincent, and an eruption of Kilauea in Hawaii--so far as I am -aware, never before occurred. This was a blast of highly heated air, -mingled with white hot or incandescent dust, that swept down the side -of the mountain with a velocity of one or two miles per minute, or -possibly more. - -Nearly all of the people in St. Pierre were killed. From the -appearance of the bodies it seemed that death was practically -instantaneous, and was due either to scorching or burning, or -asphyxiation by the breathing of highly heated air. The number of -people so killed, including almost the entire population of St. -Pierre, as well as a number of adjoining settlements, was not less -than 30,000. - -The zone of absolute destruction was limited to an area the extent -of which did not greatly exceed eight or nine square miles. On the -outskirts of this zone the destruction, though considerable, was less -complete. - -There was almost an entire absence of great earthquake shocks during -the eruption. - -Following the terrible eruption of May 8th were a number of less -violent eruptions on May 20th, 26th, June 6th, July 9th, and August -31st. According to Heilprin these eruptions were of the same character -as that of May 8th. - -There has been considerable discussion as to the exact causes of the -tornadic incandescent blast that caused the awful destruction of life. -Without entering this discussion it is sufficient to say that it is -now generally considered that the blast consisted of highly heated -air, and super-heated steam loaded with great quantities of finely -divided red hot or even white hot dust particles. - -While, perhaps, the force producing the awful eruption of Mt. Pelee -was greatly excelled in the case of many other volcanic eruptions; -such as Papandayang, in 1772; Asamayama, in 1783; Skaptar Joekul, in -1783; Tomboro, in 1815; Coseguina, in 1835; and Krakatoa, in 1883; -yet, in the words of Heilprin, "in intensity and swiftness of its -death-dealing blast ... the eruption of May 8th, and of later dates, -stands unique in records of volcanic manifestations." - -While the amount of ashes that accompanied the blast of white hot -steam and air was comparatively small, yet during the time between -this and the subsequent eruptions, the amount of ashes that were -thrown from the surface of Mt. Pelee was exceedingly great. - -According to Russell, in a paper on the volcanic eruptions of -Martinique and St. Vincent, in 1902, the amount of ashes and solid -matter generally thrown out from the crater of Mt. Pelee would be -equal to 40,000,000 cubic feet every minute, or one and a half times -the sediments discharged by the Mississippi in the course of a whole -year. - -According to Heilprin, however, the actual amount of dust thrown from -the crater of Mt. Pelee was, probably, 500 times greater than the -amount discharged by the Mississippi River in the course of a year, -and, consequently, considerably greater than that of all the rivers of -the world combined, or, as he says: - - "Mont Pelee has now been in a condition of forceful - activity for upwards of two hundred days; can we assume - that during this time it may have thrown out a mass of - material whose cubical contents are hardly less than - a quarter of the area of Martinique as it now appears - above the waters? One is, indeed, almost appalled by the - magnitude of this work, and yet the work may even be very - much greater than is here stated. We ask ourselves the - questions, what becomes of the void that is being formed in - the interior? What form of new catastrophe does it invite? - There can be no answer to a question of this kind--except - in the future happening that may be associated with this - special condition. But geologists must take count of the - force as being one of greatest potential energy, whose - relation to the modelling and the shaping of the destinies - of the globe is of far greater significance than has - generally been conceived." - -A curious circumstance connected with the eruption of Mt. Pelee was -the most pronounced electric and magnetic disturbances. Moreover, as -in the case of the eruption of Krakatoa, there were the same after -glows or red sunsets and sunrises due to the presence of fine volcanic -dust in the higher regions of the air. These phenomena were observed -over widely separated areas. - -It appears that this great eruption in Martinique was preceded by -severe earthquakes in the northern part of South America, especially -in Colombia and Venezuela. The most marked was the great earthquake -which on April 18th destroyed the city of Guatamaula; this was, -perhaps, the most destructive earthquake that has occurred in the -Western Hemisphere since the great earthquake of 1812, that destroyed -the city of Caracas. Indeed, Professor Milne suggests that it was this -earthquake that brought about the eruption of Mt. Pelee. - -Soufriere, on the island of St. Vincent, had a great eruption on May -7th, 1902, one day before the awful eruption of Mt. Pelee. No lava -flowed during this eruption. There were, however, great discharges -of mud, due to a lake that before the eruption filled the top of -a depression known as the old crater which lay southwest of a new -crater, or the crater that was formed during the eruption of 1812. The -old crater was nine-tenths of a mile across from east to west, and -eight-tenths of a mile from north to south. The depth to the crater -floor was from 1,000 to 2,400 feet. The surface of the new and shallow -boiling lake which occupied the deepest part of the floor during the -latter part of May, and from June to August, was estimated to be -only 1,200 feet above the level of the sea. The sheet of water that -occupied it before the eruption being several hundred feet higher. - -Soufriere did not fail to give warnings of its coming eruption. -Rumblings were heard two days before the explosion. On May 5th, 1902, -fishermen who crossed the lake noticed that the water was disturbed -and agitated. On the Tuesday following, May 6th, great clouds were -thrown out during the afternoon, and the volcano was illumined by a -reddish glare of fire. The first explosion was heard shortly before -two o'clock on the following day and the volcano burst into activity. -The explosions, together with great discharges of pumice, ashes, and -boulders, followed one another rapidly. A column of steam was shot up -into the air for a height of 30,000 feet. The severest paroxysm came -shortly after ten A. M., and was succeeded by others nearly -as violent during the next few hours. By this time a reddish curtain -of clouds nearly shut out the island from view, and rapidly advanced -over the land and descended on the sea. This eruption caused a loss of -life of about 1,350. - -This eruption of Mt. Soufriere was accompanied by the same tornadic -blast of glowing air. There was not, however, any single blast quite -as severe as that which attended the eruption of Pelee on May 8th, -1902. - - - - -CHAPTER XII - -SOME OTHER NOTED VOLCANIC MOUNTAINS - - -Since the limits of our book will prevent any further description -of volcanic districts or regions, we must content ourselves with -descriptions of some of the noted of the remaining volcanoes, although -many we will thus omit contain great wonders. - -As we have already seen from the description of Krakatoa, the island -of Java near which Krakatoa is situated is especially noted not only -for the great number of its volcanic mountains, but also for the -frequency and severity of their eruptions. - -Perhaps the most destructive eruption of any of the volcanic mountains -of Java was of a volcanic mountain called Papandayang. This volcano, -situated on the southern coast of the island, is 7,034 feet in -height, and was in eruption in 1772. According to Scrope, from whom -the details of this eruption have been obtained, two others of the -many volcanoes on Java, situated at 184 and 352 geographical miles -respectively from Papandayang, broke out at the same time into active -eruption, although several intervening cones were undisturbed. - -The eruption of Papandayang was of the explosive type, a large part -of the mountain being broken off by the great force of the eruption, -and its materials scattered far and wide over the surrounding country. -During this eruption forty villages with their inhabitants were -buried by great showers of ashes. An area of fifteen by six miles was -left in the shape of a huge pit by the great eruption. It was at -first believed by some that this pit was due to the actual sinking -in of the ground, but a more careful study has shown that it was in -reality caused by the great force of the eruption, being, in point -of fact, a vast explosive crater that was formed by the expulsion of -the materials that formerly filled it. Some idea of the great extent -of this eruption of Papandayang may be had by the size of this huge -crater that was six by fifteen miles in diameter. - -Another great volcanic mountain in Java that had a terrific eruption -was Galungoon, or Galung Gung. According to Lyell, from whom the facts -of this eruption have been obtained, prior to this eruption the slopes -of the mountain were highly cultivated and densely populated. There -was a circular pit or crater on the summit of the mountain, but there -had been no traditions of any eruptions prior to 1822. - -In July, 1822, the waters of the Kunir River, one of the small rivers -that flow down the slopes of the mountain, were observed to become -hot and turbid. On the 8th of October, 1822, a terrific explosion was -suddenly heard, accompanied by great earthquake shocks, when immense -columns of hot water and boiling mud, mixed with burning brimstone, -ashes, and lapilli, were thrown violently like a great waterspout from -the opening in the mountain, with such enormous violence that great -quantities fell across the River Tandoi, forty miles distant, while -the valleys in the neighborhood were filled with a burning torrent. -The rivers overflowed their banks and produced great destruction by -floods of burning and boiling materials that washed away all the -villages and cultivated fields in their path. During this eruption an -extended area was covered with boiling mud in which were completely -buried the bodies of many of those who perished. - -So great was the violence with which the boiling mud, cinders, etc., -were thrown out of the mountain that they entirely failed to fall on -many of the villages in the immediate neighborhood, while the more -remote villages were completely destroyed and buried out of sight -under the mud. - -The first eruption continued for nearly five hours. During several -days following the eruption, torrents of rain fell, which produced -floods in the rivers that covered the country far and wide with thick -layers of mud. - -Four days after the great eruption, that is, on the 12th of October, -1822, a second and still more violent eruption occurred, when immense -quantities of hot mud were again thrown out of the crater. Great -blocks of hardened lava called basalt were thrown a distance of seven -miles from the volcano. This eruption was accompanied by a violent -earthquake. It was during this eruption that a huge piece of the side -of the cone was blown out, not unlike the case of the Val del Bove on -Mt. Etna. The surrounding country was covered with mud. The immense -quantity of materials thus thrown out of the side of the mountain -produced changes in the courses of several rivers, thus causing great -floods which in the single night of October 12th drowned 2,000 people. -During these eruptions there were 114 villages destroyed, with a total -loss of life of about 4,000. - -There is a volcanic mountain on the island of Sumbawa that is noted -for the very destructive eruption that occurred on it in April, 1815. -If you examine the map of the Sunda Islands chain, you will see that -the island of Sumbawa lies immediately east of a little island called -Lombock, about 200 miles east of Java. - -This eruption of Sumbawa was of the most frightful violence, and, -indeed, with the exception of Krakatoa and Pelee, was one of the -greatest eruptions in historic times. - -Like all great eruptions, that of Sumbawa gave plenty of signs of -its coming. During April, 1814, the volcano manifested considerable -increase in its activity, and ashes fell on the decks of vessels -sailing past the island. - -The eruption began on April 5th, 1815, but reached its greatest -violence on the 11th and 12th of April. According to Lyell, the sound -of the explosion was heard at the island of Sumatra at a distance of -970 geographical miles towards the west, and in the opposite direction -it was heard for a distance of 720 miles. The destruction of life was -terrible. Out of a population of 12,000 in the province of Tomboro, -only twenty-six people escaped with their lives. - -Like many other great eruptions the shooting upwards of the great -column of matter from the crater produced a violent whirlwind that -carried people, horses, cattle, and almost every movable object high -into the air, and tore up huge trees by their roots. - -Immense quantities of ashes fell over the surrounding country, or were -carried towards Java to the west a distance of 300 miles, while on the -north they were carried towards Celebes for a distance of 217 miles. -Cinders covered the ocean towards the west two feet thick and several -miles in length, so that ships could hardly make their way through -them. - -The darkness in Java produced by the dense ash cloud was greater than -had ever before been experienced with the single exception of the -great eruption of Krakatoa. A considerable quantity of this volcanic -dust was carried to the islands of Amboyna and Banda, the last named -island being at a distance of 800 miles east of the volcano. - -This eruption of Sumbawa was attended by great lava streams that -covered vast areas of the land and afterwards poured into the sea. - -As in the case of the explosive eruption of Krakatoa great waves were -produced in the ocean all along the coasts of Sumbawa, and surrounding -islands. The sea suddenly rose from two to twelve feet. A great wave -rushed up the mouths of the rivers, and at the town of Tomboro, on -the west side of Sumbawa, an area of land was sunk in the waters and -remained permanently covered by eighteen feet of water. - -The most important of the still active volcanoes of Japan is -Assamayna. This mountain was in terrible eruption during the autumn of -1783, when dense showers of ashes thrown out of the crater darkened -the sky, turning the day into night, and, falling on the cultivated -fields around the mountain, changed them into deserts. During the -eruption some forty-eight villages were destroyed by showers of ashes -and red hot stones and thousands of the inhabitants were either killed -directly by the stones and ashes, or died from starvation, since their -fields were covered with ashes for miles around to a depth of from two -and a half to five feet. - -Another terrible eruption in Japan was in the volcanic mountain of -Wunzen, or Onzen-Gatake. This occurred during 1791-93. During the last -eruption of this volcano, 53,000 people lost their lives, either by -reason of the eruption of the volcano, or by huge waves set up in the -ocean by an earthquake. - - - - -CHAPTER XIII - -JORULLO, A YOUNG VOLCANIC MOUNTAIN - - -You must not suppose that when we speak of Jorullo as a young volcanic -mountain that we mean young in the sense that you or I might be called -young, but young as regards mountains; for Jorullo, now a great -mountain range, had no existence before the year 1759, and that would -make the mountain a little less than 150 years old, which so far as -mountains are concerned may properly be regarded as quite young. - -The story of Jorullo is very interesting, and affords an excellent -example of the great scale on which modern volcanic eruptions take -place during historical times. - -If you examine the map of Mexico on page 86 you will see that Jorullo -lies 170 miles southwest of the city of Mexico, and 108 miles from the -Pacific Ocean, which is the nearest large body of water. This mountain -is of especial interest because, if old traditions are to be believed, -it was thrown up during practically a single night. This wonderful -event took place on an elevated plain or plateau, called the Plain of -Malpais, that lies between 2,000 and 3,000 feet above the level of the -ocean. The plain was situated in a part of Mexico that was celebrated -for the growth of the finest cotton and indigo in the world. It -formed the large estate of a wealthy planter, Senor Pedro de Jorullo, -who lived at his ease as a wealthy planter is apt to do in tropical -countries like Mexico. - -Jorullo's plantation was covered by an especially fertile soil, since -it was formed by the deposits of volcanic ashes, dust, tufa, etc., -produced, most probably, by neighboring volcanoes long before man -appeared on the earth, for the plain of Malpais was bounded by hills -that were composed of volcanic materials. There had, however, been no -signs of volcanic activity in the neighborhood. It had indeed been -quiet, so far as volcanic eruptions were concerned, since the time of -the discovery of America by Columbus, until the middle of the last -century. The fertile fields of the Jorullo plantation were watered by -two rivers, or as we would probably call them, brooks, the Cuitamba -and the San Pedro. - -Signs were not wanting of the coming calamity. During June, 1759, -subterranean sounds were heard of a low rumbling character, which -every now and then increased until they resembled in intensity the -sounds produced by the firing of large guns. These sounds were -accompanied by earthquake shocks that greatly terrified the people -and caused them to flee from their homes. Nothing, however, occurred, -so, becoming accustomed to the noises, the people returned to their -houses. The noises and tremblings ceased for over two months, until, -on the 29th of September, 1759, they were again heard, and a terrible -eruption began. A long fissure opened in the earth, extending -generally from northeast to southwest. From this fissure flames -burst out, fragments of burning rock and stone, together with large -quantities of ashes were thrown to great heights in the air, and were -followed by streams of molten rock. Six volcanic cones were formed -along the fissure. The highest of these cones is what now constitutes -the volcanic mountain of Jorullo, which then reached a height of at -least 1,600 feet above the level of the plain. From its cone were -thrown out great quantities of lava of the same type as that which -escaped from the craters of many volcanic islands such as Hawaii and -Iceland, namely, basaltic lavas. This eruption, which began on the -29th of September, 1759, continued until the month of February, 1760. - -The account as above given was obtained by Humboldt, who visited the -country some fifty-six years after the eruption. This story was told -him by the Indians, but was also recorded in verse by a Jesuit priest, -Raphael Landiva, a native of Guatemala. According to the account given -Humboldt by the Indians, it appears that when a long time after the -eruptions had quieted down, they had returned to their old homes with -the hope of cultivating part of the grounds, they found the plains -still too hot to permit their living on them. - -According to Lyell, there was around the base of the cone, spreading -from them as a centre over an area of some four square miles, a convex -mass, about 550 feet in height, most of the surface of which was -covered with thousands of small flattish conical mounds from six to -nine feet in height. These, together with numerous large fissures that -crossed the plain in different directions, served as points for the -escape of sulphur vapors, as well as for the vapors of hot water. - -During the escape of lava from the craters in 1759, the molten rock, -spreading over the plain, ran into the channels of the river or brooks -before named, driving out the water. This water reappeared at the base -of the mountain in numerous hot springs. - -Humboldt thought that the conical mountains had been lifted or raised -by the formation of huge bubbles formed under the lava, thus causing -it to assume a shape not unlike that of a huge bladder. This opinion, -however, has not been accepted by geologists at the present time. -Scrope points out that this was probably the origin of the little -conical mounds that covered the surface of the principal conical -mounds but was not, in all probability, the cause of the mound itself. -He says: - - "With regard to the disputed question as to the origin - of the raised plain of the Malpais, M. de Saussure, the - last and most trustworthy visitor, entirely confirms the - opinion which I ventured to proclaim in 1825, that Humboldt - was mistaken in supposing it to have been 'blown up from - beneath like a bladder,' and that it is merely an ordinary - current of lava, which, owing to its very imperfect - liquidity at the time of its issue from the volcanic vent, - as well as to the overflow of one sheet or stream upon - another, had acquired great thickness about its source, - gradually thinning off towards the outer limit of the - elliptical area it covered." - -If you have been able to follow the above you will see that Mr. Scrope -means that in his opinion the cone of Jorullo is a lava cone like -that we have already studied on Mt. Loa or Mt. Kilauea, or, in other -words, that the lava as it came out from the opening on the top of -Jorullo, flowed in all directions around the opening, thus building up -a mountain in the form of a flat lava cone. - -Perhaps one of the reasons Humboldt had for believing the entire -elevation of Jorullo to be due to the formation of a huge bladder was -the fact that the plain on which the cone is situated, when struck, -gave out a sound as though there was a vast hollow space below it. -This was especially the case when the hoofs of the horses driven over -its surface produced sounds as though they were moving over the summit -of a hollow dome-like space below. But, as Lyell points out, this was -probably only due to the fact that the materials forming the cone were -very light and porous. - -According to Burkhardt, a German mining engineer who visited Jorullo -in 1827, there appears to have been no other eruptions of the volcano -since the time of Humboldt's visit. Mr. Burkhardt descended to the -bottom of the crater and observed that small quantities of sulphurous -vapors were still escaping. The small cones or _hornitos_, however, on -the slopes had entirely ceased emitting steam. It appeared, too, that -the twenty-four years that had passed since the time of Humboldt's -visit, the rich soil of the surrounding country had permitted the -successful cultivation of some crops of sugar cane and indigo. - -Russell appears to doubt the reliability of the information obtained -by Humboldt concerning Jorullo. He suggests that a poetical account -by the Jesuit missionary from whom Humboldt obtained much of his -information was not apt to possess marked scientific accuracy. While, -however, this may be true, yet to a certain extent it seems entirely -probable that the principal facts were as above given. The following -account as given by Humboldt, is taken from a translation made in the -early part of 1800: - - "The affrighted inhabitants fled to the mountains of - Aguasarco. A tract of ground from three to four square - miles in extent, which goes by the name of Malpays, rose up - in the shape of a bladder. The bounds of this convulsion - are still distinguishable in the fractural strata. The - Malpays, near its edge, is only twelve metres above the - old level of the plain called the Playas de Jorullo; but - the convexity of the ground thus thrown up increases - progressively towards the centre, to an elevation of 160 - metres (524.8 ft.). - - "Those who witnessed this catastrophe from the top of - Aguasarco assert that flames were seen to issue forth - for an extent of more than half a square league, that - fragments of burning rocks were thrown up to prodigious - heights, and that through a thick cloud of ashes, - illuminated by the volcanic fire, the softened surface - of the earth was seen to swell up like an agitated - sea. The rivers of Cuitamba and San Pedro precipitated - themselves into the burning chasms. The decomposition of - the water contributed to invigorate the flames, which were - distinguishable at the city of Pascuaro, though situated on - very extensive table-land 1,400 metres (4,592 ft.) elevated - above the plains of Las Playas de Jorullo. Eruptions of - mud, and especially of strata of clay enveloping balls - of decomposed basalt in concentrical layers, appeared to - indicate that subterranean water had no small share in - producing this extraordinary revolution. Thousands of small - cones, from two to three metres in height, called by the - indigenes ovens, issued forth from the Malpays.... - - "In the midst of the ovens, six large masses, elevated from - 400 to 500 metres each above the old level of the plain, - sprung up from a chasm, of which the direction is from - N. N. E. to the S. S. E. This is the phenomenon of the - Montenovo of Naples, several times repeated in a range of - volcanic hills. The most elevated of these enormous masses, - which bears some resemblance to the puys de l'Auvergne, is - the great Volcan de Jorullo. It is continually burning, - and has thrown up from the north side an immense quantity - of scorified and basaltic lavas containing fragments of - primitive rocks. These great eruptions of the central - volcano continued till the month of February, 1760. In the - following years they became gradually less frequent.... The - roofs of the houses of Queretaro were then covered with - ashes at a distance of more than forty-eight leagues in a - straight line from the scene of the explosion. Although - the subterranean fire now appears far from violent, and - the Malpays and the great volcano begin to be covered with - vegetation, we nevertheless found the ambient air heated to - such a degree by the action of the small ovens, that the - thermometer at a great distance from the surface and in the - shade rose as high as 43 deg. C." (109 deg. 4' F.). - - - - -CHAPTER XIV - -MID-OCEAN VOLCANIC ISLANDS - - -Besides the volcanoes we have already described, there are many others -situated in mid-ocean far from any continent. A brief description will -be given of a few of these. - -All the three great central oceans, the Pacific, the Atlantic, and the -Indian, contain numerous volcanic islands, some of which rise many -thousands of feet above the general level. - -We will begin with a description of some of the more important -volcanic islands of the Pacific. It was first pointed out by Kotzebue, -and afterwards by Darwin, that all the islands of the Pacific Ocean -can be divided into two great classes, the _high islands_ and the -_low islands_. All the high islands are of volcanic origin, while -the low islands are of coral formation. It is the opinion of Dana, -who has made a careful study of coral formations, especially in the -Pacific, that in all probability even the low islands of the Pacific -were originally volcanic, and that the deposits of coral had been made -along their shores after their volcanoes had become extinct. - -The islands of the Pacific, like the shores of the continents and -most of their mountain ranges, extend in two great lines of trend, or -general direction, which intersect each other nearly at right angles. -These lines extend from the southeast to the northwest, and from the -northeast to the southwest respectively, those extending in a general -direction from southeast to northwest being the most common in the -Pacific. - -Now, perhaps, the greatest number of the earth's volcanoes are -arranged along fissures, or cracks in the earth's crust. The craters -are situated along the cracks, the openings being kept clear at the -crater, and gradually closing elsewhere, probably by pressure. In -other words, most of the volcanoes follow one another along more or -less straight lines. For example, in the western part of South America -they follow the Andes Mountains. A similar arrangement exists in the -volcanoes of Central America, Mexico, and the United States. Now, this -is especially true of mid-ocean volcanoes of the Pacific which lie -along lines extending from southeast to northwest, or from northeast -to southwest, though mainly along the former. - -Some of the volcanic islands of the Pacific have already been -described or referred to, as, for example, the Aleutian Islands, -which stretch in a curved line from the southwestern extremity of -the peninsula of Alaska to Kamtschatka on the coast of Asia. We have -already described the island of Hawaii, the great volcanoes of the -Sandwich Islands chain, and besides these there are in the North -Pacific the Ladrone Islands, lying east of the Philippines. - -Some of the principal remaining islands are: the Fejee Islands, which -are volcanic, with numerous hot springs and craters. The Friendly -Islands, with the peak of Tafua, 2,138 feet high, an active volcano -with a large crater always burning, and two other volcanoes, Apia, -and Upala. Tahiti, to the east, is at present extinct. One of its -mountains, Orobena, said to be 10,000 feet high, has a crater on its -summit. The Marquesas, still further to the east, are also volcanic. -All of these islands lie generally in the lines of the northeast -trend. - -The Tongan or New Zealand Island chain extends in the direction of -the northeast trend. This, as you will see, is the direction in which -the two islands of New Zealand extend. The Tongan Island chain is -continued to the south through Auckland and the Macquaire Islands to -58 deg. S. Towards the north, in almost the same line, are the Kermadec -Islands near 30 deg. S. - -There are several active volcanoes in New Zealand. An explosive -eruption of Tarawera, in New Zealand, in 1883, continued for several -days, and was followed, three days afterwards, by an outburst in an -active volcano in the Bay of Plenty, and two months afterwards, by a -violent outburst in a volcano on the island of Ninafou in the Tongan -Islands. - -Coming now to the Atlantic Ocean we find a number of volcanic -mountains in the deep waters near mid-ocean. The principal of these, -besides Iceland, are the Azores, the Canaries, Cape Verde Islands, -Ascension Island, St. Helena Island, and Tristan d'Acunha. The Peak -of Pico, in the Azores, rises to a height of 7,016 feet. The Peak -of Teneriffe, in the Canaries, reaches the height of 12,225 feet. -Teneriffe is a snow-capped mountain. It has a cone on its summit with -precipitous walls like Vesuvius. Sulphurous vapors are continually -formed at its summit, but no flames can be seen. - -In the Cape Verde Islands is to be found the active volcanic mountain -of Fuego, rising 7,000 feet above the sea. It has a central cone that -has been broken down on one side like that of Somma on Vesuvius. Fuego -was in eruption in 1785, and also in 1799. - -Ascension Island, south of the equator, is formed entirely of volcanic -materials. This island rises from an apparently granite floor on the -bed of the ocean, in water 12,000 feet deep. - -St. Helena lies further to the south. It is an extinct volcano, and -has the remains of a crater on its summit with lava dikes in various -parts of the island. - -Tristan d'Acunha is an isolated mountain that lies in the South -Atlantic, south of St. Helena, 1,500 miles from Africa, the nearest -land. It is an extinct volcano that rises from a depth of 12,150 feet -to a height of 7,000 feet above the sea. It has a truncated cone on -its summit and a lake of pure water in its old crater. - -There are only a few volcanic islands in the Indian Ocean. Kerguelen -Island lies in the southern waters. St. Paul and Amsterdam to the -north, lying near 40 deg. S. lat., as well as the Crozet Islands, are -extinct volcanoes. - -In the Arctic Ocean is the volcanic island of Jan Mayen. In the -Antarctic Ocean, as far as is known, there are only two volcanoes, -Mt. Erebus and Mt. Terror. Mt. Erebus, 12,400 feet high, is an active -volcano. Mt. Terror, 10,990 feet high, is an extinct volcano. - - - - -CHAPTER XV - -SUBMARINE VOLCANOES - - -A submarine volcano is a volcano that erupts on the bed of the ocean -with its crater covered by the waters. Many of the great volcanic -mountains of the world began as submarine volcanoes. A crater first -opened on the floor of the ocean, and lava escaping, was heaped up -around the opening, until it emerged above the surface as an island. -As we have seen, the island of Iceland is believed to have begun in -this way. Such, too, in all probability, was the origin of Hawaii, -Vesuvius, Etna, and Santorin. - -But besides the volcanic mountains that were thrown up during the -geological past, there are others that have been called into existence -while man has been living on the earth. We will now describe a few -islands that have been formed in this manner by submarine volcanic -eruptions. - -That volcanic eruptions, or at least something that greatly resembles -eruptions, occur on the bed of the ocean too far below the surface to -permit them to be directly seen from above, has been shown in a number -of cases where the captains of vessels have reported that in certain -parts of the ocean, jets of water, or steam, and pillars of flame have -been seen rising to great heights from the surface of the water, and -that in certain regions sulphurous smoke has also been seen. During -such occurrences, the water is agitated, as if it were being violently -boiled. Moreover, these parts of the ocean are shaken by severe -earthquake shocks. - -Another evidence of submarine volcanic eruptions is to be found in -great quantities of ashes, scoriae, or pumice stone, that are seen -spread out over the surface of the ocean after the commotions referred -to in the preceding paragraph. Still another proof is that parts of -the ocean whose waters were previously very deep are found to have -suddenly shoaled. - -Of course, the best proof is the appearance of rocky reefs or small -islands thrown up above the surface of the water, especially where -volcanic cones appear. While in many cases the new islands thus thrown -up are subsequently washed away by the waves, yet some have continued -above the water. - -One of the most noted instances of the formation of an island by a -submarine volcano was Sabrina, which was thrown up in 1811, in the -Atlantic Ocean, off the shores of St. Michael in the Azores Islands. -Sabrina had a cone that was 300 feet in height. It did not long remain -above the waters, however, being soon washed away by the waves. It is -interesting to note that in the same part of the ocean where Sabrina -appeared, other islands have appeared and disappeared, at times long -before 1811; that is, during the year 1691, as well as during 1720. - -Another instance of a submarine island is Graham's Island, that was -thrown up in 1831, in the Mediterranean Sea, between the west coast -of Sicily and the nearest part of Africa, on which ancient Carthage -was situated. The part of the sea where the island was thrown up had -previously a depth of 600 feet. - -The general appearance of Graham's Island is represented in Fig. 22. - -Graham's Island was formed by accumulations of loose scoria and -cinders, together with blocks of lava and fragments of limestone. It -reached a height of 200 feet above the water, but only remained above -the surface for a few months, when it was washed away, leaving a -submarine bank some twelve miles in width, that was covered by water -of about 150 feet, but which, however, increased rapidly in depth -towards the edge until depths of from 1,200 to 2,000 feet were reached. - -[Illustration: FIG. 22. GRAHAM'S ISLAND--A RECENT VOLCANIC -ISLAND] - -According to Lyell, on the 28th of June, 1831, before Graham's Island -appeared, a ship passing over this portion of the sea felt severe -earthquake shocks. On July 10th of the same year, the captain of a -vessel from Sicily reported that as he passed near this part of the -Mediterranean, a column of water, 800 yards in circumference, was seen -to rise from the sea to a height of sixty feet, and that afterwards a -column of steam rising to a height of 1,800 feet was seen in the same -place. On again passing the same region on July 18th, this captain -found a small island about twelve feet in height, with a crater in -its centre, that was throwing out volcanic materials, together with -immense masses of vapor. - -The island thus formed grew rapidly, both in size and height. When -visited at the end of July, it had attained a height of from fifty to -ninety feet, and was three-quarters of a mile in circumference. By -August 4th, it had reached a height of 200 feet, and was then some -three miles in circumference. From this time, however, the island -began to decrease in size, as the waves began to wash it away. By -August 25th, it was only two miles in circumference. On September -3d, it had decreased to three-fifths of a mile in circumference, and -continued to decrease until it entirely disappeared, so that in the -year 1832, there were, according to measurements, some 150 feet of -water over its former site. - -The Mediterranean Sea between Sicily and Greece is also especially -liable to submarine activity. New islands appear and disappear so -frequently that in this region they are almost regarded as common -phenomena. - -There are many other parts of the ocean where submarine volcanic -eruptions are common. This is especially the case in the narrowest -part of the Atlantic Ocean between Africa and South America. Here -there is a region situated partly above the equator, though for the -greater part south of the equator, frequently visited by submarine -eruptions, that are accompanied by earthquakes, by the agitation of -the water, by the appearance of floating masses of ashes and scoriae, -as well as by columns of steam or smoke. Floating masses of ashes and -scoriae sometimes occur so thick as to retard the progress of vessels. - -But what forms, perhaps, one of the best instances of a large island -formed by submarine eruptions during historical times, is Bogosloff -Island in Behring Sea, some forty miles west of Unalaska Island. This -island, the position of which is seen on the accompanying map, is -known to the Russians as Ioanna Bogoslova, or St. John the Theologian. -It is situated in lat. 53 deg. 58' N., long. 168 deg. west. It is said that -during the year 1795, some of the natives of Unalaska Island saw what -they thought was a fog in the neighborhood of a small rock, which they -had known for a long time to project above the sea in these waters. -This rock was marked on some Russian chart dated 1768-69. It was seen -by Captain Cooke, in 1778, and was named by him Ship Rock. - -But it was not a fog that the Unalaskans had seen in the neighborhood -of Ship Rock; for, to their great surprise, the fog continued in sight -although everywhere else the air was quite clear. Of course, this -was a great mystery to the people. During the spring of 1796, one of -them, who possessed either greater curiosity than the rest, or greater -courage, or both, visited the rock. He returned, telling the strange -story that all the ocean around the rock was boiling, and that the -mist or fog was caused by the rising steam. What was taking place was -a submarine eruption. During May, 1796, sufficient matter had been -brought up from below to increase greatly the area of the small rock. - -[Illustration: FIG. 23. ALEUTIAN ISLANDS] - -During later years several attempts have been made to visit Bogosloff -Island. For example, the island was visited during 1872 and 1873, -when it was found to have increased in height to 850 feet. But no -appearance of any volcanic crater was to be seen. - -During October, 1883, a great volcanic eruption occurred there. -Considerable changes were produced in its shape, as well as in the -depth of the surrounding water. During this eruption, clouds of steam -completely hid the island. Great quantities of ashes obscured the -light of the sun. After the eruption, a new island was thrown up near -the old one, in a place where the water had previously been deep -enough for the ready passage of ships. The new island was about half a -mile from the old one. It was conical in form, from 500 to 800 feet in -height, and about three-quarters of a mile in diameter. - -The new island was visited in 1884 by the U. S. Revenue Marine Steamer -_Corwin_. Lieutenant Cartwell, who visited the island at this time, -described it as follows: - - "The sides of New Bogosloff rise with a gentle slope to the - crater. The ascent at first appears easy, but a thin layer - of ashes, formed into a crust by the action of rain and - moisture, is not strong enough to sustain a man's weight. - At every step my feet crushed through the outer covering - and I sank at first ankle-deep and later on knee-deep into - a soft, almost impalpable dust which arose in clouds and - nearly suffocated me. As the summit was reached, the heat - of the ashes become almost unbearable, and I was forced - to continue the ascent by picking my way over rocks whose - surfaces being exposed to the air, were somewhat cooled and - afforded a more secure foothold. - - "On all sides of the cone there are openings through - which steam escaped with more or less energy. I observed - from some vents the steam was emitted at regular - intervals, while from others it issued with no perceptible - intermission. Around each vent there was a thick deposit of - sulphur, which gave off suffocating vapors." - - - - -CHAPTER XVI - -DISTRIBUTION OF THE EARTH'S VOLCANOES - - -Having now considered at some length the principal volcanoes of the -earth, and endeavored to obtain some idea of the many wonders they -exhibit, especially as regards the vast quantities of material they -bring from the inside of the earth, as well as the great force with -which they sometimes throw these materials out of their craters, it -will be well to point out where such volcanoes are to be found. - -It may have seemed to you, when you have carefully followed what has -been said about the earth's volcanoes, that they are to be found -pretty nearly everywhere, at least so far as latitude is concerned; -and in this supposition you are correct; for there are volcanoes in -the Arctic Ocean, as in the volcanic island of Jan Mayen between -Iceland and Spitzbergen, there are Mt. Erebus and Mt. Terror in the -Antarctic Ocean, besides very numerous volcanoes in the Atlantic, -Pacific, and Indian Oceans, and their shores in both the temperate and -the torrid zones. - -There is, however, one thing that you have probably especially -noticed and that is that volcanoes are seldom found at very great -distances from the ocean, except on some of its arms or seas, such -as the Mediterranean Sea. I do not mean by this that all the earth's -volcanoes are either situated directly on the coast of the continents -or on islands, since, in such a large body as the earth, a distance of -a few hundred miles from the ocean is hardly to be regarded as being -very far from it. But it is true that all the earth's volcanoes are -either situated on the coasts of the continents, or on islands, and, -moreover, they are situated to a greater or less extent along lines, -which, as we have already pointed out, are believed to mark weak -portions of the earth's crust that have been fissured or fractured. - -In order that you may have some idea of this distribution, I think it -will be well to give you a number of interesting facts that have been -pointed out by Dana. According to this authority, there are something -in the neighborhood of 300 active volcanoes on the earth. Of these, -no less than five-sixths, or 250, lie either on the borders of the -Pacific Ocean, or on some of its many islands. Thirty-nine either -lie within or on the borders of the Atlantic, of which thirteen are -in Iceland, or near the Arctic Circle, three in the Canaries, seven -in the Mediterranean Sea, six in the Lesser Antilles, and ten in -the Atlantic Oceanic Islands. The Indian Ocean contains only a few -active volcanoes. There are, however, a much greater number of extinct -volcanoes, which may at any time again become active. - -The following is the distribution of the earth's volcanoes as given -by Dana. As you will see, from an inspection of Fig. 24, all of the -regions of volcanoes lie either on the borders of the continents, or -on islands in the oceans. The districts are as follows: - -1. _Scattered Over the Pacific Ocean._--This district includes the -following active volcanoes; i. e., the Hawaiian Islands, nearly in -mid-ocean, almost directly below the Tropic of Cancer; in the west -central parts of the South Pacific; in the New Hebrides; in the -Friendly Islands, the Tongan or New Zealand Islands, in the Santa Cruz -Islands, and in the Ladrones. - -[Illustration: FIG. 24. MAP OF THE WORLD, SHOWING LOCATION OF -ACTIVE AND RECENTLY EXTINCT VOLCANOES] - -2. _On the Borders of the Pacific._--This district includes the -volcanoes that extend from the southern part of South America -at intervals along the Andes Mountain range. Of these there are -thirty-two in Chile, seven or eight in Bolivia and Southern Peru; -about twenty in the neighborhood of Quito. Further north there are -thirty-nine in Central America, and seven in Mexico. Proceeding -northwards through the United States, there are a number of volcanic -mountains, generally extinct, in portions of the Sierra Nevadas -and Cascade Ranges. Probably a number of volcanic mountains exist -in portions of Canada lying between the northern boundaries of the -United States and Alaska, and a number in Alaska; some twenty-one -volcanic mountains in the Aleutian Islands; some fifteen or twenty -in Kamtschatka; thirteen in the Kuriles; some twenty-five or thirty -in Japan and the neighboring islands; some fifteen or twenty in the -Philippines; several along the northern coasts of New Guinea; a number -in New Zealand and south of Cape Horn; the volcanoes of the Deception -Island with its hot springs, and also in the South Shetlands 62 deg. 30' S. - -3. _In the Indian Ocean._--On the western border of the Indian Ocean -there are a few volcanoes in Madagascar; in the Island of Bourbon; -Mauritius; the Comoro Islands; and in Kerguelen Land on the south. -There are also volcanoes on the western border of the Indian Ocean -where the lofty peak of Kilima Ndjro, 18,000 feet, is volcanic. - -4. _Over the Seas that Separate the Northern and the Southern -Continents and in their Vicinity._--This is an especially active -region of volcanoes. For the sake of convenience the continents of the -world are sometimes divided into three pairs or double continents; -namely, North and South America, connected by the Isthmus of Panama; -Europe and Africa, connected by the Isthmus of Suez; and Australia and -Asia, completely separated by a sunken isthmus, the summits of which -form the Sunda Island chain. In the first of these regions we have the -very active group of the West Indies, where there are ten volcanic -islands. In the second pair of double continents we have the volcanoes -of the Mediterranean and Red Seas, and their borders, such as Sicily, -Vesuvius, and other parts of Italy, Spain, Germany, the Grecian -Archipelago, Asia Minor, and extending eastward through the Caspian, -Mt. Ararat, Demavend, on the south shores of the Caspian, Mt. Ararat, -and some few others along the borders of the Red Sea. - -In the East Indies we find the most intense centre of volcanic -activity in the world. Here there are some 200 volcanoes of which -there are nearly fifty in Java alone, more than half of which are -still active. There are nearly as many volcanoes in Sumatra, and many -in the small islands near Borneo, the Philippines, etc. - -5. _On the Borders of the Atlantic and Elsewhere._--It is an -interesting fact that there are no volcanoes on the eastern borders -of the Atlantic north of the West Indies Island chain. In the South -Atlantic the only volcano on the borders is one of the Cameroons -Mountains. In the Atlantic Ocean we have Iceland, the Azores, the -Canaries, Cape Verde, Ascension, St. Helena, and Tristan d'Acunha. - -This curious distribution of the volcanoes of the world near the -oceanic waters appears to be dependent rather on the very early shapes -of the continents and the ocean beds than on their present shapes. - - - - -CHAPTER XVII - -VOLCANOES OF THE GEOLOGICAL PAST - - -The question is often asked whether the volcanic eruptions of the -geological past were not much more violent and destructive than the -volcanoes of the present time. Now, while this is a matter that -properly belongs to the subject of geology, and will be treated at -greater length in the Wonder Book on Geology, yet a short mention -should be made of it here. - -It is the opinion of Dana that while there have been volcanoes during -the different geological ages, yet volcanic activity has increased -through the geological past until the age that immediately preceded -the appearance of man on the earth. He thinks there is no reason for -believing that there were any very great volcanic eruptions during the -earliest geological time known as the Archaeic. Dana speaks as follows -concerning this: - - "In this connection it is an instructive fact that in - eastern North America, at epochs when there was the - greatest amount of friction and crushing ... those of the - making of the Green Mountains and the Appalachians ... no - volcanoes were made, and little took place in the way of - eruptions through fissures." - -On the other hand, Prestwich seems inclined to think that the absence -of well-marked cones of volcanic material in the rock of the older -geological ages is not to be regarded as proof that no eruptions then -took place, since the very great amount of erosion that occurred -between that time and the Tertiary Age before the appearance of man, -would, probably, have completely obliterated any cones, and even the -volcanic materials would have undergone such changes as completely to -alter their general character. He agrees, however, with Dana that, -probably, the most violent and explosive volcanoes of the geological -ages have been those of the Tertiary Age. - -Without, however, attempting anything more than a brief reference to -the volcanoes of the geological past, it may be said that many of the -more important of the active volcanoes of the earth's present time -were begun in the Tertiary Age. Mt. Etna, Vesuvius, and Mt. Hecla are -believed to have commenced at this time. - -There is an interesting region of geological volcanoes in the -neighborhood of Auvergne in Central France. Here they occur in three -separate groups that extend over a high granite platform from north -to south for a distance of about 100 miles, and from twenty to eighty -miles from east to west. The eruptions began in the earlier portions -of the Tertiary Age, and continued down to the latter periods of -prehistoric times. Some of these volcanic craters remain to-day almost -as unaffected by erosion as if they had been formed but recently. - -Other regions of geological volcanoes are to be found in parts of -Spain near the foot of the Pyrenees Mountains, in parts of Italy and -Germany, as well as in regions in the Caucasus Mountains. - -In Asia Minor there exists a group of almost thirty extinct volcanoes -in the neighborhood of the Gulf of Smyrna. Both Little and Great -Ararat contain volcanic cones: that in the latter mountain was active -during historical times. There are also extensive volcanic districts -in the Taurus Mountains. In addition to these there are groups of -extinct volcanoes in portions of Central Asia. - -Aden, on the Red Sea, is the centre of an extensive volcanic district. -Indeed, on both shores of the Red Sea there are a few volcanoes that -are still active, while in Sinai, and in the districts of the south, -there are several extinct craters. - -But it is in the New World, especially on the Pacific coast of -North America, that volcanic activity was especially great during -the geological past. There is a district containing volcanic rocks -that extends through various parts of western North America, from -New Mexico and North California, to Oregon and British Columbia. -This district has a width of from eighty to 200 miles, and a length -of not quite 800 miles. This great area of nearly 150,000 square -miles is covered with great sheets of volcanic rocks except where -mountain ranges rise from them, or where the rivers have cut deep -valleys through them. In portions of California and New Mexico these -plateaus rise to heights of from 8,000 to 10,000 feet, while in parts -of Colorado, where they form huge dome-like mountains, they reach a -thickness of 14,000 feet. In Oregon the sheet of lava is 2,000 feet -thick, and, indeed, in some places, is estimated to have a depth of -7,000 feet. - -In the opinion of nearly all American geologists these great lava -flows in western North America were not of the type known as crater -eruptions, but were what are called fissure eruptions. Some of them -are believed to have occurred during geological times as early as the -Eocene. Prestwich, however, is of the opinion that the eruptions of -the past in these portions of the world were not confined to fissure -eruptions, but that crater eruptions also occurred; and that it was -towards the close of the Tertiary Age that crater eruptions occurred -with great lava flows. Indeed, as we have seen, in portions of Utah -and the neighborhood the remains of true craters can be found. - -Besides the above there are evidences of geological volcanoes of still -older times. In portions of Deccan, in southern Hindostan, there is an -immense plateau formed of trap rock, that extends from east to west -for a distance of 400 miles, and from north to south through from 700 -to 800 miles. This district, with an area of almost 200,000 square -miles, is covered with a vast lava sheet. It was, in the opinion of -Prestwich, from whom many of the facts of the geological volcanic -eruptions have been obtained, probably still more extensive. The -plateau of Deccan rises gradually from the east to the west, where, in -some parts of the Ghauts Mountains, it reaches a height of from 4,000 -to 5,000 feet. - -One of the greatest of these prehistoric volcanoes of Scotland was a -volcano in the Isle of Mull in the Hebrides. This volcano was probably -nearly thirty miles across at its base, and was from 10,000 to 12,000 -feet high. It is now only 3,172 feet in height. - -According to Judd the Island of Skye in Inverness-shire is the remains -of a volcano that was active in Tertiary times, probably many millions -of years ago. This volcano was very large, probably about thirty miles -across at its base, with a height of perhaps as great as 12,000 or -15,000 feet. Now there are only left some granite and other similar -rocks that form the Red Mountains and Coolim Hills of Skye that reach -about 3,000 feet above the sea level. - -There are many other parts of the world containing volcanoes that were -active during the geological past. The above, however, is as far as we -can describe such volcanoes in this book. - - - - -CHAPTER XVIII - -LAPLACE'S NEBULAR HYPOTHESIS - - -LaPlace's nebular hypothesis is the name given to an ingenious -hypothesis proposed by LaPlace, a celebrated French astronomer, in an -endeavor to explain how the solar system has been evolved. - -You will notice that this is called a hypothesis and not a theory. -The word hypothesis is properly applied to a more or less intelligent -guess or assumption, that has been made for the purpose of trying -to find out in the cause of any natural phenomenon. A theory is an -expression of a physical truth based on natural laws and principles -that have been independently established. A theory, therefore, is much -more complete than a hypothesis. A hypothesis, as Silliman remarks, -bears the same relation to a theory or law, that a scaffolding does to -a completed building, since it forms a convenient means for erecting -the building. LaPlace's work is properly called a hypothesis, because -it is not to be considered as any more than a means for enabling one -intelligently to inquire into the probable manner in which the solar -system has reached its present condition, by gradual steps or stages -during the almost inconceivable length of time since its creation. - -Before describing LaPlace's hypothesis it will be necessary to give -you some ideas concerning what is known by astronomers as the solar -system. - -The solar system consists of the sun, and the eight large bodies -called planets that revolve around the sun. It also includes a number -of moons or satellites revolving around the planets, a number of small -bodies, called planetoids or asteroids, together with numerous comets -and meteorites. Besides these there is probably a system of meteoric -bodies that are believed to revolve around the sun, and to produce, by -the reflection of the light from their surfaces, what is known as the -_zodiacal light_. - -The principal bodies of the solar system are the planets. These -constitute eight large bodies named in their order from the sun, -beginning with the nearest: Mercury, Venus, Earth, Mars, Jupiter, -Saturn, Uranus, and Neptune. The last four planets, Jupiter, Saturn, -Uranus, and Neptune are much larger than the others, and are therefore -known as the _major planets_ in order to distinguish them from -Mercury, Venus, Earth, and Mars, which are called the _minor planets_. -You can remember the order in which the last three planets come by -their initial letter, S-aturn, U-ranus, and N-eptune, spelling the -word SUN, around which they all revolve. - -It may be interesting to state here that the ancients knew of seven -only of these planets. Since, as they asserted, there were only seven -days in the week, and seven openings into the head; i. e., two for the -eyes, two for the nostrils, two for the ears, and one for the mouth, -it was natural that there should be but seven planets. During later -years, however, an eighth planet was discovered and named Neptune. It -would be interesting to explain to you how the position of this planet -was reasoned out by mathematical calculations, that is, in other -words, how, as a result of such calculations, an astronomer was told -that if he would point his telescope to a certain part of the heavens -he would discover a new planet. He did this and located the planet -Neptune. However interesting this story may be it belongs properly -to astronomy, and will be described in full in the Wonder Book of -Astronomy. - -In the opinion of some astronomers it is quite probable that a ninth -planet will be found far beyond the orbit of Neptune. There may also -be some additional planets discovered between Mercury and the Sun. - -Besides the eight known planets there exist, somewhere between the -orbits of Mars and Jupiter, many smaller planets called _asteroids_, -or _minor planets_. A long time ago it was pointed out by Bode that -a curious relation exists between the distances of the planets from -the sun. This relation or law is generally known, after the name of -the astronomer who first called attention to it, as _Bode's Law_. -No reason has been discovered for this arrangement of the planets, -so that Bode's Law may be regarded as empirical. It may, however, -be mentioned here that the distances of all the planets from the -sun agrees with the law very closely, with the single exception of -Neptune, which is quite at variance with the law. - -It was noticed at an early date, that a gap existed between Mars -and Jupiter, so that astronomers began to believe that there was -probably a missing planet in that space, and this belief was greatly -strengthened when Neptune was discovered in 1781. Without going any -further into this story in this book, it may be said that it is the -general opinion of astronomers that the planetoids or asteroids were -formed possibly from the fragments of the missing planet, or, more -probably, from the breaking up of some of the outer rings on the -planet Mars. - -The distances of the planets from the central sun vary from the -nearest planet, Mercury, which is about 36,000,000 miles from the sun, -to the furthest, or Neptune, which is 2,766,000,000 miles from the sun. - -All the major planets have a single moon, or more, revolving around -them. For example, Jupiter has four moons; Uranus, six; Saturn, eight; -Neptune, one. As to the minor planets, Mars has two moons; and, as far -as is known, neither Mercury or Venus has a moon. Our earth has one -moon, but, as we shall afterwards see, this is not to be regarded as -a moon or satellite of the earth, but rather as a twin planet to the -earth. - -LaPlace's nebular hypothesis was proposed by LaPlace during the year -1796. While there are many objections that can be brought against -it, since it fails to account for all of the phenomena of the solar -system, yet it is a significant fact now, in the year 1907, nearly a -century and a quarter after the hypothesis was first announced, that -although modified in many respects, there has not been any hypothesis -proposed to entirely replace it. - -While the nebular hypothesis of LaPlace is necessarily a matter that -belongs to astronomy, yet it will be advisable to consider it here, -since it explains the source of the original heat of both the earth -and the moon, which we believe is the true cause of volcanoes. - -In his nebular hypothesis, LaPlace assumes that all the materials of -which the solar system is formed, were originally scattered throughout -space in the shape of an exceedingly rare form of matter known as -nebulous matter. He points out that if it be granted that this medium -began to accumulate around a common centre, so as to form a huge globe -or sphere, and if a motion of rotation on its axis from west to east -were given to this sphere that, on strictly mechanical principles, a -system of heavenly bodies corresponding to the solar system might have -been evolved. Let us, therefore, try to understand how this might have -been brought about. - -The nebulous matter that LaPlace assumed originally constituted all -the matter in the solar system, was highly heated gaseous matter. In -other words, it consisted of ordinary matter raised to a very high -temperature; LaPlace thought at a temperature very much hotter than -that of the sun. - -As this great mass of matter commenced to cool, it began to collect -around a centre and slowly rotate. Its contraction or shrinkage, while -cooling, must have caused an increase in the speed with which it spun -around or rotated on its axis. At first it spun but sluggishly, but as -it cooled and began to shrink this rate of rotation began slowly to -increase. - -Now you must bear in mind that the huge rotating mass, as imagined -by LaPlace, was very many times larger than the size of our present -sun. Indeed, instead of having a diameter of only 866,500 miles, its -temperature was so high that the nebulous matter of which it was -composed had expanded it so much that it extended far beyond the orbit -of Neptune, or had a diameter twice as great as 2,766,000,000 miles. - -As the huge mass continued to shrink or contract, its rotation -began to gradually increase until at last its centrifugal force was -sufficiently great to cause it to bulge out at the equator, so as -at last to separate a ring of gaseous matter. This ring was left -behind by the sun, as it continued cooling, and formed the first -planet that was born into the solar system. The ring might have -continued to revolve around the sun for a time, and would, of course, -revolve in the same direction as that in which the sun was rotating, -that is, from west to east. Eventually, however, it broke up into -smaller fragments, that afterwards collected in a single body, and, -assuming a globe-like shape of the planet, formed the planet Neptune. -Necessarily, too, the planet so formed not only would revolve in its -orbit from west to east in the same direction in which the sun was -revolving on its axis, but would also rotate or spin on its axis in -the same direction. - -After, in this way, throwing off the first planet, the central sun -continued to cool and grow smaller, until the increase in the rate -of its rotation was again such as to permit its centrifugal force to -form a second ring around its equator, which being left as the sun -continued to contract, gave rise to another planet, or to Uranus, and -so on until the four major planets and the four minor planets were -born. - -According to this hypothesis, the planet that was first born was the -planet that is farthest from the sun, that is, Neptune, and the planet -last born must have been the nearest planet, Mercury. - -But while all this planet forming was going on, the separate planets -also continued to shrink, and, therefore, began to rotate more rapidly -on their axes. Under the influence of the centrifugal force, ring-like -masses began to form around their equators, and these masses left by -the planet constituted their moons or satellites. As you can see, -according to this hypothesis, just as the planets would all revolve in -their orbits from west to east, and rotate on their axes in the same -direction as the sun, so, too, the moons or satellites of the planets -would also rotate on their axes, from east to west, and revolve in -their orbits in the same direction. - -In order to show the extent to which LaPlace's nebular hypothesis -explains the peculiarities of the solar system, we must inquire what -are the most important of these peculiarities. We will take these from -Young's general book on Astronomy, from which most of the facts in -this chapter have been condensed. They are as follows: - -The orbits of nearly all the planets and their satellites are nearly -circular; they are all in the same plane; and all revolve in the same -direction. They are, moreover, with the single exception of Neptune, -arranged at distances from the sun in accordance with Bode's Law. - -All the planets increase in both directions, towards and from the sun, -in density from Saturn, the least dense. - -All the planets, with the exception probably of Uranus, rotate in a -plane that is nearly the same as the plane of the orbit in which they -revolve. Moreover, with the exception of probably both Uranus and -Neptune, all the planets rotate in the same direction as that in which -they revolve. - -The satellites revolve in orbits whose planes nearly coincide with the -plane of the planets' rotation, while the direction of the revolution -of the satellites is the same as that in which their planets revolve. - -Finally, the largest planets rotate most swiftly. - -Now, LaPlace's nebular hypothesis explains nearly all of the above -facts. The following modifications of the hypothesis, however, are -necessary. Let us briefly examine some of these modifications. - -In the first place it can be shown that the original nebulous mass -instead of being at a higher temperature than that of the sun was -probably at a much lower temperature, since the condensation of -the gaseous matter must have increased the temperature. Instead, -therefore, of the original nebulous mass being purely gaseous it was, -as Young expressed it: "Rather a cloud of ice cold meteoric dust than -an incandescent gas or a fire mist." Or in other words, the original -nebulous mass from which the solar system was evolved, consisted of -finely divided particles of solid or liquid matter surrounded by an -envelope of permanent gaseous matter. - -A doubt, too, has been raised as regards the manner in which the -planets were liberated from the central sun. Instead of separating in -the form of a regular ring, it has been thought that probably in most -cases this separation assumed the shape of a lump. It might, however, -have occurred at times in the ring-like form as may be seen in the -case of the planet Saturn. - -Again, instead of the outer rings being separated first, and the -others in regular order, so that the outer planets are much the older, -it would seem possible, or, as Young states, even probable, that -several of the planets may be of the same or nearly the same age, as -they would be if more than one ring had been separated at one time, -or, indeed, several planets may have been formed from different zones -of a single ring. - -As you will see, LaPlace's nebular hypothesis assumes that both -sun and moon were in a highly heated condition when they were -separated from the nebulous sun, so that we can understand that the -former molten condition of their interiors was due to the heat they -originally possessed. - - - - -CHAPTER XIX - -THE EARTH'S HEATED INTERIOR, THE CAUSE OF VOLCANOES - - -As we have already seen, the nebular hypothesis of LaPlace would seem -to make it more than probable that the earth was originally in a -highly heated condition, and only reached its present state after long -cooling. While this cooling has gone on for probably millions upon -millions of years both before and during the geological past, yet in -the opinion of perhaps the best geologists the interior of the earth -is still very hot, only the outer portions or crust having hardened by -loss of heat. - -That there is a very hot region somewhere inside the earth is evident, -since from some place or places below the surface there come out -the immense streams of lava that, continuing to flow at irregular -intervals, have at last built up such great masses of land as the -island of Hawaii, the still greater island of Iceland, the even -greater lava fields of the western United States, and the great -plateau of the Deccan in southern Hindustan. - -It certainly must have required a great quantity of lava to build up -an island like Hawaii with its area of fully 40,000 square miles, for -the highest point on the summit of Mt. Kea reaches 13,805 feet above -the level of the sea, and, moreover, stands on the bed of the Pacific -Ocean in water fully 12,000 feet deep. - -But Iceland is only one of many similar cases. Volcanoes are to -be found in practically all parts of the earth, not only in the -equatorial regions, where they are especially numerous, but also in -the frigid and temperate zones. We must also remember the immense lava -streams that are known to have come from the interior during the great -fissure eruptions of the geological past. When all these facts are -taken into consideration, it would certainly seem that there is only -one source sufficiently great to supply this wonderful demand, and -that is the entire inside of the earth. - -But entirely apart from volcanic phenomena there are other proofs that -the entire interior of the earth is in a highly heated condition. The -differences of temperature caused by the sun during day and night -do not affect the earth much below a depth of three feet, while the -differences of temperature between summer and winter do not extend -much further below the surface than forty feet. Below these depths, in -all parts of the earth, the temperature of the crust rises at a rate, -which, although not uniform, yet is not far from an increase of one -degree of the Fahrenheit thermometer scale for every fifty or sixty -feet of descent. - -If the above rate of increase continues uniform the temperature of -the crust would be sufficiently hot to boil water at a distance of -about 8,000 feet below the surface, while at a depth of about thirty -miles the temperature would be sufficiently high to melt all known -substances at ordinary conditions of atmospheric pressure; that is, to -melt all known substances if they were subjected to such a temperature -at the level of the sea. - -In considering the above we must not lose sight of the fact that this -increase in temperature with descent below the surface of the earth's -crust occurs, not only in places where there are volcanoes, but over -all parts of the earth, thus seeming to point out that there is -something hot below the surface which fills the entire inside of the -earth. - -It is true the greatest distance to which man has actually gone down -through the earth's crust is but a few miles. We do not, therefore, -know by actual experience that the interior is anywhere in a fused -condition, yet the escape of lava or molten rocks in all latitudes, -and in the enormous quantities referred to above, seems to show that -the entire inside of the earth is at a temperature sufficiently high -to melt all known substances under ordinary conditions. - -It may be interesting in this connection to examine some of the proofs -of this increase in temperature with descent below the surface. The -following figures are given by Dana: - -Borings to great depths have been made in various parts of the earth, -both for artesian wells as well as for the shafts of mines. After -passing the line of invariable temperature, the rate of increase for a -total distance of 4,000 feet below the surface is in the neighborhood -of from one degree for fifty-five to sixty feet, or an average of -fifty-seven and a half feet for each degree of heat. In the case of -the deep artesian well bored at Grenelle, Paris, where a temperature -of eighty-five degrees Fahrenheit was reached at a distance of 2,000 -feet, the rate of increase was somewhat more rapid, being one degree -Fahrenheit for every sixty feet. - -In a deep well bored in a salt mine at Neusalzwerk, Prussia, a depth -of 2,200 feet showed a temperature of ninety-one degrees Fahrenheit at -the bottom. This was at the rate of one degree for every fifty feet of -descent. At Schladenbach, in Prussia, a well has been dug to the depth -of 5,735 feet with a temperature of 134 deg. F. A boring at Wheeling, in -West Virginia, reached a depth of 4,500 feet, 3,700 feet below the -level of the sea. Here the rate of increase of temperature in the -upper half was one degree Fahrenheit for every eighty feet, and in -the lower half of one degree for every sixty feet. - -It must not be supposed because the rate of increase of temperature is -not uniform that the argument of a highly heated interior is weakened. -On the contrary, it would be very surprising if the rate continued -uniform; for it is evident that the conducting power of different -materials in the earth's crust for heat must necessarily make a great -difference in the rate at which heat should increase, as we go farther -down into the earth. This is so important a matter that I will explain -it at somewhat greater length. - -Let us suppose that instead of the highly heated interior of the -earth, we consider the simple case of a hot stove, the doors or other -openings into which are closed so that it is impossible to see the -red hot coals inside. Now, suppose holes were bored in the sides of -this stove not deep enough to reach the red hot mass within, and that -tightly fitting rods or plugs all of the same length and thickness, -but of different kinds of materials such as wood, earthenware, glass, -iron, copper, silver, and gold, etc., were so placed in the holes as -to tightly fit them. Now, under these circumstances the end of all -the plugs would be at the same distance from the heated inside. They -would not, however, by any means show the same temperatures, the -metallic rods would be too hot to touch, while the end of the piece -of wood would hardly be hot enough to burn the hand when held against -it. The piece of glass and earthenware though less cool would be much -less hot than the different rods of metals. Their temperatures would -be necessarily affected by their conducting power for heat. The wood, -the glass, and the earthenware being poorer conductors than the metals -would show much lower temperatures. - -Now, the same thing is true with the different materials that -constitute the rocks of the earth's crust. Some of these are much -better conductors of heat than others, so that the rate of increase of -temperature with descent below the surface must necessarily vary with -the kind of materials that form the crust of different parts of the -earth. - -You may, therefore, safely conclude that the entire interior of the -earth is in a highly heated condition, and that the source of this -heat is to be traced to the heat the earth originally possessed when, -in accordance to the nebular hypothesis of LaPlace, it was separated -from the sun which gave birth to it, that the present crust of the -earth has been formed on the outside by the loss of a portion of this -heat. - -The rapidity with which a body cools, depends, among other things, -on the difference between its temperature and that of the medium in -which it is placed. The greater this difference of temperature the -greater the rapidity of cooling. Careful measurements made by Tait, -the English physicist, show that our earth loses every year from each -square foot of surface, an amount of heat that would be able to raise -the temperature of one pound of water from the melting point of ice to -the boiling point of water, or from 32 deg. F. to 212 deg. F. The rate of loss -of heat, must, therefore, have been much greater when the earth was -more highly heated than it is now, and will be much smaller than now -many years from the present. - -Now, let us suppose, what nearly everyone acknowledges to be true, -that the earth was originally so hot as to be a molten globe, and that -while in this molten condition, it began to revolve or move around the -sun. Since the empty space through which the earth moves is very cold, -something in the neighborhood of 45 deg. below the zero of the Fahrenheit -thermometer scale, the loss of heat would take place very rapidly and -a thin crust of hardened materials would be formed on the outside. Now -all the time the earth is cooling, it is shrinking or growing smaller. - -A very little thought will convince you that this cooling or shrinkage -could not go on uninterruptedly; for, while the earth was cooling it -was contracting, or growing smaller, and in this way a great pressure, -or as it is generally called in science, a great stress was being -produced. Every now and then this stress became so great that the -crust of the earth was fractured or broken. - -At first these fractures would not require a very great amount of -stress or force, since the crust of lava was then very thin. After -great periods of time, however, the crust grew thicker and thicker, -and the amount of force required to break it continually increased, so -that the fractures of the crust produced a greater disturbance. - -Whenever the earth's crust was fractured in this way the earth was -shaken by what are called earthquakes, while a part of the molten -interior would run out or escape, making volcanoes. In the very early -times neither the earthquakes or the volcanoes were as energetic as -they were at later periods when the thickness of the earth's crust -increased. - -Now, having as we believe correctly come to the conclusion that the -entire interior of the earth is in a highly heated condition, the -next question that arises is as to the present condition of this -interior. A long time ago it was believed that the interior of the -earth is still melted, and that a cooled portion or crust surrounds -a great molten mass that fills all the inside; that it is this mass -which supplies the immense quantities of molten rock or lava that -escape through the craters of volcanoes or through the fissures in -the crust. Without going into this question thoroughly, since it is a -very difficult question to understand, it will be sufficient to say -that there are many reasons why it is impossible to believe that the -interior is still melted. - -You will understand that if the interior of the earth were melted like -a huge central sea of fire that each volcano would necessarily affect -all the others. Now, as we have seen, this is never the case, so that -this is one reason we cannot believe in the existence of a melted -interior. - -Another reason we cannot believe in a molten interior is an -astronomical consideration. It can be shown that under the attraction -of the sun and moon the earth could not possibly behave as it does -if it were still liquid in the interior. That, on the contrary, the -behavior of the earth to the attraction of the sun and moon is such as -to make it necessary for us to believe that it is as rigid throughout -as would be a globe of steel of the same size. - -I can easily understand that you find it very difficult to see how it -can be believed that the interior of the earth is solid and yet at the -same time be sufficiently hot to melt. I can imagine hearing you ask -if it is hot enough in the inside to melt any known materials, why it -is not melted. The reason, however, is very simple when you come to -think it over. For a solid to fuse or become melted, it is not only -necessary for it to be heated to a temperature which is different for -different substances, but that at the same time it is heated it shall -have plenty of room in which to expand or grow bigger. In other words, -the temperature required to fuse any substance increases very rapidly -with the pressure to which that substance is exposed. - -Now, try to think of the pressure to which the materials that fill -the inside of the earth are subjected at great distances below the -surface. This pressure is enormous, not only by reason of the weight -of the many miles of rocks that are pressing down, but also by reason -of the enormous stress or pressure caused by contraction or shrinkage. -When we say that the interior of the earth is hot enough to melt all -known substances we mean hot enough to melt them if they could be -brought from great depths to the level of the sea, but not hot enough -to melt them when subjected to the great pressure that exists in -regions far below the surface of the earth. - -Briefly, the condition of things is believed to be as follows: The -entire interior is filled with rock hot enough to melt at the level -of the sea, but under too great pressure to melt. If this be granted, -as it is by perhaps the greatest number of men who are competent to -judge, the phenomena of earthquakes can be readily explained, as can, -indeed, the phenomena of those great movements whereby great changes -of level take place in different parts of the earth. - -Now let us see how volcanoes can be explained on the assumption that -the interior of the earth is hot enough to melt, but remains solid -only because there is no room for the heated mass to expand in. Such -a heated interior as we have imagined, must be constantly losing its -heat and, therefore, shrinking. Every now and then this shrinkage must -produce great fissures or cracks in the solid crust of the earth. -Now should such cracks or fissures extend downwards to the heated -interior, there must result a decrease in the pressure. The rocks -would, therefore, begin to expand and would be forced by the great -pressure to rise slowly in such cracks or fissures. The further they -rise the greater the relief of pressure, until they at last assume a -molten condition in which they are forced out through the craters of -volcanoes as molten rocks or lava. - -But it is not only volcanoes that seem to indicate a highly heated -plastic condition as existing in the earth's interior. As geologists -well know, there are to be found in the various strata of the earth -places where great fissures have been made at various times during the -geological past. These fissures vary in width from a few inches to -many hundreds of feet, and are frequently scores of miles in length. -Lava either flows out of them, and covers adjoining sections of the -country, or simply rises in them and, afterwards cooling, forms dikes. -In many instances, however, the lava is forced in between more or less -horizontal layers and in some cases has caused these layers to assume -the shape of what geologists know as _subtruderant mountains_. Some -of the eastern ranges of the Rocky Mountains have been formed in this -manner. - -We can, therefore, picture to ourselves the following as the manner -of formation of an ordinary volcano. A fissure is first formed in the -solid crust of the earth, extending downwards to the regions of great -heat. There is thus produced a relief of pressure, so that at this -point the highly heated rocks begin to be slowly forced up through the -fissure. As they rise higher and higher they become less solid and -finally expand into fused masses that can flow out of the crater or -opening in the earth's surface. In this way a volcano is started. - -But for this volcano to continue in eruption, it is necessary that -the conditions shall continue that force the molten rock upwards from -great depths. It is not enough for the lava to fill the crevice that -exists upwards to the surface, it must continue to be forced upwards -until it escapes. If it is permitted to remain in the fissure for any -time, it hardens, and only great dikes are formed. It would seem, -therefore, that some other force must be called into action to keep -the fissure open or, in other words, to prevent the chilling of the -lava. Now, this force is generally believed to be the expansive force -of steam or the vapor of water. - -As Dana points out, by far the greater part of the vapor which escapes -from the craters of volcanoes consists of steam or the vapor of water. -Indeed, it can be shown that for every hundred parts of different -vapors, at least ninety-nine of such parts consist of water vapor. It -is for the greater part, to the pressure of steam or water vapor that -the escape of lava from the tube near the top of the crater is due. - -Of course, the question arises as to where the water comes from that -produces this steam. There are three possible sources. From the rains; -from leakage at the bed of the ocean; and from vapors existing at -great depths below the surface. - -It is not probable that either rain water, or water from the ocean, -penetrates through the earth's crust for distances much greater than a -few thousand feet. It is, however, very well known that in all parts -of the earth, except in desert regions, whether they are near or far -from the ocean, the rocks are always found fully charged with water. -When, therefore, the slowly rising lava passes through the moist rocks -that everywhere form the crust of the earth, there must be formed in -them great quantities of steam under very high pressure. Moreover, -many substances, especially those forming lava, possess the power of -absorbing large quantities of steam and other gases. Therefore, as -the molten material reaches the moist rocks in the earth's crust, it -becomes highly charged with steam, and as the lava rises towards the -surface this steam expands. - -Where the lava is in a very fluid condition the steam quietly escapes, -as does the steam from the surface of boiling water. But where the -lava is viscous, like tar or pitch, great bubbles are formed, which, -on their explosion, throw the lava upwards for great distances into -the air. - -We can, therefore, account in this manner for both the non-explosive -as well as the explosive type of volcanoes. - -It must not be supposed, however, that it is the explosive power of -steam which is the principal cause of the lava rising upwards from -great depths. This is caused by the great pressure or stress set up -by the contraction of a cooling crust. The pressure of this steam is -added to this pressure which keeps the lava flowing upwards from great -depths below. - -The objection has sometimes been urged that it is impossible to -believe the lava comes from a highly heated interior, because, as is -well known, lavas are of different types even when coming from the -same volcano at different times of eruption. While such an objection -would have weight were it believed that the interior of the earth is -still in a molten condition, it loses its weight when one believes -that the interior is solid. It must, however, be acknowledged that -the largest part of the interior of the earth would probably have the -same chemical composition if it had ever been in a completely melted -condition throughout. - -I do not doubt you have already concluded that the reason the earth's -volcanoes are practically limited to the borders of continents, -or to the shores of islands, is the leakage of the ocean waters -into the crust at these parts. This was at one time believed by -most geologists. That sea water has much to do with such volcanoes -as Vesuvius there is no doubt, but it is now generally recognized -that it is not so much the present outlines of the earth, or the -present arrangement of its land and water areas, that determines the -distribution of the world's volcanoes. It is rather believed that the -location of the lines of fractures along which the earth's volcanoes -are found were determined by conditions that occurred long before the -earth assumed its present outlines. - -But there is another explanation that has been suggested as regards -the condition of the interior of the earth. Judd refers to this -explanation as follows: - - "Some physicists have asserted that a globe of liquid - matter radiating its heat into space, would tend to - solidify both at the surface and the centre at the - same time. The consequence of this action would be the - production of a sphere with a solid external shell and a - solid central nucleus, but with an interposed layer in a - fluid or semi-fluid condition. It has been pointed out that - if we suppose the solidification to have gone so far as - to have caused the partial union of the interior nucleus - and the external shell, we may conceive a condition of - things in which the stability and rigidity is sufficient to - satisfy both geologists and astronomers, but that in still - unsolidified pockets or reservoirs, filled with liquefied - rock, between the nucleus and the shell, we should have - a competent cause for the production of the volcanic - phenomena of the globe. In this hypothesis, however, it is - assumed that the cooling at the centre and the surface of - the globe would go on at such rate that the reservoirs of - liquid material would be left at a moderate depth from the - surface, so that easy communication could be opened between - them and volcanic vents." - -I must caution you, however, not to think that the above theory of -volcanoes is accepted by all scientific men. On the contrary, there -are many who believe that the earth is solid throughout because it -has completely lost its original heat; that it is only comparatively -small areas that are to be found filled with molten or at least highly -heated material. But these opinions are held largely by those who have -given their attention almost entirely to the phenomena of earthquakes, -or who base their reasonings on mathematical grounds only and have not -sufficiently considered the phenomena of volcanoes. Since, however, -they can be better understood after we have explained the phenomena of -earthquakes, we will defer their discussion to the last chapters of -this book. - - - - -CHAPTER XX - -SOME FORMS OF LAVA - - -In describing the wonders of volcanoes, we must not fail to say -something of the many remarkable forms that lava is capable of -assuming. - -All volcanic lavas contain large quantities of an acid substance known -as _silica_, or what is known better as _quartz sand_. This material -exists in lava combined chemically with various substances called -bases, the principal of which are alumina, magnesia, lime, iron, -potash, and soda. - -Although there are many kinds of lava, yet all lavas can be arranged -under three great classes according to the quantity of silica they -contain. - -_Acid lavas_ are those in which the quantity of silica is greatest. -In these lavas the silica, which varies from 66 to 80%, is combined -with small quantities of lime or magnesia, and comparatively large -quantities of potash or soda. Some of the most important varieties of -acid lavas are known as _trachytes_, _andesites_, _rhyolites_, and -_obsidians_. - -_Basic lavas_ are those containing from 45 to 55% of silica. They -are rich in lime and magnesia, but poor in soda or potash. Some of -the most important of basic lavas are the _dolerites_ and _basalts_. -Generally speaking, basic lavas are of a darker color than acid lavas, -and fuse at much lower temperatures. - -_Intermediate lavas_ are those containing silica in the proportion of -from 55 to 66%. - -While the temperature of liquid lava has not been very accurately -determined, yet, since we know that molten lava is able to melt silver -or copper, its temperature must be somewhere between 2,500 deg. F. and -3,000 deg. F., the melting point varying with the chemical composition. - -According to Dana lavas can be divided into the following classes -according to their fusibility; i. e., _lavas of easy fusibility_, such -as _basalts_; these lavas fuse at about 2,250 deg. F.; _lavas of medium -fusibility_, including andesites; these lavas fuse at about 2,520 deg. F.; -_lavas of difficult fusibility_, such as trachytes; these lavas fuse -at about 2,700 deg. F. - -But what is, perhaps, most curious about lavas is that when the -surface of a freshly broken piece of cold lava is carefully examined, -it is found to contain a number of small crystals of such mineral -substances as quartz, feldspar, hornblende, mica, magnetite, etc. - -The best way to study the different forms of lava crystals is to -prepare a thin transparent slice of hardened lava and then examine it -with a good magnifying glass. It will be found that the slice consists -of a mass of a glass-like material through which the crystals are -irregularly distributed, not unlike the raisins and currants in a -slice of not over rich plumcake. - -When examined by a more powerful glass, such as a microscope, cloudy -patches can be seen distributed irregularly through the glass-like -mass. When these patches are examined by a higher power of the -microscope they are seen to consist of small solid particles of -definite forms known as _microliths_ and _crystallites_. It has been -shown by a careful study of these minute objects that they form the -exceedingly small particles of which crystals are built up. - -If we fuse a small quantity of lava and then let it slowly cool, the -glassy mass will be found to contain numerous crystallites. On the -other hand, when fused lava is permitted to cool quickly, it takes on -the form of a black, glass-like mass known as _obsidian_ or _volcanic_ -glass, a very common form of lava in some parts of the world. - -In some lavas there are found larger crystals that appear to have been -separated from the glassy mass, under the great pressure that exists -in the subterranean reservoirs at great depths below the volcanic -crater, and then floated to the surface surrounded by the glass-like -material. Now when we examine these crystals with a higher power of -the microscope, we frequently find in them minute cavities containing -a small quantity of liquid and a bubble of gas, thus causing them to -resemble small spirit levels. The liquid in such cavities has been -examined chemically and in most cases has been found to consist of -water containing several salts in solution. Sometimes, however, the -liquid consists of liquefied carbonic acid gas. These wonderful things -will be discussed at greater length in the Wonder Book of Light. - -When the mass of molten rock or lava that comes out of the crater -of a volcano is thrown upwards in the air the condition it assumes -by the time it falls back again to the earth depends on the height -it reaches. If this height is great the lava chills or hardens -before reaching the earth, and assumes various forms according to -the size of the fragments. The largest of these fragments are called -_cinders_; the finer particles _volcanic dust_; while most of those -of intermediate particles are known among other things as _volcanic -ashes_. - -We have already seen that when an explosive volcanic eruption occurs -there is suddenly thrown out of the crater of the volcano a huge -column of various substances that rises sometimes as high as 30,000 -feet or even more. The smaller fragments of lava are quickly cooled -and form volcanic ashes, sand, cinders, or dust. These are rapidly -spread out by the wind in the form of a black cloud, that not only -covers the mountain but reaches out over the surrounding country, -completely shutting off the light of the sun. From this cloud -particles of red hot ashes, cinders, sand, etc., begin to fall, the -largest particles near the crater of the volcano, and the smaller -particles at much greater distances. In very powerful explosive -volcanic eruptions such as Krakatoa, the finer dust may be carried to -practically all parts of the world. - -Volcanic ashes consist of a fine, light, gray powder. These particles -take the name ashes from their resemblance to the ashes left after the -burning of pieces of wood or coal in an open fire. The name, however, -as Geicke points out, is unfortunate, since it is apt to lead one to -suppose that volcanic ashes consist of some burned material. Such an -idea is erroneous, however, since ashes do not consist of anything -that is left after burning, but merely of fine particles of molten -rock that have hardened by cooling. When in the shape of what is known -as volcanic dust these particles are so exceedingly small that they -can readily make their way through the smallest openings in a closed -room just as does the finest dust in the rooms of our houses when -they are shut up. There are cases on record where people have been -suffocated by the entrance of volcanic dust in closed rooms to which -they have fled for safety during volcanic eruptions. - -_Volcanic sand_ consists of the coarser particles of chilled lava that -are partly round and partly angular. They are of various sizes up to -that of an ordinary pea. Volcanic sand is formed by the breaking up of -the lava by the explosion of the vapors as they escape from the lava -on relief from pressure. Volcanic dust when examined by the microscope -is found to consist of very small particles that are more or less -crystalline. - -But besides the above there are larger fragments known as _lapilli_, -consisting of rounded or angular bits of lava varying in size from -that of a pea to an ordinary black walnut. These sometimes consist of -solid fragments, but are usually porous, sometimes so much so that -they readily float on water. - -A curious form sometimes assumed by lava consists of what are called -_volcanic bombs_. These are formed during explosive eruptions, -when masses of liquid lava are hurled high up into the air. During -their flight they take on a rotary motion, which tends to make them -globular, so that cooling, while still revolving, they assume the -form of a more or less spherical mass. At times, however, they are -still sufficiently soft when they strike the earth to be flattened out -in the form of flat cakes. When of a spherical form these are very -properly called volcanic bombs. - -That volcanic bombs have actually been subjected to a spinning motion -while in the air can sometimes be shown by the fact that masses of -scoriae are frequently found in the interior with air cells largest at -the centre of the bomb. - -Volcanic bombs are sometimes thrown from the crater to great -distances. During one of its recent eruptions, Cotopaxi threw out -bombs that fell at a distance of nine miles from the crater. - -According to Dana another form of lava bombs is sometimes found on the -slopes of the active volcanoes of Hawaii, where masses of lava acquire -a ball-like shape while rolling down an inclination. - -What are sometimes called volcanic bombs, but which are more properly -_volcanic vesicles_, are produced by small fragments of lava which -are thrown up in the air for only a moderate height and, on cooling, -assume pear-like forms. Fig. 25 represents the appearance of volcanic -vesicles. The direction in which these vesicles moved through the air -while in a molten state is indicated by their shape, the blunt end -being the end towards which the particles were projected. - -[Illustration: FIG. 25. VOLCANIC VESICLES _From Dana's Manual -of Geology_] - -But by far the greater portion of the hardened lava; i. e., the -coarser, heavier particles, fall back on the mountain, and collecting -around the crater build up volcanic cones, as already described in the -case of mountains of the Vesuvian type. - -There are two different ways in which the melted lava is broken up -into fine particles when it is thrown upwards from the crater of the -volcano. Nearly all lava contains large quantities of steam that are -shut up, or occluded in the mass, being prevented from escaping by -reason of the pressure to which the lava is subjected. The lava is -released from this pressure as it is thrown out of the crater. The -steam or gases escape explosively and thus break the lava into fine -liquid spray, which rapidly hardens. - -There is another way in which small particles of lava are formed. -Sometimes large pieces of hardened lava are shot upwards into the air -with a velocity as great as that with which a heavy projectile leaves -the muzzle of a large gun. These heavy particles striking against -one another, either while rising or falling, are broken into smaller -fragments. Sometimes, indeed, these fragments fall back again into -the crater from which they are again violently thrown out, and are -again broken into smaller fragments either while rising or falling. - -You will, probably, remember several instances of volcanic eruptions -where masses of rock were thrown violently up into the air out of -the crater. These larger masses are known as _volcanic blocks_. They -probably consist of masses of hardened lava that have collected in -the tube of the volcano during some of its periods of inactivity. -Sometimes, however, they consist of fragments of rocks that are not -of volcanic origin. Cases are on record where volcanic blocks have -been thrown out of the craters in so great quantities as to cover the -surface of many square miles of land with fragments hundreds of feet -deep. - -There is sometimes formed on the surface of a pool of lava as it -collects in the craters of such volcanoes as Mt. Loa or Kilauea, when -the volcanoes are not in eruption, a material resembling froth or -scum. The same thing sometimes occurs on the surface of some kinds -of lava as it runs down the side of the mountain. In this way a very -light variety of highly cellular lava known as _pumice stone_ is -produced. The action which thus takes place is not unlike that which -occurs during the raising of a lot of the dough from which bread is -made, where the carbonic acid gas which is formed during the raising -of the dough expands, and produces the well-known open cellular -structure of well-raised bread. In the case of pumice stone, however, -this raising goes on to such an extent that the mass consists often of -less than 2% of solid matter, the remainder being a tangled mass of -air. - -[Illustration: THE LAVA FLOW OF THE CRATER OF KILAUEA, HAWAIIAN -ISLANDS _From a Stereograph, Copyright, by Underwood & Underwood_] - -Fragments of lava that possess a cellular structure form what are -known as _scoriae_. The lightest of all kinds of scoriae is what is -known as _thread-lace scoriae_. Here the thin walls consist of mere -threads. Figs. 26 and 27 represent the appearance of thread-lace -scoriae from Kilauea. The separate threads are very fine, being only -from one-thirtieth to one-fortieth of an inch in thickness. As can be -seen, this form of scoriae have six-sided or hexagonal shapes. You can -form some idea of the great lightness of such scoriae when you learn -that they contain only 1.7% of rocky material. Indeed, they contain -so little solid material that a layer of volcanic glass only one inch -thick, if blown out into scoriae, would be able to produce a layer -sixty inches thick. - -[Illustration: FIG. 26. THREAD-LACE SCORIAE FROM KILAUEA _From -Dana's Manual of Geology_] - -Another curious form sometimes assumed by lava, especially in the -case of Kilauea, is where the lava is spun out in the form of long -silk-like hairs. This is called by the natives _Pele's hair_, after -the name of their goddess. Inasmuch as the origin of this form of lava -was at one time generally attributed to the action of the wind in -drawing out thread-like pieces from the jets of lava thrown upwards -from the pool, it will be interesting if its true cause is explained. - -[Illustration: FIG. 27. THREAD-LACE SCORIAE FROM KILAUEA _From -Dana's Manual of Geology_] - -Dutton, in his report on the Hawaiian volcanoes, refers to the -formation of Pele's hair as follows: - - "The phenomenon of Pele's hair is often spoken of in the - school books, and receives its name from this locality. - It has generally been explained as the result of the - action of the wind upon minute threads of lava drawn out - by the spurting up of boiling lava. Nothing of the sort - was seen here, and yet Pele's hair was seen forming in - great abundance. Whenever the surface of the liquid lava - was exposed during the break-up the air above the lake was - filled with these cobwebs, but there was no spurting or - apparent boiling on the exposed surface. The explanation of - the phenomenon which I would offer is as follows: Liquid - lava coming up from the depths always contains more or - less water, which it gives off slowly and by degrees, in - much the same way as champagne gives off carbonic acid - when the bottle is uncorked. Water-vapor is held in the - liquid lava by some affinity similar to chemical affinity, - and though it escapes ultimately, yet it is surrendered - by the lava with reluctance so long as the lava remains - liquid. But when the lava solidifies the water is expelled - much more energetically, and the water-vapor separates - in the form of minute vesicles. Since the congelation of - all siliceous compounds is a passage free from a liquid - condition through an intermediate state of viscosity to - final solidity, the walls of these vesicles are capable of - being drawn out as in the case of glass. The commotion set - up by the descending crust produces eddies and numberless - currents in the surface of the lava. These vesicles are - drawn out on the surface of the current with exceeding - tenuity, producing myriads of minute filaments, and the - air, agitated by the intense heat at the surface of the - pool, readily lifts them and wafts them away. It forms - almost wholly at the time of the break-up. The air is then - full of it. Yet I saw no spouting or sputtering, but only - the eddying of the lava like water in the wake of a ship. - The country to the leeward of Kilauea shows an abundance - of Pele's hair, and it may be gathered by the barrelful. A - bunch of it is much like finely shredded asbestos." - -You have probably often seen the beautiful frost pictures that collect -on the panes of glass in a room where the ventilation has been -neglected. These pictures consist of groupings of ice crystals that -collect on the surface of the windows, when the moist vapor-laden -air in the room is chilled by contact with their cold surfaces. Now -the crystals formed in cooling lavas are sometimes grouped in forms -closely resembling frost pictures. A few of such forms are represented -in Figs. 28 and 29 in lava from Mt. Loa and Mt. Kea. - -[Illustration: FIG. 28. FROST-LIKE LAVA CRYSTALS _From Dana's -Manual of Geology_] - -[Illustration: FIG. 29. FROST-LIKE LAVA CRYSTALS _From Dana's -Manual of Geology_] - -Certain varieties of lava, especially that which is found in dikes, -form cool, beautiful columns called basaltic columns. They are due to -the contraction that occurs on the cooling of the material. Instances -of basaltic columns are seen in the Giant's Causeway, on the northern -coast of Ireland, as well as in the Isle of Cyclops on the coast of -Italy. The general appearance of the latter is represented in Fig. 30. - -[Illustration: FIG. 30. BASALTIC COLUMNS, ISLE OF CYCLOPS, -ITALY] - -It is a curious fact that the entire mass of basalt does not generally -take the columnous form but only certain layers which terminate -suddenly above and below at structureless masses of basalt, as shown -in Fig. 31. These columns, however, are always found at right angles -to the cooling surfaces as seen in the figures. They may, therefore, -be inclined at all angles to the horizon. - -[Illustration: FIG. 31. COLUMNAR AND NON-COLUMNAR BASALT] - -When molten lava is only thrown up a short distance into the air -from a crater it is still partially molten when on falling it again -reaches the earth, and therefore clings to any surface on which it -falls. There are thus built up curious cones known as _driblet cones_, -in which the separate drops covering the sides of the cone can be -distinctly traced. Driblet cones are represented in Figs. 32 and 33. -Here, as can be seen, the separate drops can be readily traced as they -run down a short distance before cooling. - -[Illustration: FIGS. 32, 33. DRIBLET CONES _From Dana's -Manual of Geology_] - -We have already referred briefly to the _lava caves_ or _grottoes_, -that are formed in some of the lava streams issuing from Vesuvius, -Etna, or Hawaii. These caves consist either of a number of -communicating huge bubbles, or of the tunnels that are formed in the -lava by the hardening of the outside of the lava streams as they flow -down the sides of the mountain, and towards the close of the eruption -are afterwards emptied by the molten lava within continuing to flow to -a lower level before solidifying. Now, in the interior of these caves, -there are often found on the walls, as well as on the portions of the -floors of the caves, immediately below them, curious pendants, like -icicles, or, more correctly, like the _stalactites of limestone_ that -are seen hanging to the walls of caves in limestone districts, where -they are formed as follows: as the rain water sinks through limestone -strata it dissolves some of the lime, when, slowly falling, drop after -drop, from the roofs of the caverns, small particles of lime are -deposited on the roof, and in this manner a pendant of limestone is -formed. The water that falls to the floor of the causeway immediately -below, also builds up a dome-like hillock called a stalagmite. In due -time the pillar reaches downwards, and the opposite hillock upwards -until the two meet, thus forming great natural pillars that appear -to hold up the roof of the vast cave in which they have been slowly -formed. A number of _lava stalactites_ are represented in Fig. 34. - -[Illustration: FIG. 34. LAVA STALACTITES _From Dana's Manual -of Geology_] - -Now, in a similar manner these lava stalactites, formed in the lava -caves or grottoes, are caused by the stream as it escapes from the -walls of the caves depositing on them stalactites of various lava -minerals it has dissolved as it slowly passed through them. - -But the most important of all volcanic products is _volcanic dust_. -This, as we have seen, is so light that it remains longest in the air, -and is often carried by the winds to great distances from the volcano -from which it escaped. It may interest you to know that some of the -most fruitful of the great wheat fields of the western parts of the -United States owe their extraordinary fertility to immense deposits -of volcanic dust that have been thrown out from some of the great -volcanoes of the geological past, now found in an extinct condition in -these parts of the United States. - -According to Russell, immense deposits of volcanic dust are spread -over vast areas in Montana, Southern Dakota, Nebraska, and Kansas, as -well as over parts of Oregon, and Washington, and, indeed, over large -areas of southwestern Canada and Alaska. - -It is practically certain that many of the eruptions producing this -dust occurred within historic times. There must, therefore, have been -many times in these parts of our country when the dense ash clouds -hiding the sun turned the day into night and destroyed the forests and -other vegetation by showers of red hot ashes. There were produced, -too, the same great dread, and possibly loss of life as common during -historical eruptions. It is pleasing, however, to think that while -these great catastrophes brought suffering and dread to the people who -then lived on the earth, they were, nevertheless, but the forerunners -of those fruitful fields that at a much later age were to bless the -people who afterwards lived on them. - - - - -CHAPTER XXI - -MUD VOLCANOES AND HOT SPRINGS - - -Mud volcanoes are the more or less conical hillocks from which, under -certain conditions, mud is thrown out through the crust of the earth. - -Geikie defines mud volcanoes as follows: - - "Conical hills formed by the accumulation of fine and - usually saline (salty) mud, which, with various gases, is - continuously or intermittently given out from the orifice - or crater in the centre. They occur in groups, each hillock - being sometimes less than a yard in height, but ranging up - to elevations of 100 feet or more. Like true volcanoes, - they have their periods of repose, when either no discharge - takes place at all, or mud oozes out tranquilly from the - crater, and their periods of activity, when large volumes - of gas, and sometimes columns of flame, rush out with - considerable violence and explosion, and throw up mud and - stones to a height of several hundred feet." - -There are two kinds of mud volcanoes: those in which the mud is thrown -out by the action of different kinds of gases, and those in which the -mud is thrown out by the action of steam. - -Mud volcanoes may or not be volcanic phenomena. Those which occur in -the neighborhood of volcanoes whether active, dormant, or extinct, are -probably of volcanic origin. There are others, however, which occur -in regions far removed from volcanoes. These are probably due not to -volcanoes, but to chemical action and the eruptions are caused by the -action of gases. - -The gases producing these eruptions are either carbonic acid gas -(the gas that is given off from soda water); carburetted hydrogen -(the gas that is sometimes seen escaping from the bottom of marshy -ground); sulphuretted hydrogen (a gas that is given off from rotten or -decomposing eggs, and possessing the characteristic odor of decayed -eggs) and nitrogen gas derived from the atmosphere. In mud volcanoes -of the gaseous type the mud is generally cold, and the water salty. In -this latter case the mud volcanoes are also called _salses_. Daubeny -has pointed out that the mud volcanoes of this class that occur in the -neighborhood of Sicily are due to the slow burning or oxidation of -beds of sulphur. - -Mud volcanoes which eject hot mud by the force of eruption of steam, -which occur in volcanic districts, are of volcanic origin. They are -caused by the passage of hot water and steam through beds of volcanic -rock such as tufa, or hardened volcanic mud and other volcanic -products. The hot water or steam raises the temperature of the mud -through which it passes to the boiling point. As Dana remarks, the mud -varies in consistency from very liquid muddy water to a thick mass -like boiling soap, or in some cases like masses of mud or paint, and, -in still other cases, to material like soft mortar, the consistency of -the mud varying with the dryness of the season. - -There are three regions where mud volcanoes are especially common. -One of the best known is in the Yellowstone National Park, four miles -north of Yellowstone Lake, and six miles from Crater Hill. Some of -these mud volcanoes have circular craters about ten feet in depth -around which they have built mounds, the rims of which are several -feet above the general level. - -There are well-known regions of mud volcanoes in different parts of -Iceland. Here, according to Lyell, they occur in many of the valleys -where sulphur vapor and steam bursts from fissures in the ground with -a loud hissing noise. In these regions there are pools of boiling -water filled with a bluish black clay-like paste, that is kept -violently boiling. Huge bubbles, fifteen feet or more in diameter, -rise from the surface of the boiling mass. The volcanoes pile up the -mud around the sides of their craters or basins. - -Another part of the world where mud volcanoes are especially numerous -is on the western shores of the Caspian Sea at a place called Baku. -These are of the gaseous type and are attended by flames that blaze -up to great heights often for several hours. These flames are due to -the presence of natural gas and petroleum vapor that pass out through -the water. Large quantities of mud are thrown out from the craters of -these mud volcanoes. - -There are also many mud volcanoes in a district in India about 120 -miles northwest of Cutch near the mouth of the Indus. In this region -the cone built up around the crater is sometimes as high as 400 feet. - -The following description of mud volcanoes on Java is quoted from -Daubeny's book on volcanoes. - - "It would appear likewise from Dr. Horsfield's description, - that Java exhibits phenomena of a similar kind to those - noticed in Sicily and at the foot of the Apennines, and - there known under the name of 'Salses.' In the calcareous - district (which I suspect to belong to the same class - of formations as the blue clay and tertiary limestone - of Sicily) occur a number of hot springs, containing in - solution a large quantity of calcareous earth, which - incrusts the surface of the ground near it. Of these, some - are much mixed with petroleum, and others highly saline. - - "The latter are dispersed through a district of country - consisting of limestone, several miles in circumference. - They are of considerable number, and force themselves - upwards through apertures in the rocks with some violence - and ebullition. The waters are strongly impregnated with - muriate of soda, and yield upon evaporation very good salt - for culinary purposes (not less than 200 tons in the year). - - "About the centre of this limestone district is found an - extraordinary volcanic phenomenon. On approaching the - spot from a distance, it is first discovered by a large - volume of smoke rising and disappearing at intervals of a - few seconds, resembling the vapors arising from a violent - surf, whilst a dull noise is heard like that of distant - thunder. Having advanced so near that the vision was no - longer impeded by the smoke, a large hemispherical mass was - observed, consisting of black earth mixed with water, about - sixteen feet in diameter, rising to the height of twenty or - thirty feet in a perfectly regular manner, and, as it were, - pushed up by a force beneath, which suddenly exploded with - a dull noise, and scattered about a volume of black mud - in every direction. After an interval of two or three, or - sometimes four or five seconds, the hemispherical body of - mud or earth rose and exploded again. - - "In the same manner this volcanic ebullition goes on - without interruption, throwing up a globular mass of mud, - and dispersing it with violence through the neighboring - places. The spot where the ebullition occurs is nearly - circular and perfectly level; it is covered with only the - earthy particles impregnated with salt water, which are - thrown up from below; its circumference may be estimated - at about half an English mile. In order to conduct the - salt water to the circumference, small passages or gutters - are made in the loose muddy earth, which lead it to the - borders, where it is collected in holes dug in the ground - for the purpose of evaporation. - - "A strong, pungent, sulphurous smell, somewhat resembling - that of earth-oil (naphtha), is perceived on standing near - the site of the explosion, and the mud recently thrown - up possesses a degree of heat greater than that of the - surrounding atmosphere. During the rainy season these - explosions are more violent, the mud is thrown up much - higher, and the noise is heard at a greater distance. - - "This volcanic phenomenon is situated near the centre of - the large plain, which interrupts the great series of - volcanoes, and owes its origin to the same general cause as - that of the numerous eruptions met with in this island." - -There are, in many parts of the world, springs, whose waters issue -from their reservoirs at temperatures either at or near the boiling -point of water. These are called _hot_ or _thermal springs_. Hot -springs are found both in volcanic regions, as well as in regions -where there are no volcanoes, but where there are lines of deep -fissures or faults. According to Dana, in both of these classes, the -cause is to be traced to heat of volcanic or deep subterranean origin. -Hot springs are also found in regions where there are no volcanoes. -In these cases the heat is due to the gradual oxidation of various -sulphide ores, or to some other chemical action. - -The waters of hot or thermal springs almost always contain various -mineral substances in solution. All spring water contains some little -dissolved mineral matter, but in hot springs the quantity of this -matter is greater than in cold springs, because hot water can dissolve -mineral substances much better than can cold water. - -It might surprise you to hear that one of the commonest substances -that is found in solution in the waters of many hot springs is silica; -for silica is practically sand, and sand does not easily dissolve in -water as does sugar. The very hot water, however, which comes from -the hot spring, whose temperature below the earth's surface is very -much higher than it is when it comes out of the spring, possesses -the power of readily dissolving silica from the rocks over which it -flows. When the waters of such springs reach the surface the silica -is deposited in a solid condition around the outlets of the springs. -In this way there are built up craters or mounds, or, more correctly, -crater-shaped basins. - -Sometimes the hot water contains calcareous substances dissolved in -it, the solution being caused not only by reason of the hot water, but -also by means of the carbonic gas it contains. When this water flows -from the springs, it builds up the same crater-shaped mounds, only in -this case the mounds are of lime instead of silica. - -There are peculiar kinds of hot springs called _geysers_, that possess -the power of throwing huge streams of water up into the air at more or -less regular intervals. The word geyser is an Icelandic word meaning -to rage, or snort, or gush, the name being given by reason of the -manner in which the waters rush violently out during an eruption. - -As Dana points out, when the water in a basin of a hot spring merely -boils, whether this boiling is nearly continuous, or the water is -alternately boiling and quiet, the spring is called a hot or thermal -spring, but where the water is thrown violently out at more or less -regular intervals, it is called a geyser. - -The cause of the eruption of a geyser was discovered by Professor -Bunsen, the celebrated German chemist, after a careful study of -the geyser regions in Iceland. The waters of geysers contain large -quantities of either silica or lime in solution. Bunsen traced the -cause of these curious eruptions to be the manner in which the hot -springs pile up cones of silica or limestone around their mouths. - -The water of a geyser generally issues from the top of a more or less -conical hillock, reaching the surface through a funnel-shaped tube. -Both the tube and the basin are covered with a smooth coating of -silica or limestone. In the case of the Great Geyser in Iceland, the -basin is over fifty feet high and seventy-five feet deep. Both the -tube and the basin have been slowly deposited by the hot water of the -geyser. - -It is only when the tube of a geyser has reached a certain depth that -the geyser is able to erupt. Moreover, as soon as this tube passes a -certain depth the geyser can no longer erupt and forever afterwards -becomes an ordinary hot spring. There are, therefore, to be found in -most geyser regions, a number of what might be called young geysers or -merely hot springs, that are not yet deep enough to erupt; others that -have just commenced eruption, others that have reached their prime, -while others that, old and decrepit, have again merely become hot -springs. - -Let us now try to understand the cause of the eruption of a geyser. -Bunsen's explanation, which is now generally accepted, is as follows: - -The heat of the volcanic strata through which the tube of the geyser -extends, gradually raises the temperature of the water that fills -the geyser tube. Since the boiling point of a liquid increases with -the pressure to which it is subjected, far down in the tube of a -geyser, the pressure arising from the weight of the water above it is -sufficiently great to prevent the water from beginning to boil until -it reaches a temperature far higher than that at which it would boil -in the upper parts of the tube. Suppose now, when the water in the -funnel-shaped tube is nearly filled to the top, the water at last -grows hot enough to begin boiling at some point near the middle of -the tube. The pressure of the steam driven off from this portion of -the water raises the column of water above it in the tube and begins -to empty it out of the top of the geyser. All the water below this -point being thus suddenly relieved of its pressure, and being now much -hotter than is necessary to boil the water at that decreased pressure, -suddenly flashes into steam, and violently shoots out all the water -above it to a height that in some cases may be as great as 100 to 200 -feet. The steam causes this eruption, then rushes out with a roar, and -the geyser eruption is over. - -Professor Tyndall in his charming book entitled "Heat as a Mode of -Motion" speaks as follows concerning Professor Bunsen's discovery: - - "Previous to an eruption, both the tube and basin are - filled with hot water; detonations which shake the ground, - are heard at intervals, and each is succeeded by a violent - agitation of the water in the basin. The water in the - pipe is lifted up so as to form an eminence in the middle - of the basin, and an overflow is the consequence. These - detonations are evidently due to the production of steam in - the ducts which feed the geyser tube, which steam escaping - into the cooler water of the tube is there suddenly - condensed, and produces the explosions. Professor Bunsen - succeeded in determining the temperature of the geyser - tube, from top to bottom, a few minutes before a great - eruption; and these observations revealed the extraordinary - fact that at no part of the tube did the water reach its - boiling point. In the sketch [not reproduced] I have given - on one side the temperatures actually observed, and on - the other side the temperatures at which water would boil, - taking into account both the pressure of the atmosphere and - the pressure of the superincumbent column of water. The - nearest approach to the boiling point is at A, a height of - 30 feet from the bottom; but even here the water is 2 deg. C., - or more than 3-1/2 deg. F., below the temperature at which it - could boil. How then is it possible that an eruption could - occur under such circumstances? - - "Fix your attention upon the water at the point A, where - the temperature is within 2 deg. C. of the boiling point. Call - to mind the lifting of the column when the detonations - are heard. Let us suppose that by the entrance of steam - from the ducts near the bottom of the tube, the geyser - column is elevated six feet, a height quite within the - limits of actual observation; the water at A is thereby - transferred to B. Its boiling point at A is 123.8 deg., and - its actual temperature 121.8 deg.; but at B its boiling point - is only 120.8 deg., hence, when transferred from A to B the - heat which it possesses is in excess of that necessary to - make it boil. This excess of heat is instantly applied to - the generation of steam: the column is thus lifted higher, - and the water below is further relieved. More steam is - generated; from the middle downwards the mass suddenly - bursts into ebullition, the water above, mixed with steam - clouds, is projected into the atmosphere, and we have the - geyser eruption in all its grandeur. - - "By its contact with the air the water is cooled, falls - back into the basin, partially refills the tube, in which - it gradually rises, and finally fills the basin as before. - Detonations are heard at intervals, and risings of the - water in the basin. These are so many futile attempts at - an eruption, for not until the water in the tube comes - sufficiently near its boiling temperature, to make the - lifting of the column effective, can we have a true - eruption." - -The principal geyser regions of the world are in Iceland, in New -Zealand, and in the Yellowstone National Park in the United States. - -There are several geyser regions in Iceland. The best known lies in -the neighborhood of Mt. Hecla. Here is a great geyser that shoots up -a column of water to a height of about 100 feet every thirty hours. -Fig. 35 represents the appearance of the crater of the great geyser in -Iceland. - -[Illustration: FIG. 35. CRATER OF THE GREAT GEYSER OF ICELAND] - -It is a well-known fact that in geyser regions generally, the throwing -of stones or other materials into the tube will frequently hasten an -eruption. This is probably due to the fact that the throwing in of -these things results in the raising of the water in the tube, thus -hastening the eruption. - -The New Zealand region is in the neighborhood of Lake Rotomahama in -the northern island. - -The geyser region in the Yellowstone Park is by far the most -interesting of all geyser regions. This region is situated principally -around Fire-Hole Fork of the Madison, and near Shoshone Lake at the -head of Lake Fork of the Snake River. There are many geysers in this -region, as well as simple hot springs. The temperature of their -waters varies from between 160 deg. and 200 deg. F. to the boiling point of -water at this elevation. As you are probably aware, water boils at -the temperature of 212 deg. F. only under the condition of the ordinary -atmospheric pressure that exists at the level of the sea. At higher -elevations, such as on the slopes of mountains, or on high plateaus, -water boils at a lower temperature. The height of the country in which -the Yellowstone Park is situated is so great that the water boils at -temperatures of from 198 deg. to 199 deg. F. - -The conical hillock of geyser cones from which the waters flow assume -various shapes, two of which are shown in Figs. 36 and 37. - -[Illustration: FIG. 36. GIANT GEYSER _From Dana's Manual of -Geology_] - - -[Illustration: FIG. 37. BEE HIVE _From Dana's Manual of -Geology_] - -That shown in Fig. 36 represents the shape of the cone of the giant -geyser in the upper geyser basin of the Fire-Hole, Yellowstone -National Park. This cone is about ten feet in height, and twenty-four -feet in diameter. As shown in the figure it is broken on one of its -sides. It throws out, at long intervals, a column of water the height -of which varies from ninety to 200 feet. - -Fig. 38 represents the crater of a cone known as the Bee Hive in -eruption. - -Besides the above named geyser regions there is another region on the -shores of Celebes, and a small region on San Miguel, in the Azores -Islands, in the Atlantic Ocean. - -Besides hot springs and mud volcanoes there are two other phenomena -connected with volcanic action that we will now briefly describe. - -When eruptions take place and the lava begins to flow down the side -of a mountain, the different vapors and gases with which the lava is -charged begin to escape or pass out from the boiling or fused mass. -When these substances are of such a character that they produce fumes, -or the vapors of various chemical substances, that become solid on -cooling, they form what are called _fumaroles_, a word derived from -a Latin word meaning "to smoke." For the greater part, fumaroles are -found on the edge of craters, but sometimes are found in cavernous -places either in the crater or in the lava streams. - -There is, still, another class of openings through which only -sulphurous vapors escape. These are called _solfataras_, a word -derived from the Italian word _solfo_, or sulphur. Solfataras are -generally found in regions distant from volcanic action. In the -materials that escape from recently ejected lava, or molten lava, -the temperature is high enough to volatilize many of the solid -ingredients. But where the temperature is low, only sulphur vapors are -driven off. It is for this reason that fumaroles are only found around -the craters of active volcanoes, or on the lines of cracks or crevices -of the lava stream where the temperature is very high. - -[Illustration: FIG. 38. BEE HIVE GEYSER OF ICELAND _From -Dana's Manual of Geology_] - -Besides water vapor and sulphurous vapors there are other substances -that escape from the earth in volcanic districts. Sulphurous acid, -together with hydrogen and nitrogen escape from nearly all lava. At -Vesuvius chlorine gas is given off. This, however, as soon as it -passes into the atmosphere becomes changed into hydrochloric acid. -Sulphurous acid is frequently changed into sulphuric acid, which, -combining with various substances, forms such materials as _gypsum_, -or sulphate of lime, the chemical name for plaster of Paris; sulphate -of soda or _Glauber's salt_; sodium chloride or _common table salt_; -and _sal ammoniac_. You will remember in reading the description of -Vulcano, in the Grecian Archipelago, that some of these products were -collected at the chemical works that had been established on the -volcano. - -When a volcanic mountain is for the time being passing from an active -to an extinct condition, it is sometimes said to be in the _fumarole -stage_, since the presence of the fumaroles are the only indication -of its activity. The volcanic heat is still great. When it reaches a -still greater decline, the fumaroles disappear, and only solfataras -are left. The amount of heat is now only sufficient to produce sulphur -vapors and the vapor of water. This is called the _solfatara stage_. - -Of course, as we have already pointed out, fumaroles and solfataras -may occur in the neighborhood of a volcano at different distances from -its crater. - - - - -CHAPTER XXII - -THE VOLCANOES OF THE MOON - - -There can be no doubt that the moon was once the seat of very great -volcanic activity. It was formerly believed that the very many -volcanic craters which can be seen on its surface when it is examined -by a comparatively small telescope, were all extinct. While this -is nearly true, yet recent investigations have shown that in all -probability a feeble volcanic activity still exists in a few of these -craters. - -The distinctness with which the surface of the moon is seen does not -depend so much on the size of the telescope employed, as it does -on the steadiness of the atmosphere when the telescope is being -used. When one wishes to examine a very distant body like a star, -it is necessary to use a powerful telescope, but in the case of a -comparatively near body, like one of the planets or the moon, a big -telescope is not necessary. It is, however, necessary to make the -observations at some time of the year, or in some part of the world, -when the air is apt to be free from winds. - -A person on the earth's surface looking at the heavenly bodies through -a telescope is practically in the position in which he would be were -he at the bottom of the water in a large lake looking up through the -water at some body in the heavens. He would have no difficulty in -seeing such a body distinctly as long as the upper surface of the -water remained quiet, and unruffled by waves. As soon, however, as -waves were set up, the images seen in the telescope are so distorted -as to become practically worthless. It is for this reason that it is -customary to build great astronomical observatories in parts of the -world where there are apt to be many days in the year when the air is -almost entirely free from wind. - -Since the atmosphere is apt to be disturbed by winds in both the -temperate and the polar latitudes, these parts of the world are -not very satisfactory as sites for astronomical observatories. The -conditions are more favorable near the equator, since, although at -certain seasons of the year there are very severe storms in these -regions, yet there are quite long periods when the air is almost -entirely free from winds. - -It is for this reason that Harvard University has erected an -astronomical observatory at Arequipa, Peru, at an elevation of 8,000 -feet above the level of the Pacific Ocean. Here, with a comparatively -small object glass, of about twelve inches aperture, magnificent -photographs have been obtained not only of the moon but also of the -planet Mars. - -According to Professor Pickering, from whose magnificent work, -entitled, "The Moon," much of the information in this chapter has been -obtained, the moon, which is generally spoken of as a satellite of the -earth, ought rather to be called the earth's twin planet. Although the -moon appears to revolve in a small elliptical orbit around the earth -it should properly be said to revolve around the sun; for, together -with the earth, it revolves around the sun once every year. As seen -from any of the planets that lie near the earth the earth and moon -would appear as a very beautiful double star. - -In order the more readily to understand what will be said shortly -concerning the origin of the moon, it may be mentioned that the -moon's diameter is 2,163 miles, or a little more than one-fourth the -diameter of our earth. - -You will, most probably, be surprised to learn that the origin of the -moon is believed to be very different from the origin of the moons -or satellites of Jupiter, Saturn, and the other planets. As we have -already seen, according to the nebular hypothesis, all the planets -except the earth probably had their moons formed from the rings that -were left surrounding them when they shrunk on cooling to their -present dimensions. Such a ring is still to be seen surrounding Saturn. - -Now it is believed that our moon was formed in a different manner. -It was not thrown off from the earth while the latter was in a -highly fluid or gaseous condition, but after the earth had shrunken -to nearly its present size and, most probably, after a solid crust -had been formed on its surface. In order that our earth should be -able to violently throw off a large portion of its mass, it is only -necessary that at the time this separation occurred, its motion of -rotation on its axis was sufficiently great to enable it to make one -complete revolution in rather less than three hours instead of in -the twenty-four hours it now requires. At this velocity of rotation, -objects would fly off the earth in the neighborhood of the equator, -under the influence of the high centrifugal force. Let us, then, -endeavor to see if it was at all probable that the earth ever did turn -so rapidly on its axis. - -You all probably know that it is principally the attraction of the -moon that produces the earth's tides. Of course, the sun also produces -tides on the earth, but it is so far off from the earth that not -withstanding its greater mass the tides it forms are much smaller -than those produced by the moon. You also know that the moon produces -at the same time two tides in every twenty-four hours, on directly -opposite sides of the earth; one on the side immediately under the -moon, and the other on the side furthest from the moon. As the earth -rotates between these two tides, they act as a break which serves to -impede its motion. Every high tide, therefore, tends to make the earth -rotate more slowly, and thus to slowly increase the length of the day. -For this reason to-day is a trifle longer than yesterday, and still -longer than a day a hundred years ago. - -You must not suppose for a moment that this increase in the length of -the day is large. On the contrary, it is so small that since the year -A. D. 1, up to the present time, the day is only a very small -fraction of a second longer. - -But it was very different in the earth's geological past, when the -inside of the earth was in a molten condition; for then great tides -were set up in the melted interior of the earth that not only greatly -changed the shape of the earth, but decreased the rate of rotation -much more rapidly than it does when the earth's tides are limited as -they are now to the waters on the earth's surfaces. - -There was, however, at the same time, something going on that tended -greatly to make the earth turn more rapidly on its axis. While the -originally melted earth was cooling and shrinking, the rate of -its rotation was necessarily increasing. As you know, the time of -vibration of a pendulum, that is, the time it requires to make one -complete to-and-fro motion, is shorter the shorter the length of the -pendulum. A pendulum two feet long moves to and fro more slowly than -a pendulum one foot in length. In the same way a rotating sphere will -make one complete rotation in a shorter time when its radius, which -corresponds to the length of a pendulum, is shorter. Therefore, as the -earth shrunk, it rotated more and more rapidly, and at last reached a -rapidity of motion at which an immense quantity of matter flew off -its surface nearest the equator and went out into space, never again -to return. It was this mass that constituted the earth's moon. - -Necessarily such a tremendous catastrophe was attended by an -earthquake as well as by the most fearful volcanic phenomena that -the earth has ever witnessed. The terrible catastrophe produced by -the explosive eruption of Krakatoa was but as a small drop of rain -falling on the earth, when compared with the catastrophe produced when -the "five thousand million cubic miles of material left the earth's -surface, never again to return to it." - -It is not known whether this matter was torn off the earth at a single -time or during successive times, but quoting the beautiful language of -Professor Pickering: - - "We may try in vain to imagine the awful uproar and fearful - volcanic phenomena exhibited when a planet was cleft in - twain, and a new planet was born into the solar system." - -This terrible catastrophe took place at a time not when the earth was -a gaseous mass, but when it had condensed into a comparatively small -mass not much larger than it is at its present time, and possibly -even after it had hardened sufficiently to form a solid crust on its -outside. - -If you look at a map of the earth on a Mercator's projection, such, -for example, as that employed in illustrating the distribution of the -world's volcanoes in Fig. 24, you can see, even without any very close -examination, that the great water area of the Atlantic Ocean has its -eastern and western shores almost parallel to each other, so that -if you conceive the Eastern and Western Continents as being pushed -together, they would, except at the south, almost completely fit -together, and the same thing is true, if Greenland is pushed towards -the northeastern coast of North America. Of course, some portions of -the coast would not fit exactly, but then these portions might either -have been worn away, or, as is more probable, have been changed in -shape by the deposit of immense beds of sedimentary rocks spread over -the borders of the Atlantic by the great rivers that empty into it. -This is so remarkable a fact that it will be well worth your while to -turn to the map mentioned and convince yourself of the proof of what -I have just said. As you will see, Europe and Africa would almost -exactly fit against South America and North America, while Greenland -would even more closely fit against the northeastern coast of North -America. - -Now, while we do not say that it was so, it has been suggested as just -possible that the great depression of the Pacific Ocean represents the -spot that was once filled by the moon. That the Eastern and Western -Continents, then torn asunder by the great force of the convulsion, -were left floating on the surface of a sea of molten matter, a greatly -widened crack marking positions they assumed at the end of this -cataclysm. - -Of course, you must understand that all this is a mere supposition, -and that we do not know whether the earth was actually cooled on the -outside when this occurred, since it might have still been in a liquid -condition throughout. It would seem, however, to have occurred rather -recently, since it could not have occurred until the earth shrunk so -much that it became so small in radius as to acquire a very rapid rate -of motion on its axis. - -It is an interesting fact that we are, perhaps, better acquainted with -that side of the moon which is turned towards us than we are with the -surface of the earth on which we live. Of course, I do not mean in the -small details of the moon's surface, but with such portions as can be -seen through a good telescope when the air is quiet. While there are -no parts of the moon's surface that have not been carefully examined -in detail probably thousands of times by acute astronomers, there are -still comparatively large areas of the earth that have never been once -trodden by civilized man. - -When I speak of all parts of the moon's surface, I only mean those -parts that are turned towards us. You may possibly be ignorant of the -fact that the moon always turns exactly the same face towards the -earth. Not only has no man ever seen the opposite side of the moon, -but he never can hope to see it while he remains on the earth. This is -because the moon turns or rotates on its axis in exactly the same time -that it revolves in its orbit. - -When I say that the time of rotation is the same as the time of -revolution of the moon, I do not mean that it is almost the same, but -that it is exactly the same. If it differed even but a small fraction -of a second, a time would come when we would be able to see the other -side of the moon. Now, since astronomers have made careful pictures -of the moon, many, many years ago, we can see by comparing them -with photographs taken at the present time there has been no change -whatever in that face of the moon which is turned towards us, and -this, of course, proves beyond question, that the time of the moon's -rotation during this great period has remained exactly the same as the -time of its revolution. - -It may possibly seem to you that it cannot be a matter of great -importance in a book like this on the Wonders of Volcanoes and -Earthquakes, whether or not the moon always turns its face towards -the earth; on the contrary, it is a matter of the greatest importance -since by it we can prove positively that the moon was at one time at -least in a partly fluid condition. It was the presence of this partly -fluid interior that resulted in the time of the moon's rotation -agreeing exactly with the time of its revolution. The tides of the -earth set up in the moon's molten interior, tides, that instead of -reaching twice every day the height of a few feet only, were set up -in the molten mass in the moon's interior, probably reaching miles in -height, rapidly decreased the time of the moon's rotation until the -moon rotated once only during every complete revolution. - -Even now that the moon is probably solid throughout, the time of its -rotation and revolution exactly agree because, while in a molten -condition, the action of the earth changed its shape from that of an -exact sphere to a spheroid, with its longest axis in the direction of -the earth. Even, therefore, if the moon at any time began to rotate -faster than the earth, the earth acting on its projecting surface -retarded it until the time of its rotation agreed exactly with the -time of its revolution. - -It was at one time believed that the moon had no atmosphere. It is -now known, however, that it has an atmosphere. It is true this is a -rare atmosphere, probably not greater in density than the one-ten -thousandth of the earth's atmosphere. This important question was -settled once for all on August 12th, 1892, at the Harvard Observatory -at Arequipa, Peru, when a photograph was taken of an object on the -moon. It could be readily seen on examining this photograph that the -light coming from the moon experienced a bending, known as refraction, -in passing from the space outside the moon to its atmosphere on to its -surface. - -Of course, when the moon was thrown off from the earth by reason of -its great centrifugal force, it carried along with it a portion of the -earth's atmosphere. But since the quantity of matter in the moon is -only about one-eightieth of that of the earth, the force of gravity -on the moon is much smaller than that on the earth, being almost -exactly one-sixth that of the earth's gravity. In other words, if you -could succeed in reaching the moon's surface, you would only weigh -one-sixth of what you weigh on the earth, but then you could carry a -weight six times heavier with no greater effort, and, as for running, -jumping, and other athletic exercises, the surface of the moon would, -indeed, be a great place on which to break records, since one could -readily jump six times higher, put the shot six times further, than -on the earth, or go through most other athletic exercises with a -corresponding increase. - -Without going any further into this question it will be sufficient -to say that the moon's present atmosphere is believed to consist of -carbonic acid gas, and that while on the general surface of the moon -this atmosphere must be very rare, yet, at the bottom of the great -fissures that cross the moon's surface, it may possess a fairly great -density, especially if the moon still possesses feeble volcanic -activity; that carbonic acid gas is still being given off from the -inside of the moon as we know it is being given off from inside the -earth. - -Under the best conditions of atmosphere and telescope, we can see the -moon's surface as it would appear at a distance varying from 800 miles -to 300 miles from the earth. With a fifteen-inch telescope, under -perfect conditions of vision, objects can be seen as if they were at -a distance of 800 miles from the earth, and with the most powerful -glasses, and the best conditions of atmosphere this distance can be -reduced to about 300 miles. This would enable us to clearly see large -objects like rivers, lakes, seas, or forests, if they existed, but -would not be sufficient to enable us to see houses, buildings, or -roads. - -When we come to examine the surface of the moon under the most -favorable conditions, we find that it is extremely irregular. There -are plenty of high mountains. These mountains are not collected -in ranges as they are on the earth's surface, but are completely -separated from each other, and are scattered in great numbers over the -moon's surface. - -You may form some idea of the number of volcanoes that have been -observed on the moon when I tell you that as many as 32,000 have been -seen on that side of the moon that is turned towards the earth. - -Now it is an interesting fact that almost all these mountains possess -great craters that are not unlike some of the volcanic craters we see -on the earth. The volcanic craters of the moon, however, are of very -much greater size than those on the earth, many being from fifty to -sixty miles in diameter, while some of them are more than 100 miles -in diameter. Smaller craters, say from twenty to twenty-five miles in -diameter, can be counted by the hundreds. - -Like most of the moon's craters, the largest crater more closely -resembles one of the pit-craters or calderas on the island of Hawaii. -This volcanic crater consists of a huge circular ring with a small -irregular peak that rises inside the ring. This peak, by the way, -might at first appear to resemble the crater of Vesuvius, which after -a long period of inactivity of the mountain during the eruption that -destroyed Pompeii and Herculaneum was thrown up inside of what had -been left standing of the old crater of Somma. But it has no crater -at its summit, and, therefore, resembles rather the irregular pile or -rock that rises from the surface of a lava lake in the craters of Mt. -Loa or Mt. Kilauea in Hawaii. - -Besides the numerous craters to be seen on the moon's surface there -are many lines of deep, crooked valleys, known as _rills_, that may -at one time have been the beds of rivers. Besides the rills, there are -many straight clefts about half a mile in width, that extend down into -the surface of the moon for unknown depths. These clefts can be seen -passing directly through mountains and valleys. They are believed to -be cracks or fissures in the moon's surface. - -On the moon is a great crater called Tycho. It is situated near the -moon's south pole. The great crater of Tycho is by far the most -prominent object on the moon's surface. It has a system of rays that -extend for great distances around its craters. - -You will also see if you examine the moon's surface by a powerful -glass that there are immense plains called _oceans_ or _seas_. By an -appropriate custom the names of the different craters on the moon are -the same as the names of the great astronomers and philosophers that -have long since passed from their labors, such as Tycho, Copernicus, -Kepler, Plato, etc. - -Various explanations have been given as to the origin of the craters -on the moon's surface, but without going into a discussion it may be -said that they are now generally regarded as having been formed in the -main just as were the craters of the earth's volcanoes. - -The tremendous size of the moon's craters is of course due to the -great decrease in the force of gravity. This would make the craters, -approximately, six times as great as the craters on the earth. -Professor Pickering points out that while the moon's craters resemble -more closely those of Hawaii than those of any other of the earth's -volcanoes, yet there is this difference in them: that while the -earth's crater floors are generally considerably higher than the level -of the sea, the moon's crater floors are generally below the level of -the surrounding country. Still, taking them all in all, the craters -of the moon's volcanoes resemble those of the island of Hawaii, or -again quoting from Pickering:-- - - "There seems, indeed, to be no feature found upon the moon - which is not presented by these Hawaiian volcanoes, there - is no feature of the volcanoes that does not also have its - counterpart in the moon." - - - - -CHAPTER XXIII - -EARTHQUAKES - - -An _earthquake_ is a shaking of the earth. It may vary in intensity -from a shaking so feeble that it requires the use of a delicate -instrument to detect it, to a shaking violent enough to overthrow -heavy buildings, and even to make great rents or fissures in the crust. - -An earthquake then is an _earth-shake_. It may be caused by anything -capable of shaking the earth; for example, as the falling of a heavy -weight on its surface. Now, a shaking so caused is only felt in the -immediate neighborhood of the place the weight strikes the earth. On -the contrary, in an earthquake, the shaking spreads in all directions -through the earth's crust, until, in the case of very violent -earthquakes, it reaches portions that may be situated many thousands -of miles away from where the shock started. This spreading of the -earthquake waves through the solid earth is not unlike the spreading -of the circular waves that are set up in a still water surface when a -stone is tossed in. - -Any shaking of the earth's crust produces what may be called an -earth-shake or earthquake. The mere falling of a raindrop on the earth -produces a slight shaking. The falling of a heavy stone produces a -stronger shaking, and sets up a series of minute waves, generally -called vibrations, that spread around the place in all directions from -where the stone struck. These movements, however, while they spread -in all directions, just as they do in a surface of a lake, when a -stone is thrown into it, are of course much more quickly stopped by -the solid earth than similar movements are by the more readily movable -water. - -But, while any shaking of the earth's crust constitutes an earthquake, -yet, strictly speaking, an earthquake is produced only by some force -that acts suddenly on the earth, _at a point below its surface_, and, -therefore, out of sight. This, of course, would rule out all such -shakings as are caused by bodies striking the outer surface of the -earth. - -Earthquakes may occur in any part of the world, and at any time of the -day or year. They do occur, however, most frequently in certain parts -of the world, at certain seasons of the year and at certain hours of -the day. - -Earthquakes are far from being unusual occurrences. In some parts of -the world, such as the island of Java, they are very common, and in -Japan, under certain circumstances, scarcely a day passes without one -or more shocks in some part of that little empire. - -Professor Mallet, who has made a very extensive study of earthquakes, -published in 1850 to 1858, in the Philosophical Transactions, brief -abstracts or descriptions of all the more important earthquakes he -could find records of during the past 3,456 years. The number of -earthquakes thus recorded during this period reached 6,830. Of this -great number nearly one-half occurred during the last fifty years. - -It should not be inferred from the above figures that the number of -earthquakes has really increased so greatly in the past half-century. -The explanation of the apparent increase is that greater care has -been taken recently in recording earthquakes, and that an apparatus -called a _seismometer_, or _earthquake-recorder_, has been invented -which automatically produces a record of the smallest shocks; so that -a great many have been recorded that would otherwise have passed -undetected. - -It is the opinion of Le Conte that if the records of all the -earthquakes of 3,456 years had been thus made there would have been -found during the entire time of Mallet's researches to have occurred -no less than 200,000, while during the last four years of Mallet's -records, the number would have probably reached two earthquakes per -week. - -Since Mallet's time, Prof. Alexis Perry published (1876) a much larger -list of earthquakes. Perry finds that from 1843 to 1872 there have -been 17,249 earthquakes, or 575 every year. Perry's list, however, -is incomplete, since it fails to record earthquakes that occurred in -mid-ocean, and in the unexplored and uncivilized parts of the world. -So it seems likely that earthquakes are so common that our earth, at -some part or other of its surface, is continually shaking or quaking. - -Earthquakes are such tremendous phenomena that they were necessarily -observed by the ancients. We find more or less complete accounts of -them in various writings. Lucretius (Titus Carus Lucretius, a great -Roman poet) speaks as follows, in his De Rerum Natura (On the Nature -of Things). We use Munro's translation here: - - "Now mark and learn what the law of earthquakes is. And - first of all take for granted that the earth below us as - well as above is filled in all parts with windy caverns, - and bears within its bosom many lakes and many chasms, - cliffs and craggy rocks; and you must suppose that many - rivers hidden beneath the crust of the earth roll on with - violent waves and submerged stones; for the very nature - of the case requires it to be throughout like to itself. - With such things then attached and placed below, the - earth quakes above from the shock of great falling masses, - when underneath, time has undermined vast caverns. Whole - mountains, indeed, fall in, and in an instant from the - mighty shock tremblings spread themselves far and wide from - that centre. And with good cause, since buildings beside - a road tremble throughout, when shaken by a wagon of not - such very great weight; and they rock no less, where any - sharp pebble on the road jolts up the iron tires of the - wheels on both sides. Sometimes, too, when an enormous mass - of soil through age rolls down from the land into great - and extensive pools of water, the earth rocks and sways - with the undulation of the water just as a vessel at times - cannot rest, until the liquid within has ceased to sway - about in unsteady undulations.... - - "The same great quaking likewise arises from this cause, - when on a sudden the wind and some enormous force of air - gathering either from without or within the earth have - flung themselves into the hollow of the earth and there - chafe at first with much uproar among the great caverns - and are carried on with a whirling motion, and when their - force, afterwards stirred and lashed into fury, bursts - abroad and at the same moment cleaves the deep earth and - opens up a great yawning chasm. This fell out in Syrian - Sidon and took place at AEgium in the Peloponnese, two towns - which an outbreak of wind of this sort and the ensuing - earthquake threw down. And many walled places besides fell - down by great commotions on land and many towns sank down - engulfed in the sea together with their burghers. And if - they do not break out, still the impetuous fury of the - air and the fierce violence of the wind spread over the - numerous passages of the earth like a shivering-fit and - thereby cause a trembling." - -Of course, no one at the present time believes this ridiculous -explanation as to the cause of earthquakes. - -Aristotle, a Greek philosopher, speaks thus concerning earthquakes. We -quote the translation employed by Mallet: - - "Three theories on the subject have been handed down to - us by three different persons; namely, Anaxagoras of - Klazomene, before him Anaximenes the Milesian, and later - than these Democritus of Abdera. - - "Anaxagoras says that the ether of nature rises upward, but - that when it falls into hollow places in the lower parts - of the earth it moves it (the earth); because the parts - above are cemented or closed up by rain, all parts being by - nature equally spongy or full of cavities, both those which - are above (where we live) and those which are below. Of - this opinion it may perhaps be unnecessary to say anything, - as being foolish, for it is absurd to suppose that things - would thus exist above and beneath, and that the parts of - bodies which have weight would not on every side be borne - to the earth, and those which are light, and fiery, rise; - especially since we see the surface of the earth to be - convex and spherical, the horizon constantly changing as - we change our place, at least as far as we know. And it is - also foolish to assert on the one hand that it remains in - the air on account of its great size, and on the other to - say that it is shaken, when struck from beneath upwards. - And besides these objections, it is to be remarked that - he has not treated of the attendant circumstances of - earthquakes, for neither every time nor place is subject to - these convulsions. - - "But Democritus says, that the earth being full of water, - and receiving much also by means of rain, is moved by - this. For when the water increases in bulk, because the - cavities cannot contain it, in its struggles it causes an - earthquake. And when the earth becomes partially dried up, - the water being drawn from the full reservoirs into those - which are empty, in passing from one to the other, by its - movements it causes an earthquake also. - - "Anaximenes, however, says that the earth, when parched up - and again moistened, cracks, and by the masses thus broken - off falling on it, is shaken; wherefore earthquakes occur - in drouths and again in times of rain; in drouths, because, - as we have said, it cracks, when highly dried, and then, - when moistened over again, it cracks and falls to pieces. - Were this the case, however, the earth ought to appear - in many places subsiding. Why then is it that hitherto - many places have been very subject to these convulsions - which do not present any such remarkable differences from - others? Yet such ought to be the case. And, moreover, those - who think thus must assert that earthquakes constantly - become less and less, and at last cease altogether. For - the continual condensation of the earth would cause this. - Wherefore, if this be not the fact, it is plain that this - is not the correct explanation." - -Besides the above, there are numerous references to earthquakes in the -works of other writers. Thales, Seneca, and Pliny all speak of these -phenomena and appear to describe correctly the movement of the earth -in waves both in the solid land, as well as on the sea. - -Coming down to less ancient writers, Mallet refers to a book by -Fromondi, published in Antwerp, in 1527, that contains much valuable -and interesting information. Among other things Fromondi declares -that in the year 369, in the reign of Valentinian, there was a great -earthquake that shook nearly the entire world and that another -earthquake of almost equal severity occurred in 1116. He also states -that in 1601 an earthquake continued for nearly forty days; that a -great earthquake in Italy, in 1538, lasted fifteen days, and that -another, in Spain, lasted for nearly three years. - -This does not mean that these earthquakes actually continued to shake -the earth violently for the times mentioned. These are only the times -during which, at intervals of greater or less length, successive -shocks were felt in these localities. - -Another of the less ancient writers referred to by Mallet is -Travagini, who published a book in Venice in 1683. This book contains -a description of a terrible earthquake occurring in Italy on the 6th -of April, 1667, which affected large portions of the country adjacent -to Ragusa. - -Without attempting at present to discuss the various theories of -earthquakes, it will suffice to say that earthquakes can be divided, -according to their origin, into two classes: _volcanic earthquakes_, -or earthquakes that are caused by practically the same forces that -cause volcanoes, and _tectonic[3] earthquakes_, or those produced by -the slipping of a large mass of rock lying along the lines of old or -new fractures. - -Earthquakes of the first class are found especially in volcanic -districts, while those of the second class are found in all parts -of the world, whether in volcanic districts or elsewhere. According -to Dana, earthquakes of the second class generally start in the -neighborhood of mountains, where old lines of fractures are especially -abundant. - -As regards the direction of the shaking movements of the earth, -earthquakes can be divided into three different classes: _explosive -earthquakes_, or those in which the force acts vertically upwards; -_horizontal earthquakes_, or those in which the force moves in a more -or less horizontal direction, or parallel to the general surface -of the earth, and _rotary earthquakes_, or those in which the earth -rotates or moves in great eddies or whirls. - -When the earthquake wave is started below the earth's surface, it -spreads through the crust in all directions. The direction these waves -will have on emerging, or coming out of the surface, will depend on -the distance of this point from the place the waves started. When a -place is situated directly over where the wave started, the waves will -emerge so as to move vertically upwards, so that the earth at this -point will be shaken by an explosive earthquake. As the point where -the waves pass out is situated further and further from the place -where the waves start, the waves will emerge more nearly horizontally, -the greater the distance from the source. - -In explosive earthquakes, which, as just explained, occur at areas -almost immediately above the point where the disturbance starts, -the force is, generally speaking, the greatest. In earthquakes of -this character the force is sometimes sufficiently great to throw -large bodies high up into the air. In the case of the great Riobamba -earthquake of 1797, the force was not only sufficiently great to -fracture the earth in various places, but also to throw bodies lying -on the surface great distances into the air. Bodies of men were thrown -several hundred feet into the air and were afterwards found on the -other side of a broad river or high up on the side of a hill. - -It is possible that Humboldt did not inquire with as much care as -he should have done into these reports. They were probably greatly -exaggerated, since it is difficult to understand how a force great as -this would have failed to detach the soil at these places, and hurl it -after the people. This much, however, can be accepted, that the upward -force was very great. - -In the great Calabria earthquake of March, 1783, Dolomieu states that -the tops of the granite hills of Calabria were distinctly seen to rise -and fall. In some cases houses were suddenly raised a great distance -in the air, and were afterwards brought down again to a position of -rest, at a higher level without any damage occurring to them. In a -similar manner during the Caracas earthquake of March, 1812, the -ground was seen to rise and fall in a nearly vertical direction. But, -perhaps, one of the most terrible earthquakes of this character was -the earthquake that destroyed the greater part of Jamaica in June, -1793. During this earthquake the entire surface of the ground at Port -Royal assumed the appearance of a rolling sea. Houses were shifted -from their old sites. Many of the inhabitants who had succeeded in -escaping from the city to the neighboring country were thrown great -distances into the air. Some of these, by good fortune, fell into the -harbor, from which, in some cases, they escaped with their lives. Here -again the projectile force was probably greatly exaggerated. - -Vertical movements characterized the great earthquake of Lisbon, on -November 1st, 1755, the city appearing to have been not far from the -point of origin. - -The commonest type of earthquakes is the horizontal, where the waves -emerge at the surface in a direction either horizontal or parallel -to the general surface, or at least inclined to it at a very small -angle. Where the materials of the earth's crust, through which the -waves spread, are of the same kind and of the same density in all -directions, the area shaken is approximately circular, but where the -materials of the crust are more or less dense in some directions than -in others, the area of disturbance is of course oblong or elliptical. - -In some cases earthquakes of the horizontal type are limited almost -entirely to a single direction. This is especially the case with -earthquakes that occur in mountainous districts. These earthquakes are -known as _linear earthquakes_, since they spread almost in a single -line. - -When earthquake waves pass from one medium to another, that is, from -one kind of rock to another, the greater portion of the waves is -refracted or bent out of their straight direction as they pass into -the new medium; a part of the waves, however, are reflected. It is -these reflected waves that probably cause rotary earthquakes. - -The speed with which the surface waves move outwards in all -directions, varies not only with the force of the wave, but also with -the kind of material through which they pass. This velocity may be -in the neighborhood of twenty miles per second, while in others the -velocity is as great as 140 miles per second. - -Naturally, one would suppose that the most severe earthquakes are -those in which the waves move the most rapidly. On the contrary, -however, the comparatively feeble shocks are sent through the earth -with greater velocity. - -In rotary earthquakes, as the name indicates, the ground is whirled -or twisted in the manner of a violent eddy, and is often left in -this twisted condition. In the great Calabria earthquake, huge -blocks of stone forming obelisks were twisted on one another in a -manner represented in Fig. 39. In this case the pedestals remained -unaffected, but the separate blocks of stone were partially turned -around, as shown. During this earthquake the earth was so twisted that -trees, which had been planted in straight lines before the earthquake, -were left standing in zigzags. During the great Charleston earthquake, -South Carolina, the chimney-tops of the houses were separated at -places where they joined the roof and were twisted around these places -without being overthrown. In some of the houses wardrobes or bureaus -were turned at right angles to their former positions, and in some -cases were even found with their faces turned towards the wall. - -[Illustration: FIG. 39. HEAVY STONE OBELISKS TWISTED BY CALABRIAN -EARTHQUAKE OF 1783] - -Mallet suggests that in some cases the rotary motion is more apparent -than real, being due only to a to-and-fro motion without any twisting, -the apparent turning being due to the greater freedom of motion of the -object in one direction than in another. A twisting motion, however, -has actually taken place in some earthquakes. - -While separate shocks, in a given locality, may follow one another -at intervals for fairly long times, yet the principal shock or shake -that produces the greatest damage is generally of exceedingly short -duration. In the Caracas earthquake the greatest destruction was -accomplished in about one minute. There were three distinct shocks, -each of which lasted but three or four seconds. The great Calabria -earthquake, of 1783, lasted but two minutes. The earthquake of Lisbon, -in 1755, lasted five minutes, but the first, and worst, shock, was -only from five to six seconds. - - - - -CHAPTER XXIV - -SOME OF THE PHENOMENA OF EARTHQUAKES - - -The nature of an earthquake and the movements of its waves from -their starting place having now been briefly described, it remains -to explain some of the strange phenomena that precede, accompany, or -follow one. - -Next to the violent shaking of the earth's crust, perhaps the most -wonderful and impressive thing is the great variety of sounds and -noises. These occur not only while the earth-waves are passing through -the crust at any place, but also long before the principal shocks -reach the place, as well as long after they have passed. - -Earthquake sounds vary almost infinitely, both in intensity and -character. Some are like the gentle sighings of the wind, or resemble -faint mysterious whisperings; some are not unlike the confused -murmurings of a crowded room; some resemble the sounds of a busy -street. Some sounds are full and strong, like the deep bass notes -of a large organ. Others resemble the din of a great battle with -the reports of the large guns. Still others reach the intensity of -continuous peals of thunder. But we can better understand the nature -of earthquake sounds from an actual description of them in a number of -great earthquakes, and by inquiring at the same time into any of the -peculiar facts connected. - -Humboldt in his great work, "Cosmos," thus describes the varied voice -of the earthquake: - - "It is either rolling or rustling, or clanking, like - chains being moved, or like near thunder, or clear and - ringing, as if obsidian or some other vitrified masses were - struck in subterranean cavities." - -That the sounds produced during earthquakes are carried through the -ground faster than through the air appears clear from the fact that -such sounds are sometimes heard in deep mines when they are not at all -heard on the earth's surface. - -In describing the earthquake that occurred in Kamtschatka, in 1759, -Krashenikoff of St. Petersburg states that noises were heard like the -rushing of a strong underground wind, accompanied by a hissing sound, -which resembled the sizzlings heard when red hot coals are thrown in -water. - -In an earthquake that occurred in Lincolnshire, England, February -6th, 1817, a noise was heard closely resembling the sounds of wagons -running away on a road. So complete and convincing was the resemblance -that several wagoners on one of the roads drew their teams to one side -so as to permit the runaway to pass safely. - -Another kind of noise heard during earthquakes is a loud hollow -bellowing. Sometimes, however, the sounds are more musical in their -nature, being not unlike those produced by a very large organ pipe. At -other times they resemble the noises produced when steam is blown into -cold water. - -The following account of earthquake sounds is given by Daubeny, -in his book on volcanoes. It appears that during March, 1822, the -people living on the island of Melida, opposite Ragusa, in Dalmatia, -were greatly alarmed by sounds that at first they believed due to -cannonading either at sea or on the neighboring coast. They afterwards -found that these sounds were due to something that was taking place -under the ground. The noises continued at intervals until August -23d, 1823, when a great earthquake occurred, during which one of the -highest mountains on the island was cleft or split in one place. The -underground noises continued from time to time and so frightened -the people that they were about to leave the island permanently and -emigrate to the mainland of Dalmatia. They were dissuaded from doing -so by the government, and while the noises continued at intervals it -so happened that no damage came to them. It is said, however, that -twenty years after an active volcano broke out on the island. - -There are various causes that produce earthquake sounds. A very slight -rubbing or grinding together of rock surfaces may produce fairly -loud noises, the volume of the sound being increased by transmission -through the rock masses that lie in the path of the waves. An example -of such an increase in the loudness of sounds is seen in the case of -several of the large blocks of stone used for some of the piers of -Kingston Harbor, in Ireland. When these rocks are moved together by -blows of the waves they produce loud and appalling sounds, as if the -whole island were being washed away. The same rocks, however, when -left high and dry on the falling of the tide, can be caused to rub -together, when moved by the hand. Under these circumstances, they -produce but feeble sounds that can only be heard in their immediate -neighborhood. - -No doubt, some find it difficult to understand how it is possible for -comparatively feeble sound-waves to be strengthened by their passage -through large masses of solids. This is important and should be made -clear. As everyone well knows, the ticking of a watch can only be -heard at a short distance when the watch is held in the hand, because -the sound-waves cannot readily pass through the body of the person -holding the watch to the earth, the materials of the body not being -sufficiently elastic. If, however, the watch be placed on the bare -surface of a large wooden table from which the tablecloth has been -removed, so that the watch can come directly in contact with the wood, -and nothing else is placed on the table but the watch, the sound-waves -are transmitted to the mass of the table and its entire surface sends -them out into the air. The ticking of the watch can then be heard -distinctly in almost any part of a large room. - -Mallet states that in nearly all great earthquakes sounds are heard -before the principal shock, and in his description of the Calabrian -earthquake Hamilton says: - - "All agreed that every shock seemed to come with a rumbling - noise from the westward, beginning with the horizontal and - ending with the vorticose (rotary) motion." - -According to Dolomieu, during the Lisbon earthquake, the shocks were -preceded "by a loud subterranean noise like thunder, which was renewed -for every shock.... This great shock," he says, referring to one of -the great upward shocks, "occurred without the prelude of any slight -shocks, without any notice whatever as suddenly as the blowing up of -a mine.... Some, however, pretend that a muffled interior noise was -heard almost at the same moment." - -The noises do not generally continue long after the earthquake shocks. -In some cases, however, a very loud noise is heard at intervals for a -considerable length of time after the principal shock. This was the -case at Quito and Ibarra, in which a great noise was heard for from -eighteen to twenty minutes after the principal shock. In a similar -manner during the earthquake of October, 1746, at Lima, and Callao, -South America, peals of underground thunder were heard at Truxillo -for fifteen minutes after the principal shock. In such cases it -seems probable that the noises were not caused by the same impulses -that caused the original shock, but by the forces that caused the -subsequent shock. - -Humboldt relates that in 1784 there were noises heard at Guanajuato, -from the 9th to the 12th of February. They were not, however, followed -by an earthquake. - -Humboldt also states that in an earthquake which occurred on the 30th -of April, 1812, on the banks of the Orinoco River, in South America, -a loud thundering noise was heard, without, however, any shock, but -at this time a volcano on the island of St. Vincent, in the Lesser -Antilles, although some 632 miles to the northeast, was pouring out -streams of lava. Again in the great eruption of Cotopaxi, in 1734, -underground noises were heard as if cannon were being fired. These -sounds were distinctly heard at as great a distance as Honda on the -banks of the Magdalena River. Now, bearing in mind that the crater of -Cotopaxi is situated on the high plateau of Quito, in a region full -of valleys and fissures, it would seem that for the sounds to have -been sent through the 436 miles between the mountains and the valley -of the Magdalena River, the waves must, for the greater part, have -been transmitted through the solid earth at some considerable distance -below the surface. - -Mallet states that the underground noises which continued for more -than a month from the midnight of January 9th, 1784, at Guanajuato, -were not followed by any earthquake shocks, that it was if as thunder -clouds occupied the space below the surface at that part of the earth -and from these clouds there came the slow rolling sounds like short, -quick, snaps of thunder. - -Major Dutton in his book entitled "Earthquakes in the Light of the -New Seismology" gives the following as the principal signs that herald -the coming earthquake in the open country. - - "The first sensation is the sound. It is wholly unlike - anything we have ever heard before, unless we have already - had a similar experience. It is a strange murmur. Some - liken it to the sighing of pine-trees in the wind, or to - falling rain; others to the distant roar of the surf; - others to the far-off rumble of the railway train; others - to distant thunder. It grows louder. The earth begins to - quiver, then to shake rudely. Soon the ground begins to - heave. Then it is actually seen to be traversed by visible - waves somewhat likes waves at sea, but of less height and - moving much more swiftly. The sound becomes a roar. It is - difficult to stand, and at length it becomes impossible to - do so. The victim flings himself to the ground to avoid - being dashed to it, or he clings to a convenient sapling, - or fence-post, to avoid being overthrown. The trees are - seen to sway sometimes through large arcs, and are said, - doubtless with exaggeration, to touch the ground with - their branches, first on one side, then on the other. As - the waves rush past, the ground on the crests opens in - cracks which close again in the troughs. As they close, the - squeezed-out air blows forth sand and gravel, and sometimes - sand and water are spurted high in air. The roar becomes - appalling. Through its din are heard loud, deep, solemn - booms that seem like the voice of the Eternal One, speaking - out of the depths of the universe. Suddenly this storm - subsides, the earth comes speedily to rest and all is over." - -There are many other curious phenomena besides earthquake sounds or -noises. Among some of the more interesting are the fire and smoke that -are seen to come out of fissures that have been rent in the ground. - -It is possible that in many cases these flashes of fire are in reality -produced by electric discharges that momentarily light the clouds of -dust thrown up out of the fissure. But sometimes true flames are seen -escaping from the fissures. This was the case during the earthquake of -Lisbon, in 1755, when fire burst through fissures at several places, -burning with a lambent flame for some hours. - -The clouds of dust that follow the rending of mountain masses by -earthquakes are probably to be traced to the fracture of the rock -masses, the dust so formed being violently thrown forth by the air -squeezed out of the fissures, when they are suddenly closed. The -violent compression of this air may raise this dust to incandescence. - -Mallet asserts that in many cases the clouds of smoke observed do -not consist of true smoke like that produced when wood or vegetable -matters are incompletely burned, but is only ordinary air mixed with -sulphurous acid gas, and various other gases. - -But not only fire and smoke are seen at times coming out of fissures -in the earth. A thing still more frequently thrown out is water, which -often spouts forth along with great quantities of mud, sand, and the -finely ground fragments of earthy materials generally. Among many -other instances where the emission of water from the crevices was -particularly noticeable, may be mentioned the earthquakes at Jamaica -in 1687 and 1692. Here the water, in some places, was thrown out of -the ground to considerable heights in the air. - -Mallet calls attention to the fact that the waters of springs collect -in reservoirs consisting either of fissures or crevices of the rocks, -of small width but great depth, which are vertical or inclined to the -horizon, or in reservoirs that are formed of extended beds of sand or -gravel. - -Now, when the earthquake waves moving horizontally over the surface -produce movements that squeeze these fissures together, the water in -the fissures is spurted out in high jets, and carries with it the -finely divided rock or sand formed by the rubbing together of the rock -surfaces. In the case of the reservoirs consisting of beds of sand -or gravel, lying between impervious layers, if, during an earthquake -motion, the land areas are suddenly lowered, the water rushing into -the cavity thus left will afterwards be shot out with considerable -force, when the land is suddenly raised again. - -Where there are no direct openings in the ground the water will burst -through the crust in the shape of great vertical jets, thus forming a -circular hole, broken or fractured at its edges. Water jets of this -character were especially numerous during the earthquake of Calabria -in 1783. In a swampy plain, known as Rosarno, many of these circular -wells or openings about the size of an ordinary carriage wheel, though -in some cases much larger, were to be seen crowded together. The -appearance of the openings are represented in Fig. 40. - -Some of these were filled with water, but the greater number were dry -and filled with loose sand. These latter, when examined by digging, -were shown to be funnel-shaped, as seen in Fig. 41. As seen, the -margins of the wells exhibit a series of cracks or crevices extending -radially outward from the centre. Their origin is evident. As the -water was violently expelled by the squeezing motion of the upper -and lower impervious strata, it shot upwards, thus producing the -funnel-shaped tube. At the same time the force of the eruption was -sufficiently great to produce the radial fissures or fractures at the -sides. - -[Illustration: FIG. 40. CIRCULAR HOLLOW FORMED BY CALABRIAN -EARTHQUAKE] - -[Illustration: FIG. 41. SECTION OF CIRCULAR HOLLOW FORMED BY -CALABRIAN EARTHQUAKE] - -But greater fissures than these have been formed by earthquakes, -especially those of the class created by a slipping of the earth's -strata. In the case of an earthquake on the South Island of New -Zealand, in 1848, a fissure having an average width of eighteen -inches could be clearly seen extending in a direction parallel to -the mountain chain for a distance of sixty miles, and during a later -earthquake in the same region, in 1855, a fracture was formed that -could be clearly traced for a distance of nearly ninety miles. - -In some cases these fissures or fractured parts of the crust are left -with one of their sides at a higher level than the opposite side. This -was the case of the great Japanese earthquake of October 28th, 1891. - -There are three kinds of waves produced by earthquakes; namely, the -earthquake waves proper through the earth; the sound waves in the air, -and great forced waves in the sea. - -The sound waves of course reach the air from the point of origin below -the earth's surface through the solid materials of the crust, and take -on the curious varieties already described in connection with the -sounds accompanying earthquakes. - -We have already briefly described the manner in which the earthquake -waves travel through the materials of the earth's crust. There remain -to be discussed the great waves that are rolled up in the ocean -during an earthquake shock. These waves are, perhaps, among the most -destructive phenomena of great earthquakes. The following are only -some of the more remarkable of such waves, and have been taken from -Mallet's collection of earthquake data. - -During some of the great earthquakes on the coasts of Chile and Peru, -huge waves from the ocean did great damage when they reached the land. -In the earthquake of 1590, ocean waves rushed for several leagues -inland over the coast of Chile, carrying with them ships that were -left high and dry as the wave receded. In the earthquake of 1687, -Callao was inundated by a great wave from the Pacific Ocean, and ships -were carried a full league into the country. During the earthquake of -1746, Callao was again swept away by a huge ocean wave. At later times -earthquake waves have caused great damage to several other parts of -the coast of South America. - -Ocean waves of this character are formed by successive upward and -downward movements at the bottom of the ocean, following each other at -very brief intervals. Le Conte points out that the sudden upheaval of -the bed of the ocean forms a huge mound in the surface of the water -which results in a large wave that spreads rapidly in all directions. -Waves produced in this manner sometimes reach a height of fifty to -sixty feet. They are not readily observed in the deep ocean, but -as soon as they reach the shallow waters near the shore they rush -forward, forming waves from fifty to sixty feet in height and, rushing -over the land, sweep everything before them. - -During the great Lisbon earthquake of 1755 a huge wave started at a -point fifty miles off the coast of Portugal. Half an hour after the -earthquake was over several waves, the largest of which was sixty -feet in height, rushed over a part of the city and greatly increased -the ruin already wrought by the earthquake. According to Le Conte the -great waves so formed moved in all directions across the Atlantic -Ocean. They were thirty feet high when they reached Cadiz, eighteen -feet in height at Madeira, and five feet on the coast of Ireland. They -even crossed the Atlantic, being observed on the coasts of the West -Indies. - -A great ocean wave accompanied the Japanese earthquake in 1854. As in -the case of the Lisbon earthquake this wave started in the bed of the -ocean off the coast of Japan and only reached the island half an hour -afterwards. It was thirty feet in height, and completely swept away -the town of Simoda. - -Owing to water's greater freedom of motion earthquake waves travel -greater distances through the water than they do on land. - -Of course, great earthquake shocks as a rule cause a very large loss -of life. The following figures from Mallet give some idea of the -extent of this loss, which is generally a matter of a few moments. - -In the Lisbon earthquake, where the worst shock lasted a few seconds, -60,000 people were killed. During other earthquakes the losses have -been as follows: 10,000 at Morocco; 40,000 in Calabria; 50,000 in -Syria, and probably 120,000 in earthquakes that occurred in Syria in -A. D. 19 and in A. D. 526. - -But even these figures give only a meagre idea of the vast loss of -life that has occurred during the past. It is said that during the -reign of Justinian, earthquakes repeatedly shook the whole Roman -world. The city of Constantinople was visited by earthquake shocks -that continued at intervals for forty days. Deep chasms were opened in -the earth and huge masses were thrown into the air. Enormous sea-waves -were formed. At Antioch, during the earthquake of May 20th, A. -D. 526, 250,000 people are believed to have been killed. - -On the 31st of July, A. D. 365, in the second year of -Valentinian, a dreadful earthquake shook the Roman world, and a great -wave rolled in from the Mediterranean and swept two miles inland, -carrying ships over the tops of houses. During this earthquake 50,000 -people lost their lives at Alexandria. - -In the earthquake of Messina in 1692, 74,000 people are said to have -been killed; and, according to other accounts, 100,000. In the year -A. D. 602, another earthquake at Antioch killed 60,000 people. - -During the earthquake of Quito, in 1797, Humboldt estimates that -40,000 natives were either buried in crevices in the earth, under -the ruins of buildings, or were drowned in lakes and ponds that were -temporarily formed. - -In this connection Mallet writes as follows: - - "Such are the numbers to be met with in narratives, and - if we suppose that there occurs one great earthquake in - three years over the whole earth and that this involves the - entombment of only 10,000 human beings, and that such has - been the economy of our system for the last 4,000 years, we - shall have a number representing above 13,000,000 men thus - suddenly swallowed up, with countless bodies of animals of - every lower class. Sir Charles Lyell then with good reason - suggests that even in our own time we may yet find the - remains of men and of their habitations and implements thus - buried deep and embalmed, as it were, by earthquakes that - occurred in the days of Moses and the Ptolemies." - -Necessarily the progress of a great earthquake wave will produce great -changes in the earth's surface features; for example, landslides, -where immense layers of clay or other material slip or slide to a -lower level and are thrown across the course of a river, causing its -waters to be dammed up and then by spreading to form great lakes. - -Sometimes, after vast bodies of water have been collected in this -manner, disastrous floods result later from a sudden giving way of the -barrier, and the loss thus caused is occasionally far greater than -that directly due to the earthquake. - -Permanent changes of level are frequently caused by earthquakes, as, -for example, the coast of Chile during the earthquake of November -19th, 1822, where the coast for many miles was raised from three to -four feet above its former plane. - -In other cases the level of the ground is permanently lowered. This -occurred in the Bengal earthquake in 1762, when an area of some sixty -square miles suddenly sank, leaving only the tops of the higher points -above water. - -In some cases of changes in the level of the ground, large areas being -raised in one place and lowered in another, rivers take new courses, -and their old courses are completely obliterated. - - - - -CHAPTER XXV - -THE EARTHQUAKE OF CALABRIA IN 1783 - - -All students of elementary geography are quick to notice that the -extreme southeastern part of Italy is shaped something like a boot, -which appears to be kicking at the island of Sicily. This part of the -Mediterranean Sea has for very many years been the arena or storm -centre of more or less intense volcanic activity. To the northwest is -the active volcano of Vesuvius, as well as the volcanic regions of the -Phlegraean Fields. Immediately opposite the point of Italy, near the -toe of the foot, is the active volcanic mountain, Etna, while not far -from this point is the volcano of Stromboli. - -In 1783 this part of the world was visited by a very severe -earthquake. Since at that time the country was divided into two -parts, known as Upper Calabria and Lower Calabria, this earthquake is -sometimes spoken of as the earthquake of the Calabrias, or more simply -as the Calabrian earthquake. - -The great mountain range of the Apennines, mainly of granite -formation, extends through the central part of Italy. The lands -adjoining the mountains on each side are flat and marshy, and -consequently unhealthy. - -Numerous observers have compiled excellent accounts of the Calabrian -earthquake. These, having been made by educated persons, are, to a -large extent free from the inconsistencies and exaggerations apt to -characterize descriptions by ignorant persons, especially when in -a condition of excitement or alarm. Among reliable writers was Sir -William Hamilton, who made a personal examination of the region, soon -after the first severe shock, and collected much valuable information -for a paper which was afterwards published in the Philosophical -Transactions of the Royal Society. Then, too, Dolomieu, another -scientific man of high ability, made a careful study of the effects -produced by the earthquake. - -[Illustration: FIG. 42. MAP OF THE CALABRIAN EARTHQUAKE OF -1783] - -As can be seen by an examination of the map presented in Fig. 42, the -part of Italy included in the Calabrias covers an area from north to -south almost equal to two degrees of latitude. Although the shock -extended beyond the limits of Calabria, since it reached as far north -as Naples, as well as over a great part of the Island of Sicily, the -territory in which the greatest damage was done did not exceed in area -about 500 square miles. - -The southern part of Italy is subject to frequent earthquake shocks. -Pignatari, an Italian physician, asserts that this region was visited -during 1783 by no less than 949 earthquakes, of which 501 were of the -first class, or degree of intensity, while in 1784, there were 151 -earthquakes, of which ninety-eight were of the first class. - -It seems that the city of Oppido, marked on the above map as midway -between the two coasts, was the point from which the severe earthquake -of 1783 started. If one draws a circle, with a radius of twenty-two -miles, around Oppido as a centre, the portions of the Calabrias that -were the most affected will all lie within this circle. - -The great Calabrian earthquake was attended by numerous shocks. The -first and the most severe shock, that of February 5th, 1783, was only -two minutes in destroying most of the houses in all cities, towns, and -villages on the western side of the Apennines in this part of Italy. - -Another severe shock occurred on the 28th of March. This shock was -almost as severe as that of February 5th. - -In order to understand many of the effects produced by this -earthquake, inquiry must be made into the geological character of the -region. According to Dolomieu, the flat country at the slopes of the -Apennines, known as the Plain of Calabria, is covered with sand and -clay mixed with sea shells. These strata have been deposited by the -sea from materials that have been obtained by the decomposition of the -granite mountain ranges in the Apennines. The plain is quite level -except where it is crossed by deep valleys or ravines, which have -been eroded or cut by the swift mountain torrents. In many cases, -these ravines or valleys have depths as great as 600 feet. Their sides -are generally almost perpendicular. Consequently, as Lyell remarks, -throughout the length of the mountain chain, the soil, which adheres -but loosely to the granite base of the mountain chain, could therefore -be easily separated from the mountain, and sliding over the solid -steeps of the mountain could readily move, especially through the -ravines or gorges, to distances in some cases as great as from nine to -ten miles. - -This peculiarity of the country must be thoroughly understood, since, -otherwise, it would seem impossible that lands could be carried -several miles from their former position, and often bear along -with them almost undisturbed houses, olive groves, vineyards, and -cultivated fields. - -The heaving of the surface of the earth like the waters of the sea, -so common in severe earthquakes, occurred during the Calabrian -earthquake. In some places this heaving so shook the trees that they -bent until their tops touched the ground near their base. - -Parts of the ground were violently thrown upwards into the air as in -the explosive type of earthquakes. In many instances the large paving -stones were thrown into the air and afterwards found with their lower -portions upwards. - -During the earthquake deep fissures were made in the earth at various -localities and there were, moreover, marked changes of level. At -Messina in Sicily the shore was fissured and rent and while before the -convulsion the surface had been level, it was afterwards found to be -inclined toward the sea. - -According to Dolomieu the following curious incident occurred during -the passage of the earthquake waves. A well in the ground of one of -the convents of the Augustines, lined on the inside with stones, was -so affected by the upward thrust given to the land that its stone -lining was left projecting above the level of the earth in the form of -a small tower some eight or nine feet in height. - -Frequent instances occurred of deep fissures in the surface of the -earth. Many of these remained open after the earthquake, although in -other cases they were firmly closed together before the earthquake -shocks ceased. - -[Illustration: FIG. 43. FISSURES CAUSED BY THE CALABRIAN -EARTHQUAKE] - -Fig. 43 represents the appearance of certain fissures in a part of -Calabria during this earthquake. These cracks, it will be noticed, -radiate or pass outward in all directions from a central point, just -like the cracks that are formed in a glass window pane when it is -fractured by a stone thrown against it. - -Of course, the most violent effects were near the origin of the -earthquake at Oppido. Here the formation of deep fissures was common. -In another part of the country a number of buildings were suddenly -swallowed up in a central chasm, which almost immediately closed, -thus permanently burying all these objects. - -Some idea of the force with which the fissures were afterwards closed -can be formed by reflecting on a case where, in order to recover some -of the buried articles, the ground was dug up at these points, and it -was found that the materials, human bodies and other objects, were so -jammed together as to make one compact mass. - -To Sir William Hamilton a place was shown where the fissures, though, -when he saw them, they were not more than a foot in width, had opened -sufficiently wide during the shock to swallow up a hundred goats as -well as an ox. - -An earthquake that caused such marked changes in the appearance of the -earth's surface, naturally made great changes in the direction of the -rivers. In one case the end of a small valley was so completely filled -with stones and dirt that the water was dammed up, producing a lake -two miles in length and one mile in breadth. In a similar manner no -less than 215 lakes were formed in different portions of Calabria. - -Of course, in the flat country at the base of the Apennines, -frequent landslides occurred, the land sliding into great chasms and -continuing to move down them for considerable distances, so that in -many places pieces of land containing olive trees, vineyards, and -green fields, were bodily transported for distances of several miles. -This, moreover, was done so quietly as to leave the houses entirely -uninjured, and the trees and other vegetation continuing to grow up -with apparently no marked decrease in vitality. - -As is usual in such cases, the sudden and strong blows acting on the -waters of the sea, killed great numbers of fish just as does the -explosion of dynamite at a point below the surface of the water; and -in a similar way the fish that usually live at the bottom of the sea -in the soft mud, being disturbed by the earthquake shocks, came near -the surface where they were caught in vast numbers. - -It is an interesting fact that during this earthquake the volcano of -Stromboli showed a marked decrease in the volume of smoke it gave out. -Etna, however, was observed to emit large quantities of vapor during -the convulsion. - -Lyell tells the following story of the Prince of Scilla, who with -many of his vassals sought safety in their fishing boats. Suddenly, -on the night of February 5th, while some of the people were sleeping -in the boat, and others were resting on a low plain near the sea, -in the neighborhood, another shock occurred, a great mass was torn -from a neighboring mountain and hurled with a crash on the plain, and -immediately afterwards a wave, twenty feet or more in height, rolled -over the level plain, sweeping away the people. It then retreated, but -soon rushed back again, bringing with it many of the bodies of the -people who had perished. At the same time all the boats were either -sunk or dashed against the beach, and the Prince with 1,430 of his -people was destroyed. - -The total number of deaths caused by this earthquake in the Calabrias -and Sicily were estimated by Hamilton at 40,000. Besides these about -20,000 more perished in epidemics that followed the earthquake, or -died for lack of proper food. - - - - -CHAPTER XXVI - -THE GREAT LISBON EARTHQUAKE OF 1755 - - -Lisbon, the capital of Portugal, on the Tagus River, is built along -both banks for five miles, and on several small neighboring hills. It -is supplied with water by means of an aqueduct, called the Alcantara, -which brings the water from springs about nine miles to the northwest. -For portions of its length the aqueduct is placed underground, but -where it crosses the deep valley of the Alcantara it is supported, -for a distance of 2,400 feet, by a number of marble arches, which -in one place are 260 feet in height. This fact is put forward not -merely for the sake of its artistic interest, but because, strange to -relate, this part of the aqueduct remained uninjured during that great -earthquake, the greatest of modern times. - -On the 1st of November, 1755, this frightful catastrophe, according to -Lyell, from whose excellent account much of the information contained -in this chapter has been obtained, struck the beautiful city almost -without any warning. Terrible sounds came suddenly from underground; -almost instantly afterward a violent shock threw down the greater -portion of the city; in less than six minutes 60,000 people were -killed. - -The place from which this earthquake started must have been situated -on the bed of the ocean at some distance from the coast; for the great -wave thus raised in the Atlantic Ocean did not reach the mouth of the -Tagus River until about half an hour after the most severe shocks -were over. The arrival of this wave at the mouth of the Tagus was -announced by the sea retiring to such an extent as to leave the bar -dry. Then a huge wave, sixty feet in height, rolled in from the ocean -and completed the work of destruction that had been commenced by the -earthquake. - -So great was the shock that the mountains in the neighborhood were -violently shaken and some of them split or fractured in a most -wonderful manner. - -Particularly large was the loss of life in the churches whither -hundreds hastened for refuge when the shakings of the earth began, -for most of these buildings fell and buried the worshippers. Another -immense loss of life was caused by the destruction of a large marble -quay or wharf that was suddenly swallowed up by the sea. While the -buildings in the city were being overthrown by the violent shakings -of the earth, a multitude sought the quay as a flat place where they -could not be injured by the falling buildings. Suddenly, however, -this structure sank into the water and not only were all the people -drowned, but none of the bodies was ever afterwards found. - -Failure to find any remnants of the pier or any of the people who -perished on it has been attributed to the formation of eddies or -whirls that were sufficiently strong to carry down vessels by suction -similar to that of the famous maelstrom off the coast of Norway. Of -course, in a time of boundless excitement like that of the Lisbon -earthquake, accounts are apt to be highly exaggerated. For example, -assertions are made in many books that the water left in the harbor -after the sinking of the quay was unfathomable. Now, in point of fact, -the depth of this place has been measured and found to be less than -100 fathoms. - -When it is remembered that not one of the bodies of the people on that -quay was ever again seen, it is possible, as Lyell suggests, that a -deep fissure or chasm opened immediately on the ground on which the -quay stood, so that it, together with all on it, were dropped into the -chasm, which, closing, buried them deep in the earth. - -The Lisbon earthquake was especially noted for the extent of country -affected by it. Humboldt estimated this area as being more than four -times the size of Europe. In parts of this area immense mountain -ranges, such as the Pyrenees, Alps, etc., were violently shaken. When -the size of these mountains is considered one realizes that it must -have required a mighty force to shake them. These shakings were so -severe that they produced a deep fissure in the ground in France. -Continuing towards the north the solid earth was shaken as far as -the shores of the Baltic and Norway and Sweden, generally. This, of -course, included the flat country of Northern Germany. The hot springs -of Toplitz disappeared for a time, but, breaking out afterwards, -discharged such quantities of muddy water that the surrounding country -was inundated. - -The waves crossed the Atlantic, causing high tides on the island of -Antigua, Barbadoes, and Martinique, of the Lesser Antilles, where, -instead of the usual tides of two feet, tides of twenty feet high were -observed. Further to the north the waves reached the eastern shores of -North America, and shook the continent as far west as the Great Lakes, -and spread in the North Atlantic as far as Iceland. - -Toward the south the waves affected parts of northwestern Africa, -where much loss of life occurred in the villages some eight leagues -distant from the city of Morocco. Here from 8,000 to 10,000 people -were killed, being swallowed up by deep fissures in the earth, which -afterwards closed on their bodies. - -Severe shocks were in many cases felt on vessels at sea. In one -instance, although the vessels were at considerable distances from -where the waves started, the captains reported that the shocks were so -great that on several occasions it was believed the vessel had struck -a rock, till, on heaving the lead, they found that they were in very -deep water. In another instance, such was the shock to the vessel that -the planks on the deck had their seams opened. In still another case -several of the sailors were thrown into the air for a distance of -about one and a half feet. - -It has been frequently observed that when great earthquakes happen, -curious changes take place in the level of the waters of lakes -entirely disconnected with the ocean; for example, mountain lakes, -far above the level of the sea, the water suddenly rising and then -resuming its original level. Sometimes the waters of such lakes have -suddenly disappeared, probably being drained off through a fissure -formed in the bed of the lake. In such event the lake generally -remains dry after the passage of the earthquake. - -At the time of the Lisbon earthquake it was observed that the water of -Loch Lomond in Scotland first rose above its ordinary, then sank again -to its usual level. This difference of level is explained by Lyell as -follows: when the earthquake waves reached the lake, the water being -unable to take the sudden shove given to it by the earthquake waves, -dashed over that side of the basin which first received the shock. -Assuming this to be the case, since the rise of the level in the water -of Loch Lomond was two feet and four inches, it is comparatively easy -to calculate the speed of movement that the earthquake waves had, -when they reached this body of water. Calculated in this way it would -seem that the waves had a speed of about twenty miles a minute. - -But what especially characterized the Lisbon earthquake were the great -waves that were produced in the ocean. Besides the huge wave that -entered the Tagus, a wave of the same height swept eastward along the -southern coast of Spain, and the northwestern coast of Africa. At -Tangier in Africa it swept the coast as a very high wave no less than -eighteen times, or, in other words, eighteen huge waves rolled in from -the ocean. At Funchal, on the Madeira Islands, this wave rose fifteen -feet above the high water mark. - -Many attempts have been made to explain the manner in which the great -sea waves are started in earthquake movements. Some believe that they -are due to the sudden raising or heaving up of the water, far above -ordinary level. But, as Lyell points out, this explanation would not -be satisfactory for the waves produced in the case of the Lisbon -earthquake, since it would fail to account for the fact that both on -the coasts of Portugal as well as on the island of Madeira the high -wave was preceded by a movement of the water toward the point of -origin; that is, the waters moved away from Lisbon and the Madeira -Islands, so as to leave the water very low at those points, when -shortly afterwards a huge wave rushed in from the sea and swept over -the land. - -Earthquake waves move much more rapidly through the solid rocks of -the earth's crust than through the waters of the ocean. The shock -transmitted through the solid earth from Lisbon to the Madeira Islands -took only twenty-five minutes to reach the islands, while the waves in -the ocean took about two and a half hours to cover the same distance. - - - - -CHAPTER XXVII - -THE EARTHQUAKE OF CUTCH, INDIA, IN 1819 - - -Cutch is one of the Provinces of India lying on the western coast of -Hindostan, east of the delta of the Indus River. - -A great earthquake occurred in this region on June 16th, 1819. As -indicated by the map presented in Fig. 44, by Lyell, the district -of Cutch lies on the coast of the Arabian Sea. Cutch is at times a -peninsula, being washed on the south and east by the Arabian Sea and -the Gulf of Cutch, and on the north by a depression known as the Runn -of Cutch which, during unusual tides, is overflowed by the waters of -the sea, but for the rest of the year is dry. - -The earthquake of Cutch was apparently central at the town of Bhooj, -where the destruction was extreme, hardly a house being left standing. -The shock extended over a radius of about 1,000 miles from Bhooj, -reaching to Khatmandoo, Calcutta, and Pondicherry. - -At Anjar the fort, together with its tower and guns, were completely -ruined. The shocks continued at intervals after the principal shock -until June 20th, when the volcano of Denodur is said by some to have -emitted flames, although this is denied by others. - -Great changes were produced in the eastern channel of the Indus, -which forms the western boundary of the Province of Cutch. The water -in this inlet had become so low that it was readily fordable at low -tide at Luckput, and was only covered with six feet of water at high -tide. After the earthquake it deepened at the port of Luckput to over -eighteen feet at low tide, while in other parts of the channel the -water had deepened from four to ten feet at high tide, where before -the earthquake shock it had never been deeper than from one to two -feet. Indeed, after these changes the inland navigation of the country -again became possible after having been closed for many centuries. - -[Illustration: FIG. 44. MAP SHOWING DISTRICT VISITED BY THE -EARTHQUAKE OF CUTCH OF 1819] - -The Cutch earthquake resulted in a marked depression of the country, -especially north of Luckput, where the fort and village of Sindree -were so quietly sunk that the fort, with its tower and walls, was left -projecting slightly above a body of water that not only completely -covered the old site but also formed a large lake marked on the -preceding map, at Sindree, by the dark shading. It was this change of -level that deepened the eastern channel of the Indus, just mentioned. - -[Illustration: FIG 45.. SINDREE BEFORE THE EARTHQUAKE OF -1819] - -Fig. 45, from Lyell, gives an idea of the appearance of the fort at -Sindree before the earthquake. The appearance of the fort after its -submergence is represented in Fig. 46, where, as will be noticed, only -the top of the tower and the walls remain above the surface of the -water. That the masonry was not affected either by the earthquake, or -by the inrush of waters, is evident from the fact that the ruins were -still standing in March, 1838, as represented in the figure. - -In heavy shading on the map in Fig. 44 is a large area lying in the -northern part of the province known as the Runn of Cutch. This is a -flat region of about 7,000 square miles. It owes its level surface to -its being the deserted or dried-up bed of a sea. For the greater part -of the year its bottom is dry and hard, and is covered with a crust of -salt half an inch or so in thickness. - -[Illustration: FIG. 46. SINDREE AFTER THE EARTHQUAKE OF 1819] - -According to Lyell, from whom most of the facts concerning this -earthquake have been obtained, the Runn of Cutch is connected with -a vast inland sea, not only by the water driven into it through the -Gulf of Cutch, but also through the eastern channel of the Indus at -Luckput. These changes occur especially during the monsoon, when the -seas are high, and especially after the heavy rains that come with -these winds, when the wet condition of the soil permits the sea water -to spread rapidly. - -Traditions of the natives tend to confirm belief that Cutch a long -time ago was a true peninsula, and that the Runn of Cutch was then an -arm of the sea. - -That a change of this character did occur in the Runn of Cutch seems -to be proved by the ruins of old towns now far inland that are said to -have been ancient seaports, and as apparent evidences of this many -pieces of wrought iron and ships' nails have been found in parts of -the Runn. - -At the same time that the sinking of the land around the fort and -village of Sindree took place a considerable elevation occurred in the -neighborhood. Immediately after the earthquake, the people in Sindree -saw that a low hill or mound had been thrown up in a place that before -had been a low and perfectly level plain. They named this elevation -the Ullah Bund, or _the Mound of God_, in order to distinguish it -from several embankments that had been built directly across the -eastern mouth of the Indus; for the Ullah Bund had been raised by the -earthquake across the same branch of the Indus. - -For several years after the earthquake of 1819 marked changes kept -developing in the channels of the Indus. During 1826 a large body of -water entered into the eastern branch of the Indus above the Ullah -Bund and finally forced its way through the mound, thus establishing -a direct course to the sea. The Ullah Bund, being thus cut in two, -an opportunity was afforded of seeing the materials of which it was -composed. These were found to consist principally of clay filled with -shells. - -The opening of the river resulted in throwing such large quantities of -fresh water into Lake Sindree that its waters were rendered fresh for -several months, but at last regained their saltiness. - -Dana states that in 1845 another earthquake occurred in this district -which converted Sindree Lake into a salt marsh. - - - - -CHAPTER XXVIII - -THE SAN FRANCISCO EARTHQUAKE OF APRIL 18, 1906 - - -About twelve minutes past five o'clock on the morning of the 18th of -April, 1906, the inhabitants of San Francisco were rudely awakened by -a few frightful earthquake shocks. Their houses were violently shaken -to and fro, and on all sides were heard the awful crashings of falling -walls, chimneys, and buildings, together with the death-shrieks of -those caught in the ruins. Rushing madly into the streets they could -see on every side evidences of destruction; for, in almost every -direction, were heaps of fallen buildings, still being violently -shaken by the earthquake waves that rapidly passed through the solid -earth. Huge cracks or crevices had been formed in the streets, while -the heavy rails of the trolley tracks had been bent and twisted by the -mighty forces. - -Before describing in detail the great San Francisco earthquake, the -location of the city and its surroundings demand consideration. - -As can be seen from the map, Fig. 47, San Francisco is situated on the -western coast of California, at the northern end of a peninsula, some -twenty miles in length and about six miles in width. This peninsula -is formed by the magnificent Bay of San Francisco on the east, a -navigable strait called the Golden Gate on the north, and the Pacific -Ocean on the west. - -[Illustration: FIG. 47. MAP OF WESTERN COAST OF CALIFORNIA SHOWING -POSITION OF SAN FRANCISCO] - -San Francisco Bay, accessible by the Golden Gate, is the principal -harbor on the Pacific Coast, and is, indeed, one of the most -magnificent harbors in the world. It is land-locked, that is, -surrounded by a continuous land border except at its entrance through -the Golden Gate. Including San Pablo Bay, it has a length of about -fifty-five miles, and varies in breadth from three to twelve miles. -The entrance to the harbor, however, is impeded by a bar across the -mouth of the Golden Gate, over which there is a depth of but thirty -feet of water at low tide. - -San Francisco has over 750 miles of streets, 200 miles of which are -paved. The city is lighted by both electricity and gas, and has an -extensive system of water-works, the water being brought from the -Pilarcitos and Calaveras Creeks, situated from twenty to forty miles -respectively from the city. - -San Francisco is in a region where earthquakes are common. It might, -therefore, be visited at any time by a great catastrophe. There have -occurred between 1850 and 1888, no less than 254 earthquake shocks in -the State of California, these shocks having been especially frequent -in the country surrounding San Francisco Bay. The most severe were -the earthquake of 1868, which injured San Francisco; the Owens Valley -earthquake of 1872; the Vacaville earthquake of 1892; the Mare Island -earthquake of 1898; and a smaller earthquake in 1900. Since 1900 there -was a period of rest until the 18th of April, 1906. - -As in the case of practically all severe earthquakes, that which -destroyed San Francisco consisted of a few momentary shocks: then all -was over. According to a preliminary report of the State Earthquake -Commission, appointed by the Governor of California, April 21st, 1906, -these shocks, as recorded in the observatory at Berkeley, began at -twelve minutes and six seconds after five A. M., Pacific -Standard Time. Their entire duration was only one minute and fifty -seconds, but, as frequently happens, there were a number of minor -shocks, following at regular intervals during the next few hours as -well as the next few days. - -While the most severe shocks were in the neighborhood of the Peninsula -of San Francisco, yet minor disturbances were felt as far north -as Coos Bay, Oregon, and as far south as Los Angeles, California. -As shown by recording instruments at the seismograph station at -Washington, D. C., Sitka, Alaska; Potsdam, Germany; and Tokio, Japan, -a series of waves were propagated through the earth, as well as over -its periphery. - -The damage done within the city limits was wide-reaching. Among the -buildings almost completely destroyed were the City Hall, on which -about $7,000,000 had been expended, the United States Post Office, -besides many business blocks, hotels, department stores, theatres, -banks, churches, and dwelling houses. - -Amid the terrors of such a calamity it is difficult to obtain -observations possessing any scientific value. Fortunately, however, -there was in the city a physicist trained to observe phenomena of this -character, Professor George Davidson of the University of California. -Like others, he had been awakened by the first severe shock. At once -recognizing the nature of the phenomenon, and desirous of obtaining -the exact time of its occurrence, he counted seconds while he ran -towards the table on which he had placed his watch, and in this way -estimated that the shock occurred at twelve minutes past five in -the morning. The closeness of this observation is emphasized by the -fact that it differed from the recorded time by only six seconds. He -states that the motion, at the time of its greatest intensity, closely -resembled that of a rat vigorously shaken by a terrier. - -The destruction caused by the earthquake was, however, but a small -part of the total loss to the city. Fires were almost immediately -started in the ruined houses by the fires in the kitchens and other -parts of the houses, by the ignited jets of the illuminating gas, -and, perhaps, especially, by the crossing of numerous electric light -wires. - -The manner in which the woodwork and other combustible materials of -the buildings were loosely tossed together by the shocks helped the -quick spread of the fires, and this, too, was probably greatly aided -by the illuminating gas from the broken gas pipes and mains. Eight -severe conflagrations were, therefore, soon raging in different parts -of the doomed city. What made these fires especially dangerous was the -fact that the earthquake shocks had destroyed the water pipes. Thus -the firemen were handicapped in their heroic endeavors to extinguish -the flames. - -At the time of the fire a strong wind was blowing from the northeast. -Since the firemen were unable to check the flames, the fire line -rapidly advanced. Its path led towards the best residential parts of -the city through portions of the mission section containing a dense -population of poor people. The dwellings in this latter section -consisted of frame houses, through which the flames rapidly spread. - -There was but one way to save the city from total destruction--a free -use of dynamite! This was intelligently employed until the supply gave -out, when it seemed that the city was doomed to utter destruction. -But at the last moment, as it were, came a lucky change in the -direction of the wind. Instead of blowing from the northeast, the -steady southwest winds set in, and beat back the fire on itself, so by -Friday, the 18th being Wednesday, it was under complete control and -the rest of the city was saved. - -[Illustration: A SAN FRANCISCO PAVEMENT TORN BY THE -EARTHQUAKE _From a Stereograph, Copyright, 1906, by Underwood & -Underwood_] - -The extent of the fire is thus described in an article in the -"Outlook," for Saturday, April 28th, 1906, as follows: - - "The turn in the direction of the fire endangered for a - time the great Ferry House, at the foot of Market Street. - While the section actually destroyed is not, geographically - speaking, much more than one-third of the city limits, - yet it is in the heart of San Francisco, and includes the - chief business streets and the Mission District, inhabited - by poor people, and a large part of the so-called Nob Hill - Quarter, where were the finest and costliest residences of - the city. Another fine residence section, Civic Heights, - escaped, together with that known as the Western District. - - "The unburned district, though large in extent, was in - the nature of suburbs, and was not closely built up, so - that estimates made, as late as Saturday, declared that - three-fourths of San Francisco's improvements in real - estate had been destroyed." - -The burnt district was about two miles from east to west and from two -to four miles from north to south, with, of course, very irregular -outlines. - -Naturally, the great destruction wrought by the earthquake of April -18th, 1906, attracted the almost universal attention of scientific men -especially interested in earthquake phenomena. We are, therefore, able -to speak authoritatively about the probable causes. - -The great San Francisco earthquake of April 18th, 1906, appears to -have been a _tectonic_ quake. Ransome, in an article entitled, "The -Probable Cause of the San Francisco Earthquake," says: - - "The region thus amply fulfils the conditions under which - tectonic earthquakes arise. It is in unstable equilibrium, - and it is cut by long northwest faults into narrow blocks - which are in turn traversed by many minor dislocations. - Under the operation of the unknown forces of elevation and - subsidence, stresses are set up which finally overcome the - adhesion of the opposing walls of one or more of the fault - fissures; an abrupt slip of a few inches, or a few feet, - takes place and an earthquake results. The region extending - for some hundreds of miles north and south of the Bay of - San Francisco may be considered as particularly susceptible - to shocks on account of the number and magnitude of the - faults and the evidences that these furnish of very recent - slippings and the marked subsidence in the vicinity of the - Golden Gate." - - - - -CHAPTER XXIX - -SOME OTHER NOTABLE EARTHQUAKES - - -It would, of course, be impossible within the limits of this book to -attempt a description of all the remarkable earthquakes in the annals -of science; but before leaving this part of the theme a brief account -of a few more among the many may be worth while. - -Jamaica, one of the West Indian Islands, about ninety miles south of -Cuba, suffered a very destructive earthquake in 1692. During this -earthquake the ground was agitated like the waves of the sea. These -movements were so violent that numerous fissures were made in the -ground, as many as 300 being formed at the same time, rapidly opening -and closing. Many of the inhabitants were swallowed up in these -fissures. In some cases, however, their bodies were afterward thrown -out of the fissures, along with quantities of water. - -The Jamaican earthquake was characterized by marked sinkings of the -ground. At the city of Port Royal, which was then the capital, many -houses on the harbor side sank in from twenty-four to forty-eight -feet of water. As in the case of the earthquake at Cutch, many of -these houses were left standing, the chimney tops of some being seen -above the water, with their foundations and other parts apparently -uninjured, and some of them were standing at a date as late as 1780. -At a little later date, 1793, they were mostly ruins. - -During the Jamaican quake a tract of land containing at least 1,000 -acres near the town was sunk, and a wave of the sea rolled over it. -This wave is said by Lyell to have carried a frigate over the roofs of -the houses and left it stranded on one roof. When the wave rolled back -to the sea, the weight of the frigate made it fall through the roof. - -Perhaps one of the most remarkable things about the Jamaican -earthquake was the swallowing up of several plantations, which -disappeared, together with all their inhabitants, their former place -becoming a lake. But the lake soon disappeared, leaving a mass of sand -and gravel which obliterated any least sign that dwellings and trees -had once adorned the spot. - -The forces developed during this earthquake were sufficiently powerful -to make several rents in the Blue Mountains, and the shock of blows on -the waters of the sea killed fish by the hundred thousands so that the -silver shine of their dead bodies stretched for miles and was beheld -for days "on the face of the deep." - -Portions of the world that have been frequently visited by mighty -earthquakes, are the coasts of Chile. On the 24th of May, 1751, a part -of the Chilian coast near the ancient town of Concepcion, sometimes -called Penco, was destroyed by an earthquake, and the powerful -earthquake waves that afterwards rushed in from the sea. So complete -was this destruction that the ancient harbor was rendered useless and -the people had to build another town about ten miles from the coast, -so as to be beyond the reach of earthquake waves from the sea. - -Another great earthquake occurred on the coast of Chile on the -19th of November, 1822. This shock was felt simultaneously over a -distance of 1,200 miles from north to south. It reached its greatest -intensity about 100 miles north of Valparaiso. This earthquake caused -a rising of the coast to a height of from three to five feet. From -careful examinations it appears that the area over which a permanent -elevation of the country took place must have been equal to 100,000 -square miles, an area equal to about half of the area of France, and -five-sixths that of Great Britain and Ireland. - - "If we suppose," says Dana, "the elevation to have been - only three feet on an average, it will be seen that the - mass of rock added to the continent of America by the - movement, or, in other words, the mass previously below the - level of the sea, and after the shock, permanently above - it, must have contained fifty-seven cubic miles in bulk; - which would be sufficient to form a conical mountain two - miles high (or about as high as Etna) with a circumference - at the base of nearly thirty-three miles.... Assuming the - Great Pyramid of Egypt, if solid, to weigh in accordance - with the estimate before given 6,000,000 tons, we may - state that the rock added to the continent by the Chilian - earthquake would have equalled more than 100,000 pyramids. - - "But it must always be borne in mind that the weight of - rock here alluded to constituted but an insignificant - part of the whole amount which the volcanic forces had to - overcome. The thickness of rock between the surface of - Chile and the subterranean foci of volcanic action may be - many miles or leagues deep. Say that the thickness was only - two miles, even then the mass which changed place and rose - three feet, being 200,000 cubic miles in volume, must have - exceeded in weight 363,000,000 pyramids." - -The shocks of this earthquake continued from the time of its -occurrence, on November 19th, 1822, to the end of September, 1823, and -even then there were scarcely two days that passed without a shock. - -On the 20th of February, 1835, the same part of the world was in the -throes of an earthquake that was felt nearly 1,000 miles from north to -south, or from near the town of Concepcion to the Isle of Chiloe, and -from east to west a distance of about 500 miles, from Mendoza to the -island of Juan Fernandez, which you probably know better as Robinson -Crusoe's Island. By this earthquake the new town of Concepcion and -several other towns were partly destroyed. - -There were the same phenomena connected with great sea waves that are -common in earthquakes of this character. Both this and the preceding -earthquakes probably began on the bed of the ocean at some distance -from the coast; for, in the last earthquake, the sea retired from the -Bay of Concepcion and vessels were grounded that had been anchored -in seven fathoms of water. Shortly afterwards waves from sixteen to -twenty feet in height rushed in from the ocean and swept over the land. - -It is interesting in this connection to note that the volcanoes of the -Chilian Andes were in an unusual state of activity before, during, and -after the earthquake. - -Another characteristic of this quake was the great number of severe -shocks. Between the day of the first great shock; i. e., on February -20th, 1835, and March 4th, there were more than 300 severe shocks. - -In this as in the preceding quake a notable elevation of the land near -the coast occurred, amounting to from four to five feet, and a part of -the bed of the ocean near the coast was raised permanently above the -level of the sea. - -In the description of the explosive eruption of Krakatoa in 1883, the -fact was noted that the island of Java is very frequently visited by -earthquakes. Here a terribly severe earthquake occurred on the 5th of -January, 1699. There were no less than 208 shocks of great intensity. -Considerable property in the city of Batavia was destroyed, and a -neighboring river, that has its head waters by a volcano near the -city, ran high and muddy and brought down multitudes of fishes that -had been killed, together with many buffaloes, tigers, rhinoceroses, -deer, and other wild beasts. Seven hills bordering on the river sank -down, damming up the streams of the region and thereby causing wide -destruction from floods. - -During portions of the years 1811 and 1812 an earthquake occurred -in the United States, in the Mississippi Valley near the town of -New Madrid, Missouri, at the mouth of the Ohio River. These shocks -continued almost incessantly for several months, and were accompanied -by a sinking of the ground over large areas. This depressed area, -known in the neighborhood as _The Sunk Country_, extended along the -course of the White Water River and its tributaries for a distance of -about eighty miles from north to south, and several miles from east -to west. Most of it was converted into a marshy lake characterized by -thousands of submerged trees. The area was covered for the greater -part with water to a depth of about three to four feet. - -As the earthquake shocks continued at intervals for several months -there was an ample opportunity for studying the peculiarities of the -earth waves. The ground rose and fell like large waves in the sea, and -after the crest of the waves had reached great heights, the ground -burst, and threw large quantities of water, sand, and earth into the -air. - -[Illustration: FIG. 48. NEW ZEALAND] - -Throughout the disturbed district there were numerous depressions -known as _sink-holes_, or irregularly shaped pits, varying from ten to -thirty yards across, and having a depth of about twenty feet. These -were formed by the forcible ejection of large quantities of water -mixed with sand. - -New Zealand has been subject to earthquake shocks for a long time, the -years 1826, 1841, 1843, 1848, and 1855 being especially marked by such -visitations. It is a characteristic of the New Zealand earthquakes -that they have produced a marked change in the coast line. This was -particularly the case with those of 1848 and 1855. - -The 23d of January, 1855, an earthquake occurred that was most violent -in the narrowest part of Cook's Strait, a body of water separating -the two principal islands that constitute New Zealand; or, as they -are called, the North Island and the South Island. These shocks were -felt at sea by ships 150 miles from the coast. The entire area shaken, -including the water, has been estimated at three times the area of -the British Isles. In the vicinity of the southern shores of the -North Island a tract of land having an area of 4,600 square miles is -believed to have been permanently raised from one to nine feet. - -The earthquakes in New Zealand are evidently of the tectonic type. -During that of 1848 a rent or fissure was formed, which, though but -eighteen inches in average width, yet extended for a distance of sixty -miles in a direction parallel to one of the mountain chains. - -On the 31st of August, 1886, an earthquake of considerable intensity -occurred in the United States in the neighborhood of the city of -Charleston, South Carolina. The details of this earthquake were -carefully studied by Major Dutton of the U. S. A., and published in -the Ninth Annual Report of the United States Geological Survey of 1888. - -Charleston is situated on a narrow tongue of land between the Ashley -and the Cooper Rivers, about seven miles from the Atlantic Ocean. -There are in this area numerous creeks connected with the drainage of -these rivers. As the city limits extended, the creeks were filled in, -forming "made land," all buildings or structures erected on this land -being supported by pilings. - -It appears that the point at which the earthquakes started was -situated sixteen or seventeen miles from Charleston. - -The earthquake shock affected a large area of the United States. Fig. -49 shows curved lines called isoseismal connecting places, having the -same degree of seismic intensity. This map shows that these isoseimals -are marked by figures or numbers from two to ten. These numbers are -the numbers of the Rossi-Forel earthquake scale. They indicate varying -degrees of intensity, beginning from the least intense shock which -is marked as two and ending with the severest shock marked as ten. -There is one degree not marked on this map, the least, called the -micro-seismic shock. - -The shocks then increase in intensity as follows: II. Extremely -feeble shocks; III. Very feeble shocks; IV. Feeble shocks; V. Shocks -of moderate intensity; VI. Fairly strong shocks; VII. Strong shocks; -VIII. Very strong shocks; IX. Extremely strong shocks; X. Shocks of -extreme intensity. - -The meaning of the map presented in the accompanying figure will now -become more apparent in several ways. That portion numbered ten, -denoting where shocks of greatest intensity have been experienced, -clearly indicates the region just above the point where the earthquake -originated. - -Beyond this is a region marked nine where the earthquake shock has -decreased in intensity to the next figure on the Rossi-Forel scale, -and then to eight and a half, seven, six, five, four, three, and two. - -[Illustration: FIG. 49. MAP SHOWING REGION AFFECTED BY THE -CHARLESTON EARTHQUAKE OF 1886] - -The Charleston earthquake damaged property to a considerable extent; -for, although comparatively few buildings were completely destroyed, a -considerable number were partially injured, and many, not thrown down -by the shock, had to be torn down in order to insure public safety. -The loss of life, fortunately, was comparatively small. During this -earthquake a number of openings called _craterlets_ were made in the -ground by the forcible ejection of large quantities of water and sand. - -The empire of Japan is another part of the world particularly subject -to great as well as frequent earthquake shocks. Although Japan is also -especially noted for its volcanic activity, its earthquakes are almost -entirely of the tectonic type, or are due to the slipping of the land -at faults in the earth's crust. Most of these quakes occur on the bed -of the ocean on the sides of a steep slope that extends down to a very -deep part of the Pacific known as the _Tuscarora Deep_. - -On the 28th of October, 1891, Japan was visited by a great quake, -generally known as the Mino-Owaro earthquake, from the name of the two -provinces of Mino and Owaro in which it occurred. - -This earthquake is correctly regarded as one of the most severe in -Japanese records. Originating, as it did, in a densely populated -section, it caused a great loss of life and property. The deaths -reached about 7,000, while the number of houses entirely destroyed -reached about 80,000 and those partly destroyed nearly 200,000. The -total area markedly affected reached 250,000 square kilometres, while -the area sensibly affected reached 900,000 square kilometres, or a -little more than one-half the Empire. - -The place at which this earthquake started was situated, not as usual -on the bed of the ocean, but on the surface of the land. The first -shock was the strongest and wrought the greatest havoc. Besides the -loss of life and property, the damage to the system of dikes or levees -on the river where it passed through the delta plain near the river's -mouth was heavy, and singular in some of its features. In one case, -near the city of Nagoya, on the Bay near the southern coast of Niphon, -one of these levees was lifted and shifted bodily more than sixty feet -from its original position. - -That this quake was of the tectonic type was evident from the great -fault that was formed. According to Davison this fault was seventy -miles in length and in places had a breadth of from two to five feet. -It extended from east to west, crossing the entire width of the island. - -Another great earthquake was that which hit northeastern Bengal and -Assam in India on the 12th of June, 1897. According to the India -Geological Survey, by whom a careful examination of the effects -produced by this quake was made, it was, perhaps, the greatest quake -that ever happened, not even excepting the Lisbon earthquake. - -The place where the quake started appears to have been of unusual size -and irregularity of outline. Its southern boundary was almost in the -shape of a straight line extending from east to west about 200 miles, -and covering a total area of nearly 6,000 square miles. Over all this -vast area the intensity of the shock was exceedingly severe. The total -area perceptibly shaken by the quake was about equal to 1,750,000 -square miles. - -That this quake was of the tectonic type became evident, when several -faults were found in the ground afterwards. Some of these extended -twelve miles, with a breadth at places as great as thirty feet. - -Valparaiso, or, as the name means, Vale of Paradise, the second -largest city of Chile and its chief seaport, lies about ninety -miles east of Santiago, the capital, with which it is connected by a -railroad. - -This beautiful sea city is built at the base of a cluster of hills -about 1,600 feet above sea level. On August 16th, 1906, it was visited -by an earthquake. There were two distinct shocks. Contrary to general -rule it was not the first, but the second shock that did the most -damage, coming about ten minutes after the first. As you will see from -the above date the earthquake of Valparaiso occurred shortly after -the catastrophe of San Francisco. In a general way, its coming was -predicted by Dr. G. F. Becker of the United States Geological Survey, -on April 19th, 1906, one day after the San Francisco disaster. Becker -published an article in the "New York Tribune," in which he argued -that the severe shock at San Francisco, having occurred on one part -of the earthquake region extending around the Pacific, would probably -soon affect other portions of this region along the Pacific coast line -of this hemisphere. - -As at San Francisco fierce fires immediately started in the ruins of -the houses, but the Valparaisans were more fortunate in having a water -supply available. - -There were very many shocks following the first two of this -earthquake. Indeed, during August 16th, 17th, 18th, and 19th, no less -than 380 were noted. - -Santiago, situated at the foot of the Andes, was also considerably -damaged by the same earthquake. Estimates, probably conservative, put -the total of dead in both cities at 1,000 and the number of people -rendered homeless temporarily, at 100,000. - - - - -CHAPTER XXX - -SODOM AND GOMORRAH AND THE CITIES OF THE PLAIN - - -The eastern border of the Mediterranean Sea or Syria, with that part -of Arabia forming the Sinai Peninsula and which lies between the two -northern arms of the Red Sea, is a region formerly characterized by -extreme volcanic activity. This region includes the greater part of -the land promised, according to the Old Testament, to the Children -of Israel. Through a large part of this region flows that historic -river, the Jordan, until it empties into the Dead Sea, also called the -Salt Sea, the Sea of the Plain, and by some Lake Asphaltites because -of asphalt or bitumen so abundant on its shores. This river has its -source in the Mountains of Lebanon, some distance north of the Sea of -Chinnerth, Tiberius, or the Sea of Galilee, which empties into the -River Jordan. - -As the map in Fig. 50 shows, this famous, though small river, flows -between ranges of high hills, or low mountains, that lie on both its -eastern and western boundaries; and these parallel ranges extend -down to the Gulf of Akaba, which forms the eastern boundary of the -Sinai Peninsula. The Sea of Galilee, the valley of the Jordan and the -country between the Dead Sea and the Gulf of Akaba, are all, for the -most part, considerably below the level of the Mediterranean or the -Red Sea; the Sea of Galilee being about 626 feet and the Dead Sea 1312 -feet below that line. - -[Illustration: FIG. 50. SYRIA] - -That this country has been the scene of great volcanic activities is -evident from the volcanic rocks found over different portions of its -surface. Moreover, the remains of several craters are still visible. -On the western banks of the Jordan numerous dikes and streaks of -basalt occur in the limestone that covers parts of the region. Besides -there are thermal springs whose waters are at a temperature, according -to Daubeny, of 114 deg. F. Then, too, in the neighborhood of the Dead -Sea, as well as in the neighborhood of the adjoining mountain ranges, -there are quantities of sulphur and asphaltum or bitumen, while on the -Dead Sea asphaltum is found floating in sufficient quantity to be a -source of considerable revenue to the boatmen who collect it. It was -in this region that Sodom, Gomorrah, and other cities of the plain -were situated; cities so wicked that God utterly destroyed them by -volcanoes and earthquakes. - -Volcanic activity was evidently common in this land of the Bible -during the times of the prophets of Israel; for in their poetic -writings are frequent references to such phenomena--beautiful and -majestic similes and metaphors derived from contemplation of live -volcanoes. - -Jeremiah says: - - "Behold, I am against thee, O devouring mountain, saith the - Lord, which destroyeth all the earth; and I will stretch - out mine hand upon thee, and roll thee down from the rocks, - and will make thee a burnt[4] mountain. - - "And they shall not take of thee a stone for a corner, - nor a stone for foundations; but thou shalt be desolate - forever, saith the Lord." (Jer. li, 25-26.) - -So, too, the prophet Isaiah says: - - "Oh that thou wouldst rend the heavens, that thou wouldst - come down, that the mountains might flow down at thy - presence! - - "As when the melting fire burneth, the fire causeth the - water to boil, to make thy name known to thine adversaries, - that the nations may tremble at thy presence! - - "When thou didst terrible things which we look not for, - thou cameth down, the mountains flowed down at thy - presence." (Is. lxiv, 1-2.) - -So, too, the prophet Nahum says: - - "The mountains quake at him, and the hills melt, and the - earth is burned at his presence, yea, the world, and all - that dwell therein. - - "Who can stand before his indignation? And who can abide in - the fierceness of his anger? His fury is poured down like - fire, and the rocks are thrown down by him." (Nahum, i, - 5-6.) - -Let us now examine briefly the description Moses gives of the -destruction of Sodom, Gomorrah, and other cities of the plain. This -destruction occurred during the life time of Abraham and his nephew -Lot. The record says that God told Abraham He intended to destroy -them because of their wickedness. Then follows in the 18th chapter -of Genesis the eloquent pleading of Abraham for one of the doomed -cities. At Abraham's earnest plea God promises to spare Sodom if -fifty righteous men can be found therein. Obtaining this respite, -Abraham repeatedly asks further mercy for the city, and at last -receives the sacred promise that the city shall not be destroyed, if -but ten righteous people can be found there. An evidence of the great -wickedness of the city is seen in the fact that not even ten could be -found. Whereupon the Lord gives notice to Lot that the cities were -doomed and commands Lot to leave at once with his family. - - "Escape for thy life; look not behind thee, neither stay - thou in all the plain; escape to the mountain, lest thou be - consumed!" - -Moses describes what happened as follows: - - "The sun was risen upon the earth, when Lot entered into - Zoar. - - "Then the Lord rained upon Sodom and upon Gomorrah - brimstone and fire from the Lord out of heaven; - - "And he overthrew those cities and all the plain, and all - the inhabitants of the cities, and that which grew upon the - ground. - - "But his wife looked back from behind him, and she became a - pillar of salt. - - "And Abraham gat up early in the morning to the place where - he stood before the Lord: - - "And he looked toward Sodom and Gomorrah, and toward all - the land of the plain, and beheld, and lo, the smoke of - the country went up as the smoke of a furnace." (Gen. xix, - 23-28). - -This is clearly the description of a volcanic eruption, for throughout -the Bible things are described as they appear to be. When Moses speaks -of brimstone and fire being rained upon Sodom and Gomorrah out of -heaven, he is describing the phenomenon as it would appear to one -looking at it. Of course, we know that in volcanic eruptions such -things come to the earth through the crater of the volcano. The lava -is thrown high into the air, and the hardening, but still red hot, -ashes, rain down on the earth from the ash cloud that forms over the -mountain. But, looked at from a distance they appear to fall or be -rained down from the skies. In exactly the same way, Livy, the Roman -historian, tells about showers of stones that fell from heaven on -Mt. Albano near Rome for two whole days during the second Punic War. -So, too, even Pliny, who had some pretensions to be considered a -naturalist, in describing the appearance of Mt. Vesuvius during the -terrible eruption of A. D. 79, when Herculaneum and Pompeii -were destroyed, speaks of the red hot stones and ashes as falling -from above. So, in reality, they did, although, as in the case of the -cities of the plain, the materials forming the cloud came from the -crater of the volcano below. - -As to brimstone falling from the sky, this is by no means an unusual -occurrence during many volcanic eruptions, since sulphur is a common -material, often thrown out of the craters of some volcanoes. - -Note also the statement that, when Abraham rose early in the morning -and looked toward the place where Sodom and Gomorrah stood, he saw -the smoke of the country go up like the smoke of a furnace. This was, -probably, the smoke caused by the burning of the city, or even by the -destruction of the crops in their fields, when ignited by the falling -red hot ashes. It might also have been partly due to the burning of -asphalt thrown out from the fissures in the ground, or to the showers -of volcanic ashes that fell from the cloud formed during the eruption. - -That the cities there were destroyed by a volcano far in the past -appears from things outside of the Bible proper; for Strabo, -the Greek geographer, refers to Jewish traditions that thirteen -flourishing cities were swallowed up by a volcano, and this finds fair -corroboration in the ruins along the western borders of the Dead Sea. - -A writer referring to these eruptions says: - - "The eruptions themselves have ceased long since, but the - effects, which usually succeed them, still continue to be - felt at intervals in this country. The coast in general is - subject to earthquakes, and history notes several which - have changed the face of Antioch, Laodicea, Tripoli, - Berytus, Tyre, and Sidon. In 1793 there happened one which - spread the greatest ravages. It is said to have destroyed - in the valley of Balbec upwards of 20,000 persons." - -Attention has already been called to the fact that the valley of the -Jordan occupies a depressed or sunken region far below the level -of the Mediterranean and the Red Seas. It is the belief of some -geologists that this depression was caused by an earthquake which -accompanied the volcanic eruption that destroyed Sodom and Gomorrah -and the cities of the plain. Indeed, some contend that the present -site of the valley of the Jordan, including the Sea of Tiberius and -the Dead Sea, is a great fissure that was made in the limestone of the -valley during the time of that earthquake. - -It would appear from the peculiar geography of this section of country -that the Jordan River has not always emptied into the Dead Sea, but -that before the time of the destruction of the Cities of the Plain the -greater part of the country now occupied by the Dead Sea was a fertile -valley, and the Jordan emptied directly into the Red Sea at the Gulf -of Akaba; that during the disturbance through changes in the valley, -or possibly by a lava stream flowing across a portion of the bed of -the lower Jordan, or even by a huge accumulation of stones or ashes -thrown out from a neighboring volcano, the discharge of the river into -the Red Sea was cut off, and that in this way the waters of the rivers -began to accumulate and to flow over the plain, thus forming the basin -of the Dead Sea. - -There is no difficulty in accounting for the saltness of the Dead -Sea. There are large quantities of salt, and salty matters generally, -in the volcanic rocks of the region, but, even if this were not so, -when a river empties into a lake with no outlet to the sea, and -which therefore loses its water by evaporation only, the water will -gradually become very salt, since the remaining waters of such a lake -contain more or less salt, while the water they lose by evaporation -contains none. - -The waters of the Dead Sea are very salt, but not the saltest in -the world. In every 100 pounds of Dead Sea water twenty-four pounds -consist of salty matters. The waters of the Great Salt Lake, in Utah, -contain eighteen per cent of salty matters. Lake Van, in eastern -Turkey, is, perhaps, the saltest lake on earth, it containing no less -than thirty-three pounds of salty substances in every 100 pounds of -water. - -Daubeny, an authority on volcanoes, and quite competent to give an -opinion concerning what is possible in this line, describes what he -believes took place, as follows: - - "Briefly then to recapitulate the train of phenomena by - which the destruction of the cities might have been brought - about, I would suppose that the River Jordan, prior to - that event, continued its course tranquilly through the - great longitudinal valley, called El Arabah, into the - Gulf of Akaba; that a shower of stones and sand from some - neighboring volcano first overwhelmed these places; and - that its eruption was followed by a depression of the whole - of the region, from some point apparently intermediate - between the lake of Tiberius and the mountains of Lebanon, - to the watershed in the parallel of 30 deg., which occurs in - the valley of El Arabah above-mentioned. I would thence - infer that the waters of the Jordan, pent-up within the - valley by a range of mountains to the east and west, and a - barrier of elevated table-land to the south, could find no - outlet, and consequently by degrees formed a lake in its - most depressed portion, which, however, did not occur at - once, and therefore is not recorded by Scripture as a part - of the catastrophe, though reference is made in another - passage of its existence _in what was before the valley of - Siddim_." - -As regards the turning of Lot's wife into a pillar of salt, Henderson, -who has carefully studied this part of the country, remarks: "How -natural is the incrustation of his wife on this hypothesis! Remaining -in a lower part of the valley, and looking with a wistful eye towards -Sodom, she was surrounded, ere she was aware, by the lava, which -rising and swelling, at length reached her, and (whilst the volcanic -effluvia deprived her of life) incrusted her where she stood, so that -being, as it were, embalmed by the salso-bituminous mass, she became a -conspicuous beacon and admonitory example of future generations." - - - - -CHAPTER XXXI - -INSTRUMENTS FOR RECORDING AND MEASURING EARTHQUAKE SHOCKS - - -To attempt by the unaided senses a determination of the direction in -which earthquake shocks reach any certain spot, the velocity with -which they are travelling, their degree of intensity, their general -character, whether horizontal or vertical, or any peculiarities which -might show them to be exceptional would be futile for more reasons -than one. Even a skilled scientific observer, familiar with what has -already been discovered and eager to discover more, might in the -excitement of an earthquake become so excited himself as to make him -unable to take reliable observations. - -But human ingenuity has succeeded in devising delicate instruments -capable of recording not only the exact time of the arrival of an -earthquake shock, but also of measuring the different parts of what -may seem to be a single shock, the direction in which the shocks reach -the place, as well as the variations of intensity in all the shocks. - -Crude instruments to do some of these things have been in use from -very early times. According to Mallet among the more important -of these early instruments was the following: the instrument of -Cacciatore of Palmero. This consisted of a circular wooden dish, about -ten inches in diameter, placed horizontally, and filled with mercury -to the brim of eight notches at equal distances apart. Beneath each -notch was placed a small cup. On the passage of the earthquake waves -the vessel, being tilted in a direction dependent on the direction in -which the waves were travelling, would cause some of the mercury to -spill over into one or more of the cups, thus indicating by its amount -the intensity of the wave, and by the particular cup or cups that were -filled, the direction in which the waves reached the place. - -Somewhat similar contrivances were of a vessel partly filled with -molasses, or other sticky liquid; or a cylindrical tub, the sides of -which were chalked or whitewashed and filled with some colored liquid. -In either of these cases, on the passage of the earthquake waves, -the vessels were tilted and showed by the height of the marks the -intensity of the waves, and by the position of the marks the direction -in which the waves first reached the instrument. - -These instruments, though satisfactory for the study of earthquake -shocks a long time ago, when an earthquake was regarded as practically -consisting of but a single shock, or, at the most, of a very few -shocks, would be worthless for the study of earthquakes now, for it is -finally known that an earthquake consists of a series of many hundreds -of vibrations, differing greatly in their rapidity and intensity, and -following one another in a definite order. - -The old forms of earthquake instruments were known as _seismoscopes_. -The word seismoscope is a compound word from Greek consisting of -the two words, seism and scope. It means literally any instrument -capable of seeing, or calling attention to, a seism, or _earth-shake_. -In other words, a seismoscope is any instrument capable of calling -attention only to an earth-shake. - -Of course, neither of the rude seismoscopes just mentioned would be -able to give any valuable indications of the successive shakings to -which the vessel containing the viscid liquid had been subjected, -since the liquid would simply be splashed a number of times over the -same parts of the vessel. In order to get a record of the successive -shocks another form of apparatus must be employed, a form known as a -_seismograph_. - -Concerning the complex character of the apparently single earthquake -shock, Professor Milne makes this highly interesting and picturesque -statement: - - "An earthquake disturbance at a station far removed from - its origin shows that the main movement has two attendants, - one which precedes and the other which follows. The first - of these by its characteristics indicates what is to - follow, whilst the latter, in a very much more pronounced - manner, will often repeat at definite intervals, but with - decreasing intensity, the prominent features of what - has passed. Inasmuch as these latter rhythmical, but - decreasing, impulses of the dying earthquake are more - likely to result from reflection than from interference, I - have provisionally called them Echoes." - -There are many different forms of instruments known as seismographs -that are capable of recording all of these vibrations, but there is -this objection to their use: that the records appear in so tangled a -form that it is practically impossible to decipher or untangle them. -This fact can be grasped by examining Fig. 51, which represents a -record of this kind. - -[Illustration: FIG. 51. COMPLEX RECORD OF SEISMOGRAPH] - -It is necessary, therefore, to employ a modified form of instrument -called a _seismometer_, able not only to record all the different -vibrations, but to record them in such a manner that they can be -easily recognized. Fig. 52, for example, shows results obtained by the -use of a seismometer, in which the different vibrations are separated, -and so recorded on a sheet of paper, as to be readily understood. Such -a record is called a _seismogram_, and represents a _long distance -seismogram_. Here the large arrow indicates the beginning of the -record. And herein, as can be clearly seen, what would appear to an -observer without an instrument only a single shock, lasting but the -fraction of a minute, in reality consists of the _preliminary shake_ -as represented in ab and bc, the _principal shake_, as represented -at c, d1, d2, and d3, and the _final portions of the shake_ or the -"echoes" of Professor Milne, as represented from d3 to e. - -[Illustration: FIG. 52. LONG DISTANCE SEISMOGRAM] - -Except in a very general way there is for present purposes no need -of explaining the construction and operation of the seismometer -and seismograph. Suffice it to say, there are many forms of these -instruments, any of which are capable of recording the details of a -passing shock. The most important thing in either a seismograph or a -seismometer is to obtain what is known as a _steady point_; that is, a -point consisting of some object or mass that will remain practically -at rest, while everything around it, even the support which holds it, -is affected by the earthquake. - -It is, of course, not very easy to obtain a steady point, but it can -be done; and it will be at once comprehended that if a plate or piece -of paper were attached to such a steady point or mass, and a pencil -or tracer had one of its ends resting on the plate, and its other end -attached to the support that vibrates with the earth, a tracing or -record would be drawn on the plate from which the character of the -motion of the end of the tracer, and, therefore, of the earth, would -be marked on the plate. - -[Illustration: FIG. 53. VICENTINI VERTICAL PENDULUM] - -Various devices have been employed for the steady points. The most -successful consists of a heavy mass of lead. - -Fig. 53 represents a form of instrument invented by Professor -Vicentini of Italy. Here the steady point consists of a heavy leaden -bob, of 200, 400, or even 500 kilograms, suspended by three metallic -rods united above by a brass cap, hung on a steel wire to a bracket -fixed on the wall. This wire may have a length as great as fifty feet. - -[Illustration: FIG. 54. VICENTINI PENDULUM AND RECORDER] - -Fig. 54 represents the recording instrument. Here a tracer is provided -that is capable of multiplying the motion fifty times, or even eighty -times. A record is traced on a sheet of paper passing over a roller -which imparts a rapid motion to a sheet so as to make sure that the -different parts of the shock or vibration will be recorded on separate -portions of the paper. - - - - -CHAPTER XXXII - -SEAQUAKES - - -As earthquakes are shakings of the earth's crust in places where it is -uncovered by the waters of the ocean, so _seaquakes_ are the shakings -of those portions that lie on the bed of the ocean. - -Mallet points out that the earthquake wave may start either in the -interior of the continent, or on the bed of the ocean; that the latter -place is the more common, since on the land vents--rude safety-valves, -as it were,--are provided by the craters of the volcanoes; that, when -earthquakes start on the ocean bed, the impulses are conveyed in -different forms of waves, i. e., those through the solid earth, those -through the water, and those through the air, with varying sounds like -bellowings and explosions, or like the rolling of wagons over rough -roads. - -To learn when quakes occur on the sea is a much harder task, since on -the land we can use seismoscopes, seismographs, or seismometers to -indicate, record, or measure the shakings of the crust, while on the -sea, where the water is always in more or less motion and the surface -so far from the ocean's bed this is impossible, or, rather shall it -be said, has hitherto been found so; for that the mind of man may -surmount this obstacle is not impossible to conceive. - -To detect the wave produced by the quaking of the bed of the ocean -is exceedingly difficult, since those in very deep water are flat or -possess but a small height. Indeed, in the deepest parts of the ocean -this height is probably to be measured only by inches instead of feet. -When, however, the waves advance towards the shore they increase in -height, and when they reach the shallows near the coast, they begin -to curl over and break, thus creating the enormous waves mentioned so -often as attending great earthquakes in the ocean. - -During the great earthquake of Simoda in Japan, 1854, the waters of -the bay were first greatly agitated, and then retreated, leaving the -bottom bare in places where the water was formerly thirty feet deep. A -wave, thirty feet high, then rushed in from the bay and, climbing the -land, swept away everything in its path, covering the town with water -to the tops of the houses. This monster wave then receded, but rushed -back five times. - -In 1751, an earthquake wave suddenly entered Callao, the port of Lima, -Peru, sinking twenty-three vessels and driving a frigate inland, where -it was left high and dry. This wave extended across the Pacific to the -Hawaiian Islands, a distance of 6,000 miles. - -On the 13th of August, 1866, an earthquake wave, that started a short -distance from shore, produced a number of earthquake waves sixty feet -high that reached the coast of Peru half an hour after the principal -earthquake shock. These waves reached Coquimbo, 800 miles distant, -in about three hours, and Honolulu, on the Sandwich Islands, 5,520 -miles distant, in twelve hours, and the coast of Japan, more than -10,000 miles distant, on the next day. Le Conte remarks that these -waves would have encircled the earth, had it not been for the barrier -interposed by the Andes. - -Another great seaquake, known as the Iquiqui seaquake, during 1868 in -the same neighborhood damaged severely the towns of north Chile and -southern Peru. - -While, however, there is difficulty in readily observing the -earthquake waves that form in the deep ocean, yet such is at times the -violence of an earthquake that there is no difficulty in detecting its -presence, even in deep water. Dr. Rudolph has made a careful study of -the evidences of earthquakes produced in the deep sea, from a careful -examination of a great number of the logs of ships. Logs, as everybody -knows, are books in which the captain or commanding officer makes -careful entries of all important happenings to the vessel, conditions -of the weather and of the sea. From this source Dr. Rudolph obtained -considerable information of much value concerning these phenomena. - -I have already called your attention to portion of the Atlantic Ocean -lying near the Equator, in the warmest part of the ocean, between -Africa and South America, as being a region especially liable to -submarine volcanic showers. While, generally speaking, there is -nothing in this region to indicate the probability of submarine -disturbance, yet suddenly, if a vessel happens to pass directly over -the point of origin of the quake, there ensues a great quaking or -quivering. Loose objects on the ship begin to shake and clatter. -Noises arise from some invisible point deep down in the ocean. The -disturbance grows, the noises begin to resemble distant thunder, the -ship trembles and staggers as though it had struck rocks, and many -believe she is about to go down; when, as suddenly as it began, the -commotion ceases, the noises stop, and the ship shapes her course as -calmly, and as gallantly, as before. - -Rudolph gives two excellent examples of seaquakes in this region, both -of which were, doubtless, due to submarine eruptions. - -On the 25th of January, 1859, as the ship _Florence_ was in lat. -0 deg. 48' N., long. 29 deg. 16' W., about ten miles N. W. by N. from St. -Paul's Rock, the people on board felt a sudden shock that began with a -rumbling sound like distant thunder. This lasted only forty seconds. -The glass and dishes of the vessel rattled so violently that it was -feared they would be broken. The shakings were so strong that several -objects on the vessel were thrown down. Everyone believed the ship -had struck on rocks. The captain leaned over the taffrail in order to -see the position of the reef, but soon saw that the vessel had struck -nothing, and informed his crew "it was only an earthquake shock." - -Another of the log books examined by Rudolph was that of a ship in the -same part of the Atlantic Ocean. This record showed that suddenly on -a morning, in 1883, strange noises were heard that soon increased and -became not unlike the firing of great guns or the peals of distant -thunder. The ship vibrated as if its anchor had been suddenly let go, -and at the same time a feeling came over all the crew, as if they had -been electrified. - -In some cases the vibrations were sufficiently severe to throw heavy -objects from the deck, as appears in an account given by a French -geologist of a quake in the Mediterranean off the shores of Asia Minor. - -"Our ship was over the epicentre,"[5] he says, "and was so severely -shaken that at first the Admiral feared the complete destruction of -the corvette." He then makes the statement that the shocks which were -directly upwards were so strong as to throw heavy objects in the air; -for example, a heavy gun and its carriage. While it is possible, as -Dutton remarks, that this incident of the heavy gun and carriage was -grossly exaggerated, yet it should not be forgotten that in the case -of submarine eruptions such as that which resulted in the production -of the island of Sabrina, an immense column of water, weighing -probably many times more than a gun and its carriage, was observed to -be shot high into the air. - -Where the seaquake is produced by a strong submarine volcanic -eruption, there is a violent commotion of the water itself, so that a -vessel passing over such a point may be greatly injured, and, indeed, -even destroyed. Such disasters, however, are fortunately exceedingly -rare. - -Among other common effects of seaquakes is the destruction of fish -already mentioned by the sudden blow to the water stunning and killing -them, just as the explosion of dynamite or other high explosives does -in a lake or pond. - -The most marked effect, however, of seaquakes is the starting of the -great wave on the coasts of continents and islands. - -There are certain parts of the ocean that are especially liable to -seaquakes. Some of the more important of these, as shown by Rudolph's -researches, are: - -The region already referred to in the narrowest parts of the Atlantic -Ocean between Africa and South America almost immediately under the -equator. Here there are two well marked regions. One is in lat. 1 deg. -N., long. 30 deg. W., where there is a submarine ridge, the tops of which -form what are known as St. Paul's Rock. The ocean here is very deep, -the slopes of the ridge descending rapidly. It is on these slopes -that earthquakes are very apt to occur just as they do on the steep -slopes of mountain ranges. The other region, called by Rudolph the -_Equatorial District_, lies a little further to the east on both sides -of the equator in long. 20 deg. W. - -It appears from Rudolph's researches that between 1845 and 1893 no -less than thirty-seven seaquakes were reported in the logs of ships -in the neighborhood of St. Paul's Rock, and between 1747 and 1890, in -the equatorial district, there were forty-nine seaquakes. It must not -be supposed, however, that these were all the quakes in the regions -during these times, since, of course, many shocks must have happened -that were not felt even by vessels in the neighborhood and many more, -when this portion of the ocean was free from any craft. - -In the North Atlantic there is a portion of the ocean's bed known as -the _West Indies Deep_. Here the bed is marked by great depths and by -many irregularities and is, therefore, a region where seaquakes are -common. - -Still another district is found in the North Atlantic in the -neighborhood of the Azores. This is the region in which the Lisbon -earthquake is believed to have started. - -Another region where seaquakes are common is in the Pacific along the -coast of South America from the equator to 45 deg. S. lat. "Here," says -Dutton, "especially in the vicinity of the angle where the Peruvian -and Chilian coasts meet have they been most numerous and formidable. -The harbors of Pisco, Arica, Tacua, Iquiqui, and Pisago have been -repeatedly subject to these destructive invasions." - -There has been considerable discussion as to the exact manner in which -the earthquake waves are set up. Whatever be the cause or causes, -the action must be sudden, such as an upheaval of the bottom, or a -collapse of a large section of the ocean's bed, with a dropping of a -vast body of water. Or, possibly, a submarine volcanic eruption causes -the water to lift suddenly under pressure of steam generated by escape -of the lava and other hot volcanic products. - -Dr. Rudolph attributes earthquake waves to submarine volcanic -eruptions alone. It would seem, however, as if each one of the other -things above referred to might at times be the direct cause. - - - - -CHAPTER XXXIII - -THE DISTRIBUTION OF EARTHQUAKES - - -Earthquakes may occur at any part of the earth's surface, at any time -of the day, or at any season of the year, yet they are more frequent -at certain parts, certain hours, certain seasons. - -Since some earthquakes are unquestionably connected with volcanic -eruptions, a map or chart of the volcanoes of the earth would also, -to a certain extent, show the parts of the earth that are likely to -be visited by earthquakes. Since, however, by far the most severe -earthquakes are not directly connected with volcanoes, but are due to -sudden slips of faulted strata, a volcanic chart would necessarily -fail to indicate accurately the principal earthquake regions. - -In the preparation of a map showing the distribution of earthquakes -over the earth's surface, Mallet adopted the plan of colorings or -tintings in such a manner that the depth of the colors would represent -not only the parts shaken, but also the relative number of times -shaken, as well as the intensity of the shocks. In order to determine -the depth of tint to be employed, Mallet divided earthquakes into the -following classes according to their intensity: - -_Great earthquakes_, or earthquakes of the first class; or those in -which the area affected is of great size, in which many cities have -been overthrown, and many people killed, and parts of the surface -greatly altered. - -_Intermediate earthquakes_, or those in which, although the area -affected is great, yet the destruction of buildings, or loss of life, -has been comparatively small. - -_Minor earthquakes_, or those which, although capable of producing -small fissures in the crust, generally leave but few or no traces of -their occurrence. - -The greatest distance to which earthquake waves of the first class -extend is taken by Mallet as being over a diameter of 1,080 miles; -those of the second class over a diameter of about 360 miles, and -those of the third class over a diameter of about 120 miles. - -According to the Rossi Forel scale already given, earthquake shocks -are divided according to their relative intensity into ten separate -classes, viz.: I. The micro-seismic; II. The extremely feeble; III. -The very feeble; IV. The feeble; V. The moderately intense; VI. -The fairly strong; VII. The strong; VIII. The very strong; IX. The -extremely strong; X. Shocks of extreme intensity. - -An earthquake map prepared according to Mallet's scale would show a -greater depth of color or tint in the neighborhood of the volcanic -districts of the earth and especially in the neighborhood of the -mountain regions, where tectonic quakes are most frequent. Oceanic -areas would be left almost untinted, not because earthquakes do not -occur on the bed of the ocean, but because of the difficulty of -observing such earthquakes at great distances from the land. So far -from earthquakes being absent on the bed of the ocean it is most -probable that they are more frequent there than elsewhere. - -Prepared in this way, Mallet's map would show a preponderance of -earthquakes along the borders of the continents, especially along the -"Great Circle of Fire" on the borders of the Pacific Ocean. - -Dutton as well as some others assert that the "Great Circle of Fire" -on the shores of the Pacific has in reality no existence; that, -instead of there being a continuous region of volcanoes, there is in -reality nothing more than a considerable number of volcanoes arranged -in groups along the borders of this ocean, but separated by spaces -containing no marked volcanic activity. We do not think this a tenable -position, since it is well known that volcanoes lie along great lines -of fissures at different points or openings which are kept open -by subsequent volcanic activity, while the remaining portions are -closed soon afterwards; and, moreover, in parts of these so-called -non-volcanic regions, there are probably extended regions of extinct -volcanoes. - -Since the time of Mallet many maps have been made to show the -distribution of earthquakes. Among the best of such is that by M. de -Montessus de Ballore. - -Some idea of the great amount of work required for the preparation of -Montessus' map may be formed when one learns that the catalogue of -earthquakes collected by him for this purpose included for the years -1880 to 1900, 131,292 quakes. - -De Montessus' earthquake map divides the grand divisions of the earth -into numerous sub-divisions, too numerous, indeed, for even brief -description in a work of this kind. From the map he thus laboriously -prepared De Montessus drew the following general conclusions: - -1. The parts of the earth that are most apt to be shaken by -earthquakes are those which possess the greatest differences of relief -between their highlands and lowlands, and that in such regions the -most pronounced earthquakes are found on the steepest slopes. - -2. Earthquakes are most common along those parts of the crust that are -thrown up in huge wrinkles, or mountain ranges, whether these masses -be above the level of the sea or are covered by it. - -[Illustration: FIG. 55. DAVISON'S EARTHQUAKE MAP OF JAPAN] - -3. Earthquakes are more common in mountainous districts than in -plains. But not all mountains are characterized by earthquakes nor -are all plains free from them. Sometimes the plain at the base of -the mountain appears to be especially liable to shocks, probably by -reason of slips along faults at these points. - -The great mountain ranges of the world are generally characterized -by unequal slopes, the long gentle slope facing the interior of the -continents, and the short, abrupt slopes being turned towards the -coast. Now, Montessus points out that volcanoes are the most frequent -on the short, abrupt slopes. In some cases, however, where the long -slopes are the roughest, it is these slopes that are most frequently -shaken. - -The beds of the ocean that lie along rapidly descending lines, -especially when they lie on the borders of large mountain ranges, are -especially liable to earthquakes. - -Dr. Charles Davison has made a map of the earthquakes of Japan in -which he had adopted the plan of representing the origin or centres -of earthquakes by a series of contour lines like those employed on -topographical maps. The advantage of this type of map over that -employed by Mallet is just this: Davison's earthquake map of Japan in -which the active volcanoes are marked by dots, and the earthquakes -by contour lines surrounding the points of origin, discloses the -interesting fact that here the positions of the volcanoes and the -earthquake centres coincide, since the mountainous districts where the -active volcanoes are numerous are singularly free from earthquakes. -This can be seen from an inspection of Fig. 55. - - - - -CHAPTER XXXIV - -THE CAUSES OF EARTHQUAKES - - -Earthquakes occurred long before man appeared on earth. It is natural, -therefore, that our early ancestors, experiencing these unwelcome -phenomena, vaguely endeavored to explain their causes. These early -attempts at explanation have in many cases been of an exceedingly -fanciful character. - -The ancient Mongolians and Hindoos declared that earthquakes are due -to our earth resting on a huge frog and that they occur whenever the -frog scratches its head. - -In Japan, where earthquakes are very common, the ignorant people even -at a much later day declared that there exists in the depth of the sea -an immense fish which, when angry, dashes its head violently against -the coast of the island, thus making the earth tremble. This is, -doubtless, the biggest fish-story extant. - -Another folk-lore explanation in Japan attributes the cause of the -tremblings of the earth to a subterranean monster whose head lies in -the north of the island of Hondo, while his tail lies between the two -principal cities. The shaking of his tail causes earthquakes. - -Fantastic and foolish as these explanations are, it is worthy of -note that the first of the Japanese explanations shows no little -observation on the part of the people, since it locates the -starting-points of earthquakes as being not on the land, but on the -bottom of the sea. In point of fact, nearly all the great earthquakes -in Japan seem to start somewhere between the coasts of the islands -on the sea-bottom that leads down to a very deep part of the Pacific -known as the Tuscarora Deep. - -Many years ago nearly everyone believed that earthquakes were caused -solely by the forces that produce volcanic eruptions; that all -earthquakes, whether in the neighborhood of active volcanoes, or at -great distances therefrom, were to be regarded solely as volcanic in -their origin. - -It is now recognized that the most severe and far-reaching earthquakes -have no immediate connection with volcanic explosions, but are due to -the sudden slippings of the earth's strata over lines of faults; or, -in other words, earthquakes are most frequently of the tectonic type. - -At the present time there is unfortunately much difference in -opinion as to the exact cause of earthquakes. By this is not meant -the immediate cause, but the ultimate cause. As to the immediate -cause, practically all are agreed that quakes of volcanic origin are -to be traced to the same forces that produce volcanic eruptions, -while quakes of tectonic origin are due directly to the slipping of -the strata along the faults. But when inquiry is instituted as to -the nature of the forces that cause the volcanic eruptions, or that -produce such an alteration of the strata as permits them afterwards to -slip and thus jar the earth, there is much difference of opinion. - -As can be seen from a few quotations of well-known authorities, only -two kinds of earthquakes exist; namely, volcanic earthquakes and -tectonic earthquakes. - -Dana, for example, while acknowledging that small earthquakes may be -caused by the sudden falling of large rock masses into cavities in the -crust of the earth, says: - - "But true earthquakes come, for the most part at least, - from one or the other of the following sources of - disturbance. - - "1. Vapors suddenly produced, causing ruptures and friction. - - "2. Sudden movements or slips along old or new fractures. - - "Earthquakes due to the former of these methods are common - about volcanoes, and at the Hawaiian islands shakings that - are destructive over the island of Hawaii at the moment of - some of the more violent eruptions, do not often affect the - island of Oahu, a depth of 500 fathoms of water, the least - depth between the two islands, being sufficient to stop off - the vibrations.... - - "Earthquakes of the second mode of origin may occur in all - regions, volcanic or not. They have their origin mostly in - the vicinity of mountain regions, where old fractures most - abound. The vibrations may begin in a slip of a few inches, - in fact; but where there has been a succession of slips, - up and up from 10,000 feet or more, as in the Appalachian, - earthquakes of inconceivable volcanic activity must have - resulted." - -Dana points out that volcanoes stand on lines of fractures in the -openings of which their existence began and that, during geological -time, slips up or down these fractures have occurred, producing -earthquakes and possibly starting eruptions. - -Prestwich, a well-known English geologist, speaks very decidedly -concerning the causes of earthquakes: - - "For my own part, I am disposed to share the belief - expressed by Dana that the tension or pressure, by which - the great oscillations or plications of the earth's crust - have been produced, have not entirely ceased; and that - this is generally the most probable cause of earthquakes. - The uplifting of the great continental tracts and mountain - ranges must have always left the interior of the crust in - a state of unstable equilibrium, and any slight slide or - settling along an old fracture, or in highly disturbed and - distorted strata, would be attended by an earthquake shock. - - "In volcanic areas the removal of the large volumes of - molten rock from the interior to the surface must produce - settlements and strains which might also result in some of - these minor earthquakes to which volcanic districts are - so subject. Where we have the two conditions combined, as - they are in the Andes in South America, these earthquake - phenomena are, as we should expect, developed on the - grandest and widest scale." - -Geikie, the Scotch geologist, says: - - "Various conceivable causes may, at different times - and under different conditions, communicate a shock to - the subterranean regions. Such as the sudden flashing - into steam of water in the spherodial state, the sudden - condensation of steam, the explosion of a volcanic outpour, - the falling in of the roof of a subterranean cavity, or the - sudden snap of deep-seated rocks subjected to prolonged and - intense stress." - -Sir Charles Lyell, the great English geologist, holds the following -views concerning the origin of earthquakes. He speaks as follows in -his "Principles of Geology": - - "1. The primary cause of the volcanoes and the earthquakes - are to a great extent the same, and connected with the - development of heat and chemical action at various depths - in the interior of the globe. - - "2. Volcanic heat has been supposed by many to be the - result of the high temperature which belonged to the - whole planet when it was in a state of igneous fusion, - a temperature which they suppose to have been always - diminishing and still to continue to diminish by radiation - into space.... - - "The powerful agency of steam or aqueous vapor in volcanic - eruptions leads us to compare its power of propelling lava - to the surface with that which it exerts in driving up - water in the pipe of an Icelandic geyser. Various gases - also, rendered liquid by pressure at great depths, may - aid in causing volcanic outbursts and in fissuring and - convulsing the rocks during earthquakes." - -Major Clarence Edward Dutton, U. S. A., an acknowledged authority on -seismology, speaks as follows: - - "Thus far, then, we have two causes of earthquakes which - are apparently well sustained: (1) the downthrows, which - have often been observed to be accompanied by earthquakes, - and (2) volcanic action. But neither of them have been - shown to be connected with more than a comparatively small - number. Much the greater part of the earthquakes still - require explanation, and the indications are manifold that - some of them are produced by some cause yet to be stated." - -He acknowledges, however, this unknown cause may be traceable to -volcanic agency. To quote him in full: - - "It remains now to refer to the possibility that many - quakes whose origin is unknown, or extremely doubtful, may, - after all, be volcanic. This must be fully admitted, and, - indeed, it is in many cases highly probable. Evidences - that volcanic action has taken place in the depths of the - earth without visible, permanent results on the surface - abound in ancient rock exposures. Formations of great - geological age, once deeply buried and brought to daylight - by secular denudations, show that lavas have penetrated - surrounding rock-masses in many astonishing ways. Sometimes - they have intruded between strata, lifting or floating up - the overlying beds without any indication of escaping to - the surface. Sometimes the lava breaks across a series of - strata and finds its way into the partings between higher - beds. Or it forces its way into a fissure to form a dike - which may never reach the surface. In one place a long arm - or sheet of lava has in a most surprising and inexplicable - manner thrust itself into the enveloping rock-mass, and in - the older or metamorphic rocks these offshoots or apophyses - cross each other in great numbers and form a tangled - network of intrusive dikes. In other places the intruded - lava has formed immense lenticular (lense shaped) masses - (laccolites), which have domed up the overlying strata - into mountain masses. These intrusions, almost infinitely - varied in form and condition, are often, in fact usually, - inexplicable as mechanical problems, but their reality is - vouched for by the evidence of our senses. What concerns - us here is the great energy which they suggest and their - adequacy to generate in the rocks those sudden, elastic - displacements which are the real initiatory impulses of an - earthquake. They assure us that a great deal of volcanic - action has transpired in past ages far under ground, which - makes no other sign at the surface than those vibrations - which we call an earthquake." - -Koto, the celebrated Japanese student of earthquakes, and a member -of the Earthquake Investigation Committee appointed by the Japanese -Government for studying the great Mino-Owaro earthquake, in Japan, -1891, is properly regarded as an authority on earthquakes. Living, as -he does, in a country where earthquakes and volcanic eruptions are of -almost daily occurrence, he has had abundant opportunity for studying -these phenomena, especially in connection with the Seismological -Institute of Japan. He speaks as follows: - - "To make clear once for all my own standpoint, I may say - plainly that the chain of volcanoes and the system of - mountains of the non-volcanic earthquake, appear to me - to have very intimate and fundamental relations with the - so-called tectonic line." - -Mallet regards earthquakes that can be directly traceable to volcanic -origin as unsuccessful efforts on the part of nature to establish -volcanoes. He speaks concerning this matter as follows: - - "An earthquake in a non-volcanic region may, in fact, be - viewed as an uncompleted effort to establish a volcano. - The forces of explosion and impulse are the same in both; - they differ only in degree of energy, or in the varying - sorts and degrees of resistance opposed to them. There is - more than a mere vaguely admitted connection between them, - as heretofore commonly acknowledged--one so vague that the - earthquake has been often stated to be the cause of the - volcano (Johnson, 'Phy. Atlas,' Geology, page 21), and more - commonly the volcano the cause of the earthquake, neither - view being the expression of the truth of nature. They are - not in the relation to each other of cause and effect, but - are both unequal manifestations of a common force under - different conditions." - -Before closing this chapter on the causes of earthquakes it may be -well to state briefly the explanations that have been suggested by -those who hold that the earth is solid and cold throughout its entire -mass, except that in the neighborhood of volcanic districts there -are limited areas situated only a comparatively few miles below the -surface where the rocks are highly heated. - -Professor Mallet suggested that the source of heat for these local -areas of melted rocks was to be found in the enormous mechanical force -that is developed by the crushing of the strata in the earth's crust. -The principal objection to Mallet's theory is to be found in the -fact that, for this heat to be available for the melting of rocks, -it must be produced rapidly, and not spread out over long periods of -time. Moreover, there would appear to be no other way to account for -the production of the great force required to effect the crushing of -the earth's strata save on the assumption of a highly heated interior -still cooling and contracting. - -In his "Aspects of the Earth" Shaler has suggested an hypothesis -that may be regarded to a certain extent as explaining how heat, -slowly generated, might be blanketed, or prevented from escaping and -so possibly reaching a temperature sufficiently high to melt the -materials in portions of the interior not far below the surface of the -earth. - - "We thus see that in the water imprisoned in the deposits - of the early geological ages and brought to a high - temperature by the blanketing action of the more recently - deposited beds, we have a sufficient cause for the great - generation of steam at high temperatures, and this is the - sole essential phenomenon of volcanic eruptions. We see - also by this hypothesis why volcanoes do not occur at - points remote from the sea, and why they cease to be in - action soon after the sea leaves their neighborhood.... - - "The foregoing considerations make it tolerably clear that - volcanoes are fed from deposits of water contained in - ancient rocks which have become greatly heated through the - blanketing effects of the strata which have been laid down - upon them. The gas which is the only invariable element - of volcanic eruptions is steam; moreover, it is the steam - of sea-water, as is proven by analysis of the ejections. - It breaks its way to the surface only on those parts of - the earth which are near to where the deposition of strata - is lifting the temperature of water contained in rocks by - preventing, in fact, the escape of the earth's heat." - -Another very common theory is that of chemical action, or the heat -produced by the oxidation of various substances inside the earth, -such, for example, as iron pyrites, a compound of iron and sulphur. - -When Sir Humphrey Davy discovered metallic sodium and it was found -that this material, when thrown on water, possessed the power of -liberating intense heat, the discovery was welcomed by geologists -as affording a possible explanation of the cause of volcanoes and -earthquakes. - -It may be said generally concerning chemical action as the source -of the earth's interior heat, that the chief objection against it -is the fact that such heat is liberated too slowly to result in the -production of a very high temperature. This objection does not exist -in the case of such substances as metallic sodium, since here the -heat is rapidly developed and is sufficient in amount to fuse the -substances produced. But in the lava produced in such great quantities -as it is in volcanic districts there must be liberated at the same -time large quantities of gaseous hydrogen. Now, although hydrogen -is, as we have already seen, sometimes given off with the gases that -escape from volcanic craters, yet the quantity which escapes is so -small that this theory of volcanic activity has been practically -abandoned. - -Quite recently, however, among the various chemical substances that -are produced under the extremely high temperatures of the electric -furnace have been found, or formed, a number of curious substances -such as _calcium carbide_, _calcium silicide_, _barium silicide_, -etc., that possess the property of becoming highly heated on coming in -contact with water. - -Now it is an interesting fact that the hydrogen and other gases -which are given off by the action of water on these substances are -absorbed in large quantities by the materials themselves, so that the -objection of the absence of hydrogen and similar gases in the craters -of the volcanoes would not be quite as objectionable as in the case of -such substances. - -Of course, it is impossible to say whether such substances as calcium -carbide, etc., actually exist inside the earth's crust, yet, as -has been pointed out, the principal condition necessary for their -formation, i. e., a high temperature, existed at times long after -the earth, assuming the correctness of the nebular hypothesis, was -separated from the nebulous sun. - -There still remains to be discussed the most curious of all possible -causes that have been suggested for the presence of the local heated -areas at comparatively short distances below the earth's crust; -namely, radio-activity. - -In 1896, Henri Becquerel, a Frenchman, while investigating the power -of the X-rays, when passing through certain substances, to produce -phosphorescence, or causing the substances to shine in the dark, -made the extraordinary discovery that some of the salts of uranium -possess the power of emitting a peculiar radiation closely resembling -the X-rays, that is able to pass through substances opaque to -ordinary light as well as to affect photographic plates. But the most -extraordinary part of this discovery was that the salts of uranium -apparently possess the power of giving out this radiation continuously -without being exposed to the sun's rays. - -This peculiar property was called _radio-activity_, and was shortly -afterwards found to be present in many other substances besides -uranium, and notably so in two newly discovered elements known as -polonium and radium. - -Now it has been suggested that if there existed somewhere beneath the -earth's crust in these locally heated areas, large quantities of -radio-active substances, these regions would at last become highly -heated, and in this way likely to produce volcanoes and earthquakes. -It would not, however, seem that this is probably their true cause. - -From what has just been said it is clear how exceedingly difficult it -has become to explain the source of the earth's interior heat when -the fact of the earth's original highly heated condition is denied. -We are, therefore, disposed with Russell to believe, as stated in the -first part of this volume, that the ultimate cause of both volcanoes -and earthquakes is to be found in the gradual cooling of an originally -highly heated globe, and that the greater part of the interior is -still in a highly heated condition, hot enough to be melted but yet -in a solid condition by reason of the great pressure to which it is -subjected. - - - - -CHAPTER XXXV - -EARTHQUAKES OF THE GEOLOGICAL PAST--CATACLYSMS - - -There were numerous volcanoes in the geological past; therefore, since -volcanic eruptions are generally attended by earthquake shocks, it -follows that during that remote past the earth has been violently -shaken by earthquakes. Indeed, if we assume, as we believe to be the -case, that the cause of earthquakes is correctly to be traced to an -originally heated globe which is gradually cooling, it follows that -the earth was necessarily subject to great earthquakes almost from the -time when it began to cool. - -But to establish as a fact the occurrence of an earthquake at so -remote a time in the earth's history is far more difficult than to -detect the occurrence of a volcano at that time. While the earthquake -shocks may produce fissures in the earth's crust, and may be -accompanied by great changes of level, yet the great time that has -elapsed between such occurrences and the present would permit the -various geological agencies that are at work either to cover these -fissures completely, or completely to remove by erosion, or in other -similar ways, the rocks in which they occurred. It is different in -the case of a volcano; for the volcanic craters are in many cases -still left standing, and then there are the voluminous sheets of lava -that have spread over great areas of the earth, as well as numerous -volcanic cones. Besides, there are thousands of square miles of -surface that have been covered, often to great depths, by deposits of -volcanic dust thrown out at one time or another from the craters of -the then active volcanoes. - -I am sure you will acknowledge that any force capable of causing great -cracks or fissures in the earth's crust, must, while doing this, have -produced violent shakings of the earth. Great cracks or fissures are -to be found in the rocks of all the geological formations. These are a -record of the earthquakes that must have attended these convulsions. -And there is plenty of evidence to show that the earth's crust has -been torn into these fissures in places deep down below the present -surface; for, by the action of water, many of these portions have -been uncovered so that these great cracks or fissures which have been -afterwards filled with a molten rock that has hardened can be seen in -the great dikes that still remain. - -But there are still other evidences of the existence of earthquakes -during the geological past. There are found in the different strata -of the earth's crust fossil remains of the plants and animals that -lived on the earth long before the creation of man. By a careful study -of these fossils we know positively the kinds of animals and plants -that lived on the earth, in its waters, or in its atmosphere, when -these strata were being deposited. It is in this way possible for a -geologist to trace the life of the earth and its development as it -is written on the great book of which the earth's different strata -form the separate pages. Now, a careful study of the earth's fauna -and flora during the geological past, shows, beyond any question, -that occasionally great changes have occurred in the earth; for, here -and there, during different times, we find that certain species of -animals and plants have completely disappeared, to be followed, after -certain intervals, by entirely different species. It is evident, -therefore, that changes have occurred that have made it impossible for -the animals and plants that formerly lived on the earth to exist under -the changed conditions. These occurrences are known to geologists -as _exterminations_, _catastrophes_, or _cataclysms_. They are also -sometimes called _revolutions_, for they mark a more or less complete -wiping-out of the animals living at the time they occurred. - -If you will try to think you will readily understand how great a -catastrophe must be, that would be able to wipe out or completely -destroy an entire race of animals. - -You have doubtless read with astonishment the terrible catastrophe -that accompanied the eruption of Krakatoa, especially at the loss of -life and property caused by the great waves that were set up in the -ocean, but far reaching as these losses were they have nevertheless -affected but a limited portion of the earth. The plain truth is even -more stupendous, for catastrophes of the geological past appear to -have been so far-reaching and powerful as to affect the whole surface -of the earth, and to have annihilated entire races of animals and -plants as if they had never existed. - -Geologists are all practically agreed that there are only two ways in -which such exterminations of the earth's life could have been caused, -and these are changes in the earth's climate, or the starting of waves -in the sea by great earthquakes. In the sea; for it must be borne -in mind that in the geological past the greater part of the earth's -surface was covered by water, and the land areas were comparatively -small and low, so that waves created by earthquakes might easily have -overwhelmed the entire land surface. - -Of course, it is fair to suppose that in many cases these -exterminations may have been caused by sudden changes of climate, such -as would naturally have resulted from any change in the direction -of hot ocean currents which formerly flowed from the equator to the -poles. The appearance of a fairly large mass of land in the central -parts of the ocean might readily have turned aside the hot ocean -currents that formerly swept over the polar regions, thus greatly -lowering the earth's average temperature in these regions. - -But it seems probable that the principal cause of the destruction of -life in the geological past was produced by earthquake waves in the -sea, sweeping over the continents. Let us, therefore, examine two of -the earth's principal geological revolutions or cataclysms; namely, -that which occurred at the close of an early geological time known as -the Palaeozoic, and that which occurred at the end of a geological -time intermediate between the Palaeozoic time or the time of ancient -life, called the Mesozoic time, and the Cenozoic time, or the time -immediately preceding the present time. These two revolutions are -called by Dana, _the Post-Palaeozoic_, or _Appalachian Revolution_, -and the _Post-Mesozoic Revolution_. Both were characterized by the -making of great mountain systems, and were, therefore, especially -liable to repetitions of tremendous earthquakes that must have -produced enormous waves in the ocean. - -"Palaeozoic time," says Dana, "closed with the making of one of the -great mountain ranges of North America--the Appalachian, besides -ranges in other lands, and in producing one of the most universal and -abrupt disappearances of life in geological history. So great an event -is properly styled a revolution." - -Towards the close of the Palaeozoic time immense disturbances of -the earth's crust occurred during the uplifting of the Appalachian -Mountain System. One may, perhaps, form some faint idea of the -immensity of the forces at work, from the fact that there were -great faults produced by the uplifting of the lands attended with -displacement amounting to 10,000 or 20,000 feet or more; that in parts -of southwestern Virginia there were flexure faults 100 miles in length. - -As to the probability of the extensive exterminations that have -occurred during these times being produced by earthquake waves, Dana -speaks thus: - - "The causes of the extermination are two.... (1) a colder - climate.... (2) earthquake waves produced by orogenic - movements (movements producing mountain ranges). If North - America from the west of the Carolinas to the Mississippi - Valley can be shaken in consequence of a little slip along - a fracture in times of perfect quiet (the allusion here - to the Charleston earthquake, in 1886), and ruin mark its - movements, incalculable violence and great surgings of - the ocean should have occurred and been often repeated - during the progress of flexures, miles in height and - space, and slips along newly opened fractures that kept up - their interrupted progress through thousands of feet of - displacements.... - - "Under such circumstances the devastation of the sea-border - and the low-lying land of the period, the destruction of - their animals and plants, would have been a sure result. - The survivors within a long distance of the coastline - would have been few. The same waves would have swept over - European land and seas, and there found coadjutors for new - strife in earthquake waves of European origin. These times - of catastrophe may have continued in America through half - of the following Triassic period; for fully two thirds of - the Triassic period are unrepresented by rocks and fossils - on the Atlantic border." - -Coming now to the Post-Mesozoic revolution this period was marked by -the making of the greatest of the North American mountain systems. - -Dana points out that this revolution affected the summit region of the -Rocky Mountains over a broad belt probably as long as the western side -of the continent. - -This great belt of mountain-making extended from the Arctic regions -through North America, probably paralleled by like work, of equal -extent, in South America, but on a more eastern line. - -"The disappearance of species," says Dana, "at the close of Mesozoic -time was one of the two most noted in all geological history. Probably -not a tenth part of the animal species of the world disappeared -at the time, and far less of the vegetable life and terrestrial -Invertebrates; yet the change was so comprehensive that no Cretaceous -species of Vertebrate is yet known to occur in the rocks of the -American Tertiary, and not even a marine Invertebrate." - -In tracing the causes of these disappearances, Dana points out that, -perhaps, the principal cause was a decrease in the temperature of the -ocean, since the destructions were limited in large measure to marine -life. He regards, however, the other most probable cause as traceable -to earthquake waves; for the making of a great mountain range along -the entire length of the continent resulted in displacements of -the rock formations along lines hundreds of miles in length. Such -displacements must have been attended by a succession of earthquakes -of unusual violence, causing the destruction by sudden shocks beneath, -and resulting, directly and indirectly, in waves sweeping over the -continent. Since at this time the land was still low for the greater -part, the huge waves must have repeatedly swept over the greater part -of the land, leaving only the smaller species of animals and the -vegetation. - -It is evident, therefore, that during the geological past earthquakes -occurred that were probably vastly greater than any that have occurred -on the earth during more recent times. - - - - -CHAPTER XXXVI - -THE KIMBERLY DIAMOND FIELDS AND THEIR VOLCANIC ORIGIN - - -The elementary substance carbon occurs in three forms, i. e., -_charcoal_, _graphite_, and the _diamond_. The commonest form of -carbon is to be found in charcoal, as well as in bituminous coal, -anthracite coal, and _lignite_. Graphite, also known as _plumbago_, -or _black lead_, is the substance you have seen so often in the lead -of pencils. The diamond, as every one knows, is the highly prized -precious stone that sparkles so brightly in the light, and is so hard -that it is capable of scratching almost any other substance. - -Diamonds are found in various parts of the world. We are now -interested in them, however, only as they occur in certain parts of -the world, as in the great Kimberly diamond fields in Southern Africa. - -Dr. Max Bauer in his book on precious stones says that the discovery -of diamonds in South Africa was made by a traveller named O'Reilly, -who, in 1867, saw a child sitting in the house of a Boer named Jacobs, -playing with a shining stone. Jacob's farm was a short distance south -of the Orange River near Hopetown. This stone proved to be a diamond -weighing some twenty-one and three-tenths carats and was afterwards -sold for $2,500. The incident led to the discovery and consequent -development of the Kimberly diamond fields. - -Without going into a description of the different deposits in which -diamonds are found, it will suffice to say that in the Kimberly -district the diamonds occur distributed through the materials that -fill peculiar funnel-shaped depressions called _pipes_ which extend -vertically downward to unknown depths. The rock that fills a pipe -consists of an entirely different material from that in which the pipe -occurs. The upper extremity of the pipe is generally slightly elevated -above the general surface for a few yards. The pipes vary in diameter -from twenty to 750 yards, diameters of from 200 to 300 yards being -quiet common. - -In 1892, the diamond-bearing material found in the pipes of the -Kimberly mines had been excavated vertically downwards a distance of -1,261 feet, without any signs of its being exhausted. - -Now, the materials which fill the pipe of the great Kimberly mine are -practically the same in all the mines in the neighborhood. At the -upper part of the pipe the materials show the action of weathering by -exposure to the air. Here the ground is of a yellowish color. Below, -the materials have a blue color. - -According to Bauer the diamond-bearing material that fills the upper -part of the pipe consists of a soft, sandy material of a light yellow -color, known to diamond miners as _yellow ground_, or _yellow stuff_. - -In the case of the Kimberly mine, the yellow ground has a thickness of -about sixty feet. Below it the material has a blue color and is known -as the _blue ground_. This latter material possesses the character -of a volcanic _tuff_, which is a hardened clay. It is of a green or -bluish green color and has the appearance of dried mud that holds -or binds together numerous irregular, tough, and sometimes rounded -fragments of a green or bluish black serpentine. - -The diamonds are found near the surface in the yellow ground, as -well as downwards through the blue ground. It was at one time thought -that most of the diamonds existed in the yellow ground, and that they -would soon disappear entirely at short distances below where the blue -ground began. Under this belief some of the most valuable claims -changed hands at prices far below their true value. It was soon found, -however, that large and valuable stones existed in the blue ground, -and, indeed, this ground has never been mined to a depth below where -valuable diamonds appear. - -The diamonds occur in very small quantities spread through the yellow -and blue grounds. The following statement by Bauer will show this: - - "A striking illustration of their sparing occurrence is - furnished by the fact that in the richest part of the - richest mine, namely, in the Kimberly mine, they constitute - only one part in 2,000,000, or 0.00005% of the blue ground. - In other mines the proportion is still lower, namely, one - part in 40,000,000, a yield which corresponds to five - carats per cubic yard of rock." - -Of course, you will desire by this time to know the manner in which -the pipes of the diamond mines of South Africa have become filled with -the diamond-bearing rocks, and particularly what diamonds have to do -with a book on volcanoes and earthquakes. - -Dr. Emil Cohen, who has made a study of these regions, regards the -pipes as volcanic vents or chimneys, and that the materials filling -the pipes have been brought up from below by volcanic forces. He says: - - "I consider that the diamantiferous ground is a product - of volcanic action, and was probably erupted at a - comparatively low temperature in the form of an ash - saturated with water and comparable to the materials - ejected by a mud volcano. Subsequently new minerals were - formed in the mass, consequent on alterations induced in - the upper part by exposure to atmospheric agencies, and in - the lower by the presence of water. Each of the crater-like - basins, or, perhaps, more correctly, funnels, in which - alone diamonds are now found, was at one time the outlet - of an active volcano which became filled up, partly with - the products of eruption and partly with ejected material - which fell back from the sides of the crater intermingled - with various foreign substances, such as small pebbles, - or organic remains of local origin, all of which became - imbedded in the volcanic tuff. The substance of the tuff - was probably mainly derived from deep-seated crystalline - rocks, of which isolated remains are now to be found, - and which are similar to those which now crop out at the - surface, only at a considerable distance from the diamond - fields. These crystalline rocks from which the diamonds - probably took their origin, were pulverized and forced - up into the pipes by the action of volcanic forces, and - imbedded in this eruptive material, these diamonds either - in perfect crystals or in fragments are now found." - -So far as the volcanic origin of the diamonds of the Kimberly diamond -fields is concerned, Cohen's theory has been generally accepted with -the following modifications: that the pipes were not filled by a -single volcanic eruption, but by successive eruptions, and that in -the case of the Kimberly mine, the pipes contain the results of as -many as fifteen successive eruptions. There has, however, been another -and more important modification proposed to Cohen's theory, which is -far more probable. It will be noticed that Cohen's theory regards the -action of the volcanic eruption as only serving to bring fragments -of a deep-seated mother rock that contained the diamonds up from -below with the material that fills the pipe. Now, Prof. Carvill Lewis -proposes the following very important change in Cohen's theory: that -the blue ground does not consist of fragmentary material or tuff, but -was forced up from below in the pipe in a molten mass and consolidated -on cooling. In other words, the blue ground is filled with an ordinary -igneous rock that was solidified in place in the vent or pipe. - -In the great Kimberly mines the surface of the pipe is divided into -numerous separate claims, each consisting of a small square lot. There -are so many of these claims in the Kimberly mine that its surface is -honey-combed by numerous square pits. The work is done largely by -native Kaffirs employed there since the '70's. As the material was -removed from the pit, the adjoining claims were separated from each -other by high vertical walls. - -At a later date, in order to remove the material and separate the -lots, high staging provided with ropes and hauling machinery was -erected. The number of these ropes is now so great that the mine has -the appearance of a huge cobweb. - -A very extensive series of investigations has been made at a -comparatively recent date by Prof. Henri Moissan of France on various -chemical products that are obtained under the influence of the high -temperatures of the electric furnace. When a powerful electric current -is caused to pass through a highly refractory material, that is to -say, a material difficult to fuse, such as carbon, it raises it to an -extremely high temperature. A still higher temperature can be obtained -by causing a powerful current to flow between two carbon rods that -are first brought into contact, and then gradually separated from -each other, just as they are in the ordinary arc lights employed for -lighting the streets of our cities. In the latter way a temperature -that is estimated as high as 3,500 deg. C. (6,332 deg. F.), can be readily -obtained. Under these very high temperatures some very curious -chemical products have been obtained in electric furnaces. These -furnaces consist of small chambers made of highly refractory materials -closely surrounding the incandescent carbon, or the carbon voltaic -arc. Among some of the most curious of these products are artificially -produced diamonds. - -Moissan, however, was not the first to produce diamonds artificially. -As soon as Lavoisier had experimentally shown that the chemical -composition of the diamond and carbon are the same, efforts were made -to convert charcoal into diamonds, and Despretz, as early as 1849, -by means of the combined influence of a powerful burning glass, the -oxyhydrogen blowpipe, and the carbon voltaic arc obtained a very high -temperature. He claims by this temperature to have been able to change -carbon into a few microscopic diamonds. It is quite possible, in the -light of later investigations, that Despretz may have been mistaken -in his belief that he had actually produced diamonds; but whether -this be so or not, he was certainly one of the pioneers in this early -transformation of charcoal. - -Theoretically, all that would be required in order to change the -non-crystalline form of carbon into the diamond, would be to -subject the carbon to a temperature sufficiently high to fuse it -and then permit it slowly to crystallize. Could this be done, there -should be no trouble in transforming any amount of coal into any -equal amount of diamonds. But the transformation is by no means as -simple as might be supposed. It is not that the temperature of the -carbon cannot be raised to its point of fusion, but that as soon -as a certain temperature has been reached, the carbon, instead of -fusing or melting, is suddenly volatilized or turned into vapor. -There is no doubt that this is done. Thousands of feet of carbon -rods are volatilized every night in the arc lamps of our cities, -but the trouble is that this carbon vapor so formed, when cooled, -or condensed, is not converted into the exceedingly hard, clear, -crystalline diamond, but into the soft, dull black graphite or -plumbago. - -Now the process adopted by Moissan in order to cause volatilized -carbon, or carbon vapor, to condense in the form of crystalline -diamonds was practically as follows: he placed pieces of pure carbon -inside a very strong steel tube, such, for example, as would be formed -by boring a short cylindrical hole in a piece of strong thick steel, -and placing a small quantity of carbon inside the tube so formed. -Closing the open end of the tube by means of a tightly fitting screw -plug, he volatilized the carbon inside the tube. The steel, tube, and -plug formed an electric furnace, for, as soon as he passed an electric -current through it, the temperature at once became high enough to -volatilize the carbon. - -Under these circumstances the carbon vapor was subjected to great -pressure owing to the limited space in which it was liberated. As soon -as this mass of dense vapor had been formed, he seized the steel tube -with a pair of furnace tongs, and plunged it below the surface of cold -water in a bucket. - -Of course, as the hot tube suddenly chilled, there was a great -shrinking in the walls of the furnace, so that the already compressed -carbon vapor was subjected to a still greater pressure which possibly -liquified it. Of that, however, we cannot speak definitely. This, -however, can safely be asserted, that when the tube was broken open -a confused mass of small crystals was found inside, some of which, -on examination with the microscope, were found to consist of small -crystals of two forms of diamonds, namely, the black diamond, or -carbonado, and the regular crystallized diamond. - -Moissan made a great number of experiments for producing diamonds -in this way, and succeeded in forming some very beautiful, though -microscopic, diamonds. - -What may be said to characterize especially Moissan's experiments was -the comparatively great number of diamonds, so small as to be scarcely -distinguishable under the microscope. The high temperature to which -the materials inside the tube were exposed resulted in the production -of numerous minute crystals of different minerals. In order to get rid -of as many of these as possible Moissan adopted the plan of subjecting -the material to the action of powerful solvents, such as sulphuric -acid, aqua regia, or a mixture of sulphuric and nitric acid, and -hydrofluoric acid. These acids destroyed most of the minute crystals -of other minerals, but left the minute crystals of diamonds unaffected. - -Now it will be observed that the theory proposed by Prof. Carvill -Lewis as to the probable origin of the diamonds of the Kimberly mines -bears a wonderfully close resemblance to the method adopted by Moissan -for the production of artificial diamonds, since it supposes the -diamonds to have been formed by the sudden cooling or chilling within -the pipe of various molten materials brought up from great depths by -the volcanic forces. If this be true, then besides the comparatively -large crystallized and perfect diamonds found in the blue ground -of the Kimberly mines, there should also be found large quantities -of microscopic diamonds, just as are found in Moissan's electric -furnaces, in which he produced artificial diamonds. - -Moissan, considering this, obtained a specimen of the blue ground -from the Kimberly diamond pipe and on subjecting it to the action of -the different solvents before named, found in the mass that was left -undissolved a great number of microscopic diamonds. It would seem, -therefore, that there is no reasonable doubt but that the Kimberly -diamond fields had their diamonds produced by the sudden chilling in -the volcanic pipes of molten materials brought from great depths by -the force of volcanic eruption. - - - - -CHAPTER XXXVII - -THE FABLED CONTINENT OF ATLANTIS - - -Besides the sudden changes of level that frequently occur during -earthquake shocks there are gradual changes of level that take place -very slowly throughout long periods of time. - -These are believed to be due to the warpings produced by the cooling -of an originally highly heated globe. - -It is not true, therefore, that the earth's surface is fixed, or that -its land and water areas remain always the same. On the contrary, what -is land at one time is water at another time, and so, too, water areas -may become changed into land areas. - -For the most part these changes go on so slowly as not to be -noticeable in an ordinary lifetime. Indeed, in some cases, they are so -extremely gradual that Methuselah himself might have gone to his grave -in ignorance of their progress. - -Let us briefly note a few well-known gradual changes of level. - -One of the most extensive of these is the sinking of an immense area, -over 6,000 miles in diameter, that covers a large part of the bed or -floor of the Pacific Ocean. - -It is an easy matter to observe the gradual changes of level on the -coasts, since the old water line can be at once found, but it is very -difficult to detect such changes in the bed of the ocean, hidden as -it is by a covering of water. Yet many things that seem impossible to -the uninitiated are readily solved by those familiar with physical -science. Little signs, meaningless to others, are easily read, and -these prove beyond doubt the gradual sinking of the ocean's bed. - -It was once believed that the coral polyps or animalculae from the -hard, bony skeletons of which coral reefs are formed, could live -at the greatest depths of the ocean. These minute animals were, -therefore, generally credited with filling up the deep ocean, -in certain places, and converting it into dry land, and poetic -philosophers were pleased to point to their indefatigable labors as an -object lesson to the slothful. - -But these charming, though fallacious, ideas were rudely overthrown by -the sounding line and the drag-net. It had long been known that pieces -of coral rock were brought up by dredging apparatus from the bottom of -the ocean at all depths, but it was eventually shown that such pieces -of coral rock never contained living animalculae, when brought from -water at greater depths than from 100 to 120 feet. - -It puzzled scientific men no little at first to explain this apparent -inconsistency. If the coral polyp could not live in water at greater -depths than from 100 to 120 feet, how could the presence of coral rock -at a depth of thousands of feet be explained? Happily, however, this -problem was solved by the great naturalist, Charles Darwin, who showed -that coral islands can only be formed in parts of the ocean whose beds -are sinking at the same gradual rate at which the coral rock is being -deposited. The presence, therefore, of coral islands on the bed of the -Pacific, as well as along parts of its coasts, are, to scientific men, -as good indications of its gradual sinking as if such facts had been -written in the clearest language. - -But there are other instances of gradual changes of level besides -the bed of the Pacific. About 600 miles along the coast of Greenland, -from Disco Bay, near lat. 69 deg. N., south to the Firth of Igaliko, lat. -60 deg. 43' N., the bed of the ocean has been slowly sinking through 400 -years. Old buildings and islands have been covered by the waters, so -that fishermen have been compelled to provide new poles for their -boats. As Sir Charles Lyell remarks: - - "In one place the Moravian settlers have been obliged more - than once to move inland the poles upon which their large - boats are set, and the old poles still remain beneath the - water as silent witnesses of the change." - -Besides these gradual changes of level there are many others, but -only one more need be cited: the gradual movements of the coasts of -North America between Labrador and New Jersey that are rising in some -places, and sinking in other places. - -The evidences of these gradual changes of level are sometimes of -such a character that he who runs may read them. One of the most -interesting is, perhaps, that of the old Roman temple of Jupiter -Serapis, at Pozzuli, on the borders of the Mediterranean. This temple, -when completed, was 124 feet in length and 115 feet in width. Its roof -was supported by forty-six columns, each forty-two feet in height, and -five feet in diameter. Only three of these columns are now standing. -They give, however, unquestionable evidence of having been submerged -for about half their height. Nor, indeed, is the evidence wanting that -this submergence continued a considerable time; for, while the lower -twelve feet of the columns remain smooth and unaffected, yet, for a -distance of nine feet above this portion, they have been perforated -by various stone-boring mollusks of a species still living in the -Mediterranean. This witnesses that the columns, when submerged, were -buried in mud for twelve feet, and surrounded by water nine feet -deep. According to Dana, the pavement of the temple is still under -water. The fact that another pavement exists below it shows that these -changes of level had occurred before the temple was deserted by the -Romans. It appears, that, prior to 1845, a gradual sinking of this -part of the coast had been going on, but that since then there has -ensued a gradual rising. - -The evidences of these gradual changes of level in the land and water -surfaces of the earth cannot be doubted by even the most skeptical. -Again and again has the dry land disappeared below the surface of the -waters of the ocean. Again and again, the ocean's bed has been raised -to the surface and been converted into dry land. Suppose we attempt to -follow one of the latter movements. - -We will imagine an extensive area to have slowly appeared above the -ocean. In due process of time this land surface, which we will assume -to have continental dimensions, gradually becomes covered with plant -and animal life. If it remains above the water for a sufficient -length of time, its simple plants and animals acquire more and more -complex forms, so as to make it difficult to detect any traces of the -original species from which they have descended, or, more correctly, -ascended. Moreover, where favorable conditions exist, the continent -becomes peopled with men, who gradually advance from barbarism to -semi-barbarism and eventually become a most highly civilized nation, -sending to different parts of the world colonies, who carry with them -the language and religious customs of the land of their birth. - -But, a sudden or paroxysmal change of level occurs. The highly -developed and densely populated region is suddenly swept out of -existence and completely covered by the waters of the ocean until, in -a few thousand years, all traces of its existence have so completely -disappeared that but few, if any, can be found willing to acknowledge -it ever had an existence. - -Such, it is claimed, was the fate of the fabled Continent of Atlantis. -It will, therefore, be interesting to endeavor briefly to review its -past history and to read some of the things that have been written -about this part of the world, which appears in the opinion of some of -the ancients to have actually existed. - -References to Atlantis have been made by various early writers. Solon, -the great Athenian lawgiver, who flourished 600 years B. C., -began a description of this place in verse. This description was never -completed. At a later date one of Solon's descendants, Plato, who -lived about 400 B. C., prepared a description of Atlantis, -giving in detail its location, the general character of its surface, -a description of its principal city, and the civilization of its -inhabitants, as well as a brief reference to its sudden destruction. -In another place this record of Plato will be given in full. It will -suffice now to quote briefly what he says concerning its location. - - "There was an island situated in front of the straits which - you call the Columns of Heracles (Straits of Gibraltar). - The island was larger than Libya and Asia put together, - and was the way to other islands, and from the island you - might pass through the whole in the opposite continent, - for this sea which is within the Straits of Heracles is - only a harbor, having a narrow entrance, but that other is - the real sea, and the surrounding land may most truly be - called a continent. Now, in the island of Atlantis, there - was a great and wonderful empire, which had ruled over the - whole island and several others, as well as over part of - the continents; and, besides these, they subjected the - parts of Libya within the Columns of Heracles as far as - Egypt, and of Europe as far as Tyrrhenia. The vast power, - thus gathered into one, endeavored to subdue at one blow - our country and yours, and the whole of the land which was - within the straits, and then, Solon, your country shone - forth, in the excellence of her virtues and strength, among - all mankind, for she was the first in courage and military - skill, and was the leader of the Hellenes. And when the - rest fell off from her, being compelled to stand alone, - after having undergone the very extremity of danger, she - defeated and triumphed over the invaders, and preserved - from slavery those who were not yet subjected, and freely - liberated all the others who dwelt within the limits of - Heracles. - - "But afterwards, there occurred violent earthquakes and - floods, and in a single day and night of rain, all your - warlike men in a body sunk into the earth, and the island - of Atlantis in a like manner disappeared, and was sunk - beneath the sea. And that is the reason why the sea in - those parts is impassable and impenetrable, because there - is such a quantity of shallow mud in the way; and this - was caused by the subsidence of the island." ("Plato's - Dialogues," ii, 517, Timaeus). - -But besides Solon and Plato there are other ancient writers who refer -to the lost island of Atlantis. - -AElian, in his "Varia Historia," lib. iii, chap. xvii, states that -Theopompos, who flourished 400 B. C., refers to an interview -between Midas, King of Phrygia, and Sielus, in which the latter speaks -of a great continent larger than Asia, Europe, and Libya together that -existed in the Atlantic. - -Proclus quotes a statement from an ancient writer, who speaks about -the islands of the sea beyond the Pillars of Hercules (Straits of -Gibraltar). - -Marcellus, in a book on the Ethiopians, refers to seven islands in -the Atlantic whose inhabitants preserve legends of a greater island -(possibly Atlantis), that had dominion over the small islands. - -Diodorus Siculus asserts that the Phoenicians discovered a large -island in the Atlantic beyond the Pillars of Hercules several days' -sail from the coast of Africa. - -Homer, Plutarch, and other ancient writers, refer to several islands -in the Atlantic situated several thousand stadia from the Pillars of -Hercules. (A stadium was a Greek measure of length equal to 600 feet. -It was equal to one-eighth of a Roman mile, or 625 Roman feet.) - -Ignatius Donnelly, in his book, called "Atlantis, the Ante-Diluvian -World," claims that Plato's description of Atlantis which has -generally been regarded as imaginary, was, on the contrary, historic; -that the prehistoric continent of Atlantis was the cradle of the human -race; that here man reached his highest civilization; that Atlantis -was the site of the Garden of Eden, the Gardens of the Hesperides, the -Elysian Fields, as well as Olympus; that, under the forms of the gods -and goddesses of the ancient Greeks, the Phoenicians, the Hindoos, -and the Scandinavians, are related the stories of the kings, queens, -and heroes of Atlantis. - -Much that has been claimed for the lost continent can hardly be -regarded in any other light save that of imagination. For example, it -has been asserted that it was from Atlantis that the colonies were -sent out that peopled the coast countries of the Gulf of Mexico, of -parts of the valley of the Mississippi, the basin of the Amazon, the -western coasts of South America, parts of Europe, the shore lands of -the Mediterranean Sea, the coasts of Europe, including the Caspian and -the Black Seas, and even of parts of Africa. - -It has also been asserted that this mighty nation of Atlantis carried -the worship of the sun to Egypt, which was one of its first colonies, -and, therefore, the civilization of Egypt was but an offshoot of -prehistoric Atlantis. - -But it will be reasonably objected that, if such a mass of land ever -existed in the North Atlantic, some evidences should still be found -on the bed of the ocean. Even though great periods of time have -elapsed since the disappearance of Atlantis, some traces of its former -existence should still remain on the floor of the ocean. Are there -any evidences of an old land mass on this part of the floor of the -Atlantic? The answer is unmistakable. - -Deep-sea soundings show beyond question that there still exists in -the North Atlantic in the region where Atlantis is said to have been -located a submarine island, the summits of which appear above the -waters in the Azores and the Canary Islands. This submarine island -has been traced southwest over the bed of the ocean for a distance of -several thousand miles with a breadth of fully 1,000 miles. Toward the -south there is connected with it another submarine island, the summits -of which reach above the surface in the islands of Ascension, St. -Helena, and Tristan d'Acunha. - -But the testimony of the submarine islands extends further than this. -According to a number of careful soundings it appears that the bed -of these parts of the ocean, instead of being characterized by a -comparatively level surface due to the gradual accumulation of silt, -possesses, to a great extent, the peculiarly sculptured surfaces which -are only produced by exposure for a long time to the atmosphere. - -Other facts might be adduced to show that some time during the first -appearance of man on the earth there was a large land mass connecting -the Eastern and Western Continents. These facts include the wonderful -resemblances existing between the plants and animals of the Eastern -and Western Continents, the close resemblances of the myths and -legends of the races of the Eastern and Western Continents, as well -as the identity of their religious ideas, and the close similarity of -their language so far as relates to certain fundamental ideas. These -facts all point unquestionably to the existence of some large land -mass between the two continents, and to this extent to throw light on -the probable existence of prehistoric Atlantis. - - - - -CHAPTER XXXVIII - -PLATO'S ACCOUNT OF ATLANTIS - - -The following is a translation of Plato's record in full: - - Critias. Then listen, Socrates, to a strange tale, which - is, however, certainly true, as Solon, who was the wisest - of the seven sages, declared. He was a relative and great - friend of my great-grandfather, Dropidas, as he himself - says in several of his poems, and Dropidas told Critias, my - grandfather, who remembered, and told us, that there were - of old great and marvellous actions of the Athenians, which - have passed into oblivion through time and the destruction - of the human race--and one in particular, which was the - greatest of them all, the recital of which will be a - suitable testimony of our gratitude to you.... - - Socrates. Very good; and what is this ancient famous - action of which Critias spoke, not as a mere legend, but - as a veritable action of the Athenian State, which Solon - recounted? - - Critias. I will tell an old-world story which I heard from - an aged man; for Critias was, as he said, at that time - nearly ninety-years of age, and I was about ten years of - age. Now the day was that day of the Apaturia which is - called the registration of youth; at which, according to - custom, our parents gave prizes for recitations, and the - poems of several poets were recited by us boys, and many - of us sung the poems of Solon, which were new at the time. - One of our tribe, either because this was his real opinion, - or because he thought that he would please Critias, said - that, in his judgment, Solon was not only the wisest of men - but the noblest of poets. The old man, I well remember, - brightened up at this, and said smiling: "Yes, Amynander, - if Solon had only, like other poets, made poetry the - business of his life, and had completed the tale which he - brought with him from Egypt, and had not been compelled, by - reason of the factions and troubles which he found stirring - in this country when he came home, to attend to other - matters, in my opinion, he would have been as famous as - Homer, or Hesiod, or any poet." - - "And what was that poem about, Critias?" said the person - who addressed him. - - "About the greatest action which the Athenians ever did, - and which ought to have been most famous, but which, - through the lapse of time and the destruction of the - actors, has not come down to us." - - "Tell us," said the other, "the whole story, and how and - from whom Solon heard this veritable tradition." - - He replied: "At the head of the Egyptian Delta, where the - river Nile divides, there is a certain district which is - called the district of Sais, and the great city of the - district is also called Sais, and is the city from which - Amasis the king was sprung. And the citizens have a deity - who is their foundress: she is called in the Egyptian - tongue Neith, which is asserted by them to be the same - whom the Hellenes called Athene. Now, the citizens of - this city are great lovers of the Athenians, and say that - they are in some way related to them. Thither came Solon, - who was received by them with great honor; and he asked - the priests, who were most skilful in such matters, about - antiquity, and made the discovery that neither he nor any - other Hellene knew anything worth mentioning about the - times of old. - - "On one occasion, when he was drawing them on to speak of - antiquity, he began to tell about the most ancient things - in our part of the world--about Phoroneus, who is called - 'the first,' and about Niobe; and, after the Deluge, to - tell of the lives of Deucalian and Pyrrha; and he traced - the genealogy of their descendants, and attempted to - reckon how many years old were the events of which he was - speaking, and to give the dates. Thereupon, one of the - priests, who was of very great age, said: 'O Solon, Solon, - you Hellenes are but children, and there is never an old - man who is an Hellene.' Solon, hearing this, said, 'What do - you mean?' 'I mean to say,' he replied, 'that in mind you - are all young; there is no old opinion handed down among - you by ancient traditions, nor any science which is hoary - with age. And I will tell you the reason of this: there - have been, and there will be again, many destructions of - mankind arising out of many causes. - - "'There is a story which even you have preserved, that - once upon a time Phaethon, the son of Helios, having yoked - the steeds in his father's chariot, because he was not - able to drive them in the path of his father, burnt up all - that was upon the earth, and was himself destroyed by a - thunder-bolt. Now, this has the form of a myth, but really - signifies a declination of the bodies moving around the - earth, and in the heavens, and a great conflagration of - things upon the earth recurring at long intervals of time: - when this happens, those who live upon the mountains and in - dry and lofty places are more liable to destruction than - those who dwell by rivers or on the sea-shore; and from - this calamity the Nile, who is our never-failing savior, - saves and delivers us. - - "'When, on the other hand, the gods purge the earth with a - deluge of water, among you herdsmen and shepherds on the - mountains are the survivors, whereas those of you who live - in cities are carried by the rivers into the sea; but in - this country neither at that time nor at any other does - the water come up from below, for which reason the things - preserved here are said to be the oldest. The fact is, - that wherever the extremity of winter frost or of summer - sun does not prevent, the human race is always increasing - at times, and at other times diminishing in numbers. And - whatever happened either in your country or in ours, or in - any other regions of which we are informed--if any action - which is noble or great, or in any other way remarkable has - taken place, all that has been written down of old, and is - preserved in our temples; whereas you and other nations are - just being provided with letters and the other things which - States require; and then, at the usual period, the stream - from heaven descends like a pestilence, and leaves only - those of you who are destitute of letters and education; - and thus you have to begin all over again as children, and - know nothing of what happened in ancient times, either - among us or among yourselves. - - "'As for those genealogies of yours which you have - recounted to us, Solon, they are no better than the tales - of children; for, in the first place, you remember one - deluge only, whereas there were many of them, and, in the - next place, you do not know that there dwelt in your land - the fairest and noblest race of men which ever lived, of - whom you and your whole city are but a seed or remnant. And - this was unknown to you, because for many generations the - survivors of that destruction died and made no sign. For - there was a time, Solon, before that great deluge of all, - when the city which now is Athens, was first in war, and - was preeminent for the excellence of her laws, and is said - to have performed the noblest deeds, and to have had the - fairest constitution of any of which tradition tells, under - the face of heaven.' - - "Solon marvelled at this and earnestly requested the priest - to inform him exactly and in order about these former - citizens. 'You are welcome to hear about them, Solon,' said - the priest, 'both for your own sake and for that of the - city; and, above all, for the sake of the goddess who is - the common patron and protector and educator of both our - cities. She founded your city a thousand years before ours, - receiving from the Earth and Hephaestus the seed of your - race, and then she founded ours, the constitution of which - is set down in our sacred registers as 8,000 years old. As - touching the citizens of 9,000 years ago, I will briefly - inform you of their laws and of the noblest of their - actions; and the exact particulars of the whole we will - hereafter go through at our leisure in the sacred registers - themselves. If you compare these very laws with your own, - you will find that many of ours are the counterpart of - yours, as they were in the olden time. - - "'In the first place, there is the caste of priests, - which is separated from all the others; next there are - the artificers, who exercise their several crafts by - themselves, and without admixture of any other, and also - there is the class of shepherds and that of hunters, as - well as that of husbandmen; and you will observe, too, that - the warriors in Egypt are separated from all the other - classes, and are commanded by the law only to engage in - war. Moreover, the weapons with which they are equipped - are shields and spears, and this the goddess taught first - among you, and then in Asiatic countries, and we among the - Asiatics first adopted. - - "'Then, as to wisdom, do you observe, what care the law - took from the very first, searching out and comprehending - the whole order of things down to prophecy and medicine - (the latter with a view to health); and out of these divine - elements drawing what was needful for human life, and - adding every sort of knowledge which was connected with - them. All this order and arrangement the goddess first - imparted to you when establishing your city; and she chose - the spot of earth in which you were born, because she saw - that the happy temperament of the seasons in that land - would produce the wisest of men. - - "'Wherefore the goddess, who was a lover both of war and - of wisdom, selected, and first of all settled that spot - which was the most likely to produce men likest herself. - And there you dwelt, having such laws as these and still - better ones, and excelled all mankind in all virtue, - as became the children and disciples of the gods. Many - great and wonderful deeds are recorded of your State in - our histories; but one of them exceeds all the rest in - greatness and valor; for these histories tell of a mighty - power which was agressing wantonly against the whole of - Europe and Asia, and to which your city put an end. - - "'This power came forth out of the Atlantic Ocean, for in - those days the Atlantic was navigable; and there was an - island situated in front of the straits which you call the - Columns of Heracles: the island was larger than Libya and - Asia put together, and was the way to other islands, and - from the island you might pass through the whole of the - opposite continent which surrounded the true ocean; for - this sea which is within the Straits of Heracles is only - a harbor, having a narrow entrance, but that other is a - real sea, and the surrounding land may be most truly called - a continent. Now, in the island of Atlantis there was a - great and wonderful empire, which had rule over the whole - island and several others, as well as over parts of the - continent; and, besides these, they subjected the parts of - Libya within the Columns of Heracles as far as Egypt, and - of Europe as far as Tyrrhenia. - - "'That vast power, thus gathered into one, endeavored to - subdue at one blow our country and yours, and the whole of - the land which was within the straits; and then, Solon, - your country shone forth, in the excellence of her virtue - and strength, among all mankind, for she was the first - in courage and military skill, and was the leader of the - Hellenes. And when the rest fell off from her, being - compelled to stand alone, after having undergone the very - extremity of danger, she defeated and triumphed over the - invaders, and preserved from slavery those who were not - yet subjected, and freely liberated all the others who - dwelt within the limits of Heracles. But afterward there - occurred violent earthquakes and floods, and in a single - day and night of rain all your warlike men in a body sunk - into the earth, and the island of Atlantis in like manner - disappeared, and was sunk beneath the sea. And that is - the reason why the sea in those parts is impassable and - impenetrable, because there is such a quantity of shallow - mud in the way; and this was caused by the subsidence of - the island.' ('Plato's Dialogues,' ii, 517, Timaeus.)... - - "But in addition to the gods whom you have mentioned, I - would specially invoke Mnemosyne; for all the important - part of what I have to tell is dependent on her favor, and - if I can recollect and recite enough of what was said by - the priests, and brought hither by Solon, I doubt not that - I shall satisfy the requirements of this theatre. To that - task, then, I will at once address myself. - - "Let me begin by observing first of all that nine thousand - was the sum of years which had elapsed since the war which - was said to have taken place between all those who dwelt - outside the Pillars of Heracles and those who dwelt within - them. This war I am now to describe. Of the combatants on - the one side the city of Athens was reported to have been - the ruler, and to have directed the contest; the combatants - on the other side were led by the kings of the islands - of Atlantis, which, as I was saying, once had an extent - greater than that of Libya and Asia; and, when afterwards - sunk by an earthquake, became an impassable barrier of mud - to voyagers sailing from hence to the ocean. The progress - of the history will unfold the various tribes of barbarians - and Hellenes which then existed, as they successively - appear on the scene; but I must begin by describing, first - of all, the Athenians as they were in that day, and their - enemies who fought with them; and I shall have to tell of - the power and form of government of both of them. Let us - give the precedence to Athens.... - - "Many great deluges have taken place during the nine - thousand years, for that is the number of years which have - elapsed since the time of which I am speaking; and in all - the ages and changes of things there has never been any - settlement of the earth flowing down from the mountains, as - in other places, which is worth speaking of; it has always - been carried round in a circle, and disappeared in the - depths below. The consequence is that, in comparison with - what then was, there are remaining in small islets only the - bones of the wasted body, as they may be called, all the - richer and softer parts of the soil having fallen away, and - the mere skeleton of the country being left.... - - "And next, if I have not forgotten what I heard when I was - a child, I will impart to you the character and origin - of their adversaries; for friends should not keep their - stories to themselves, but have them in common. Yet, before - proceeding further in the narrative, I ought to warn you - that you must not be surprised, if you should hear Hellenic - names given to foreigners. I will tell you the reason - of this: Solon, who was intending to use the tale for - his poem, made an investigation into the meaning of the - names, and found that the early Egyptians, in writing them - down, had translated them into their own language, and he - recovered the meaning of the several names and retranslated - them, and copied them out again in our language. My - great-grandfather, Dropidas, had the original writing, - which is still in my possession, and was carefully studied - by me when I was a child. Therefore, if you hear names such - as are used in this country, you must not be surprised, for - I have told you the reason of them. - - "The tale, which was of great length, began as follows: - I have before remarked, in speaking of the allotments - of the gods, that they distributed the whole earth into - portions differing in extent, and made themselves temples - and sacrifices. And Poseidon, receiving for his lot the - island of Atlantis, begat children by a mortal woman, and - settled them in a part of the island which I will proceed - to describe. On the side toward the sea, and in the centre - of the whole island, there was a plain which is said to - have been the fairest of all plains, and very fertile. - Near the plain, and also in the centre of the island, at a - distance of about fifty stadia, there was a mountain, not - very high on any side. In this mountain there dwelt one of - the earth-born primeval men of that country, whose name was - Evenor, and he had a wife named Leucippe, and they had an - only daughter, who was named Cleito. - - "The maiden was growing up to womanhood when her father - and mother died; Poseidon fell in love with her, and had - intercourse with her; and, breaking the ground, enclosed - the hill in which she lived all around, making alternate - zones of sea and land, larger and smaller, encircling - one another; there were two of land and three of water, - which he turned as with a lathe out of the centre of the - island, equidistant every way, so that no man could get - to the island, for ships and voyagers were not yet heard - of. He himself, as he was a god, found no difficulty in - making special arrangements for the centre island, bringing - two streams of water under the earth, which he caused to - ascend as springs, one of warm water and the other of cold, - and making every variety of food to spring up abundantly - in the earth. He also begat and brought up five pairs of - male children, dividing the island of Atlantis into ten - portions; he gave to the first-born of the eldest pair his - mother's dwelling and the surrounding allotment, which was - the largest and best, and made him king over the rest; the - others he made princes, and gave them rule over many men - and a large territory. - - "He named them all: the eldest, who was king, he named - Atlas, and from him the whole island and the ocean received - the name of Atlantic. To his twin brother, who was born - after him, and obtained as his lot the extremity of the - island toward the Pillars of Heracles, as far as the - country which is still called the region of Gades in that - part of the world, he gave the name which in the Hellenic - language is Eumelus, in the language of the country which - is named after him, Gadeirus. Of the second pair of twins, - he called one Ampheres and the other Evaemon. To the third - pair of twins he gave the name Mneseus to the elder, and - Autochthon to the one who followed him. Of the fourth pair - of twins he called the elder Elasippus and the younger - Mestor. And of the fifth pair he gave to the elder the name - of Azaes, and to the younger Diaprepes. - - "All these and their descendants were the inhabitants - and rulers of divers islands in the open sea; and also, - as has been already said, they held sway in the other - direction over the country within the Pillars as far as - Egypt and Tyrrhenia. Now Atlas had a numerous and honorable - family, and his eldest branch always retained the kingdom, - which the eldest son handed on to his eldest for many - generations; and they had such an amount of wealth as - was never before possessed by kings and potentates, and - is not likely ever to be again, and they were furnished - with everything which they could desire both in city and - country. For, because of the greatness of their empire, - many things were brought to them from foreign countries, - and the island itself provided much of what was required by - them for the uses of life. - - "In the first place, they dug out of the earth whatever - was to be found there, mineral as well as metal, and that - which is now only a name, and was then something more - than a name--orichalcum--was dug out of the earth in many - parts of the island, and, with the exception of gold, was - esteemed the most precious of metals among the men of those - days. There was an abundance of wood for carpenters' work, - and sufficient maintenance for tame and wild animals. - Moreover, there were a great number of elephants in the - island, and there was provision for animals of every kind, - both for those who live in lakes and marshes and rivers, - and also for those which live in mountains, and on plains, - and therefore for the animal which is the largest and most - voracious of them. - - "Also whatever fragrant things there are in the earth, - whether roots, or herbage, or woods, or distilling drops - of flowers, or fruits, grew and thrived in that land; and - again, the cultivated fruit of the earth, both the dry - edible fruit and other species of food, which we call by - the general name of legumes, and the fruits having a hard - rind, affording drinks, and meats, and ointments, and good - store of chestnuts and the like, which may be used to play - with, and are fruits which spoil with keeping--and the - pleasant kinds of dessert which console us after dinner, - when we are full and tired of eating--all these that - sacred island lying beneath the sun brought forth fair and - wondrous in infinite abundance. - - "All these things they received from the earth, and they - employed themselves in constructing their temples, and - palaces, and harbors and docks; and they arranged the - whole country in the following manner: first of all they - bridged over the zones of sea which surrounded the ancient - metropolis, and made a passage into and out of the royal - palace; and then they began to build the palace in the - habitation of the god and of their ancestors. This they - continued to ornament in successive generations, every king - surpassing the one who came before him to the utmost of his - power, until they made the building a marvel to behold for - size and for beauty. - - "And, beginning from the sea, they dug a canal three - hundred feet in width and one hundred feet in depth, and - fifty stadia in length, which they carried through to the - outermost zone, making a passage from the sea up to this, - which became a harbor, and leaving an opening sufficient - to enable the largest vessels to find ingress. Moreover, - they divided the zones of land which parted the zones - of sea, constructing bridges of such a width as would - leave a passage for a single trireme to pass out of one - into another, and roofed them over; and there was a way - underneath for the ships, for the banks of the zones were - raised considerably above the water. - - "Now the largest of the zones into which a passage was cut - from the sea was three stadia in breadth, and the zone of - land which came next of equal breadth; but the next two, - as well a zone of water as of land, were two stadia, and - the one which surrounded the central island was a stadium - only in width. The island in which the palace was situated - had a diameter of five stadia. This, and the zones and the - bridge, which was the sixth part of a stadium in width, - they surrounded by a stone wall, on either side placing - towers, and gates on the bridges where the sea passed - in. The stone which was used in the work they quarried - from underneath the centre island and from underneath the - zones, on the outer as well as the inner side. One kind of - stone was white, another black, and a third red; as they - quarried, they at the same time hollowed out decks, double - within, having roofs formed out of the native rock. - - "Some of their buildings were simple, but in others they - put together different stones, which they intermingled for - the sake of ornament, to be a natural source of delight. - The entire circuit of the wall which went around the - outermost one they covered with a coating of brass, and - the circuit of the next wall they coated with tin, and the - third, which encompassed the citadel, flashed with the red - light of orichalcum. The palace in the interior of the - citadel was constructed in this wise: in the centre was - a holy temple, dedicated to Cleito and Poseidon, which - remained inaccessible, and was surrounded by an enclosure - of gold; this was the spot in which was originally begotten - the race of ten princes, and thither they annually brought - the fruits of the earth in their season from all the ten - portions, and performed sacrifices to each of them. - - "Here, too, was Poseidon's own temple, of a stadium in - length and half a stadium in width, and of a proportionate - height, having a sort of barbaric splendor. All the outside - of the temple, with the exception of the pinnacles, they - covered with silver, and the pinnacles with gold. In the - interior of the temple the roof was of ivory, adorned - everywhere with gold and silver and orichalcum; all the - other parts of the walls and pillars and floor they lined - with orichalcum. In the temple they placed statues of - gold: there was the god himself standing in a chariot--the - charioteer of six winged horses--and of such a size that - he touched the roof of the building with his head; around - him were a hundred Nereids riding on dolphins, for such was - thought to be the number of them in that day. - - "There were also in the interior of the temple other images - which had been dedicated by private individuals. And around - the temple, on the outside, were placed statues of gold - of all the ten kings and of their wives; and there were - many other great offerings, both of kings and of private - individuals, coming both from the city itself and the - foreign cities over which they held sway. There was an - altar, too, which in size and workmanship corresponded to - the rest of the work, and there were palaces in like manner - which answered to the greatness of the kingdom and the - glory of the temple. - - "In the next place, they used fountains both of gold and - hot springs. These were very abundant, and both kinds - wonderfully adapted to use by reason of the sweetness and - excellence of their waters. They constructed buildings - about them, and planted suitable trees; also cisterns, - some open to the heaven, others which they roofed over, - to be used in winter as warm baths: there were the king's - baths, and the baths of private persons, which were kept - apart; also separate baths for women, and others again for - horses and cattle, and to them they gave as much adornment - as was suitable for them. The water which ran off they - carried, some to the grove of Poseidon, where were growing - all manner of trees of wonderful height and beauty, owing - to the excellence of the soil; the remainder was conveyed - by aqueducts which passed over the bridges to the outer - circles: and there were many temples built and dedicated - to many gods; also gardens and places of exercise, some - for men, and some set apart for horses, in both of the - two islands formed by the zones; and in the centre of the - larger of the two, there was a racecourse of a stadium - in width, and in length allowed to extend all round the - island, for horses to race in. - - "Also there were guard-houses at intervals for the - body-guard, the more trusted of whom had their duties - appointed to them in the lesser zone, which was nearer the - Acropolis; while the most trusted of all had houses given - them within the citadel, and about the persons of the - kings. The docks were full of triremes and naval stores, - and all things were quite ready for use. Enough of the plan - of the royal palace. Crossing the outer harbors, which were - three in number, you would come to a wall which began at - the sea and went all round; this was everywhere distant - fifty stadia from the largest zone and harbor, and enclosed - the whole, meeting at the mouth of the channel toward the - sea. - - "The entire area was densely crowded with habitations; - and the canal and the largest of the harbors were full - of vessels, and merchants coming from all parts, who, - from their numbers, kept up a multitudinous sound of - human voices and din of all sorts, night and day. I have - repeated his descriptions of the city and the parts about - the ancient palace nearly as he gave them, and now I must - endeavor to describe the nature and arrangement of the - rest of the country. The whole country was described as - being very lofty and precipitous on the side of the sea, - but the country immediately about and surrounding the city - was a level plain, itself surrounded by mountains which - descended toward the sea; it was smooth and even, but of - an oblong shape, extending in one direction three thousand - stadia, and going up the country from the sea through the - centre of the island two thousand stadia; the whole region - of the island lies toward the south, and is sheltered from - the north. - - "The surrounding mountains were celebrated for their number - and size and beauty, in which they exceeded all that are - now to be seen anywhere; having in them also many wealthy - inhabited villages, and rivers and lakes, and meadows - supplying food enough for every animal, wild or tame, and - wood of various sorts, abundant for every kind of work. - I will now describe the plain, which had been cultivated - during many ages by many generations of kings. It was - rectangular, and for the most part straight and oblong; and - what it wanted of the straight line followed the line of - the circular ditch. The depth and width and length of this - ditch were incredible, and gave the impression that such a - work, in addition to so many other works, could hardly have - been wrought by the hand of man. But I must say what I have - heard. - - "It was excavated to the depth of a hundred feet, and its - breadth was a stadium everywhere; it was carried round the - whole of the plain, and was ten thousand stadia in length. - It received the streams which came down the mountains, - and winding round the plain, and touching the city at - various points, was there let off into the sea. From above, - likewise, straight canals of a hundred feet in width were - cut in the plain, and again let off into the ditch, toward - the sea. These canals were at intervals of a hundred - stadia, and by them they brought down the wood from the - mountains to the city, and conveyed the fruits of the earth - in ships, cutting transverse passages from one canal into - another, and to the city. Twice in the year they gathered - the fruits of the earth--in winter having the benefit of - the rains, and in summer introducing the water of the - canals. As to the population, each of the lots in the plain - had an appointed chief of men who were fit for military - service, and the size of the lot was to be a square of ten - stadia each way, and the total number of all the lots was - sixty thousand. - - "And of the inhabitants, of the mountains and of the rest - of the country there was also a vast multitude having - leaders, to whom they were assigned according to their - dwellings and villages. The leader was required to furnish - for the wars the sixth portion of a war-chariot, so as - to make up a total of ten thousand chariots; also two - horses and riders upon them, and a light chariot without - a seat, accompanied by a fighting man on foot carrying a - small shield, and having a charioteer mounted to guide the - horses; also, he was bound to furnish two heavy-armed men, - two archers, two slingers, three stone-shooters, and three - javelin men, who were skirmishers, and four sailors, to - make up a complement of twelve hundred ships. Such was the - order of war in the royal city. - - "That of the other nine governments was different in each - of them, and would be wearisome to narrate. As to offices - and honors the following was the arrangement from the - first: each of the ten kings, in his own division and in - his own city, had the absolute control of the citizens, - and in many cases, of the laws, punishing and slaying - whomsoever he would. - - "Now the relations of their governments to one another - were regulated by the injunctions of Poseidon as the law - had handed them down. These were inscribed by the first - men on a column of orichalcum, which was situated in the - middle of the island, at the temple of Poseidon, whither - the people were gathered together every fifth and sixth - years alternately, thus giving equal honor to the odd and - to the even number. And when they were gathered together - they consulted about public affairs, and inquired if any - one had transgressed in anything, and passed judgment on - him accordingly--and before they passed judgment they gave - their pledges to one another in this wise: - - "There were bulls who had the range of the temple of - Poseidon; and the ten who were left alone in the temple, - after they had offered prayers to the gods that they might - take the sacrifices which were acceptable to them, hunted - the bulls without weapons, but with staves and nooses; and - the bull which they caught they led up to the column. The - victim was then struck on the head by them, and slain over - the sacred inscription. Now on the column, besides the law, - there was inscribed an oath invoking mighty curses on the - disobedient. When, therefore, after offering sacrifices - according to their customs, they had burnt the limbs of the - bull, they mingled a cup and cast in a clot of blood for - each of them. The rest of the victim they took to the fire, - after having made a purification of the column all round. - - "They then drew from the cup in golden vessels, and, - pouring a libation on the fire, they swore that they would - judge according to the laws on the column, and would punish - any one who had previously transgressed, and that for the - future they would not, if they could help, transgress any - of the inscriptions, and would not command, or obey any - ruler who commanded them, to act otherwise than according - to the laws of their father Poseidon. - - "This was the prayer which each of them offered up for - himself and for his family, at the same time drinking, and - dedicating the vessel in the temple of the god; and, after - spending some necessary time at supper, when darkness came - on and the fire about the sacrifice was cool, all of them - put on most beautiful azure robes, and, sitting on the - ground at night near the embers of the sacrifices on which - they had sworn, and extinguishing all the fires about the - temple, they received and gave judgment, if any of them had - any accusation to bring against any one; and, when they had - given judgment, at daybreak they wrote down their sentences - on a golden tablet, and deposited them as memorials with - their robes. - - "There were many special laws which the several kings had - inscribed about the temple, but the most important was the - following: that they were not to take up arms against one - another, and they were all to come to the rescue, if any - one in any city attempted to overthrow the royal house. - Like their ancestors, they were to deliberate in common - about war and other matters, giving the supremacy to the - family of Atlas; and the king was not to have the power of - life or death over any of his kinsmen, unless he had the - assent of the majority of the ten kings. - - "Such was the vast power which the god settled in the lost - island of Atlantis; and this he afterward directed against - our land on the following pretext, as traditions tell. For - many generations, as long as the divine nature lasted in - them, they were obedient to the laws, and well-affectioned - toward the gods, who were their kinsmen, for they possessed - true and in every way great spirits, practicing gentleness - and wisdom in the various chances of life, and in their - intercourse with one another. - - "They despised everything but virtue, not caring for - their present state of life, and thinking lightly on the - possession of gold, and other property, which seemed only a - burden to them; neither were they intoxicated by luxury, - nor did wealth deprive them of their self-control; but - they were sober, and saw clearly that all these goods are - increased by virtuous friendship with one another, and that - by excessive zeal for them and honor of them, the good of - them is lost, and friendship perishes with them. - - "By such reflections, and by the continuance in them of a - divine nature, all that which we have described waxed and - increased in them; but when this divine portion began to - fade away in them, and became diluted too often, and with - too much of the mortal admixture, and the human nature - got the upper hand, then, they being unable to bear their - fortune, became unseemly, and to him who had an eye to see, - they began to appear base, and had lost the fairest of - their precious gifts; but to those who had no eye to see - the true happiness they still appeared glorious and blessed - at the very time when they were filled with unrighteous - avarice and power. Zeus, the god of gods, who rules with - law, and is able to see into such things, perceiving that - an honorable race was in a most wretched state, and wanting - to inflict punishment on them, that they might be chastened - and improved, collected all the gods into his most holy - habitation, which, being placed in the centre of the world, - sees all things that partake of generations. And when he - had called them together, he spake as follows:" - -The story abruptly ends here, for Plato left no further record. - - - - -CHAPTER XXXIX - -NATURE'S WARNING OF COMING EARTHQUAKES - - -That there are signs of coming earthquakes which might be read by -man, had he sufficient knowledge, there would seem to be but little -doubt. These phenomena follow natural laws so that the approach of an -earthquake must necessarily be in a definite order both as regards -the phenomena which precede as well as those which follow it. There -should, therefore, be signs that would enable one to predict its -coming, although it must be acknowledged that these signs, so far as -we actually know, are indistinct. - -It may seem to the unthinking and unobservant that the awful -catastrophe of an earthquake comes entirely unheralded; that, -apparently, it is not until the earth's surface begins to rock to -and fro under the mighty forces that are causing destruction that -its presence can be known. There are, however, many reasons for -believing that in, perhaps, the greatest number of cases, it might -have been foreseen, if greater attention had been given to the -slight indications of its probable approach a short time before its -occurrence. - -It is evident that the conditions of great pressure or stress in the -earth's crust which finally result in a disastrous earthquake have -been slowly accumulating for a long time, and that when the pressure -at last reaches a point where the crust has to yield or slip, the -ground is suddenly crushed and tossed to and fro while vast fissures -and chasms are produced in the subterranean regions. At those points -of the earth immediately above or in the neighborhood of such regions -it is possible that there are many signs of the coming quake; -and, although indistinguishable by our duller senses, are readily -appreciated by the more highly developed senses of the lower animals. -Indeed, had we accustomed ourselves to reading the various indications -of nature as the lower animals have, we, too, might be able to read -these warnings of the coming earthquake. - -At great distances from the place where the earthquake starts there -would necessarily be a better opportunity for predicting its approach. -As already stated, what is called an earthquake does not consist -of a single shaking of the ground, but of a highly complex series -of shakings. According to Mallet, the following waves start at the -same time from the place of origin of an earthquake, when located -on the bed of an ocean; i. e., an earth sound wave and a earth wave -constituting the earth's shake; a sound wave through the ocean, -another through the air; a sea wave called by him a forced sea wave, -and finally the great sea wave. - -These waves reach a distant point in the following order: the sound -wave through the earth and the great earthquake or shake which -produces the damage. Then a smaller sea wave called the forced sea -wave. This is followed almost immediately by the sound wave through -the sea. Next come the air sound wave and finally the great sea wave; -which, rushing in on the shore, sweeps nearly everything before it. - -In other words, the disturbances produced by the great earthquake -follow in this order of sequence. If, therefore, the great earthquake -wave proper transmitted through the earth should for any reason be -delayed in reaching a distant place, the great sound waves should be -able to give warning of the coming disturbances. - -Again, as we have already seen, the earthquake wave is preceded by a -number of preliminary tremors, and is followed by a number of after -tremors or _earthquake echoes_. Since, therefore, the preliminary -waves reach a place first, it would seem that the approach of an -earthquake must be heralded by the preliminary tremors. These, -perhaps, at least in part, enable the lower animals to detect its -coming. - -Again, in almost all instances there are a number of preliminary -shocks that precede the great earthquake shock. Some of these -preliminary shocks continue at intervals for several days or even -longer. Sometimes, indeed, these subterranean sounds fail to be -followed by earthquakes. Milne thinks that these sounds are caused -by the preliminary tremors which precede the principal shock of the -earthquake and that they reach the place first. Here again then it -is evident that, were we able to interpret properly these sounds, we -would probably be able to foretell the coming quake with a fair degree -of certainty. - -There would appear to be no reasonable doubt that in some manner -which we have not yet been able to discover, but probably along some -of the lines indicated above, animals are capable of recognizing a -coming earthquake. Long before the coming of the catastrophe they are -said to exhibit extreme terror, and in many cases appear to seek the -companionship of man, as if for protection. - -That the senses of smell and hearing are far more acute in the lower -animals than in man no one can reasonably doubt. The manner in which -a trained dog can follow a scent, for a long time after the animal -or thing producing it has passed, far exceeds the power of scent -possessed by man, and it is more than likely that this same power is -possessed by all animals who live upon or prey upon other animals. It -is probable that faintly odorous vapors or gases escape from the crust -shortly before the great shock occurs, and that these faint odors are -warnings to the animals of the approaching calamity. The sense of -hearing also is much more acute in the lower animals. - -Daubeny is evidently of this belief, as will be seen from the -following: - - "These gases and vapors (alluding to emanations given off - from the ground during earthquakes) exert an influence - on the barometer, which does appear to be indirectly - affected by the earthquake. Then, similar properties - also may occasion that uneasiness which animals are said - to evince before any such event. Thus, according to the - accounts of some writers, rats and mice leave their holes, - alligators seek the dry land, quadrupeds snuff the ground, - and manifest such signs of the impending calamity that in - countries where earthquakes are common, the inhabitants - take the alarm in consequence, and escape from their - houses. It is right, however, to add, that more recent - authorities dispute altogether the correctness of these - statements." - -Dutton doubts the ability of animals to foretell coming earthquake -shocks. - -But that the lower animals do exhibit signs of fear at the approach of -an earthquake has been repeatedly asserted by good observers. - -Hamilton, who made a careful examination of the neighboring country -during the great earthquake at Calabria, asserts that horses and oxen -during the shocks extended their legs widely in order to avoid being -thrown down, "and that hogs, oxen, horses, and mules, and also geese, -appeared to be painfully aware of the approach of the earthquake of -Calabria; and the neighing of a horse, the braying of an ass, or the -cackling of a goose, even when he (Hamilton) was making his survey -(after the occurrence of the great earthquake shock), drove the people -out of their temporary sheds in expectation of a shock." - -It is asserted that birds appear to be especially sensible to a coming -earthquake shock. That geese will quit the water in which they were -swimming before the earthquake and will not return to it. It is quite -possible that these birds with their heads immersed in the water can -hear the distant murmurings long before they become audible in the air. - -Von Hoff makes the following statement: - - "It has been remarked that at such times (immediately - before the coming of an earthquake shock), domestic animals - showed a decided uneasiness, dogs howled mournfully, horses - neighed in an unusual manner, and poultry flew restlessly - about. These latter phenomena might easily be produced by - mephitic vapours, which often ascend to the surface of the - earth before the breaking out of an earthquake." - -Mallet states that there is abundant evidence that earthquake shocks, -even when not of very great intensity, produce nausea in both men and -women. This would seem natural, since, as everyone knows, until one -is accustomed to sea-voyages, merely to be tossed to and fro by the -motion of the waves results in the production of sea-sickness. - -It has been also noticed that during earthquakes fish which under -ordinary circumstances live in the mud at the bottom of bodies of -water come near to the surface and at such times can be caught in -great numbers. - -Mallet cites the following effects produced by earthquakes: - - "Amongst the effects supposed to be produced by the - earthquake on the atmosphere were reckoned tempestuous - winds, thunder-storms, meteors, coldness of the air, - severe winters, heavy rains, miasmata, producing diseases - and affecting vegetation. A very remarkable instance of - the latter is quoted, namely, that in Peru, after the - earthquake of 1687, wheat and barley would not thrive at - all, though formerly the country was remarkably favourable - for them." - -Sir Charles Lyell notes the following phenomena attending earthquakes: - - "Irregularities in the seasons preceding or following the - shocks; sudden gusts of wind, interrupted by dead calms; - violent rains at unusual seasons, or in countries where, - as a rule, they are almost unknown; a reddening of the - sun's disk, and haziness in the air, often continued for - months; an evolution of electric matter, or of inflammable - gas from the soil, with sulphurous and mephitic vapours; - noises underground, like the running of carriages, or - the discharge of artillery, or distant thunder; animals - uttering cries of distress, and evincing extraordinary - alarm, being more sensitive than men to the slightest - movement; a sensation like sea-sickness, and a dizziness in - the head, experienced by men. These, and other phenomena, - less connected with our present subject as geologists, have - recurred again and again at distant ages, and in all parts - of the globe." - - -THE END - - - - -FOOTNOTES: - -[Footnote 1: A point on the other side of the earth directly opposite -a given point.] - -[Footnote 2: A fracture of a stratum, or a general rock mass, with a -relative displacement of the opposite sides of the break. - -The plane or fracture of a fault, known as the fault-plane, is seldom -vertical. The higher side is called the heaved or upthrow side; the -opposite side the thrown or downthrow side.] - -[Footnote 3: _Tectonic Earthquake_. An earthquake due to the sudden -slip of faulted strata.] - -[Footnote 4: _I. e._, burnt out mountain, extinct volcano.] - -[Footnote 5: _Epicentre._ A point on the surface of the earth -vertically above the point of origin of an earthquake, or the place -where it starts.] - - - - -Transcriber's Notes - - -Obvious printer errors have been silently corrected. - -Some illustrations have been moved to paragraph breaks. - -Page 43: Kamehamoha could be a typo for Kamehameha. - -Page 68: Changed "salter" to "saltier." - (Orig: another with water salter than the sea,) - -Page 76: Changed "Ena" to "Etna." - (Orig: during his time Mt. Ena had lost so much of its height) - -Page 115: "eruption during the winter of 1841-43," could be a typo for -1841-42 or 1842-43. - -Page 122: "Mont Pelee" could be a typo for "Mount Pelee." - -Page 136: 43 deg. C." (109 deg. 4' F.). could be a typo for (109.4 deg. F.). - -Page 341: Changed one-eight to one-eighth. - (Orig: It was equal to one-eight of a Roman mile) - -Retained the following spelling variations: - - Page 49: The largest volcano in Iceland, the Dyngjufkoell, - Page 57: The largest volcano in Iceland is Dyngjufjoll. - - Pages 52, 193, 311: Geikie - Page 181: Geicke - - Pages 17, 156, 257: Hindostan - Page 165: Hindustan - - Page 63: Lucullis - Page 76: Lucullus - - - - - - - -End of the Project Gutenberg EBook of The Wonder Book of Volcanoes and -Earthquakes, by Edwin J. 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