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diff --git a/15884-0.txt b/15884-0.txt new file mode 100644 index 0000000..2670472 --- /dev/null +++ b/15884-0.txt @@ -0,0 +1,10632 @@ +*** START OF THE PROJECT GUTENBERG EBOOK 15884 *** +Young Folks' Library + +Selections from the Choicest Literature of All +Lands; Folk-Lore, Fairy Tales, Fables, Legends, +Natural History, Wonders of Earth, Sea +and Sky, Animal Stories, Sea Tales, +Brave Deeds, Explorations, Stories +of School and College Life, +Biography, History, Patriotic +Eloquence, Poetry + +Third Edition + +Revised in Conference by + + Thomas Bailey Aldrich, Editor-in-Chief, + President William Jewett Tucker, + Hamilton Wright Mabie, + Henry Van Dyke, + Nathan Haskell Dole + +Twenty Volumes Richly Illustrated + +Boston +Hall and Locke Company +Publishers +Stanhope Press +F.H. Gilson Company +Boston, U.S.A. + +1902 + + + + + + +EDITORIAL BOARD + + + THOMAS BAILEY ALDRICH, Editor-in-chief, + Author, poet, former editor _Atlantic Monthly,_ Boston, Mass. + + The HON. JOHN D. LONG, + Secretary of the United States Navy, Boston. + + HAMILTON WRIGHT MABIE, LL.D., + Author, literarian, associate editor _The Outlook_, New York. + + ERNEST THOMPSON SETON, + Artist, author, New York. + + JOHN TOWNSEND TROWBRIDGE, + Author, poet, and editor, Arlington, Mass. + + The REVEREND CYRUS TOWNSEND BRADY, + Archdeacon, author, Philadelphia. + + JOEL CHANDLER HARRIS, + Humorous writer, Atlanta, Ga. + + MARY HARTWELL CATHERWOOD, + Historical novelist, Chicago. + + LAURA E. RICHARDS, + Author, Gardiner, Me. + + ROSWELL FIELD, + Author, editor _The Evening Post_, Chicago. + + TUDOR JENKS, + Author, associate editor _Saint Nicholas_, New York. + + GEORGE A. HENTY, + Traveller, author, London, England. + + KIRK MUNROE, + Writer of stories for boys, Cocoanut Grove, Fla. + + EDITH M. THOMAS, + Poet, West New Brighton, N.Y. + + CAROLINE TICKNOR, + Author, editor, Boston. + + NATHAN HASKELL DOLE, + Author, translator, literary editor _Current History_, Boston. + + WILLIAM RAINEY HARPER, D.D., LL.D., + President Chicago University. + + DAVID STARR JORDAN, M.D., LL.D., + President Leland Stanford Junior University, naturalist, writer, + Stanford University, Cal. + + CHARLES ELIOT NORTON, A.M., LL.D., etc., + Scholar, author, Emeritus Professor of Art at Harvard University. + + HENRY VAN DYKE, D.D., LL.D., + Clergyman, author, Professor Princeton University. + + The REVEREND THOMAS J. SHAHAN, + Dean of the Faculty of Divinity, Professor of Early Ecclesiastical + History, Catholic University, Washington, D.C. + + WILLIAM P. TRENT, + Author, editor, Professor of English Literature, Columbia University, + New York City. + + EDWARD SINGLETON HOLDEN, A.M., LL.D., + Ex-president University of California, astronomer, author, + U.S. Military Academy, West Point. + + EDWIN ERLE SPARKS, + Professor of American History, Chicago University. + + The VERY REV. GEORGE M. GRANT, D.D., LL.D., + Educator, author, vice-principal Queen's College, Kingston, Ont. + + BARONESS VON BULOW, + Educator, author, Dresden, Germany. + + ABBIE FARWELL BROWN, + Author, Boston. + + CHARLES WELSH, Managing Editor, + Author, lecturer, editor, Winthrop Highlands, Mass. + + + + +LIST OF VOLUMES + + + VOLUME I. + + THE STORY TELLER + Edited by CHARLES ELIOT NORTON + + + VOLUME II. + + THE MERRY MAKER + Edited by JOEL CHANDLER HARRIS + + + VOLUME III. + + FAMOUS FAIRY TALES + Edited by ROSWELL FIELD + + + VOLUME IV. + + TALES OF FANTASY + Edited by TUDOR JENKS + + + VOLUME V. + MYTHS AND LEGENDS + Edited by THOMAS J. SHAHAN + + + VOLUME VI. + + THE ANIMAL STORY BOOK + Edited by ERNEST THOMPSON SETON + + + VOLUME VII. + + SCHOOL AND COLLEGE DAYS + Edited by KIRK MUNROE and + MARY HARTWELL CATHERWOOD + + + VOLUME VIII. + + BOOK OF ADVENTURE + Edited by NATHAN HASKELL DOLE + + + VOLUME IX. + + FAMOUS EXPLORERS + Edited by EDWIN ERLE SPARKS + + + VOLUME X. + + BRAVE DEEDS + Edited by JOHN TOWNSEND TROWBRIDGE + + + VOLUME XI. + + WONDERS OF EARTH, SEA AND SKY + Edited by EDWARD SINGLETON HOLDEN + + + VOLUME XII. + + FAMOUS TRAVELS + Edited by GEORGE A. HENTY + + + VOLUME XIII. + + SEA STORIES + Edited by CYRUS TOWNSEND BRADY + + + VOLUME XIV. + + A BOOK OF NATURAL HISTORY + Edited by DAVID STARR JORDAN + + + VOLUME XV. + + HISTORIC SCENES IN FICTION + Edited by HENRY VAN DYKE + + + VOLUME XVI. + + FAMOUS BATTLES BY LAND AND SEA + Edited by JOHN D. LONG + + + VOLUME XVII. + + MEN WHO HAVE RISEN + Edited by HAMILTON WRIGHT MABIE. + + + VOLUME XVIII. + + BOOK OF PATRIOTISM + Edited by + + + VOLUME XIX. + + LEADERS OF MEN, OR HISTORY TOLD IN BIOGRAPHY + Edited by WILLIAM RAINEY HARPER + + + VOLUME XX. + + FAMOUS POEMS + Selected by THOMAS BAILEY ALDRICH, + with Poetical Foreword by EDITH M. THOMAS. + + + +[Illustration: A GEYSER] + + + + +Volume XI: WONDERS OF EARTH, SEA AND SKY + +Edited by EDWARD SINGLETON HOLDEN + +Boston +Hall and Locke Company Publishers + +1902 + + + + +CONTENTS + + + LIST OF ILLUSTRATIONS xi + + THE MARVELS OF NATURE xiii + BY PROFESSOR E.S. HOLDEN. + + WHAT THE EARTH'S CRUST IS MADE OF 1 + BY AGNES GIBERNE. + + AMERICA THE OLD WORLD 45 + BY LOUIS AGASSIZ. + + SOME RECORDS OF THE ROCKS 77 + BY N.S. SHALER. + + THE PITCH LAKE IN THE WEST INDIES 97 + BY CHARLES KINGSLEY. + + A STALAGMITE CAVE 111 + BY SIR C. WYVILLE THOMSON. + + THE BIG TREES OF CALIFORNIA 119 + BY ALFRED RUSSEL WALLACE. + + WHAT IS EVOLUTION? 127 + BY PROFESSOR EDWARD S. HOLDEN. + + HOW THE SOIL IS MADE 135 + BY CHARLES DARWIN. + + ZOÖLOGICAL MYTHS 143 + BY ANDREW WILSON. + + ON A PIECE OF CHALK 171 + BY T.H. HUXLEY. + + A BIT OF SPONGE 205 + BY A. WILSON. + + THE GREATEST SEA-WAVE EVER KNOWN 211 + BY R.A. PROCTOR. + + THE PHOSPHORESCENT SEA 228 + BY W.S. DALLAS. + + COMETS 251 + BY CAMILLE FLAMMARION. + + THE TOTAL SOLAR ECLIPSE OF 1883 261 + BY E.S. HOLDEN. + + HALOS--PARHELIA--THE SPECTRE OF + THE BROCKEN, ETC. 268 + BY CAMILLE FLAMMARION. + + THE PLANET VENUS 282 + BY AGNES M. CLERKE. + + THE STARS 296 + BY SIR R.S. BALL. + + RAIN AND SNOW 342 + BY JOHN TYNDALL. + + THE ORGANIC WORLD 357 + BY ST. GEORGE MIVART. + + INHABITANTS OF MY POOL 366 + BY ARABELLA B. BUCKLEY. + + BIOGRAPHICAL NOTES. 387 + + SUGGESTIONS FOR SUPPLEMENTARY + READING. 389 + + +NOTE. + +The publishers' acknowledgments are due to Messrs. Houghton, Mifflin & +Co., for permission to use "America and the Old World," by L. Agassiz; +to Messrs. D.C. Heath & Co. for permission to use "Some Records of the +Rocks," by Professor N.S. Shaler; and to Professor E.S. Holden for +permission to use "What is Evolution?" and "An Astronomer's Voyage to +Fairy Land." + + + + +LIST OF COLORED ILLUSTRATIONS + + A GEYSER. _Frontispiece, See Page_ 47 + + VIEW IN A CAÑON _Face Page_ 12 + + A VOLCANO 48 + + A STALAGMITE CAVE 116 + + WHERE SPONGES GROW 208 + + A COMET 254 + + THE SPECTRE OF THE BROCKEN 272 + + +AND ONE HUNDRED AND SIXTY-FOUR BLACK AND WHITE ILLUSTRATIONS IN THE +TEXT. + + + + +THE MARVELS OF NATURE + +BY EDWARD S. HOLDEN, M.A., Sc.D. LL.D. + + +The Earth, the Sea, the Sky, and their wonders--these are the themes +of this volume. The volume is so small, and the theme so vast! Men +have lived on the earth for hundreds of thousands of years; and its +wonders have increased, not diminished, with their experience. + +To our barbarous ancestors of centuries ago, all was mystery--the +thunder, the rainbow, the growing corn, the ocean, the stars. +Gradually and by slow steps they learned to house themselves in trees, +in caves, in huts, in houses; to find a sure supply of food; to +provide a stock of serviceable clothing. The arts of life were born; +tools were invented; the priceless boon of fire was received; tribes +and clans united for defence; some measure of security and comfort was +attained. + +With security and comfort came leisure; and the mind of early Man +began curiously to inquire the meaning of the mysteries with which he +was surrounded. That curious inquiry was the birth of Science. Art was +born when some far-away ancestor, in an idle hour, scratched on a +bone the drawing of two of his reindeer fighting, or carved on the +walls of his cave the image of the mammoth that he had but lately +slain with his spear and arrows. + +In a mind that is completely ignorant there is no wonder. Wonder is +the child of knowledge--of partial and imperfect knowledge, to be +sure, but still, of knowledge. The very first step in Science is to +make an inventory of external Nature (and by and by of the faculties +of the mind that thinks). The second step is to catalogue similar +appearances together. It is a much higher flight to seek the causes of +likenesses thus discovered. + +A few of the chapters of this volume are items in a mere catalogue of +wonders, and deserve their place by accurate and eloquent description. +Most of them, however, represent higher stages of insight. In the +latter, Nature is viewed not only with the eye of the observer, but +also with the mind's eye, curious to discover the reasons for things +seen. The most penetrating inward inquiry accompanies the acutest +external observation in such chapters as those of Darwin and Huxley, +here reprinted. + +Now, the point not to be overlooked is this: to Darwin and Huxley, as +to their remote and uncultured ancestors, the World--the Earth, the +Sea, the Sky--is full of wonders and of mysteries, but the wonders are +of a higher order. The problems of the thunder and of the rainbow as +they presented themselves to the men of a thousand generations ago, +have been fully solved: but the questions; what is the veritable +nature of electricity, exactly how does it differ from light, are +still unanswered. And what are simple problems like these to the +questions: what is love; why do we feel a sympathy with this person, +an antipathy for that; and others of the sort? Science has made almost +infinite advances since pre-historic man first felt the feeble current +of intellectual curiosity amid his awe of the storm; it has still to +grow almost infinitely before anything like a complete explanation +even of external Nature is achieved. + +Suppose that, at some future day, all physical and mechanical laws +should be found to be direct consequences of a single majestic law, +just as all the motions of the planets are (but--are they?) the direct +results of the single law of gravitation. Gravitation will, probably, +soon be explained in terms of some remoter cause, but the reason of +that single and ultimate law of the universe which we have imagined +would still remain unknown. Human knowledge will always have limits, +and beyond those limits there will always be room for mystery and +wonder. A complete and exhaustive explanation of the world is +inconceivable, so long as human powers and capacities remain at all as +they now are. + +It is important to emphasize such truths, especially in a book +addressed to the young. When a lad hears for the first time that an +astronomer, by a simple pointing of his spectroscope, can determine +with what velocity a star is approaching the earth, or receding from +it, or when he hears that the very shape of the revolving masses of +certain stars can be calculated from simple measures of the sort, he +is apt to conclude that Science, which has made such astounding +advances since the days of Galileo and Newton, must eventually reach a +complete explanation of the entire universe. The conclusion is not +unnatural, but it is not correct. There are limits beyond which +Science, in this sense, cannot go. Its scope is limited. Beyond its +limits there are problems that it cannot solve, mysteries that it +cannot explain. + +At the present moment, for example, the nature of Force is unknown. A +weight released from the hand drops to the earth. Exactly what is the +nature of the force with which the earth attracts it? We do not know, +but it so happens that it is more than likely that an explanation will +be reached in our own day. Gravity will be explained in terms of some +more general forces. The mystery will be pushed back another step, and +yet another and another. But the progress is not indefinite. If all +the mechanical actions of the entire universe were to be formulated as +the results of a single law or cause, the cause of that cause would be +still to seek, as has been said. + +We have every right to exult in the amazing achievements of Science; +but we have not understood them until we realize that the universe of +Science has strict limits, within which all its conquests must +necessarily be confined. Humility, and not pride, is the final lesson +of scientific work and study. + + * * * * * + +The choice of the selections printed in this volume has been +necessarily limited by many hampering conditions, that of mere space +being one of the most harassing. Each of the chapters might readily be +expanded into a volume. Volumes might be added on topics almost +untouched here. It has been necessary to pass over almost without +notice matters of surpassing interest and importance: Electricity and +its wonderful and new applications; the new Biology, with its views +upon such fundamental questions as the origins of life and death; +modern Astronomy, with its far-reaching pronouncements upon the fate +of universes. All these can only be touched lightly, if at all. It is +the chief purpose of this volume to point the way towards the most +modern and the greatest conclusions of Science, and to lay foundations +upon which the reading of a life-time can be laid. + +[Illustration: Signature: Edward S. Holden] + +UNITED STATES MILITARY ACADEMY, WEST POINT, _January 1, 1902_. + + + + +WONDERS OF EARTH, SEA, AND SKY + + + + +WHAT THE EARTH'S CRUST IS MADE OF + +(FROM THE WORLD'S FOUNDATIONS.) + +BY AGNES GIBERNE. + + + "Stand still and consider the wondrous works of God." + +[Illustration] + +What is the earth made of--this round earth upon which we human beings +live and move? + +A question more easily asked than answered, as regards a very large +portion of it. For the earth is a huge ball nearly eight thousand +miles in diameter, and we who dwell on the outside have no means of +getting down more than a very little way below the surface. So it is +quite impossible for us to speak positively as to the inside of the +earth, and what it is made of. Some people believe the earth's inside +to be hard and solid, while others believe it to be one enormous lake +or furnace of fiery melted rock. But nobody really knows. + +This outside crust has been reckoned to be of many different +thicknesses. One man will say it is ten miles thick, and another will +rate it at four hundred miles. So far as regards man's knowledge of +it, gained from mining, from boring, from examination of rocks, and +from reasoning out all that may be learned from these observations, we +shall allow an ample margin if we count the field of geology to extend +some twenty miles downwards from the highest mountain-tops. Beyond +this we find ourselves in a land of darkness and conjecture. + +Twenty miles is only one four-hundredth part of the earth's +diameter--a mere thin shell over a massive globe. If the earth were +brought down in size to an ordinary large school globe, a piece of +rough brown paper covering it might well represent the thickness of +this earth-crust, with which the science of geology has to do. And the +whole of the globe, this earth of ours, is but one tiny planet in the +great Solar System. And the centre of that Solar System, the blazing +sun, though equal in size to more than a million earths, is yet +himself but one star amid millions of twinkling stars, scattered +broadcast through the universe. So it would seem at first sight that +the field of geology is a small field compared with that of +astronomy.... + +With regard to the great bulk of the globe little can be said. Very +probably it is formed through and through of the same materials as the +crust. This we do not know. Neither can we tell, even if it be so +formed, whether the said materials are solid and cold like the +outside crust, or whether they are liquid with heat. The belief has +been long and widely held that the whole inside of the earth is one +vast lake or furnace of melted fiery-hot material, with only a thin +cooled crust covering it. Some in the present day are inclined to +question this, and hold rather that the earth is solid and cold +throughout, though with large lakes of liquid fire here and there, +under or in her crust, from which our volcanoes are fed.... + +The materials of which the crust is made are many and various; yet, +generally speaking, they may all be classed under one simple word, and +that word is--_Rock_. + +It must be understood that, when we talk of rock in this geological +sense, we do not only mean hard and solid stone, as in common +conversation. Rock may be changed by heat into a liquid or "molten" +state, as ice is changed by heat to water. Liquid rock may be changed +by yet greater heat to vapor, as water is changed to steam, only we +have in a common way no such heat at command as would be needed to +effect this. Rock may be hard or soft. Rock maybe chalky, clayey, or +sandy. Rock may be so close-grained that strong force is needed to +break it; or it may be so porous--so full of tiny holes--that water +will drain through it; or it may be crushed and crumbled into loose +grains, among which you can pass your fingers. + +The cliffs above our beaches are rock; the sand upon our seashore is +rock; the clay used in brick-making is rock; the limestone of the +quarry is rock; the marble of which our mantel-pieces are made is +rock. The soft sandstone of South Devon, and the hard granite of the +north of Scotland, are alike rock. The pebbles in the road are rock; +the very mould in our gardens is largely composed of crumbled rock. So +the word in its geological sense is a word of wide meaning. + +Now the business of the geologist is to read the history of the past +in these rocks of which the earth's crust is made. This may seem a +singular thing to do, and I can assure you it is not an easy task. + +For, to begin with, the history itself is written in a strange +language, a language which man is only just beginning to spell out and +understand. And this is only half the difficulty with which we have to +struggle. + +If a large and learned book were put before you and you were set to +read it through, you would perhaps, have no insurmountable difficulty, +with patience and perseverance, in mastering its meaning. + +But how if the book were first chopped up into pieces, if part of it +were flung away out of reach, if part of it were crushed into a pulp, +if the numbering of the pages were in many places lost, if the whole +were mixed up in confusion, and if _then_ you were desired to sort, +and arrange, and study the volume? + +Picture to yourself what sort of a task this would be, and you will +have some idea of the labors of the patient geologist. + +Rocks may be divided into several kinds or classes. For the present +moment it will be enough to consider the two grand +divisions--_Stratified rocks_ and _Unstratified rocks_. + +Unstratified rocks are those which were once, at a time more or less +distant, in a melted state from intense heat, and which have since +cooled into a half _crystallized_ state; much the same as water, when +growing colder, cools and crystallizes into ice. Strictly speaking, ice +is rock, just as much as granite and sandstone are rock. Water itself +is of the nature of rock, only as we commonly know it in the liquid +state we do not commonly call it so. + +[Illustration: UNSTRATIFIED ROCK.--A VOLCANIC BLOCK.] + +"Crystallization" means those particular forms or shapes in which the +particles of a liquid arrange themselves, as that liquid hardens into +a solid--in other words, as it freezes. Granite, iron, marble, are +frozen substances, just as truly as ice is a frozen substance; for +with greater heat they would all become liquid like water. When a +liquid freezes, there are always crystals formed, though these are not +always visible without the help of a microscope. Also the crystals are +of different shapes with different substances. + +If you examine the surface of a puddle or pond, when a thin covering +of ice is beginning to form, you will be able to see plainly the +delicate sharp needle-like forms of the ice crystals. Break a piece of +ice, and you will find that it will not easily break just in any way +that you may choose, but it will only split along the lines of these +needle-like crystals. This particular mode of splitting in a +crystallized rock is called the _cleavage_ of that rock. + +Crystallization may take place either slowly or rapidly, and either +in the open air or far below ground. The lava from a volcano is an +example of rock which has crystallized rapidly in the open air; and +granite is an example of rock which has crystallized slowly +underground beneath great pressure. + +Stratified rocks, on the contrary, which make up a very large part of +the earth's crust, are not crystallized. Instead of having cooled from +a liquid into a solid state, they have been slowly _built up_, bit by +bit and grain upon grain, into their present form, through long ages +of the world's history. The materials of which they are made were +probably once, long, long ago, the crumblings from granite and other +crystallized rocks, but they show now no signs of crystallization. + + +[Illustration: SECTION OF STRATIFIED ROCKS. + +_a._ Conglomerate. _b._ Pebbly Sandstone, _c._ Thin-bedded Sandstone, +_d._ Shelly Sandstone, _e._ Shale. _f._ Limestone.] + +They are called "stratified" because they are in themselves made up of +distinct layers, and also because they lie thus one upon another in +layers, or _strata_, just as the leaves of a book lie, or as the +bricks of a house are placed. + +Throughout the greater part of Europe, of Asia, of Africa, of North +and South America, of Australia, these rocks are to be found, +stretching over hundreds of miles together, north, south, east, and +west, extending up to the tops of some of the earth's highest +mountains, reaching down deep into the earth's crust. In many parts if +you could dig straight downwards through the earth for thousands of +feet, you would come to layer after layer of these stratified rocks, +one kind below another, some layers thick, some layers thin, here a +stratum of gravel, there a stratum of sandstone, here a stratum of +coal, there a stratum of clay. + +But how, when, where, did the building up of all these rock-layers +take place? + +[Illustration: THE BEACH IN THE FOREGROUND IS A ROCKY SHELF, THE +REMNANT OF THE CLIFF WHICH ONCE EXTENDED OUT TO THE ISLAND.] + + +People are rather apt to think of land and water on the earth as if +they were fixed in one changeless form,--as if every continent and +every island were of exactly the same shape and size now that it +always has been and always will be. + +Yet nothing can be further from the truth. The earth-crust is a scene +of perpetual change, of perpetual struggle, of perpetual building up, +of perpetual wearing away. + +The work may go on slowly, but it does go on. The sea is always +fighting against the land, beating down her cliffs, eating into her +shores, swallowing bit by bit of solid earth; and rain and frost and +inland streams are always busily at work, helping the ocean in her +work of destruction. Year by year and century by century it continues. +Not a country in the world which is bordered by the open sea has +precisely the same coast-line that it had one hundred years ago; not a +land in the world but parts each century with masses of its material, +washed piecemeal away into the ocean. + +Is this hard to believe? Look at the crumbling cliffs around old +England's shores. See the effect upon the beach of one night's fierce +storm. Mark the pathway on the cliff, how it seems to have crept so +near the edge that here and there it is scarcely safe to tread; and +very soon, as we know, it will become impassable. Just from a mere +accident, of course,--the breaking away of some of the earth, loosened +by rain and frost and wind. But this is an accident which happens +daily in hundreds of places around the shores. + +Leaving the ocean, look now at this river in our neighborhood, and see +the slight muddiness which seems to color its waters. What from? Only +a little earth and sand carried off from the banks as it flowed,--very +unimportant and small in quantity, doubtless, just at this moment and +just at this spot. But what of that little going on week after week, +and century after century, throughout the whole course of the river, +and throughout the whole course of every river and rivulet in our +whole country and in every other country. A vast amount of material +must every year be thus torn from the land and given to the ocean. For +the land's loss here is the ocean's gain. + +And, strange to say, we shall find that this same ocean, so busily +engaged with the help of its tributary rivers in pulling down land, is +no less busily engaged with their help in building it up. + +You have sometimes seen directions upon a vial of medicine to "shake" +before taking the dose. When you have so shaken the bottle the clear +liquid grows thick; and if you let it stand for awhile the thickness +goes off, and a fine grain-like or dust-like substance settles down at +the bottom--the settlement or _sediment_ of the medicine. The finer +this sediment, the slower it is in settling. If you were to keep the +liquid in gentle motion, the fine sediment would not settle down at +the bottom. With coarser and heavier grains the motion would have to +be quicker to keep them supported in the water. + +Now it is just the same thing with our rivers and streams. Running +water can support and carry along sand and earth, which in still water +would quickly sink to the bottom; and the more rapid the movement of +the water, the greater is the weight it is able to bear. + +This is plainly to be seen in the case of a mountain torrent. As it +foams fiercely through its rocky bed it bears along, not only mud and +sand and gravel, but stones and even small rocks, grinding the latter +roughly together till they are gradually worn away, first to rounded +pebbles, then to sand, and finally to mud. The material thus swept +away by a stream, ground fine, and carried out to sea--part being +dropped by the way on the river-bed--is called _detritus_, which +simply means _worn-out_ material. + +[Illustration: A MOUNTAIN TORRENT.] + +The tremendous carrying-power of a mountain torrent can scarcely be +realized by those who have not observed it for themselves. I have seen +a little mountain-stream swell in the course of a heavy thunderstorm +to such a torrent, brown and turbid with earth torn from the +mountainside, and sweeping resistlessly along in its career a shower +of stones and rock-fragments. That which happens thus occasionally +with many streams is more or less the work all the year round of many +more. + +As the torrent grows less rapid, lower down in its course, it ceases +to carry rocks and stones, though the grinding and wearing away of +stones upon the rocky bed continues, and coarse gravel is borne still +upon its waters. Presently the widening stream, flowing yet more +calmly, drops upon its bed all such coarser gravel as is not worn away +to fine earth, but still bears on the lighter grains of sand. Next the +slackening speed makes even the sand too heavy a weight, and that in +turn falls to line the river-bed, while the now broad and placid +stream carries only the finer particles of mud suspended in its +waters. Soon it reaches the ocean, and the flow being there checked by +the incoming ocean-tide, even the mud can no longer be held up, and it +also sinks slowly in the shallows near the shore, forming sometimes +broad mud-banks dangerous to the mariner. + +This is the case only with smaller rivers. Where the stream is +stronger, the mud-banks are often formed much farther out at sea; and +more often still the river-detritus is carried away and shed over the +ocean-bed, beyond the reach of our ken. The powerful rush of water in +earth's greater streams bears enormous masses of sand and mud each +year far out into the ocean, there dropping quietly the gravel, sand, +and earth, layer upon layer at the bottom of the sea. Thus pulling +down and building up go on ever side by side; and while land is the +theatre oftentimes of decay and loss, ocean is the theatre oftentimes +of renewal and gain. + + +Did you notice the word "sediment" used a few pages back about the +settlement at the bottom of a medicine-vial? + +There is a second name given to the Stratified Rocks, of which the +earth's crust is so largely made up. They are called also _Sedimentary +Rocks_. + +The reason is simply this. The Stratified Rocks of the present day +were once upon a time made up out of the sediment stolen first from +land and then allowed to settle down on the sea-bottom. + +Long, long ago, the rivers, the streams, the ocean, were at work, as +they are now, carrying away rock and gravel, sand and earth. Then, as +now, all this material, borne upon the rivers, washed to and fro by +the ocean, settled down at the mouths of rivers or at the bottom of +the sea, into a sediment, one layer forming over another, gradually +built up through long ages. At first it was only a soft, loose, sandy +or muddy sediment, such as you may see on the seashore, or in a +mud-bank. But as the thickness of the sediment increased, the weight +of the layers above gradually pressed the lower layers into firm hard +rocks; and still, as the work of building went on, these layers were, +in their turn, made solid by the increasing weight over them. Certain +chemical changes had also a share in the transformation from soft mud +to hard rock, which need not be here considered. + +All this has through thousands of years been going on. The land is +perpetually crumbling away; and fresh land under the sea is being +perpetually built up, from the very same materials which the sea and +the rivers have so mercilessly stolen from continents and islands. +This is the way, if geologists rightly judge, in which a very large +part of the enormous formations of Stratified or Sedimentary Rocks +have been made. + +[Illustration: VIEW IN A CANON.] + +So far is clear. But now we come to a difficulty. + +The Stratified Rocks, of which a very large part of the continents is +made, appear to have been built up slowly, layer upon layer, out of +the gravel, sand, and mud, washed away from the land and dropped on +the shore of the ocean. + +[Illustration: SEA CLIFFS SHOWING A SERIES OF STRATIFIED ROCKS.] + +You may see these layers for yourself as you walk out into the +country. Look at the first piece of bluff rock you come near, and +observe the clear pencil-like markings of layer above layer--not often +indeed lying _flat_, one over another, and this must be explained +later, but however irregularly slanting, still plainly visible. You +can examine these lines of stratification on the nearest cliff, the +nearest quarry, the nearest bare headland, in your neighborhood. + +But how can this be? If all these stratified rocks are built on the +floor of the ocean out of material taken _from_ the land, how can we +by any possibility find such rocks _upon_ the land? In the beds of +rivers we might indeed expect to see them, but surely nowhere else +save under ocean waters. + +Yet find them we do. Through England, through the two great +world-continents, they abound on every side. Thousands of miles in +unbroken succession are composed of such rocks. + +Stand with me near the seashore, and let us look around. Those white +chalk cliffs--they, at least, are not formed of sand or earth. True, +and the lines of stratification are in them very indistinct, if seen +at all; yet they too are built up of sediment of a different kind, +dropping upon ocean's floor. See, however, in the rough sides of +yonder bluff the markings spoken of, fine lines running alongside of +one another, sometimes flat, sometimes bent or slanting, but always +giving the impression of layer piled upon layer. Yet how can one for a +moment suppose that the ocean-waters ever rose so high? + +Stay a moment. Look again at yonder white chalk cliff, and observe a +little way below the top a singular band of shingles, squeezed into +the cliff, as it were, with chalk below and earth above. + +That is believed to be an old sea-beach. Once upon a time the waters +of the sea are supposed to have washed those shingles, as now they +wash the shore near which we stand, and all the white cliff must have +lain then beneath the ocean. + +Geologists were for a long while sorely puzzled to account for these +old sea-beaches, found high up in the cliffs around our land in many +different places. + +They had at first a theory that the sea must once, in far back ages, +have been a great deal higher than it is now. But this explanation +only brought about fresh difficulties. It is quite impossible that the +level of the sea should be higher in one part of the world than in +another. If the sea around England were then one or two hundred feet +higher than it is now, it must have been one or two hundred feet +higher in every part of the world where the ocean-waters have free +flow. One is rather puzzled to know where all the water could have +come from, for such a tremendous additional amount. Besides, in some +places remains of sea-animals are found in mountain heights, as much +as two or three thousand feet above the sea-level--as, for instance, +in Corsica. This very much increases the difficulty of the above +explanation. + +So another theory was started instead, and this is now generally +supposed to be the true one. What if instead of the whole ocean having +been higher, parts of the land were lower? England at one time, parts +of Europe at another time, parts of Asia and America at other times, +may have slowly sunk beneath the ocean, and after long remaining there +have slowly risen again. + +This is by no means so wild a supposition as it may seem when first +heard, and as it doubtless did seem when first proposed. For even in +the present day these movements of the solid crust of our earth are +going on. The coasts of Sweden and Finland have long been slowly and +steadily rising out of the sea, so that the waves can no longer reach +so high upon those shores as in years gone by they used to reach. In +Greenland, on the contrary, land has long been slowly and steadily +sinking, so that what used to be the shore now lies under the sea. +Other such risings and sinkings might be mentioned, as also many more +in connection with volcanoes and earthquakes, which are neither slow +nor steady, but sudden and violent. + +So it becomes no impossible matter to believe that, in the course of +ages past, all those wide reaches of our continents and islands, where +sedimentary rocks are to be found, were each in turn, at one time or +another, during long periods, beneath the rolling waters of the +ocean.... + + * * * * * + +These built-up rocks are not only called "Stratified," and +"Sedimentary." They have also the name of _Aqueous Rock_, from the +Latin word _aqua, water_; because they are believed to have been +formed by the action of the water. + +They have yet another and fourth title, which is, _Fossiliferous +Rocks_. + +Fossils are the hardened remains of animals and vegetables found in +rocks. They are rarely, if ever, seen in unstratified rocks; but many +layers of stratified rocks abound in these remains. Whole skeletons as +well as single bones, whole tree-trunks as well as single leaves, are +found thus embedded in rock-layers, where in ages past the animal or +plant died and found a grave. They exist by thousands in many parts of +the world, varying in size from the huge skeleton of the elephant to +the tiny shell of the microscopic animalcule. + +[Illustration: FOSSIL OF CARBONIFEROUS FERN.] + +Fossils differ greatly in kind. Sometimes the entire shell or bone is +changed into stone, losing all its animal substance, but retaining its +old outline and its natural markings. Sometimes the fossil is merely +the hardened impress of the outside of a shell or leaf, which has +dented its picture on soft clay, and has itself disappeared, while the +soft clay has become rock, and the indented picture remains fixed +through after-centuries. Sometimes the fossil is the cast of the +inside of a shell; the said shell having been filled with soft mud, +which has taken its exact shape and hardened, while the shell itself +has vanished. The most complete description of fossil is the first of +these three kinds. It is wonderfully shown sometimes in fossil wood, +where all the tiny cells and delicate fibres remain distinctly marked +as of old, only the whole woody substance has changed into hard stone. + +[Illustration: FOOTPRINTS FROM TRIASSIC SANDSTONE OF CONNECTICUT.] + +But although the fossil remains of quadrupeds and other land-animals +are found in large quantities, their number is small compared with the +enormous number of fossil sea-shells and sea-animals. + +[Illustration: FOSSIL FOOTPRINTS.] + +Land-animals can, as a rule, have been so preserved, only when they +have been drowned in ponds or rivers, or mired in bogs and swamps, or +overtaken by frost, or swept out to sea. + +Sea-animals, on the contrary, have been so preserved on land whenever +that land has been under the sea; and this appears to have been the +case, at one or another past age, with the greater part of our +present continents. These fossil remains of sea-animals are +discovered in all quarters of the world, not only on the seashore but +also far inland, not only deep down underground but also high up on +the tops of lofty mountains--a plain proof that over the summits of +those mountains the ocean must once have rolled, and this not for a +brief space only, but through long periods of time. And not on the +mountain-summit only are these fossils known to abound, but sometimes +in layer below layer of the mountain, from top to bottom, through +thousands of feet of rock. + +[Illustration: FOSSIL SHELLS.] + +This may well seem puzzling at first sight. Fossils of sea-creatures +on a mountain-top are startling enough; yet hardly so startling as the +thought of fossils _inside_ that mountain. How could they have found +their way thither? + +The difficulty soon vanishes, if once we clearly understand that all +these thousands of feet of rock were built up slowly, layer after +layer, when portions of the land lay deep under the sea. Thus _each +separate layer_ of mud or sand or other material became in its turn +the _top layer_, and was for the time the floor of the ocean, until +further droppings of material out of the waters made a fresh layer, +covering up the one below. + +While each layer was thus in succession the top layer of the building, +and at the same time the floor of the ocean, animals lived and died +in the ocean, and their remains sank to the bottom, resting upon the +sediment floor. Thousands of such dead remains disappeared, crumbling +into fine dust and mingling with the waters, but here and there one +was caught captive by the half-liquid mud, and was quickly covered and +preserved from decay. And still the building went on, and still layer +after layer was placed, till many fossils lay deep down beneath the +later-formed layers; and when at length, by slow or quick upheaval of +the ground, this sea-bottom became a mountain, the little fossils were +buried within the body of that mountain. So wondrously the matter +appears to have come about. + + * * * * * + +Another difficulty with respect to the stratified rocks has to be +thought of. All these layers or deposits of gravel, sand, or earth, on +the floor of the ocean, would naturally be horizontal--that is, would +lie flat, one upon another. In places the ocean-floor might slant, or +a crevice or valley or ridge might break the smoothness of the +deposit. But though the layers might partake of the slant, though the +valley might have to be filled, though the ridge might have to be +surmounted, still the general tendency of the waves would be to level +the dropping deposits into flat layers. + +Then how is it that when we examine the strata of rocks in our +neighborhood, wherever that neighborhood may be, we do not find them +so arranged? Here, it is true, the lines for a space are nearly +horizontal, but there, a little way farther on, they are +perpendicular; here they are bent, and there curved; here they are +slanting, and there crushed and broken. + +This only bears out what has been already said about the Book of +Geology. It _has_ been bent and disturbed, crushed and broken. + +Great powers have been at work in this crust of our earth. Continents +have been raised, mountains have been upheaved, vast masses of rock +have been scattered into fragments. Here or there we may find the +layers arranged as they were first laid down; but far more often we +discover signs of later disturbance, either slow or sudden, varying +from a mere quiet tilting to a violent overturn. + +[Illustration: EXAMPLE OF DISTURBANCE OF THE EARTH'S LAYERS.] + +So the Book of Geology is a torn and disorganized volume, not easy to +read. + +Yet, on the other hand, these very changes which have taken place are +a help to the geologist. + +It may seem at first sight as if we should have an easier task, if the +strata were all left lying just as they were first formed, in smooth +level layers, one above another. But if it were so, we could know very +little about the lower layers. + +We might indeed feel sure, as we do now, that the lowest layers were +the oldest and the top layers the newest, and that any fossils found +in the lower layers must belong to an age farther back than any +fossils found in the upper layers. + +So much would be clear. And we might dig also and burrow a little way +down, through a few different kinds of rock, where they were not too +thick. But that would be all. There our powers would cease. + +Now how different. Through the heavings and tiltings of the earth's +crust, the lower layers are often pushed quite up to the surface, so +that we are able to examine them and their fossils without the least +difficulty, and very often without digging underground at all. + +You must not suppose that the real order of the rocks is changed by +these movements, for generally speaking it is not. The lower kinds are +rarely if ever found placed _over_ the upper kinds; only the ends of +them are seen peeping out above ground. + +It is as if you had a pile of copy-books lying flat one upon another, +and were to put your finger under the lowest and push it up. All those +above would be pushed up also, and perhaps they would slip a little +way down, so that you would have a row of _edges_ showing side by +side, at very much the same height. The arrangement of the copy-books +would not be changed, for the lowest would still be the lowest in +actual position; but a general tilting or upheaval would have taken +place. + +Just such a tilting or upheaval has taken place again and again with +the rocks forming our earth-crust. The edges of the lower rocks often +show side by side with those of higher layers. + +But geologists know them apart. They are able to tell confidently +whether such and such a rock, peeping out at the earth's surface, +belongs really to a lower or a higher kind. For there is a certain +sort of order followed in the arrangement of rock-layers all over the +earth, and it is well known that some rocks are never found below some +other rocks, that certain particular kinds are never placed above +certain other kinds. Thus it follows that the fossils found in one +description of rock, must be the fossils of animals which lived and +died before the animals whose fossil remains are found in another +neighboring rock, just because this last rock-layer was built upon the +ocean-floor above and therefore later than the other. + +All this is part of the foreign language of geology--part of the +piecing and arranging of the torn volume. Many mistakes are made; many +blunders are possible; but the mistakes and blunders are being +gradually corrected, and certain rules by which to read and understand +are becoming more and more clear. + +It has been already said that unstratified rocks are those which have +been at some period, whether lately or very long ago, in a liquid +state from intense heat, and which have since cooled, either quickly +or slowly, crystallizing as they cooled. + +Unstratified Rocks may be divided into two distinct classes. + +[Illustration: SECTION OF A LAVA BOMB.] + +First.--Volcanic Rocks, such as lava. These have been quickly cooled +at the surface of the earth, or not far below it. + +Secondly.--Plutonic Rocks, such as granite. These have been slowly +cooled deep down in the earth under heavy pressure. + +There is also a class of rocks, called metamorphic rocks, including +some kinds of marble. These are, strictly speaking, crystalline rocks, +and yet they are arranged in something like layers. The word +"metamorphic" simply means "transformed." They are believed to have +been once stratified rocks, perhaps containing often the remains of +animals; but intense heat has later transformed them into crystalline +rocks, and the animal remains have almost or quite vanished. + +[Illustration: LAVA-STREAM ON VESUVIUS.] + +Just as the different kinds of Stratified Rocks are often called +Aqueous Rocks, or rocks formed by the action of water--so these +different kinds of Unstratified Rocks are often called Igneous Rocks, +or rocks formed by the action of fire--the name being taken from the +Latin word for fire. The Metamorphic Rocks are sometimes described as +"Aqueo-igneous," since both water and fire helped in the forming of +them. + +It was at one time believed, as a matter of certainty, that granite +and such rocks belonged to a period much farther back than the periods +of the stratified rocks. That is to say, it was supposed that +fire-action had come first and water-action second; that the fire-made +rocks were all formed in very early ages, and that only water-made +rocks still continued to be formed. So the name of Primary Rocks, or +First Rocks, was given to the granites and other such rocks, and the +name of Secondary Rocks to all water-built rocks; while those of the +third class were called Transition Rocks, because they seemed to be a +kind of link or stepping-stone in the change from the First to the +Second Rocks. + +The chief reason for the general belief that fire-built rocks were +older than water-built ones was, that the former are as a rule found +to lie _lower_ than the latter. They form, as it were, the basement of +the building, while the top-stories are made of water-built rocks. + +Many still believe that there is much truth in the thought. It is most +probable, so far as we are able to judge, that the _first-formed_ +crust of rocks all over the earth was of cooled and crystallized +material. As these rocks were crumbled and wasted by the ocean, +materials would have been supplied for the building-up of rocks, layer +upon layer. + +But this is conjecture. We cannot know with any certainty the course +of events so far back in the past. And geologists are now able to +state with tolerable confidence that, however old many of the granites +may be, yet a large amount of the fire-built rocks are no older than +the water-built rocks which lie over them. + +So by many geologists the names of Primary, Transition, and Secondary +Formations are pretty well given up. It has been proposed to give +instead to the crystallized rocks of all kinds the name of Underlying +Rocks (Hypogene Rocks). + +But if they really do lie under, how can they possibly be of the same +age? One would scarcely venture to suppose, in looking at a building, +that the cellars had not been finished before the upper floors. + +True. In the first instance doubtless the cellars were first made, +then the ground-floor, then the upper stories. + +When, however, the house was so built, alterations and improvements +might be very widely carried on above and below. While one set of +workmen were engaged in remodelling the roof, another set of workmen +might be engaged in remodelling the kitchens and first floor, pulling +down, propping up, and actually rebuilding parts of the lower walls. + +This is precisely what the two great fellow-workmen, Fire and Water, +are ever doing in the crust of our earth. And if it be objected that +such alterations too widely undertaken might result in slips, cracks, +and slidings, of ceilings and walls in the upper stories, I can only +say that such catastrophes _have_ been the result of underground +alterations in that great building, the earth's crust.... + +We see therefore clearly that, although the earliest fire-made rocks +may very likely date farther back than the earliest water-made rocks, +yet the making of the two kinds has gone on side by side, one below +and the other above ground, through all ages up to the present moment. + +And just as in the present day water continues its busy work above +ground of pulling down and building up, so also fire continues its +busy work underground of melting rocks which afterwards cool into new +forms, and also of shattering and upheaving parts of the earth-crust. + +For there can be no doubt that fiery heat does exist as a mighty power +within our earth, though to what extent we are not able to say. + +These two fellow-workers in nature have different modes of working. +One we can see on all sides, quietly progressing, demolishing land +patiently bit by bit, building up land steadily grain by grain. The +other, though more commonly hidden from sight, is fierce and +tumultuous in character, and shows his power in occasional terrific +outbursts. + +We can scarcely realize what the power is of the imprisoned fiery +forces underground, though even we are not without some witness of +their existence. From time to time even our firm land has been felt to +tremble with a thrill from some far-off shock; and even in our country +is seen the marvel of scalding water pouring unceasingly from deep +underground.... + +Think of the tremendous eruptions of Vesuvius, of Etna, of Hecla, of +Mauna Loa. Think of whole towns crushed and buried, with their +thousands of living inhabitants. Think of rivers of glowing lava +streaming up from regions below ground, and pouring along the surface +for a distance of forty, fifty, and even sixty miles, as in Iceland +and Hawaii. Think of red-hot cinders flung from a volcano-crater to a +height of ten thousand feet. Think of lakes of liquid fire in other +craters, five hundred to a thousand feet across, huge cauldrons of +boiling rock. Think of showers of ashes from the furnace below of yet +another, borne so high aloft as to be carried seven hundred miles +before they sank to earth again. Think of millions of red-hot stones +flung out in one eruption of Vesuvius. Think of a mass of rock, one +hundred cubic yards in size, hurled to a distance of eight miles or +more out of the crater of Cotopaxi. + +[Illustration: HOT WELLS.] + +Think also of earthquake-shocks felt through twelve hundred miles of +country. Think of fierce tremblings and heavings lasting in constant +succession through days and weeks of terror. Think of hundreds of +miles of land raised several feet in one great upheaval. Think of the +earth opening in scores of wide-lipped cracks, to swallow men and +beasts. Think of hot mud, boiling water, scalding stream, liquid rock, +bursting from such cracks, or pouring from rents in a mountain-side. + +Truly these are signs of a state of things in or below the solid crust +on which we live, that may make us doubt the absolute security of +"Mother Earth." + +Different explanations have been put forward to explain this seemingly +fiery state of things underground. + +Until lately the belief was widely held that our earth was one huge +globe of liquid fire, with only a slender cooled crust covering her, a +few miles in thickness. + +This view was supported by the fact that heat is found to increase as +men descend into the earth. Measurements of such heat-increase have +been taken, both in mines and in borings for wells. The usual rate is +about one degree more of heat, of our common thermometer, for every +fifty or sixty feet of descent. If this were steadily continued, water +would boil at a depth of eight thousand feet below the surface; iron +would melt at a depth of twenty-eight miles; while at a depth of forty +or fifty miles no known substance upon earth could remain solid. + +The force of this proof is, however, weakened by the fact that the +rate at which the heat increases differs very much in different +places. Also it is now generally supposed that such a tremendous +furnace of heat--a furnace nearly eight thousand miles in +diameter--could not fail to break up and melt so slight a covering +shell. + +Many believe, therefore, not that the whole interior of the earth is +liquid with heat, but that enormous fire-seas or lakes of melted rock +exist here and there, under or in the earth-crust. From these lakes +the volcanoes would be fed, and they would be the cause of earthquakes +and land-upheavals or land-sinkings. There are strong reasons for +supposing that the earth was once a fiery liquid body, and that she +has slowly cooled through long ages. Some hold that her centre +probably grew solid first from tremendous pressure; that her crust +afterwards became gradually cold; and that between the solid crust and +the solid inside or "nucleus," a sea of melted rock long existed, the +remains of which are still to be found in these tremendous fiery +reservoirs. + +The idea accords well with the fact that large numbers of extinct or +dead volcanoes are scattered through many parts of the earth. If the +above explanation be the right one, doubtless the fire-seas in the +crust extended once upon a time beneath such volcanoes, but have since +died out or smouldered low in those parts. + +A somewhat curious calculation has been made, to illustrate the +different modes of working of these two mighty powers--Fire and Water. + +The amount of land swept away each year in mud, and borne to the ocean +by the River Ganges, was roughly reckoned, and also the amount of land +believed to have been upheaved several feet in the great Chilian +earthquake. + +It was found that the river, steadily working month by month, would +require some four hundred years to carry to the sea the same weight of +material, which in one tremendous effort was upheaved by the fiery +underground forces. + +Yet we must not carry this distinction too far. Fire does not always +work suddenly, or water slowly; witness the slow rising and sinking of +land in parts of the earth, continuing through centuries; and witness +also the effects of great floods and storms. + +The crust of the earth is made of rock. But what is rock made of? + +Certain leading divisions of rocks have been already considered: + +The Water-made Rocks; + +The Fire-made Rocks, both Plutonic and Volcanic; + +The Water-and-Fire-made Rocks. + +The first of these--Water-made Rocks--may be subdivided into three +classes. These are,-- + +I. _Flint Rocks_; II. _Clay Rocks_; III. _Lime Rocks_. + +This is not a book in which it would be wise to go closely into the +mineral nature of rocks. Two or three leading thoughts may, however, +be given. + +Does it not seem strange that the hard and solid rocks should be in +great measure formed of the same substances which form the thin +invisible air floating around us? + +Yet so it is. There is a certain gas called Oxygen Gas. Without that +gas you could not live many minutes. Banish it from the room in which +you are sitting, and in a few minutes you will die. + +This gas makes up nearly one-quarter by weight of the atmosphere round +the whole earth. + +The same gas plays an important part in the ocean; for more than +three-quarters of water is _oxygen_. + +It plays also an important part in rocks; for about half the material +of the entire earth's crust is oxygen. + +Another chief material in rocks is _silicon_. This makes up +one-quarter of the crust, leaving only one-quarter to be accounted +for. Silicon mixed with oxygen makes silica or quartz. There are few +rocks which have not a large amount of quartz in them. Common flint, +sandstones, and the sand of our shores, are made of quartz, and +therefore belong to the first class of Silicious or Flint Rocks. +Granites and lavas are about one-half quartz. The beautiful stones, +amethyst, agate, chalcedony, and jasper, are all different kinds of +quartz. + +Another chief material in rocks is a white metal called _aluminium_. +United to oxygen it becomes alumina, the chief substance in clay. +Rocks of this kind--such as clays, and also the lovely blue gem, +sapphire--are called Argillaceous Rocks, from the Latin word for clay, +and belong to the second class. Such rocks keep fossils well. + +Another is _calcium_. United to oxygen and carbonic acid, it makes +carbonate of lime, the chief substance in limestone; so all limestones +belong to the third class of Calcareous or Lime Rocks. + +Other important materials may be mentioned, such as _magnesium, +potassium, sodium, iron, carbon, sulphur, hydrogen, chlorine, +nitrogen_. These, with many more, not so common, make up the remaining +quarter of the earth-crust. + +Carbon plays as important a part in animal and vegetable life as +silicon in rocks. Carbon is most commonly seen in three distinct +forms--as charcoal, as black-lead, and as the pure brilliant diamond. +Carbon united, in a particular proportion, to oxygen, forms carbonic +acid; and carbonic acid united, in a particular proportion, to lime, +forms limestone. + +_Hydrogen_ united to oxygen forms water. Each of these two gases is +invisible alone, but when they meet and mingle they form a liquid. + +_Nitrogen_ united to oxygen and to a small quantity of carbonic acid +gas forms our atmosphere. + +Rocks of pure flint, pure clay, or pure lime, are rarely or never met +with. Most rocks are made up of several different substances melted +together. + + * * * * * + +In the fire-built rocks no remains of animals are found, though in +water-built rocks they abound. Water-built rocks are sometimes divided +into two classes--those which only contain occasional animal remains, +and those which are more or less built up of the skeletons of animals. + +[Illustration: AMIBA PRINCEPS, ONE OF THE MANY ORDERS OF THE RHIZOPODA +CLASS, MAGNIFIED ONE HUNDRED TIMES.] + +There are some exceedingly tiny creatures inhabiting the ocean, called +Rhizopods. They live in minute shells, the largest of which may be +almost the size of a grain of wheat, but by far the greater number are +invisible as shells without a microscope, and merely show as fine +dust. The rhizopods are of different shapes, sometimes round, +sometimes spiral, sometimes having only one cell, sometimes having +several cells. In the latter case a separate animal lives in each +cell. The animal is of the very simplest as well as the smallest kind. +He has not even a mouth or a stomach but can take in food at any part +of his body. + +[Illustration: RHIZOPODS (MAGNIFIED).] + +These rhizopods live in the oceans in enormous numbers. Tens of +millions are ever coming into existence, living out their tiny lives, +dying, and sinking to the bottom. + +There upon the ocean-floor gather their remains, a heaped-up multitude +of minute skeletons or shells, layer forming over layer. + +It was long suspected that the white chalk cliffs of England were +built up in some such manner as this through past ages. And now at +length proof has been found, in the shape of mud dredged up from the +ocean-bottom--mud entirely composed of countless multitudes of these +little shells, dropping there by myriads, and becoming slowly joined +together in one mass. + +Just so, it is believed, were the white chalk cliffs built--gradually +prepared on the ocean-floor, and then slowly or suddenly upheaved, so +as to become a part of the dry land. + +Think what the enormous numbers must have been of tiny living +creatures, out of whose shells the wide reaches of white chalk cliffs +have been made. Chalk cliffs and chalk layers extend from Ireland, +through England and France, as far as to the Crimea. In the south of +Russia they are said to be six hundred feet thick. Yet one cubic inch +of chalk is calculated to hold the remains of more than one million +rhizopods. How many countless millions upon millions must have gone to +the whole structure! How long must the work of building up have +lasted! + +[Illustration: THREE POLYPS OF CORAL.] + +These little shells do not always drop softly and evenly to the +ocean-floor, to become quietly part of a mass of shells. Sometimes, +where the ocean is shallow enough for the waves to have power below, +or where land currents can reach, they are washed about, and thrown +one against another, and ground into fine powder; and the fine powder +becomes in time, through different causes, solid rock. + +[Illustration: CORAL POLYP.] + +Limestone is made in another way also. In the warm waters of the South +Pacific Ocean there are many islands, large and small, which have +been formed in a wonderful manner by tiny living workers. The workers +are soft jelly-like creatures, called polyps, who labor together in +building up great walls and masses of coral. + +[Illustration: CORAL ISLAND.] + +[Illustration: YOUNG CORAL POLYP ATTACHED TO A ROCK AND EXPANDED.] + +They never carry on their work above the surface of the water, for in +the air they would die. But the waves break the coral, and heap it up +above high-water mark, and carry earth and seeds to drop there till at +length a small low-lying island is formed. + +The waves not only heap up broken coral, but they grind the coral into +fine powder, and from this powder limestone rock is made, just as it +is from the powdered shells of rhizopods. The material used by the +polyps in building the coral is chiefly lime, which they have the +power of gathering out of the water, and the fine coral-powder, +sinking to the bottom, makes large quantities of hard limestone. Soft +chalk is rarely, if ever, found near the coral islands. + +[Illustration: 1. WHITE CORAL. 2. PORTION OF A BRANCH (MAGNIFIED).] + +Limestones are formed in the same manner from the grinding up of other +sea-shells and fossils, various in kind; the powder becoming gradually +united into solid rock. + +There is yet another way in which limestone is made, quite different +from all these. Sometimes streams of water have a large quantity of +lime in them; and these as they flow will drop layers of lime which +harden into rock. Or a lime-laden spring, making its way through the +roof of an underground cavern, will leave all kinds of fantastic +arrangements of limestone wherever its waters can trickle and drip. +Such a cavern is called a "stalactite cave." + + * * * * * + +So there are different kinds of fossil rock-making. There may be rocks +made of other materials, with fossil simply buried in them. There may +be rocks made entirely of fossils, which have gathered in masses as +they sank to the sea-bottom, and have there become simply and lightly +joined together. There may be rocks made of the ground-up powder of +fossils, pressed into a solid substance or united by some other +substance. + +Rocks are also often formed of whole fossils, or stones, or shells, +bound into one by some natural soft sticky cement, which has gathered +round them and afterwards grown hard, like the cement which holds +together the stones in a wall. + +The tiny rhizopods (meaning root foot) which have so large a share in +chalk and limestone making, are among the smallest and simplest known +kinds of animal life. + +There are also some very minute forms of vegetable life, which exist +in equally vast numbers, called Diatoms. For a long while they were +believed to be living animals, like the rhizopods. Scientific men are +now, however, pretty well agreed that they really are only vegetables +or plants. + +The diatoms have each one a tiny shell or shield, not made of lime +like the rhizopod-shells, but of flint. Some think that common flint +may be formed of these tiny shells. + +Again, there is a kind of rock called Mountain Meal, which is entirely +made up of the remains of diatoms. Examined under the microscope, +thousands of minute flint shields of various shapes are seen. This +rock, or earth, is very abundant in many places, and is sometimes used +as a polishing powder. In Bohemia there is a layer of it no less than +fourteen feet thick. Yet so minute are the shells of which it is +composed, that one square inch of rock is said to contain about four +thousand millions of them. Each one of these millions is a separate +distinct fossil.... + + * * * * * + +[Illustration: SUCCESSION OF BURIED COAL-GROWTHS AND ERECT +TREE-STUMPS. SYDNEY, CAPE BRETON. + +_a._ Sandstone, _b._ Shales, _c._ Coal-seams, _d._ Bed containing +Roots and Stumps _in situ_.] + +If you examine carefully a piece of coal, you will find, more or less +clearly, markings like those which are seen in a piece of wood. +Sometimes they are very distinct indeed. Coal abounds in impressions +of leaves, ferns, and stems, and fossil remains of plants and +tree-trunks are found in numbers in coal-seams. + +Coal is a vegetable substance. The wide coal-fields of Britain and +other lands are the _fossil_ remains of vast forests. + +Long ages ago, as it seems, broad and luxuriant forests flourished +over the earth. In many parts generation after generation of trees +lived and died and decayed, leaving no trace of their existence, +beyond a little layer of black mould, soon to be carried away by wind +and water. Coal could only be formed where there were bogs and +quagmires. + +But in bogs and quagmires, and in shallow lakes of low-lying lands, +there were great gatherings of slowly-decaying vegetable remains, +trees, plants, and ferns all mingling together. Then after a while the +low lands would sink and the ocean pouring in would cover them with +layers of protecting sand or mud; and sometimes the land would rise +again, and fresh forests would spring into life, only to be in their +turn overwhelmed anew, and covered by fresh sandy or earthy deposits. + +These buried forests lay through the ages following, slowly hardening +into the black and shining coal, so useful now to man. + +The coal is found thus in thin or thick seams, with other rock-layers +between, telling each its history of centuries long past. In one place +no less than sixteen such beds of coal are found, one below another, +each divided from the next above and the next underneath by beds of +clay or sand or shale. The forests could not have grown in the sea, +and the earth-layers could not have been formed on land, therefore +many land-risings and sinkings must have taken place. Each bed +probably tells the tale of a succession of forests.... + + * * * * * + +Before going on to a sketch of the early ages of the Earth's +history--ages stretching back long long before the time of Adam--it is +needful to think yet for a little longer about the manner in which +that history is written, and the way in which it has to be read. + +For the record is one difficult to make out, and its style of +expression is often dark and mysterious. There is scarcely any other +volume in the great Book of Nature, which the student is so likely to +misread as this one. It is very needful, therefore, to hold the +conclusions of geologists with a light grasp, guarding each with a +"perhaps" or a "may be." Many an imposing edifice has been built, in +geology, upon a rickety foundation which has speedily given way. + +In all ages of the world's history up to the present day, rock-making +has taken place--fire-made rocks being fashioned underground, and +water-made rocks being fashioned above ground though under water. + +Also in all ages different kinds of rocks have been fashioned side by +side--limestone in one part of the world, sandstone in another, chalk +in another, clay in another, and so on. There have, it is true, been +ages when one kind seems to have been the _chief_ kind--an age of +limestone, or an age of chalk. But even then there were doubtless more +rock-buildings going on, though not to so great an extent. On the +other hand, there may have been ages during which no limestone was +made, or no chalk, or no clay. As a general rule, however, the various +sorts of rock-building have probably gone on together. This was not so +well understood by early geologists as it is now. + +The difficulty is often great of disentangling the different strata, +and saying which was earlier and which later formed. + +Still, by close and careful study of the rocks which compose the +earth's crust, a certain kind of order is found to exist, more or less +followed out in all parts of the world. _When_ each layer was formed +in England or in America, the geologist cannot possibly say. He can, +however, assert, in either place, that a certain mass of rock was +formed before a certain other mass in that same place, even though +the two may seem to lie side by side; for he knows that they were so +placed only by upheaval, and that once upon a time the one lay beneath +the other. + +The geologist can go further. He can often declare that a certain mass +of rock in America and a certain mass of rock in England, quite +different in kind, were probably built up at about the same time. How +long ago that time was he would be rash to attempt to say; but that +the two belong to the same age he has good reason for supposing. + +We find rocks piled upon rocks in a certain order, so that we may +generally be pretty confident that the lower rocks were first made, +and the upper rocks the latest built. Further than this, we find in +all the said layers of water-built rocks signs of past life. + +As already stated, much of this life was ocean-life, though not all. + +Below the sea, as the rock-layers were being formed, bit by bit, of +earth dropping from the ocean to the ocean's floor, sea-creatures +lived out their lives and died by thousands, to sink to that same +floor. Millions passed away, dissolving and leaving no trace behind; +but thousands were preserved--shells often, animals sometimes. + +Nor was this all. For now and again some part of the sea-bottom was +upheaved, slowly or quickly, till it became dry land. On this dry land +animals lived again, and thousands of them, too, died, and their bones +crumbled into dust. But here and there one was caught in bog or frost, +and his remains were preserved till, through lapse of ages, they +turned to stone. + +Yet again that land would sink, and over it fresh layers were formed +by the ocean-waters, with fresh remains of sea-animals buried in with +the layers of sand or lime; and once more the sea-bottom would rise, +perhaps then to continue as dry land, until the day when man should +discover and handle these hidden remains. + +Now note a remarkable fact as to these fossils, scattered far and wide +through the layers of stratified rock. + +In the uppermost and latest built rocks the animals found are the +same, in great measure, as those which now exist upon the earth. + +Leaving the uppermost rocks, and examining those which lie a little +way below, we find a difference. Some are still the same, and others, +if not quite the same, are very much like what we have now; but here +and there a creature of a different form appears. + +Go deeper still, and the kinds of animals change further. Fewer and +fewer resemble those which now range the earth; more and more belong +to other species. + +Descend through layer after layer till we come to rocks built in +earliest ages and not one fossil shall we find precisely the same as +one animal living now. + +So not only are the rocks built in successive order, stratum after +stratum belonging to age after age in the past, but fossil-remains +also are found in successive order, kind after kind belonging to past +age after age. + +Although in the first instance the succession of fossils was +understood by means of the succession of rock-layers, yet in the +second place the arrangement of rock-layers is made more clear by the +means of these very fossils. + +A geologist, looking at the rocks in America, can say which there were +first-formed, which second-formed, which third-formed. Also, looking +at the rocks in England, he can say which there were first-formed, +second-formed, third-formed. He would, however, find it very +difficult, if not impossible, to say which among any of the American +rocks was formed at about the same time as any particular one among +the English rocks, were it not for the help afforded him by these +fossils. + +Just as the regular succession of rock-strata has been gradually +learned, so the regular succession of different fossils is becoming +more and more understood. It is now known that some kinds of fossils +are always found in the oldest rocks, and in them only; that some +kinds are always found in the newest rocks, and in them only; that +some fossils are rarely or never found lower than certain layers; that +some fossils are rarely or never found higher than certain other +layers. + +So this fossil arrangement is growing into quite a history of the +past. And a geologist, looking at certain rocks, pushed up from +underground, in England and in America, can say: "These are very +different kinds of rocks, it is true, and it would be impossible to +say how long the building up of the one might have taken place before +or after the other. But I see that in both these rocks there are +exactly the same kinds of fossil-remains, differing from those in the +rocks above and below. I conclude therefore that the two rocks belong +to about the same great age in the world's past history, when the +same animals were living upon the earth." + +Observing and reasoning thus, geologists have drawn up a general plan +or order of strata; and the whole of the vast masses of water-built +rocks throughout the world have been arranged in a regular succession +of classes, rising step by step from earliest ages up to the present +time. + +[Illustration] + + + + +AMERICA THE OLD WORLD + +(FROM GEOLOGICAL SKETCHES.) + +BY L. AGASSIZ. + + +[Illustration] + +First-born among the Continents, though so much later in culture and +civilization than some of more recent birth, America, so far as her +physical history is concerned, has been falsely denominated the _New +World_. Hers was the first dry land lifted out of the waters, hers the +first shore washed by the ocean that enveloped all the earth beside; +and while Europe was represented only by islands rising here and there +above the sea, America already stretched an unbroken line of land from +Nova Scotia to the Far West. + +In the present state of our knowledge, our conclusions respecting the +beginning of the earth's history, the way in which it took form and +shape as a distinct, separate planet, must, of course, be very vague +and hypothetical. Yet the progress of science is so rapidly +reconstructing the past that we may hope to solve even this problem; +and to one who looks upon man's appearance upon the earth as the +crowning work in a succession of creative acts, all of which have had +relation to his coming in the end, it will not seem strange that he +should at last be allowed to understand a history which was but the +introduction to his own existence. It is my belief that not only the +future, but the past also, is the inheritance of man, and that we +shall yet conquer our lost birthright. + +Even now our knowledge carries us far enough to warrant the assertion +that there was a time when our earth was in a state of igneous fusion, +when no ocean bathed it and no atmosphere surrounded it, when no wind +blew over it and no rain fell upon it, but an intense heat held all +its materials in solution. In those days the rocks which are now the +very bones and sinews of our mother Earth--her granites, her +porphyries, her basalts, her syenites--were melted into a liquid mass. +As I am writing for the unscientific reader, who may not be familiar +with the facts through which these inferences have been reached, I +will answer here a question which, were we talking together, he might +naturally ask in a somewhat sceptical tone. How do you know that this +state of things ever existed, and, supposing that the solid materials +of which our earth consists were ever in a liquid condition, what +right have you to infer that this condition was caused by the action +of heat upon them? I answer, Because it is acting upon them still; +because the earth we tread is but a thin crust floating on a liquid +sea of molten materials; because the agencies that were at work then +are at work now, and the present is the logical sequence of the past. +From artesian wells, from mines, from geysers, from hot springs, a +mass of facts has been collected, proving incontestably the heated +condition of all substances at a certain depth below the earth's +surface; and if we need more positive evidence, we have it in the +fiery eruptions that even now bear fearful testimony to the molten +ocean seething within the globe and forcing its way but from time to +time. The modern progress of Geology has led us by successive and +perfectly connected steps back to a time when what is now only an +occasional and rare phenomenon was the normal condition of our earth; +when the internal fires were enclosed by an envelope so thin that it +opposed but little resistance to their frequent outbreak, and they +constantly forced themselves through this crust, pouring out melted +materials that subsequently cooled and consolidated on its surface. So +constant were these eruptions, and so slight was the resistance they +encountered, that some portions of the earlier rock-deposits are +perforated with numerous chimneys, narrow tunnels as it were, bored by +the liquid masses that poured out through them and greatly modified +their first condition. + +[Illustration: IDEAL SECTION OF A VOLCANO IN ACTION.] + +The question at once suggests itself, How was even this thin crust +formed? what should cause any solid envelope, however slight and filmy +when compared to the whole bulk of the globe, to form upon the surface +of such a liquid mass? At this point of the investigation the +geologist must appeal to the astronomer; for in this vague and +nebulous border-land, where the very rocks lose their outlines and +flow into each other, not yet specialized into definite forms and +substances,--there the two sciences meet. Astronomy shows us our +planet thrown off from the central mass of which it once formed a +part, to move henceforth in an independent orbit of its own. That +orbit, it tells us, passed through celestial spaces cold enough to +chill this heated globe, and of course to consolidate it externally. +We know, from the action of similar causes on a smaller scale and on +comparatively insignificant objects immediately about us, what must +have been the effect of this cooling process upon the heated mass of +the globe. All substances when heated occupy more space than they do +when cold. Water, which expands when freezing, is the only exception +to this rule. The first effect of cooling the surface of our planet +must have been to solidify it, and thus to form a film or crust over +it. That crust would shrink as the cooling process went on; in +consequence of the shrinking, wrinkles and folds would arise upon it, +and here and there, where the tension was too great, cracks and +fissures would be produced. In proportion as the surface cooled, the +masses within would be affected by the change of temperature +outside of them, and would consolidate internally also, the crust +gradually thickening by this process. + +[Illustration: A VOLCANO.] + +But there was another element without the globe, equally powerful in +building it up. Fire and water wrought together in this work, if not +always harmoniously, at least with equal force and persistency. I have +said that there was a time when no atmosphere surrounded the earth; +but one of the first results of the cooling of its crust must have +been the formation of an atmosphere, with all the phenomena connected +with it,--the rising of vapors, their condensation into clouds, the +falling of rains, the gathering of waters upon its surface. Water is a +very active agent of destruction, but it works over again the +materials it pulls down or wears away, and builds them up anew in +other forms. As soon as an ocean washed over the consolidated crust of +the globe, it would begin to abrade the surfaces upon which it moved, +gradually loosening and detaching materials, to deposit them again as +sand or mud or pebbles at its bottom in successive layers, one above +another. Thus, in analyzing the crust of the globe, we find at once +two kinds of rocks, the respective work of fire and water: the first +poured out from the furnaces within, and cooling, as one may see any +mass of metal cool that is poured out from a smelting-furnace to-day, +in solid crystalline masses, without any division into separate layers +or leaves; and the latter in successive beds, one over another, the +heavier materials below, the lighter above, or sometimes in alternate +layers, as special causes may have determined successive deposits of +lighter or heavier materials at some given spot. + +There were many well-fought battles between geologists before it was +understood that these two elements had been equally active in building +up the crust of the earth. The ground was hotly contested by the +disciples of the two geological schools, one of which held that the +solid envelope of the earth was exclusively due to the influence of +fire, while the other insisted that it had been accumulated wholly +under the agency of water. This difference of opinion grew up very +naturally; for the great leaders of the two schools lived in different +localities, and pursued their investigations over regions where the +geological phenomena were of an entirely opposite character,--the one +exhibiting the effect of volcanic eruptions, the other that of +stratified deposits. It was the old story of the two knights on +opposite sides of the shield, one swearing that it was made of gold, +the other that it was made of silver; and almost killing each other +before they discovered that it was made of both. So prone are men to +hug their theories and shut their eyes to any antagonistic facts, that +it is related of Werner, the great leader of the Aqueous school, that +he was actually on his way to see a geological locality of especial +interest, but, being told that it confirmed the views of his +opponents, he turned round and went home again, refusing to see what +might force him to change his opinions. If the rocks did not confirm +his theory, so much the worse for the rocks,--he would none of them. +At last it was found that the two great chemists, fire and water, had +worked together in the vast laboratory of the globe, and since then +scientific men have decided to work together also; and if they still +have a passage at arms occasionally over some doubtful point, yet the +results of their investigations are ever drawing them nearer to each +other,--since men who study truth, when they reach their goal, must +always meet at last on common ground. + +The rocks formed under the influence of heat are called, in geological +language, the Igneous, or, as some naturalists have named them, the +Plutonic rocks, alluding to their fiery origin, while the others have +been called Aqueous or Neptunic rocks, in reference to their origin +under the agency of water. A simpler term, however, quite as +distinctive, and more descriptive of their structure, is that of the +stratified and massive or unstratified rocks. We shall see hereafter +how the relative position of these two classes of rocks and their +action upon each other enable us to determine the chronology of the +earth, to compare the age of her mountains, and, if we have no +standard by which to estimate the positive duration of her continents, +to say at least which was the first-born among them, and how their +characteristic features have been successfully worked out. I am aware +that many of these inferences, drawn from what is called "the +geological record," must seem to be the work of the imagination. In a +certain sense this is true,--for imagination, chastened by correct +observation, is our best guide in the study of Nature. We are too apt +to associate the exercise of this faculty with works of fiction, while +it is in fact the keenest detective of truth. + +[Illustration: DIKES.] + +Besides the stratified and massive rocks, there is still a third set, +produced by the contact of these two, and called, in consequence of +the changes thus brought about, the Metamorphic rocks. The effect of +heat upon clay is to bake it into slate; limestone under the influence +of heat becomes quick-lime, or, if subjected afterwards to the action +of water, it is changed to mortar; sand under the same agency is +changed to a coarse kind of glass. Suppose, then, that a volcanic +eruption takes place in a region of the earth's surface where +successive layers of limestone, of clay, and of sandstone, have been +previously deposited by the action of water. If such an eruption has +force enough to break through these beds, the hot, melted masses will +pour out through the rent, flow over its edges, and fill all the +lesser cracks and fissures produced by such a disturbance. What will +be the effect upon the stratified rocks? Wherever these liquid masses, +melted by a heat more intense than can be produced by any artificial +means, have flowed over them or cooled in immediate contact with them, +the clays will be changed to slate, the limestone will have assumed a +character more like marble, while the sandstone will be vitrified. +This is exactly what has been found to be the case, wherever the +stratified rocks have been penetrated by the melted masses from +beneath. They have been themselves partially melted by the contact, +and when they have cooled again, their stratification, though still +perceptible, has been partly obliterated, and their substance changed. +Such effects may often be traced in dikes, which are only the cracks +in rocks filled by materials poured into them at some period of +eruption when the melted masses within the earth were thrown out and +flowed like water into any inequality or depression of the surface +around. The walls enclosing such a dike are often found to be +completely altered by contact with its burning contents, and to have +assumed a character quite different from the rocks of which they make +a part; while the mass itself which fills the fissure shows by the +character of its crystallization that it has cooled more quickly on +the outside, where it meets the walls, than at the centre. + +The first two great classes of rocks, the unstratified and stratified +rocks, represent different epochs in the world's physical history: the +former mark its revolutions, while the latter chronicle its periods of +rest. All mountains and mountain-chains have been upheaved by great +convulsions of the globe, which rent asunder the surface of the earth, +destroyed the animals and plants living upon it at the time, and were +then succeeded by long intervals of repose, when all things returned +to their accustomed order, ocean and river deposited fresh beds in +uninterrupted succession, the accumulation of materials went on as +before, a new set of animals and plants were introduced, and a time of +building up and renewing followed the time of destruction. These +periods of revolution are naturally more difficult to decipher than +the periods of rest; for they have so torn and shattered the beds they +uplifted, disturbing them from their natural relations to each other, +that it is not easy to reconstruct the parts and give them coherence +and completeness again. But within the last half-century this work has +been accomplished in many parts of the world with an amazing degree of +accuracy, considering the disconnected character of the phenomena to +be studied; and I think I shall be able to convince my readers that +the modern results of geological investigation are perfectly sound +logical inferences from well-established facts. In this, as in so many +other things, we are but "children of a larger growth." The world is +the geologist's great puzzle-box; he stands before it like the child +to whom the separate pieces of his puzzle remain a mystery till he +detects their relation and sees where they fit, and then his fragments +grow at once into a connected picture beneath his hand.... + +When geologists first turned their attention to the physical history +of the earth, they saw at once certain great features which they took +to be the skeleton and basis of the whole structure. They saw the +great masses of granite forming the mountains and mountain-chains, +with the stratified rocks resting against their slopes; and they +assumed that granite was the first primary agent, and that all +stratified rocks must be of a later formation. Although this involved +a partial error, as we shall see hereafter when we trace the upheavals +of granite even into comparatively modern periods, yet it held an +important geological truth also; for, though granite formations are by +no means limited to those early periods, they are nevertheless very +characteristic of them, and are indeed the foundation-stones on which +the physical history of the globe is built. + +Starting from this landmark, the earlier geologists divided the +world's history into three periods. As the historian recognizes +Ancient History, the Middle Ages, and Modern History as distinct +phases in the growth of the human race, so they distinguished between +what they called the Primary period, when, as they believed, no life +stirred on the surface of the earth; the Secondary or middle period, +when animals and plants were introduced, and the land began to assume +continental proportions; and the Tertiary period, or comparatively +modern geological times, when the physical features of the earth as +well as its inhabitants were approaching more nearly to the present +condition of things. But as their investigations proceeded, they found +that every one of these great ages of the world's history was divided +into numerous lesser epochs, each of which had been characterized by a +peculiar set of animals and plants, and had been closed by some great +physical convulsion, disturbing and displacing the materials +accumulated during such a period of rest. + +The further study of these subordinate periods showed that what had +been called Primary formations, namely, the volcanic or Plutonic rocks +formerly believed to be confined to the first geological ages, +belonged to all the periods, successive eruptions having taken place +at all times, pouring up through the accumulated deposits, penetrating +and injecting their cracks, fissures, and inequalities, as well as +throwing out large masses on the surface. Up to our own day there has +never been a period when such eruptions have not taken place, though +they have been constantly diminishing in frequency and extent. In +consequence of this discovery, that rocks of igneous character were by +no means exclusively characteristic of the earliest times, they are +now classified together upon very different grounds from those on +which geologists first united them; though, as the name _Primary_ was +long retained, we still find it applied to them, even in geological +works of quite recent date. This defect of nomenclature is to be +regretted, as likely to mislead the student, because it seems to refer +to time; whereas it no longer signifies the age of the rocks, but +simply their character. The name Plutonic or Massive rocks is, +however, now almost universally substituted for that of Primary. + +A wide field of investigation still remains to be explored by the +chemist and the geologist together, in the mineralogical character of +the Plutonic rocks, which differs greatly in the different periods. +The earlier eruptions seem to have been chiefly granitic, though this +must not be understood in too wide a sense, since there are granite +formations even as late as the Tertiary period; those of the middle +periods were mostly porphyries and basalts; while in the more recent +ones, lavas predominate. We have as yet no clew to the laws by which +this distribution of volcanic elements in the formation of the earth +is regulated; but there is found to be a difference in the crystals of +the Plutonic rocks belonging to different ages, which, when fully +understood may enable us to determine the age of any Plutonic rock by +its mode of crystallization; so that the mineralogist will as readily +tell you by its crystals whether a bit of stone of igneous origin +belongs to this or that period of the world's history, as the +palæontologist will tell you by its fossils whether a piece of rock +of aqueous origin belongs to the Silurian or Devonian or Carboniferous +deposits. + +Although subsequent investigations have multiplied so extensively not +only the number of geological periods, but also the successive +creations that have characterized them, yet the first general division +into three great eras was nevertheless founded upon a broad and true +generalization. In the first stratified rocks in which any organic +remains are found, the highest animals are fishes, and the highest +plants are cryptogams; in the middle periods reptiles come in, +accompanied by fern and moss forests; in later times quadrupeds are +introduced, with a dicotyledonous vegetation. So closely does the +march of animal and vegetable life keep pace with the material +progress of the world, that we may well consider these three +divisions, included under the first general classification of its +physical history, as the three Ages of Nature; the more important +epochs which subdivide them may be compared to so many great +dynasties, while the lesser periods are the separate reigns contained +therein. Of such epochs there are ten, well known to geologists; of +the lesser periods about sixty are already distinguished, while many +more loom up from the dim regions of the past, just discerned by the +eye of science, though their history is not yet unravelled. + +Before proceeding further, I will enumerate the geological epochs in +their succession, confining myself, however, to such as are perfectly +well established, without alluding to those of which the limits are +less definitely determined, and which are still subject to doubts and +discussions among geologists. As I do not propose to make here any +treatise of Geology, but simply to place before my readers some +pictures of the old world, with the animals and plants that have +inhabited it at various times, I shall avoid, as far as possible, all +debatable ground, and confine myself to those parts of my subject +which are best known, and can therefore be more clearly presented. + +[Illustration: FOSSIL SCORPION.--SILURIAN PERIOD.] + +First, we have the Azoic period, _devoid of life_, as its name +signifies,--namely, the earliest stratified deposits upon the heated +film forming the first solid surface of the earth, in which no trace +of living thing has ever been found. Next comes the Silurian period, +when the crust of the earth had thickened and cooled sufficiently to +render the existence of animals and plants upon it possible, and when +the atmospheric conditions necessary to their maintenance were already +established. Many of the names given to these periods are by no means +significant of their character, but are merely the result of accident: +as, for instance, that of Silurian, given by Sir Roderick Murchison to +this set of beds, because he first studied them in that part of Wales +occupied by the ancient tribe of the Silures. The next period, the +Devonian, was for a similar reason named after the country of +Devonshire in England, where it was first investigated. Upon this +follows the Carboniferous period, with the immense deposits of coal +from which it derives its name. Then comes the Permian period, named, +again, from local circumstances, the first investigation of its +deposits having taken place in the province of Permia in Russia. Next +in succession we have the Triassic period, so called from the trio of +rocks, the red sandstone, Muschel Kalk (shell-limestone), and Keuper +(clay), most frequently combined in its formations; the Jurassic, so +amply illustrated in the chain of the Jura, where geologists first +found the clew to its history; and the Cretaceous period, to which the +chalk cliffs of England and all the extensive chalk deposits belong. +Upon these follow the so-called Tertiary formations, divided into +three periods, all of which have received most characteristic names in +this epoch of the world's history we see the first approach to a +condition of things resembling that now prevailing, and Sir Charles +Lyell has most fitly named its three divisions, the Eocene, Miocene, +and Pliocene. The termination of the three words is made from the +Greek word _Kainos_, recent; while _Eos_ signifies dawn, _Meion_ less, +and _Pleion_ more. Thus Eocene indicates the dawn of recent species, +Pliocene their increase, while Miocene, the intermediate term, means +less recent. Above these deposits comes what has been called in +science the present period,--_the modern times_ of the geologist,--that +period to which man himself belongs, and since the beginning of which, +though its duration be counted by hundreds of thousands of years, +there has been no alteration in the general configuration of the +earth, consequently no important modification of its climatic +conditions, and no change in the animals and plants inhabiting it. + +[Illustration: CRUSTACEA.--DEVONIAN PERIOD.] + +[Illustration: FISH OF THE DEVONIAN PERIOD.] + +[Illustration: FISH OF THE CARBONIFEROUS PERIOD.] + +[Illustration: FOSSIL VEGETATION OF CARBONIFEROUS PERIOD.] + +[Illustration: FISH OF THE PERMIAN PERIOD.] + +I have spoken of the first of these periods, the Azoic, as having +been absolutely devoid of life, and I believe this statement to be +strictly true; but I ought to add that there is a difference of +opinion among geologists upon this point, many believing that the +first surface of our globe may have been inhabited by living beings, +but that all traces of their existence have been obliterated by the +eruptions of melted materials, which not only altered the character of +those earliest stratified rocks, but destroyed all the organic remains +contained in them. It will be my object to show, not only that the +absence of the climatic and atmospheric conditions essential to +organic life, as we understand it, must have rendered the previous +existence of any living beings impossible, but also that the +completeness of the Animal Kingdom in those deposits where we first +find organic remains, its intelligible and coherent connections with +the successive creations of all geological times and with the animals +now living, afford the strongest internal evidence that we have indeed +found in the lower Silurian formations, immediately following the +Azoic, the beginning of life upon earth. When a story seems to us +complete and consistent from the beginning to the end, we shall not +seek for a first chapter, even though the copy in which we have read +it be so torn and defaced as to suggest the idea that some portion of +it may have been lost. The unity of the work, as a whole, is an +incontestable proof that we possess it in its original integrity. The +validity of this argument will be recognized, perhaps, only by those +naturalists to whom the Animal Kingdom has begun to appear as a +connected whole. For those who do not see order in Nature it can have +no value. + +[Illustration: FOSSILS OF TRIASSIC VEGETATION.] + +[Illustration: BIRD OF THE JURASSIC PERIOD.(The Oldest Bird.)] + +[Illustration: SKELETON OF BIRD OF THE CRETACEOUS PERIOD.] + +[Illustration: SKELETON OF ANIMAL OF THE EOCENE PERIOD.] + +For a table containing the geological periods in their succession, I +would refer to any modern text-book of Geology, or to an article in +the _Atlantic Monthly_ for March, 1862, upon "Methods of Study in +Natural History," where they are given in connection with the order of +introduction of animals upon earth. + +Were these sets of rocks found always in the regular sequence in which +I have enumerated them, their relative age would be easily +determined, for their superposition would tell the whole story: the +lowest would, of course, be the oldest, and we might follow without +difficulty the ascending series, till we reached the youngest and +uppermost deposits. But their succession has been broken up by +frequent and violent alterations in the configuration of the globe. +Land and water have changed their level,--islands have been +transformed to continents,--sea-bottoms have become dry land, and dry +land has sunk to form sea-bottoms,--Alps and Himalayas, Pyrenees and +Apennines, Alleghanies and Rocky Mountains, have had their stormy +birthdays since many of these beds have been piled one above another, +and there are but few spots on the earth's surface where any number of +them may be found in their original order and natural position. When +we remember that Europe, which lies before us on the map as a +continent, was once an archipelago of islands,--that, where the +Pyrenees raise their rocky barrier between France and Spain, the +waters of the Mediterranean and Atlantic met,--that, where the British +Channel flows, dry land united England and France, and Nature in those +days made one country of the lands parted since by enmities deeper +than the waters that run between,--when we remember, in short, all the +fearful convulsions that have torn asunder the surface of the earth, +as if her rocky record had indeed been written on paper, we shall find +a new evidence of the intellectual unity which holds together the +whole physical history of the globe in the fact that through all the +storms of time the investigator is able to trace one unbroken thread +of thought from the beginning to the present hour. + +[Illustration: SKELETON OF ANIMAL OF THE MIOCENE PERIOD.] + +[Illustration: SKELETON OF ANIMAL OF THE PLIOCENE PERIOD.] + +The tree is known by its fruits,--and the fruits of chance are +incoherence, incompleteness, unsteadiness, the stammering utterance of +blind, unreasoning force. A coherence that binds all the geological +ages in one chain, a stability of purpose that completes in the beings +born to-day an intention expressed in the first creatures that swam in +the Silurian ocean or crept upon its shores, a steadfastness of +thought, practically recognized by man, if not acknowledged by him, +whenever he traces the intelligent connection between the facts of +Nature and combines them into what he is pleased to call his system of +Geology, or Zoölogy, or Botany,--these things are not the fruits of +chance or of an unreasoning force, but the legitimate results of +intellectual power. There is a singular lack of logic, as it seems to +me, in the views of the materialistic naturalists. While they consider +classification, or, in other words, their expression of the relations +between animals or between physical facts of any kind, as the work of +their intelligence, they believe the relations themselves to be the +work of physical causes. The more direct inference surely is, that, if +it requires an intelligent mind to recognize them, it must have +required an intelligent mind to establish them. These relations +existed before man was created; they have existed ever since the +beginning of time; hence, what we call the classification of facts is +not the work of his mind in any direct original sense, but the +recognition of an intelligent action prior to his own existence. + +There is, perhaps, no part of the world, certainly none familiar to +science, where the early geological periods can be studied with so +much ease and precision as in the United States. Along their northern +borders, between Canada and the United States, there runs the low line +of hills known as the Laurentian Hills. Insignificant in height, +nowhere rising more than fifteen hundred or two thousand feet above +the level of the sea, these are nevertheless the first mountains that +broke the uniform level of the earth's surface and lifted themselves +above the waters. Their low stature, as compared with that of other +more lofty mountain-ranges, is in accordance with an invariable rule, +by which the relative age of mountains may be estimated. The oldest +mountains are the lowest, while the younger and more recent ones tower +above their elders, and are usually more torn and dislocated also. +This is easily understood, when we remember that all mountains and +mountain-chains are the result of upheavals, and that the violence of +the outbreak must have been in proportion to the strength of the +resistance. When the crust of the earth was so thin that the heated +masses within easily broke through it, they were not thrown to so +great a height, and formed comparatively low elevations, such as the +Canadian hills or the mountains of Bretagne and Wales. But in later +times, when young, vigorous giants, such as the Alps, the Himalayas, +or, later still, the Rocky Mountains, forced their way out from their +fiery prison-house, the crust of the earth was much thicker, and +fearful indeed must have been the convulsions which attended their +exit. + +[Illustration: A PHYSICAL MAP OF THE UNITED STATES.] + +The Laurentian Hills form, then, a granite range, stretching from +Eastern Canada to the Upper Mississippi, and immediately along its +base are gathered the Azoic deposits, the first stratified beds, in +which the absence of life need not surprise us, since they were +formed beneath a heated ocean. As well might we expect to find the +remains of fish or shells or crabs at the bottom of geysers or of +boiling springs, as on those early shores bathed by an ocean of which +the heat must have been so intense. Although, from the condition in +which we find it, this first granite range has evidently never been +disturbed by any violent convulsion since its first upheaval, yet +there has been a gradual rising of that part of the continent; for the +Azoic beds do not lie horizontally along the base of the Laurentian +Hills in the position in which they must originally have been +deposited, but are lifted and rest against their slopes. They have +been more or less dislocated in this process, and are greatly +metamorphized by the intense heat to which they must have been +exposed. Indeed, all the oldest stratified rocks have been baked by +the prolonged action of heat. + +It may be asked how the materials for those first stratified deposits +were provided. In later times, when an abundant and various soil +covered the earth, when every river brought down to the ocean, not +only its yearly tribute of mud or clay or lime, but the débris of +animals and plants that lived and died in its waters or along its +banks, when every lake and pond deposited at its bottom in successive +layers the lighter or heavier materials floating in its waters and +settling gradually beneath them, the process by which stratified +materials are collected and gradually harden into rock is more easily +understood. But when the solid surface of the earth was only just +beginning to form, it would seem that the floating matter in the sea +can hardly have been in sufficient quantity to form any extensive +deposits. No doubt there was some abrasion even of that first crust; +but the more abundant source of the earliest stratification is to be +found in the submarine volcanoes that poured their liquid streams into +the first ocean. At what rate these materials would be distributed and +precipitated in regular strata it is impossible to determine; but that +volcanic materials were so deposited in layers is evident from the +relative position of the earliest rocks. I have already spoken of the +innumerable chimneys perforating the Azoic beds, narrow outlets of +Plutonic rock, protruding through the earliest strata. Not only are +such funnels filled with the crystalline mass of granite that flowed +through them in a liquid state, but it has often poured over their +sides, mingling with the stratified beds around. In the present state +of our knowledge, we can explain such appearances only by supposing +that the heated materials within the earth's crust poured out +frequently, meeting little resistance,--that they then scattered and +were precipitated in the ocean around, settling in successive strata +at its bottom,--that through such strata the heated masses within +continued to pour again and again, forming for themselves the +chimney-like outlets above mentioned. + +Such, then, was the earliest American land,--a long, narrow island, +almost continental in its proportions, since it stretched from the +eastern borders of Canada nearly to the point where now the base of +the Rocky Mountains meets the plain of the Mississippi Valley. We may +still walk along its ridge and know that we tread upon the ancient +granite that first divided the waters into a northern and southern +ocean; and if our imaginations will carry us so far, we may look down +toward its base and fancy how the sea washed against this earliest +shore of a lifeless world. This is no romance, but the bald, simple +truth; for the fact that this granite band was lifted out of the +waters so early in the history of the world, and has not since been +submerged, has, of course, prevented any subsequent deposits from +forming above it. And this is true of all the northern part of the +United States. It has been lifted gradually, the beds deposited in one +period being subsequently raised, and forming a shore along which +those of the succeeding one collected, so that we have their whole +sequence before us. In regions where all the geological deposits +(Silurian, Devonian, carboniferous, permian, triassic, etc.) are piled +one upon another, and we can get a glimpse of their internal relations +only where some rent has laid them open, or where their ragged edges, +worn away by the abrading action of external influences, expose to +view their successive layers, it must, of course, be more difficult to +follow their connection. For this reason the American continent offers +facilities to the geologist denied to him in the so-called Old World, +where the earlier deposits are comparatively hidden, and the broken +character of the land, intersected by mountains in every direction, +renders his investigation still more difficult. Of course, when I +speak of the geological deposits as so completely unveiled to us here, +I do not forget the sheet of drift which covers the continent from +north to south, and which we shall discuss hereafter, when I reach +that part of my subject. But the drift is only a superficial and +recent addition to the soil, resting loosely above the other +geological deposits, and arising, as we shall see, from very different +causes. + +In this article I have intended to limit myself to a general sketch of +the formation of the Laurentian Hills with the Azoic stratified beds +resting against them. In the Silurian epoch following the Azoic we +have the first beach on which any life stirred; it extended along the +base of the Azoic beds, widening by its extensive deposits the narrow +strip of land already upheaved. I propose ... to invite my readers to +a stroll with me along that beach. + +With what interest do we look upon any relic of early human history! +The monument that tells of a civilization whose hieroglyphic records +we cannot even decipher, the slightest trace of a nation that vanished +and left no sign of its life except the rough tools and utensils +buried in the old site of its towns or villages, arouses our +imagination and excites our curiosity. Men gaze with awe at the +inscription on an ancient Egyptian or Assyrian stone; they hold with +reverential touch the yellow parchment-roll whose dim, defaced +characters record the meagre learning of a buried nationality; and the +announcement, that for centuries the tropical forests of Central +America have hidden within their tangled growth the ruined homes and +temples of a past race, stirs the civilized world with a strange, deep +wonder. + +To me it seems, that to look on the first land that was ever lifted +above the waste of waters, to follow the shore where the earliest +animals and plants were created when the thought of God first +expressed itself in organic forms, to hold in one's hand a bit of +stone from an old sea-beach, hardened into rock thousands of +centuries ago, and studded with the beings that once crept upon its +surface or were stranded there by some retreating wave, is even of +deeper interest to men than the relies of their own race, for these +things tell more directly of the thoughts and creative acts of God. + +Standing in the neighborhood of Whitehall, near Lake George, one may +look along such a seashore, and see it stretching westward and sloping +gently southward as far as the eye can reach. It must have had a very +gradual slope, and the waters must have been very shallow; for at that +time no great mountains had been uplifted, and deep oceans are always +the concomitants of lofty heights. We do not, however, judge of this +by inference merely; we have an evidence of the shallowness of the sea +in those days in the character of the shells found in the Silurian +deposits, which shows that they belonged in shoal waters. + +Indeed, the fossil remains of all times tell us almost as much of the +physical condition of the world at different epochs as they do of its +animal and vegetable population. When Robinson Crusoe first caught +sight of the footprint on the sand, he saw in it more than the mere +footprint, for it spoke to him of the presence of men on his desert +island. We walk on the old geological shores, like Crusoe along his +beach, and the footprints we find there tell us, too, more than we +actually see in them. The crust of our earth is a great cemetery, +where the rocks are tombstones on which the buried dead have written +their own epitaphs. They tell us not only who they were and when and +where they lived, but much also of the circumstances under which they +lived. We ascertain the prevalence of certain physical conditions at +special epochs by the presence of animals and plants whose existence +and maintenance required such a state of things, more than by any +positive knowledge respecting it. Where we find the remains of +quadrupeds corresponding to our ruminating animals, we infer not only +land, but grassy meadows also, and an extensive vegetation; where we +find none but marine animals, we know the ocean must have covered the +earth; the remains of large reptiles, representing, though in gigantic +size, the half aquatic, half terrestrial reptiles of our own period, +indicate to us the existence of spreading marshes still soaked by the +retreating waters; while the traces of such animals as live now in +sand and shoal waters, or in mud, speak to us of shelving sandy +beaches and of mud-flats. The eye of the Trilobite tells us that the +sun shone on the old beach where he lived; for there is nothing in +nature without a purpose, and when so complicated an organ was made to +receive the light, there must have been light to enter it. The immense +vegetable deposits in the Carboniferous period announce the +introduction of an extensive terrestrial vegetation; and the +impressions left by the wood and leaves of the trees show that these +first forests must have grown in a damp soil and a moist atmosphere. +In short, all the remains of animals and plants hidden in the rocks +have something to tell of the climatic conditions and the general +circumstances under which they lived, and the study of fossils is to +the naturalist a thermometer by which he reads the variations of +temperature in past times, a plummet by which he sounds the depths of +the ancient oceans,--a register, in fact, of all the important +physical changes the earth has undergone. + +But although the animals of the early geological deposits indicate +shallow seas by their similarity to our shoal-water animals, it must +not be supposed that they are by any means the same. On the contrary, +the old shells, crustacea, corals, etc., represent types which have +existed in all times with the same essential structural elements, but +under different specific forms in the several geological periods. And +here it may not be amiss to say something of what are called by +naturalists _representative types_. + +The statement that different sets of animals and plants have +characterized the successive epochs is often understood as indicating +a difference of another kind than that which distinguishes animals now +living in different parts of the world. This is a mistake. There are +so-called representative types all over the globe, united to each +other by structural relations and separated by specific differences of +the same kind as those that unite and separate animals of different +geological periods. Take, for instance, mud-flats or sandy shores in +the same latitudes of Europe and America; we find living on each, +animals of the same structural character and of the same general +appearance, but with certain specific differences, as of color, size, +external appendages, etc. They represent each other on the two +continents. The American wolves, foxes, bears, rabbits, are not the +same as the European, but those of one continent are as true to their +respective types as those of the other; under a somewhat different +aspect they represent the same groups of animals. In certain +latitudes, or under conditions of nearer proximity, these differences +may be less marked. It is well known that there is a great monotony +of type, not only among animals and plants, but in the human races +also, throughout the Arctic regions; and some animals characteristic +of the high North reappear under such identical forms in the +neighborhood of the snow-fields in lofty mountains, that to trace the +difference between the ptarmigans, rabbits, and other gnawing animals +of the Alps, for instance, and those of the Arctics, is among the most +difficult problems of modern science. + +And so it is also with the animated world of past ages; in similar +deposits of sand, mud, or lime, in adjoining regions of the same +geological age, identical remains of animals and plants may be found; +while at greater distances, but under similar circumstances, +representative species may occur. In very remote regions, however, +whether the circumstances be similar or dissimilar, the general aspect +of the organic world differs greatly, remoteness in space being thus +in some measure an indication of the degree of affinity between +different faunæ. In deposits of different geological periods +immediately following each other, we sometimes find remains of animals +and plants so closely allied to those of earlier or later periods that +at first sight the specific differences are hardly discernible. The +difficulty of solving these questions, and of appreciating correctly +the differences and similarities between such closely allied +organisms, explains the antagonistic views of many naturalists +respecting the range of existence of animals, during longer or shorter +geological periods; and the superficial way in which discussions +concerning the transition of species are carried on, is mainly owing +to an ignorance of the conditions above alluded to. My own personal +observation and experience in these matters have led me to the +conviction that every geological period has had its own +representatives, and that no single species has been repeated in +successive ages. + +The laws regulating the geographical distribution of animals, and +their combination into distinct zoölogical provinces called faunæ, +with definite limits, are very imperfectly understood as yet; but so +closely are all things linked together from the beginning that I am +convinced we shall never find the clew to their meaning till we carry +on our investigations in the past and the present simultaneously. The +same principle according to which animal and vegetable life is +distributed over the surface of the earth now, prevailed in the +earliest geological periods. The geological deposits of all times have +had their characteristic faunæ under various zones, their zoölogical +provinces presenting special combinations of animal and vegetable life +over certain regions, and their representative types reproducing in +different countries, but under similar latitudes, the same groups with +specific differences. + +Of course, the nearer we approach the beginning of organic life, the +less marked do we find the differences to be, and for a very obvious +reason. The inequalities of the earth's surface, her mountain-barriers +protecting whole continents from the Arctic winds, her open plains +exposing others to the full force of the polar blasts, her snug +valleys and her lofty heights, her tablelands and rolling prairies, +her river-systems and her dry deserts, her cold ocean-currents pouring +down from the high North on some of her shores, while warm ones from +tropical seas carry their softer influence to others,--in short, all +the contrasts in the external configuration of the globe, with the +physical conditions attendant upon them, are naturally accompanied by +a corresponding variety in animal and vegetable life. + +But in the Silurian age, when there were no elevations higher than the +Canadian hills, when water covered the face of the earth, with the +exception of a few isolated portions lifted above the almost universal +ocean, how monotonous must have been the conditions of life! And what +should we expect to find on those first shores? If we are walking on a +sea-beach to-day, we do not look for animals that haunt the forests or +roam over the open plains, or for those that live in sheltered valleys +or in inland regions or on mountain-heights. We look for Shells, for +Mussels and Barnacles, for Crabs, for Shrimps, for Marine Worms, for +Star-Fishes and Sea-Urchins, and we may find here and there a fish +stranded on the sand or tangled in the seaweed. + +[Illustration] + + + + +SOME RECORDS OF THE ROCKS + +(FROM A FIRST BOOK IN GEOLOGY.) + +BY N.S. SHALER, S.D.[1] + +[Footnote 1: Copyright, 1884, by N.S. Shaler.] + +[Illustration] + +The geologist cannot find his way back in the record of the great +stone book, to the far-off day when life began. The various changes +that come over rocks from the action of heat, of water, and of +pressure, have slowly modified these ancient beds, so that they no +longer preserve the frames of the animals that were buried in them. + +These old rocks, which are so changed that we cannot any longer make +sure that any animals lived in them, are called the "archæan," which +is Greek for ancient. They were probably mud and sand and limestone +when first made, but they have been changed to mica schists, gneiss, +granite, marble, and other crystalline rocks. When any rock becomes +crystalline, the fossils dissolve and disappear, as coins lose their +stamp and form when they are melted in the jeweller's gold-pot. + +These ancient rocks that lie deepest in the earth are very thick, and +must have taken a great time in building; great continents must have +been worn down by rain and waves in order to supply the waste out of +which they were made. It is tolerably certain that they took as much +time during their making as has been required for all the other times +since they were formed. During the vast ages of this archæan the life +of our earth began to be. We first find many certain evidences of life +in the rocks which lie on top of the archæan rock, and are known as +the Cambriani and Silurian periods. There we have creatures akin to +our corals and crabs and worms, and others that are the distant +kindred of the cuttle-fishes and of our lamp-shells. There were no +backboned animals, that is to say, no land mammals, reptiles, or +fishes at this stage of the earth's history. It is not likely that +there was any land life except of plants and those forms like the +lowest ferns, and probably mosses. Nor is it likely that there were +any large continents as at the present time, but rather a host of +islands lying where the great lands now are, the budding tops of the +continents just appearing above the sea. + +Although the life of this time was far simpler than at the present +day, it had about as great variety as we would find on our present +sea-floors. There were as many different species living at the same +time on a given surface. + +The Cambrian and Silurian time--the time before the coming of the +fishes--must have endured for many million years without any great +change in the world. Hosts of species lived and died; half a dozen +times or more the life of the earth was greatly changed. New species +came much like those that had gone before, and only a little gain here +and there was perceptible at any time. Still, at the end of the +Silurian, the life of the world had climbed some steps higher in +structure and in intelligence. + +[Illustration: FIG. 1. NORTH AMERICA IN CAMBRIAN TIME.] + +The next set of periods is known as the Devonian. It is marked by the +rapid extension of the fishes; for, although the fishes began in the +uppermost Silurian, they first became abundant in this time. These, +the first strong-jawed tyrants of the sea, came all at once, like a +rush of the old Norman pirates into the peaceful seas of Great +Britain. They made a lively time among the sluggish beings of that +olden sea. Creatures that were able to meet feebler enemies were swept +away or compelled to undergo great changes, and all the life of the +oceans seems to have a spur given to it by these quicker-formed and +quicker-willed animals. In this Devonian section of our rocks we have +proofs that the lands were extensively covered with forests of low +fern trees, and we find the first trace of air-breathing animals in +certain insects akin to our dragon-flies. In this stage of the earth's +history the fishes grew constantly more plentiful, and the seas had a +great abundance of corals and crinoids. Except for the fishes, there +were no very great changes in the character of the life from that +which existed in the earlier time of the Cambrian and Silurian. The +animals are constantly changing, but the general nature of the life +remains the same as in the earlier time. + +[Illustration: FIG. 2. RANICEPS LYELLI--COAL TIME SALAMANDER.] + +In the Carboniferous or coal-bearing age, we have the second great +change in the character of the life on the earth. Of the earlier +times, we have preserved only the rocks formed in the seas. But rarely +do we find any trace of the land life or even of the life that lived +along the shores. In this Carboniferous time, however, we have very +extensive sheets of rocks which were formed in swamps in the way shown +in the earlier part of this book. They constitute our coal-beds, +which, though much worn away by rain and sea, still cover a large part +of the land surface. These beds of coal grew in the air, and, although +the swamps where they were formed had very little animal life in them, +we find some fossils which tell us that the life of the land was +making great progress; there are new insects, including beetles, +cockroaches, spiders, and scorpions, and, what is far more important, +there are some air-breathing, back-boned animals, akin to the +salamanders and water-dogs of the present day. These were nearly as +large as alligators, and of much the same shape, but they were +probably born from the egg in the shape of tadpoles and lived for a +time in the water as our young frogs, toads, and salamanders do. This +is the first step upwards from the fishes to land vertebrates; and we +may well be interested in it, for it makes one most important advance +in creatures through whose lives our own existence became possible. +Still, these ancient woods of the coal period must have had little of +the life we now associate with the forests; there were still no birds, +no serpents, no true lizards, no suck-giving animals, no flowers, and +no fruits. These coal-period forests were sombre wastes of shade, with +no sound save those of the wind, the thunder, and the volcano, or of +the running streams and the waves on the shores. + +In the seas of the Carboniferous time, we notice that the ancient life +of the earth is passing away. Many creatures, such as the trilobites, +die out, and many other forms such as the crinoids or sea lilies +become fewer in kind and of less importance. These marks of decay in +the marine life continue into the beds just after the Carboniferous, +known as the Permian, which are really the last stages of the +coal-bearing period. + +When with the changing time we pass to the beds known as the Triassic, +which were made just after the close of the Carboniferous time, we +find the earth undergoing swift changes in its life. The moist climate +and low lands that caused the swamps to grow so rapidly have ceased to +be, and in their place we appear to have warm, dry air, and higher +lands. + +On these lands of the Triassic time the air-breathing life made very +rapid advances. The plants are seen to undergo considerable changes. +The ferns no longer make up all the forests, but trees more like the +pines began to abound, and insects became more plentiful and more +varied. + +[Illustration: FIG. 3. CYCAS CIRCINALIS, AKIN TO HIGHEST PLANTS OF +COAL TIME.] + +Hitherto the only land back-boned animal was akin to our salamanders. +Now we have true lizards in abundance, many of them of large size. +Some of them were probably plant-eaters, but most were flesh-eaters; +some seem to have been tenants of the early swamps, and some dwelt in +the forests. + +The creatures related to the salamanders have increased in the variety +of their forms to a wonderful extent. We know them best by the tracks +which they have left on the mud stones formed on the borders of lakes +or the edge of the sea. In some places these footprints are found in +amazing numbers and perfection. The best place for them is in the +Connecticut Valley, near Turner's Falls, Mass. At this point the red +sandstone and shale beds, which are composed of thin layers having a +total thickness of several hundred feet, are often stamped over by +these footprints like the mud of a barnyard. From the little we can +determine from these footprints, the creatures seem to have been +somewhat related to our frogs, but they generally had tails, and, +though provided with four legs, were in the habit of walking on the +hind ones alone like the kangaroo. A few of these tracks are shown in +the figure on this page. + +[Illustration: FIG. 4. FOOT-PRINTS, CONNECTICUT SANDSTONES.] + +These strange creatures were of many different species. Some of them +must have been six or seven feet high, for their steps are as much as +three feet apart, and seem to imply a creature weighing several +hundred pounds. Others were not bigger than robins. Strangely enough, +we have never found their bones nor the creatures on which they fed, +and but for the formation of a little patch of rocks here and there we +should not have had even these footprints to prove to us that such +creatures had lived in the Connecticut Valley in this far-off time. + +[Illustration: FIG. 5. FOOT-PRINT, TURNER'S FALLS.] + +But these wonderful forms are less interesting than two or three +little fossil jaw-bones that prove to us that in this Triassic time +the earth now bore another animal more akin to ourselves, in the shape +of a little creature that gave suck to its young. Once more life takes +a long upward step in this little opossum-like animal, perhaps the +first creature whose young was born alive. These little creatures +called Microlestes or Dromatherium, of which only one or two different +but related species have been found in England and in North Carolina, +appear to have been insect-eaters of about the size and shape of the +Australian creature shown in Fig. 7. So far we know it in but few +specimens,--altogether only an ounce or two of bones,--but they are +very precious monuments of the past. + +[Illustration: FIG. 6. DROMATHERIUM SYLVESTRE AND TEETH OF MICROLESTES +ANTIQUUS.] + +In this Triassic time the climate appears to have been rather dry, for +in it we have many extensive deposits of salt formed by the +evaporation of closed lakes, of seas, such as are now forming on the +bottom of the Dead Sea, and the Great Salt Lake of Utah, and a hundred +or more other similar basins of the present day. + +[Illustration: FIG. 7. MYRMECOBIUS.] + +In the sea animals of this time we find many changes. Already some of +the giant lizard-like animals, which first took shape on the land, are +becoming swimming-animals. They changed their feet to paddles, which, +with the help of a flattened tail, force them through the water. + +The fishes on which these great swimming lizards preyed are more like +the fishes of our present day than they were before. The trilobites +are gone, and of the crinoids only a remnant is left. Most of the +corals of the earlier days have disappeared, but the mollusks have not +changed more than they did at several different times in the earliest +stages of the earth's history. + +[Illustration: FIG. 8. ICHTHYOSAURUS AND PLESIOSAURUS.] + +After the Trias comes a long succession of ages in which the life of +the world is steadily advancing to higher and higher planes; but for a +long time there is no such startling change as that which came in the +passage from the coal series of rocks to the Trias. This long set of +periods is known to geologists as the age of reptiles. It is well +named, for the kindred of the lizards then had the control of the +land. There were then none of our large fish to dispute their control, +so they shaped themselves to suit all the occupations that could give +them a chance for a living. Some remained beasts of prey like our +alligators, but grew to larger size; some took to eating the plants, +and came to walk on their four legs as our ordinary beasts do, no +longer dragging themselves on their bellies as do the lizard and +alligator, their lower kindred. Others became flying creatures like +our bats, only vastly larger, often with a spread of wing of fifteen +or twenty feet. Yet others, even as strangely shaped, dwelt with the +sharks in the sea. + +[Illustration: FIG. 9. REPTILES OF JURASSIC PERIOD.] + +In this time of the earth's history we have the first bird-like forms. +They were feathered creatures, with bills carrying true teeth, and +with strong wings; but they were reptiles in many features, having +long, pointed tails such as none of our existing birds have. They show +us that the birds are the descendants of reptiles, coming off from +them as a branch does from the parent tree. The tortoises began in +this series of rocks. At first they are marine or swimming forms, the +box-turtles coming later. Here too begin many of the higher insects. +Creatures like moths and bees appear, and the forests are enlivened +with all the important kinds of insects, though the species were very +different from those now living. + +In the age of reptiles the plants have made a considerable advance. +Palms are plenty; forms akin to our pines and firs abound, and the old +flowerless group of ferns begins to shrink in size, and no longer +spreads its feathery foliage over all the land as before. Still there +were none of our common broad-leaved trees; the world had not yet +known the oaks, birches, maples, or any of our hard-wood trees that +lose their leaves in autumn; nor were the flowering plants, those with +gay blossoms, yet on the earth. The woods and fields were doubtless +fresh and green, but they wanted the grace of blossoms, plants, and +singing-birds. None of the animals could have had the social qualities +or the finer instincts that are so common among animals of the present +day. There were probably no social animals like our ants and bees, no +merry singing creatures; probably no forms that went in herds. Life +was a dull round of uncared-for birth, cruel self-seeking, and of +death. The animals at best were clumsy, poorly-endowed creatures, with +hardly more intelligence than our alligators. + +The little thread of higher life begun in the Microlestes and +Dromatherium, the little insect-eating mammals of the forest, is +visible all through this time. It held in its warm blood the powers of +the time to come, but it was an insignificant thing among the mighty +cold-blooded reptiles of these ancient lands. There are several +species of them, but they are all small, and have no chance to make +headway against the older masters of the earth. + +The Jurassic or first part of the reptilian time shades insensibly +into the second part, called the Cretaceous, which immediately follows +it. During this period the lands were undergoing perpetual changes; +rather deep seas came to cover much of the land surfaces, and there is +some reason to believe that the climate of the earth became much +colder than it had been, at least in those regions where the great +reptiles had flourished. It may be that it is due to a colder climate +that we owe the rapid passing away of this gigantic reptilian life of +the previous age. The reptiles, being cold-blooded, cannot stand even +a moderate winter cold, save when they are so small that they can +crawl deep into crevices in the rocks to sleep the winter away, +guarded from the cold by the warmth of the earth. At any rate these +gigantic animals rapidly ceased to be, so that by the middle of the +Cretaceous period they were almost all gone, except those that +inhabited the sea; and at the end of this time they had shrunk to +lizards in size. The birds continue to increase and to become more +like those of our day; their tails shrink away, their long bills lose +their teeth; they are mostly water-birds of large size, and there are +none of our songsters yet; still they are for the first time perfect +birds, and no longer half-lizard in their nature. + +The greatest change in the plants is found in the coming of the +broad-leaved trees belonging to the families of our oaks, maples, etc. +Now for the first time our woods take on their aspect of to-day; pines +and other cone-bearers mingle with the more varied foliage of +nut-bearing or large-seeded trees. Curiously enough, we lose sight of +the little mammals of the earlier time. This is probably because there +is very little in the way of land animals of this period preserved to +us. There are hardly any mines or quarries in the beds of this age to +bring these fossils to light. In the most of the other rocks there is +more to tempt man to explore them for coal ores or building stones. + +In passing from the Cretaceous to the Tertiary, we enter upon the +threshold of our modern world. We leave behind all the great wonders +of the old world, the gigantic reptiles, the forests of tree ferns, +the seas full of ammonites and belemnites, and come among the no less +wonderful but more familiar modern forms. We come at once into lands +and seas where the back-boned animals are the ruling beings. The +reptiles have shrunk to a few low forms,--the small lizards, the +crocodiles and alligators, the tortoises and turtles, and, as if to +mark more clearly the banishment of this group from their old empire, +the serpents, which are peculiarly degraded forms of reptiles which +have lost the legs they once had, came to be the commonest reptiles of +the earth. + +The first mammals that have no pouches now appear. In earlier times, +the suck-giving animals all belonged to the group that contains our +opossums, kangaroos, etc. These creatures are much lower and feebler +than the mammals that have no pouches. Although they have probably +been on the earth two or three times as long as the higher mammals, +they have never attained any eminent success whatever; they cannot +endure cold climates; none of them are fitted for swimming as are the +seals and whales, or for flying as the bats, or for burrowing as the +moles; they are dull, weak things, which are not able to contend with +their stronger, better-organized, higher kindred. They seem not only +weak, but unable to fit themselves to many different kinds of +existence. + +In the lower part of the Tertiary rocks, we find at once a great +variety of large beasts that gave suck to their young. It is likely +that these creatures had come into existence in a somewhat earlier +time in other lands, where we have not been able to study the fossils; +for to make their wonderful forms slowly, as we believe them to have +been made, would require a very long time. It is probable that during +the Cretaceous time, in some land where we have not yet had a chance +to study the rocks, these creatures grew to their varied forms, and +that in the beginning of the Tertiary time, they spread into the +regions where we find their bones. + +Beginning with the Tertiary time, we find these lower kinsmen of man, +through whom man came to be. The mammals were marked by much greater +simplicity and likeness to each other than they now have. There were +probably no monkeys, no horses, no bulls, no sheep, no goats, no +seals, no whales, and no bats. All these animals had many-fingered +feet. There were no cloven feet like those of our bulls, and no solid +feet as our horses have. Their brains, which by their size give us a +general idea of the intelligence of the creature, are small; hence we +conclude that these early mammals were less intelligent than those of +our day. + +It would require volumes to trace the history of the growth of these +early mammals, and show how they, step by step, came to their present +higher state. We will take only one of the simplest of these changes, +which happens to be also the one which we know best. This is the +change that led to the making of our common horses, which seem to have +been brought into life on the continent of North America. The most +singular thing about our horses is that the feet have but one large +toe or finger, the hoof, the hard covering of which is the nail of +that extremity. Now it seems hard to turn the weak, five-fingered +feet of the animals of the lower Tertiary--feet which seem to be +better fitted for tree-climbing than anything else--into feet such as +we find in the horse. Yet the change is brought about by easy stages +that lead the successive creatures from the weak and loose-jointed +foot of the ancient forms to the solid, single-fingered horse's hoof, +which is wonderfully well-fitted for carrying a large beast at a swift +speed, and is so strong a weapon of defence that an active donkey can +kill a lion with a well-delivered kick. + +[Illustration: FIG. 10. FEET OF TERTIARY MAMMALS.] + +The oldest of these creatures that lead to the horses is called +_Eohippus_ or beginning horse. This fellow had on the forefeet four +large toes, each with a small hoof and fifth imperfect one, which +answered to the thumb. The hind feet had gone further in the change, +for they each had but three toes, each with hoofs, the middle-toed +hoof larger and longer than the others. A little later toward our day +we find another advance in the _Orohippus_, when the little imperfect +thumb has disappeared, and there are only four toes on the forefeet +and three on the hind. + +Yet later we have the _Mesohippus_ or half-way horse. There are still +three toes on the hind foot, but one more of the fingers of the +forefeet has disappeared. This time it is the little finger that goes, +leaving only a small bone to show that its going was by a slow +shrinking. The creature now has three little hoofs on each of its +feet. + +Still nearer our own time comes the _Miohippus_, which shows the two +side hoofs on each foot shrinking up so that they do not touch the +ground, but they still bear little hoofs. Lastly, about the time of +man's coming on the earth, appears his faithful servant, the horse, in +which those little side hoofs have disappeared, leaving only two +little "splint" bones to mark the place where these side hoofs belong. +Thus, step by step, our horses' feet were built up; while these parts +were changing, the other parts of the animals were also slowly +altering. They were at first smaller than our horses,--some of them +not as large as an ordinary Newfoundland dog; others as small as +foxes. + +[Illustration: FIG. 11. DEVELOPMENT OF HORSES'S FOOT.] + +As if to remind us of his old shape, our horses now and then, but +rarely, have, in place of the little splint bones above the hoof, two +smaller hoofs, just like the foot of _Miohippus_. Sometimes these are +about the size of a silver dollar, on the part that receives the shoe +when horses are shod. + +In this way, by slow-made changes, the early mammals pass into the +higher. Out of one original part are made limbs as different as the +feet of the horse, the wing of a bat, the paddle of a whale, and the +hand of man. So with all the parts of the body the forms change to +meet the different uses to which they are put. + +At the end of this long promise, which was written in the very first +animals, comes man himself, in form closely akin to the lower animals, +but in mind immeasurably apart from them. We can find every part of +man's body in a little different shape in the monkeys, but his mind is +of a very different quality. While his lower kindred cannot be made to +advance in intelligence any more than man himself can grow a horse's +foot or a bat's wing, he is constantly going higher and higher in his +mental and moral growth. + +So far we have found but few traces of man that lead us to suppose +that he has been for a long geological time on the earth, yet there is +good evidence that he has been here for a hundred thousand years or +more. It seems pretty clear that he has changed little in his body in +all these thousands of generations. The earliest remains show us a +large-brained creature, who used tools and probably had already made a +servant of fire, which so admirably aids him in his work. + +Besides the development of this wonderful series of animals, that we +may call in a certain way our kindred, there have been several other +remarkable advances in this Tertiary time, this age of crowning +wonders in the earth's history. The birds have gone forward very +rapidly; it is likely that there were no songsters at the first part +of this period, but these singing birds have developed very rapidly in +later times. Among the insects the most remarkable growth is among the +ants, the bees, and their kindred. These creatures have very wonderful +habits; they combine together for the making of what we may call +states, they care for their young, they wage great battles, they keep +slaves, they domesticate other insects, and in many ways their acts +resemble the doings of man. Coming at about the same time as man, +these intellectual insects help to mark this later stage of the earth +as the intellectual period in its history. Now for the first time +creatures are on the earth which can form societies and help each +other in the difficult work of living. + +Among the mollusks, the most important change is in the creation of +the great, strong swimming squids, the most remarkable creatures of +the sea. Some of these have arms that can stretch for fifty feet from +tip to tip. + +Among the plants, the most important change has been in the growth of +flowering plants, which have been constantly becoming more plenty, and +the plants which bear fruits have also become more numerous. The +broad-leaved trees seem to be constantly gaining on the forests of +narrow-leaved cone-bearers, which had in an earlier day replaced the +forests of ferns. + +In these Tertiary ages, as in the preceding times of the earth, the +lands and seas were much changed in their shape. It seems that in the +earlier ages the land had been mostly in the shape of large islands +grouped close together where the continents now are. In this time, +these islands grew together to form the united lands of Europe, Asia, +Africa, Australia, and the twin American continents; so that, as life +rose higher, the earth was better fitted for it. Still there were +great troubles that it had to undergo. There were at least two +different times during the Tertiary age termed glacial periods, times +when the ice covered a large part of the northern continents, +compelling life of all sorts to abandon great regions, and to find new +places in more southern lands. Many kinds of animals and plants seem +to have been destroyed in these journeys; but these times of trial, by +removing the weaker and less competent creatures, made room for new +forms to rise in their places. All advance in nature makes death +necessary, and this must come to races as well as to individuals if +the life of the world is to go onward and upward. + +Looking back into the darkened past, of which we yet know but little +compared with what we would like to know, we can see the great armies +of living beings led onward from victory to victory toward the higher +life of our own time. Each age sees some advance, though death +overtakes all its creatures. Those that escape their actual enemies or +accident, fall a prey to old age: volcanoes, earthquakes, glacial +periods, and a host of other violent accidents sweep away the life of +wide regions, yet the host moves on under a control that lies beyond +the knowledge of science. Man finds himself here as the crowning +victory of this long war. For him all this life appears to have +striven. In his hands lies the profit of all its toil and pain. +Surely this should make us feel that our duty to all these living +things, that have shared in the struggle that has given man his +elevation, is great, but above all, great is our duty to the powers +that have been placed in our bodies and our minds. + +[Illustration: A GLACIER.] + + + + +THE PITCH LAKE IN THE WEST INDIES + +(FROM AT LAST.) + +BY C. KINGSLEY. + + +[Illustration: COOLIE AND NEGRO.] + +The Pitch Lake, like most other things, owes its appearance on the +surface to no convulsion or vagary at all, but to a most slow, +orderly, and respectable process of nature, by which buried vegetable +matter, which would have become peat, and finally brown coal, in a +temperate climate, becomes, under the hot tropic soil, asphalt and +oil, continually oozing up beneath the pressure of the strata above +it.... + + * * * * * + +As we neared the shore, we perceived that the beach was black with +pitch; and the breeze being off the land, the asphalt smell (not +unpleasant) came off to welcome us. We rowed in, and saw in front of a +little row of wooden houses a tall mulatto, in blue policeman's dress, +gesticulating and shouting to us. He was the ward policeman, and I +found him (as I did all the colored police) able and courteous, shrewd +and trusty. These police are excellent specimens of what can be made +of the negro, or half-negro, if he be but first drilled, and then +given a responsibility which calls out his self-respect. He was +warning our crew not to run aground on one or other of the pitch +reefs, which here take the place of rocks. A large one, a hundred +yards off on the left, has been almost all dug away, and carried to +New York or to Paris to make asphalt-pavement. + +[Illustration: THE POLICE STATION.] + +The boat was run ashore, under his directions, on a spit of sand +between the pitch; and when she ceased bumping up and down in the +muddy surf, we scrambled out into a world exactly the hue of its +inhabitants of every shade, from jet black to copper-brown. The +pebbles on the shore were pitch. A tide-pool close by was enclosed in +pitch; a four-eyes was swimming about in it, staring up at us; and +when we hunted him, tried to escape, not by diving, but by jumping on +shore on the pitch, and scrambling off between our legs. While the +policeman, after profoundest courtesies, was gone to get a mule-cart +to take us up to the lake, and planks to bridge its water channels, +we took a look round at this oddest of corners of the earth. + +In front of us was the unit of civilization,--the police-station, +wooden, on wooden stilts (as all well-built houses are here), to +insure a draught of air beneath them. We were, of course, asked to +come in and sit down, but preferred looking about, under our +umbrellas; for the heat was intense. The soil is half pitch, half +brown earth, among which the pitch sweals in and out as tallow sweals +from a candle. It is always in slow motion under the heat of the +tropic sun; and no wonder if some of the cottages have sunk right and +left in such a treacherous foundation. A stone or brick house could +not stand here; but wood and palm-thatch are both light and tough +enough to be safe, let the ground give way as it will. + +The soil, however, is very rich. The pitch certainly does not injure +vegetation, though plants will not grow actually in it. The first +plants which caught our eyes were pine-apples, for which La Brea is +famous. The heat of the soil, as well as the air, brings them to +special perfection. They grow about anywhere, unprotected by hedge or +fence; for the negroes here seem honest enough, at least toward each +other; and at the corner of the house was a bush worth looking at, for +we had heard of it for many a year. It bore prickly, heart-shaped pods +an inch long, filled with seeds coated with a red waxy pulp. + +This was a famous plant--_Bixa orellana Roucou_; and that pulp was the +well-known annotto dye of commerce. In England and Holland it is used +merely, I believe, to color cheeses, but in the Spanish Main to color +human beings. The Indian of the Orinoco prefers paint to clothes; and +when he has "roucoued" himself from head to foot, considers himself in +full dress, whether for war or dancing. Doubtless he knows his own +business best from long experience. Indeed, as we stood broiling on +the shore, we began somewhat to regret that European manners and +customs prevented our adopting the Guaraon and Arrawak fashion. + +[Illustration: THE MULE-CART.] + +The mule-cart arrived; the lady of the party was put into it on a +chair, and slowly bumped and rattled past the corner of Dundonald +Street--so named after the old sea-hero, who was, in his life-time, +full of projects for utilizing this same pitch--and up in pitch road, +with a pitch gutter on each side. + +The pitch in the road has been, most of it, laid down by hand, and is +slowly working down the slight incline, leaving pools and ruts full of +water, often invisible, because covered with a film of brown +pitch-dust, and so letting in the unwary walker over his shoes. The +pitch in the gutter-bank is in its native place, and as it spues +slowly out of the soil into the ditch in odd wreaths and lumps, we +could watch, in little, the process which has produced the whole +deposit--probably the whole lake itself. + +A bullock-cart, laden with pitch, came jolting down past us, and we +observed that the lumps, when the fracture is fresh, have all a drawn +out look; that the very air bubbles in them, which are often very +numerous, are all drawn out likewise, long and oval, like the +air-bubbles in some ductile lavas. + +On our left, as we went on, the bush was low, all of yellow cassia and +white Hibiscus, and tangled with lovely convolvulus-like creepers, +Ipomoea and Echites, with white, purple or yellow flowers. On the +right were negro huts and gardens, fewer and fewer as we went on,--all +rich with fruit trees, especially with oranges, hung with fruit of +every hue; and beneath them, of course, the pine-apples of La Brea. +Everywhere along the road grew, seemingly wild here, that pretty low +tree, Cashew, with rounded yellow-veined leaves and little green +flowers, followed by a quaint pink and red-striped pear, from which +hangs, at the larger and lower end, a kidney-shaped bean, which bold +folk eat when roasted; but woe to those who try it when raw; for the +acrid oil blisters the lips, and even while the beans are roasting the +fumes of the oil will blister the cook's face if she holds it too near +the fire. + +As we went onward up the gentle slope (the rise is one hundred and +thirty-eight feet in rather more than a mile), the ground became more +and more full of pitch, and the vegetation poorer and more rushy, +till it resembled, on the whole, that of an English fen. An Ipomoea or +two, and a scarlet flowered dwarf Heliconia, kept up the tropic type, +as does a stiff brittle fern about two feet high. We picked the weeds, +which looked like English mint or basil, and found that most of them +had three longitudinal nerves in each leaf, and were really +Melastomas, though dwarfed into a far meaner habit than that of the +noble forms we saw at Chaguanas, and again on the other side of the +lake. On the right, too, in a hollow, was a whole wood of Groogroo +palms, gray stemmed, gray leaved, and here and there a patch of white +or black Roseau rose gracefully eight or ten feet high among the +reeds. + +The plateau of pitch now widened out, and the whole ground looked like +an asphalt pavement, half overgrown with marsh-loving weeds, whose +roots feed in the sloppy water which overlies the pitch. But, as yet, +there was no sign of the lake. The incline, though gentle, shuts off +the view of what is beyond. This last lip of the lake has surely +overflowed, and is overflowing still, though very slowly. Its furrows +all curve downward; and it is, in fact, as one of our party said, "a +black glacier." The pitch, expanding under the burning sun of day, +must needs expand most toward the line of least resistance--that is, +downhill; and when it contracts again under the coolness of night, it +contracts, surely, from the same cause, more downhill than uphill; and +so each particle never returns to the spot whence it started, but +rather drags the particles above it downward toward itself. At least, +so it seemed to us. Thus may be explained the common mistake which is +noticed by Messrs. Wall and Sawkins in their admirable description of +the lake. + +"All previous descriptions refer the bituminous matter scattered over +the La Brea district, and especially that between the village and the +lake, to streams which have issued at some former epoch from the lake, +and extended into the sea. This supposition is totally incorrect, as +solidification would probably have ensued before it had proceeded +one-tenth of the distance; and such of the asphalt as has undoubtedly +escaped from the lake has not advanced more than a few yards, and +always presents the curved surfaces already described, and never +appears as an extended sheet." + +Agreeing with this statement as a whole, I nevertheless cannot but +think it probable that a great deal of the asphalt, whether it be in +large masses or in scattered veins, may be moving very slowly down +hill, from the lake to the sea, by the process of expansion by day and +contraction by night, and may be likened to a caterpillar, or rather +caterpillars innumerable, progressing by expanding and contracting +their rings, having strength enough to crawl down hill, but not +strength enough to back up hill again. + +At last we surmounted the last rise, and before us lay the famous +lake--not at the bottom of a depression, as we expected, but at the +top of a rise, whence the ground slopes away from it on two sides, and +rises from it very slightly on the two others. The black pool glared +and glittered in the sun. A group of islands, some twenty yards wide, +were scattered about the middle of it. Beyond it rose a double forest +of Moriche fan-palms; and to the right of them high wood with giant +Mombins and undergrowth of Cocorite--a paradise on the other side of +the Stygian pool. + +[Illustration: THE PITCH LAKE.] + +We walked, with some misgivings, on to the asphalt, and found it +perfectly hard. In a few steps we were stopped by a channel of clear +water, with tiny fish and water-beetles in it; and, looking round, saw +that the whole lake was intersected with channels, so unlike anything +which can be seen elsewhere that it is not easy to describe them. + +Conceive a crowd of mushrooms, of all shapes, from ten to fifty feet +across, close together side by side, their tops being kept at exactly +the same level, their rounded rims squeezed tight against each other; +then conceive water poured on them so as to fill the parting seams, +and in the wet season, during which we visited it, to overflow the +tops somewhat. Thus would each mushroom represent, tolerably well, one +of the innumerable flat asphalt bosses, which seem to have sprung up +each from a separate centre, while the parting seams would be of much +the same shape as those in the asphalt, broad and shallow atop, and +rolling downward in a smooth curve, till they are at bottom mere +cracks from two to ten feet deep. Whether these cracks actually close +up below, and the two contiguous masses of pitch become one, cannot be +seen. As far as the eye goes down, they are two, though pressed close +to each other. Messrs. Wall and Sawkins explain the odd fact clearly +and simply. The oil, they say, which the asphalt contains when it +rises first, evaporates in the sun, of course most on the outside of +the heap, leaving a thorough coat of asphalt, which has, generally, no +power to unite with the corresponding coat of the next mass. Meanwhile +Mr. Manross, an American gentleman, who has written a very clever and +interesting account of the lake, seems to have been so far deceived by +the curved and squeezed edges of these masses that he attributes to +each of them a revolving motion, and supposes that the material is +continually passing from the centre to the edges, when it "rolls +under," and rises again in the middle. Certainly the strange stuff +looks, at the first glance, as if it were behaving in this way; and +certainly, also, his theory would explain the appearance of sticks and +logs in the pitch. But Messrs. Wall and Sawkins say that they have +observed no such motion: nor did we; and I agree with them, that it is +not very obvious to what force, or what influence, it could be +attributable. We must, therefore, seek some other way of accounting +for the sticks--which utterly puzzled us, and which Mr. Manross well +describes as "numerous pieces of wood, which, being involved in the +pitch, are constantly coming to the surface. They are often several +feet in length, and five or six inches in diameter. On reaching the +surface they generally assume an upright position, one end being +detained in the pitch, while the other is elevated by the lifting of +the middle. They may be seen at frequent intervals over the lake, +standing up to the height of two or even three feet. They look like +stumps of trees protruding through the pitch; but their parvenu +character is curiously betrayed by a ragged cap of pitch which +invariably covers the top, and hangs down like hounds' ears on either +side." + +Whence do they come? Have they been blown on to the lake, or left +behind by man? or are they fossil trees, integral parts of the +vegetable stratum below which is continually rolling upward? or are +they of both kinds? I do not know. Only this is certain, as Messrs. +Wall and Sawkins have pointed out, that not only "the purer varieties +of asphalt, such as approach or are identical with asphalt glance, +have been observed" (though not, I think, in the lake itself) "in +isolated masses, where there was little doubt of their proceeding from +ligneous substances of larger dimensions, such as roots and pieces of +trunks and branches," but, moreover, that "it is also necessary to +admit a species of conversion by contact, since pieces of wood +included accidentally in the asphalt, for example, by dropping from +overhanging vegetation, are often found partially transformed into the +material." This is a statement which we verified again and again, as +we did the one which follows, namely, that the hollow bubbles which +abound on the surface of the pitch "generally contain traces of the +lighter portion of vegetation," and "are manifestly derived from +leaves, etc., which are blown about the lake by the wind, and are +covered with asphalt, and, as they become asphalt themselves, give off +gases which form bubbles round them." + +But how is it that those logs stand up out of the asphalt, with +asphalt caps and hounds' ears (as Mr. Manross well phrases it) on the +tops of them? + +We pushed on across the lake, over the planks which the negroes laid +down from island to island. Some, meanwhile, preferred a steeple-chase +with water-jumps, after the fashion of the midshipmen on a certain +second visit to the lake. How the negroes grinned delight and surprise +at the vagaries of English lads--a species of animal altogether new to +them; and how they grinned still more when certain staid and portly +dignitaries caught the infection, and proved by more than one good +leap that they too had been English school-boys--alas! long, long ago. + +So, whether by bridging, leaping, or wading, we arrived at the little +islands, and found them covered with a thick, low scrub; deep sedge, +and among them Pinguins, like huge pine-apples without the apple; gray +wild-pines, parasites on Matapalos, which, of course, have established +themselves, like robbers and vagrants as they are, everywhere; a true +holly, with box-like leaves; and a rare cocoa-plum, very like the +holly in habit, which seems to be all but confined to these little +patches of red earth, afloat on the pitch. Out of the scrub, when we +were there, flew off two or three night-jars, very like our English +species, save that they had white in the wings; and on the second +visit one of the midshipmen, true to the English boy's bird's-nesting +instinct, found one of their eggs, white-spotted, in a grass nest. + +Passing these little islands, which are said (I know not how truly) to +change their places and number, we came to the very fountains of Styx, +to that part of the lake where the asphalt is still oozing up. + +As the wind set toward us, we soon became aware of an evil +smell--petroleum and sulphureted hydrogen at once--which gave some of +us a headache. The pitch here is yellow and white with sulphur foam; +so are the water-channels; and out of both water and pitch innumerable +bubbles of gas arise, loathsome to the smell. We became aware that the +pitch was soft under our feet. We left the impression of our boots; +and if we had stood still awhile, we should soon have been ankle-deep. +No doubt there are spots where, if a man stayed long enough, he would +be slowly and horribly engulfed. "But," as Mr. Manross says truly, "in +no place is it possible to form those bowl-like depressions round the +observer described by former travellers." What we did see is that the +fresh pitch oozes out at the lines of least resistance, namely, in the +channels between the older and more hardened masses, usually at the +upper ends of them, so that one may stand on pitch comparatively hard, +and put one's hand into pitch quite liquid, which is flowing softly +out, like some ugly fungoid growth, such as may be seen in old +wine-cellars, into the water. One such pitch-fungus had grown several +yards in length in the three weeks between our first and second visit; +and on another, some of our party performed exactly the same feat as +Mr. Manross. + +"In one of the star-shaped pools of water, some five feet deep, a +column of pitch had been forced perpendicularly up from the bottom. On +reaching the surface of the water it had formed a sort of +centre-table, about four feet in diameter, but without touching the +sides of the pool. The stem was about a foot in diameter. I leaped out +on this table, and found that it not only sustained my weight, but +that the elasticity of the stem enabled me to rock it from side to +side. Pieces torn from the edges of this table sank readily, showing +that it had been raised by pressure, and not by its buoyancy." + +True, though strange; but stranger still did it seem to us when we did +at last what the negroes asked us, and dipped our hands into the +liquid pitch, to find that it did not soil the fingers. The old +proverb that one cannot touch pitch without being defiled happily does +not stand true here, or the place would be intolerably loathsome. It +can be scraped up, moulded into any shape you will, wound in a string +(as was done by one of the midshipmen) round a stick, and carried off; +but nothing is left on the hand save clean gray mud and water. It may +be kneaded for an hour before the mud be sufficiently driven out of it +to make it sticky. This very abundance of earthy matter it is which, +while it keeps the pitch from soiling, makes it far less valuable than +it would be were it pure. + +It is easy to understand whence this earthy matter (twenty or thirty +per cent) comes. Throughout the neighborhood the ground is full, to +the depth of hundreds of feet, of coaly and asphaltic matter. Layers +of sandstone or of shale containing this decayed vegetable alternate +with layers which contain none; and if, as seems probable, the coaly +matter is continually changing into asphalt and oil, and then working +its way upward through every crack and pore, to escape from the +enormous pressure of the superincumbent soil, it must needs carry up +with it innumerable particles of the soils through which it passes. + +In five minutes we had seen, handled, and smelt enough to satisfy us +with this very odd and very nasty vagary of tropic nature; and as we +did not wish to become faint and ill between the sulphureted hydrogen +and the blaze of the sun reflected off the hot black pitch, we hurried +on over the water-furrows, and through the sedge-beds to the farther +shore--to find ourselves, in a single step, out of an Inferno into a +Paradise. + +[Illustration] + + + + +A STALAGMITE CAVE + +(FROM THE VOYAGE OF THE CHALLENGER.) + +BY SIR C. WYVILLE THOMSON, KT., LL.D., ETC. + + +[Illustration] + +I think the Painter's Vale cave is the prettiest of the whole. The +opening is not very large. It is an arch over a great mass of débris +forming a steep slope into the cave, as if part of the roof of the +vault had suddenly fallen in. At the foot of the bank of débris one +can barely see in the dim light the deep clear water lying perfectly +still and reflecting the roof and margin like a mirror. We clambered +down the slope, and as the eye became more accustomed to the obscurity +the lake stretched further back. There was a crazy little punt moored +to the shore, and after lighting candles Captain Nares rowed the +Governor back into the darkness, the candles throwing a dim light for +a time--while the voices became more hollow and distant--upon the +surface of the water and the vault of stalactite, and finally passing +back as mere specks into the silence. + +[Illustration: A GUIDE.] + +After landing the Governor on the opposite side, Captain Nares +returned for me, and we rowed round the weird little lake. It was +certainly very curious and beautiful; evidently a huge cavity out of +which the calcareous sand had been washed or dissolved, and whose +walls, still to a certain extent permeable, had been hardened and +petrified by the constant percolation of water charged with carbonate +of lime. From the roof innumerable stalactites, perfectly white, often +several yards long and coming down to the delicacy of knitting-needles, +hung in clusters; and wherever there was any continuous crack in the +roof or wall, a graceful, soft-looking curtain of white stalactite +fell, and often ended, much to our surprise. Deep in the water +Stalagmites also rose up in pinnacles and fringes through the water, +which was so exquisitely still and clear that it was something +difficult to tell where the solid marble tracery ended, and its +reflected image began. In this cave, which is a considerable distance +from the sea, there is a slight change of level with the tide +sufficient to keep the water perfectly pure. The mouth of the cave is +overgrown with foliage, and every tree is draped and festooned with +the fragrant _Jasminum gracile_, mingled not unfrequently with the +"poison ivy" (_Rhus toxicodendron_). The Bermudians, especially the +dark people, have a most exaggerated horror of this bush. They imagine +that if one touch it or rub against it he becomes feverish, and is +covered with an eruption. This is no doubt entirely mythical. The +plant is very poisonous, but the perfume of the flower is rather +agreeable, and we constantly plucked and smelt it without its +producing any unpleasant effect. The tide was with us when we regained +the Flats Bridge, and the galley shot down the rapid like an arrow, +the beds of scarlet sponges and the great lazy trepangs showing +perfectly clearly on the bottom at a fathom depth. + +[Illustration: FIG. 1. CALCAREOUS CONCRETION SIMULATING A FOSSIL +PALM-STEM, BOAZ ISLAND, BERMUDAS.] + +Every here and there throughout the islands there are groups of bodies +of very peculiar form projecting from the surface of the limestone +where it has been weathered. These have usually been regarded as +fossil palmetto stumps, the roots of trees which have been overwhelmed +with sand and whose organic matter has been entirely removed and +replaced by carbonate of lime. Fig. 1 represents one of the most +characteristic of these from a group on the side of the road in Boaz +Island. It is a cylinder a foot in diameter and six inches or so high; +the upper surface forms a shallow depression an inch deep surrounded +by a raised border; the bottom of the cup is even, and pitted over +with small depressions like the marks of rain-drops on sand; the walls +of the cylinder seem to end a few inches below the surface of the +limestone in a rounded boss, and all over this there are round +markings or little cylindrical projections like the origins of +rootlets. The object certainly appears to agree even in every detail +with a fossil palm-root, and as the palmetto is abundant on the +islands and is constantly liable to be destroyed by and ultimately +enveloped in a mass of moving sand, it seemed almost unreasonable to +question its being one. Still something about the look of these things +made me doubt, with General Nelson, whether they were fossil palms, or +indeed whether they were of organic origin at all; and after carefully +examining and pondering over several groups of them, at Boaz Island, +on the shore at Mount Langton, and elsewhere, I finally came to the +conclusion that they were not fossils, but something totally +different. + +[Illustration: FIG. 2. CALCAREOUS CONCRETION IN AEOLIAN LIMESTONE, +BERMUDAS.] + +[Illustration: FIG. 3. CALCAREOUS CONCRETION IN AEOLIAN LIMESTONE, +BERMUDAS.] + +[Illustration: FIG. 4. CALCAREOUS CONCRETION, BERMUDAS.] + +[Illustration: FIG. 5. CALCAREOUS CONCRETION IN AEOLIAN LIMESTONE, +BERMUDAS.] + +The form given in Fig. 1 is the most characteristic, and probably by +far the most common; but very frequently one of a group of these, one +which is evidently essentially the same as the rest and formed in the +same way, has an oval or an irregular shape (Figs. 2, 3, and 4). In +these we have the same raised border, the same scars on the outside, +the same origins of root-like fibres, and the same pitting of the +bottom of the shallow cup; but their form precludes the possibility of +their being tree-roots. In some cases (Fig. 5), a group of so-called +"palm-stems" is inclosed in a space surrounded by a ridge, and on +examining it closely this outer ridge is found to show the same +leaf-scars and traces of rootlets as the "palm-stems" themselves. In +some cases very irregular honey-combed figures are produced which the +examination of a long series of intermediate forms shows to belong to +the same category (Fig. 6). + +[Illustration: FIG. 6. CONCRETIONS IN AEOLIAN ROCKS, BERMUDAS.] + +In the caves in the limestone, owing to a thread of water having found +its way in a particular direction through the porous stone of the +roof, a drop falls age after age on one spot on the cave-floor, +accurately directed by the stalactite which it is all the time +creating. The water contains a certain proportion of carbonate of +lime, which is deposited as stalagmite as the water evaporates, and +thus a ring-like crust is produced at a little distance from the spot +where the drop falls. When a ring is once formed, it limits the spread +of the drop, and determines the position of the wall bounding the +little pool made by the drop. The floor of the cave gradually rises by +the accumulation of sand and travertine, and with it rise the walls +and floor of the cup by the deposit of successive layers of stalagmite +produced by the drop percolating into the limestone of the floor which +hardens it still further, but in this peculiar symmetrical way. From +the floor and sides of the cup the water oozes into the softer +limestone around and beneath; but, as in all these limestones, it does +not ooze indiscriminately, but follows certain more free paths. These +become soon lined and finally blocked with stalagmite, and it is +these tubes and threads of stalagmite which afterwards in the +pseudo-fossil represent the diverging rootlets. + +[Illustration: A STALAGMITE CAVE.] + +Sometimes when two or more drops fall from stalactites close to one +another the cups coalesce (Figs. 2, 3, and 4); sometimes one drop or +two is more frequent than the other, and then we have the form shown +in Figs. 3 and 4; sometimes many drops irregularly scattered form a +large pool with its raised border, and a few drops more frequent and +more constant than the rest grow their "palmetto stems" within its +limit (Fig. 5); and sometimes a number of drops near one another make +a curious regular pattern, with the partitions between the recesses +quite straight (Fig. 6). + +I have already referred to the rapid denudation which is going on in +these islands, and to the extent to which they have been denuded +within comparatively recent times. The floors of caves, from their +being cemented into a nearly homogeneous mass by stalagmitic matter, +are much harder than the ordinary porous blown limestone; and it seems +that in many cases, after the rocks forming the walls and roof have +been removed, disintegration has been at all events temporarily +arrested by the floor. Where there is a flat surface of rock exposed +anywhere on the island, it very generally bears traces of having been +at one time the floor of a cave; and as the weather-wearing of the +surface goes on, the old concretionary structures are gradually +brought out again, the parts specially hardened by a localized slow +infiltration of lime resist integration longest and project above the +general surface. Often a surface of weathered rock is so studded with +these symmetrical concretions, that it is hard to believe that one is +not looking at the calcified stumps of a close-growing grove of palms. + +[Illustration] + + + + +THE BIG TREES OF CALIFORNIA + +(FROM STUDIES SCIENTIFIC AND SOCIAL.) + +BY ALFRED RUSSEL WALLACE. + + +[Illustration] + +In the popular accounts of these trees it is usual to dwell only on +the dimensions of the very largest known specimens, and sometimes even +to exaggerate these. Even the smaller full-grown trees, however, are +of grand dimensions, varying from fourteen to eighteen feet in +diameter, at six feet above the ground, and keeping nearly the same +thickness for perhaps a hundred feet. In the south Calaveras grove, +where there are more than a thousand trees, the exquisite beauty of +the trunks is well displayed by the numerous specimens in perfect +health and vigor. The bark of these trees, seen at a little distance, +is of a bright orange brown tint, delicately mottled with darker +shades, and with a curious silky or plush-like gloss, which gives them +a richness of color far beyond that of any other conifer. The tree +which was cut down soon after the first discovery of the species, the +stump of which is now covered with a pavilion, is twenty-five feet in +diameter at six feet above the ground, but this is without the thick +bark, which would bring it to twenty-seven feet when alive. A +considerable portion of this tree still lies where it fell, and at one +hundred and thirty feet from the base I found it to be still twelve +and a half feet in diameter (or fourteen feet with the bark), while at +the extremity of the last piece remaining, two hundred and fifteen +feet from its base, it is six feet in diameter, or at least seven feet +with the bark. The height of this tree when it was cut down is not +recorded, but as one of the living trees is more than three hundred +and sixty feet high, it is probable that this giant was not much short +of four hundred feet. + +[Illustration: THE "MOTHER OF THE FOREST."] + +In the accompanying picture the dead tree in the centre is that from +which the bark was stripped, which was erected in the Crystal Palace +and unfortunately destroyed by fire. It is called the "Mother of the +Forest." The two trees nearer the foreground are healthy, medium-sized +trees, about fifteen feet diameter at six feet above the ground. + +The huge decayed trunk called "Father of the Forest," which has fallen +perhaps a century or more, exhibits the grandest dimensions of any +known tree. By measuring its remains, and allowing for the probable +thickness of the bark, it seems to have been about thirty-five feet +diameter near the ground, at ninety feet up fifteen feet, and even at +a height of two hundred and seventy feet, it was nine feet in +diameter. It is within the hollow trunk of this tree that a man on +horse-back can ride--both man and horse being rather small; but the +dimensions undoubtedly show that it was considerably larger than the +"Pavilion tree," and that it carried its huge dimensions to a greater +altitude; and although this does not prove it to have been much +taller, yet it was in all probability more than four hundred feet in +height. + +[Illustration] + +Very absurd statements are made to visitors as to the antiquity of +these trees, three or four thousand years being usually given as their +age. This is founded on the fact that while many of the large Sequoias +are greatly damaged by fire, the large pines and firs around them are +quite uninjured. As many of these pines are assumed to be near a +thousand years old, the epoch of the "great fire" is supposed to be +earlier still, and as the Sequoias have not outgrown the fire-scars in +all that time, they are supposed to have then arrived at their full +growth. But the simple explanation of these trees alone having +suffered so much from fire is, that their bark is unusually thick, +dry, soft, and fibrous, and it thus catches fire more easily and +burns more readily and for a longer time than that of the other +coniferæ. Forest fires occur continually, and the visible damage done +to these trees has probably all occurred in the present century. +Professor C.B. Bradley, of the University of California, has carefully +counted the rings of annual growth on the stump of the "Pavilion +tree," and found them to be twelve hundred and forty; and after +considering all that has been alleged as to the uncertainty of this +mode of estimating the age of a tree, he believes that in the climate +of California, in the zone of altitude where these trees grow, the +seasons of growth and repose are so strongly marked that the number of +annual rings gives an accurate result. + +Other points that have been studied by Professor Bradley are, the +reason why there are so few young trees in the groves, and what is the +cause of the destruction of the old trees. To take the last point +first, these noble trees seem to be singularly free from disease or +from decay due to old age. All the trees that have been cut down are +solid to the heart, and none of the standing trees show any +indications of natural decay. The only apparent cause for their +overthrow is the wind, and by noting the direction of a large number +of fallen trees it is found that the great majority of them lie more +or less towards the south. This is not the direction of the prevalent +winds, but many of the tallest trees lean towards the south, owing to +the increased growth of their topmost branches towards the sun. They +are then acted upon by violent gales, which loosen their roots, and +whatever the direction of the wind that finally overthrows them, they +fall in the direction of the over-balancing top weight. The young +trees grow spiry and perfectly upright, but as soon as they overtop +the surrounding trees and get the full influence of the sun and wind, +the highest branches grow out laterally, killing those beneath their +shade, and thus a dome-shaped top is produced. Taking into +consideration the health and vigor of the largest trees, it seems +probable that, under favorable conditions of shelter from violent +winds, and from a number of trees around them of nearly equal height, +big trees might be produced far surpassing in height and bulk any that +have yet been discovered. It is to be hoped that if any such are found +to exist in the extensive groves of these trees to the south of those +which are alone accessible to tourists, the Californian Government +will take steps to reserve a considerable tract containing them, for +the instruction and delight of future generations. + +The scarcity of young Sequoias strikes every visitor, the fact being +that they are only to be found in certain favored spots. These are, +either where the loose débris of leaves and branches which covers the +ground has been cleared away by fire, or on the spots where trees have +been uprooted. Here the young trees grow in abundance, and serve to +replace those that fall. The explanation of this is, that during the +long summer drought the loose surface débris is so dried up that the +roots of the seedling Sequoias perish before they can penetrate the +earth beneath. They require to germinate on the soil itself, and this +they are enabled to do when the earth is turned up by the fall of a +tree, or where a fire has cleared off the débris. They also flourish +under the shade of the huge fallen trunks in hollow places, where +moisture is preserved throughout the summer. Most of the other +conifers of these forests, especially the pines, have much larger +seeds than the Sequoias, and the store of nourishment in these more +bulky seeds enables the young plants to tide over the first summer's +drought. It is clear, therefore, that there are no indications of +natural decay in these forest giants. In every stage of their growth +they are vigorous and healthy, and they have nothing to fear except +from the destroying hand of man. + +[Illustration: REDWOOD TREE WITH TRIPLE TRUNK.] + +Destruction from this cause is, however, rapidly diminishing both the +giant Sequoia and its near ally the noble redwood (_Sequoia +sempervirens_), a tree which is more beautiful in foliage and in some +other respects more remarkable than its brother species, while there +is reason to believe that under favorable conditions it reaches an +equally phenomenal size. It once covered almost all the coast ranges +of central and northern California, but has been long since cleared +away in the vicinity of San Francisco, and greatly diminished +elsewhere. A grove is preserved for the benefit of tourists near Santa +Cruz, the largest tree being two hundred and ninety-six feet high, +twenty-nine feet diameter at the ground and fifteen feet at six feet +above it. One of these trees having a triple trunk is here figured +from a photograph. Much larger trees, however, exist in the great +forests of this tree in the northern part of the State; but these are +rapidly being destroyed for the timber, which is so good and durable +as to be in great demand. Hence Californians have a saying that the +redwood is too good a tree to live. On the mountains a few miles east +of the Bay of San Francisco, there are a number of patches of young +redwoods, indicating where large trees have been felled, it being a +peculiarity of this tree that it sends up vigorous young plants from +the roots of old ones immediately around the base. Hence in the +forests these trees often stand in groups arranged nearly in a circle, +thus marking out the size of the huge trunks of their parents. It is +from this quality that the tree has been named _sempervirens_, or ever +flourishing. Dr. Gibbons, of Alameda, who has explored all the remains +of the redwood forests in the neighborhood of Oakland, kindly took me +to see the old burnt-out stump of the largest tree he had discovered. +It is situated about fifteen hundred feet above the sea, and is +thirty-four feet in diameter at the ground. This is as large as the +very largest specimens of the _Sequoia gigantea_, but it may have +spread out more at the base and have been somewhat smaller above, +though this is not a special characteristic of the species. + +[Illustration] + + + + +WHAT IS EVOLUTION? + +(FROM THE ATLANTIC MONTHLY, MARCH, '93.) + +BY PROFESSOR E.S. HOLDEN. + + +[Illustration] + +I was once trying to tell a boy, a friend of mine, what the scientific +men mean by the long word _Evolution_, and to give him some idea of +the plan of the world. I wanted an illustration of something that had +grown--evolved, developed--from small beginnings up through more and +more complicated forms, till it had reached some very complete form. I +could think of no better example than the railway by which we were +sitting. The trains were running over the very track where a +wagon-road had lately been, and before that a country cart-track, and +before that a bridle-path, and before that again a mere trail for +cattle. So I took the road for an example, and tried to show my boy +how it had grown from little things by slow degrees according to laws; +and if you like, I will try to tell it again. + +Just as one can go further and further back, and always find a bird to +be the parent of the egg, and an egg to be the parent of that bird, so +in the history of this road of ours; we may go back and back into the +past, always finding something earlier, which is the cause of the +something later. The earth, the planets, and the sun were all a fiery +mist long ago. And in that mist, and in what came before it, we may +look for the origin of things as they are. But we must begin +somewhere. Let us begin with the landscape as we see it now,--hills, +valleys, streams, mountains, grass,--but with only a single tree. + +We will not try to say how the tree came there. At least, we will not +try just yet. When we are through with the story you can say just as +well as I can. + +Suppose, then, a single oak-tree stood just on that hillside thousands +and thousands of years ago. Grass was growing everywhere, and flowers, +too. The seeds came with the winds. Year after year the oak-tree bore +its acorns, hundreds and hundreds of them, and they fell on the grass +beneath and rolled down the smooth slopes, and sprouted as best they +could,--most of them uselessly so far as producing trees were +concerned,--but each one did its duty and furnished its green sprout, +and died if it found no nourishment. + +All the hundreds of acorns rolled down the slopes, Not one rolled up; +and here was a _law_,--the law of gravitation,--in full activity. +There were scores of other laws active, too; for evolution had gone a +long way when we had an earth fit to be lived on, and hills in their +present shape, and a tree bearing acorns that would reproduce their +kind. But ever since the fiery mist this simple law of gravitation has +been acting, binding the whole universe together, making a +relationship between each clod and every other clod, and forcing +every stone, every acorn, and every rain-drop to move down and not up. + +Just as this law operates,--continuously, silently, inexorably,--so +every other law makes itself felt in its own sphere. Gravitation is +simple. The law according to which an acorn makes an oak--and not a +pine-tree is complex. But the laws of Nature are all alike, and if we +understand the simple ones, we can at least partly comprehend the more +complex. They are nothing but fixed habits on a large scale. + +So the acorns fell year by year and sprouted; and one out of a +thousand found good soil, and was not wasted, and made a tree. And so +all around (below) the tree with which we started there grew a grove +of oaks like it, in fact its children; and finally the original trees +died, but not without having left successors. + +First of all, the green hillside is smooth and untrodden. There is +nothing but grass and flowers, borne there by the winds, which leave +no track. There is no animal life even in this secluded spot save the +birds, and they too leave no track. By and by there comes a hard +winter, or a dearth of food, and a pair of stray squirrels emigrate +from their home in the valley below; and the history of our hill and +its woods begins. Mere chance decides the choice of the particular +oak-tree in which the squirrels make their home. From the foot of this +tree they make excursions here and there for their store of winter +food,--acorns and the like,--and they leave little paths on the +hillside from tree to tree. + +The best-marked paths run to the places where there are the most +acorns. A little later on there are more squirrels in the colony,--the +young of the parent pair, and other colonists from the valley. The +little tracks become plainer and plainer. + +Later still come other wild animals in search of food,--squirrels will +do. The wild animals do not remain in the colony (there are too few +squirrels, and they are too hard to catch), but they pass through it, +sometimes by day but oftenest by night. + +You might think it was perfectly a matter of chance along which path a +bear or a wolf passed, but it was not. He _could_ walk anywhere on the +hillside; and sometimes he would be found far out of the paths that +the squirrels had begun. But usually, when he was in no haste, he took +the easiest path. The easiest one was that which went between the +bushes and not through them; along the hillside and not straight up +it; around the big rocks and not over them. The wolves and bears and +foxes have new and different wants when they come; and they break new +paths to the springs where they drink, to the shade where they lie, to +the hollow trees where the bees swarm and store the wild honey. + +But the squirrels were the first surveyors of these tracks. The bears +and wolves are the engineers, who change the early paths to suit their +special convenience. + +By and by the Indian hunter comes to follow the wild game. He, too, +takes the easiest trail, the path of least resistance; and he follows +the track to the spring that the deer have made, and he drinks there. +He is an animal as they are, and he satisfies his animal wants +according to the same law that governs them. + +After generations of hunters, Indians, and then white men, there comes +a man on horseback looking for a house to live in. He, too, follows +along the easiest paths and stops at the spring; and near by he finds +the place he is looking for. Soon he returns, driving before him herds +of cattle and flocks of sheep, which spread over the grassy glades to +feed. But everywhere they take the easiest place, the old paths, from +the shady tree to the flowing spring. After awhile the hillside is +plainly marked with these sheep trails. You can see them now whenever +you go into the country, on every hillside. + +Soon there are neighbors who build their homes in the next valley, and +a good path must be made between the different houses. + +A few days' work spent in moving the largest stones, in cutting down +trees, and in levelling off a few steep slopes, makes a trail along +which you can gallop your horse. + +Things move fast now,--history begins to be made quickly as soon as +man takes a hand in it. Soon the trail is not enough: it must be +widened so that a wagon-load of boards for a new house can be carried +in (for the settler has found a wife). After the first cart-track is +made to carry the boards and shingles in, a better road will be needed +to haul firewood and grain out (for the wants of the new family have +increased, and things must be bought in the neighboring village with +money, and money can only be had by selling the products of the farm). +By and by the neighborhood is so well inhabited that it is to the +advantage of the villages all around it to have good and safe and easy +roads there; and the road is declared a public one, and it is +regularly kept in repair and improved at the public expense. Do not +forget the squirrels of long ago. They were the projectors of this +road. Their successors use it now,--men and squirrels alike,--and stop +at the spring to drink, and under the huge oaks to rest. + +A few years more, and it becomes to the advantage of all to have a +railway through the valley and over the hillside. Then a young +surveyor, just graduated from college, comes with his chain-men and +flag-men, and finds that the squirrels, and bears, and hunters, and +all the rest have picked out the easiest way for him long centuries +ago. He makes his map, and soon the chief enigneer and the president +of the road drive along in a buggy with a pair of fast horses +(frightening the little squirrels off their road-way and into their +holes), and the route of the Bear Valley and Quercus Railway is +finally selected, and here it is. See! there comes a train along the +track. This is the way a railway route grew out of a squirrel path. +There are thousands of little steps, but you can trace them, or +imagine them, as well as I can tell you. + +It is the same all over the world. Stanley cut a track through the +endless African forests. But it lay between the Pygmy villages, along +the paths they had made, and through the glades where they fought +their battles with the storks. + +Sometimes the first road is a river--the track is already cut. Try to +find out where the settlements in America were in the very early +days--before 1800. You will find them along the Hudson, the Juanita, +the St. Lawrence, the James, the Mississippi Rivers. But when these +are left, men follow the squirrel-tracks and bear-tracks, or the +paths of hunters, or the roads of Roman soldiers. It is a standing +puzzle to little children why all the great rivers flow past the great +towns. (Why do they?) The answer to that question will tell you why +the great battles are fought in the same regions; why Egypt has been +the coveted prize of a dozen different conquerors (it is the gateway +of the East); why our Civil War turned on the possession of the +Mississippi River. It is the roadways we fight for, the ways in and +out, whether they be land or water. Of course, we really fought for +something better than the mere possession of a roadway, but to get +what we fought for we had to have the roadway first. + +The great principle at the bottom of everything in Nature is that the +fittest survives: or, as I think it is better to say it, in any +particular conflict or struggle that thing survives which is the +fittest to survive _in this particular struggle_. This is Mr. Darwin's +discovery,--or one of them,--and the struggle for existence is a part +of the great struggle of the whole universe, and the laws of it make +up the methods of Evolution--of Development. + +It is clear now, is it not, how the railway route is the direct +descendant of the tiny squirrel track between two oaks? The process of +development we call Evolution, and you can trace it all around you. +Why are your skates shaped in a certain way? Why is your gun rifled? +Why have soldiers two sets of (now) useless buttons on the skirts of +their coats? (I will give you three guesses for this, and the hint +that you must think of cavalry soldiers.) Why are eagles' wings of +just the size that they are? These and millions of like questions are +to be answered by referring to the principle of development. + +Sometimes it is hard to find the clew. Sometimes the development has +gone so far, and the final product has become so complex and special, +that it takes a good deal of thinking to find out the real reasons. +But they _can_ be found, whether they relate to a fashion, to one of +the laws of our country, or to the colors on a butterfly's wing. + +There is a little piece of verse intended to be comic, which, on the +contrary, is really serious and philosophical, if you understand it. +Learn it by heart, and apply it to all kinds and conditions of things, +and see if it does not help you to explain them to yourself.... + + "And Man grew a thumb for that he had need of it, + And developed capacities for prey. + For the fastest men caught the most animals, + And the fastest animals got away from the most men. + Whereby all the slow animals were eaten, + And all the slow men starved to death." + +[Illustration] + + + + +HOW THE SOIL IS MADE + +(FROM THE FORMATION OF VEGETABLE MOULD.) + +BY CHARLES DARWIN. + + +[Illustration: W] + +Worms have played a more important part in the history of the world +than most persons would at first suppose. In almost all humid +countries they are extraordinarily numerous, and for their size +possess great muscular power. In many parts of England a weight of +more than ten tons (10,516 kilogrammes) of dry earth annually passes +through their bodies and is brought to the surface on each acre of +land; so that the whole superficial bed of vegetable mould passes +through their bodies in the course of every few years. From the +collapsing of the old burrows the mould is in constant though slow +movement, and the particles composing it are thus rubbed together. By +these means fresh surfaces are continually exposed to the action of +the carbonic acid in the soil, and of the humus-acids which appear to +be still more efficient in the decomposition of rocks. The generation +of the humus-acids is probably hastened during the digestion of the +many half-decayed leaves which worms consume. Thus the particles of +earth, forming the superficial mould, are subjected to conditions +eminently favorable for their decomposition and disintegration. +Moreover, the particles of the softer rocks suffer some amount of +mechanical trituration in the muscular gizzards of worms, in which +small stones serve as mill-stones. + +[Illustration: DIAGRAM OF THE ALIMENTARY CANAL OF AN EARTH-WORM.] + +The finely levigated castings, when brought to the surface in a moist +condition, flow during rainy weather down any moderate slope; and the +smaller particles are washed far down even a gently inclined surface. +Castings when dry often crumble into small pellets and these are apt +to roll down any sloping surface. Where the land is quite level and is +covered with herbage, and where the climate is humid so that much dust +cannot be blown away, it appears at first sight impossible that there +should be any appreciable amount of sub-aerial denudation; but worm +castings are blown, especially while moist and viscid, in one uniform +direction by the prevalent winds which are accompanied by rain. By +these several means the superficial mould is prevented from +accumulating to a great thickness; and a thick bed of mould checks in +many ways the disintegration of the underlying rocks and fragments of +rock. + +[Illustration: A WORM CASTING, FROM NICE. (Natural Size.)] + +The removal of worm-castings by the above means leads to results which +are far from insignificant. It has been shown that a layer of earth,.2 +of an inch in thickness, is in many places annually brought to the +surface per acre; and if a small part of this amount flows, or rolls, +or is washed, even for a short distance, down every inclined surface, +or is repeatedly blown in one direction, a great effect will be +produced in the course of ages. It was found by measurements and +calculations that on a surface with a mean inclination of 9° 26', 2.4 +cubic inches of earth which had been ejected by worms crossed, in the +course of a year, a horizontal line one yard in length; so that two +hundred and forty cubic inches would cross a line one hundred yards in +length. This latter amount in a damp state would weigh eleven and +one-half pounds. Thus, a considerable weight of earth is continually +moving down each side of every valley, and will in time reach its bed. +Finally, this earth will be transported by the streams flowing in the +valleys into the ocean, the great receptacle for all matter denuded +from the land. It is known from the amount of sediment annually +delivered into the sea by the Mississippi, that its enormous +drainage-area must on an average be lowered.00263 of an inch each +year; and this would suffice in four and a half million years to lower +the whole drainage-area to the level of the seashore. So that if a +small fraction of the layer of fine earth,.2 of an inch in thickness, +which is annually brought to the surface by worms, is carried away, a +great result cannot fail to be produced within a period which no +geologist considers extremely long. + +[Illustration: SECTION THROUGH ONE OF THE DRUIDICAL STONES AT +STONEHENGE, SHOWING HOW MUCH IT HAD SUNK INTO THE GROUND. + +(Scale, 1/2 inch to 1 foot.)] + +Archaeologists ought to be grateful to worms, as they protect and +preserve for an indefinitely long period every object, not liable to +decay, which is dropped on the surface of the land, by burying it +beneath their castings. Thus, also, many elegant and curious +tesselated pavements and other ancient remains have been preserved; +though no doubt the worms have in these cases been largely aided by +earth washed and blown from the adjoining land, especially when +cultivated. The old tesselated pavements have, however, often suffered +by having subsided unequally from being unequally undermined by the +worms. Even old massive walls may be undermined and subside; and no +building is in this respect safe, unless the foundations lie six or +seven feet beneath the surface, at a depth at which worms cannot work. +It is probable that many monoliths and some old walls have fallen +down from having been undermined by worms. + +Worms prepare the ground in an excellent manner for the growth of +fibrous-rooted plants and for seedlings of all kinds. They +periodically expose the mould to the air, and sift it so that no +stones larger than the particles which they can swallow are left in +it. They mingle the whole intimately together, like a gardener who +prepares fine soil for his choicest plants. In this state it is well +fitted to retain moisture and to absorb all soluble substances, as +well as for the process of nitrification. The bones of dead animals, +the harder parts of insects, the shells of land mollusks, leaves, +twigs, etc., are before long all buried beneath the accumulated +castings of worms, and are thus brought in a more or less decayed +state within reach of the roots of plants. Worms likewise drag an +infinite number of dead leaves and other parts of plants into their +burrows, partly for the sake of plugging them up and partly as food. + +The leaves which are dragged into the burrows as food, after being +torn into the finest shreds, partially digested and saturated with the +intestinal and urinary secretions, are commingled with much earth. +This earth forms the dark-colored, rich humus which almost everywhere +covers the surface of the land with a fairly well-defined layer or +mantle. Von Hensen placed two worms in a vessel eighteen inches in +diameter, which was filled with sand, on which fallen leaves were +strewed; and these were soon dragged into their burrows to a depth of +three inches. After about six weeks an almost uniform layer of sand, a +centimetre (.4 inch) in thickness, was converted into humus by having +passed through the alimentary canals of these two worms. It is +believed by some persons that worm-burrows, which often penetrate the +ground almost perpendicularly to a depth of five or six feet, +materially aid in its drainage; notwithstanding that the viscid +castings piled over the mouths of the burrows prevent or check the +rain-water directly entering them. They allow the air to penetrate +deeply into the ground. They also greatly facilitate the downward +passage of roots of moderate size; and these will be nourished by the +humus with which the burrows are lined. Many seeds owe their +germination to having been covered by castings; and others buried to a +considerable depth beneath accumulated castings lie dormant, until at +some future time they are accidentally uncovered and germinate. + +[Illustration: A WORM CASTING FROM SOUTH INDIA. (Natural Size.)] + +Worms are poorly provided with sense-organs, for they cannot be said +to see, although they can just distinguish between light and darkness; +they are completely deaf, and have only a feeble power of smell; the +sense of touch alone is well developed. They can, therefore, learn +little about the outside world, and it is surprising that they should +exhibit some skill in lining their burrows with their castings and +with leaves, and in the case of some species in piling up their +castings into tower-like constructions. But it is far more surprising +that they should apparently exhibit some degree of intelligence +instead of a mere blind, instinctive impulse, in their manner of +plugging up the mouths of their burrows. They act in nearly the same +manner as would a man, who had to close a cylindrical tube with +different kinds of leaves, petioles, triangles of paper, etc., for +they commonly seize such objects by their pointed ends. But with thin +objects a certain number are drawn in by their broader ends. They do +not act in the same unvarying manner in all cases, as do most of the +lower animals; for instance, they do not drag in leaves by their +foot-stalks, unless the basil part of the blade is as narrow as the +apex, or narrower than it. + + * * * * * + +When we behold a wide, turf-covered expanse, we should remember that +its smoothness, on which so much of its beauty depends, is mainly due +to all the inequalities having been slowly levelled by worms. It is a +marvellous reflection that the whole of the superficial mould over any +such expanse has passed, and will again pass, every few years through +the bodies of worms. The plough is one of the most ancient and most +valuable of man's inventions; but long before he existed the land was +in fact regularly ploughed, and, still continues to be thus ploughed +by earth-worms. It may be doubted whether there are many other animals +which have played so important a part in the history of the world, as +have these lowly organized creatures. Some other animals, however, +still more lowly organized, namely, corals, have done far more +conspicuous work in having constructed innumerable reefs and islands +in the great oceans; but these are almost confined to the tropical +zones. + +[Illustration] + + + + +ZOÖLOGICAL MYTHS + +(FROM FACTS AND FICTIONS OF ZOÖLOGY.) + +BY ANDREW WILSON. + + +[Illustration] + +When the country swain, loitering along some lane, comes to a +standstill to contemplate, with awe and wonder, the spectacle of a +mass of the familiar "hair-eels" or "hair-worms" wriggling about in a +pool, he plods on his way firmly convinced that, as he has been taught +to believe, he has just witnessed the results of the transformation of +some horse's hairs into living creatures. So familiar is this belief +to people of professedly higher culture than the countryman, that the +transformation just alluded to has to all, save a few thinking persons +and zoölogists, become a matter of the most commonplace kind. When +some quarrymen, engaged in splitting up the rocks, have succeeded in +dislodging some huge mass of stone, there may sometimes be seen to hop +from among the débris a lively toad or frog, which comes to be +regarded by the excavators with feelings akin to those of +superstitious wonder and amazement. The animal may or may not be +captured; but the fact is duly chronicled in the local newspapers, and +people wonder for a season over the phenomenon of a veritable Rip Van +Winkle of a frog, which to all appearance, has lived for "thousands of +years in the solid rock." Nor do the hair-worm and the frog stand +alone in respect of their marvellous origin. Popular zoölogy is full +of such marvels. We find unicorns, mermaids, and mermen; geese +developed from the shell-fish known as "barnacles"; we are told that +crocodiles may weep, and that sirens can sing--in short, there is +nothing so wonderful to be told of animals that people will not +believe the tale. Whilst, curiously enough, when they are told of +veritable facts of animal life, heads begin to shake and doubts to be +expressed, until the zoölogist despairs of educating people into +distinguishing fact from fiction, and truth from theories and +unsupported beliefs. The story told of the old lady, whose youthful +acquaintance of seafaring habits entertained her with tales of the +wonders he had seen, finds, after all, a close application in the +world at large. The dame listened with delight, appreciation, and +belief, to accounts of mountains of sugar and rivers of rum, and to +tales of lands where gold and silver and precious stones were more +than plentiful. But when the narrator descended to tell of fishes that +were able to raise themselves out of the water in flight, the old +lady's credulity began to fancy itself imposed upon; for she +indignantly repressed what she considered the lad's tendency to +exaggeration, saying, "Sugar mountains may be, and rivers of rum may +be, but fish that flee ne'er can be!" Many popular beliefs concerning +animals partake of the character of the old lady's opinions regarding +the real and fabulous; and the circumstance tells powerfully in favor +of the opinion that a knowledge of our surroundings in the world, and +an intelligent conception of animal and plant life, should form part +of the school-training of every boy and girl, as the most effective +antidote to superstitions and myths of every kind. + + +[Illustration: FLYING FISH.] + +The tracing of myths and fables is a very interesting task, and it +may, therefore, form a curious study, if we endeavor to investigate +very briefly a few of the popular and erroneous beliefs regarding +lower animals. The belief regarding the origin of the hair-worms is +both widely spread and ancient. Shakespeare tells us that + + "Much, is breeding + Which, like the courser's hair, hath, yet but life, + And not a serpent's poison." + +The hair-worms certainly present the appearance of long, delicate +black hairs, which move about with great activity amidst the mud of +pools and ditches. These worms, in the early stages of their +existence, inhabit the bodies of insects, and may be found coiled up +within the grasshopper, which thus gives shelter to a guest exceeding +many times the length of the body of its host. Sooner or later the +hair-worm, or _Gordius aquaticus_ as the naturalist terms it, leaves +the body of the insect, and lays its eggs, fastened together in long +strings, in water. From each egg a little creature armed with minute +hooks is produced, and this young hair-worm burrows its way into the +body of some insect, there to repeat the history of its parent. Such +is the well-ascertained history of the hair-worm, excluding entirely +the popular belief in its origin. There certainly does exist in +science a theory known as that of "spontaneous generation," which, in +ancient times, accounted for the production of insects and other +animals by assuming that they were produced in some mysterious fashion +out of lifeless matter. But not even the most ardent believer in the +extreme modification of this theory which holds a place in modern +scientific belief, would venture to maintain the production of a +hair-worm by the mysterious vivification of an inert substance such as +a horse's hair. + +The expression "crocodile's tears" has passed into common use, and it +therefore may be worth while noting the probable origin of this myth. +Shakespeare, with that wide extent of knowledge which enabled him to +draw similes from every department of human thought, says that + + "Gloster's show + Beguiles him, as the mournful crocodile + With sorrow snares relenting passengers." + +The poet thus indicates the belief that not only do crocodiles shed +tears, but that sympathizing passengers, turning to commiserate the +reptile's woes, are seized and destroyed by the treacherous creatures. +That quaint and credulous old author--the earliest writer of English +prose--Sir John Mandeville, in his "Voiage," or account of his +"Travile," published about 1356--in which, by the way, there are to be +found accounts of not a few wonderful things in the way of zoölogical +curiosities--tells us that in a certain "contre and be all yonde, ben +great plenty of Crokodilles, that is, a manner of a long Serpent as I +have seyed before." He further remarks that "these Serpents slew men," +and devoured them, weeping; and he tells us, too, that "whan thei +eaten thei meven (move) the over jowe (upper jaw), and nought the +nether (lower) jowe: and thei have no tonge (tongue)." Sir John thus +states two popular beliefs of his time and of days prior to his age, +namely, that crocodiles move their upper jaws, and that a tongue was +absent in these animals. + +[Illustration: CROCODILE.] + +As regards the tears of the crocodile, no foundation of fact exists +for the belief in such sympathetic exhibitions. But a highly probable +explanation may be given of the manner in which such a belief +originated. These reptiles unquestionably emit very loud and +singularly plaintive cries, compared by some travellers to the +mournful howling of dogs. The earlier and credulous travellers would +very naturally associate tears with these cries, and, once begun, the +supposition would be readily propagated, for error and myth are ever +plants of quick growth. The belief in the movement of the upper jaw +rests on apparent basis of fact. The lower jaw is joined to the skull +very far back on the latter, and the mouth-opening thus comes to be +singularly wide; whilst, when the mouth opens, the skull and upper jaw +are apparently observed to move. This is not the case, however; the +apparent movement arising from the manner in which the lower jaw and +the skull are joined together. The belief in the absence of the tongue +is even more readily explained. When the mouth is widely opened, no +tongue is to be seen. This organ is not only present, but is, +moreover, of large size; it is, however, firmly attached to the floor +of the mouth, and is specially adapted, from its peculiar form and +structure, to assist these animals in the capture and swallowing of +their prey. + +One of the most curious fables regarding animals which can well be +mentioned, is that respecting the so-called "Bernicle" or "Barnacle +Geese," which by the naturalists and educated persons of the Middle +Ages were believed to be produced by those little Crustaceans named +"Barnacles." With the "Barnacles" every one must be familiar who has +examined the floating driftwood of the sea-beach, or who has seen +ships docked in a seaport town. A barnacle is simply a kind of crab +enclosed in a triangular shell, and attached by a fleshy stalk to +fixed objects. If the barnacle is not familiar to readers, certain +near relations of these animals must be well known, by sight at least, +as amongst the most familiar denizens of our sea-coast. These latter +are the "Sea-Acorn," or Balani, whose little conical shells we crush +by hundreds as we walk over the rocks at low-water mark; whilst every +wooden pile immersed in the sea becomes coated in a short time with a +thick crust of the "Sea-Acorns." If we place one of these little +animals, barnacle, or sea-acorn--the latter wanting the stalk of the +former--in its native waters, we shall observe a beautiful little +series of feathery plumes to wave backward and forward, and ever and +anon to be quickly withdrawn into the secure recesses of the shell. +These organs are the modified feet of the animal, which not only serve +for sweeping food-particles into the mouth, but act also as +breathing-organs. We may, therefore, find it a curious study to +inquire through what extraordinary transformation and confusion of +ideas such an animal could be credited with giving origin to a +veritable goose; and the investigation of the subject will also afford +a singularly apt illustration of the ready manner in which the fable +of one year or period becomes transmitted and transformed into the +secure and firm belief of the next. + +We may begin our investigation by inquiring into some of the opinions +which were entertained on this subject and ventilated by certain old +writers. Between 1154 and 1189 Giraldus Cambrensis, in a work entitled +"Topographia Hiberniae," written in Latin, remarks concerning "many +birds which are called Bernacae: against nature, nature produces them +in a most extraordinary way. They are like marsh geese, but somewhat +smaller. They are produced from fir timber tossed along the sea, and +are at first like gum. Afterward they hang down by their beaks, as if +from a seaweed attached to the timber, surrounded by shells, in order +to grow more freely," Giraldus is here evidently describing the +barnacles themselves. He continues: "Having thus, in process of time, +been clothed with a strong coat of feathers, they either fall into the +water or fly freely away into the air. They derive their food and +growth from the sap of the wood or the sea, by a secret and most +wonderful process of alimentation. I have frequently, with my own +eyes, seen more than a thousand of these small bodies of birds, +hanging down on the seashore from one piece of timber, enclosed in +shells, and already formed." Here, again, our author is speaking of +the barnacles themselves, with which he naturally confuses the geese, +since he presumes the Crustaceans are simply geese in an undeveloped +state. He further informs his readers that, owing to their presumably +marine origin, "bishops and clergymen in some parts of Ireland do not +scruple to dine off these birds at the time of fasting, because they +are not flesh, nor born of flesh," although for certain other and +theological reasons, not specially requiring to be discussed in the +present instance, Giraldus disputes the legality of this practice of +the Hibernian clerics. + +In the year 1527 appeared "The Hystory and Croniclis of Scotland, with +the cosmography and dyscription thairof, compilit be the noble Clerk +Maister Hector Boece, Channon of Aberdene." Boece's "History" was +written in Latin; the title we have just quoted being that of the +English version of the work (1540), which title further sets forth +that Boece's work was "Translait laitly in our vulgar and commoun +langage be Maister Johne Bellenden, Archedene of Murray, And +Imprentit in Edinburgh, be me Thomas Davidson, prenter to the Kyngis +nobyll grace." In this learned work the author discredits the popular +ideas regarding the origin of the geese. "Some men belevis that thir +clakis (geese) growis on treis be the nebbis (bills). Bot thair +opinoun is vane. And becaus the nature and procreatioun of thir clakis +is strange, we have maid na lytyll laboure and deligence to serche ye +treuth and verite yairof, we have salit (sailed) throw ye seis quhare +thir clakis ar bred, and I fynd be gret experience, that the nature of +the seis is mair relevant caus of thair procreatioun than ony uthir +thyng." According to Boece, then, "the nature of the seis" formed the +chief element in the production of the geese, and our author proceeds +to relate how "all treis (trees) that ar casein in the seis be proces +of tyme apperis first wormeetin (worm-eaten), and in the small boris +and hollis (holes) thairof growis small worms." Our author no doubt +here alludes to the ravages of the Teredo, or ship-worm, which burrows +into timber, and with which the barnacles themselves are thus +confused. Then he continues, the "wormis" first "schaw (show) thair +heid and feit, and last of all thay schaw thair plumis and wyngis. +Finaly, quhen thay ar cumyn to the just mesure and quantite of geis, +thay fle in the aire as othir fowlis dois, as was notably provyn, in +the yeir of God ane thousand iii hundred lxxxx, in sicht of mony +pepyll, besyde the castell of Petslego." On the occasion referred to, +Boece tells us that a great tree was cast on shore, and was divided, +by order of the "laird" of the ground, by means of a saw. Wonderful to +relate, the tree was found not merely to be riddled with a "multitude +of wormis," throwing themselves out of the holes of the tree, but some +of the "wormis" had "baith heid, feit, and wyngis," but, adds the +author, "they had no fedderis (feathers)." + +Unquestionably, either "the scientific use of the imagination" had +operated in this instance in inducing the observers to believe that in +this tree, riddled by the ship-worms and possibly having barnacles +attached to it, they beheld young geese; or Boece had construed the +appearances described as those representing the embryo stages of the +barnacle geese. + +Boece further relates how a ship named the Christofir was brought to +Leith, and was broken down because her timbers had grown old and +failing. In these timbers were beheld the same "wormeetin" +appearances, "all the hollis thairof" being "full of geis." Boece +again most emphatically rejects the idea that the "geis" were produced +from the wood of which the timbers were composed, and once more +proclaims his belief that the "nature of the seis resolvit in geis" +may be accepted as the true and final explanation of their origin. A +certain "Maister Alexander Galloway" had apparently strolled with the +historian along the sea-coast, the former giving "his mynd with maist +ernist besynes to serche the verite of this obscure and mysty dowtis." +Lifting up a piece of tangle, they beheld the seaweed to be hanging +full of mussel-shells from the root to the branches. Maister Galloway +opened one of the mussel-shells, and was "mair astonis than afore" to +find no fish therein, but a perfectly shaped "foule, smal and gret," +as corresponded to the "quantity of the shell." And once again Boece +draws the inference that the trees or wood on which the creatures are +found have nothing to do with the origin of the birds; and that the +fowls are begotten of the "occeane see, quhilk," concludes our author, +"is the caus and production of mony wonderful thingis." + +More than fifty years after the publication of Boece's "History," old +Gerard of London, the famous "master in chirurgerie" of his day, gave +an account of the barnacle goose, and not only entered into minute +particulars of its growth and origin, but illustrated its manner of +production by means of the engraver's art of his day. Gerard's +"Herball," published in 1597, thus contains, amongst much that is +curious in medical lore, a very quaint piece of zoölogical history. He +tells us that "in the north parts of Scotland, and the Hands adjacent, +called Orchades (Orkneys)," are found "certaine trees, whereon doe +growe certaine shell fishes, of a white colour tending to russet; +wherein are conteined little living creatures: which shels in time of +maturitie doe open, and out of them grow those little living foules +whom we call Barnakles, in the north of England Brant Geese, and in +Lancashire tree Geese; but the other that do fall upon the land, +perish, and come to nothing: thus much by the writings of others, and +also from the mouths of people of those parts, which may," concludes +Gerard, "very well accord with truth." + +Not content with hearsay evidence, however, Gerard relates what his +eyes saw and hands touched. He describes how on the coasts of a +certain "small Hand in Lancashire called Pile of Foulders" (probably +Peel Island), the wreckage of ships is cast up by the waves, along +with the trunks and branches "of old and rotten trees." On these +wooden rejectamenta "a certaine spume or froth" grows, according to +Gerard. This spume "in time breedeth unto certaine shels, in shape +like those of the muskle, but sharper pointed, and of a whitish +color." This description, it may be remarked, clearly applies to the +barnacles themselves. Gerard then continues to point out how, when the +shell is perfectly formed, it "gapeth open, and the first thing that +appeereth is the foresaid lace or string"--the substance described by +Gerard as contained within the shell--"next come the legs of the Birde +hanging out; and as it groweth greater, it openeth the shell by +degrees, till at length it is all come forth, and hangeth only by the +bill; in short space after it commeth to full maturitie, and falleth +into the sea, where it gathereth feathers, and groweth to a foule, +bigger than a Mallard, and lesser than a Goose, having blacke legs and +bill or beake, and feathers blacke and white ... which the people of +Lancashire call by no other name than a tree Goose." + +[Illustration: FIG. 1. THE BARNACLE TREE. (From Gerard's "Herball.")] + +Accompanying this description is the engraving of the barnicle tree +(Fig. 1) bearing its geese progeny. From the open shells in two cases, +the little geese are seen protruding, whilst several of the +fully-fledged fowls are disporting themselves in the sea below. +Gerard's concluding piece of information, with its exordium, must not +be omitted. "They spawne," says the wise apothecary, "as it were, in +March or Aprill; the Geese are found in Maie or June, and come to +fulnesse of feathers in the moneth after. And thus hauing, through +God's assistance, discoursed somewhat at large of Grasses, Herbes, +Shrubs, Trees, Mosses, and certaine excrescences of the earth, with +other things moe incident to the Historic thereof, we conclude and end +our present volume, with this woonder of England. For which God's name +be euer honored and praised." It is to be remarked that Gerard's +description of the goose-progeny of the barnacle tree exactly +corresponds with the appearance of the bird known to ornithologists as +the "barnacle-goose"; and there can be no doubt that, skilled as was +this author in the natural history lore of his day, there was no other +feeling in his mind than that of firm belief in and pious wonder at +the curious relations between the shells and their fowl-offspring. +Gerard thus attributes the origin of the latter to the barnacles. He +says nothing of the "wormeetin" holes and burrows so frequently +mentioned by Boece, nor would he have agreed with the latter in +crediting the "nature of the occeane see" with their production, save +in so far as their barnacle-parents lived and existed in the waters of +the ocean. + +The last account of this curious fable which we may allude to in the +present instance is that of Sir Robert Moray, who, in his work +entitled "A Relation concerning Barnacles," published in the +_Philosophical Transactions_ of the Royal Society in 1677-78, gives a +succinct account of these crustaceans and their bird-progeny. Sir +Robert is described as "lately one of his Majesties Council for the +Kingdom of Scotland," and we may therefore justly assume his account +to represent that of a cultured, observant person of his day and +generation. The account begins by remarking that the "most ordinary +trees" found in the western islands of Scotland "are Firr and Ash." +"Being," continues Sir Robert, "in the Island of East (Uist), I saw +lying upon the shore a cut of a large Firr tree of about 2-1/2 foot +diameter, and 9 or 10 foot long; which had lain so long out of the +water that it was very dry: And most of the shells that had formerly +cover'd it, were worn or rubb'd off. Only on the parts that lay next +the ground, there still hung multitudes of little Shells; having +within them little Birds, perfectly shap'd, supposed to be Barnacles." +Here again the description applies to the barnacles; the "little +birds" they are described as containing being of course the bodies of +the shell-fish. + +"The Shells," continues the narrator, "hang at the Tree by a Neck +longer than the Shell;" this "neck" being represented by the stalk of +the barnacle. The neck is described as being composed "of a kind of +filmy substance, round, and hollow, and creased, not unlike the +Wind-pipe of a Chicken; spreading out broadest where it is fastened to +the Tree, from which it seems to draw and convey the matter which +serves for the growth and vegetation of the Shell and the little Bird +within it." Sir Robert Moray therefore agrees in respect of the manner +of nourishment of the barnacles with the opinion of Giraldus already +quoted. The author goes on to describe the "Bird" found in every +shell he opened; remarking that "there appeared nothing wanting as to +the internal parts, for making up a perfect Sea-fowl: every little +part appearing so distinctly, that the whole looked like a large Bird +seen through a concave or diminishing Glass, colour and feature being +everywhere so clear and neat." The "Bird" is most minutely described +as to its bill, eyes, head, neck, breast, wings, tail, and feet, the +feathers being "everywhere perfectly shaped, and blackish-coloured. +All being dead and dry," says Sir Robert, "I did not look after the +Internal parts of them," a statement decidedly inconsistent with his +previous assertion as to the perfect condition of the "internal +parts"; and he takes care to add, "nor did I ever see any of the +little Birds alive, nor met with anybody that did. Only some credible +persons," he concludes, "have assured me they have seen some as big as +their fist." + +[Illustration: FIG. 2. BARNACLE TREE. (From Munster's "Cosmography.")] + +This last writer thus avers that he saw little birds within the shells +he clearly enough describes as those of the barnacles. We must either +credit Sir Robert with describing what he never saw, or with +misconstruing what he did see. His description of the goose +corresponds with that of the barnacle goose, the reputed progeny of +the shells; and it would, therefore, seem that this author, with the +myth at hand, saw the barnacles only with the eyes of a credulous +observer, and thus beheld, in the inside of each shell--if, indeed, +his research actually extended thus far--the reproduction in miniature +of a goose, with which, as a mature bird, he was well acquainted. + +On p. 157 is a woodcut, copied from Munster's "Cosmography" (1550), a +very popular book in its time, showing the tree with its fruit, and +the geese which are supposed to have just escaped from it. + +This historical ramble may fitly preface what we have to say regarding +the probable origin of the myth. By what means could the barnacles +become credited with the power of producing the well-known geese? Once +started, the progress and growth of the myth are easily accounted for. +The mere transmission of a fable from one generation or century to +another is a simply explained circumstance, and one exemplified by the +practices of our own times. The process of accretion and addition is +also well illustrated in the perpetuation of fables; since the tale is +certain to lose nothing in its historical journey, but, on the +contrary, to receive additional elaboration with increasing age. +Professor Max Müller, after discussing various theories of the origin +of the barnacle myth, declares in favor of the idea that confusion of +language and alteration of names lie at the root of the error. The +learned author of the "Science of Language" argues that the true +barnacles were named, properly enough, Bernaculae, and lays stress on +the fact that Bernicle geese were first caught in Ireland. That +country becomes _Hibernia_ in Latin, and the Irish geese were +accordingly named Hibernicae, or Hiberniculae. By the omission of the +first syllable--no uncommon operation for words to undergo--we obtain +the name Berniculae for the geese, this term being almost synonymous +with the name Bernaculae already applied, as we have seen, to the +barnacles. Bernicle geese and bernicle shells, confused in name, thus +became confused in nature; and, once started, the ordinary process of +growth was sufficient to further intensify, and render more realistic, +the story of the bernicle tree and its wonderful progeny. + +By way of a companion legend to that of the barnacle tree, we may +select the story of the "Lamb Tree" of Cathay, told by Sir John +Mandeville, whose notes of travel regarding crocodiles' tears, and +other points in the conformation of these reptiles, have already been +referred to. Sir John, in that chapter of his work which treats "Of +the Contries and Yles that ben bezonde the Lond of Cathay; and of the +Frutes there," etc., relates that in Cathay "there growethe a manner +of Fruyt, as thoughe it were Gowrdes: and whan thei ben rype, men +kutten (cut) hem a to (them in two), and men fyndem with inne a +lytylle Best (beast), in Flessche in Bon and Blode (bone and blood) as +though it were a lytylle Lomb (lamb) with outen wolle (without wool). +And men eaten both the Frut and the Best; and that," says Sir John, +"is a great marveylle. Of that frut," he continues, "I have eten; alle +thoughe it were wondirfulle"--this being added, no doubt, from an +idea that there might possibly be some stay-at-home persons who would +take Sir John's statement _cum grano salis_. "But," adds this worthy +"knyght of Ingolond," "I knowe wel that God is marveyllous in His +Werkes." Not to be behind the inhabitants of Cathay in a tale of +wonders, the knight related to these Easterns "als gret a marveylle to +hem that is amonges us; and that was of the Bernakes. For I tolde him +hat in oure Countree weren Trees that beren a Fruyt, that becomen +Briddes (birds) fleeynge: and tho that fellen in the Water lyven +(live); and thei that fallen on the Erthe dyen anon: and thei ben +right gode to mannes mete (man's meat). And here had thei als gret +marvayle," concludes Sir John, "that sume of hem trowed it were an +impossible thing to be." Probably the inhabitants of Cathay, knowing +their own weakness as regards the lamb tree, might possess a +fellow-feeling for their visitor's credulity, knowing well, from +experience, the readiness with which a "gret marvayle" could be +evolved and sustained. + +Passing from the sphere of the mythical and marvellous as represented +in mediaeval times, we may shortly discuss a question, which, of all +others, may justly claim a place in the records of zoölogical +curiosities--namely, the famous and oft-repeated story of the "Toad +from the solid rock," as the country newspapers style the incident. +Regularly, year by year, and in company with the reports of the +sea-serpent's reappearance, we may read of the discoveries of toads +and frogs in situations and under circumstances suggestive of a +singular vitality on the part of the amphibians, of more than usual +credulity on the part of the hearers, or of a large share of +inventive genius in the narrators of such tales. The question +possesses for every one a certain degree of interest, evoked by the +curious and strange features presented on the face of the tales. And +it may therefore not only prove an interesting but also a useful +study, if we endeavor to arrive at some just and logical conceptions +of these wonderful narrations. + +[Illustration] + +Instances of the discovery of toads and frogs in solid rocks need not +be specially given; suffice it to say, that these narratives are +repeated year by year with little variation. A large block of stone or +face of rock is detached from its site, and a toad or frog is seen +hereafter to be hopping about in its usual lively manner. The +conclusion to which the bystanders invariably come is that the animal +must have been contained within the rock, and that it was liberated by +the dislodgement of the mass. Now, in many instances, cases of the +appearance of toads during quarrying operations have been found, on +close examination, to present no evidence whatever that the appearance +of the animals was due to the dislodgement of the stones. A frog or +toad may be found hopping about among some recently formed débris, and +the animal is at once seized upon and reported as having emerged from +the rocks into the light of day. There is in such a case not the +slightest ground for supposing any such thing; and the animal may more +reasonably be presumed to have simply hopped into the débris from its +ordinary habitat. But laying aside narratives of this kind, which lose +their plausibility under a very commonplace scrutiny, there still +exist cases, reported in an apparently exact and truthful manner, in +which these animals have been alleged to appear from the inner +crevices of rocks after the removal of large masses of the formations. +We shall assume these latter tales to contain a plain, unvarnished +statement of what was observed, and deal with the evidence they +present on this footing. + +[Illustration: A TOAD.] + +One or two notable examples of such verified tales are related by +Smellie, in his "Philosophy of Natural History." Thus, in the "Memoirs +of the French Academy of Sciences" for 1719, a toad is described as +having been found in the heart of an elm tree; and another is stated +to have been found in the heart of an old oak tree, in 1731, near +Nantz. The condition of the trees is not expressly stated, nor are we +afforded any information regarding the appearance of the +toads--particulars of considerable importance in view of the +suggestions and explanations to be presently brought forward. Smellie +himself, while inclined to be sceptical in regard to the truth or +exactness of many of the tales told of the vitality of toads, regards +the matter as affording food for reflection, since he remarks, "But I +mean not to persuade, for I cannot satisfy myself; all I intend is, to +recommend to those gentlemen who may hereafter chance to see such rare +phenomena, a strict examination of every circumstance that can throw +light upon a subject so dark and mysterious; for the vulgar, ever +inclined to render uncommon appearances still more marvellous, are not +to be trusted." + +This author strikes the key-note of the inquiry in his concluding +words, and we shall find that the explanation of the matter really +lies in the clear understanding of what are the probabilities, and +what the actual details, of the cases presented for consideration. We +may firstly, then, glance at a few of the peculiarities of the frogs +and toads, regarded from a zoölogical point of view. As every one +knows, these animals emerge from the egg in the form of little +fish-like "tadpoles," provided with outside gills, which are soon +replaced by inside gills, resembling those of fishes. The hind legs +are next developed, and the fore limbs follow a little later; whilst, +with the development of lungs, and the disappearance of the gills and +tail, the animal leaves the water, and remains for the rest of its +life an air-breathing, terrestrial animal. Then, secondly, in the +adult frog or toad, the naturalist would point to the importance of +the skin as not only supplementing, but, in some cases, actually +supplanting the work of the lungs as the breathing organ. Frogs and +toads will live for months under water, and will survive the excision +of the lungs for like periods; the skin in such cases serving as the +breathing surface. A third point worthy of remembrance is included in +the facts just related, and is implied in the information that these +animals can exist for long periods without food, and with but a +limited supply of air. We can understand this toleration on the part +of these animals when we take into consideration their cold-blooded +habits, which do not necessitate, and which are not accompanied by, +the amount of vital activity we are accustomed to note in higher +animals. And, as a last feature in the purely scientific history of +the frogs and toads, it may be remarked that these animals are known +to live for long periods. One pet toad is mentioned by a Mr. Arscott +as having attained, to his knowledge, the age of thirty-six years; and +a greater age still might have been recorded of this specimen, but for +the untoward treatment it sustained at the hands, or rather beak, of a +tame raven. In all probability it may be safely assumed that, when the +conditions of life are favorable, these creatures may attain a highly +venerable age--regarding the lapse of time from a purely human and +interested point of view. + +We may now inquire whether or not the foregoing considerations may +serve to throw any light upon the tales of the quarryman. The first +point to which attention may be directed is that involved in the +statement that the amphibian has been imprisoned in a _solid_ rock. +Much stress is usually laid on the fact that the rock was solid; this +fact being held to imply the great age, not to say antiquity, of the +rock and its supposed tenant. The impartial observer, after an +examination of the evidence presented, will be inclined to doubt +greatly the justification for inserting the adjective "solid"; for +usually no evidence whatever is forthcoming as to the state of the +rock prior to its removal. No previous examination of the rock is or +can be made, from the circumstance that no interest can possibly +attach to its condition until its removal reveals the apparent wonder +it contained, in the shape of the live toad. And it is equally +important to note that we rarely, if ever, find mention of any +examination of the rock being made subsequently to the discovery. +Hence, a first and grave objection may be taken to the validity of the +supposition that the rock was solid, and it may be fairly urged that +on this supposition the whole question turns and depends. For if the +rock cannot be proved to have been impermeable to and barred against +the entrance of living creatures, the objector may proceed to show the +possibility of the toad having gained admission, under certain notable +circumstances, to its prison-house. + +The frog or toad in its young state, and having just entered upon its +terrestrial life, is a small creature, which could, with the utmost +ease, wriggle into crevices and crannies of a size which would almost +preclude such apertures being noticed at all. Gaining access to a +roomier crevice or nook within, and finding there a due supply of air, +along with a dietary consisting chiefly of insects, the animal would +grow with tolerable rapidity, and would increase to such an extent +that egress through its aperture of entrance would become an +impossibility. Next, let us suppose that the toleration of the toad's +system to starvation and to a limited supply of air is taken into +account, together with the fact that these creatures will hibernate +during each winter, and thus economize, as it were, their vital +activity and strength; and after the animal has thus existed for a +year or two--no doubt under singularly hard conditions--let us imagine +that the rock is split up by the wedge and lever of the excavator. We +can then readily enough account for the apparently inexplicable story +of "the toad in the rock." "There is the toad and here is the solid +rock," say the gossips. "There is an animal which has singular powers +of sustaining life under untoward conditions, and which, in its young +state, could have gained admittance to the rock through a mere +crevice," says the naturalist in reply. Doubtless, the great army of +the unconvinced may still believe in the tale as told them; for the +weighing of evidence and the placing _pros_ and _cons_ in fair +contrast are not tasks of congenial or wonted kind in the ordinary run +of life. Some people there will be who will believe in the original +solid rock and its toad, despite the assertion of the geologists that +the earliest fossils of toads appear in almost the last-formed rocks, +and that a live toad in rocks of very ancient age--presuming, +according to the popular belief, that the animal was enclosed when the +rock was formed--would be as great an anomaly and wonder as the +mention, as an historical fact, of an express train or the telegraph +in the days of the patriarchs. In other words, the live toad which +hops out of an Old Red Sandstone rock must be presumed, on the popular +belief, to be older by untold ages than the oldest fossil frogs and +toads. The reasonable mind, however, will ponder and consider each +feature of the case, and will rather prefer to countenance a +supposition based on ordinary experience, than an explanation brought +ready-made from the domain of the miraculous; whilst not the least +noteworthy feature of these cases is that included in the remark of +Smellie, respecting the tendency of uneducated and superstitious +persons to magnify what is uncommon, and in his sage conclusion that +as a rule such persons in the matter of their relations "are not to be +trusted." + +But it must also be noted that we possess valuable evidence of a +positive and direct kind bearing on the duration of life in toads +under adverse circumstances. As this evidence tells most powerfully +against the supposition that the existence of those creatures can be +indefinitely prolonged, it forms of itself a veritable court of appeal +in the cases under discussion. The late Dr. Buckland, curious to learn +the exact extent of the vitality of the toad, caused, in the year +1825, two large blocks of stone to be prepared. One of the blocks was +taken from the oölite limestone, and in this first stone twelve cells +were excavated. Each cell was one foot deep and five inches in +diameter. The mouth of each cell was grooved so as to admit of two +covers being placed over the aperture; the first or lower cover being +of glass, and the upper one of slate. Both covers were so adapted that +they could be firmly luted down with clay or putty; the object of this +double protection being that the slate cover could be raised so as to +inspect the contained object through the closed glass cover without +admitting air. In the second or sandstone block, a series of twelve +cells was also excavated; these latter cells being, however, of +smaller size than those of the limestone block, each cell being only +six inches in depth by five inches in diameter. These cells were +likewise fitted with double covers. + +On November 26th, 1825, a live toad--kept for some time previously to +insure its being healthy--was placed in each of the twenty-four cells. +The largest specimen weighed 1185 grains, and the smallest 115 grains. +The stones and the immured toads were buried on the day mentioned, +three feet deep, in Dr. Buckland's garden. There they lay until +December 10th, 1826, when they were disinterred and their tenants +examined. All the toads in the smaller cells of the sandstone block +were dead, and from the progress of decomposition it was inferred that +they had succumbed long before the date of disinterment. The majority +of the toads in the limestone block were alive, and, curiously enough, +one or two had actually increased in weight. Thus, No. 5, which at the +commencement of its captivity had weighed 1185 grains, had increased +to 1265 grains; but the glass cover of No. 5's cell was found to be +cracked. Insects and air must therefore have obtained admittance and +have afforded nourishment to the imprisoned toad; this supposition +being rendered the more likely by the discovery that in one of the +cells, the covers of which were also cracked and the tenant of which +was dead, numerous insects were found. No. 9, weighing originally 988 +grains, had increased during its incarceration to 1116 grains; but +No. 1, which in the year 1825 had weighed 924 grains, was found in +December, 1826, to have decreased to 698 grains; and No. 11, +originally weighing 936 grains, had likewise disagreed with the +imprisonment, weighing only 652 grains when examined in 1826. + +At the period when the blocks of stone were thus prepared, four toads +were pinned up in holes five inches deep and three inches in diameter, +cut in the stem of an apple-tree; the holes being firmly plugged with +tightly fitting wooden plugs. These four toads were found to be dead +when examined along with the others in 1826; and of four others +enclosed in basins made of plaster of Paris, and which were also +buried in Dr. Buckland's garden, two were found to be dead at the end +of a year, their comrades being alive, but looking starved and meagre. +The toads which were found alive in the limestone block in December, +1826, were again immured and buried, but were found to be dead, +without leaving a single survivor, at the end of the second year of +their imprisonment. + +These experiments may fairly be said to prove two points. They firstly +show that under circumstances even of a favorable kind when compared +with the condition popularly believed in--namely, that of being +enclosed in a _solid_ rock--the limit of the toad's life may be +assumed to be within two years; this period being no doubt capable of +being extended when the animal gains a slight advantage, exemplified +by the admission of air and insect-food. Secondly, we may reasonably +argue that these experiments show that toads when rigorously treated, +like other animals, become starved and meagre, and by no means +resemble the lively, well-fed animals reported as having emerged from +an imprisonment extending, in popular estimation, through periods of +inconceivable duration. + +These tales are, in short, as devoid of actual foundation as are the +modern beliefs in the venomous properties of the toad, or the ancient +beliefs in the occult and mystic powers of various parts of its frame +when used in incantations. Shakespeare, whilst attributing to the toad +venomous qualities, has yet immortalized it in his famous simile by +crediting it with the possession of a "precious jewel." But even in +the latter case the animal gets but scant justice; for science strips +it of its poetical reputation, and in this, as in other respects, +shows it, despite fable and myth, to be zoölogically an interesting, +but otherwise a commonplace member of the animal series. + +[Illustration] + + + + +ON A PIECE OF CHALK + +_A LECTURE TO WORKING MEN_. + +(Delivered in England.) + +BY T.H. HUXLEY. + + +[Illustration: A CHALK CLIFF.] + +If a well were to be sunk at our feet in the midst of the city of +Norwich, the diggers would very soon find themselves at work in that +white substance almost too soft to be called rock, with which we are +all familiar as "chalk." + +Not only here, but over the whole county of Norfolk, the well-sinker +might carry his shaft down many hundred feet without coming to the end +of the chalk; and, on the sea-coast, where the waves have pared away +the face of the land which breasts them, the scarped faces of the high +cliffs are often wholly formed of the same material. Northward, the +chalk may be followed as far as Yorkshire; on the south coast it +appears abruptly in the picturesque western bays of Dorset, and breaks +into the Needles of the Isle of Wight; while on the shores of Kent it +supplies that long line of white cliffs to which England owes her name +of Albion. + +Were the thin soil which covers it all washed away, a curved band of +white chalk, here broader, and there narrower, might be followed +diagonally across England from Lulworth in Dorset, to Flamborough Head +in Yorkshire--a distance of over two hundred and eighty miles as the +crow flies. + +From this band to the North Sea, on the east, and the Channel, on the +south, the chalk is largely hidden by other deposits; but, except in +the Weald of Kent and Sussex, it enters into the very foundation of +all the south-eastern counties. + +Attaining, as it does in some places, a thickness of more than a +thousand feet, the English chalk must be admitted to be a mass of +considerable magnitude. Nevertheless, it covers but an insignificant +portion of the whole area occupied by the chalk formation of the +globe, which has precisely the same general character as ours, and is +found in detached patches, some less, and others more extensive, than +the English. + +Chalk occurs in north-west Ireland; it stretches over a large part of +France--the chalk which underlies Paris being, in fact, a continuation +of that of the London basin; it runs through Denmark and Central +Europe, and extends southward to North Africa; while eastward, it +appears in the Crimea and in Syria, and may be traced as far as the +shores of the Sea of Aral, in Central Asia. + +If all the points at which true chalk occurs were circumscribed, they +would lie within an irregular oval about three thousand miles in long +diameter--the area of which would be as great as that of Europe, and +would many times exceed that of the largest existing inland sea--the +Mediterranean. + +Thus the chalk is no unimportant element in the masonry of the earth's +crust, and it impresses a peculiar stamp, varying with the conditions +to which it is exposed, on the scenery of the districts in which it +occurs. The undulating downs and rounded coombs, covered with +sweet-grassed turf, of our inland chalk country, have a peacefully +domestic and mutton-suggesting prettiness, but can hardly be called +either grand or beautiful. But on our southern coasts, the wall-sided +cliffs, many hundred feet high, with vast needles and pinnacles +standing out in the sea, sharp and solitary enough to serve as perches +for the wary cormorant, confer a wonderful beauty and grandeur upon +the chalk headlands. And in the East, chalk has its share in the +formation of some of the most venerable of mountain ranges, such as +the Lebanon. + + * * * * * + +What is this wide-spread component of the surface of the earth? and +whence did it come? + +You may think this no very hopeful inquiry. You may not unnaturally +suppose that the attempt to solve such problems as these can lead to +no result, save that of entangling the inquirer in vague speculations, +incapable of refutation and of verification. + +If such were really the case, I should have selected some other +subject than a "piece of chalk" for my discourse. But, in truth, +after much deliberation, I have been unable to think of any topic +which would so well enable me to lead you to see how solid is the +foundation upon which some of the most startling conclusions of +physical science rest. + +A great chapter of the history of the world is written in the chalk. +Few passages in the history of man can be supported by such an +overwhelming mass of direct and indirect evidence as that which +testifies to the truth of the fragment of the history of the globe, +which I hope to enable you to read, with your own eyes, to-night. + +[Illustration: MICROSCOPIC SECTION OF CHALK. + +(Magnified nearly 300 times.) + +1. Textularia. 2. Globigerina. 3. Rotalia. 4. Coccoliths.] + +Let me add, that few chapters of human history have a more profound +significance for ourselves. I weigh my words well when I assert, that +the man who should know the true history of the bit of chalk which +every carpenter carries about in his breeches' pocket, though ignorant +of all other history, is likely, if he will think his knowledge out to +its ultimate results, to have a truer, and therefore a better, +conception of this wonderful universe, and of man's relation to it, +than the most learned student who is deep-read in the records of +humanity and ignorant of those of nature. + +The language of the chalk is not hard to learn, not nearly so hard as +Latin, if you only want to get at the broad features of the story it +has to tell; and I propose that we now set to work to spell that story +out together. + +We all know that if we "burn" chalk, the result is quicklime. Chalk, +in fact, is a compound of carbonic acid gas and lime; and when you +make it very hot, the carbonic acid flies away and the lime is left. + +By this method of procedure we see the lime, but we do not see the +carbonic acid. If, on the other hand, you were to powder a little +chalk and drop it into a good deal of strong vinegar, there would be a +great bubbling and fizzing, and, finally, a clear liquid, in which no +sign of chalk would appear. Here you see the carbonic acid in the +bubbles; the lime, dissolved in the vinegar, vanishes from sight. +There are a great many other ways of showing that chalk is essentially +nothing but carbonic acid and quicklime. Chemists enunciate the result +of all the experiments which prove this, by stating that chalk is +almost wholly composed of "carbonate of lime." + +It is desirable for us to start from the knowledge of this fact, +though it may not seem to help us very far toward what we seek. For +carbonate of lime is a widely-spread substance, and is met with under +very various conditions. All sorts of limestones are composed of more +or less pure carbonate of lime. The crust which is often deposited by +waters which have drained through limestone rocks, in the form of what +are called stalagmites and stalactites, is carbonate of lime. Or, to +take a more familiar example, the fur on the inside of a tea-kettle is +carbonate of lime; and, for anything chemistry tells us to the +contrary, the chalk might be a kind of gigantic fur upon the bottom of +the earth-kettle, which is kept pretty hot below. + +Let us try another method of making the chalk tell us its own history. +To the unassisted eye chalk looks simply like a very loose and open +kind of stone. But it is possible to grind a slice of chalk down so +thin that you can see through it--until it is thin enough, in fact, to +be examined with any magnifying power that may be thought desirable. A +thin slice of the fur of a kettle might be made in the same way. If it +were examined microscopically, it would show itself to be a more or +less distinctly laminated mineral substance, and nothing more. + +But the slice of chalk presents a totally different appearance when +placed under the microscope. The general mass of it is made up of very +minute granules; but, imbedded in this matrix, are innumerable bodies, +some smaller and some larger, but, on a rough average, not more than a +hundredth of an inch in diameter, having a well-defined shape and +structure. A cubic inch of some specimens of chalk may contain +hundreds of thousands of these bodies, compacted together with +incalculable millions of the granules. + +[Illustration: CHALK. + +(Magnified nearly 100 diameters.)] + +The examination of a transparent slice gives a good notion of the +manner in which the components of the chalk are arranged, and of +their relative proportions. But, by rubbing up some chalk with a brush +in water and then pouring off the milky fluid, so as to obtain +sediments of different degrees of fineness, the granules and the +minute rounded bodies may be pretty well separated from one another, +and submitted to microscopic examination, either as opaque or as +transparent objects. By combining the views obtained in these various +methods, each of the rounded bodies may be proved to be a +beautifully-constructed calcareous fabric, made up of a number of +chambers, communicating freely with one another. The chambered bodies +are of various forms. One of the commonest is something like a +badly-grown raspberry, being formed of a number of nearly globular +chambers of different sizes congregated together. It is called +Globigerina, and some specimens of chalk consist of little else than +Globigerinæ and granules. + +[Illustration: GLOBIGERINA.] + +Let us fix our attention upon the Globigerina. It is the spoor of the +game we are tracking. If we can learn what it is and what are the +conditions of its existence, we shall see our way to the origin and +past history of the chalk. + +A suggestion which may naturally enough present itself is, that these +curious bodies are the result of some process of aggregation which has +taken place in the carbonate of lime; that, just as in winter, the +rime on our windows simulates the most delicate and elegantly +arborescent foliage--proving that the mere mineral matter may, under +certain conditions, assume the outward form of organic bodies--so this +mineral substance, carbonate of lime, hidden away in the bowels of +the earth, has taken the shape of these chambered bodies. I am not +raising a merely fanciful and unreal objection. Very learned men, in +former days, have even entertained the notion that all the formed +things found in rocks are of this nature; and if no such conception is +at present held to be admissible, it is because long and varied +experience has now shown that mineral matter never does assume the +form and structure we find in fossils. If anyone were to try to +persuade you that an oyster-shell (which is also chiefly composed of +carbonate of lime) had crystallized out of sea-water, I suppose you +would laugh at the absurdity. Your laughter would be justified by the +fact that all experience tends to show that oyster-shells are formed +by the agency of oysters, and in no other way. And if there were no +better reasons, we should be justified, on like grounds, in believing +that Globigerina is not the product of anything but vital activity. + +Happily, however, better evidence in proof of the organic nature of +the Globigerinæ than that of analogy is forthcoming. It so happens +that calcareous skeletons, exactly similar to the Globigerinæ of the +chalk, are being formed, at the present moment, by minute living +creatures, which flourish in multitudes, literally more numerous than +the sands of the sea-shore, over a large extent of that part of the +earth's surface which is covered by the ocean. + +The history of the discovery of these living Globigerinæ, and of the +part which they play in rock-building, is singular enough. It is a +discovery which, like others of no less scientific importance, has +arisen, incidentally, out of work devoted to very different and +exceedingly practical interests. + +When men first took to the sea, they speedily learned to look out for +shoals and rocks; and the more the burthen of their ships increased, +the more imperatively necessary it became for sailors to ascertain +with precision the depth of the waters they traversed. Out of this +necessity grew the use of the lead and sounding-line; and, ultimately, +marine-surveying, which is the recording of the form of coasts and of +the depth of the sea, as ascertained by the sounding-lead, upon +charts. + +At the same time, it became desirable to ascertain and to indicate the +nature of the sea-bottom, since this circumstance greatly affects its +goodness as holding ground for anchors. Some ingenious tar, whose name +deserves a better fate than the oblivion into which it has fallen, +attained this object by "arming" the bottom of the lead with a lump of +grease, to which more or less of the sand or mud, or broken shells, as +the case might be, adhered, and was brought to the surface. But, +however well adapted such an apparatus might be for rough nautical +purposes, scientific accuracy could not be expected from the armed +lead, and to remedy its defects (especially when applied to sounding +in great depths) Lieutenant Brooke, of the American Navy, some years +ago invented a most ingenious machine, by which a considerable portion +of the superficial layer of the sea-bottom can be scooped out and +brought up, from any depth to which the lead descends. + +In 1853, Lieutenant Brooke obtained mud from the bottom of the North +Atlantic, between Newfoundland and the Azores, at a depth of more than +ten thousand feet, or two miles, by the help of this sounding +apparatus. The specimens were sent for examination to Ehrenberg of +Berlin, and to Bailey of West Point, and those able microscopists +found that this deep-sea mud was almost entirely composed of the +skeletons of living organisms--the greater proportion of these being +just like the Globigerinæ already known to occur in chalk. + +Thus far, the work had been carried on simply in the interests of +science, but Lieutenant Brooke's method of sounding acquired a high +commercial value, when the enterprise of laying down the +telegraph-cable between this country and the United States was +undertaken. For it became a matter of immense importance to know, not +only the depth of the sea over the whole line, along which the cable +was to be laid, but the exact nature of the bottom, so as to guard +against chances of cutting or fraying the strands of that costly rope. +The Admiralty consequently ordered Captain Dayman, an old friend and +shipmate of mine, to ascertain the depth over the whole line of the +cable, and to bring back specimens of the bottom. In former days, such +a command as this might have sounded very much like one of the +impossible things which the young prince in the Fairy Tales is ordered +to do before he can obtain the hand of the princess. However, in the +months of June and July, 1857, my friend performed the task assigned +to him with great expedition and precision, without, so far as I know, +having met with any reward of that kind. The specimens of Atlantic mud +which he procured were sent to me to be examined and reported upon. + +The result of all these operations is, that we know the contours and +the nature of the surface-soil covered by the North Atlantic, for a +distance of seventeen hundred miles from east to west, as well as we +know that of any part of the dry land. + +It is a prodigious plain--one of the widest and most even plains in +the world. If the sea were drained off, you might drive a wagon all +the way from Valentia, on the west coast of Ireland, to Trinity Bay in +Newfoundland. And, except upon one sharp incline about two hundred +miles from Valentia, I am not quite sure that it would even be +necessary to put the skid on, so gentle are the ascents and descents +upon that long route. From Valentia the road would lie down-hill for +about two hundred miles to the point at which the bottom is now +covered by seventeen hundred fathoms of sea-water. Then would come the +central plain, more than a thousand miles wide, the inequalities of +the surface of which would be hardly perceptible, though the depth of +water upon it now varies from ten thousand to fifteen thousand feet; +and there are places in which Mont Blanc might be sunk without showing +its peak above water. Beyond this, the ascent on the American side +commences, and gradually leads, for about three hundred miles, to the +Newfoundland shore. + +Almost the whole of the bottom of this central plain (which extends +for many hundred miles in a north and south direction) is covered by a +fine mud, which, when brought to the surface, dries into a grayish +white friable substance. You can write with this on a black-board, if +you are so inclined; and, to the eye, it is quite like very soft, +grayish chalk. Examined chemically, it proves to be composed almost +wholly of carbonate of lime; and if you make a section of it, in the +same way as that of the piece of chalk was made, and view it with the +microscope, it presents innumerable Globigerinæ embedded in a granular +matrix. + +Thus this deep-sea mud is substantially chalk. I say substantially, +because there are a good many minor differences; but as these have no +bearing on the question immediately before us--which is the nature of +the Globigerinæ of the chalk--it is unnecessary to speak of them. + +Globigerinæ of every size, from the smallest to the largest, are +associated together in the Atlantic mud, and the chambers of many are +filled by a soft animal matter. This soft substance is, in fact, the +remains of the creature to which the Globigerina shell, or rather +skeleton, owes its existence--and which is an animal of the simplest +imaginable description. It is, in fact, a mere particle of living +jelly, without defined parts of any kind--without a mouth, nerves, +muscles, or distinct organs, and only manifesting its vitality to +ordinary observation by thrusting out and retracting from all parts of +its surface long filamentous processes, which serve for arms and legs. +Yet this amorphous particle, devoid of everything which, in the higher +animals, we call organs, is capable of feeding, growing, and +multiplying; of separating from the ocean the small proportion of +carbonate of lime which is dissolved in sea-water; and of building up +that substance into a skeleton for itself, according to a pattern +which can be imitated by no other known agency. + +The notion that animals can live and flourish in the sea, at the vast +depths from which apparently living Giobigerinæ have been brought up, +does not agree very well with our usual conceptions respecting the +conditions of animal life; and it is not so absolutely impossible as +it might at first sight appear to be, that the Globigerinæ of the +Atlantic sea-bottom do not live and die where they are found. + +[Illustration: DIATOM OOZE DREDGED FROM A DEPTH OF 1950 FEET. + +(Magnified nearly 300 diameters.)] + +As I have mentioned, the soundings from the great Atlantic plain are +almost entirely made up of Globigerinæ, with the granules which have +been mentioned, and some few other calcareous shells; but a small +percentage of the chalky mud--perhaps at most some five per cent of +it--is of a different nature, and consists of shells and skeletons +composed of silex, or pure flint. These siliceous bodies belong partly +to the lowly vegetable organisms which are called Diatomaceæ, and +partly to the minute and extremely simple animals, termed Radiolaria. +It is quite certain that these creatures do not live at the bottom of +the ocean, but at its surface--where they may be obtained in +prodigious numbers by the use of a properly constructed net. Hence it +follows that these siliceous organisms, though they are not heavier +than the lightest dust, must have fallen, in some cases, through +fifteen thousand feet of water, before they reached their final +resting-place on the ocean floor. And, considering how large a +surface these bodies expose in proportion to their weight, it is +probable that they occupy a great length of time in making their +burial journey from the surface of the Atlantic to the bottom. + +[Illustration: RADIOLARIA. (_a._ Natural size. _b._ One-third natural +size.)] + +But if the Radiolaria and Diatoms are thus rained upon the bottom of +the sea, from the superficial layer of its waters in which they pass +their lives, it is obviously possible that the Globigerinæ may be +similarly derived; and if they were so, it would be much more easy to +understand how they obtain their supply of food than it is at present. +Nevertheless, the positive and negative evidence all points the other +way. The skeletons of the full-grown, deep-sea Globigerinæ are so +remarkably solid and heavy in proportion to their surface as to seem +little fitted for floating; and, as a matter of fact, they are not to +be found along with the Diatoms and Radiolaria, in the uppermost +stratum of the open ocean. + +It has been observed, again, that the abundance of Globigerinæ, in +proportion to other organisms of like kind, increases with the depth +of the sea; and that deep-water Globigerinæ are larger than those +which live in the shallower parts of the sea; and such facts negative +the supposition that these organisms have been swept by currents from +the shallows into the deeps of the Atlantic. + +It therefore seems to be hardly doubtful that these wonderful +creatures live and die at the depths in which they are found.[1] + +[Footnote 1: During the cruise of H.M.S. Bull-dog, commanded by Sir +Leopold M'Clintock, in 1860, living star-fish were brought up, +clinging to the lowest part of the sounding-line, from a depth of 1260 +fathoms, midway between Cape Farewell, in Greenland, and the Rockall +banks. Dr. Wallich ascertained that the sea-bottom at this point +consisted of the ordinary Globigerina ooze, and that the stomachs of +the star-fishes were full of Globigerinæ. This discovery removes all +objections to the existence of living Globigerinæ at great depths, +which are based upon the supposed difficulty of maintaining animal +life under such conditions; and it throws the burden of proof upon +those who object to the supposition that the Globigerinæ live and die +where they are found.] + +However, the important points for us are, that the living Globigerinæ +are exclusively marine animals, the skeletons of which abound at the +bottom of deep seas; and that there is not a shadow of reason for +believing that the habits of the Globigerinæ of the chalk differed +from those of the existing species. But if this be true, there is no +escaping the conclusion that the chalk itself is the dried mud of an +ancient deep sea. + +In working over the soundings collected by Captain Dayman, I was +surprised to find that many of what I have called the "granules" of +that mud were not, as one might have been tempted to think at first, +the mere powder and waste of Globigerinæ, but that they had a definite +form and size. I termed these bodies "_coccoliths_" and doubted their +organic nature. Dr. Wallich verified my observation, and added the +interesting discovery that, not unfrequently, bodies similar to these +"coccoliths" were aggregated together into spheroids, which he termed +"_coccospheres_." So far as we knew, these bodies, the nature of which +is extremely puzzling and problematical, were peculiar to the +Atlantic soundings. + +But, a few years ago, Mr. Sorby, in making a careful examination of +the chalk by means of thin sections and otherwise, observed, as +Ehrenberg had done before him, that much of its granular basis +possesses a definite form. Comparing these formed particles with those +in the Atlantic soundings, he found the two to be identical; and thus +proved that the chalk, like the soundings, contains these mysterious +coccoliths and coccospheres. Here was a further and a most interesting +confirmation, from internal evidence, of the essential identity of the +chalk with modern deep-sea mud. Globigerinæ, coccoliths, and +coccospheres are found as the chief constituents of both, and testify +to the general similarity of the conditions under which both have been +formed.[2] + +[Footnote 2: I have recently traced out the development of the +"coccoliths" from a diameter of 1/7000th of an inch up to their +largest size (which is about 1/1600th), and no longer doubt that they +are produced by independent organisms, which, like the Globigerinæ, +live and die at the bottom of the sea.] + +The evidence furnished by the hewing, facing, and superposition of the +stones of the Pyramids, that these structures were built by men, has +no greater weight than the evidence that the chalk was built by +Globigerinæ; and the belief that those ancient pyramid-builders were +terrestrial and air-breathing creatures like ourselves, is not better +based than the conviction that the chalk-makers lived in the sea. + +But as our belief in the building of the Pyramids by men is not only +grounded on the internal evidence afforded by these structures, but +gathers strength from multitudinous collateral proofs, and is clinched +by the total absence of any reason for a contrary belief; so the +evidence drawn from the Globigerinæ that the chalk is an ancient +sea-bottom, is fortified by innumerable independent lines of evidence; +and our belief in the truth of the conclusion to which all positive +testimony tends, receives the like negative justification from the +fact that no other hypothesis has a shadow of foundation. + +It may be worth while briefly to consider a few of these collateral +proofs that the chalk was deposited at the bottom of the sea. + +The great mass of the chalk is composed, as we have seen, of the +skeletons of Globigerinæ, and other simple organisms, imbedded in +granular matter. Here and there, however, this hardened mud of the +ancient sea reveals the remains of higher animals which have lived and +died, and left their hard parts in the mud, just as the oysters die +and leave their shells behind them, in the mud of the present seas. + +[Illustration: UPPER SILURIAN CORALS AND CRUSTACEANS.] + +There are, at the present day, certain groups of animals which are +never found in fresh waters, being unable to live anywhere but in the +sea. Such are the corals; those corallines which are called Polyzoa; +those creatures which fabricate the lamp-shells, and are called +Brachiopoda; the pearly Nautilus, and all animals allied to it; and +all the forms of sea-urchins and star-fishes. + +Not only are all these creatures confined to salt water at the present +day, but, so far as our records of the past go, the conditions of +their existence have been the same: hence, their occurrence in any +deposit is as strong evidence as can be obtained, that that deposit +was formed in the sea. Now the remains of animals of all the kinds +which have been enumerated occur in the chalk, in greater or less +abundance; while not one of those forms of shell-fish which are +characteristic of fresh water has yet been observed in it. + +When we consider that the remains of more than three thousand distinct +species of aquatic animals have been discovered among the fossils of +the chalk, that the great majority of them are of such forms as are +now met with only in the sea, and that there is no reason to believe +that any one of them inhabited fresh water--the collateral evidence +that the chalk represents an ancient sea-bottom acquires as great +force as the proof derived from the nature of the chalk itself. I +think you will now allow that I did not overstate my case when I +asserted that we have as strong grounds for believing that all the +vast area of dry land at present occupied by the chalk was once at the +bottom of the sea, as we have for any matter of history whatever; +while there is no justification for any other belief. + +[Illustration: CRETACEOUS NAUTILUS.] + +No less certain is it that the time during which the countries we now +call southeast England, France, Germany, Poland, Russia, Egypt, +Arabia, Syria, were more or less completely covered by a deep sea, +was of considerable duration. + +We have already seen that the chalk is, in places, more than a +thousand feet thick. I think you will agree with me that it must have +taken some time for the skeletons of the animalcules of a hundredth of +an inch in diameter to heap up such a mass as that. I have said that +throughout the thickness of the chalk the remains of other animals are +scattered. These remains are often in the most exquisite state of +preservation. The valves of the shell-fishes are commonly adherent; +the long spines of some of the sea-urchins, which would be detached by +the smallest jar, often remain in their places. In a word, it is +certain that these animals have lived and died when the place which +they now occupy was the surface of as much of the chalk as had then +been deposited; and that each has been covered up by the layer of +Globigerina mud, upon which the creatures imbedded a little higher up +have, in like manner, lived and died. But some of these remains prove +the existence of reptiles of vast size in the chalk sea. These lived +their time, and had their ancestors and descendants, which assuredly +implies time, reptiles being of slow growth. + +There is more curious evidence, again, that the process of covering +up, or, in other words, the deposit of Globigerina skeletons, did not +go on very fast. It is demonstrable that an animal of the cretaceous +sea might die, that its skeleton might lie uncovered upon the +sea-bottom long enough to lose all its outward coverings and +appendages by putrefaction; and that, after this had happened, another +animal might attach itself to the dead and naked skeleton, might grow +to maturity, and might itself die before the calcareous mud had buried +the whole. + +Cases of this kind are admirably described by Sir Charles Lyell. He +speaks of the frequency with which geologists find in the chalk a +fossilized sea-urchin to which is attached the lower valve of a +Crania. This is a kind of shell-fish, with a shell composed of two +pieces, of which, as in the oyster, one is fixed and the other free. + +"The upper valve is almost invariably wanting, though occasionally +found in a perfect state of preservation in the white chalk at some +distance. In this case, we see clearly that the sea-urchin first lived +from youth to age, then died and lost its spines, which were carried +away. Then the young Crania adhered to the bared shell, grew and +perished in its turn; after which, the upper valve was separated from +the lower, before the Echinus became enveloped in chalky mud." + +A specimen in the Museum of Practical Geology, in London, still +further prolongs the period which must have elapsed between the death +of the sea-urchin and its burial by the Globigeringæ. For the outward +face of the valve of a Crania, which is attached to a sea-urchin +(Micrastor), is itself overrun by an incrusting coralline, which +spreads thence over more or less of the surface of the sea-urchin. It +follows that, after the upper valve of the Crania fell off, the +surface of the attached valve must have remained exposed long enough +to allow of the growth of the whole coralline, since corallines do not +live imbedded in the mud. + +The progress of knowledge may, one day, enable us to deduce from such +facts as these the maximum rate at which the chalk can have +accumulated, and thus to arrive at the minimum duration of the chalk +period. Suppose that the valve of the Crania upon which a coralline +has fixed itself in the way just described is so attached to the +sea-urchin that no part of it is more than an inch above the face upon +which the sea-urchin rests. Then, as the coralline could not have +fixed itself if the Crania had been covered up with chalk-mud, and +could not have lived had itself been so covered, it follows, that an +inch of chalk mud could not have accumulated within the time between +the death and decay of the soft parts of the sea-urchin and the growth +of the coralline to the full size which it has attained. If the decay +of the soft parts of the sea-urchin; the attachment, growth to +maturity, and decay of the Crania; and the subsequent attachment and +growth of the coralline, took a year (which is a low estimate enough), +the accumulation of the inch of chalk must have taken more than a +year: and the deposit of a thousand feet of chalk must, consequently, +have taken more than twelve thousand years. + +The foundation of all this calculation is, of course, a knowledge of +the length of time the Crania and the coralline needed to attain their +full size; and, on this head, precise knowledge is at present wanting. +But there are circumstances which tend to show that nothing like an +inch of chalk has accumulated during the life of a Crania; and, on any +probable estimate of the length of that life, the chalk period must +have had a much longer duration than that thus roughly assigned to +it. + +Thus, not only is it certain that the chalk is the mud of an ancient +sea-bottom; but it is no less certain that the chalk sea existed +during an extremely long period, though we may not be prepared to give +a precise estimate of the length of that period in years. The relative +duration is clear, though the absolute duration may not be definable. +The attempt to affix any precise date to the period at which the chalk +sea began or ended its existence, is baffled by difficulties of the +same kind. But the relative age of the cretaceous epoch may be +determined with as great ease and certainty as the long duration of +that epoch. + +You will have heard of the interesting discoveries recently made, in +various parts of Western Europe, of flint implements, obviously worked +into shape by human hands, under circumstances which show conclusively +that man is a very ancient denizen of these regions. + +It has been proved that the old populations of Europe, whose existence +has been revealed to us in this way, consisted of savages, such as the +Esquimaux are now; that, in the country which is now France, they +hunted the reindeer, and were familiar with the ways of the mammoth +and the bison. The physical geography of France was in those days +different from what it is now--the river Somme, for instance, having +cut its bed a hundred feet deeper between that time and this; and it +is probable that the climate was more like that of Canada or Siberia +than that of Western Europe. + +The existence of these people is forgotten even in the traditions of +the oldest historical nations. The name and fame of them had utterly +vanished until a few years back; and the amount of physical change +which has been effected since their day renders it more than probable +that, venerable as are some of the historical nations, the workers of +the chipped flints of Hoxne or of Amiens are to them, as they are to +us, in point of antiquity. + +But, if we assign to these hoar relics of long-vanished generations of +men the greatest age that can possibly be claimed for them, they are +not older than the drift, or boulder clay, which, in comparison with +the chalk, is but a very juvenile deposit. You need go no further than +your own seaboard for evidence of this fact. At one of the most +charming spots on the coast of Norfolk, Cromer, you will see the +boulder clay forming a vast mass, which lies upon the chalk, and must +consequently have come into existence after it. Huge boulders of chalk +are, in fact, included in the clay, and have evidently been brought to +the position they now occupy by the same agency as that which has +planted blocks of syenite from Norway side by side with them. + +The chalk, then, is certainly older than the boulder clay. If you ask +how much, I will again take you no further than the same spot upon +your own coasts for evidence. I have spoken of the boulder clay and +drift as resting upon the chalk. That is not strictly true. Interposed +between the chalk and the drift is a comparatively insignificant +layer, containing vegetable matter. But that layer tells a wonderful +history. It is full of stumps of trees standing as they grew. +Fir-trees are there with their cones, and hazel-bushes with their +nuts; there stand the stools of oak and yew trees, beeches and +alders. Hence this stratum is appropriately called the "forest-bed." + +It is obvious that the chalk must have been upheaved and converted +into dry land before the timber trees could grow upon it. As the bolls +of some of these trees are from two to three feet in diameter, it is +no less clear that the dry land thus formed remained in the same +condition for long ages. And not only do the remains of stately oaks +and well-grown firs testify to the duration of this condition of +things, but additional evidence to the same effect is afforded by the +abundant remains of elephants, rhinoceroses, hippopotamuses, and other +great wild beasts, which it has yielded to the zealous search of such +men as the Rev. Mr. Gunn. + +When you look at such a collection as he has formed, and bethink you +that these elephantine bones did veritably carry their owners about, +and these great grinders crunch, in the dark woods of which the +forest-bed is now the only trace, it is impossible not to feel that +they are as good evidence of the lapse of time as the annual rings of +the tree-stumps. + +Thus there is a writing upon the wall of cliffs at Cromer, and whoso +runs may read it. It tells us, with an authority which cannot be +impeached, that the ancient sea-bed of the chalk sea was raised up, +and remained dry land, until it was covered with forest, stocked with +the great game whose spoils have rejoiced your geologists. How long it +remained in that condition cannot be said; but "the whirligig of time +brought its revenges" in those days as in these. That dry land, with +the bones and teeth of generations of long-lived elephants, hidden +away among the gnarled roots and dry leaves of its ancient trees, sank +gradually to the bottom of the icy sea, which covered it with huge +masses of drift and boulder clay. Sea-beasts, such as the walrus, now +restricted to the extreme north, paddled about where birds had +twittered among the topmost twigs of the fir-trees. How long this +state of things endured we know not, but at length it came to an end. +The upheaved glacial mud hardened into the soil of modern Norfolk. +Forests grew once more, the wolf and the beaver replaced the reindeer +and the elephant; and at length what we call the history of England +dawned. + +Thus you have, within the limits of your own county, proof that the +chalk can justly claim a very much greater antiquity than even the +oldest physical traces of mankind. But we may go further and +demonstrate, by evidence of the same authority as that which testifies +to the existence of the father of men, that the chalk is vastly older +than Adam himself. + +The Book of Genesis informs us that Adam, immediately upon his +creation, and before the appearance of Eve, was placed in the garden +of Eden. The problem of the geographical position of Eden has greatly +vexed the spirits of the learned in such matters, but there is one +point respecting which, so far as I know, no commentator has ever +raised a doubt. This is, that of the four rivers which are said to run +out of it, Euphrates and Hiddekel are identical with the rivers now +known by the names of Euphrates and Tigris. + +But the whole country in which these mighty rivers take their origin, +and through which they run, is composed of rocks which are either of +the same age as the chalk, or of later date. So that the chalk must +not only have been formed, but, after its formation, the time required +for the deposit of these later rocks, and for their upheaval into dry +land, must have elapsed, before the smallest brook which feeds the +swift stream of "the great river, the river of Babylon," began to +flow. + + * * * * * + +Thus, evidence which cannot be rebutted, and which need not be +strengthened, though if time permitted I might indefinitely increase +its quantity, compels you to believe that the earth, from the time of +the chalk to the present day, has been the theatre of a series of +changes as vast in their amount as they were slow in their progress. +The area on which we stand has been first sea and then land, for at +least four alternations; and has remained in each of these conditions +for a period of great length. + +Nor have these wonderful metamorphoses of sea into land, and of land +into sea, been confined to one corner of England. During the chalk +period, or "cretaceous epoch," not one of the present great physical +features of the globe was in existence. Our great mountain ranges, +Pyrenees, Alps, Himalayas, Andes, have all been upheaved since the +chalk was deposited, and the cretaceous sea flowed over the sites of +Sinai and Ararat. + +All this is certain, because rocks of cretaceous or still later date +have shared in the elevatory movements which gave rise to these +mountain chains; and may be found perched up, in some cases, many +thousand feet high upon their flanks. And evidence of equal cogency +demonstrates that, though in Norfolk the forest-bed rests directly +upon the chalk, yet it does so, not because the period at which the +forest grew immediately followed that at which the chalk was formed, +but because an immense lapse of time, represented elsewhere by +thousands of feet of rock, is not indicated at Cromer. + +I must ask you to believe that there is no less conclusive proof that +a still more prolonged succession of similar changes occurred before +the chalk was deposited. Nor have we any reason to think that the +first term in the series of these changes is known. The oldest +sea-beds preserved to us are sands, and mud, and pebbles, the wear and +tear of rocks which were formed in still older oceans. + +But, great as is the magnitude of these physical changes of the world, +they have been accompanied by a no less striking series of +modifications in its living inhabitants. + +All the great classes of animals, beasts of the field, fowls of the +air, creeping things, and things which dwell in the waters, flourished +upon the globe long ages before the chalk was deposited. Very few, +however, if any, of these ancient forms of animal life were identical +with those which now live. Certainly not one of the higher animals was +of the same species as any of those now in existence. The beasts of +the field, in the days before the chalk, were not our beasts of the +field, nor the fowls of the air such as those which the eye of man has +seen flying, unless his antiquity dates infinitely further back than +we at present surmise. If we could be carried back into those times, +we should be as one suddenly set down in Australia before it was +colonized. We should see mammals, birds, reptiles, fishes, insects, +snails, and the like, clearly recognizable as such, and yet not one of +them would be just the same as those with which we are familiar, and +many would be extremely different. + +From that time to the present, the population of the world has +undergone slow and gradual, but incessant, changes. There has been no +grand catastrophe--no destroyer has swept away the forms of life of +one period, and replaced them by a totally new creation; but one +species has vanished and another has taken its place; creatures of one +type of structure have diminished, those of another have increased, as +time has passed on. And thus, while the differences between the living +creatures of the time before the chalk and those of the present day +appear startling, if placed side by side, we are led from one to the +other by the most gradual progress, if we follow the course of Nature +through the whole series of those relics of her operations which she +has left behind. + +[Illustration: SKELETON OF THE PTERODACTYL.] + +And it is by the population of the chalk sea that the ancient and the +modern inhabitants of the world are most completely connected. The +groups which are dying out flourish, side by side, with the groups +which are now the dominant forms of life. + +Thus the chalk contains remains of those flying and swimming +reptiles, the pterodactyl, the ichthyosaurus, and the plesiosaurus, +which are found in no later deposits, but abounded in preceding ages. +The chambered shells called ammonites and belemnites, which are so +characteristic of the period preceding the cretaceous, in like manner +die with it. + +[Illustration: THE SKELETON OF THE ICHTHYOSAURUS.] + +[Illustration: THE SKELETON OF THE PLESIOSAURUS.] + +[Illustration: AMMONITES.] + +But, among these fading remainders of a previous state of things, are +some very modern forms of life, looking like Yankee peddlers among a +tribe of red Indians. Crocodiles of modern type appear; bony fishes, +many of them very similar to existing species, almost supplant the +forms of fish which predominate in more ancient seas; and many kinds +of living shell-fish first become known to us in the chalk. The +vegetation acquires a modern aspect. A few living animals are not even +distinguishable as species from those which existed at that remote +epoch. The Globigerina of the present day, for example, is not +different specifically from that of the chalk; and the same may be +said of many other Foraminifera. I think it probable that critical and +unprejudiced examination will show that more than one species of much +higher animals have had a similar longevity; but the only example +which I can at present give confidently is the snake's-head lamp-shell +(_Terebratulina caput serpentis_), which lives in our English seas and +abounded (as _Terebratulina striata_ of authors) in the chalk. + +[Illustration: BELEMNITES.] + +[Illustration: TEREBRATULINA.] + +The longest line of human ancestry must hide its diminished head +before the pedigree of this insignificant shell-fish. We Englishmen +are proud to have an ancestor who was present at the Battle of +Hastings. The ancestors of _Terebratulina caput serpentis_ may have +been present at a battle of Ichthyosauria in that part of the sea +which, when the chalk was forming, flowed over the site of Hastings. +While all around has changed, this Terebratulina has peacefully +propagated its species from generation to generation, and stands to +this day as a living testimony to the continuity of the present with +the past history of the globe. + + * * * * * + +Up to this moment I have stated, so far as I know, nothing but +well-authenticated facts, and the immediate conclusions which they +force upon the mind. + +But the mind is so constituted that it does not willingly rest in +facts and immediate causes, but seeks always after a knowledge of the +remoter links in the chain of causation. + +Taking the many changes of any given spot of the earth's surface, from +sea to land, and from land to sea, as an established fact, we cannot +refrain from asking ourselves how these changes have occurred. And +when we have explained them--as they must be explained--by the +alternate slow movements of elevation and depression which have +affected the crusts of the earth, we go still further back, and ask, +Why these movements? + +I am not certain that any one can give you a satisfactory answer to +that question. Assuredly I cannot. All that can be said for certain +is, that such movements are part of the ordinary course of nature, +inasmuch as they are going on at the present time. Direct proof may be +given, that some parts of the land of the northern hemisphere are at +this moment insensibly rising and others insensibly sinking; and there +is indirect but perfectly satisfactory proof, that an enormous area +now covered by the Pacific has been deepened thousands of feet since +the present inhabitants of that sea came into existence. + +Thus there is not a shadow of a reason for believing that the +physical changes of the globe, in past times, have been effected by +other than natural causes. + +Is there any more reason for believing that the concomitant +modifications in the forms of the living inhabitants of the globe have +been brought about in any other ways? + +Before attempting to answer this question, let us try to form a +distinct mental picture of what has happened in some special case. + +The crocodiles are animals which, as a group, have a very vast +antiquity. They abounded ages before the chalk was deposited; they +throng the rivers in warm climates at the present day. There is a +difference in the form of the joints of the backbone, and in some +minor particulars, between the crocodiles of the present epoch and +those which lived before the chalk; but, in the cretaceous epoch, as I +have already mentioned, the crocodiles had assumed the modern type of +structure. Notwithstanding this, the crocodiles of the chalk are not +identically the same as those which lived in the times called "older +tertiary," which succeeded the cretaceous epoch; and the crocodiles of +the older tertiaries are not identical with those of the newer +tertiaries, nor are these identical with existing forms. I leave open +the question whether particular species may have lived on from epoch +to epoch. But each epoch has had its peculiar crocodiles; though all, +since the chalk, have belonged to the modern type, and differ simply +in their proportions and in such structural particulars as are +discernible only to trained eyes. + +How is the existence of this long succession of different species of +crocodiles to be accounted for? + +Only two suppositions seem to be open to us--either each species of +crocodile has been specially created, or it has arisen out of some +pre-existing form by the operation of natural causes. + +Choose your hypothesis; I have chosen mine. I can find no warranty for +believing in the distinct creation of a score of successive species of +crocodiles in the course of countless ages of time. Science gives no +countenance to such a wild fancy; nor can even the perverse ingenuity +of a commentator pretend to discover this sense, in the simple words +in which the writer of Genesis records the proceeding of the fifth and +sixth days of the Creation. + +On the other hand, I see no good reason for doubting the necessary +alternative, that all these varied species have been evolved from +pre-existing crocodilian forms by the operation of causes as +completely a part of the common order of nature as those which have +effected the changes of the inorganic world. + +Few will venture to affirm that the reasoning which applies to +crocodiles loses its force among other animals or among plants. If one +series of species has come into existence by the operation of natural +causes, it seems folly to deny that all may have arisen in the same +way. + + * * * * * + +A small beginning has led us to a great ending. If I were to put the +bit of chalk with which we started into the hot but obscure flame of +burning hydrogen, it would presently shine like the sun. It seems to +me that this physical metamorphosis is no false image of what has been +the result of our subjecting it to a jet of fervent, though nowise +brilliant, thought to-night. It has become luminous, and its clear +rays, penetrating the abyss of the remote past, have brought within +our ken some stages of the evolution of the earth. And in the shifting +"without haste, but without rest" of the land and sea, as in the +endless variation of the forms assumed by living beings, we have +observed nothing but the natural product of the forces originally +possessed by the substance of the universe. + +[Illustration] + + + + +A BIT OF SPONGE + +(Written on Scotland.) + +(FROM GLIMPSES OF NATURE.) + +BY A. WILSON. + + +[Illustration] + +This morning, despite the promise of rain over-night, has broken with +all the signs and symptoms of a bright July day. The Firth is bathed +in sunlight, and the wavelets at full tide are kissing the strand, +making a soft musical ripple as they retire, and as the pebbles run +down the sandy slope on the retreat of the waves. Beyond the farthest +contact of the tide is a line of seaweed dried and desiccated, mixed +up with which, in confusing array, are masses of shells, and such +_olla podrida_ of the sea. + +Tossed up at our very feet is a dried fragment of sponge, which +doubtless the unkind waves tore from its rocky bed. It is not a large +portion of sponge this, but its structure is nevertheless to be fairly +made out, and some reminiscences of its history gleaned, for the sake +of occupying the by no means "bad half-hour" before breakfast. "What +is a sponge?" is a question which you may well ask as a necessary +preliminary to the understanding of its personality. + +[Illustration: A SPONGE ATTACHED TO ITS ROCKY BED.] + +The questionings of childhood and the questionings of science run in +precisely similar grooves. "What is it?" and "How does it live?" and +"Where does it come from?" are equally the inquiries of childhood, and +of the deepest philosophy which seeks to determine the whole history +of life. This morning, we cannot do better than follow in the +footsteps of the child, and to the question, "What is a sponge?" I +fancy science will be able to return a direct answer. First of all, we +may note that a sponge, as we know it in common life, is the horny +skeleton or framework which was made by, and which supported, the +living parts. These living parts consist of minute masses of that +living jelly to which the name of _protoplasm_ has been applied. This, +in truth, is the universal matter of life. It is the one substance +with which life everywhere is associated, and as we see it simply in +the sponge, so also we behold it (only in more complex guise) in the +man. Now, the living parts of this dried cast-away sponge were found +both in its interior and on its surface. They lined the canals that +everywhere permeate the sponge-substance, and microscopic examination +has told us a great deal about their nature. + + +[Illustration: FIG. 1. DEVELOPMENT OF A SPONGE (_Olynthus_). 1. The +egg. 2, 3, and 4. The process of egg-division. 5 and 6. The +gastrula-stage. 7. The perfect sponge.] + +For, whether found in the canals of the sponge themselves, or embedded +in the sponge-substance, the living sponge-particles are represented +each by a semi-independent mass of protoplasm. So that the first view +I would have you take of the sponge as a living mass, is, that it is a +colony and not a single unit. It is composed, in other words, of +aggregated masses of living particles, which bud out one from the +other, and manufacture the supporting skeleton we know as "the sponge +of commerce" itself. Under the microscope, these living sponge-units +appear in various guises and shapes. Some of them are formless, and, +as to shape, ever-altering masses, resembling that familiar animalcule +of our pools we know as the _Amoeba_. These members of the +sponge-colony form the bulk of the population. They are embedded in +the sponge substance; they wander about through the meshes of the +sponge; they seize food and flourish and grow; and they probably also +give origin to the "eggs" from which new sponges are in due course +produced. + +More characteristic however, are certain units of this living +sponge-colony which live in the lining membrane of the canals. In +point of fact, a sponge is a kind of Venice, a certain proportion of +whose inhabitants, like those of the famous Queen of the Adriatic +herself, live on the banks of the waterways. Just as in Venice we find +the provisions for the denizens of the city brought to the inhabitants +by the canals, so from the water, which, as we shall see, is +perpetually circulating through a sponge, the members of the +sponge-colony receive their food. + +Look, again, at the sponge-fragment which lies before us. You perceive +half a dozen large holes or so, each opening on a little eminence, as +it were. These apertures, bear in mind, we call _oscula_. They are the +exits of the sponge-domain. But a close inspection of a sponge shows +that it is riddled with finer and smaller apertures. These latter are +the _pores_, and they form the entrances to the sponge-domain. + +On the banks of the canal you may see growing plentifully in summer +time a green sponge, which is the common fresh-water species. Now, if +you drop a living specimen of this species into a bowl of water, and +put some powdered indigo into the water, you may note how the currents +are perpetually being swept in by the pores and out by the oscula. In +every living sponge this perpetual and unceasing circulation of water +proceeds. This is the sole evidence the unassisted sight receives of +the vitality of the sponge-colony, and the importance of this +circulation in aiding life in these depths, to be fairly carried out +cannot readily be over-estimated. + +[Illustration: WHERE SPONGES GROW.] + +Let us now see how this circulation is maintained. Microscopically +regarded, we see here and there, in the sides of the sponge-passages, +little chambers and recesses which remind one of the passing-places in +a narrow canal. Lining these chambers, we see living sponge-units of a +type different from the shapeless specks we noted to occur in the +meshes of the sponge substance itself. The units of the recesses each +consist of a living particle, whose free extremity is raised into a +kind of collar, from which projects a lash-like filament known as a +flagellum. + +This lash is in constant movement. It waves to and fro in the water, +and the collection of lashes we see in any one chamber acts as a +veritable brush, which by its movement not only sweeps water in by the +pores, but sends it onwards through the sponge, and in due time sends +it out by the bigger holes, or oscula. This constant circulation in +the sponge discharges more than one important function. For, as +already noted, it serves the purpose of nutrition, in that the +particles on which sponge-life is supported are swept into the colony. + +Again, the fresh currents of water carry with them the oxygen gas +which is a necessity of sponge existence, as of human life; while, +thirdly, waste matters, inevitably alike in sponge and in man as the +result of living, are swept out of the colony, and discharged into the +sea beyond. Our bit of sponge has thus grown from a mere dry fragment +into a living reality. It is a community in which already, low as it +is, the work of life has come to be discharged by distinct and fairly +specialized beings. + +The era of new sponge-life is inaugurated by means of egg-development, +although there exists another fashion (that of gemmules or buds) +whereby out of the parental substance young sponges are produced. A +sponge-egg develops, as do all eggs, in a definite cycle. It undergoes +division (Fig. 1); its one cell becomes many; and its many cells +arrange themselves first of all into a cup-like form (5, 6 and 7), +which may remain in this shape if the sponge is a simple one, or +become developed into the more complex shape of the sponges we know. + +In every museum you may see specimens of a beautiful vase-like +structure seemingly made of spun-glass. This is a flinty sponge, the +"Venus flower-basket," whose presence in the sponge family redeems it +from the charge that it contains no things of beauty whatever. So, +too, the rocks are full of fossil-sponges, many of quaint form. Our +piece of sponge, as we may understand, has yet other bits of history +attached to it.... Meanwhile, think over the sponge and its ways, and +learn from it that out of the dry things of life, science weaves many +a fairy tale. + +[Illustration] + + + + +THE GREATEST SEA-WAVE EVER KNOWN + +(FROM LIGHT SCIENCE IN LEISURE HOURS.) + +BY R.A. PROCTOR. + + +[Illustration] + +August 13th, 1868, one of the most terrible calamities which has ever +visited a people befell the unfortunate inhabitants of Peru. In that +land earthquakes are nearly as common as rain storms are with us; and +shocks by which whole cities are changed into a heap of ruins are by +no means infrequent. Yet even in Peru, "the land of earthquakes," as +Humboldt has termed it, no such catastrophe as that of August, 1868, +had occurred within the memory of man. It was not one city which was +laid in ruins, but a whole empire. Those who perished were counted by +tens of thousands, while the property destroyed by the earthquake was +valued at millions of pounds sterling. + +Although so many months have passed since this terrible calamity took +place, scientific men have been busily engaged, until quite recently, +in endeavoring to ascertain the real significance of the various +events which were observed during and after the occurrence of the +earthquake. The geographers of Germany have taken a special interest +in interpreting the evidence afforded by this great manifestation of +Nature's powers. Two papers have been written recently on the great +earthquake of August 13th, 1868--one by Professor von Hochsteter, the +other by Herr von Tschudi, which present an interesting account of the +various effects, by land and by sea, which resulted from the +tremendous upheaving force to which the western flanks of the Peruvian +Andes were subjected on that day. The effects on land, although +surprising and terrible, only differ in degree from those which have +been observed in other earthquakes. But the progress of the great +sea-wave which was generated by the upheaval of the Peruvian shores +and propagated over the whole of the Pacific Ocean differs altogether +from any earthquake phenomena before observed. Other earthquakes have +indeed been followed by oceanic disturbances; but these have been +accompanied by terrestrial motions, so as to suggest the idea that +they had been caused by the motion of the sea-bottom or of the +neighboring land. In no instance has it ever before been known that a +well-marked wave of enormous proportions should have been propagated +over the largest ocean tract on our globe by an earth-shock whose +direct action was limited to a relatively small region, and that +region not situated in the centre, but on one side of the wide area +traversed by the wave. + +We propose to give a brief sketch of the history of this enormous +sea-wave. In the first place, however, it may be well to remind the +reader of a few of the more prominent features of the great shock to +which this wave owed its origin. + +It was at Arequipa, at the foot of the lofty volcanic mountain Misti, +that the most terrible effects of the great earthquake were +experienced. Within historic times Misti has poured forth no lava +streams, but that the volcano is not extinct is clearly evidenced by +the fact that in 1542 an enormous mass of dust and ashes was vomited +forth from its crater. On August 13th. 1868, Misti showed no signs of +being disturbed. So far as the volcanic neighbor was concerned, the +forty-four thousand inhabitants of Arequipa had no reason to +anticipate the catastrophe which presently befell them. At five +minutes past five an earthquake shock was experienced, which, though +severe, seems to have worked little mischief. Half a minute later, +however, a terrible noise was heard beneath the earth; a second shock +more violent than the first was felt, and then began a swaying motion, +gradually increasing in intensity. In the-course of the first minute +this motion had become so violent that the inhabitants ran in terror +out of their houses into the streets and squares. In the next two +minutes the swaying movement had so increased that the more lightly +built houses were cast to the ground, and the flying people could +scarcely keep their feet. "And now," says Von Tschudi, "there followed +during two or three minutes a terrible scene. The swaying motion which +had hitherto prevailed changed into fierce vertical upheaval. The +subterranean roaring increased in the most terrifying manner; then +were heard the heart-piercing shrieks of the wretched people, the +bursting of walls, the crashing fall of houses and churches, while +over all rolled thick clouds of a yellowish-black dust, which, had +they been poured forth many minutes longer, would have suffocated +thousands." Although the shocks had lasted but a few minutes, the whole +town was destroyed. Not one building remained uninjured, and there +were few which did not lie in shapeless heaps of ruins. + +At Tacna and Arica the earth-shock was less severe, but strange and +terrible phenomena followed it. At the former place a circumstance +occurred the cause and nature of which yet remain a mystery. About +three hours after the earthquake--in other words, at about eight +o'clock in the evening--an intensely brilliant light made its +appearance above the neighboring mountains. It lasted for fully half +an hour, and has been ascribed to the eruption of some as yet unknown +volcano. + +At Arica the sea-wave produced even more destructive effects than had +been caused by the earthquake. About twenty minutes after the first +earth-shock the sea was seen to retire, as if about to leave the +shores wholly dry; but presently its waters returned with tremendous +force. A mighty wave, whose length seemed immeasurable, was seen +advancing like a dark wall upon the unfortunate town, a large part of +which was overwhelmed by it. Two ships, the Peruvian corvette America, +and the United States "double-ender" Wateree, were carried nearly half +a mile to the north of Arica beyond the railroad which runs to Tacna, +and there left stranded high and dry. This enormous wave was +considered by the English vice-consul at Arica to have been fully +fifty feet in height. + +At Chala three such waves swept in after the first shocks of +earthquake. They overflowed nearly the whole of the town, the sea +passing more than half a mile beyond its usual limits. + +At Islay and Iquique similar phenomena were manifested. At the former +town the lava flowed in no less than five times, and each time with +greater force. Afterward the motion gradually diminished, but even an +hour and a half after the commencement of this strange disturbance the +waves still ran forty feet above the ordinary level. At Iquique the +people beheld the inrushing wave while it was still a great way off. A +dark blue mass of water some fifty feet in height was seen sweeping in +upon the town with inconceivable rapidity. An island lying before the +harbor was completely submerged by the great wave, which still came +rushing on black with the mud and slime it had swept from the +sea-bottom. Those who witnessed its progress from the upper balconies +of their houses, and presently saw its black mass rushing close +beneath their feet, looked on their safety as a miracle. Many +buildings were indeed washed away, and in the low-lying parts of the +town there was a terrible loss of life. After passing far inland, the +wave slowly returned sea-ward, and, strangely enough, the sea, which +elsewhere heaved and tossed for hours after the first great wave had +swept over it, here came soon to rest. + +At Callao a yet more singular instance was afforded of the effect +which circumstances may have upon the motion of the sea after a great +earthquake has disturbed it. In former earthquakes Callao has suffered +terribly from the effects of the great sea-wave. In fact, on two +occasions the whole town has been destroyed, and nearly all its +inhabitants have been drowned, through the inrush of precisely such +waves as flowed into the ports of Arica and Chala. But upon this +occasion the centre of subterranean disturbance must have been so +situated that either the wave was diverted from Callao, or, more +probably, two waves reached Callao from different sources and at +different times, so that the two undulations partly counteracted each +other. Certain it is that, although the water retreated strangely from +the coast near Callao, insomuch that a wide tract of the sea-bottom +was uncovered, there was no inrushing wave comparable with those +described above. The sea afterward rose and fell in an irregular +manner, a circumstance confirming the supposition that the disturbance +was caused by two distinct oscillations. Six hours after the +occurrence of the earth-shock the double oscillations seemed for a +while to have worked themselves into unison, for at this time three +considerable waves rolled in upon the town. But clearly these waves +must not be compared with those which in other instances had made +their appearance within half an hour of the earth-throes. There is +little reason to doubt that if the separate oscillations had +re-enforced each other earlier, Callao would have been completely +destroyed. As it was, a considerable amount of mischief was effected; +but the motion of the sea presently became irregular again, and so +continued until the morning of August 14th, when it began to ebb with +some regularity. But during the 14th there were occasional renewals of +the irregular motion, and several days elapsed before the regular ebb +and flow of the sea were resumed. + +Such were among the phenomena presented in the region where the +earthquake itself was felt. It will be seen at once that within this +region, or rather along that portion of the sea-coast which falls +within the central region of disturbance, the true character of the +sea-wave generated by the earthquake could not be recognized. If a +rock fall from a lofty cliff into a comparatively shallow sea, the +water around the place where the rock has fallen is disturbed in an +irregular manner. The sea seems at one place to leap up and down; +elsewhere one wave seems to beat against another, and the sharpest eye +can detect no law in the motion of the seething waters. But presently, +outside the scene of disturbance, a circular wave is seen to form, and +if the motion of this wave be watched it is seen to present the most +striking contrast with the turmoil and confusion at its centre. It +sweeps onward and outward in a regular undulation. Gradually it loses +its circular figure (unless the sea-bottom happens to be unusually +level), showing that although its motion is everywhere regular, it is +not everywhere equally swift. A wave of this sort, though incomparably +vaster, swept swiftly away on every side from the scene of the great +earthquake near the Peruvian Andes. It has been calculated that the +width of this wave varied from one million to five million feet, or, +roughly, from two hundred to one thousand miles, while, when in +mid-Pacific, the length of the wave, measured along its summit in a +widely-curved path from one side to another of the great ocean, +cannot have been less than eight thousand miles. + +[Illustration: OVER A LARGE PORTION OF ITS COURSE ITS PASSAGE WAS +UNNOTED.] + +We cannot tell how deep-seated was the centre of subterranean action; +but there can be no doubt it was very deep indeed, because otherwise +the shock felt in towns separated from each other by hundreds of miles +could not have been so nearly contemporaneous. Therefore the portion +of the earth's crust upheaved must have been enormous, for the length +of the region where the direct effects of the earthquake were +perceived is estimated by Professor von Hochsteter at no less than +two hundred and forty miles. The breadth of the region is unknown, +because the slope of the Andes on one side and the ocean on the other +concealed the motion of the earth's crust. + +The great ocean-wave swept, as we have said, in all directions around +the scene of the earth-throe. Over a large part of its course its +passage was unnoted, because in the open sea the effects even of so +vast an undulation could not be perceived. A ship would slowly rise as +the crest of the great wave passed under her, and then as slowly sink +again. This may seem strange, at first sight, when it is remembered +that in reality the great sea-wave we are considering swept at the +rate of three or four hundred sea-miles an hour over the larger part +of the Pacific. But when the true character of ocean-waves is +understood, when it is remembered that there is no transference of the +water itself at this enormous rate, but simply a transmission of +motion (precisely as when in a high wind waves sweep rapidly over a +cornfield, while yet each cornstalk remains fixed in the ground), it +will be seen that the effects of the great sea-wave could only be +perceived near the shore. Even there, as we shall presently see, there +was much to convey the impression that the land itself was rising and +falling rather than that the deep was moved. But among the hundreds of +ships which were sailing upon the Pacific when its length and breadth +were traversed by the great sea-wave, there was not one in which any +unusual motion was perceived. + +In somewhat less than three hours after the occurrence of the +earthquake the ocean-wave inundated the port of Coquimbo, on the +Chilean seaboard, some eight hundred miles from Arica. An hour or so +later it had reached Constitucion, four hundred and fifty miles +farther south; and here for some three hours the sea rose and fell +with strange violence. Farther south, along the shore of Chile, even +to the island of Chiloe, the shore-wave travelled, though with +continually diminishing force, owing, doubtless, to the resistance +which the irregularities of the shore opposed to its progress. + +The northerly shore-wave seems to have been more considerable; and a +moment's study of a chart of the two Americas will show that this +circumstance is highly significant. When we remember that the +principal effects of the land-shock were experienced within that angle +which the Peruvian Andes form with the long north-and-south line of +the Chilean and Bolivian Andes, we see at once that, had the centre of +the subterranean action been near the scene where the most destructive +effects were perceived, no sea-wave, or but a small one, could have +been sent toward the shores of North America. The projecting shores of +northern Peru and Ecuador could not have failed to divert the sea-wave +toward the west; and though a reflected wave might have reached +California, it would only have been after a considerable interval of +time, and with dimensions much less than those of the sea-wave which +travelled southward. When we see that, on the contrary, a wave of even +greater proportions travelled toward the shores of North America, we +seem forced to the conclusion that the centre of the subterranean +action must have been so far to the west that the sea-wave generated +by it had a free course to the shores of California. + +Be this as it may, there can be no doubt that the wave which swept the +shores of Southern California, rising upward of sixty feet above the +ordinary sea-level, was absolutely the most imposing of all the +indirect effects of the great earthquake. When we consider that even +in San Pedro Bay, fully five thousand miles from the centre of +disturbance, a wave twice the height of an ordinary house rolled in +with unspeakable violence only a few hours after the occurrence of the +earth-throe, we are most strikingly impressed with the tremendous +energy of the earth's movement. + +Turning to the open ocean, let us track the great wave on its course +past the multitudinous islands which dot the surface of the Pacific. + +The inhabitants of the Sandwich Islands, which lie about six thousand +three hundred miles from Arica, might have imagined themselves safe +from any effects which could be produced by an earthquake taking place +so far away from them. But on the night between August 13th and 14th, +the sea around this island group rose in a surprising manner, insomuch +that many thought the islands were sinking, and would shortly subside +altogether beneath the waves. Some of the smaller islands, indeed, +were for a time completely submerged. Before long, however, the sea +fell again, and as it did so the observers "found it impossible to +resist the impression that the islands were rising bodily out of the +water." For no less than three days this strange oscillation of the +sea continued to be experienced, the most remarkable ebbs and floods +being noticed at Honolulu, on the island of Woahoo. + +But the sea-wave swept onward far beyond these islands. + +At Yokohama, in Japan, more than ten thousand five hundred miles from +Arica, an enormous wave poured in on August 14th, but at what hour we +have no satisfactory record. So far as distance is concerned, this +wave affords most surprising evidence of the stupendous nature of the +disturbance to which the waters of the Pacific Ocean had been +subjected. The whole circumference of the earth is but twenty-five +thousand miles, so that this wave had travelled over a distance +considerably greater than two-fifths of the earth's circumference. A +distance which the swiftest of our ships could not traverse in less +than six or seven weeks had been swept over by this enormous +undulation in the course of a few hours. + +More complete details reach us from the Southern Pacific. + +Shortly before midnight the Marquesas Isles and the low-lying Tuamotu +group were visited by the great wave, and some of these islands were +completely submerged by it. The lonely Opara Isle, where the steamers +which run between Panama and New Zealand have their coaling station, +was visited at about half-past eleven in the evening by a billow which +swept away a portion of the coal depot. Afterward great waves came +rolling in at intervals of about twenty minutes, and several days +elapsed before the sea resumed its ordinary ebb and flow. + +It was not until about half-past two on the morning of August 14th +that the Samoa Isles (sometimes called the Navigator Islands) were +visited by the great wave. The watchmen startled the inhabitants from +their sleep by the cry that the sea was about to overwhelm them; and +already, when the terrified people rushed from their houses, the sea +was found to have risen far above the highest water-mark. But it +presently began to sink again, and then commenced a series of +oscillations, which lasted for several days, and were of a very +remarkable nature. Once in every quarter of an hour the sea rose and +fell, but it was noticed that it rose twice as rapidly as it sank. +This peculiarity is well worth remarking. The eminent physicist Mallet +speaks thus (we follow Lyell's quotation) about the waves which +traverse an open sea: "The great sea-wave, advancing at the rate of +several miles in a minute, consists, in the deep ocean, of a long, low +swell of enormous volume, having an equal slope before and behind, and +that so gentle that it might pass under a ship without being noticed. +But when it reaches the edge of soundings, its front slope becomes +short and steep, while its rear slope is long and gentle." On the +shores visited by such a wave, the sea would appear to rise more +rapidly than it sank. We have seen that this happened on the shores of +the Samoa group, and therefore the way in which the sea rose and fell +on the days following the great earthquake gave significant evidence +of the nature of the sea-bottom in the neighborhood of these islands. +As the change of the great wave's figure could not have been quickly +communicated, we may conclude with certainty that the Samoan Islands +are the summits of lofty mountains, whose sloping sides extend far +toward the east. + +This conclusion affords interesting evidence of the necessity of +observing even the seemingly trifling details of important phenomena. + +The wave which visited the New Zealand Isles was altogether different +in character, affording a noteworthy illustration of another remark of +Mallet's. He says that where the sea-bottom slopes in such a way that +there is water of some depth close inshore, the great wave may roll in +and do little damage; and we have seen that so it happened in the case +of the Samoan Islands. But he adds that, "where the shore is shelving +there will be first a retreat of the water, and then the wave will +break upon the beach and roll far in upon the land." This is precisely +what happened when the great wave reached the eastern shores of New +Zealand, which are known to shelve down to very shallow water, +continuing far away to sea toward the east. + +At about half-past three on the morning of August 14th the water began +to retreat in a singular manner from the port of Littleton, on the +eastern shores of the southernmost of the New Zealand Islands. At +length the whole port was left entirely dry, and so remained for about +twenty minutes. Then the water was seen returning like a wall of foam +ten or twelve feet in height, which rushed with a tremendous noise +upon the port and town. Toward five o'clock the water again retired, +very slowly as before, not reaching its lowest ebb until six. An hour +later a second huge wave inundated the port. Four times the sea +retired and returned with great power at intervals of about two hours. +Afterward the oscillation of the water was less considerable, but it +had not wholly ceased until August 17th, and only on the 18th did the +regular ebb and flow of the tide recommence. + +Around the Samoa group the water rose and fell once in every fifteen +minutes, while on the shores of New Zealand each oscillation lasted no +less than two hours. Doubtless the different depths of water, the +irregular conformation of the island groups, and other like +circumstances, were principally concerned in producing these singular +variations. Yet they do not seem fully sufficient to account for so +wide a range of difference. Possibly a cause yet unnoticed may have +had something to do with the peculiarity. In waves of such enormous +extent it would be quite impossible to determine whether the course of +the wave motion was directed full upon a line of shore or more or less +obliquely. It is clear that in the former case the waves would seem to +follow each other more swiftly than in the latter, even though there +were no difference in their velocity. + +Far on beyond the shores of New Zealand the great wave coursed, +reaching at length the coast of Australia. At dawn of August 14th +Moreton Bay was visited by five well-marked waves. At Newcastle, on +the Hunter River, the sea rose and fell several times in a remarkable +manner, the oscillatory motion commencing at half-past six in the +morning. But the most significant evidence of the extent to which the +sea-wave travelled in this direction was afforded at Port Fairy, +Belfast, South Victoria. Here the oscillation of the water was +distinctly perceived at midday on August 14th; and yet, to reach this +point, the sea-wave must not only have travelled on a circuitous +course nearly equal in length to half the circumference of the earth, +but must have passed through Bass's Straits, between Australia and Van +Diemen's Land, and so have lost a considerable portion of its force +and dimensions. When we remember that had not the effects of the +earth-shock on the water been limited by the shores of South America, +a wave of disturbance equal in extent to that which travelled westward +would have swept toward the east, we see that the force of the shock +was sufficient to have disturbed the waters of an ocean covering the +whole surface of the earth. For the sea-waves which reached Yokohama +in one direction and Port Fairy in another had each traversed a +distance nearly equal to half the earth's circumference; so that if +the surface of the earth were all sea, waves setting out in opposite +directions from the centre of disturbance would have met each other at +the antipodes of their starting-point. + +It is impossible to contemplate the effects which followed the great +earthquake--the passage of a sea-wave of enormous volume over fully +one third of the earth's surface, and the force with which, on the +farthermost limits of its range, the wave rolled in upon shores more +than ten thousand miles from its starting-place--without feeling that +those geologists are right who deny that the subterranean forces of +the earth are diminishing in intensity. It may be difficult, perhaps, +to look on the effects which are ascribed to ancient earth-throes +without imagining for a while that the power of modern earthquakes is +altogether less. But when we consider fairly the share which time had +in those ancient processes of change, when we see that while mountain +ranges were being upheaved or valleys depressed to their present +position, race after race, and type after type appeared on the earth, +and lived out the long lives which belong to races and to types, we +are recalled to the remembrance of the great work which the earth's +subterranean forces are still engaged upon. Even now continents are +being slowly depressed or upheaved; even now mountain ranges are being +raised to a new level, tablelands are in process of formation, and +great valleys are being gradually scooped out. It may need an +occasional outburst, such as the earthquake of August, 1868, to remind +us that great forces are at work beneath the earth's surface. But, in +reality, the signs of change have long been noted. Old shore-lines +shift their place, old soundings vary; the sea advances in one place +and retires in another; on every side Nature's plastic hand is at work +modelling and remodelling the earth, in order that it may always be a +fit abode for those who are to dwell upon it. + +[Illustration] + + + + +THE PHOSPHORESCENT SEA + +(FROM STUDIES OF ANIMATED NATURE.) + +BY W.S. DALLAS. + + +[Illustration] + +It is not merely on land that this phenomenon of phosphorescence is to +be seen in living forms. Among marine animals, indeed, it is a +phenomenon much more general, much more splendid, and, we may add, +much more familiar to those who live on our coasts. There must be many +in the British Isles who have never had the opportunity of seeing the +light of the glow-worm, but there can be few of those who have +frequented in summer any part of our coasts, who have never seen that +beautiful greenish light which is then so often visible, especially on +our southern shores, when the water is disturbed by the blade of an +oar or the prow of a boat or ship. In some cases, even on our own +shores, the phenomenon is much more brilliant, every rippling wave +being crested with a line of the same peculiar light, and in warmer +seas exhibitions of this kind are much more common. It is now known +that this light is due to a minute living form, to which we will +afterward return. + +But before going on to speak in some detail of the organisms to which +the phosphorescence of the sea is due, it will be as well to mention +that the kind of phosphorescence just spoken of is only one mode in +which the phenomenon is exhibited on the ocean. Though sometimes the +light is shown in continuous lines whenever the surface is disturbed, +at other times, and, according to M. de Quatrefages, more commonly, +the light appears only in minute sparks, which, however numerous, +never coalesce. "In the little channel known as the Sund de Chausez," +he writes, "I have seen on a dark night each stroke of the oar kindle, +as it were, myriads of stars, and the wake of the craft appeared in a +manner besprinkled with diamonds." When such is the case the +phosphorescence is due to various minute animals, especially +crustaceans; that is, creatures which, microscopically small as they +are, are yet constructed more or less on the type of the lobster or +cray-fish. + +At other times, again, the phosphorescence is still more partial. +"Great domes of pale gold with long streamers," to use the eloquent +words of Professor Martin Duncan, "move slowly along in endless +succession; small silvery disks swim, now enlarging and now +contracting, and here and there a green or bluish gleam marks the +course of a tiny, but rapidly rising and sinking globe. Hour after +hour the procession passes by, and the fishermen hauling in their nets +from the midst drag out liquid light, and the soft sea jellies, +crushed and torn piecemeal, shine in every clinging particle. The +night grows dark, the wind rises and is cold, and the tide changes; so +does the luminosity of the sea. The pale spectres below the surface +sink deeper, and are lost to sight, but the increasing waves are +tinged here and there with green and white, and often along a line, +where the fresh water is mixing with the salt in an estuary, there is +a brightness so intense that boats and shores are visible.... But if +such sights are to be seen on the surface, what must not be the +phosphorescence of the depths! Every sea-pen is glorious in its light, +in fact, nearly every eight-armed Alcyonarian is thus resplendent, and +the social Pyrosoma, bulky and a free swimmer, glows like a bar of hot +metal with a white and green radiance." + +Such accounts are enough to indicate how varied and how general a +phenomenon is the phosphorescence of the sea. To take notice of one +tithe of the points of interest summed up in the paragraph just quoted +would occupy many pages, and we must therefore confine the attention +to a few of the most interesting facts relating to marine +phosphorescence. + +We will return to that form of marine luminosity to which we first +referred: what is known as the general or diffused phosphorescence of +the sea. From this mode of describing it the reader must not infer +that the surface of the ocean is ever to be seen all aglow in one +sheet of continuous light. So far, at least, as was ever observed by +M. de Quatrefages, who studied this phenomenon carefully and during +long periods on the coasts of Brittany and elsewhere, no light was +visible when the surface of the sea was perfectly still. On the other +hand, when the sea exhibits in a high degree the phenomenon of +diffused phosphorescence no disturbance can be too slight to cause the +water to shine with that peculiar characteristic gleam. Drop but a +grain of sand upon its surface, and you will see a point of light +marking the spot where it falls, and from that point as a centre a +number of increasing wavelets, each clearly defined by a line of +light, will spread out in circles all around. + +The cause of this diffused phosphorescence was long the subject of +curiosity, and was long unknown, but more than a hundred years ago (in +1764) the light was stated by M. Kigaut to proceed from a minute and +very lowly organism, now known as _Noctiluca miliaris_; and subsequent +researches have confirmed this opinion. This Noctiluca is a spherical +form of not more than one-fiftieth of an inch in size, with a slight +depression or indentation at one point, marking the position of a +mouth leading to a short digestive cavity, and having close beside it +a filament, by means of which it probably moves about. The sphere is +filled with protoplasm, in which there is a nucleus and one or more +gaps, or "vacuoles." Such is nearly all the structure that can be +discerned with the aid of the microscope in this simple organism. + +Nevertheless, this lowly form is the chief cause of that diffused +phosphorescence which is sometimes seen over a wide extent of the +ocean. How innumerable the individuals belonging to this species must +therefore be, may be left to the imagination. Probably the Noctiluca +is not rivalled in this respect even by miscroscopic unicellular algæ +which compose the "red snow." + +By filtering sea-water containing Noctilucæ its light can be +concentrated, and it has been found that a few teaspoonfuls will then +yield light enough to enable one to read holding a book at the +ordinary distance from the eyes--about ten inches. + +A singular and highly remarkable case of diffused marine +phosphorescence was observed by Nordenskiöld during his voyage to +Greenland in 1883. One dark night, when the weather was calm and the +sea smooth, his vessel was steaming across a narrow inlet called the +Igaliko Fjord, when the sea was suddenly observed to be illumined in +the rear of the vessel by a broad but sharply-defined band of light, +which had a uniform, somewhat golden sheen, quite unlike the ordinary +bluish-green phosphorescence of the sea. The latter kind of light was +distinctly visible at the same time in the wake of the vessel. Though +the steamer was going at the rate of from five to six miles an hour, +the remarkable sheet of light got nearer and nearer. When quite close, +it appeared as if the vessel were sailing in a sea of fire or molten +metal. In the course of an hour the light passed on ahead, and +ultimately it disappeared in the remote horizon. The nature of this +phenomenon Nordenskiöld is unable to explain; and unfortunately he had +not the opportunity of examining it with the spectroscope. + +If we come now to consider the more partial phosphorescence of the +sea, we find that it is due to animals belonging to almost every group +of marine forms--to Echinoderms, or creatures of the sea-urchin and +star-fish type, to Annelid worm, to Medusidæ, or jelly-fish, as they +are popularly called, including the "great domes" and the "silvery +disks" of the passage above quoted from Professor Martin Duncan, to +Tunicates, among which is the Pyrosoma, to Mollusks, Crustaceans, and +in very many cases to Actinozoa, or forms belonging to the type of the +sea anemone and the coral polyp. + +Of these we will single out only a few for more special notice. + +Many of the Medusidæ, or jelly-fish, possess the character of which we +are speaking. In some cases the phosphorescence is spontaneous among +them, but in others it is not so; the creature requires to be +irritated or stimulated in some way before it will emit the light. It +is spontaneous, for example, in the _Pelagia phosphorea_, but not in +the allied _Pelagia noctiluca_, a very common form in the +Mediterranean. + +In both of the jelly-fishes just mentioned the phosphorescence, when +displayed at all, is on the surface of the swimming disk, and this is +most commonly the case with the whole group. Sometimes, however, the +phosphorescence is specially localized. In some forms, as in +_Thaumantius pilosella_ and other members of the same genus, it is +seen in buds at the base of tentacles given off from the margin of the +swimming-bell. In other cases it is situated in certain internal +organs, as in the canals which radiate from the centre to the margin +of the bell, or in the ovaries. It is from this latter seat that the +phosphorescence proceeds in _Oceania pilata_, the form which gives out +such a light that Ehrenberg compared it to a lamp-globe lighted by a +flame. + +The property of emitting a phosphorescent light, sometimes +spontaneously and sometimes on being stimulated, is likewise +exemplified in the Ctenophora, a group resembling the Medusidæ in +the jelly-like character of their bodies, but more closely allied in +structure to the Actinozoa. But we will pass over these cases in order +to dwell more particularly on the remarkable tunicate known as +Pyrosoma, a name indicative of its phosphorescent property, being +derived from two Greek words signifying fire-body. As shown in the +illustration Pyrosoma is not a single creature, but is composed of a +whole colony of individuals, each of which is represented by one of +the projections on the surface of the tube, closed at one end, which +they all combine to form. The free end on the exterior contains the +mouth, while there is another opening in each individual toward the +interior of the tube. Such colonies, which swim about by the alternate +contraction and dilatation of the individuals composing them, are +pretty common in the Mediterranean, where they may attain the length +of perhaps fourteen inches, with a breadth of about three inches. In +the ocean they may reach a much greater size. Mr. Moseley, in his +"Notes of a Naturalist on the Challenger," mentions a giant specimen +which he once caught in the deep-sea trawl, a specimen four feet in +length and ten inches in diameter, with "walls of jelly about an inch +in thickness." + +[Illustration: A. PYROSOMA. B. PONITON. (Magnified.)] + +The same naturalist states that the light emitted by this compound +form is the most beautiful of all kinds of phosphorescence. When +stimulated by a touch, or shake, or swirl of the water, it "gives out +a globe of bluish light, which lasts for several seconds, as the +animal drifts past several feet beneath the surface, and then suddenly +goes out." He adds that on the giant specimen just referred to be +wrote his name with his finger as it lay on the deck in a tub at +night, and in a few seconds he had the gratification of seeing his +name come out in "letters of fire." + +Among mollusks, the best known instance of phosphorescence is in the +rock-boring Pholas, the luminosity of which after death is mentioned +by Pliny. But it is not merely after death that Pholas becomes +luminous--a phenomenon perfectly familiar even in the case of many +fish, especially the herring and mackerel. It was long before the +luminosity of the living animal was known, but this is now a +well-ascertained fact; and Panceri, an Italian naturalist, recently +dead, has been able to discover in this, as in several other marine +phosphorescent forms, the precise seat of the light-giving bodies, +which he has dissected out again and again for the sake of making +experiments in connection with this subject. + +A more beautiful example of a phosphorescent mollusk is presented by a +sea-slug called _Phyllirhoë bucephala_. This is a creature of from one +and a half to two inches in length, without a shell in the adult +stage, and without even gills. It breathes only by the general surface +of the body. It is common enough in the Mediterranean, but is not easy +to see, as it is almost perfectly transparent, so that it cannot be +distinguished without difficulty, by day at least, from the medium in +which it swims. By night, however, it is more easily discerned, in +consequence of its property of emitting light. When disturbed or +stimulated in any way, it exhibits a number of luminous spots of +different sizes irregularly distributed all over it, but most thickly +aggregated on the upper and under parts. These phosphorescent spots, +it is found, are not on the surface, but for the most part represent +so many large cells which form the terminations of nerves, and are +situated underneath the transparent cuticle. The spots shine with +exceptional brilliancy when the animal is withdrawn from the water and +stimulated by a drop of ammonia. + +Among the Annelid worms a species of _Nereis_, or sea-centipedes, has +earned by its phosphorescent property the specific name of _noctiluca_ +(night-shining), and the same property is very beautifully shown in +_Polynoë_, a near ally of the familiar sea-mouse. M. de Quatrefages +speaks with enthusiasm of the beauty of the spectacle presented by +this latter form when examined under a microscope magnifying to the +extent of a hundred diameters. He then found, as he did in the great +majority of cases which he studied, that the phosphorescence was +confined to the motor muscles, and was manifested solely when these +were in the act of contracting, manifested, too, not in continuous +lines along the course of the muscles, but in rows of brilliant +points. + +More interesting than the Annelids, however, are the Alcyonarian +Actinozoa. The Actinozoa have already been described as formed on the +type of the sea-anemone and the coral polyp, that is, they are all +animals with a radiate structure, attached to one end, and having +their only opening at the other end, which is surrounded by tentacles. +In the Alcyonarian forms belonging to this great group these tentacles +are always eight in number, and fringed on both sides. Moreover, these +forms are almost without exception compound. Like the Pyrosoma, they +have a common life belonging to a whole stock or colony, as well as an +individual life. + +Now, throughout this sub-division of the Actinozoa phosphorescence is +a very general phenomenon. Professor Moseley, already quoted as a +naturalist accompanying the Challenger expedition, informs us that +"all the Alcyonarians dredged by the Challenger in deep water were +found to be brilliantly phosphorescent when brought to the surface." + +Among these Alcyonarians are the sea-pens mentioned in the quotation +above made from Professor Martin Duncan. Each sea-pen is a colony of +Alcyonarians, and the name is due to the singular arrangement of the +individuals upon the common stem. This stem is supported internally by +a coral rod, but its outer part is composed of fleshy matter belonging +to the whole colony. The lower portion of it is fixed in the muddy +bottom of the sea, but the upper portion is free, and gives off a +number of branches, on which the individual polyps are seated. The +whole colony thus has the appearance of a highly ornamental pen. + +There is one British species, _Pennatula phosphorea_, which is found +in tolerably deep water, and is from two to four inches in length. The +specific name again indicates the phosphorescent quality belonging to +it. When irritated, it shines brilliantly, and the curious thing is +that the phosphorescence travels gradually on from polyp to polyp, +starting from the point at which the irritation is applied. If the +lower part of the stem is irritated, the phosphorescence passes +gradually upwards along each pair of branches in succession; but if +the top is irritated the phosphorescence will pass in the same way +downwards. When both top and bottom are irritated simultaneously two +luminous currents start at once, and, meeting in the middle, usually +become extinguished there; but on one occasion Panceri found that the +two crossed, and each completed its course independently of the other. +Those of our readers who have had opportunities of making or seeing +experiments with the sensitive plant (_Mimosa pudica_) will be +reminded of the way in which, when that plant is irritated, the +influence travels regularly on from pinnules to pinnules and pinnae to +pinnae. + +In all the cases mentioned the phenomenon of phosphorescence is +exhibited by invertebrate animals; but though rare, it is not an +unknown phenomenon even in living vertebrates. In a genus of deep-sea +fishes called Stomias, Gunther mentions that a "series of +phosphorescent dots run along the lower side of the head, body, and +tail." Several other deep-sea fishes, locally phosphorescent, seem to +have been dredged up by the French ship Talisman in its exploring +cruise off the west coast of Northern Africa in 1883. During the same +expedition, a number of deep-sea phosphorescent crustaceans were +dredged up, the phosphorescence being in some cases diffused over the +whole body, in other cases localized to particular areas. In deep-sea +forms the phenomenon is, in fact, so common, as to have given rise to +the theory that in the depths of the ocean, where the light of the +sun cannot penetrate, the phosphorescence of various organisms diffuse +a light which limits the domain of absolute darkness. + +So much by way of illustration regarding the phosphorescence exhibited +by animals, terrestrial and marine; but it ought to be noticed that +there are also a few cases in which the same phenomenon is to be +witnessed in plants. These are not so numerous as was at one time +supposed, the property having been mistakenly ascribed to some plants +not really luminous. + +[Illustration: A PHOSPHORESCENT SEA.] + +In some instances the mistake appears to have been due to a subjective +effect produced by brilliantly colored (red or orange) flowers, such +as the great Indian cress, the orange lily, the sunflower, and the +marigold. The fact that such flowers do give out in the dusk sudden +flashes of light has often been stated on the authority of a daughter +of Linnæus, subsequently backed by the assertions of various other +observers. But most careful observers seem to be agreed that the +supposed flashes of light are in reality nothing else than a certain +dazzling of the eyes. + +In another case, in which a moss, _Schistostega osmundacea_, has been +stated to be phosphorescent, the effect is said to be really due to +the refraction and reflection of light by minute crystals scattered +over its highly cellular leaves, and not to be produced at all where +the darkness is complete. + +Among plants, genuine phosphorescence is to be found chiefly in +certain fungi, the most remarkable of which is _Rhizomorpha +subterranea_, which is sometimes to be seen ramifying over the walls +of dark, damp mines, caverns, or decayed towers, and emitting at +numerous points a mild phosphorescent light, which is sometimes bright +enough to allow of surrounding objects being distinguished by it. The +name of "vegetable glow-worm" has sometimes been applied to this +curious growth. + +Among other phosphorescent fungi are several species of Agaricus, +including the _A. olearius_ of Europe, _A. Gardneri_ of Brazil, and +_A. lampas_ of Australia, and besides the members of this genus, +_Thelaphora cærulea_, which is the cause of the phosphorescent light +sometimes to be seen on decaying wood--the "touchwood" which many boys +have kept in the hope of seeing this light displayed. The milky juice +of a South American Euphorbia (_E. phosphorea_) is stated by Martins +to be phosphorescent when gently heated. But phosphorescence is +evidently not so interesting and important a phenomenon in the +vegetable as it is in the animal kingdom. + +The whole phenomenon is one that gives rise to a good many questions +which it is not easy to answer, and this is especially true in the +case of animal phosphorescence. What is the nature of the light? What +are the conditions under which it is manifested? What purpose does it +serve in the animal economy? + +As to the nature of the light, the principal question is whether it is +a direct consequence of the vital activity of the organism in which it +is seen, of such a nature that no further explanation can be given of +it, any more than we can explain why a muscle is contracted under the +influence of a nerve-stimulus; or whether it is due to some chemical +process more or less analogous to the burning of a candle. + +The fact of luminosity appearing to be in certain cases directly under +the control of the creature in which it is found, and the fact of its +being manifested in many forms, as M. de Quatrefages found, only when +muscular contraction was taking place, would seem to favor the former +view. On the other hand, it is against this view that the +phosphorescence is often found to persist after the animal is dead, +and even in the phosphorescent organs for a considerable time after +they have been extracted from the body of the animal. In the glow-worm +the light goes on shining for some time after the death of the insect, +and even when it has become completely extinguished it can be restored +for a time by the application of a little moisture. Further, both +Matteucci and Phipson found that when the luminous substance was +extracted from the insect it would keep on glowing for thirty or forty +minutes. + +In Pholas the light is still more persistent, and it is found that +when the dead body of this mollusk is placed in honey, it will retain +for more than a year the power of emitting light when plunged in warm +water. + +The investigations of recent years have rendered it more and more +probable that the light exhibited by phosphorescent organisms is due +to a chemical process somewhat analogous to that which goes on in the +burning of a candle. This latter process is one of rapid oxidation. +The particles of carbon supplied by the oily matter that feeds the +candle become so rapidly combined with oxygen derived from the air +that a considerable amount of light, along with heat, is produced +thereby. Now, the phenomenon of phosphorescence in organic forms, +whether living or dead, appears also to be due to a process of +oxidation, but one that goes on much more slowly than in the case of a +lighted candle. It is thus more closely analogous to what is observed +in the element phosphorus itself, which owes its name (meaning +"light-bearer") to the fact that when exposed to the air at ordinary +temperatures it glows in the dark, in consequence of its becoming +slowly combined with oxygen. + +At one time it was believed that the presence of oxygen was not +necessary to the exhibition of phosphorescence in organic forms, but +it has now been placed beyond doubt that this is a mistake. Oxygen has +been proved to be indispensable, and hence we see a reason for the +luminous organs in the glow-worm being so intimately connected, as +above mentioned, with the air-tubes that ramify through the insect. + +This fact of itself might be taken as a strong indication of the +chemical nature of the process to which phosphorescence is due. But +the problem has been made the subject of further investigations which +have thrown more light upon it. It was long known that there were +various inorganic bodies besides phosphorus which emitted a +phosphorescent light in the dark, at least after being exposed to the +rays of the sun; but it was not till quite recently that any organic +compound was known to phosphoresce at ordinary temperatures. + +This discovery was made by a Polish chemist, named Bronislaus +Radziszewski, who followed it up with a long series of experiments on +the phosphorescence of organic compounds, by which he was able to +determine the conditions under which that phenomenon was exhibited. In +all the substances investigated by him in which phosphorescence was +introduced he found that three conditions were essential to its +production: (1) that oxygen should be present; (2) that there should +be an alkaline reaction in the phosphorescing mixture--that is, a +reaction such as is produced on acids and vegetable coloring matters +by potash, soda, and the other alkalies; and (3) that some kind of +chemical action should take place. + +He found, moreover, that among the organic compounds that could be +made to phosphoresce under these conditions were nearly all the fixed +and ethereal oils. With reference to the phosphorescence of animals, +this observation is important, for it has been shown in a great many +cases that a fatty substance forms the main constituent in their +luminous organs. This has long been known to be the case in the +luminous insects belonging to the Lampyridæ and Elateridæ, as well as +in the luminous centipedes; and the researches of Panceri, already +referred to, on the luminous organs of many marine forms have shown +that it holds good with regard to these also. + +We may, therefore, conclude that substances fitted to phosphoresce +under the conditions determined by the experiments of Radziszewski are +generally, and probably universally, present in the luminous organs of +phosphorescent animals. Now, what is to be said as to the occurrence +of these conditions? The access of oxygen is in all cases easy to +account for, but it must also be shown how the alkaline reaction is to +be produced. We need not expect to find in animal organisms potash, +soda, ammonia, and the other common alkalies; but it was established +by experiment that the alkaline organic compounds cholin and neurin, +which are present in animal tissues, would also serve to bring about +the phenomenon of phosphorescence in the substances on which the +experiments were made. + +Accordingly, it seems fair to conclude that when all these conditions +for the production of phosphorescence in a chemical laboratory are +present in animal organisms, the phenomenon, when observed in these, +is exactly of the same nature as that which is produced artificially. +By that it is meant that animal phosphorescence is attended, like the +artificial phenomenon, by a slow chemical action, or in other words, +that the phosphorescent light is due to a gradual process of +oxidation. + +One curious circumstance has been discovered which lends still further +probability to this explanation. It was mentioned above that among +phosphorescent plants there are several species of Agaricus. Now, +from one species of this genus, though not indeed one of the +phosphorescent species (from _A. muscarius_) there has been extracted +a principle called _amanitia_, which is found to be identical with +cholin. In the light of the results derived from the investigations +just referred to it is reasonable to draw the conclusion that, if +sought for, this principle would likewise be found in the +phosphorescent species in which the other conditions of +phosphorescence are also present. + +On this theory of the production of the phenomenon now under +consideration, the effect of shaking or of vital action in giving rise +to or intensifying the exhibition of the light is accounted for by the +fact that by these means fresh supplies of oxygen are brought into +contact with the phosphorescent substance. The effect of ammonia on +the light emitted by the sea-slug _Phyllirhoë bucephala_, is also +fully explained, ammonia being one of those alkaline substances which +are so directly favorable to the exhibition of the phenomenon. + +Nor is it difficult to account for the control which in some cases +insects appear to have over the luminosity of the phosphorescent +organs, exhibiting and withdrawing the light at will. It is not +necessary to suppose that this is an immediate effect, a conversion of +nerve force into light, and a withdrawal of that force. The action of +the creature's will may be merely in maintaining or destroying the +conditions under which the light is manifested. It may, for example, +have the power of withdrawing the supply of oxygen, and this +supposition receives some countenance from the observation cited from +Kirby and Spence on the two captured glow-worms, one of which +withdrew its light, while the other kept it shining, but while doing +so had the posterior extremity of the abdomen in constant motion. But +the animal may also have the power in another way of affecting the +chemical conditions of the phenomenon. It may, for example, have the +power of increasing or diminishing by some nervous influence the +supply of the necessary alkaline ingredient. + +But if animal phosphorescence is really due to a process of slow +oxidation, there is one singular circumstance to be noted in +connection with it. Oxidation is a process that is normally +accompanied by the development of heat. Even where no light is +produced an increase of temperature regularly takes place when +substances are oxidized. We ought, then, to expect such a rise of +temperature when light is emitted by the phosphorescent organs of +animals. But the most careful observations have shown that nothing of +the kind can be detected. It was with a view to test this that Panceri +dissected out the luminous organs of so many specimens of Pholas. He +selected this mollusk because it was so abundant in the neighborhood +of Naples, where, his experiments were made; and in making his +experiments he made use of a thermopile, an apparatus by which, with +the aid of electricity, much smaller quantities of heat can be +indicated than by means of the most delicate thermometer. The organs +remained luminous long after they were extracted, but no rise in +temperature whatever could be found to accompany the luminosity. Many +experiments upon different animals were made with similar negative +results by means of the thermometer. + +The only explanation of this that can be given is probably to be found +in the fact that the chemical process ascertained to go on in the +phosphorescence of organic compounds on which experiments were made in +the laboratory is an extremely slow one. + +The so-called phosphorescence of most inorganic bodies is one of a +totally different nature from that exhibited in organic forms. The +diamond shines for a time in the dark after it has been exposed to the +sun; so do pieces of quartz when rubbed together, and powdered +fluor-spar when heated shines with considerable brilliancy. Various +artificial compounds, such as sulphide of calcium (Canton's +phosphorus, as it is called from the discoverer), sulphate of barium +(Bologna stone, or Bologna phosphorus), sulphide of strontium, etc., +after being illuminated by the rays of the sun, give out in the dark a +beautiful phosphorescence, green, blue, violet, orange, red, according +to circumstances. The luminous paint which has recently attracted so +much attention is of the same nature. In these cases what we have is +either a conversion of heat rays into light rays (as in the powdered +fluor-spar), or the absorption and giving out again of sun-rays. In +the latter case the phenomenon is essentially the same as +fluorescence, in which the dark rays of the solar spectrum beyond the +violet are made visible. + +But we must now return to the other questions that have been started +in relation to phosphorescence in animals. There has been much +speculation as to the object of this light, and to the purposes it +serves in Nature. Probably no general answer can be given to this +question. It is no doubt impossible to show why so many animals have +been endowed with this remarkable property; but we may consider some +of the effects which the possession of it has in different cases. + +In the first place, it will undoubtedly serve in many cases to afford +light to enable the animal to see by, and in the Lampyridæ it would +seem that the degree of luminosity is related to the development of +the vision. In that family, according to the Rev. H.S. Gorham, the +eyes are developed, as a rule, in inverse proportion to the +luminosity. Where there is an ample supply of this kind of light the +eyes are small, but where the light is insignificant the eyes are +large by way of compensation. And moreover, where both eyes and light +are small, then the antennae are large and feathery, so that the +deficiency in the sense of sight is made up for by an unusual +development in the organs of touch. + +But it is none the less certain that the presence of this light cannot +always be designed to serve this purpose, for many of the animals so +endowed are blind. The phosphorescent centipedes are without eyes, +like all the other members of the genus (_Geophilus_) to which they +belong, and probably the majority of phosphorescent marine forms are +likewise destitute of organs of sight. + +Another suggestion is that the light derived from these marine forms, +and especially from deep-sea Alcyonarians, is what enables the members +of the deep-sea fauna that are possessed of eyes (which are always +enormously enlarged) to see. Such is the suggestion of Dr. Carpenter, +Sir Wyville Thomson, and Mr. Gwyn Jeffries; and it is possible that +this actually is one of the effects of the phosphorescent property. +But if so, it remains to inquire how the forms endowed with it came +to be possessed of a power useful in that way to other forms, but not +to themselves. According to the Darwinian doctrine of development, the +powers that are developed in different organisms by the process of +natural selection are such as are useful to themselves and not to +others, unless incidentally. + +This consideration has led to another suggestion, namely, that the +property of phosphorescence serves as a protection to the forms +possessing it, driving away enemies in one way or another: it may be +by warning them of the fact that they are unpalatable food, as is +believed to be the case with the colors of certain brilliantly-colored +caterpillars; it may be in other ways. In Kirby and Spence one case is +recorded in which the phosphorescence of the common phosphorescent +centipede (_Geophilus electricus_) was actually seen apparently to +serve as a means of defence against an enemy. "Mr. Shepherd," says +that authority, "once noticed a scarabeus running round the +last-mentioned insect when shining, as if wishing, but afraid to +attack it." In the case of the jelly-fishes, it has been pointed out +that their well-known urticating or stinging powers would make them at +least unpleasant, if not dangerous, food for fishes; and that +consequently the luminosity by which so many of them are characterized +at night may serve at once as a warning to predatory fishes and as a +protection to themselves. The experience of the unpleasant properties +of many phosphorescent animals may likewise have taught fishes to +avoid all forms possessing this attribute, even though many of them +might be quite harmless. + +Lastly, it has been suggested that the phosphorescence in the female +glow-worm may be designed to attract the male; and that it will +actually have this effect may readily be taken for granted. +Observation shows that the male glow-worm is very apt to be attracted +by a light. Gilbert White of Selborne mentions that they, attracted by +the light of the candles, came into his parlor. Another observer +states that by the same light he captured as many as forty male +glow-worms in one night. + +[Illustration] + + + + +COMETS + +(FROM MARVELS OF THE HEAVENS.) + +BY CAMILLE FLAMMARION. + + + "Je viens vous annoncer une grande nouvelle: + Nous l'avons, en dormant, madame, échappé belle. + Un monde près de nous a passé tout du long, + Est chu tout au travers de notre tourbillon; + Et s'il eût en chemin rencontré notre terre, + Elle eût été brisée en morceaux comme verre." + MOLIÈRE. + +[Illustration] + +This announcement of Trissontin's to Philaminte, who begins the parody +on the fears caused by the appearance of comets, would not have been a +parody four or five centuries ago. These tailed bodies, which suddenly +come to light up the heavens, were for long regarded with terror, like +so many warning signs of divine wrath. Men have always thought +themselves much more important than they really are in the universal +order; they have had the vanity to pretend that the whole creation was +made for them, whilst in reality the whole creation does not suspect +their existence. The Earth we inhabit is only one of the smallest +worlds; and therefore it can scarcely be for it alone that all the +wonders of the heavens, of which the immense majority remains hidden +from it, were created. In this disposition of man to see in himself +the centre and the end of everything, it was easy indeed to consider +the steps of nature as unfolded in his favor; and if some unusual +phenomenon presented itself, it was considered to be without doubt a +warning from Heaven. If these illusions had had no other result than +the amelioration of the more timorous of the community one would +regret these ages of ignorance; but not only were these fancied +warnings of no use, seeing that once the danger passed, man returned +to his former state; but they also kept up among people imaginary +terrors, and revived the fatal resolutions caused by the fear of the +end of the world. + +When one fancies the world is about to end,--and this has been +believed for more than a thousand years,--no solicitude is felt in the +work of improving this world; and, by the indifference or disdain into +which one falls, periods of famine and general misery are induced +which at certain times have overtaken our community. Why use the +wealth of a world which is going to perish? Why work, be instructed, +or rise in the progress of the sciences or arts? Much better to forget +the world, and absorb one's self in the barren contemplation of an +unknown life. It is thus that ages of ignorance weigh on man, and +thrust him further and further into darkness, while Science makes +known by its influence on the whole community, its great value, and +the magnitude of its aim. + +The history of a comet would be an instructive episode of the great +history of the heavens. In it could be brought together the +description of the progressive movement of human thought, as well as +the astronomical theory of these extraordinary bodies. Let us take, +for example, one of the most memorable and best-known comets, and give +an outline of its successive passages near the Earth. Like the +planetary worlds, Comets belong to the solar system, and are subject +to the rule of the Star King. It is the universal law of gravitation +which guides their path; solar attraction governs them, as it governs +the movement of the planets and the small satellites. The chief point +of difference between them and the planets is, that their orbits are +very elongated; and, instead of being nearly circular, they take the +elliptical form. In consequence of the nature of these orbits, the +same comet may approach very near the Sun, and afterwards travel from +it to immense distances. Thus, the period of the Comet of 1680 has +been estimated at three thousand years. It approaches the Sun, so as +to be nearer to it than our Moon is to us, whilst it recedes to a +distance 853 times greater than the distance of the Earth from the +Sun. On the 17th of December, 1680, it was at its perihelion--that is, +at its greatest proximity to the Sun; it is now continuing its path +beyond the Neptunian orbit. Its velocity varies according to its +distance from the solar body. At its perihelion it travels thousands +of leagues per minute; at its aphelion it does not pass over more than +a few yards. Its proximity to the Sun in its passage near that body +caused Newton to think that it received a heat twenty-eight thousand +times greater than that we experience at the summer solstice; and +that this heat being two thousand times greater than that of red-hot +iron, an iron globe of the same dimensions would be fifty thousand +years entirely losing its heat. Newton added that in the end comets +will approach so near the Sun that they will not be able to escape the +preponderance of its attraction, and that they will fall one after the +other into this brilliant body, thus keeping up the heat which it +perpetually pours out into space. Such is the deplorable end assigned +to comets by the author of the "Principia," an end which makes De la +Brétonne say to Rétif: "An immense comet, already larger than Jupiter, +was again increased in its path by being blended with six other dying +comets. Thus displaced from its ordinary route by these slight shocks, +it did not pursue its true elliptical orbit; so that the unfortunate +thing was precipitated into the devouring centre of the Sun." "It is +said," added he, "that the poor comet, thus burned alive, sent forth +dreadful cries!" + +[Illustration: A COMET] + +It will be interesting, then, in a double point of view, to follow a +comet in its different passages in sight of the Earth. Let us take the +most important in astronomical history--the one whose orbit has been +calculated by Edmund Halley, and which was named after him. It was in +1682 that this comet appeared in its greatest brilliancy, accompanied +with a tail which did not measure less than thirty-two millions of +miles. By the observation of the path which it described in the +heavens, and the time it occupied in describing it, this astronomer +calculated its orbit, and recognized that the comet was the same as +that which was admired in 1531 and 1607, and which ought to have +reappeared in 1759. Never did scientific prediction excite a more +lively interest. The comet returned at the appointed time; and on the +12th of March, 1759, reached its perihelion. Since the year 12 before +the Christian era, it had presented itself twenty-four times to the +Earth. It was principally from the astronomical annals of China that +it was possible to follow it up to this period. + +Its first memorable appearance in the history of France is that of +837, in the reign of Louis le Débonnaire. An anonymous writer of +chronicles of that time, named "The Astronomer," gave the following +details of this appearance, relative to the influence of the comet on +the imperial imagination: + +"During the holy days of the solemnization of Easter, a phenomenon +ever fatal, and of gloomy foreboding, appeared in the heavens. As soon +as the Emperor, who paid attention to these phenomena, received the +first announcement of it, he gave himself no rest until he had called +a certain learned man and myself before him. As soon as I arrived, he +anxiously asked me what I thought of such a sign; I asked time of him, +in order to consider the aspects of the stars, and to discover the +truth by their means, promising to acquaint him on the morrow; but the +Emperor, persuaded that I wished to gain time, which was true, in +order not to be obliged to announce anything fatal to him, said to me: +'Go on the terrace of the palace and return at once to tell me what +you have seen, for I did not see this star last evening, and you did +not point it out to me; but I know that it is a comet; tell me what +you think it announces to me.' Then scarcely allowing me time to say +a word, he added: 'There is still another thing you keep back; it is +that a change of reign and the death of a prince are announced by this +sign.' And as I advanced the testimony of the prophet, who said: 'Fear +not the signs of the heavens as the nations fear them,' the prince +with his grand nature, and the wisdom which never forsook him, said, +'We must not only fear Him who has created both us and this star. But +as this phenomenon may refer to us, let us acknowledge it as a warning +from Heaven." + +Louis le Débonnaire gave himself and his court to fasting and prayer, +and built churches and monasteries. He died three years later, in 840, +and historians have profited by this slight coincidence to prove that +the appearance of the comet was a harbinger of death. The historian, +Raoul Glader, added later: "These phenomena of the universe are never +presented to man without surely announcing some wonderful and terrible +event." + +Halley's comet again appeared in April, 1066, at the moment when +William the Conqueror invaded England. It was pretended that it had +the greatest influence on the fate of the battle of Hastings, which +delivered over the country to the Normans. + +A contemporary poet, alluding probably to the English diadem with +which William was crowned, had proclaimed in one place, "that the +comet had been more favorable to William than nature had been to +Caesar; the latter had no hair, but William had received some from the +comet." A monk of Malmesbury apostrophized the comet in these terms: +"Here thou art again, thou cause of the tears of many mothers! It is +long since I have seen thee, but I see thee now, more terrible than +ever; thou threatenest my country with complete ruin!" + +In 1455, the same comet made a more memorable appearance still. The +Turks and Christians were at war, the West and the East seemed armed +from head to foot--on the point of annihilating each other. The +crusade undertaken by Pope Calixtus III. against the invading +Saracens, was waged with redoubled ardor on the sudden appearance of +the star with the flaming tail. Mahomet II. took Constantinople by +storm, and raised the siege of Belgrade. But the Pope having put aside +both the curse of the comet, and the abominable designs of the +Mussulmans, the Christians gained the battle, and vanquished their +enemies in a bloody fight. The _Angelus_ to the sound of bells dates +from these ordinances of Calixtus III. referring to the comet. + +In his poem on astronomy, Daru, of the French Academy, describes this +episode in eloquent terms: + + "Un autre Mahomet a-t-il d'un bras puissant + Aux murs de Constantine arboré le croissant: + Le Danube étonné se trouble au bruit des armes, + La Grèce est dans les fers, l'Europe est en alarmes; + Et pour comble d'horreur, l'astre au visage ardent + De ses ailes de feu va couvrir l'Occident. + Au pied de ses autels, qu'il ne saurait défendre, + Calixte, l'oeil en pleurs, le front convert de cendre, + Conjure la comète, objet de tant d'effroi: + Regarde vers les cieux, pontife, et lève-toi! + L'astre poursuit sa course, et le fer d'Huniade + Arrête le vainqueur, qui tombe sous Belgrade. + Dans les cieux cependant le globe suspendu, + Par la loi générale à jamais retenu, + Ignore les terreurs, l'existence de Rome, + Et la Terre peut-être, et jusqu'au nom de l'homme, + De l'homme, être crédule, atome ambitieux, + Qui tremble sous un prêtre et qui lit dans les cieux." + +This ancient comet witnessed many revolutions in human history, at +each of its appearances, even in its later ones, in 1682, 1759, 1835; +it was also presented to the Earth under the most diverse aspects, +passing through a great variety of forms, from the appearance of a +curved sabre, as in 1456, to that of a misty head, as in its last +visit. Moreover, this is not an exception to the general rule, for +these mysterious stars have had the gift of exercising a power on the +imagination which plunged it in ecstasy or trouble. Swords of fire, +bloody crosses, flaming daggers, spears, dragons, fish, and other +appearances of the same kind, were given to them in the middle ages +and the Renaissance. + +Comets like those of 1577 appear, moreover, to justify by their +strange form the titles with which they are generally greeted. The +most serious writers were not free from this terror. Thus, in a +chapter on celestial monsters, the celebrated surgeon, Ambroise Paré, +described the comet of 1528 under the most vivid and frightful colors: +"This comet was so horrible and dreadful that it engendered such great +terror to the people, that they died, some with fear, others with +illness. It appeared to be of immense length, and of blood color; at +its head was seen the figure of a curved arm, holding a large sword in +the hand as if it wished to strike. At the point of the sword there +were three stars, and on either side was seen a great number of +hatchets, knives, and swords covered with blood, amongst which were +numerous hideous human faces, with bristling beards and hair." + +The imagination has good eyes when it exerts itself. The great and +strange variety of cometary aspects is described with exactitude by +Father Souciet in his Latin poem on comets. "Most of them," says he, +"shine with fires interlaced like thick hair, and from this they have +taken the name of comets. One draws after it the twisted folds of a +long tail; another appears to have a white and bushy beard; this one +throws a glimmer similar to that of a lamp burning during the night; +that one, O Titan! represents thy resplendent face; and this other, O +Phoebe! the form of thy nascent horns. There are some which bristle +with twisted serpents. Shall I speak of those armies which have +sometimes appeared in the air? of those clouds which follow as it were +along a circle, or which resemble the head of Medusa? Have there not +often been seen figures of men or savage animals? + +"Often, in the gloom of night, lighted up by these sad fires, the +horrible sound of arms is heard, the clashing of swords which meet in +the clouds, the ether furiously resounding with fearful din which +crush the people with terror. All comets have a melancholy light, but +they have not all the same color. Some have a leaden color; others +that of flame or brass. The fires of some have the redness of blood; +others resemble the brightness of silver. Some again are azure; others +have the dark and pale color of iron. These differences come from the +diversity of the vapors which surround them, or from the different +manner in which they receive the Sun's rays. Do you not see in our +fires, that various kinds of wood produce different colors? Pines and +firs give a flame mixed with thick smoke, and throw out little light. +That which rises from sulphur and thick bitumen is bluish. Lighted +straw gives out sparks of a reddish color. The large olive, laurel, +ash of Parnassus, etc., trees which always retain their sap, throw a +whitish light similar to that of a lamp. Thus, comets whose fires are +formed of different materials, each take and preserve a color which is +peculiar to them." + +Instead of being a cause of fear and terror, the variety and +variability of the aspect of comets ought rather to indicate to us the +harmlessness of their nature. + +[Illustration] + + + + +THE TOTAL SOLAR ECLIPSE OF 1883 + +_AN ASTRONOMERS VOYAGE TO FAIRY-LAND._ + +(FROM THE ATLANTIC MONTHLY, MAY, 1890.) + +BY PROF. E.S. HOLDEN. + + +[Illustration] + +In 1883 calculations showed that a solar eclipse of unusually long +duration (5 minutes, 20 seconds) would occur in the South Pacific +Ocean. The track of the eclipse lay south of the equator, but north of +Tahiti. There were in fact only two dots of coral islands on the +charts in the line of totality, Caroline Island, and one hundred and +fifty miles west Flint Island (longitude 150 west, latitude 10 south). +Almost nothing was known of either of these minute points. The station +of the party under my charge (sent out by the United States government +under the direction of the National Academy of Sciences) was to be +Caroline Islands. + +Every inch of that island (seven miles long, a mile or so broad) is +familiar now; but it is almost ludicrous to recollect with what +anxiety we pored over the hydrographic charts and sailing instructions +of the various nations, to find some information, however scanty, +about the spot which was to be our home for nearly a month. All that +was known was that this island had formerly been occupied as a guano +station. There was a landing _then_. + +After the _personnel_ of the party had been decided on, there were the +preparations for its subsistence to be looked out for. How to feed +seventeen men for twenty-one days? Fortunately the provisions that we +took, and the fresh fish caught for us by the natives, just sufficed +to carry us through with comfort and with health. + +In March of 1883 we sailed from New York, and about the same time a +French expedition left Europe bound for the same spot. From New York +to Panama, from Panama to Lima, were our first steps. Here we joined +the United States steamship Hartford, Admiral Farragut's flagship, and +the next day set sail for our destined port,--if a coral reef +surrounded by a raging surf can be called a port. About the same time +a party of French observers under Monsieur Janssen, of the Paris +Academy of Sciences, left Panama in the _Eclaireur_. + +[Illustration: BIRD'S EYE VIEW OF THE CAROLINE ISLANDS.] + +It was an ocean race of four thousand miles due west. The station +Caroline Islands was supposed to be more desirable than Flint Island. +Admiral Wilkes's expedition had lain off the latter several days +without being able to land on account of the tremendous surf, so that +it was eminently desirable to "beat the Frenchman," as the sailors put +it. With this end in view our party had secured (through a member of +the National Academy in Washington) the verbal promise of the proper +official of the Navy Department that the Hartford's orders should read +"to burn coal as necessary." The last obstacle to success was thus +removed. We were all prepared, and now the ship would take us speedily +to our station. + +Imagine our feelings the next day after leaving Callao, when the +commanding officer of the Hartford opened his sealed orders. They read +(dated Washington, in February), "To arrive at Caroline Islands (in +April) with full coal-bunkers!" + +Officialism could go no further. Here was an expedition sent on a +slow-sailing ship directly through the regions of calms for four +thousand miles. It was of no possible use to send the expedition at +all unless it arrived in time. And here were our orders "to arrive +with full coal-bunkers." + +Fortunately we had unheard-of good-luck. The trade-wind blew for us as +it did for the Ancient Mariner, and we sped along the parallel of 12° +south at the rate of one hundred and fifty miles a day under sail, +while the _Eclaireur_ was steaming for thirty days a little nearer the +equator in a dead calm. We arrived off the island just in time, with +not a day to spare. It was a narrow escape, and a warning to all of us +never to sail again under sealed orders unless we knew what was under +the seal. + +Here we were, then, lying off the island and scanning its sparse crown +of cocoanut palms, looking for a French flag among their wavy tufts. +There was none in sight. We were the winners in the long race. +Directly a whale-boat was lowered, and rowed around the white fringe +of tremendous surf that broke ceaselessly against the vertical wall of +coral rock. There was just one narrow place where the waves rolled +into a sort of cleft and did not break. Here was the "landing," then. + +Landing was an acrobatic feat. In you went on the crest of a wave, +pointing for the place where the blue seas did not break into white. +An instant after, you were in the quiet water inside of the surf. Jump +out everybody and hold the boat! Then it was pick up the various +instruments, and carry them for a quarter of a mile to high-water mark +and beyond, over the sharp points of the reef. + +In one night we were fairly settled; in another the Hartford had +sailed away, leaving us in our fairy paradise, where the corals and +the fish were of all the brilliant hues of the rainbow, and where the +whiteness of the sand, the emerald of the lagoon, and the turquoise of +the ocean made a picture of color and form never to be forgotten. + +But where are the Frenchmen? The next morning there is the _Eclaireur_ +lying a mile or so out, and there is a boat with the bo'sun--_maître +d'équipage_--pulling towards the surf. I wade out to the brink. He +halloes: + +"Where is the landing, then?" + +"_Mais ici_"--Right here,--I say. + +"Yes, that's all very well for _persons_, but where do you land _les +bagages_?" + +"_Mais ici_" I say again, and he says, "_Diable!_" + +But all the same he lands both persons and baggage in a neat, +sailor-like way. In a couple of days our two parties of fifty persons +had taken possession of this fairy isle. Observatories go up, +telescopes, spectroscopes, photographic cameras are pointed and +adjusted. The eventful day arrives. Everything is successful. Then +comes the Hartford and takes us away, and a few days later comes the +_Eclaireur_, and the Frenchmen are gone. The little island is left +there, abandoned to the five natives who tend the sickly plantation of +cocoa-palms, and live from year to year with no incident but the +annual visit of "the blig" (Kanaka for brig), which brings their store +of ship biscuit and molasses. + +[Illustration: "OBSERVATORIES GO UP."] + +Think of their stupendous experience! For years and years they have +lived like that in the marvellous, continuous charm of the silent +island. The "blig" had come and gone away this year, and there will +be no more disturbance and discord for a twelve-month longer. + + "Surely, surely, slumber is more sweet than toil, the shore + Than labor in the deep mid-ocean, wind, and wave, and oar, + Then rest ye, brother mariners, we will not wander more!" + +Not so! for here comes a great warship out of the East under a press +of canvas. What event is this? See! she clews up her light sails and +fires an eleven-inch gun! One of those guns of Mobile Bay. Then swarms +out the starboard watch, one hundred and sixty strong, and a fleet of +boats brings ashore these pale astronomers with those useless tubes +that they point at the sky every night. But there are useful things +too; cooking-stoves, and lumber, and bricks. + +What is all this? No sooner are these established than comes another +ship and fires its gun! and another set of hardy sailormen pours out, +and here is another party of madmen with tubes,--yes, and with +cooking-stoves and lumber, too. Then comes the crowning, stupendous, +and unspeakable event. The whole sun is hidden and the heavens are +lighted up with pearly streamers! In the name of all the Polynesian +gods, what is the meaning of all this? + +And then in a few days all these are gone. All the madmen. They have +taken away the useless tubes, but they have left their houses +standing. Their splendid, priceless, precious cook-stoves are here. +See! here is a frying-pan! here are empty tin cans! and a keg of +nails! They must have forgotten all this, madmen as they are! + +And the little island sinks back to its quiet and its calm. The lagoon +lies placid like a mirror. The slow sea breaks eternally on the outer +reef. The white clouds sail over day by day. The seabirds come back to +their haunts,--the fierce man-of-war birds, the gentle, soft-eyed +tern. But we, whose island home was thus invaded--are we the same? Was +this a dream? Will it happen again next year? every year? What indeed +was it that happened,--or in fact, did it happen at all? Is it not a +dream, indeed? + +If we left those peaceful Kanakas to their dream, we Americans have +brought ours away with us. Who will forget it? Which of us does not +wish to be in that peaceful fairyland once more? That is the personal +longing. But we have all come back, each one with his note-books full; +and in a few weeks the stimulus of accustomed habit has taken +possession of us again. Right and wrong are again determined by +"municipal sanctions." We have become useful citizens once more. +Perhaps it is just as well. We should have been poor poets, and we do +not forget. So ends the astronomer's voyage to fairyland. + +[Illustration] + + + + +HALOS--PARHELIA--THE SPECTRE OF THE BROCKEN, ETC + +(FROM THE ATMOSPHERE.) + +BY CAMILLE FLAMMARION. + + +[Illustration] + +Treatises on meteorology have not, up to the present day, classified +with sufficient regularity the divers optical phenomena of the air. +Some of these phenomena have, however, been seen but rarely, and have +not been sufficiently studied to admit of their classification. We +have examined the common phenomenon of the rainbow and we have seen +that it is due to the refraction and reflection of light on drops of +water, and that it is seen upon the opposite side of the sky to the +sun in day-time, or the moon at night. We are now about to consider an +order of phenomena which are of rarer occurrence, but which have this +property in common with the rainbow, viz., that they take place also +upon the side of the sky opposite to the sun. These different optical +effects are classed together under the name of _anthelia_ (from +Greek, opposite to, and Greek, the sun). The optical phenomena which +occur on the same side as, or around the sun, such as halos, parhelia, +etc., will be dealt with later on. + +Before coming to the anthelia, properly so called, or to the colored +rings which appear around a shadow, it is as well first to note the +effects produced on the clouds and mists that are facing the sun when +it rises or sets. + +Upon high mountains, the shadow of the mountain is often seen thrown +either upon the surface of the lower mists or upon the neighboring +mountains, and projected opposite to the sun almost horizontally. I +once saw the shadow of the Righi very distinctly traced upon Mount +Pilate, which is situated to the west of the Righi, on the other side +of the Lake of Lucerne. This phenomenon occurs a few minutes after +sunrise, and the triangular form of Righi is delineated in a shape +very easy to recognize. + +The shadow of Mont Blanc is discerned more easily at sunset. MM. +Bravais and Martins, in one of their scientific ascents, noticed it +under specially favorable circumstances, the shadow being thrown upon +the snow-covered mountains, and gradually rising in the atmosphere +until it reached a height of 1°, still remaining quite visible. The +air above the cone of the shadow was tinted with that rosy purple +which is seen, in a fine sunset, coloring the lofty peaks. "Imagine," +says Bravais, "the other mountains also projecting, at the same +moment, their shadows into the atmosphere, the lower parts dark and +slightly greenish, and above each of these shadows the rosy surface, +with the deeper rose of the belt which separates it from them; add to +this the regular contour of the cones of the shadow, principally at +the upper edge, and lastly, the laws of perspective causing all these +lines to converge the one to the other toward the very summit of the +shadow of Mont Blanc; that is to say, to the point of the sky where +the shadows of our own selves were; and even then one will have but a +faint idea of the richness of the meteorological phenomenon displayed +before our eyes for a few instants. It seemed as though an invisible +being was seated upon a throne surrounded by fire, and that angels +with glittering wings were kneeling before him in adoration." + +Among the natural phenomena which now attract our attention, but fail +to excite our surprise, there are some which possess the +characteristics of a supernatural intervention. The names which they +have received still bear witness to the terror which they once +inspired; and even to-day, when science has stripped them of their +marvellous origin, and explained the causes of their production, these +phenomena have retained a part of their primitive importance, and are +welcomed by the _savant_ with as much interest as when they were +attributed to divine agency. Out of a large and very diverse number, I +will first select the _Spectre of the Brocken_. + +The Brocken is the highest mountain in the picturesque Hartz chain, +running through Hanover, being three hundred and thirty feet above the +level of the sea. + +One of the best descriptions of this phenomenon is given by the +traveller Hane, who witnessed it on the 23d of May, 1797. After having +ascended no less than thirty miles to the summit, he had the good +fortune at last to contemplate the object of his curiosity. The sun +rose at about four o'clock, the weather being fine, and the wind +driving off to the west the transparent vapors which had not yet had +time to be condensed into clouds. About a quarter-past four, Hane saw +in this direction a human figure of enormous dimensions. A gust of +wind nearly blowing off his hat at that moment, he raised his hand to +secure it, and the colossal figure imitated his action. Hane, noticing +this, at once made a stooping movement, and this was also reproduced +by the spectre. He then called another person to him, and placing +themselves in the very spot where the apparition was first seen, the +pair kept their eyes fixed on the Achtermannshohe, but saw nothing. +After a short interval, however, two colossal figures appeared, which +repeated the gestures made by them, and then disappeared. + +Some few years ago, in the summer of 1862, a French artist, M. +Stroobant, witnessed and carefully sketched this phenomenon, which is +drawn in full-page illustration, opposite p. 272. He had slept at the +inn of the Brocken, and rising at two in the morning, he repaired to +the plateau upon the summit in the company of a guide. They reached +the highest point just as the first glimmer of the rising sun enabled +them to distinguish clearly objects at a great distance. To use M. +Stroobant's own words, "My guide, who had for some time appeared to be +walking in search of something, suddenly led me to an elevation whence +I had the singular privilege of contemplating for a few instants the +magnificent effect of mirage, which is termed the Spectre of the +Brocken. The appearance is most striking. A thick mist, which seemed +to emerge from the clouds like an immense curtain, suddenly rose to +the west of the mountain, a rainbow was formed, then certain +indistinct shapes were delineated. First, the large tower of the inn +was reproduced upon a gigantic scale; after that we saw our two selves +in a more vague and less exact shape, and these shadows were in each +instance surrounded by the colors of the rainbow, which served as a +frame to this fairy picture. Some tourists who were staying at the inn +had seen the sun rise from their windows, but no one had witnessed the +magnificent spectacle which had taken place on the other side of the +mountain." + +Sometimes these spectres are surrounded by colored concentric arcs. +Since the beginning of the present century, treatises on meteorology +designate, under the name of the _Ulloa circle_, the pale external +arch which surrounds the phenomenon, and this same circle has +sometimes been called the "white rainbow." But it is not formed at the +same angular distance as the rainbow, and, although pale, it often +envelops a series of interior colored arcs. + +[Illustration: "THE SPECTRE OF THE BROCKEN"] + +Ulloa, being in company with six fellow-travellers upon the Pambamarca +at daybreak one morning, observed that the summit of the mountain was +entirely covered with thick clouds, and that the sun, when it rose, +dissipated them, leaving only in their stead light vapors, which it +was almost impossible to distinguish. Suddenly, in the opposite +direction to where the sun was rising, "each of the travellers beheld, +at about seventy feet from where he was standing, his own image +reflected in the air as in a mirror. The image was in the centre of +three rainbows of different colors, and surrounded at a certain +distance by a fourth bow with only one color. The inside color of each +bow was carnation or red, the next shade was violet, the third yellow, +the fourth straw color, the last green. All these bows were +perpendicular to the horizon; they moved in the direction of, and +followed, the image of the person they enveloped as with a glory." The +most remarkable point was that, although the seven spectators were +standing in a group, each person only saw the phenomenon in regard to +his own person, and was disposed to disbelieve that it was repeated in +respect to his companions. The extent of the bows increased +continually and in proportion to the height of the sun; at the same +time their colors faded away, the spectre became paler and more +indistinct, and finally the phenomenon disappeared altogether. At the +first appearance the shape of the bows was oval, but toward the end +they became quite circular. The same apparition was observed in the +polar regions by Scoresby, and described by him. He states that the +phenomenon appears whenever there is mist and at the same time shining +sun. In the polar seas, whenever a rather thick mist rises over the +ocean, an observer, placed on the mast, sees one or several circles +upon the mist. + +[Illustration: THE ULLOA CIRCLE.] + +These circles are concentric, and their common centre is in the +straight line joining the eye of the observer to the sun, and extended +from the sun toward the mist. The number of circles varies from one to +five; they are particularly numerous and well colored when the sun is +very brilliant and the mist thick and low. On July 23, 1821, Scoresby +saw four concentric circles around his head. The colors of the first +and of the second were very well defined; those of the third, only +visible at intervals, were very faint, and the fourth only showed a +slight greenish tint. + +The meteorologist Kaemtz has often observed the same fact in the Alps. +Whenever this shadow was projected upon a cloud, his head appeared +surrounded by a luminous aureola. + +To what action of light is this phenomenon due? Bouguer is of opinion +that it must be attributed to the passage of light through icy +particles. Such, also, is the opinion of De Saussure, Scoresby, and +other meteorologists. + +In regard to the mountains, as we cannot assure ourselves directly of +the fact by entering the clouds, we are reduced to conjecture. The +aerostat traversing the clouds completely, and passing by the very +point where the apparition is seen, affords one an opportunity of +ascertaining the state of the cloud. This observation I have been able +to make, and so to offer an explanation of the phenomenon. + +As the balloon sails on, borne forward by the wind, its shadow travels +either on the ground or on the clouds. This shadow is, as a rule, +black, like all others; but it frequently happens that it appears +alone on the surface of the ground, and thus appears luminous. +Examining this shadow by the aid of a telescope, I have noticed that +it is often composed of a dark nucleus and a penumbra of the shape of +an aureola. This aureola, frequently very large in proportion to the +diameter of the central nucleus, eclipses it to the naked eye, so that +the whole shadow appears like a nebulous circle projected in yellow +upon the green ground of the woods and meadows. I have noticed, too, +that this luminous shadow is generally all the more strongly marked in +proportion to the greater humidity of the surface of the ground. + +Seen upon the clouds, this shadow sometimes presents a curious aspect. +I have often, when the balloon emerged from the clouds into the clear +sky, suddenly perceived, at twenty or thirty yards' distance, a second +balloon distinctly delineated, and apparently of a grayish color, +against the white ground of the clouds. This phenomenon manifests +itself at the moment when the sun re-appears. The smallest details of +the car can be made out clearly, and our gestures are strikingly +reproduced by the shadow. + +[Illustration: THE SHADOW OF THE BALLOON WAS SEEN BY US.] + +On April 15, 1868, at about half-past three in the afternoon, we +emerged from a stratum of clouds, when the shadow of the balloon was +seen by us, surrounded by colored concentric circles, of which the car +formed the centre. It was very plainly visible upon a yellowish white +ground. A first circle of pale blue encompassed this ground and the +car in a kind of ring. Around this ring was a second of a deeper +yellow, then a grayish red zone, and lastly as the exterior +circumference, a fourth circle, violet in hue, and imperceptibly +toning down into the gray tint of the clouds. The slightest details +were clearly discernible--net, robes, and instruments. Every one of +our gestures was instantaneously reproduced by the aerial spectres. +The anthelion remained upon the clouds sufficiently distinct, and for +a sufficiently long time, to permit of my taking a sketch in my +journal and studying the physical condition of the clouds upon which +it was produced. I was able to determine directly the circumstances of +its production. Indeed, as this brilliant phenomenon occurred in the +midst of the very clouds which I was traversing, it was easy for me to +ascertain that these clouds were not formed of frozen particles. The +thermometer marked 2° above zero. The hygrometer marked a maximum of +humidity experienced, namely, seventy-seven at three thousand seven +hundred and seventy feet, and the balloon was then at four thousand +six hundred feet, where the humidity was only seventy-three. It is +therefore certain that this is a phenomenon of the diffraction of +light simply produced by the vesicles of the mist. + +The name of diffraction is given to all the modifications which the +luminous rays undergo when they come in contact with the surface of +bodies. Light, under these circumstances, is subject to a sort of +deviation, at the same time becoming decomposed, whence result those +curious appearances in the shadows of objects which were observed for +the first time by Grimaldi and Newton. + +The most interesting phenomena of diffraction are those presented by +_gratings_, as are technically denominated the systems of linear and +very narrow openings situated parallel to one another and at very +small intervals. A system of this kind may be realized by tracing with +a diamond, for instance, on a pane of glass equidistant lines very +close together. As the light would be able to pass in the interstices +between the strokes, whereas it would be stopped in the points +corresponding to those where the glass was not smooth, there is, in +reality, an effect produced as if there were a series of openings very +near to each other. A hundred strokes, about 1/25th of an inch in +length, may thus be drawn without difficulty. The light is then +decomposed in spectra, each overlapping the other. It is a phenomenon +of this kind which is seen when we look into the light with the eye +half closed; the eyelashes in this case, acting as a net-work or +grating. These net-works may also be produced by reflection, and it is +to this circumstance that are due the brilliant colors observed when a +pencil of luminous rays is reflected on a metallic surface regularly +striated. + +To the phenomena of gratings must be attributed, too, the colors, +often so brilliant, to be seen in mother-of-pearl. This substance is +of a laminated structure; so much so, that in carving it the different +folds are often cut in such a way as to form a regular net-work upon +the surface. It is, again, to a phenomenon of this sort that are due +the rainbow hues seen in the feathers of certain birds, and sometimes +in spiders' webs. The latter, although very fine, are not simple, for +they are composed of a large number of pieces joined together by a +viscous substance, and thus constitute a kind of net-work. + +If the sun is near the horizon, and the shadow of the observer falls +upon the grass, upon a field of corn, or other surface covered with +dew, there is visible an aureola, the light of which is especially +bright about the head, but which diminishes from below the middle of +the body. This light is due to the reflection of light by the moist +stubble and the drops of dew. It is brighter about the head, because +the blades that are near where the shadow of the head falls expose to +it all that part of them which is lighted up, whereas those farther +off expose not only the part which is lighted up, but other parts +which are not, and this diminishes the brightness in proportion as +their distance from the head increases. The phenomenon is seen +whenever there is simultaneously mist and sun. This fact is easily +verified upon a mountain. As soon as the shadow of a mountaineer is +projected upon a mist, his head gives rise to a shadow surrounded by a +luminous aureola. + +[Illustration: FOG-BOW SEEN FROM THE MATTERHORN.] + +_The Illustrated London News_ of July 8, 1871, illustrates one of +these apparitions, "The Fog-Bow, seen from the Matterhorn," observed +by E. Whymper in this celebrated region of the Alps. The observation +was taken just after the catastrophe of July 14, 1865; and by a +curious coincidence, two immense white aerial crosses projected into +the interior of the external arc. These two crosses were no doubt +formed by the intersection of circles, the remaining parts of which +were invisible. The apparition was of a grand and solemn character, +further increased by the silence of the fathomless abyss into which +the four ill-fated tourists had just been precipitated. + +[Illustration] + +Other optical appearances of an analogous kind are manifested under +different conditions. Thus, for instance, if any one, turning his back +to the sun, looks into water, he will perceive the shadow of his head, +but always very much deformed. At the same time he will see starting +from this very shadow what seem to be luminous bodies, which dart +their rays in all directions with inconceivable rapidity, and to a +great distance. These luminous appearances--these aureola rays--have, +in addition to the darting movement, a rapid rotary movement around +the head. + +[Illustration] + + + + +THE PLANET VENUS + +BY AGNES M. CLERKE. + + + + +I. + +HESPERUS AND PHOSPHOR. + + +[Illustration] + +The radiant planet that hangs on the skirts of dusk and dawn + + "like a jewel in an Ethiop's ear," + +has been known and sung by poets in all ages. Its supremacy over the +remainder of the starry host is recognized in the name given it by the +Arabs, those nomad watchers of the skies, for while they term the moon +"El Azhar," "the Brighter One," and the sun and moon together "El +Azharan," "the Brighter Pair," they call Venus "Ez Zahra," the bright +or shining one _par excellence_, in which sense the same word is used +to describe a flower. This "Flower of Night" is supposed to be no +other than the white rose into which Adonis was changed by Venus in +the fable which is the basis of all early Asiatic mythology. The +morning and evening star is thus the celestial symbol of that union +between earth and heaven in the vivifying processes of nature, +typified in the love of the goddess for a mortal. + +The ancient Greeks, on the other hand, not unnaturally took the star, +which they saw alternately emerging from the effulgence of the rising +and setting sun, in the east and in the west, for two distinct bodies, +and named it differently according to the time of its appearance. The +evening star they called Hesperus, and from its place on the western +horizon, fabled an earthly hero of that name, the son of Atlas, who +from the slopes of that mountain on the verge of the known world used +to observe the stars until eventually carried off by a mighty wind, +and so translated to the skies. These divine honors were earned by his +piety, wisdom, and justice as a ruler of men, and his name long shed a +shimmering glory over those Hesperidean regions of the earth, where +the real and unreal touched hands in the mystical twilight of the +unknown. + +But the morning star shone with a different significance as the herald +of the day, the torchbearer who lights the way for radiant Aurora on +her triumphal progress through the skies. Hence he was called +Eosphorus, or Phosphorus, the bearer of the dawn, translated into +Latin as Lucifer, the Light-bearer. The son of Eos, or Aurora, and the +Titan Astraeus, he was of the same parentage as the other multitude of +the starry host, to whom a similar origin was ascribed, and from whom +in Greek mythology he was evidently believed to differ only in the +superior order of his brightness. Homer, who mentions the planet in +the following passage: + + "But when the star of Lucifer appeared, + The harbinger of light, whom following close, + Spreads o'er the sea the saffron-robed morn." + + (LORD DERBY'S "Iliad.") + +recognizes no distinction between those celestial nomads, the planets, +"wandering stars," as the Arabs call them, which visibly change their +position relatively to the other stars, and the latter, whose places +on the sphere are apparently fixed and immutable. In this he and his +compatriots were far behind the ancient Egyptians, who probably +derived their knowledge from still earlier speculators in Asia, for +they not only observed the movements of some at least of the planets, +but believed that Mercury and Venus revolved as satellites round the +sun, which in its turn circled round our lesser world. Pythagoras is +said to have been the first to identify Hesperus with Phosphor, as the + + "Silver planet both of eve and morn," + +and by Plato the same fact is recognized. The other planets, all of +which had, according to him, been originally named in Egypt and Syria, +have each its descriptive title in his nomenclature. Thus the +innermost, "the Star of Mercury," is called Stilbon, "the Sparkler," +Mars, Pyroeis, "the Fiery One," while Jupiter, the planet of the +slowest course but one, is designated as Phaeton, and Saturn, the +tardiest of all, Phaenon. These names were in later times abandoned in +favor of those of the divinities to whom they were respectively +dedicated, unalterably associated now with the days of the week, over +which they have been selected to preside. + +The Copernican theory, which once and forever "brushed the cobwebs out +of the sky," by clearing away the mists of pre-existing error, first +completely explained the varying positions of the Shepherd's star, +irradiating the first or last watch of night, according to her +alternate function as the follower or precursor of the sun. As she +travels on a path nearer to him by more than twenty-five and a half +million miles than that of the earth, she is seen by us on each side +of him in turn after passing behind or in front of him. The points at +which her orbit expands most widely to our eyes--an effect of course +entirely due to perspective, as her distance from the sun is not then +actually increased--are called her eastern and western elongations; +that at which she passes by the sun on the hither side her inferior, +and on the farther side her superior conjunction. At both conjunctions +she is lost to our view, since she accompanies the sun so closely as +to be lost in his beams, rising and setting at the same time, and +travelling with him in his path through the heavens during the day. +When at inferior conjunction, or between us and the sun, she turns her +dark hemisphere to us like the new moon, and would consequently be +invisible in any case, but when in the opposite position, shows us her +illuminated face, and is literally a day star, invisible only because +effaced by the solar splendor. It is as she gradually separates from +him, after leaving this latter position, circling over that half of +her orbit which lies to the east of him, that she begins to come into +view as an evening star, following him at a greater and greater +distance, and consequently setting later, until she attains her +greatest eastern elongation, divided from the sun about 45° of his +visible circuit through the heavens, and consequently remaining above +the horizon for some four hours after him. From this point she again +appears to draw nearer to him until she passes on his hither side in +inferior conjunction, from which she emerges on the opposite side to +the westward, and begins to shine as a morning star, preceding him on +his track, at a gradually increasing distance, until attaining her +greatest westward elongation, and finally completing her cycle by +returning to superior conjunction once more in a period of about five +hundred and eighty-four days. + +Venus is thus Hesperus or Vesper, the evening star, when following the +sun as she passes from beyond him in superior conjunction to inferior +conjunction where she is nearest to the earth. As she again leaves him +behind in her course from this point to the opposite one of superior +conjunction, she appears in her second aspect as Phosphorus or +Lucifer, "the sun of morning," and herald of the day, shining as + + "The fair star + That gems the glittering coronet of morn." + + + + +II. + +THE PHASES OF VENUS. + + +But the changes in the aspect of Venus due to her varying positions in +her orbit are not confined to those which cause her to oscillate with +a pendulum movement eastward and westward from the sun. The discovery +that she undergoes phases exactly like those of the moon, followed +that of the existence of Jupiter's satellites as the second great +result achieved by the use of the telescope in the hands of Galileo. +The fact that the planets were intrinsically dark bodies revolving +round the sun, and reflecting its light, as he and Copernicus had +maintained, thus received a further ocular demonstration. The +Florentine astronomer describes in a letter to a friend how the +planet, after emerging from superior conjunction as a morning star, +gradually loses her rotundity on the side remote from the luminary, +changing first to a half sphere and then to a waning crescent; until, +after passing through the stage of absolute extinction when +intervening between us and the sun, she re-appears as a morning star, +and undergoes the same series of transformations in inverse order. The +revelation was indeed so novel and unexpected, that when the slight +deformation of the planet's shape was first detected by him, he did +not venture to announce it in plain terms but veiled it, according to +the prevailing fashion of the time, under a Latin anagram. His +celebrated sentence-- + + "Haec immatura a me jam frustra leguntur." + +("Those incomplete observations are as yet read by me in vain.") + +forms, by transposing the letters, the more definite statement, + + "Cynthiæ figuras æmulatur Mater Amorum." + +("The mother of the loves imitates the aspects of Diana.") + +that is to say, Venus vies with the phases of the moon. The discovery +was an important one from its bearing on popular superstition ascribing +to the planets special influences on human affairs, for since they were +thus shown to transmit to us only borrowed light, belief in their +beneficent or malefic powers over man's destinies received a rude shock. + +[Illustration: THE PHASES OP VENUS.] + +Galileo's announcement, published in September, 1610, when only a +slight flattening of the planet's disk was visible, received absolute +confirmation in the ensuing months, as she completed her full +half-circle of change on February 24th of the following year, and +consequently exhibited herself to him in all her varying aspects. It +was the first time they had been looked upon by a human eye, since its +unaided powers do not enable it to discern them, although one +exception to this rule is said to have existed. This was the case of +the Swiss mathematician Gauss, who, when a child, on being shown the +crescent star through the telescope, exclaimed to his mother that it +"was turned wrong"; the inference being that he recognized the +reversal of the image in the field of the glass. If it were indeed so, +he deserves to rank with the Siberian savage, who described the +eclipses, or Jupiter's satellites; or the shoemaker of Breslau, who +could see and declare the positions of those minute orbs. + +The phases exhibited to us by Venus are due to her moving in an orbit +within that of the earth, at one side of which she is between us and +the sun, while at the other this position is exactly reversed. We may +compare her to a performer in a great celestial circus, lit by a +central chandelier, and ourselves to spectators in an external ring, +from which we see her at one time facing us with the light full on +her, at the opposite point in complete shadow, and at the intermediate +ones in varying degrees of illumination according to our changing +views of her. The same illustration may serve to show why Venus is +brightest, not when full, since she is then beyond the sun, and at the +farthest possible point from us, but when she approaches us at +inferior conjunction, more nearly by over one hundred and thirty +million miles, and still shows us a crescent of her illuminated +surface, before passing into the last phase of total obscuration. When +actually nearest to us she is absolutely invisible, being then, like +the new moon, between us and the sun. Her varying degrees of +brilliancy, even when in the same phase, are thus accounted for by her +alternate retreat from and advance towards us as she circles round the +sun. Completing, as she does, her revolution in about seven months and +a half, she would of course go through the whole series of her +metamorphoses in that time, were the earth, from which we observe +them, a fixed point. Their protraction instead, over a term of five +hundred and eighty-four days, or more than nineteen months, is due to +the simultaneous motion of the earth in the same direction, over her +larger orbit in a longer period, causing the same relative position of +the sister planet to recur only as often as she overtakes her in her +career. Thus the hour and minute hands of a watch, moving at different +rates of speed after meeting on the dial plate at twelve o'clock, will +not again come together until five minutes past one, when the swifter +paced of the two will have completed a revolution and a twelfth. But +were we to retard the motion of the latter, reducing it to only twice +that of its companion, they would always meet at the figure twelve, as +it would exactly complete two circuits while the hour hand was +performing one. Venus thus overtakes and passes the earth once in five +hundred and eighty-four days, or nearly two and a half of her own +years, constituting what is called her synodic period of apparent +revolution as seen from this globe. She thus presents to us all the +phases undergone by our own satellite during a lunar month, passing +from new to full, and _vice versa_, through the various intervening +gradations of form. + +The phases of Venus are amongst the most beautiful subjects for +observation in a moderate telescope, as her silver bow, gradually +brightening in the evening dusk, or fading in the dawn, + + "On a bed of daffodil sky," + +is, after the two greater luminaries that rule the day and night, the +most brilliant object in the heavens. + + + + +III. + +THE SILVER CROWN. + + +The parallel between Venus and + + "That orbed maiden with fire laden, + Whom mortals call the moon," + +is carried a stage further. Most of us are familiar with the spectacle +in which the Ancient Egyptians saw symbolized Horus on the lap of +Isis, but which we more prosaically term "the old moon in the new +moon's arms." The strongly illuminated half circle next the sun is +then seen embracing with its horns a dusky sphere, contrasting with it +as tarnished silver does with the newly burnished metal. The same +phenomenon is occasionally, though very rarely, exhibited by Venus, +while close to the sun at inferior injunction, when the shadowy form +of the full orb is seen to shine dimly within her crescent with what +is termed "the ashen light." More wonderful still, this "glimmering +sphere" is then crowned, as with a silver halo, by a thin luminous +arch, forming a secondary sickle facing the one nearest the sun, and +doubtless due to the refraction of his rays round the globe of the +planet, through the upper regions of her twilight atmosphere. This +spectacle was first observed by the Jesuit Ricciolo, an opponent of +the Copernican theory, on January 9th, 1643. He describes the planet +as ruddy near the sun, yellowish in the middle, and of greenish blue +on the side remote from the sun; while he also noted the bow of light +limiting the dark hemisphere. Scarcely daring to trust his own +eyesight, he ascribed these appearances, although he recorded them, to +illusory reflection in the telescope. + +[Illustration: VENUS AT HER GREATEST BRILLIANCY.] + +They were again seen, however, by Derham about 1715, and six years +later by Kirch, in Berlin, who has the following entry in his diary +for Saturday, June 29, 1721:--"I found Venus in a region where the sky +was not very clear. The planet was narrow, and I seemed to see its +dark side, though this is almost incredible. The diameter of Venus was +65", and its sickle seemed to tremble in the atmospheric vapors." +Again, on March 8th, 1726, he records a similar observation. "We +observed Venus with the twenty-six foot telescope. I perceived her +dark side, and its edge seemed to describe a smaller circle than that +of the light side, as is the case of the moon." This effect is due to +irradiation, that is to say, to the glare from a bright surface, +giving a deceptive enlargement to its apparent area. He again saw the +dark side of the planet in October, 1759, as did Harding at Göttingen, +with Herschel's ten-foot reflector, on January 24th, 1806. This latter +observer saw it on this occasion stand out against the background of +the sky as of a pale ashen green, while on February 28th following, it +seemed to him of a pale reddish gray, like the color of the eclipsed +moon. + +That the latter body should send to us from her nocturnal shadows +sufficient light to be visible is easily explicable, since she is then +flooded with earth-light reflected on her from a surface thirteen and +one-half times greater than her own, and probably casting on her an +illumination transcending our full moonlight in the same proportion. +But the secondary light of Venus admits of no such explanation, since +earth-light on her surface, diminished by 1/12000th part compared to +what it is on that of the moon, would be quite insufficient to render +her visible to our eyes. The phenomenon was therefore adduced as an +argument for the habitability of the planets by Gruithuisen, of the +Munich Observatory, who, writing early in this century, suggested that +the ashen light of Venus might be due to general illuminations in +celebration by her inhabitants of some periodically recurring +festivity, The materials for a flare-up on so grand a scale would, he +thought, exist in abundance, as he conjectured the vegetation of our +planetary neighbor to be more luxuriant than that of our Brazilian +forests. The phosphorescence of the Aphroditean oceans, warm and +teeming with life, as they are held to be by Zollner, was advanced as +an explanatory hypothesis, with scarcely more plausibility, by +Professor Safarik, while others have resorted to the supposition of +atmospheric or electrical luminosity producing on a large scale some +such display as that of the aurora borealis. + +Professor Vogel, of Berlin, who himself saw part of the night-side of +Venus, in its semi-obscurity in November, 1871, ascribed its +visibility to a twilight effect caused by a very extensive atmosphere. +The light thus transmitted to us by aerial diffusion and giving the +ashen light, is reflected sunlight, while that sent by the luminous +arc on its edge is direct sunlight, refracted, or bent round to us, +from behind the planet. The silver selvedge of the dawn edging the +dark limb may consequently be the brightest part of the broken nimbus +that then seems to surround her. + +A similar appearance is observed during transits of Venus, when she +passes directly between us and the actual solar disk. A silver thread +is then seen encircling that side of the planet which has not yet +entered on the face of the sun or "a shadowy nebulous ring," as it was +described by Mr. Macdonnell at Eden, surrounds the whole planetary +disk when two-thirds of it have passed the solar edge. As it moves off +it, the same aureole again becomes visible, testifying to the +existence of an atmosphere of considerable extent exterior to the +sharply outlined surface ordinarily visible. The shimmering haze of +reflected sunlight which perpetually enfolds her is only made apparent +to us under exceptional circumstances which cut off some portion of +her more immediate light, just as we see the motes in the air +illuminated by a candle if we hide the actual flame from our eyes. The +perennial twilight which seems to reign over the nocturnal hemisphere +of Venus may compensate, perhaps, for the want of a satellite to +modify its darkness. + +The great prolongation at other times of the horns of her crescent, so +as to embrace almost her entire circumference with a tenuous ring of +light, is doubtless due to the same cause, as their visibility should +otherwise be limited to a half segment of a circle. The regions thus +shining to us are obviously those on which the sun has not yet set, +his appearance above the horizon being prolonged, as in our own case, +by refraction, though to a much larger extent. The magnitude of the +sun's disk as seen from Venus, a third larger than it appears to us, +is also adducted by Mr. Proctor in his posthumous work, "The Old and +the New Astronomy," edited and completed by Mr. A.C. Ranyard, as an +element in extending the illumination of Venus to more than a +hemisphere of her surface. As his diameter there is 44-1/4°, a zone +of more than 22° wide outside the sunward hemisphere is he thinks +illuminated by direct though partial sunlight, the orb being +throughout this tract still partially above the horizon. + +[Illustration: GEOGRAPHICAL ASPECT OF VENUS.] + + + + +[Illustration] + + +THE STARS + +(FROM STARLAND.) + +BY SIR ROBERT S. BALL. + + +[Illustration] + +The group of bodies which cluster around our sun forms a little +island, so to speak, in the extent of infinite space. We may +illustrate this by a map in which we shall endeavor to show the stars +placed at their proper relative distances. We first open the compasses +one inch, and thus draw a little circle to represent the path of the +earth. We are not going to put in all the planets. We take Neptune, +the outermost, at once. To draw its path I open the compasses to +thirty inches, and draw a circle with that radius. That will do for +our solar system, though the comets no doubt will roam beyond these +limits. To complete our map we ought of course to put in some stars. +There are a hundred million to choose from, and we shall begin with +the brightest. It is often called the Dog Star, but astronomers know +it better as Sirius. Let us see where it is to be placed on our map. +Sirius is beyond Neptune, so it must be outside somewhere. Indeed, it +is a good deal further off than Neptune; so I try at the edge of the +drawing-board; I have got a method of making a little calculation that +I do not intend to trouble you with, but I can assure you that the +results it leads me to are quite correct; they show me that this board +is not big enough. But could a board which was big enough fit into +this lecture theatre? Here, again, I make my little calculations, and +I find that there would not be room for a board sufficiently great; in +fact, if I put the sun here at one end, with its planets around it? +Sirius would be too near on the same scale if it were at the further +corner. The board would have to go out through the wall of the +theatre, out through London. Indeed, big as London is, it would not be +large enough to contain the drawing-board that I should require. It +would have to stretch about twenty miles from where we are now +assembled. We may therefore dismiss any hope of making a practical map +of our system on this scale if Sirius is to have its proper place. Let +us, then, take some other star. We shall naturally try with the +nearest of all. It is one that we do not know in this part of the +world, but those that live in the southern hemisphere are well +acquainted with it. The name of this star is Alpha Centauri. Even for +this star we should require a drawing three or four miles long if the +distance from the earth to the sun is to be taken as one inch. You see +what an isolated position our sun and his planets occupy. The members +of the family are all close together, and the nearest neighbors are +situated at enormous distances. There is a good reason for this +separation. The stars are very pretty and perfectly harmless to us +where they are at present situated. They might be very troublesome +neighbors if they were very much closer to our system. It is therefore +well they are so far off; they would be constantly making disturbances +in the sun's family if they were near at hand. Sometimes they would be +dragging us into unpleasantly great heat by bringing us too close to +the sun, or producing a coolness by pulling us away from the sun, +which would be quite as disagreeable. + + +The Stars are Suns. + +We are about to discuss one of the grandest truths in the whole of +nature. We have had occasion to see that this sun of ours is a +magnificent globe immensely larger than the greatest of his planets, +while the greatest of these planets is immensely larger than this +earth; but now we are to learn that our sun is, indeed, only a star +not nearly so bright as many of those which shine over our heads every +night. We are comparatively close to the sun, so that we are able to +enjoy his beautiful light and cheering heat. Each of those other +myriads of stars is a sun, and the splendor of those distant suns is +often far greater than that of our own. We are, however, so enormously +far from them that they appear dwindled down to insignificance. To +judge impartially between our sun or star and such a sun or star as +Sirius we should stand halfway between the two; it is impossible to +make a fair estimate when we find ourselves situated close to one star +and a million times as far from the other. After allowance is made for +the imperfections of our point of view, we are enabled to realize the +majestic truth that the sun is no more than a star, and that the other +stars are no less than suns. This gives us an imposing idea of the +extent and magnificence of the universe in which we are situated. Look +lip at the sky at night--you will see a host of stars; try to think +that every one of them is itself a sun. It may probably be that those +suns have planets circling round them, but it is hopeless for us to +expect to see such planets. Were you standing on one of those stars +and looking towards our system, you would not perceive the sun to be +the brilliant and gorgeous object that we know so well. If you could +see him at all, he would merely seem like a star, not nearly as bright +as many of those you can see at night. Even if you had the biggest of +telescopes to aid your vision, you could never discern from one of +these bodies the planets which surround the sun, no astronomer in the +stars could see Jupiter, even if his sight were a thousand times as +powerful as any sight or telescope that we know. So minute an object +as our earth would, of course, be still more hopelessly beyond the +possibility of vision. + + +The Number of the Stars. + +To count the stars involves a task which lies beyond the power of man +to accomplish. Even without the aid of any telescope, we can see a +great multitude of stars from this part of the world. There are also +many constellations in the southern hemisphere which never appear +above our horizon. If, however, we were to go to the equator, then, by +waiting there for a twelve-month, all the stars in the heavens would +have been successively exposed to view. An astronomer, Houzeau, with +the patience to count them, enumerated about six thousand. This is the +naked-eye estimate of the star-population of the heavens; but if +instead of relying on unaided vision, you get the assistance of a +little telescope, you will be astounded at the enormous multitude of +stars which are disclosed. + +[Illustration: FIG 1. THE GREAT BEAR AND THE POLE.] + +An ordinary opera-glass or binocular is a very useful instrument for +looking at the stars in the heavens. If you employ an instrument of +this sort, you will be amazed to find that the heavens teem with +additional hosts of stars that your unaided vision would never have +given you knowledge of. Any part of the sky may be observed; but, just +to give an illustration, I shall take one special region, namely, that +of the Great Bear (Fig. 1). The seven well-known stars are here shown, +four of which form a sort of oblong, while the other three represent +the tail. I would like you to make this little experiment. On a fine +clear night, count how many stars there are within this oblong; they +are all very faint, but you will be able to see a few, and, with good +sight, and on a clear night, you may see perhaps ten. Next take your +opera-glass and sweep it over the same region; if you will carefully +count the stars it shows, you will find fully two hundred; so that +the opera-glass has, in this part of the sky, revealed nearly twenty +times as many stars as could be seen without its aid. As six thousand +stars can be seen by the eye all over the heavens, we may fairly +expect that twenty times that number--that is to say, one hundred and +twenty thousand stars--could be shown by the opera-glass over the +entire sky. Let us go a step further, and employ a telescope, the +object-glass of which is three inches across. This is a useful +telescope to have, and, if a good one, will show multitudes of +pleasing objects, though an astronomer would not consider it very +powerful. An instrument like this, small enough to be carried in the +hand, has been applied to the task of enumerating the stars in the +northern half of the sky, and three hundred and twenty thousand stars +were counted. Indeed, the actual number that might have been seen with +it is considerably greater, for when the astronomer Argelander made +this memorable investigation he was unable to reckon many of the stars +in localities where they lay very close together. This grand count +only extended to half the sky, and, assuming that the other half is as +richly inlaid with stars, we see that a little telescope like that we +have supposed will, when swept over the heavens, reveal a number of +stars which exceeds that of the population of any city in England +except London. It exhibits more than one hundred times as many stars +as our eyes could possibly reveal. Still, we are only at the beginning +of the count; the very great telescopes add largely to the number. +There are multitudes of stars which in small instruments we cannot +see, but which are distinctly visible from our great observatories. +That telescope would be still but a comparatively small one which +would show as many stars in the sky as there are people living in the +mighty city of London; and with the greatest instruments, the tale of +stars has risen to a number far greater than that of the entire +population of Great Britain. + +In addition to those stars which the largest telescopes show us, there +are myriads which make their presence evident in a wholly different +way. It is only in quite recent times that an attempt has been made to +develop fully the powers of photography in representing the celestial +objects. On a photographic plate which has been exposed to the sky in +a great telescope the stars are recorded by thousands. Many of these +may, of course, be observed with a good telescope, but there are not a +few others which no one ever saw in a telescope, which apparently no +one ever could see, though the photograph is able to show them. We do +not, however, employ a camera like that which the photographer uses +who is going to take your portrait. The astronomer's plate is put into +his telescope, and then the telescope is turned towards the sky. On +that plate the stars produce their images, each by its own light. Some +of these images are excessively faint, but we give a very long +exposure of an hour or two hours; sometimes as much as four hours' +exposure is given to a plate so sensitive that a mere fraction of a +second would sufficiently expose it during the ordinary practice of +taking a photograph in daylight. We thus afford sufficient time to +enable the fainter objects to indicate their presence upon the +sensitive film. Even with an exposure of a single hour a picture +exhibiting sixteen thousand stars has been taken by Mr. Isaac Roberts, +of Liverpool. Yet the portion of the sky which it represents is only +one ten-thousandth part of the entire heavens. It should be added that +the region which Mr. Roberts has photographed is furnished with stars +in rather exceptional profusion. + +Here, at last, we have obtained some conception of the sublime scale +on which the stellar universe is constructed. Yet even these plates +cannot represent all the stars that the heavens contain. We have every +reason for knowing that with larger telescopes, with more sensitive +plates, with more prolonged exposures, ever fresh myriads of stars +will be brought within our view. + +You must remember that every one of these stars is truly a sun, a +lamp, as it were, which doubtless gives light to other objects in its +neighborhood as our sun sheds light upon this earth and the other +planets. In fact, to realize the glories of the heavens you should try +to think that the brilliant points you see are merely the luminous +points of the otherwise invisible universe. + +Standing one fine night on the deck of a Cunarder we passed in open +ocean another great Atlantic steamer. The vessel was near enough for +us to see not only the light from the mast-head but also the little +beams from the several cabin ports; and we could see nothing of the +ship herself. Her very existence was only known to us by the twinkle +of these lights. Doubtless her passengers could see, and did see, the +similar lights from our own vessel, and they probably drew the correct +inference that these lights indicated a great ship. + +Consider the multiplicity of beings and objects in a ship: the +captain and the crew, the passengers, the cabins, the engines, the +boats, the rigging, and the stores. Think of all the varied interests +there collected and then reflect that out on the ocean, at night, the +sole indication of the existence of this elaborate structure was given +by the few beams of light that happened to radiate from it. Now raise +your eyes to the stars; there are the twinkling lights. We cannot see +what those lights illuminate, we can only conjecture what untold +wealth of non-luminous bodies may also lie in their vicinity; we may, +however, feel certain that just as the few gleaming lights from a ship +are utterly inadequate to give a notion of the nature and the contents +of an Atlantic steamer, so are the twinkling stars utterly inadequate +to give even the faintest conception of the extent and the interest of +the universe. We merely see self-luminous bodies, but of the +multitudes of objects and the elaborate systems of which these bodies +are only the conspicuous points we see nothing and we know very +little. We are, however, entitled to infer from an examination of our +own star--the sun--and of the beautiful system by which it is +surrounded, that these other suns may be also splendidly attended. +This is quite as reasonable a supposition as that a set of lights seen +at night on the Atlantic Ocean indicates the existence of a fine ship. + + +The Clusters of Stars. + +On a clear night you can often see, stretching across the sky, a track +of faint light, which is known to astronomers as the "Milky Way." It +extends below the horizon, and then round the earth to form a girdle +about the heavens. When we examine the Milky Way with a telescope we +find, to our amazement, that it consists of myriads of stars, so small +and so faint that we are not able to distinguish them individually; we +merely see the glow produced from their collective rays. Remembering +that our sun is a star, and that the Milky Way surrounds us, it would +almost seem as if our sun were but one of the host of stars which form +this cluster. + +There are also other clusters of stars, some of which are exquisitely +beautiful telescopic spectacles. I may mention a celebrated pair of +these objects which lies in the constellation of Perseus. The sight of +them in a great telescope is so imposing that no one who is fit to +look through a telescope could resist a shout of wonder and admiration +when first they burst on his view. But there are other clusters. Here +is a picture of one which is known as the "Globular Cluster in the +Centaur" (Fig. 2). It consists of a ball of stars, so far off that, +however large these several suns may actually be, they have dwindled +down to extremely small points of light. A homely illustration may +serve to show the appearance which a globular cluster presents in a +good telescope. I take a pepper-caster, and on a sheet of white paper +I begin to shake out the pepper until there is a little heap at the +centre and other grains are scattered loosely about. Imagine that +every one of those grains of pepper was to be transformed into a tiny +electric light, and then you have some idea of what a cluster of stars +would look like when viewed through a telescope of sufficient power. +There are multitudes of such groups scattered through the depths of +space. They require our biggest telescopes to show them adequately. We +have seen that our sun is a star, being only one of a magnificent +cluster that forms the Milky Way. We have also seen that there are +other groups scattered through the length and depth of space. It is +thus we obtain a notion of the rank which our earth holds in the +scheme of things celestial. + +[Illustration: FIG. 2. GLOBULAR CLUSTER IN THE CENTAUR.] + + +The Rank of the Earth as a Globe in Space. + +Let me give an illustration with the view of explaining more fully the +nature of the relation which the earth bears to the other globes which +abound through space, and you must allow me to draw a little upon my +imagination. I shall suppose that the mails of our country extend not +only over this globe, but that they also communicate with other +worlds; that postal arrangements exist between Mars and the earth, +between the sun and Orion--in fact, everywhere throughout the whole +extent of the universe. We shall consider how our letters are to be +addressed. Let us take the case of Mr. John Smith, merchant, who lives +at 1001, Piccadilly; and let us suppose that Mr. John Smith's business +transactions are of such an extensive nature that they reach not only +all over this globe, but away throughout space. I shall suppose that +the firm has a correspondent residing--let us say in the constellation +of the Great Bear; and when this man of business wants to write to Mr. +Smith from these remote regions, what address must he put upon the +letter, so that the Postmaster-General of the universe shall make no +mistake about its delivery? He will write as follows:-- + + MR. JOHN SMITH, + 1001 Piccadilly, + London, + England, + Europe, + Earth, + Near the Sun, + Milky Way, + The Universe. + +Let us now see what the several lines of this address mean. Of course +we put down the name of Mr. John Smith in the first line, and then we +will add "1001 Piccadilly" for the second; but as the people in the +Great Bear are not likely to know where Piccadilly is, we shall add +"London" underneath. As even London itself cannot be well known +everywhere, it is better to write "England." This would surely find +Mr. John Smith from any post-office on this globe. From other globes, +however, the supreme importance of England may not be so immediately +recognized, and therefore it is as well to add another line, "Europe." +This ought to be sufficient, I think, for any post-office in the solar +system. Europe is big enough to be visible from Mars or Venus, and +should be known to the post-office people there, just as we know and +have names for the continents on Mars. But further away there might be +a little difficulty; from Uranus and Neptune the different regions on +our earth can never have been distinguished, and therefore we must add +another line to indicate the particular globe of the solar system +which contains Europe. Mark Twain tells us that there was always one +thing in astronomy which specially puzzled him, and that was to know +how we found out the names of the stars. We are, of course, in +hopeless ignorance of the name by which this earth is called among +other intelligent beings elsewhere who can see it. I can only adopt +the title of "Earth," and therefore I add this line. Now our address +is so complete that from anywhere in the solar system--from Mercury, +from Jupiter, or Neptune--there ought to be no mistake about the +letter finding its way to Mr. John Smith. But from his correspondent +in the Great Bear this address would be still incomplete; they cannot +see our earth from there, and even the sun himself only looks like a +small star--like one, in fact, of thousands of stars elsewhere. +However, each star can be distinguished, and our sun may, for +instance, be recognized from the Great Bear by some designation. We +shall add the line "Near the Sun," and then I think that from this +constellation, or from any of the other stars around us, the address +of Mr. John Smith may be regarded as complete. But Mr. Smith's +correspondence may be still wider. He may have an agent living in the +cluster of Perseus or on some other objects still fainter and more +distant; then "Near the Sun" is utterly inadequate as a concluding +line to the address, for the sun, if it can be seen at all from +thence, will be only of the significance of an excessively minute +star, no more to be designated by a special name than are each of the +several leaves on the trees of a forest. What this distant +correspondent will be acquainted with is not the earth or the sun but +only the cluster of stars among which the sun is but a unit. Again we +use our own name to denote the cluster, and we call it the "Milky +Way." When we add this line, we have made the address of Mr. John +Smith as complete as circumstances will permit. I think a letter +posted to him anywhere ought to reach its destination. To perfect it, +however, we will finish up with one line more--"The Universe." + + +The Distances of the Stars. + +I must now tell you something about the distances of the stars. I +shall not make the attempt to explain fully how astronomers make such +measurements, but I will give you some notion of how it is done. You +may remember I showed you how we found the distance of a globe that +was hung from the ceiling. The principle of the method for finding the +distance of a star is somewhat similar, except that we make the two +observations not from the two ends of a table, not even from opposite +sides of the earth, but from two opposite points on the earth's orbit, +which are therefore at a distance of one hundred and eighty-six +million miles. Imagine that on Midsummer Day, when standing on the +earth here, I measure with a piece of card the angle between the star +and the sun. Six months later, on Midwinter Day, when the earth is at +the opposite point of its orbit, I again measure the angle between the +same star and the sun, and we can now determine the star's distance by +making a triangle. I draw a line a foot long, and we will take this +foot to represent one hundred and eighty-six million miles, the +distance between the two stations; then placing the cards at the +corners, I rule the two sides and complete the triangle, and the star +must be at the remaining corner; then I measure the sides of the +triangle, and how many feet they contain, and recollecting that each +foot corresponds to one hundred and eighty-six million miles, we +discover the distance of the star. If the stars were comparatively +near us, the process would be a very simple one; but, unfortunately, +the stars are so extremely far off that this triangle, even with a +base of only one foot, must have its sides many miles long. Indeed, +astronomers will tell you that there is no more delicate or +troublesome work in the whole of their science than that of +discovering the distance of a star. + +In all such measurements we take the distance from the earth to the +sun as a conveniently long measuring-rod, whereby to express the +results. The nearest stars are still hundreds of thousands of times as +far off as the sun. Let us ponder for a little on the vastness of +these distances. We shall first express them in miles. Taking the +sun's distance to be ninety-three million miles, then the distance of +the nearest fixed star is about twenty millions of millions of +miles--that is to say, we express this by putting down a 2 first, and +then writing thirteen ciphers after it. It is, no doubt, easy to speak +of such figures, but it is a very different matter when we endeavor to +imagine the awful magnitude which such a number indicates. I must try +to give some illustrations which will enable you to form a notion of +it. At first I was going to ask you to try and count this number, but +when I found it would require at least three hundred thousand years, +counting day and night without stopping, before the task was over, it +became necessary to adopt some other method. + +When on a visit in Lancashire I was once kindly permitted to visit a +cotton mill, and I learned that the cotton yarn there produced in a +single day would be long enough to wind round this earth twenty-seven +times at the equator. It appears that the total production of cotton +yarn each day in all the mills together would be on the average about +one hundred and fifty-five million miles. In fact, if they would only +spin about one-fifth more, we could assert that Great Britain produced +enough cotton yarn every day to stretch from the earth to the sun and +back again! It is not hard to find from these figures how long it +would take for all the mills in Lancashire to produce a piece of yarn +long enough to reach from our earth to the nearest of the stars. If +the spinners worked as hard as ever they could for a year, and if all +the pieces were then tied together, they would extend to only a small +fraction of the distance; nor if they worked for ten years, or for +twenty years, would the task be fully accomplished. Indeed, upwards of +four hundred years would be necessary before enough cotton could be +grown in America and spun in this country to stretch over a distance +so enormous. All the spinning that has ever yet been done in the world +has not formed a long enough thread! + +There is another way in which we can form some notion of the immensity +of these sidereal distances. You will recollect that, when we were +speaking of Jupiter's moons, I told you of the beautiful discovery +which their eclipses enabled astronomers to make. It was thus found +that light travels at the enormous speed of about one hundred and +eighty-five thousand miles per second. It moves so quickly that within +a single second a ray would flash two hundred times from London to +Edinburgh and back again. + +We said that a meteor travels one hundred times as swiftly as a +rifle-bullet; but even this great speed seems almost nothing when +compared with the speed of light, which is ten thousand times as +great. Suppose some brilliant outbreak of light were to take place in +a distant star--an outbreak which would be of such intensity that the +flash from it would extend far and wide throughout the universe. The +light would start forth on its voyage with terrific speed. Any +neighboring star which was at a distance of less than one hundred and +eighty-five thousand miles would, of course, see the flash within a +second after it had been produced. More distant bodies would receive +the intimation after intervals of time proportioned to their +distances. Thus, if a body were one million miles away, the light +would reach it in from five to six seconds, while over a distance as +great as that which separates the earth from the sun the news would be +carried in about eight minutes. We can calculate how long a time must +elapse ere the light shall travel over a distance so great as that +between the star and our earth. You will find that from the nearest of +the stars the time required for the journey will be over three years. +Ponder on all that this involves. That outbreak in the star might be +great enough to be visible here, but we could never become aware of it +till three years after it had happened. When we are looking at such a +star to-night we do not see it as it is at present, for the light that +is at this moment entering our eyes has travelled so far that it has +been three years on the way. Therefore, when we look at the star now +we see it as it was three years previously. In fact, if the star were +to go out altogether, we might still continue to see it twinkling for +a period of three years longer, because a certain amount of light was +on its way to us at the moment of extinction, and so long as that +light keeps arriving here, so long shall we see the star showing as +brightly as ever. When, therefore, you look at the thousands of stars +in the sky to-night, there is not one that you see as it is now, but +as it was years ago. + +I have been speaking of the stars that are nearest to us, but there +are others much farther off. It is true we cannot find the distances +of these more remote objects with any degree of accuracy, but we can +convince ourselves how great that distance is by the following +reasoning. Look at one of the brightest stars. Try to conceive that +the object was carried away further into the depths of space, until it +was ten times as far from us as it is at present, it would still +remain bright enough to be recognized in quite a small telescope; even +if it were taken to one hundred times its original distance it would +not have withdrawn from the view of a good telescope; while if it +retreated one thousand times as far as it was at first it would still +be a recognizable point in our mightiest instruments. Among the stars +which we can see with our telescopes, we feel confident there must be +many from which the light has expended hundreds of years, or even +thousands of years, on the journey. When, therefore, we look at such +objects, we see them, not as they are now, but as they were ages ago; +in fact, a star might have ceased to exist for thousands of years, and +still be seen by us every night as a twinkling point in our great +telescopes. + +Remembering these facts, you will, I think, look at the heavens with a +new interest. There is a bright star, Vega, or Alpha Lyræ, a beautiful +gem, so far off that the light from it which now reaches our eyes +started before many of my audience were born. Suppose that there are +astronomers residing on worlds amid the stars, and that they have +sufficiently powerful telescopes to view this globe, what do you think +they would observe? They will not see our earth as it is at present; +they will see it as it was years (and sometimes many years) ago. There +are stars from which if England could now be seen, the whole of the +country would be observed at this present moment to be in a great +state of excitement at a very auspicious event. Distant astronomers +might notice a great procession in London, and they could watch the +coronation of a youthful queen amid the enthusiasm of a nation. There +are other stars still further, from which, if the inhabitants had good +enough telescopes, they would now see a mighty battle in progress not +far from Brussels. One splendid army could be beheld hurling itself +time after time against the immovable ranks of the other. They would +not, indeed, be able to hear the ever-memorable "Up, Guards, and at +them!" but there can be no doubt that there are stars so far away that +the rays of light which started from the earth on the day of the +battle of Waterloo are only just arriving there. Further off still, +there are stars from which a bird's-eye view could be taken at this +very moment of the signing of Magna Charta. There are even stars from +which England, if it could be seen at all, would now appear, not as +the great England we know, but as a country covered by dense forests, +and inhabited by painted savages, who waged incessant war with wild +beasts that roamed through the island. The geological problems that +now puzzle us would be quickly solved could we only go far enough into +space and had we only powerful enough telescopes. We should then be +able to view our earth through the successive epochs of past +geological time; we should be actually able to see those great animals +whose fossil remains are treasured in our museums tramping about over +the earth's surface, splashing across its swamps, or swimming with +broad flippers through its oceans. Indeed, if we could view our own +earth reflected from mirrors in the stars, we might still see Moses +crossing the Red Sea, or Adam and Eve being expelled from Eden. + +So important is the subject of star distance that I am tempted to give +one more illustration in order to bring before you some conception of +how vast such distances are. I shall take, as before, the nearest of +the stars so far as known to us, and I hope to be forgiven for taking +an illustration of a practical and a commercial kind instead of one +more purely scientific. I shall suppose that a railway is about to be +made from London to Alpha Centauri. The length of that railway, of +course, we have already stated: it is twenty billions of miles. So I +am now going to ask your attention to the simple question as to the +fare which it would be reasonable to charge for the journey. We shall +choose a very cheap scale on which to compute the price of a ticket. +The parliamentary rate here is, I believe, a penny for every mile. We +will make our interstellar railway fares much less even than this; we +shall arrange to travel at the rate of one hundred miles for every +penny. That, surely, is moderate enough. If the charges were so low +that the journey from London to Edinburgh only cost fourpence, then +even the most unreasonable passenger would be surely contented. On +these terms how much do you think the fare from London to this star +ought to be? I know of one way in which to make our answer +intelligible. There is a National Debt with which your fathers are, +unhappily, only too well acquainted; you will know quite enough about +it yourselves in those days when you have to pay income tax. This debt +is so vast that the interest upon it is about sixty thousand pounds a +day, the whole amount of the National Debt being six hundred and +thirty-eight millions of pounds. + +If you went to the booking-office with the whole of this mighty sum in +your pocket--but stop a moment; could you carry it in your pocket? +Certainly not, if it were in sovereigns. You would find that after you +had as many sovereigns as you could conveniently carry there would +still be some left--so many, indeed, that it would be necessary to get +a cart to help you on with the rest. When the cart had as great a load +of sovereigns as the horse could draw there would be still some more, +and you would have to get another cart; but ten carts, twenty carts, +fifty carts, would not be enough. You would want five thousand of +these before you would be able to move off towards the station with +your money. When you did get there and asked for a ticket at the rate +of one hundred miles for a penny, do you think you would get any +change? No doubt some little time would be required to count the +money, but when it was counted the clerk would tell you that there was +not enough--that he must have nearly two hundred millions of pounds +more. + +That will give some notion of the distance of the nearest star, and we +may multiply it by ten, by one hundred, and even by one thousand, and +still not attain to the distance of some of the more remote stars that +the telescope shows us. + +On account of the immense distances of the stars we can only perceive +them to be mere points of light. We can never see a star to be a globe +with marks on it like the moon, or like one of the planets--in fact, +the better the telescope the smaller does the star seem, though, of +course, its brightness is increased with every addition to the +light-grasping power of the instrument. + + +The Brightness and Color of Stars. + +Another point to be noticed is the arrangement of stars in classes, +according to their lustre. The brightest stars, of which there are +about twenty, are said to be of the first magnitude. Those just +inferior to the first magnitude are ranked as the second; and those +just lower than the second are estimated as the third; and so on. The +smallest points that your unaided eyes will show you are of about the +sixth magnitude. Then the telescope will reveal stars still fainter +and fainter, down to what we term the seventeenth or eighteenth +magnitudes, or even lower still. The number of stars of each magnitude +increases very much in the classes of small ones. + +Most of the stars are white, but many are of a somewhat ruddy hue. +There are a few telescopic points which are intensely red, some +exhibit beautiful golden tints, while others are blue or green. + +There are some curious stars which regularly change their brilliancy. +Let me try to illustrate the nature of these variables. Suppose that +you were looking at a street gas-lamp from a very long distance, so +that it seemed a little twinkling light; and suppose that some one was +preparing to turn the gas-cock up and down. Or, better still, imagine +a little machine which would act regularly so as to keep the light +first of all at its full brightness for two days and a half, and then +gradually turn it down until in three or four hours it declines to a +feeble glimmer. In this low state the light remains for twenty +minutes; then during three or four hours the gas is to be slowly +turned on again until it is full. In this condition the light will +remain for two days and a half, and then the same series of changes is +to recommence. This would be a very odd form of gas-lamp. There would +be periods of two days and a half during which it would remain at its +full; these would be separated by intervals of about seven hours, when +the gradual turning down and turning up again would be in progress. + +The imaginary gas-lamp is exactly paralleled by a star Algol, in the +constellation of Perseus (Fig. 3), which goes through the series of +changes I have indicated. Ordinarily speaking, it is a bright star of +the second magnitude, and, whatever be the cause, the star performs +its variations with marvellous uniformity. In fact, Algol has always +arrested the attention of those who observed the heavens, and in early +times was looked on as the eye of a demon. There are many other stars +which also change their brilliancy. Most of them require much longer +periods than Algol, and sometimes a new star which nobody has ever +seen before will suddenly kindle into brilliancy. It is now known that +the bright star Algol is attended by a dark companion. This dark star +sometimes comes between Algol and the observer and cuts off the light. +Thus it is that the diminution of brightness is produced. + +[Illustration: FIG. 3. PERSEUS AND ITS NEIGHBORING STARS INCLUDING +ALGOL.] + + +Double Stars. + +Whenever you have a chance of looking at the heavens through a +telescope, you should ask to be shown what is called _a double star_. +There are many stars in the heavens which present no remarkable +appearance to the unaided eye, but which a good telescope at once +shows to be of quite a complex nature. These are what we call double +stars, in which two quite distinct stars are placed so close together +that the unaided eye is unable to separate them. Under the magnifying +power of the telescope, however, they are seen to be distinct. In +order to give some notion of what these objects are like, I shall +briefly describe three of them. The first lies in that best known +constellation, the Great Bear. If you look at his tail, which consists +of three stars, you will see that near the middle one of the three a +small star is situated; we call this little star Alcor, but it is the +brighter one near Alcor to which I specially call your attention. The +sharpest eye would never suspect that it was composed of two stars +placed close together. Even a small telescope will, however, show this +to be the case, and this is the easiest and the first observation that +a young astronomer should make when beginning to turn a telescope to +the heavens. Of course you will not imagine that I mean Alcor to be +the second component of the double star; it is the bright star near +Alcor which is the double. Here are two marbles, and these marbles are +fastened an inch apart. You can see them, of course, to be separate; +but if the pair were moved further and further away, then you would +soon not be able to distinguish between them, though the actual +distance between the marbles had not altered. Look at these two wax +tapers which are now lighted; the little flames are an inch apart. You +would have to view them from a station a third of a mile away if the +distance between the two flames were to appear the same as that +between the two components of this double star. Your eye would never +be able to discriminate between two lights only an inch apart at so +great a distance; a telescope would, however, enable you to do so, and +this is the reason why we have to use telescopes to show us double +stars. + +You might look at that double star year after year throughout the +course of a long life without finding any appreciable change in the +relative positions of its components. But we know that there is no +such thing as rest in the universe; even if you could balance a body +so as to leave it for a moment at rest, it would not stay there, for +the simple reason that all the bodies round it in every direction are +pulling at it, and it is certain that the pull in one direction will +preponderate, so that move it must. Especially is this true in the +case of two suns like those forming a double star. Placed +comparatively near each other they could not remain permanently in +that position; they must gradually draw together and come into +collision with an awful crash. There is only one way by which such a +disaster could be averted. That is by making one of these stars +revolve around the other just as the earth revolves around the sun, or +the moon revolves around the earth. Some motion must, therefore, be +going on in every genuine double star, whether we have been able to +see that motion or not. + +Let us now look at another double star of a different kind. This time +it is in the constellation of Gemini. The heavenly twins are called +Castor and Pollux. Of these, Castor is a very beautiful double star, +consisting of two bright points, a great deal closer together than +were those in the Great Bear; consequently a better telescope is +required for the purpose of showing them separately. Castor has been +watched for many years, and it can be seen that one of these stars is +slowly revolving around the other; but it takes a very long time, +amounting to hundreds of years, for a complete circuit to be +accomplished. This seems very astonishing, but when you remember how +exceedingly far Castor is, you will perceive that that pair of stars +which appear so close together that it requires a telescope to show +them apart must indeed be separated by hundreds of millions of miles. +Let us try to conceive our own system transformed into a double star. +If we took our outermost planet--Neptune--and enlarged him a good +deal, and then heated him sufficiently to make him glow like a sun, he +would still continue to revolve round our sun at the same distance, +and thus a double star would be produced. An inhabitant of Castor who +turned his telescope towards us would be able to see the sun as a +star. He would not, of course, be able to see the earth, but he might +see Neptune like another small star close to the sun. If generations +of astronomers in Castor continued their observations of our system, +they would find a binary star, of which one component took a century +and a half to go round the other. Need we then be surprised that when +we look at Castor we observe movements that seem very slow? + +There is often so much diffused light about the bright stars seen in a +telescope, and so much twinkling in some states of the atmosphere, +that stars appear to dance about in rather a puzzling fashion, +especially to one who is not accustomed to astronomical observations. +I remember hearing how a gentleman once came to visit an observatory. +The astronomer showed him Castor through a powerful telescope as a +fine specimen of a double star, and then, by way of improving his +little lesson, the astronomer mentioned that one of these stars was +revolving around the other. "Oh, yes," said the visitor, "I saw them +going round and round in the telescope." He would, however, have had +to wait for a few centuries with his eye to the instrument before he +would have been entitled to make this assertion. + +Double stars also frequently delight us by giving beautifully +contrasted colors. I dare say you have often noticed the red and the +green lights that are used on railways in the signal lamps. Imagine +one of those red and one of those green lights away far up in the sky +and placed close together, then you would have some idea of the +appearance that a colored double star presents, though, perhaps, I +should add that the hues in the heavenly bodies are not so vividly +different as are those which our railway people find necessary. There +is a particularly beautiful double star of this kind in the +constellation of the Swan. You could make an imitation of it by boring +two holes, with a red-hot needle, in a piece of card, and then +covering one of these holes with a small bit of the topaz-colored +gelatine with which Christmas crackers are made. The other star is to +be similarly colored with blue gelatine. A slide made on this +principle placed in the lantern gives a very good representation of +these two stars on the screen. There are many other colored doubles +besides this one; and, indeed, it is noteworthy that we hardly ever +find a blue or a green star by itself in the sky; it is always as a +member of one of these pairs. + + +How We Find What the Stars are Made of. + +Here is a piece of stone. If I wanted to know what it was composed of, +I should ask a chemist to tell me. He would take it into his +laboratory, and first crush it into powder, and then, with his test +tubes, and with the liquids which his bottles contain, and his +weighing scales, and other apparatus, he would tell all about it; +there is so much of this, and so much of that, and plenty of this, and +none at all of that. But now, suppose you ask this chemist to tell you +what the sun is made of, or one of the stars. Of course, you have not +a sample of it to give him; how, then, can he possibly find out +anything about it? Well, he can tell you something, and this is the +wonderful discovery that I want to explain to you. We now put down the +gas, and I kindle a brilliant red light. Perhaps some of those whom I +see before me have occasionally ventured on the somewhat dangerous +practice of making fire-works. If there is any boy here who has ever +constructed sky-rockets, and put the little balls into the top which +are to burn with such vivid colors when the explosion takes place, he +will know that the substance which tinged that fire red must have been +strontium. He will recognize it by the color; because strontium gives +a red light which nothing else will give. Here are some of these +lightning papers, as they are called; they are very pretty and very +harmless; and these, too, give brilliant red flashes as I throw them. +The red tint has, no doubt, been produced by strontium also. You see +we recognized the substance simply by the color of the light it +produced when burning. + +Perhaps some of you have tried to make a ghost at Christmas by +dressing up in a sheet, and bearing in your hand a ladle blazing with +a mixture of common salt and spirits of wine, the effect produced +being a most ghastly one. Some mammas will hardly thank me for this +suggestion, unless I add that the ghost must walk about cautiously, +for otherwise the blazing spirit would be very apt to produce +conflagrations of a kind more extensive than those intended. However, +by the kindness of Professor Dewar, I am enabled to show the +phenomenon on a splendid scale, and also free from all danger. I +kindle a vivid flame of an intensely yellow color, which I think the +ladies will unanimously agree is not at all becoming to their +complexions, while the pretty dresses have lost their variety of +colors. Here is a nice bouquet, and yet you can hardly distinguish the +green of the leaves from the brilliant colors of the flowers, except +by trifling differences of shade. Expose to this light a number of +pieces of variously colored ribbon, pink and red and green and blue, +and their beauty is gone; and yet we are told that this yellow is a +perfectly pure color; in fact, the purest color that can be produced. +I think we have to be thankful that the light which our good sun sends +us does not possess purity of that description. There is one substance +which will produce that yellow light; it is a curious metal called +sodium--a metal so soft that you can cut it with a knife, and so light +that it will float on water; while, still more strange, it actually +takes fire the moment it is dropped on the water. It is only in a +chemical laboratory that you will be likely to meet with the actual +metallic sodium, yet in other forms the substance is one of the most +abundant in nature. Indeed, common salt is nothing but sodium closely +united with a most poisonous gas, a few respirations of which would +kill you. But this strange metal and this noxious gas, when united, +become simply the salt for our eggs at breakfast. This pure yellow +light, wherever it is seen, either in the flame of spirits of wine +mixed with salt or in that great blaze at which we have been looking, +is characteristic of sodium. Wherever you see that particular kind of +light, you know that sodium must have been present in the body from +which it came. + +We have accordingly learned to recognize two substances, namely, +strontium and sodium, by the different lights which they give out when +burning. To these two metals we may add a third. Here is a strip of +white metallic ribbon. It is called magnesium. It seems like a bit of +tin at the first glance, but indeed it is a very different substance +from tin; for, look, when I hold it in the spirit-lamp, the strip of +metal immediately takes fire, and burns with a white light so dazzling +that it pales the gas-flames to insignificance. There is no other +substance which will, when kindled, give that particular kind of light +which we see from magnesium. I can recommend this little experiment as +quite suitable for trying at home; you can buy a bit of magnesium +ribbon for a trifle at the opticians; it cannot explode or do any +harm, nor will you get into any trouble with the authorities provided +you hold it when burning over a tray or a newspaper, so as to prevent +the white ashes from falling on the carpet. + +There are, in nature, a number of simple bodies called elements. +Every one of these, when ignited under suitable conditions, emits a +light which belongs to it alone, and by which it can be distinguished +from every other substance. I do not say that we can try the +experiments in the simple way I have here indicated. Many of the +materials will yield light which will require to be studied by much +more elaborate artifices than those which have sufficed for us. But +you will see that the method affords a means of finding out the actual +substances present in the sun or in the stars. There is a practical +difficulty in the fact that each of the heavenly bodies contains a +number of different elements; so that in the light it sends us the +hues arising from distinct substances are blended into one beam. The +first thing to be done is to get some way of splitting up a beam of +light, so as to discover the components of which it is made. You might +have a skein of silks of different hues tangled together, and this +would be like the sunbeam as we receive it in its unsorted condition. +How shall we untangle the light from the sun or a star? I will show +you by a simple experiment. Here is a beam from the electric light; +beautifully white and bright, is it not? It looks so pure and simple, +but yet that beam is composed of all sorts of colors mingled together, +in such proportions as to form white light. I take a wedge-shaped +piece of glass called a prism, and when I introduce it into the course +of the beam, you see the transformation that has taken place (Fig. 4). +Instead of the white light you have now all the colors of the +rainbow--red, orange, yellow, green, blue, indigo, violet, marked by +their initial letters in the figure. These colors are very beautiful, +but they are transient, for the moment we take away the prism they +all unite again to form white light. You see what the prism has done; +it has bent all the light in passing through it; but it is more +effective in bending the blue than the red, and consequently the blue +is carried away much further than the red. Such is the way in which we +study the composition of a heavenly body. We take a beam of its light, +we pass it through a prism, and immediately it is separated into its +components; then we compare what we find with the lights given by the +different elements, and thus we are enabled to discover the substances +which exist in the distant object whose light we have examined. I do +not mean to say that the method is a simple one; all I am endeavoring +to show is a general outline of the way in which we have discovered +the materials present in the stars. The instrument that is employed +for this purpose is called the spectroscope. And perhaps you may +remember that name by these lines, which I have heard from an +astronomical friend:-- + + "Twinkle, twinkle, little star, + Now we find out what you are, + When unto the midnight sky, + We the spectroscope apply." + +[Illustration: FIG. 4. HOW A RAY OF LIGHT IS SPLIT UP.] + +I am sure it will interest everybody to know that the elements which +the stars contain are not altogether different from those of which the +earth is made. It is true there may be substances in the stars of +which we know nothing here; but it is certain that many of the most +common elements on the earth are present in the most distant bodies. I +shall only mention one, the metal iron. That useful substance has been +found in some of the stars which lie at almost incalculable distances +from the earth. + + +The Nebulæ. + +In drawing towards the close of these lectures I must say a few words +about some dim and mysterious objects to which we have not yet +alluded. They are what are called nebulæ, or little clouds; and in +one sense they are justly called little, for each of them occupies but +a very small spot in the sky as compared with that which would be +filled by an ordinary cloud in our air. The nebulæ are, however, +objects of the most stupendous proportions. Were our earth and +thousands of millions of bodies quite as big all put together, they +would not be nearly so great as one of these nebulæ. Astronomers +reckon up the various nebulæ by thousands, but I must add that most of +them are apparently faint and uninteresting. A nebula is sometimes +liable to be mistaken for a comet. The comet is, as I have already +explained, at once distinguished by the fact that it is moving and +changing its appearance from hour to hour, while scores of years +elapse without changes in the aspect or position of a nebula. The most +powerful telescopes are employed in observing these faint objects. I +take this opportunity of showing a picture of an instrument suitable +for such observations. It is the great reflector of the Paris +Observatory (Fig. 5). + +[Illustration: FIG. 5. A GREAT REFLECTING TELESCOPE.] + +[Illustration: FIG. 6. THE RING NEBULA IN LYRA, UNDER DIFFERENT +TELESCOPIC POWERS.] + +There are such multitudes of nebulæ that I can only show a few of the +more remarkable kinds. In Fig. 6 will be seen pictures of a curious +object in the constellation of Lyra seen under different telescopic +powers. This is a gigantic ring of luminous gas. To judge of the size +of this ring let us suppose that a railway were laid across it, and +the train you entered at one side was not to stop until it reached the +other side, how long do you think this journey would require? I +recollect some time ago a picture in _Punch_ which showed a train +about to start from London to Brighton, and the guard walking up and +down announcing to the passengers the alarming fact that "this train +stops nowhere." An old gentleman was seen vainly gesticulating out of +the window and imploring to be let out ere the frightful journey was +commenced. In the nebular railway the passengers would almost require +such a warning. + +Let the train start at a speed of a mile a minute, you would think, +surely, that it must soon cross the ring. But the minutes pass, an +hour has elapsed; so the distance must be sixty miles at all events. +The hours creep on into days, the days advance into years, and still +the train goes on. The years would lengthen out into centuries, and +even when the train had been rushing on for a thousand years with an +unabated speed of a mile a minute, the journey would certainly not +have been completed. Nor do I venture to say what ages must elapse ere +the terminus at the other side of the ring nebula would be reached. + +A cluster of stars viewed in a small telescope will often seem like a +nebula, for the rays of the stars become blended. A powerful telescope +will, however, dispel the illusion and reveal the separate stars. It +was, therefore, thought that all the nebulæ might be merely clusters +so exceedingly remote that our mightiest instruments failed to resolve +them into stars. But this is now known not to be the case. Many of +these objects are really masses of glowing gas; such are, for +instance, the ring nebulæ, of which I have just spoken, and the form +of which I can simulate by a pretty experiment. + +We take a large box with a round hole cut in one face, and a canvas +back at the opposite side. I first fill this box with smoke, and there +are different ways of doing so. Burning brown paper does not answer +well, because the supply of smoke is too irregular and the paper +itself is apt to blaze. A little bit of phosphorus set on fire yields +copious smoke, but it would be apt to make people cough, and, besides, +phosphorus is a dangerous thing to handle incautiously, and I do not +want to suggest anything which might be productive of disaster if the +experiment was repeated at home. A little wisp of hay, slightly damped +and lighted, will safely yield a sufficient supply, and you need not +have an elaborate box like this; any kind of old packing-case, or even +a bandbox with a duster stretched across its open top and a round hole +cut in the bottom, will answer capitally. While I have been speaking, +my assistant has kindly filled this box with smoke, and in order to +have a sufficient supply, and one which shall be as little +disagreeable as possible, he has mixed together the fumes of +hydrochloric acid and ammonia from two retorts shown in Fig. 7. A +still simpler way of doing the same thing is to put a little common +salt in a saucer and pour over it a little oil of vitriol; this is put +into the box, and over the floor of the box common smelling-salts is +to be scattered. You see there are dense volumes of white smoke +escaping from every corner of the box. I uncover the opening and give +a push to the canvas, and you see a beautiful ring flying across the +room; another ring and another follows. If you were near enough to +feel the ring, you would experience a little puff of wind; I can show +this by blowing out a candle which is at the other end of the table. +These rings are made by the air which goes into a sort of eddy as it +passes through the hole. All the smoke does is to render the air +visible. The smoke-ring is indeed quite elastic. If we send a second +ring hurriedly after the first, we can produce a collision, and you +see each of the two rings remains unbroken, though both are quivering +from the effects of the blow. They are beautifully shown along the +beam of the electric lamp, or, better still, along a sunbeam. + +[Illustration: FIG. 7. HOW TO MAKE THE SMOKE RINGS.] + +We can make many experiments with smoke-rings. Here, for instance, I +take an empty box, so far as smoke is concerned, but air-rings can be +driven forth from it, though you cannot see them, but you can feel +them even at the other side of the room, and they will, as you see, +blow out a candle. I can also shoot invisible air-rings at a column of +smoke, and when the missile strikes the smoke it produces a little +commotion and emerges on the other side, carrying with it enough of +the smoke to render itself visible, while the solid black looking ring +of air is seen in the interior. Still more striking is another way of +producing these rings, for I charge this box with ammonia, and the +rings from it you cannot see. There is a column of the vapor of +hydrochloric acid, that also you cannot see; but when the visible ring +enters the invisible column, then a sudden union takes place between +the vapor of the ammonia and the vapor of the hydrochloric acid; the +result is a solid white substance in extremely fine dust which renders +the ring instantly visible. + + +What the Nebulæ are made of. + +There is a fundamental difference between the illumination of these +little rings that I have shown you and the great rings in the heavens. +I had to illuminate our smoke with the help of the electric light, +for, unless I had done so, you would not have been able to see them. +This white substance formed by the union of ammonia and hydrochloric +acid has, of course, no more light of its own than a piece of chalk; +it requires other light falling upon it to make it visible. Were the +ring nebula in Lyra composed of this material, we could not see it. +The sunlight which illuminates the planets might, of course, light up +such an object as the ring, if it wrere comparatively near us; but +Lyra is at such a stupendous distance that any light which the sun +could send out there would be just as feeble as the light we receive +from a fixed star. Should we be able to show our smoke-rings, for +instance, if, instead of having the electric light, I merely cut a +hole in the ceiling and allowed the feeble twinkle of a star in the +Great Bear to shine through? In a similar way the sunbeams would be +utterly powerless to effect any illumination of objects in these +stellar distances. If the sun were to be extinguished altogether, the +calamity would no doubt be a very dire one so far as we are concerned, +but the effect on the other celestial bodies (moon and planets +excepted) would be of the slightest possible description. All the +stars of heaven would continue to shine as before. Not a point in one +of the constellations wrould be altered, not a variation in the +brightness, not a change in the hue of any star could be noticed. The +thousands of nebulæ and clusters would be absolutely unaltered; in +fact, the total extinction of the sun would be hardly remarked in the +newspapers published in the Pleiades or in Orion. There might possibly +be a little line somewhere in an odd corner to the effect "Mr. +So-and-So, our well-known astronomer, has noticed that a tiny star, +inconspicuous to the eye, and absolutely of no importance whatever, +has now become invisible." + +If, therefore, it be not the sun which lights up this nebula, where +else can be the source of its illumination? There can be no other star +in the neighborhood adequate to the purpose, for, of course, such an +object would be brilliant to us if it were large enough and bright +enough to impart sufficient illumination to the nebula. It would be +absurd to say that you could see a man's face by the light of a candle +while the candle itself was too faint or too distant to be visible. +The actual facts are, of course, the other way; the candle might be +visible, when it was impossible to discern the face which it lighted. + +Hence we learn that the ring nebula must shine by some light of its +own, and now we have to consider how it can be possible for such +material to be self-luminous. The light of a nebula does not seem to +be like flame; it can, perhaps, be better represented by the pretty +electrical experiment with Geissler's tubes. These are glass vessels +of various shapes, and they are all very nearly empty, as you will +understand when I tell you the way in which they have been prepared. A +little gas was allowed into each tube, and then almost all the gas was +taken out again, so that only a mere trace was left. I pass a current +of electricity through these tubes, and now you see they are glowing +with beautiful colors. The different gases give out lights of +different hues, and the optician has exerted his skill so as to make +the effect as beautiful as possible. The electricity, in passing +through these tubes, heats the gas which they contain, and makes it +glow; and just as this gas can, when heated sufficiently, give out +light, so does the great nebula, which is a mass of gas poised in +space, become visible in virtue of the heat which it contains. + +We are not left quite in doubt as to the constitution of these gaseous +nebulæ, for we can submit their light to the prism in the way I +explained when we were speaking of the stars. Distant though that ring +in Lyra may be, it is interesting to learn that the ingredients from +which it is made are not entirely different from substances we know on +our earth. The water in this glass, and every drop of water, is formed +by the union of two gases, of which one is hydrogen. This is an +extremely light material, as you see by a little balloon which ascends +so prettily when filled with it. Hydrogen also burns very readily, +though the flame is almost invisible. When I blow a jet of oxygen +through the hydrogen, I produce a little flame with a very intense +heat. For instance, I hold a steel pen in the flame, and it glows and +sputters, and falls down in white-hot drops. It is needless to say +that, as a constituent of water, hydrogen is one of the most important +elements on this earth. It is, therefore, of interest to learn that +hydrogen in some form or other is a constituent of the most distant +objects in space that the telescope has revealed. + + +Photographing the Nebulæ. + +[Illustration: FIG. 8. THE PLEIADES.] + +Of late years we have learned a great deal about nebulæ, by the help +which photography has given to us. Look at this group of stars which +constitutes that beautiful little configuration known as the Pleiades +(Fig. 8). It looks like a miniature representation of the Great Bear; +in fact, it would be far more appropriate to call the Pleiades the +Little Bear than to apply that title to another quite different +constellation, as has unfortunately been done. The Pleiades form a +group containing six or seven stars visible to the ordinary eye, +though persons endowed with exceptionally good vision can usually see +a few more. In an opera-glass the Pleiades becomes a beautiful +spectacle, though in a large telescope the stars appear too far apart +to make a really effective cluster. When Mr. Roberts took a photograph +of the Pleiades he placed a highly sensitive plate in his telescope, +and on that plate the Pleiades engraved their picture with their own +light. He left the plate exposed for hours, and on developing it not +only were the stars seen, but there were also patches of faint light +due to the presence of nebulæ. It could not be said that the objects +on the plate were fallacious, for another photograph was taken, when +the same appearances were reproduced. + +When we look at that pretty group of stars which has attracted +admiration during all time, we are to think that some of those stars +are merely the bright points in a vast nebula, invisible to our +unaided eyes or even to our mighty telescopes, though capable of +recording its trace on the photographic plate. Does not this give us a +greatly increased notion of the extent of the universe, when we +reflect that by photography we are enabled to see much which the +mightiest of telescopes had previously failed to disclose? + +Of all the nebulæ, numbering some thousands, there is but a single one +which can be seen without a telescope. It is in the constellation of +Andromeda, and on a clear dark night can just be seen with the unaided +eye as a faint stain of light on the sky. It has happened before now +that persons noticing this nebula for the first time have thought they +had discovered a comet. I would like you to try and find out this +object for yourselves. + +If you look at it with an opera-glass it appears to be distinctly +elongated. You can see more of its structure when you view it in +larger instruments, but its nature was never made clear until some +beautiful photographs were taken by Mr. Roberts (Fig. 9). +Unfortunately, the nebula in Andromeda has not been placed in the best +position for its portrait from our point of view. It seems as if it +were a rather flat-shaped object, turned nearly edgewise towards us. +To look at the pattern on a plate, you would naturally hold the plate +so as to be able to look at it squarely. The pattern would not be seen +well if the plate were so tilted that its edge was turned towards you. +That seems to be nearly the way in which we are forced to view the +nebula in Andromeda. We can trace in the photograph some divisions +extending entirely round the nebula, showing that it seems to be +formed of a series of rings; and there are some outlying portions +which form part of the same system. Truly this is a marvellous object. +It is impossible for us to form any conception of the true dimensions +of this gigantic nebula; it is so far off that we have never yet been +able to determine its distance. Indeed, I may take this opportunity of +remarking that no astronomer has yet succeeded in ascertaining the +distance of any nebula. Everything, however, points to the conclusion +that they are at least as far as the stars. + +[Illustration: FIG. 9. THE GREAT NEBULA IN ANDROMEDA.] + +It is almost impossible to apply the methods which we use in finding +the distance of a star to the discovery of the distance of the +nebulæ. These flimsy bodies are usually too ill-defined to admit of +being measured with the precision and delicacy required for the +determination of distance. The measurements necessary for this purpose +can only be made from one star-like point to another similar point. If +we could choose a star in the nebula and determine its distance, then +of course, we have the distance of the nebula itself; but the +difficulty is that we have, in general, no means of knowing whether +the star does actually lie in the object. It may, for anything we can +tell, lie billions of miles nearer to us, or billions of miles further +off, and by merely happening to lie in the line of sight, appear to +glimmer in the nebula itself. + +If we have any assurance that the star is surrounded by a mass of this +glowing vapor, then it may be possible to measure that nebula's +distance. It will occasionally happen that grounds can be found for +believing that a star which appears to be in the glowing gas does +veritably lie therein, and is not merely seen in the same direction. +There are hundreds of stars visible in a good drawing or a good +photograph of the famous object in Andromeda, and doubtless large +numbers of these are merely stars which happen to lie in the same line +of sight. The peculiar circumstances attending the history of one star +seem, however, to warrant us in making the assumption that it was +certainly in the nebula. The history of this star is a remarkable one. +It suddenly kindled from invisibility into brilliancy. How is a change +so rapid in the lustre of a star to be accounted for? In a few days +its brightness had undergone an extraordinary increase. Of course, +this does not tell us for certain that the star lay in the glowing +gas; but the most rational explanation that I have heard offered of +this occurrence is that due, I believe, to my friend Mr. Monck. He has +suggested that the sudden outbreak in brilliancy might be accounted +for on the same principles as those by which we explain the ignition +of meteors in our atmosphere. If a dark star, moving along with +terrific speed through space, were suddenly to plunge into a dense +region of the nebula, heat and light must be evolved in sufficient +abundance to transform the star into a brilliant object. If, +therefore, we knew the distance of this star at the time it was in +Andromeda, we should, of course, learn the distance of that +interesting object. This has been attempted, and it has thus been +proved that the Great Nebula must be very much further from us than is +that star of whose distance I attempted some time ago to give you a +notion. + +We thus realize the enormous size of the Great Nebula. It appears that +if, on a map of this object, we were to lay down, accurately to scale, +a map of the solar system, putting the sun in the centre and all the +planets around their true proportions out to the boundary traced by +Neptune, this area, vast though it is, would be a mere speck on the +drawing of the object. Our system would have to be enormously bigger +before it sufficed to cover anything like the area of the sky included +in one of these great objects. Here is a sketch of a nebula, Fig. 10, +and near I have marked a dot, which is to indicate our solar system. +We may feel confident that the Great Nebula is at the very least as +mighty as this proportion would indicate. + +[Illustration: FIG. 10. THE SOLAR SYSTEM AS COMPARED WITH A GREAT +NEBULA.] + + + + +RAIN AND SNOW + +(FROM THE FORMS OF WATER.) + +BY JOHN TYNDALL. + + +Oceanic Distillation. + +[Illustration: SNOW CRYSTALS.] + +At the equator, and within certain limits north and south of it, the +sun at certain periods of the year is directly overhead at noon. These +limits are called the Tropics of Cancer and of Capricorn. Upon the +belt comprised between these two circles the sun's rays fall with +their mightiest power; for here they shoot directly downwards, and +heat both earth and sea more than when they strike slantingly. + +When the vertical sunbeams strike the land they heat it, and the air +in contact with the hot soil becomes heated in turn. But when heated +the air expands, and when it expands it becomes lighter. This lighter +air rises, like wood plunged into water, through the heavier air +overhead. + +When the sunbeams fall upon the sea the water is warmed, though not so +much as the land. The warmed water expands, becomes thereby lighter, +and therefore continues to float upon the top. This upper layer of +water warms to some extent the air in contact with it, but it also +sends up a quantity of aqueous vapor, which being far lighter than +air, helps the latter to rise. Thus both from the land and from the +sea we have ascending currents established by the action of the sun. + +When they reach a certain elevation in the atmosphere, these currents +divide and flow, part towards the north and part towards the south; +while from the north and the south a flow of heavier and colder air +sets in to supply the place of the ascending warm air. + +Incessant circulation is thus established in the atmosphere. The +equatorial air and vapor flow above towards the north and south poles, +while the polar air flows below towards the equator. The two currents +of air thus established are called the upper and the lower trade +winds. + +But before the air returns from the poles great changes have occurred. +For the air as it quitted the equatorial regions was laden with +aqueous vapor, which could not subsist in the cold polar regions. It +is there precipitated, falling sometimes as rain, or more commonly as +snow. The land near the pole is covered with this snow, which gives +birth to vast glaciers. + +It is necessary that you should have a perfectly clear view of this +process, for great mistakes have been made regarding the manner in +which glaciers are related to the heat of the sun. + +It was supposed that if the sun's heat were diminished, greater +glaciers than those now existing would be produced. But the lessening +of the sun's heat would infallibly diminish the quantity of aqueous +vapor, and thus cut off the glaciers at their source. A brief +illustration will complete your knowledge here. + +In the process of ordinary distillation, the liquid to be distilled is +heated and converted into vapor in one vessel, and chilled and +reconverted into liquid in another. What has just been stated renders +it plain that the earth and its atmosphere constitute a vast +distilling apparatus in which the equatorial ocean plays the part of +the boiler, and the chill regions of the poles the part of the +condenser. In this process of distillation _heat_ plays quite as +necessary a part as _cold_, and before Bishop Heber could speak of +"Greenland's icy mountains," the equatorial ocean had to be warmed by +the sun. We shall have more to say upon this question afterwards. + +The heating of the tropical air by the sun is _indirect_. The solar +beams have scarcely any power to heat the air through which they pass; +but they heat the land and ocean, and these communicate their heat to +the air in contact with them. The air and vapor start upwards charged +with the heat thus communicated. + + +Tropical Rains. + +But long before the air and vapor from the equator reach the poles, +precipitation occurs. Wherever a humid warm wind mixes with a cold dry +one, rain falls. Indeed the heaviest rains occur at those places where +the sun is vertically overhead. We must enquire a little more closely +into their origin. + +Fill a bladder about two-thirds full of air at the sea level, and take +it to the summit of Mount Blanc. As you ascend, the bladder becomes +more and more distended; at the top of the mountain it is fully +distended, and has evidently to bear a pressure from within. Returning +to the sea level you find that the tightness disappears, the bladder +finally appearing as flaccid as at first. + +The reason is plain. At the sea level the air within the bladder has +to bear the pressure of the whole atmosphere, being thereby squeezed +into a comparatively small volume. In ascending the mountain, you +leave more and more of the atmosphere behind; the pressure becomes +less and less, and by its expansive force the air within the bladder +swells as the outside pressure is diminished. At the top of the +mountain the expansion is quite sufficient to render the bladder +tight, the pressure within being then actually greater than the +pressure without. By means of an air-pump we can show the expansion of +a balloon partly filled with air, when the external pressure has been +in part removed. + +But why do I dwell upon this? Simply to make plain to you that the +_unconfined air_, heated at the earth's surface, and ascending by its +lightness, must expand more and more the higher it rises in the +atmosphere. + +And now I have to introduce to you a new fact, towards the statement +of which I have been working for some time. It is this: _The ascending +air is chilled by its expansion_. Indeed this chilling is one source +of the coldness of the higher atmospheric regions. And now fix your +eye upon those mixed currents of air and aqueous vapor which rise from +the warm tropical ocean. They start with plenty of heat to preserve +the vapor as vapor; but as they rise they come into regions already +chilled, and they are still further chilled by their own expansion. +The consequence might be foreseen. The load of vapor is in great part +precipitated, dense clouds are formed, their particles coalesce to +rain-drops, which descend daily in gushes so profuse that the word +"torrential" is used to express the copiousness of the rainfall. I +could show you this chilling by expansion, and also the consequent +precipitation of clouds. + +Thus long before the air from the equator reaches the poles its vapor +is in great part removed from it, having redescended to the earth as +rain. Still a good quantity of the vapor is carried forward, which +yields hail, rain, and snow in northern and southern lands. + + +Mountain Condensers. + +To complete our view of the process of atmospheric precipitation we +must take into account the action of mountains. Imagine a south-west +wind blowing across the Atlantic towards Ireland. In its passage it +charges itself with aqueous vapor. In the south of Ireland it +encounters the mountains of Kerry: the highest of these is +Magillicuddy's Reeks, near Killarney. Now the lowest stratum of this +Atlantic wind is that which is most fully charged with vapor. When it +encounters the base of the Kerry Mountains it is tilted up and flows +bodily over them. Its load of vapor is therefore carried to a height, +it expands on reaching the height, it is chilled in consequence of +the expansion, and comes down in copious showers of rain. From this, +in fact, arises the luxuriant vegetation of Killarney; to this, +indeed, the lakes owe their water supply. The cold crests of the +mountains also aid in the work of condensation. + +Note the consequence. There is a town called Cahirciveen to the +south-west of Magillicuddy's Reeks, at which observations of the +rainfall have been made, and a good distance farther to the +north-east, right in the course of the south-west wind there is +another town, called Portarlington, at which observations of rainfall +have also been made. But before the wind reaches the latter station it +has passed over the mountains of Kerry and left a great portion of its +moisture behind it. What is the result? At Cahirciveen, as shown by +Dr. Lloyd, the rainfall amounts to fifty-nine inches in a year, while +at Portarlington it is only twenty-one inches. + +Again, you may sometimes descend from the Alps when the fall of rain +and snow is heavy and incessant, into Italy, and find the sky over the +plains of Lombardy blue and cloudless, the wind at the same time +_blowing over the plain towards the Alps_. Below the wind is hot +enough to keep its vapor in a perfectly transparent state; but it +meets the mountains, is tilted up, expanded, and chilled. The cold of +the higher summits also helps the chill. The consequence is that the +vapor is precipitated as rain or snow, thus producing bad weather upon +the heights, while the plains below, flooded with the same air, enjoy +the aspect of the unclouded summer sun. Clouds blowing _from_ the +Alps are also sometimes dissolved over the plains of Lombardy. + +In connection with the formation of clouds by mountains, one +particularly instructive effect may be here noticed. You frequently +see a streamer of cloud many hundred yards in length drawn out from an +Alpine peak. Its steadiness appears perfect, though a strong wind may +be blowing at the same time over the mountain head. Why is the cloud +not blown away? It _is_ blown away; its permanence is only apparent. +At one end it is incessantly dissolved; at the other end it is +incessantly renewed: supply and consumption being thus equalized, the +cloud appears as changeless as the mountain to which it seems to +cling. When the red sun of the evening shines upon these +cloud-streamers they resemble vast torches with their flames blown +through the air. + +Architecture of Snow. + +We now resemble persons who have climbed a difficult peak, and thereby +earned the enjoyment of a wide prospect. Having made ourselves masters +of the conditions necessary to the production of mountain snow, we are +able to take a comprehensive and intelligent view of the phenomena of +glaciers. + +[Illustration: SNOW CRYSTALS.] + +A few words are still necessary as to the formation of snow. The +molecules and atoms of all substances, when allowed free play, build +themselves into definite and, for the most part, beautiful forms +called crystals. Iron, copper, gold, silver, lead, sulphur, when +melted and permitted to cool gradually, all show this crystallizing +power. The metal bismuth shows it in a particularly striking manner, +and when properly fused and solidified, self-built crystals of great +size and beauty are formed of this metal. + +[Illustration: SNOW-STAR.] + +[Illustration: SNOW-STAR.] + +If you dissolve salt-petre in water, and allow the solution to +evaporate slowly, you may obtain large crystals, for no portion of the +salt is converted into vapor. The water of our atmosphere is fresh +though it is derived from the salt sea. Sugar dissolved in water, and +permitted to evaporate, yields crystals of sugar-candy. Alum readily +crystallizes in the same way. Flints dissolved, as they sometimes are +in nature, and permitted to crystallize, yield the prisms and pyramids +of rock crystal. Chalk dissolved and crystallized yields Iceland spar. +The diamond is crystallized carbon. All our precious stones, the +ruby, sapphire, beryl, topaz, emerald, are all examples of this +crystallizing power. + +[Illustration: SNOW-STAR.] + +You have heard of the force of gravitation, and you know that it +consists of an attraction of every particle of matter for every other +particle. You know that planets and moons are held in their orbits by +this attraction. But gravitation is a very simple affair compared to +the force, or rather forces, of crystallization. For here the ultimate +particles of matter, inconceivably small as they are, show themselves +possessed of attractive and repellent poles, by the mutual action of +which the shape and structure of the crystal are determined. In the +solid condition the attracting poles are rigidly locked together; but +if sufficient heat be applied the bond of union is dissolved, and in +the state of fusion the poles are pushed so far asunder as to be +practically out of each other's range. The natural tendency of the +molecules to build themselves together is thus neutralized. + +This is the case with water, which as a liquid is to all appearance +formless. When sufficiently cooled the molecules are brought within +the play of the crystallizing force, and they then arrange themselves +in forms of indescribable beauty. When snow is produced in calm air, +the icy particles build themselves into beautiful stellar shapes, each +star possessing six rays. There is no deviation from this type, though +in other respects the appearances of the snow-stars are infinitely +various. In the polar regions these exquisite forms were observed by +Dr. Scoresby, who gave numerous drawings of them. I have observed them +in mid-winter filling the air, and loading the slopes of the Alps. But +in England they are also to be seen, and no words of mine could convey +so vivid an impression of their beauty as the annexed drawings of a +few of them, executed at Greenwich by Mr. Glaisher. + +[Illustration: SNOW-STAR.] + +It is worth pausing to think what wonderful work is going on in the +atmosphere during the formation and descent of every snow-shower; what +building power is brought into play! and how imperfect seem the +productions of human minds and hands when compared with those formed +by the blind forces of nature! + +But who ventures to call the forces of nature blind? In reality, when +we speak thus we are describing our own condition. The blindness is +ours; and what we really ought to say, and to confess, is that our +powers are absolutely unable to comprehend either the origin or the +end of the operations of nature. + +But while we thus acknowledge our limits, there is also reason for +wonder at the extent to which science has mastered the system of +nature. From age to age, and from generation to generation, fact has +been added to fact, and law to law, the true method and order of the +Universe being thereby more and more revealed. In doing this science +has encountered and overthrown various forms of superstition and +deceit, of credulity and imposture. But the world continually produces +weak persons and wicked persons; and as long as they continue to exist +side by side, as they do in this our day, very debasing beliefs will +also continue to infest the world. + + +Atomic Poles. + +"What did I mean when, a few moments ago I spoke of attracting and +repellent poles?" Let me try to answer this question. You know that +astronomers and geographers speak of the earth's poles, and you have +also heard of magnetic poles, the poles of a magnet being the points +at which the attraction and repulsion of the magnet are as it were +concentrated. + +Every magnet possesses two such poles; and if iron filings be +scattered over a magnet, each particle becomes also endowed with two +poles. Suppose such particles devoid of weight and floating in our +atmosphere, what must occur when they come near each other? Manifestly +the repellent poles will retreat from each other, while the attractive +poles will approach and finally lock themselves together. And +supposing the particles, instead of a single pair, to possess several +pairs of poles arranged at definite points over their surfaces; you +can then picture them, in obedience to their mutual attractions and +repulsions, building themselves together to form masses of definite +shape and structure. + +Imagine the molecules of water in calm cold air to be gifted with +poles of this description, which compel the particles to lay +themselves together in a definite order, and you have before your +mind's eye the unseen architecture which finally produces the visible +and beautiful crystals of the snow. Thus our first notions and +conceptions of poles are obtained from the sight of our eyes in +looking at the effects of magnetism; and we then transfer these +notions and conceptions to particles which no eye has ever seen. The +power by which we thus picture to ourselves effects beyond the range +of the senses is what philosophers call the Imagination, and in the +effort of the mind to seize upon the unseen architecture of crystals, +we have an example of the "scientific use" of this faculty. Without +imagination we might have _critical_ power, but not _creative_ power +in science. + + +Architecture of Lake Ice. + +We have thus made ourselves acquainted with the beautiful snow-flowers +self-constructed by the molecules of water in calm, cold air. Do the +molecules show this architectural power when ordinary water is frozen? +What, for example, is the structure of the ice over which we skate in +winter? Quite as wonderful as the flowers of the snow. The observation +is rare, if not new, but I have seen in water slowly freezing +six-rayed ice-stars formed, and floating free on the surface. A +six-rayed star, moreover, is typical of the construction of all our +lake ice. It is built up of such forms wonderfully interlaced. + +Take a slab of lake ice and place it in the path of a concentrated +sunbeam. Watch the track of the beam through the ice. Part of the beam +is stopped, part of it goes through; the former produces internal +liquefaction, the latter has no effect whatever upon the ice. But the +liquefaction is not uniformly diffused. From separate spots of the ice +little shining points are seen to sparkle forth. Every one of those +points is surrounded by a beautiful liquid flower with six petals. + +Ice and water are so optically alike that unless the light fall +properly upon these flowers you cannot see them. But what is the +central spot? A vacuum. Ice swims on water because, bulk for bulk, it +is lighter than water; so that when ice is melted it shrinks in size. +Can the liquid flowers then occupy the whole space of the ice melted? +Plainly no. A little empty space is formed with the flowers, and this +space, or rather its surface, shines in the sun with the lustre of +burnished silver. + +In all cases the flowers are formed parallel to the surface of +freezing. They are formed when the sun shines upon the ice of every +lake; sometimes in myriads, and so small as to require a magnifying +glass to see them. They are always attainable, but their beauty is +often marred by internal defects of the ice. Every one portion of the +same piece of ice may show them exquisitely, while a second portion +shows them imperfectly. + +Annexed is a very imperfect sketch of these beautiful figures. + +Here we have a reversal of the process of crystallization. The +searching solar beam is delicate enough to take the molecules down +without deranging the order of their architecture. Try the experiment +for yourself with a pocket-lens on a sunny day. You will not find the +flowers confused; they all lie parallel to the surface of freezing. In +this exquisite way every bit of the ice over which our skaters glide +in winter is put together. + +I said that a portion of the sunbeam was stopped by the ice and +liquefied it. What is this portion? The dark heat of the sun. The +great body of the light waves and even a portion of the dark ones, +pass through the ice without losing any of their heating power. When +properly concentrated on combustible bodies, even after having passed +through the ice, their burning power becomes manifest. + +[Illustration: LIQUID FLOWERS IN LAKE ICE.] + +And the ice itself may be employed to concentrate them. With an +ice-lens in the polar regions Dr. Scoresby has often concentrated the +sun's rays so as to make them burn wood, fire gunpowder, and melt +lead; thus proving that the heating power is retained by the rays, +even after they have passed through so cold a substance. + +By rendering the rays of the electric lamp parallel, and then sending +them through a lens of ice, we obtain all the effects which Dr. +Scoresby obtained with the rays of the sun. + +[Illustration] + + + + +THE ORGANIC WORLD + +(FROM THE ELEMENTS OF SCIENCE.) + +BY ST. GEORGE MIVART F.R.S. + + +The number of all the various kinds of living creatures is so enormous +that it would be impossible to study them profitably, were they not +classified in an orderly manner. Therefore the whole mass has been +divided, in the first place, into two supreme groups, fancifully +termed kingdoms--the "animal kingdom" and the "vegetal kingdom." Each +of these is subdivided into an orderly series of subordinate groups, +successively contained one within the other, and named sub-kingdoms, +classes, orders, families, genera and species. The lowest group but +one is the "genus," which contains one or more different kinds termed +"species," as e.g., the species "wood anemone" and the species "blue +titmouse." The lowest group of all--a species--may be said to consist +of individuals which differ from each other only by trifling +characters, such as characters due to difference of sex, while their +peculiar organization is faithfully reproduced by generation as a +whole, though small individual differences exist in all cases. + +The vegetal, or vegetable, kingdom, consists of the great mass of +flowering plants, many of which, however, have such inconspicuous +flowers that they are mistakenly regarded as flowerless, as is often +the case with the grasses, the pines, and the yews. Another mass, or +sub-kingdom, of plants consists of the really flowerless plants, such +as the ferns, horsetails (Fig. 1), lycopods, and mosses. Sea and +fresh-water weeds (_algæ_), and mushrooms, or "moulds," of all kinds +(_fungi_), amongst which are the now famous "bacteria," constitute a +third and lowest set of plants. + +[Illustration: FIG. 1. HORSE-TAIL (_Equisetum drummondii_).] + +The animal kingdom consists, first, of a sub-kingdom of animals which +possess a spinal column, or backbone, and which are known as +vertebrate animals. Such are all beasts, birds, reptiles, and fishes. +There are also a variety of remotely allied marine organisms known as +tunicates, sea-squirts, or ascidians (Fig. 2). There is, further, an +immense group of arthropods, consisting of all insects, crab-like +creatures, hundred-legs and their allies, with spiders, scorpions, +tics and mites. We have also the sub-kingdom of shell-fish or +molluscs, including cuttle-fishes, snails, whelks, limpets, the +oyster, and a multitude of allied forms. A multitudinous sub-kingdom of +worms also exists, as well as another of star-fishes and their +congeners. There is yet another of zoophytes, or polyps, and another +of sponges, and, finally, we have a sub-kingdom of minute creatures, +or animalculæ, of very varied forms, which may make up the sub-kingdom +of _Protozoa_, consisting of animals which are mostly unicellular. + +[Illustration: FIG. 2. A TUNICATE (_Ascidia_).] + +Multitudinous and varied as are the creatures which compose this +immense organic world, they nevertheless exhibit a very remarkable +uniformity of composition in their essential structure. Every living +creature from a man to a mushroom, or even to the smallest animalcule +or unicellular plant is always partly fluid, but never entirely so. +Every living creature also consists in part (and that part is the most +active living part) of a soft, viscid, transparent, colorless +substance, termed protoplasm, which can be resolved into the four +elements, oxygen, hydrogen, nitrogen and carbon. Besides these four +elements, living organisms commonly contain sulphur, phosphorus, +chlorine, potassium, sodium, calcium, magnesium and iron. + +In the fact that living creatures always consist of the four elements, +oxygen, hydrogen, nitrogen and carbon, we have a fundamental character +whereby the organic and inorganic (or non-living) worlds are to be +distinguished, for as we have seen, inorganic bodies, instead of being +thus uniformly constituted, may consist of the most diverse elements +and sometimes of but two or even of only one. + +Again, many minerals, such as crystals, are bounded by plain surfaces, +and, with very few exceptions (spathic and hematite iron and dolomite +are such exceptions) none are bounded by curved lines and surfaces, +while living organisms are bounded by such lines and surfaces. + +Yet, again, if a crystal be cut through, its internal structure will +be seen to be similar throughout. But if the body of any living +creature be divided, it will, at the very least, be seen to consist of +a variety of minute distinct particles, called "granules," variously +distributed throughout its interior. + +All organisms consist either--as do the simplest, mostly microscopic, +plants and animals--of a single minute mass of protoplasm, or of a +few, or of many, or of an enormous aggregation of such before-mentioned +particles, each of which is one of those bodies named a "cell" (Fig. +3). Cells may, or may not, be enclosed in an investing coat or +"cell-wall." Every cell generally contains within it a denser, +normally spheroidal, body known as the nucleus. + +Now protoplasm is a very unstable substance--as we have seen many +substances are whereof nitrogen is a component part--and it possesses +active properties which are not present in the non-living, or +inorganic world. In the latter, differences of temperature will +produce motion in the shape of "currents," as we have seen with +respect to masses of air and water. But in a portion of protoplasm, +an internal circulation of currents in definite lines will establish +itself from other causes. + +Inorganic bodies, as we have seen, will expand with heat, as they may +also do from imbibing moisture; but living protoplasm has an +apparently spontaneous power of contraction and expansion under +certain external conditions which do not occasion such movements in +inorganic matter. + +[Illustration: FIG. 3. CELL FROM A SALAMANDER. _n_, nucleus; _n'_, +nucleolus embedded in the network of chromatin threads; _k_, network +of the cell external to the nucleus; _a_, attraction-sphere or +archoplasm containing minute bodies called centrosomes; _cl_, membrane +enclosing the cell externally, _nl_, membrane surrounding the nucleus; +_c_, centrosomes.] + +Under favoring conditions, protoplasm has a power of performing +chemical changes, which result in producing heat far more gently and +continuously than it is produced by the combustion of inorganic +bodies. Thus it is that the heat is produced which makes its presence +evident to us in what we call "warm-blooded animals," the most +warm-blooded of all being birds. + +Protoplasm has also the wonderful power of transforming certain +adjacent substances into material like itself--into its own +substance--and so, in a sense, creating a new material. Thus it is +that organisms have the power to nourish themselves and grow. An +animal would vainly swallow the most nourishing food if the ultimate, +protoplasmic particles of its body had not this power of +"transforming" suitable substances brought near them in ways to be +hereinafter noticed. + +Without that, no organism could ever "grow." The growth of organisms +is utterly different from the increase in size of inorganic bodies. +Crystals, as we have seen, grow merely by external increment; but +organisms grow by an increment which takes place in the very innermost +substance of the tissues which compose their bodies, and the innermost +substance of the cells which compose such tissues; this peculiar form +of growth is termed _intussusception_. + +Protoplasm, after thus augmenting its mass, has a further power of +spontaneous division, whereby the mass of the entire organism whereof +such protoplasm forms a part, is augmented and so growth is brought +about. + +The small particles of protoplasm which constitute "cells" are far +indeed from being structureless. Besides the nucleus already mentioned +there is a delicate network of threads of a substance called +_chromatin_ within it, and another network permeating the fluid of the +cell substance, which invest the nucleus often with further +complications. These networks generally perform (or undergo) a most +complex series of changes every time a cell spontaneously divides. In +certain cases, however, it appears that the nucleus divides into two +in a more simple fashion, the rest of the cell contents subsequently +dividing--each half enclosing one part of the previously divided +nucleus. It is by a continued process of cell division that the +complex structures of the most complex organisms is brought about. + +The division of a cell, or particle of protoplasm, is indeed a +necessary consequence of its complete nutrition. + +For new material can only be absorbed by its surface. But as the cell +grows, the proportion borne by its surface to its mass, continually +decreases; therefore this surface must soon be too small to take in +nourishment enough, and the particle, or cell, must therefore either +die or divide. By dividing, its parts can continue the nutritive +process till their surface, in turn, becomes insufficient, when they +must divide again, and so on. Thus the term "feeding" has two senses. +"To feed a horse," ordinarily means to give it a certain quantity of +hay, oats or what not; and such indeed is one kind of feeding. But +obviously, if the nourishment so taken could not get from the stomach +and intestines into the ultimate particles and cells of the horse's +body, the horse could not be nourished, and still less could it grow. +It is this latter process, called assimilation, which is the real and +essential process of feeding, to which the process ordinarily so +called is but introductory. + +Protoplasm has also the power of forming and ejecting from its own +substance, other substances which it has made, but which are of a +different nature to its own. This function, as before said, is termed +secretion; and we know the liver secretes bile, and that the cow's +udder secretes milk. + +Here again we have an external and an internal process. The milk is +drawn forth from a receptacle, the udder, into which it finds its way, +and so, in a superficial sense, it may be called an organ of +secretion. Nevertheless the true internal secretion takes place in +the innermost substance of the cells or particles of protoplasm, of +the milk-land, which particles really form that liquid. + +But every living creature consists at first entirely of a particle of +protoplasm. Therefore every other kind of substance which may be found +in every kind of plant or animal, must have been formed through it, +and be, in fact, a secretion from protoplasm. Such is the rosy cheek +of an apple, or of a maiden, the luscious juice of the peach, the +produce of the castor-oil plant, the baleen that lines the whale's +enormous jaws, as well as that softest product, the fur of the +chinchilla. Indeed, every particle of protoplasm requires, in order +that it may live, a continuous process of exchange. It needs to be +continuously first built up by food, and then broken down by +discharging what is no longer needful for its healthy existence. Thus +the life of every organism is a life of almost incessant change, not +only in its being as a whole, but in that of all its protoplasmic +particles also. + +[Illustration: FIG. 4. AMOEBA SHOWN IN TWO OF THE MANY IRREGULAR +SHAPES IT ASSUMES. _(After Howes_.) + +The clear space within it is a contractile vesicle. The dark body is +the nucleus. In the right-hand figure there is shown a particle of +food, passing through the external surface.] + + +Prominent among such processes is that of an interchange of gases +between the living being and its environment. This process consists in +an absorption of oxygen and a giving-out of carbonic acid, which +exchange is termed respiration. + +Lastly, protoplasm has a power of motion when appropriately acted on. +It will then contract or expand its shape by alternate protrusions and +retractions of parts of its substance. These movements are termed +amoebiform, because they quite resemble the movements of a small +animalcule which is named amoeba. (See Fig. 4.) + +Such is the ultimate structure, and such are the fundamental +activities or functions of living organisms, as far as they can here +be described, from the lowest animalcule and unicellular plant, up to +the most complex organisms and the body of man himself. + +[Illustration] + + + + +INHABITANTS OF MY POOL + +(FROM MAGIC GLASSES.) + +BY ARABELLA B. BUCKLEY. + + +The pool lies in a deep hollow among a group of rocks and boulders, +close to the entrance of the cove, which can only be entered at low +water; it does not measure more than two feet across, so that you can +step over it, if you take care not to slip on the masses of green and +brown seaweed growing over the rocks on its sides, as I have done many +a time when collecting specimens for our salt-water aquarium. I find +now the only way is to lie flat down on the rock, so that my hands and +eyes are free to observe and handle, and then, bringing my eye down to +the edge of the pool, to lift the seaweeds and let the sunlight enter +into the chinks and crannies. In this way I can catch sight of many a +small being either on the seaweed or the rocky ledges, and even +creatures transparent as glass become visible by the thin outline +gleaming in the sunlight. Then I pluck a piece of seaweed, or chip off +a fragment of rock with a sharp-edged collecting knife, bringing away +the specimen uninjured upon it, and place it carefully in its own +separate bottle to be carried home alive and well. + +Now though this little pool and I are old friends, I find new +treasures in it almost every time I go, for it is almost as full of +living things as the heavens are of stars, and the tide as it comes +and goes brings many a mother there to find a safe home for her little +ones, and many a waif and stray to seek shelter from the troublous +life of the open ocean. + +You will perhaps find it difficult to believe that in this rock-bound +basin there can be millions of living creatures hidden away among the +fine feathery weeds; yet so it is. Not that they are always the same. +At one time it may be the home of myriads of infant crabs, not an +eighth of an inch long, another of baby sea-urchins only visible to +the naked eye as minute spots in the water, at another of young +jelly-fish growing on their tiny stalks, and splitting off one by one +as transparent bells to float away with the rising tide. Or it may be +that the whelk has chosen this quiet nook to deposit her leathery +eggs; or young barnacles, periwinkles, and limpets are growing up +among the green and brown tangles, while the far-sailing velella and +the stay-at-home sea-squirts, together with a variety of other +sea-animals, find a nursery and shelter in their youth in this quiet +harbor of rest. + +And besides these casual visitors there are numberless creatures which +have lived and multiplied there, ever since I first visited the pool. +Tender red, olive-colored, and green seaweeds, stony corallines, and +acorn-barnacles lining the floor, sea-anemones clinging to the sides, +sponges tiny and many-colored hiding under the ledges, and limpets and +mussels wedged in the cracks. These can be easily seen with the naked +eye, but they are not the most numerous inhabitants; for these we +must search with a magnifying glass, which will reveal to us wonderful +fairy-forms, delicate crystal vases with tiny creatures in them whose +transparent lashes make whirlpools in the water, living crystal bells +so tiny that whole branches of them look only like a fringe of hair, +jelly globes rising and falling in the water, patches of living jelly +clinging to the rocky sides of the pool, and a hundred other forms, +some so minute that you must examine the fine sand in which they lie +under a powerful microscope before you can even guess that they are +there. + +[Illustration: FIG. 1. GROUP OF SEAWEEDS. + +(Natural size.) + +1, _Ulva Linza._ 2, _Sphacelaria filicina._ 3, _Polysiphonia +urceolata._ 4, _Corallina officinalis._] + +So it has proved a rich hunting-ground, where summer and winter, +spring and autumn, I find some form to put under my magic glass. There +I can watch it for weeks growing and multiplying under my care; moved +only from the aquarium, where I keep it supplied with healthy +sea-water, to the tiny transparent trough in which I place it for a +few hours to see the changes it has undergone. I could tell you +endless tales of transformations in these tiny lives, but I want +to-day to show you a few of my friends, most of which I brought +yesterday fresh from the pool, and have prepared for you to examine. + +[Illustration: FIG. 2. _Ulva lactuca_, A GREEN-SEAWEED, GREATLY +MAGNIFIED TO SHOW STRUCTURE. (_After Orested)._ + +s, Spores in the cells, _ss_, Spores swimming out. _h_, Holes through +which spores have escaped.] + +Let us begin with seaweeds. I have said that there are three leading +colors in my pool--green, olive, and red--and these tints mark roughly +three kinds of weed, though they occur in an endless variety of +shapes. Here is a piece of the beautiful pale green seaweed, called +the Laver or Sea-Lettuce, _Ulva Linza_ (1, Fig. 1),[1] which grows in +long ribbons in a sunny nook in the water. I have placed under the +first microscope a piece of this weed which is just sending out young +seaweeds in the shape of tiny cells, with lashes very like those we +saw coming from the moss-flower, and I have pressed them in the +position in which they would naturally leave the plant. You will also +see on this side several cells in which these tiny spores are forming, +ready to burst out and swim; for this green weed is merely a +collection of cells, like the single-celled plants on land. Each cell +can work as a separate plant; it feeds, grows, and can send out its +own young spores. + +[Footnote 1: The slice given in Fig. 2 is from a broader-leaved form, +_U. lactuca_, because this species, being composed of only one layer +of cells, is better seen. _Ulva Linza_ is composed of two layers of +cells.] + +This deep olive-green feathery weed (2, Fig. 1), of which a piece is +magnified under the next microscope (2, Fig. 3), is very different. It +is a higher plant, and works harder for its living, using the darker +rays of sunlight which penetrate into shady parts of the pool. So it +comes to pass that its cells divide the work. Those of the feathery +threads make the food, while others, growing on short stalks on the +shafts of the feather, make and send out the young spores. + +Lastly, the lovely red threadlike weeds, such as this _Polysiphonia +urceolata_ (3, Fig. 1), carry actual urns on their stems like those of +mosses. In fact, the history of these urns (see 3, Fig. 3), is much +the same in the two classes of plants, only that instead of the urn +being pushed up on a thin stalk as in the moss, it remains on the +seaweed close down to the stem, when it grows out of the plant-egg, +and the tiny plant is shut in till the spores are ready to swim out. + +[Illustration: FIG. 3. THREE SEAWEEDS OF FIG. 1 MUCH MAGNIFIED TO SHOW +FRUITS. (_Harvey._) + +2, _Sphacelaria filicina._ 3, _Polysiphonia urceolata._ 4, _Corallina +officinalis._] + +The stony corallines (4, Figs. 1 and 3), which build so much carbonate +of lime into their stems, are near relations of the red seaweeds. +There are plenty of them in my pool. Some of them, of a deep purple +color, grow upright in stiff groups about three or four inches high; +and others, which form crusts over the stones and weeds, are a pale +rose color; but both kinds, when the plant dies, leaving the stony +skeleton (1, Fig. 4), are a pure white, and used to be mistaken for +corals. They belong to the same order of plants as the red weeds, +which all live in shady nooks in the pools, and are the highest of +their race. + +[Illustration: FIG. 4. CORALLINE AND SERTULARIA, TO SHOW LIKENESS +BETWEEN THE ANIMAL SERTULARIA AND THE PLANT CORALLINE. + +1, _Corallina officinalis._ 2, _Sertularia filicula._] + +My pool is full of different forms of these four weeds. The green +ribbons float on the surface rooted to the sides of the pool, and, as +the sun shines upon it, the glittering bubbles rising from them show +that they are working up food out of the air in the water, and giving +off oxygen. The brown weeds lie chiefly under the shelves of rocks, +for they can manage with less sunlight, and use the darker rays which +pass by the green weeds; and last of all, the red weeds and +corallines, small and delicate in form, line the bottom of the pool in +its darkest nooks. + +And now if I hand round two specimens,--one a coralline, and the other +something you do not yet know,--I am sure you will say at first sight +that they belong to the same family, and, in fact, if you buy at the +seaside a group of seaweeds gummed on paper, you will most likely get +both these among them. Yet the truth is; that while the coralline (1, +Fig. 4) is a plant, the other specimen (2), which is called +_Sertularia filicula_, is an animal. + +This special sertularian grows up right in my pool on stones or often +on seaweeds, but I have here (Fig. 5) another and much smaller one +which lives literally in millions hanging its cups downwards. I find +it not only under the narrow ledges of the pool sheltered by the +seaweed, but forming a fringe along all the rocks on each side of the +cove near to low-water mark, and for a long time I passed it by +thinking it was of no interest. But I have long since given up +thinking this of anything, especially in my pool, for my magic glass +has taught me that there is not even a living speck which does not +open out into something marvellous and beautiful. So I chipped off a +small piece of rock and brought the fringe home, and found, when I +hung it up in clear sea-water as I have done over this glass trough +(Fig. 5) and looked at it through the lens, that each thread of the +dense fringe, in itself not a quarter of an inch deep, turns out to be +a tiny sertularian with at least twenty mouths. You can see this with +your pocket lens even as it hangs here, and when you have examined it +you can by and by take off one thread and put it carefully in the +trough. I promise you a sight of the most beautiful little beings +which exist in nature. + +[Illustration: FIG. 5. _Sertularia tenella_, HANGING FROM A SPLINT OF +ROCK OVER A WATER TROUGH. ALSO PIECE ENLARGED TO SHOW THE ANIMAL +PROTRUDING.] + +Come and look at it. It is a horny-branched stem with a double row of +tiny cups all along each side. Out of these cups there appear a row of +tiny cups all along each side (see Fig. 5), Out of these cups there +appear from time to time sixteen minute transparent tentacles as fine +as spun glass, which wave about in the water. If you shake the glass a +little, in an instant each crystal star vanishes into its cup, to come +out again a few minutes later; so that now here, now there, the +delicate animal-flowers spread out on each side of the stem, and the +tree is covered with moving beings. These tentacles are feelers, which +lash food into a mouth and stomach in each cup, where it is digested +and passed, through a hole in the bottom, along a jelly thread which +runs down the stem and joins all the mouths together. In this way the +food is distributed all over the tree, which is, in fact, one animal +with many feeding-cups. Some day I will show you one of these cups +with the tentacles stretched out and mounted on a slide, so that you +can examine a tentacle with a very strong magnifying power. You will +then see that it is dotted over with cells, in which are coiled fine +threads. The animal uses these threads to paralyze the creatures on +which it feeds, for at the base of each thread there is a poison +gland. + +In the larger Sertularia the whole branched tree is connected by jelly +threads, running through the stem, and all the thousands of mouths are +spread out in the water. One large form called _Sertularia cupressina_ +grows sometimes three feet high and bears as many as a hundred +thousand cups, with living mouths, on its branches. + +The next of my minute friends I can only show to the class in a +diagram, but you will see it under the fourth microscope by and by. I +had great trouble in finding it yesterday, though I know its haunts +upon the green weed, for it is so minute and transparent that even +when the weed is in a trough a magnifying-glass will scarcely detect +it. And I must warn you that if you want to know any of the minute +creatures we are studying, you must visit one place constantly. You +may in a casual way find many of them on seaweed, or in the damp ooze +and mud, but it will be by chance only; to look for them with any +certainty you must take trouble in making their acquaintance. + +[Illustration: FIG. 6. _Thuricolla folliculata_ and _Chilomonas +amygdalum_. (_Saville Kent_.) + +1, _Thuricolla_ erect. 2, Retracted. 3, Dividing. 4, _Chilomonas +amygdalum. hc,_ Horny carapace, _cv_, Contractile vesicle. _v_ Closing +valves.] + +Turning then to the diagram (Fig. 6) I will describe it as I hope you +will see it under the microscope--a curious, tiny, perfectly +transparent open-mouthed vase standing upright on the weed, and having +an equally transparent being rising up in it and waving its tiny +lashes in the water. This is really all one animal, the vase _hc_ +being the horny covering or carapace of the body, which last stands up +like a tube in the centre. If you watch carefully, you may even see +the minute atoms of food twisting round inside the tube until they are +digested, after they have been swept in at the wide open mouth by the +whirling lashes. You will see this more clearly if you put a little +rice-flour, very minutely powdered and colored by carmine, into the +water; for you can trace these red atoms into some round spaces called +_vacuoles_ which are dotted over the body of the animal, and are +really globules of watery fluid in which the food is probably partly +digested. + +You will notice, however, one round clear space _(cv)_ into which they +do not go, and after a time you will be able to observe that this +round spot closes up or contracts very quickly, and then expands again +very slowly. As it expands it fills with a clear fluid, and +naturalists have not yet decided exactly what work it does. It may +serve the animal either for breathing, or as a very simple heart, +making the fluids circulate in the tube. The next interesting point +about this little being is the way it retreats into its sheltering +vase. Even while you are watching, it is quite likely it may all at +once draw itself down to the bottom as in No. 2, and folding down the +valves _w_ of horny teeth which grow on each side, shut itself in from +some fancied danger. Another very curious point is that, besides +sending forth young ones, these creatures multiply by dividing in two +(see No. 3, Fig. 6), each one closing its own part of the vase into a +new home. + +There are hundreds of these Infusoria, as they are called, in my pond, +some with vases, some without, some fixed to weeds and stones, others +swimming about freely. Even in the water-trough in which this +Thuricolla stands, I saw several smaller forms, and the next +microscope has a trough filled with the minutest form of all, called a +Monad. These are so small that two thousand of them could lie side by +side in an inch; that is, if you could make them lie at all, for they +are the most restless little beings, darting hither and thither, +scarcely even halting except to turn back. And yet though there are so +many of them, and as far as we know they have no organs of sight, they +never run up against each other, but glide past more cleverly than any +clear-sighted fish. These creatures are mostly to be found among +decaying seaweed, and though they are so tiny, you can still see +distinctly the clear space contracting and expanding within them. + +[Illustration: FIG. 7. LIVING DIATOMS. + +_a, Cocconema lanceolatum. b, Bacillaria paradoxa. c, Gomphonema +marinum. d, Diatoma hyalina_.] + +But if there are so many thousands of mouths to feed, on the tree-like +Sertulariæ as well as in all these Infusoria, where does the food come +from? Partly from the numerous atoms of decaying life all around, and +the minute eggs of animals and spores of plants; but besides these, +the pool is full of minute living plants--small jelly masses with +solid coats of flint which are moulded into most lovely shapes. Plants +formed of jelly and flint! You will think I am joking, but I am not. +These plants, called Diatoms, which live both in salt and fresh water, +are single cells feeding and growing just like those we took from the +water-butt, only that instead of a soft covering they build up a +flinty skeleton. They are so small, that many of them must be +magnified to fifty times their real size before you can even see them +distinctly. Yet the skeletons of these almost invisible plants are +carved and chiselled in the most delicate patterns. I showed you a +group of these in our lecture on magic glasses, and now I have brought +a few living ones that we may learn to know them. The diagram (Fig. 7) +shows the chief forms you will see on the different slides. + +The first one, _Sacillaria paradoxa_ (_b_, Fig. 7), looks like a +number of rods clinging one to another in a string, but each one of +these is a single-celled plant with a jelly cell surrounding the +flinty skeleton. You will see that they move to and fro over each +other in the water. + +The next two forms, _a_ and _c_, look much more like plants, for the +cells arrange themselves on a jelly stem, which by and by disappears, +leaving only the separate flint skeletons. The last form, _d_, is +something midway between the other forms, the separate cells hang on +to each other and also on to a straight jelly stem. + +[Illustration: FIG. 8. A DIATOM (_Diatoma vulgare_) GROWING. + +_a, b,_ Flint skeleton inside the jelly-cell. _a, c_ and _d, b_, Two +flint skeletons formed by new valves, _c_ and _d_, forming within the +first skeleton.] + +Another species of Diatoma (Fig. 8) called _Diatoma vulgare_, is a +very simple and common form, and will help to explain how these plants +grow. The two flinty valves _a, b_ inside the cell are not quite the +same size; the older one _a_ is larger than the younger one _b_ and +fits over it like the cover of a pill-box. As the plant grows, the +cell enlarges and forms two more valves, one _c_ fitting into the +cover _a_, so as to make a complete box _ac_, and a second, _d_, back +to back with _c_, fitting into the valve _b_, and making another +complete _bd_. This goes on very rapidly, and in this plant each new +cell separates as it is formed, and the free diatoms move about quite +actively in the water. + +If you consider for a moment, you will see that, as the new valves +always fit into the old ones, each must be smaller than the last, and +so there comes a time when the valves have become too small to go on +increasing. Then the plant must begin afresh. So the two halves of the +last cell open, and throwing out their flinty skeletons, cover +themselves with a thin jelly layer, and form a new cell which grows +larger than any of the old ones. These, which are spore-cells, then +form flinty valves inside, and the whole thing begins again. + +Now, though the plants themselves die, or become the food of minute +animals, the flinty skeletons are not destroyed, but go on +accumulating in the waters of the ponds, lakes, rivers, and seas, all +over the world. Untold millions have no doubt crumbled to dust and +gone back into the waters, but untold millions also have survived. The +towns of Berlin in Europe and of Richmond in the United States are +actually built upon ground called "infusorial earth," composed almost +entirely of valves of these minute diatoms which have accumulated to a +thickness of more than eighty feet! Those under Berlin are fresh-water +forms, and must have lived in a lake, while those of Richmond belong +to salt-water forms. Every inch of the ground under those cities +represents thousands and thousands of living plants which flourished +in ages long gone by, and were no larger than those you will see +presently under the microscope. + +These are a very few of the microscopic inhabitants of my pond, but, +as you will confuse them if I show you too many, we will conclude with +two rather larger specimens, and examine them carefully. The first, +called the Cydippe, is a lovely, transparent living ball, which I want +to explain to you because it is so wondrously beautiful. The second, +the Sea-mat or Flustra, looks like a crumpled drab-colored seaweed, +but is really composed of many thousands of grottos, the homes of tiny +sea-animals. + +[Illustration: FIG. 9. _Cydippe Pileus_. + +1, Animal with tentacles _t_, bearing small tendrils _t'_. 2, Body of +animal enlarged. _m_, Mouth. _c_, Digestive cavity. _s_, Sac into +which the tentacles are withdrawn. _p_, Bands with comb-like plates. +3, Portion of a band enlarged to show the moving plates _p_.] + +Let us take the Cydippe first (1, Fig. 9). I have six here, each in a +separate tumbler, and could have brought many more, for when I dipped +my net in the pool yesterday such numbers were caught in it that I +believe the retreating tide must just have left a shoal behind. Put a +tumbler on the desk in front of you, and if the light falls well upon +it you will see a transparent ball about the size of a large pea +marked with eight bright bands, which begin at the lower end of the +ball and reach nearly to the top, dividing the outside into sections +like the ribs of a melon. The creature is so perfectly transparent +that you can count all the eight bands. + +At the top of the ball is a slight bulge which is the mouth (_m_ 2, +Fig. 9), and from it, inside the ball hangs a long bag or stomach, +which opens below into a cavity, from which two canals branch out, one +on each side, and these divide again into four canals which go one +into each of the tubes running down the bands. From this cavity the +food, which is digested in the stomach, is carried by the canals all +over the body. The smaller tubes which branch out of these canals +cannot be seen clearly without a very strong lens, and the only other +parts you can discern in this transparent ball are two long sacs on +each side of the lower end. These are the tentacle sacs, in which are +coiled up the tentacles, which we shall describe presently. Lastly you +can notice that the bands outside the globe are broader in the middle +than at the ends, and are striped across by a number of ridges. + +In moving the tumblers the water has naturally been shaken, and the +creature being alarmed will probably at first remain motionless. But +very soon it will begin to play in the water, rising and falling, and +swimming gracefully from side to side. Now you will notice a curious +effect, for the bands will glitter and become tinged with prismatic +colors, till, as it moves more and more rapidly these colors, +reflected in the jelly, seem to tinge the whole ball with colors like +those on a soap-bubble, while from the two sacs below come forth two +long transparent threads like spun glass. At first these appear to be +simple threads, but as they gradually open out to about four or five +inches, smaller threads uncoil on each side of the line till there are +about fifty on each line. These short tendrils are never still for +long; as the main threads wave to and fro, some of the shorter ones +coil up and hang like tiny beads, then these uncoil and others roll +up, so that these graceful floating lines are never two seconds alike. + +We do not really know their use. Sometimes the creature anchors itself +by them, rising and falling as they stretch out or coil up; but more +often they float idly behind it in the water. At first you would +perhaps think that they served to drive the ball through the water, +but this is done by a special apparatus. The cross ridges which we +noticed on the bands are really flat comb-like plates (_p_, Fig. 9), +of which there are about twenty or thirty on each band; and these +vibrate very rapidly, so that two hundred or more paddles drive the +tiny ball through the water. This is the cause of the prismatic +colors; for iridescent tints are produced by the play of light upon +the glittering plates, as they incessantly change their angle. +Sometimes they move all at once, sometimes only a few at a time, and +it is evident the creature controls them at will. + +This lovely fairy-like globe, with its long floating tentacles and +rainbow tints, was for a long time classed with the jelly-fish; but it +really is most nearly related to the sea-anemones, as it has a true +central cavity which acts as a stomach, and many other points in +common with the _Actinozoa_. We cannot help wondering, as the little +being glides hither and thither, whether it can see where it is going. +It has nerves of a low kind which start from a little dark spot (_ng_) +exactly at the south pole of the ball, and at that point a sense-organ +of some kind exists, but what impression the creature gains from it of +the world outside we cannot tell. + +I am afraid you may think it dull to turn from such a beautiful being +as this, to the gray leaf which looks only like a dead dry seaweed; +yet you will be wrong, for a more wonderful history attaches to this +crumpled dead-looking leaf than to the lovely jelly-globe. + +[Illustration: FIG. 10. THE SEA-MAT OR FLUSTRA (_Flustra foliacea_). + +1, Natural size. 2, Much magnified, _s_, Slit caused by drawing in of +the animal _a_.] + +First of all I will pass round pieces of the dry leaf (1, Fig. 10), +and while you are getting them I will tell you where I found the +living ones. Great masses of the Flustra, as it is called, line the +bottom and sides of my pool. They grow in tufts, standing upright on +the rock, and looking exactly like hard gray seaweeds, while there is +nothing to lead you to suspect that they are anything else. Yesterday +I chipped off very carefully a piece of rock with a tuft upon it, and +have kept it since in a glass globe by itself with sea-water, for the +little creatures living in this marine city require a very good supply +of healthy water and air. I have called it a "marine city," and now I +will tell you why. Take the piece in your hand and run your finger +gently up and down it; you will glide quite comfortably from the lower +to the higher part of the leaf, but when you come back you will feel +your finger catch slightly on a rough surface. Your pocket lens will +show you why this is, for if you look through it at the surface of the +leaf you will see it is not smooth, but composed of hundreds of tiny +alcoves with arched tops; and on each side of these tops stand two +short blunt spines, making four in all, pointing upwards, so as partly +to cover the alcove above. As your finger went up it glided over the +spines, but on coming back it met their points. This is all you can +see in the dead specimen; I must show you the rest by diagrams, and by +and by under the microscope. + +First, then, in the living specimen which I have here, those alcoves +are not open as in the dead piece, but covered over with a transparent +skin, in which, near the top of the alcove just where the curve +begins, is a slit (_s_ 2, Fig. 10) Unfortunately, the membrane +covering this alcove is too dense for you to distinguish the parts +within. Presently, however, if you are watching a piece of this living +leaf in a flat water-cell under the microscope, you will see the slit +slowly open, and begin to turn as it were inside out, exactly like the +finger of a glove, which has been pushed in at the tip, gradually +rises up when you put your finger inside it. As this goes on, a bundle +of threads appears, at first closed like a bud, but gradually opening +out into a crown of tentacles, each one clothed with hairs. Then you +will see that the slit was not exactly a slit after all, but the round +edge where the sac was pushed in. Ah! you will say, you are now +showing me a polyp like those on the sertularian tree. Not so fast, my +friend; you have not studied what is still under the covering skin and +hidden in the living animal. I have, however, prepared a slide with +this membrane removed and there you can observe the different parts, +and learn that each one of these alcoves contains a complete animal, +and not merely one among many mouths, like the polyp on Sertularia. + +[Illustration: FIG. 11. DIAGRAM OF THE ANIMAL IN THE FLUSTRA OR +SEA-MAT. + +1, Animal protruding. 2, Animal retracted in the sheath, _sh_, +Covering sheath, _s_, Slit. _t_, Tentacles. _m_, Mouth. _th_, Throat, +_st_, Stomach. _i_, Intestine, _r_, Retractor muscle, _e_, Egg-forming +parts. _g_, Nerve-ganglion.] + +Each of these little beings (_a_, Fig. 10) living in its alcove has a +mouth, throat, stomach, intestine, muscles, and nerves starting from +the ganglion of nervous matter, besides all that is necessary for +producing eggs and sending forth young ones. You can trace all these +under the microscope (see 2, Fig. 11) as the creature lies curiously +doubled up in its bed, with its body bent in a loop; the intestine +_i_, out of which the refuse food passes, coming back close up to the +slit. When it is at rest, the top of the sac in which it lies is +pulled in by the retractor muscle _r_, and looks, as I have said, like +the finger of a glove with the top pushed in. When it wishes to feed +this top is drawn out by muscles running round the sac, and the +tentacles open and wave in the water (1, Fig. 11). + +Look now at the alcoves, the homes of these animals; see how tiny they +are and how closely they fit together. Mr. Gosse, the naturalist, has +reckoned that there are six thousand, seven hundred and twenty alcoves +in a square inch; then if you turn the leaf over you will see that +there is another set, fixed back to back with these, on the other +side, making in all, thirteen thousand, four hundred and forty +alcoves. Now a moderate-sized leaf of flustra measures about three +square inches, taking all the rounded lobes into account, so you will +see we get forty thousand, three hundred and twenty as a rough +estimate of the number of beings on this one leaf. But if you look at +this tuft I have brought, you will find it is composed of twelve such +leaves, and this after all is a very small part of the mass growing +round my pool. Was I wrong, then, when I said my miniature ocean +contains as many millions of beings as there are stars in the heavens? + +You will want to know how these leaves grew, and it is in this way. +First a little free swimming animal, a mere living sac provided with +lashes, settles down and grows into one little horny alcove, with its +live creature inside, which in time sends off from it three to five +buds, forming alcoves all round the top and sides of the first one, +growing on to it. These again bud out, and you can thus easily +understand that, in this way, in time a good-sized leaf is formed. +Meanwhile the creatures also send forth new swimming cells, which +settle down near to begin new leaves, and thus a tuft is formed; and +long after the beings in earlier parts of the leaf have died and left +their alcoves empty, those round the margin are still alive and +spreading.... + +If you can trace the spore-cells and urns in the seaweeds, observe the +polyps in the Sertularia, and count the number of mouths on a branch +of my animal fringe (Sertularia tenella); if you make acquaintance +with the Thuricolla in its vase, and are fortunate enough to see one +divide in two; if you learn to know some of the beautiful forms of +diatoms, and can picture to yourself the life of the tiny inhabitants +of the Flustra; then you will have used your microscope with some +effect, and be prepared for an expedition to my pool, where we will go +together some day to seek new treasures. + +[Illustration] + + + + +NOTES + + +AGASSIZ, J.L.R., naturalist, born in Switzerland, 1807; died, +Cambridge, Mass., 1873. In 1846 he came to America, after having +gained a high reputation in Europe, to deliver a course of lectures in +Boston "On the Plan of the Creation," and met with such success that +he spent the rest of his days there, declining an invitation to return +to his native country and to Paris. In 1848 he was elected to the +chair of Natural History at Harvard. In 1850-51 he went on an +expedition to the Florida Reefs. In 1858 he founded and organized the +Museum of Comparative Zoölogy at Cambridge--and, later on, went on his +important voyage to Brazil. In 1872 he founded and organized the +summer school of Natural History at Buzzard's Bay. He wrote "The +Fishes of Brazil," "A Study of Glaciers," "Natural History of the +Fresh Water Fishes of Central Europe," "Contributions to the Natural +History of the United States" (unfinished), and with his wife, "A +Journey in Brazil." + +BALL, PROF. SIR R.S., English astronomer, born in Dublin, 1840. Was +appointed Lord Ross's astronomer in 1865. Professor of mathematics and +mechanics at the Royal Irish College of Science in 1873, and is now +astronomer royal for Ireland. He is the author of "The Story of the +Heavens," "Starland," etc., and is well known as a successful lecturer +on astronomical subjects in this country. + +DARWIN, CHARLES R., English naturalist, born, 1809; died, 1882. He +first formulated what is known as the principle of Natural Selection. +In 1831 he went in the famous scientific voyage of the _Beagle_ as +naturalist, and afterwards published an account of it. He was one of +the most thorough, careful, and painstaking scientific men of this or +any age. He is the author of many famous books. "The Origin of +Species," "The Descent of Man," "Insectivorous Plants," "The Power of +Movement in Plants," "The Structure and Distribution of Coral Reefs," +"Geological Observations on Volcanic Islands." "The Formation of +Vegetable Mould" was his last published work. + +FLAMMARION, C., famous French astronomer, born, 1842. He has written +many popular works on astronomy, most of which have been translated +into English. "The Stars," "The World Before the Creation," "Uranus," +"Comets," "Popular Astronomy," are among his best known. + +HOLDEN, PROF. E.S., American astronomer, born at St. Louis, 1846. +Lieutenant engineers, U.S.A., 1870-73; professor mathematics, U.S.N., +1873-81; director Washburn Observatory, 1881-85; president University +of California, 1883-88; director Lick Observatory, 1888-98. Is a +member of several learned societies of Europe. Is the author of a +"Life of William Herschel," "A Hand-book of the Lick Observatory," +"Earth and Sky," "Primer of Heraldry," "Elementary Astronomy," "Family +of the Sun," "Essays in Astronomy," "Stories of the Great +Astronomers," etc. + +HUXLEY, T.H., English biologist, born, 1825; died, 1895. Went on an +exploring expedition on the _Rattlesnake_, and devoted himself to the +study of marine life. For his scientific researches he received many +honors. His lectures were models of clearness, and he could simplify +the most difficult subjects. He strongly advocated Darwin's views and +evolutionist doctrines. His writings are numerous and many of them +technical. Among some of the most popular are "Man's Place in Nature," +his "Lay Sermons," "Critiques and Addresses," "American Addresses," +"Physiography," "Science and Culture," "Lessons in Elementary +Physiology," etc. + +KINGSLEY, C., English clergyman and author, born, 1819; died, 1875. +Wrote "Westward, Ho!" which every boy should read, "Hypatia," "Alton +Locke," "Hereward the Wake," etc., and a charming book of travel, +entitled, "At Last." His "Water Babies" is exceedingly popular, and +his "Heroes" is a book much appreciated by the boys and girls alike. + +PROCTOR, R.A., English astronomer, born, 1834; died, 1888. He was a +very popular writer, and lectured on astronomical subjects in this +country, and in England and her colonies. A memorial teaching +observatory is erected in his honor near San Diego, Cal. He was a man +of untiring industry, an athlete, a musician, and a chess-player. His +books are numerous. Among them are "Half Hours with the Telescope," +"Other Worlds than Ours," "Light Science for Leisure Hours," "The +Expanse of Heaven," "The Moon," "The Borderland of Science," "Our +Place Among Infinites," "Myths and Marvels of Astronomy," "The +Universe of Suns," "Other Suns than Ours," etc. + +SHALER, N.S., professor of geology at Harvard. Born Newport, Ky., +1841. Served in the Union Army during the Civil War. Instructor +zoölogy, geology, and paleontology, Lawrence Scientific School, till +1887. Since then at Harvard. Is the author of "Kentucky a Pioneer +Commonwealth," "The Story of Our Continent," "The Interpretation of +Nature," "Feature of Coasts and Oceans," "Domesticated Animals," "The +Individual," "Study of Life and Death," etc. + +THOMPSON, SIR C. WYVILLE, English zoölogist, born, 1830; died, 1882. +He conducted scientific dredging expeditions in the _Lightning_ and +_Porcupine_, 1868-69, and was the scientific head of the famous voyage +of 68,900 miles in the _Challenger_ for deep-sea explorations +(1872-76). His books are "The Depths of the Sea," and "The Voyage of +the Challenger." + +TYNDALL, JOHN, English physicist, born, 1820. Began his original +researches in 1847, when teacher of physics in Queenwood College. He +and Professor Huxley visited the Alps together, and they wrote a work +on the structure and nature of glaciers. It is impossible to detail +the work he has done; but his inquiries and experiments in connection +with light, heat, sound, and electricity have all had practical +results. He is a popular lecturer, and devoted the proceeds of a +lecturing tour in this country to founding scholarships at Harvard and +Columbia Colleges, for students devoting themselves to original +research. Among his books are "Glaciers of the Alps," "Mountaineering," +"Heat as a Mode of Motion," "On Radiation," "Hours of Exercise in the +Alps," "Fragments of Science," "The Floating Matter of the Air," and +volumes on Light, Sound, Electricity, and the forms of water. + +WALLACE, A.R., English naturalist and traveller, born 1822; was +educated as land surveyor and architect, but afterwards devoted +himself entirely to Natural History. He explored the Valley of the +Amazon and Rio Negro, 1848-52, and travelled in the Malay Archipelago +and Papua, 1854-62, publishing the results of his explorations later +on. He also wrote "Contributions to the Theory of Natural Selection," +"Miracles and Modern Spiritualism," "Geographical Distribution of +Animals," "Tropical Nature," "Island Life," etc. + +GIBERNE, AGNES, English author--living. Began to write at seven years +old. Her first story for children was published when she was only +seventeen. Her stories for children have not been so popular as her +scientific writings, "Sun, Moon, and Stars," "The Starry Skies," +"Among the Stars," "The Ocean of Air," "The World's Foundations," +"Radiant Suns," etc. + +WILSON, ANDREW, English physiologist and lecturer, born, 1852. Is the +author of "Studies on Life and Sense," "Leisure Time Studies," +"Science Stories," "Chapters on Evolution," "Wild Animals," "Brain and +Nerve," etc., and is a constant contributor on scientific subjects to +the magazines and newspapers, contributing weekly "Science Jottings" +to the "Illustrated London News" + + + + +WONDERS OF EARTH, SEA, AND SKY + +SUGGESTIONS FOR SUPPLEMENTARY READING + + + Wonder Stories of Science + D.N. BEACH + + Wonders in Monsterland + EDWARD W.D. CUMING + + Ocean Wonders + W.E. DAMON + + Among the Stars + AGNES GIBERNE + + The Scenery of the Heavens + JOHN ELLARD GORR + + Coal and the Coal Miners + HOMER GREENE + + Wonders of the Moon + A. GUILLEMIN + + The Sea and Its Living Wonders. + G. HARTWIG + + The Wonders of Plant Life Under the Microscope + SOPHIE B. HERRICK + + Marvels of Animal Life + CHARLES F. HOLDER + + Old Ocean + ERNEST INGERSOLL + + Modern Seven Wonders of the World + C. KENT + + Madam How and Lady Why + CHARLES KINGSLEY + + Wonders of Optics + F. MARION + + The Wonders of Science + HENRY MAYHEW + + Wonders of Man and Nature + E. MENAULT + + A Century of Electricity + T.C. MENDENHALL + + The Orbs of Heaven + ORMSBY S. MITCHELL + + Under Foot + LAURA D. NICHOLS + + Myths and Marvels of Astronomy + R.A. PROCTOR + + The Wonders of the World + CHARLES G. ROSENBERG + + The Wonders of Nature + PROFESSOR RUDOLPH + + Volcanoes of North America + ISRAEL COOK RUSSELL + + Aspects of the Earth + N.S. SHALER + + Wonders of the Bird World + R.B. SHARPE + + The Wonders of Water + GASTON TISSANDIER + + Total Eclipses of the Sun + MABEL L. TODD + + Wonders of Insect Life + JOSEPH C. WILLET + + + +*** END OF THE PROJECT GUTENBERG EBOOK 15884 *** |