P25 Fie oN LiQm/r DOUBL e RuMBcR apne sows - " { RZ LILA LLL LLLLLL La COL CLLOLELLEA iS R MODERN SCIENCE AND MODERN THOUGHT Sd a as SSSSA SISSSLS BY SAMUEL LAING © ITIL IAL LPSILLILLLS i an PART: I. = SL So a ~- : ia ie ik RN THE HUMBOLDT PUBLISHING COMPANY | ul 19 ASTOR PLACE 8 EIN Zs) SLL DPOLD (ONLY BY SUBSCRIPTION. COMPLETE SETS OF THE HUMBOLDT LIBRARY CAN BE. OBTAINED UNIFORM <“IN' “SIZES STYLE OF o BINDING. (RTC. The Volumes average 600 pages each, and are arranged thus: Volume F. “Goptains ONumibers 5) Ge doe Ae eh as Be Bie tea 0 ica Scene I-12 a IT f BE eI Be La ie aie CE ee ie ae 13-24 ff III S oo a RM NS haite lee otal dele eS eed doe aa ean a 25-36 c IV c cg OS ET oie) ..37-48 v V if PT Se oS ve Siglalle at taut sie els gta alts 5: ean 49-59 . VI i BR he Nite se SIRO ae Gunn ata ae wae (ais er 60-70 i VII Hi Nn MMERAE UAL ANIC GA UR aay Sees AY 71-80 Gri. Il c ce OO NE Se ee 81-91 \ ; IX % FF des bg abr alnie a Ltn dete UND oa eae ea a 92-103 \ eae X. iy LIEN Bata g Ce A ae TELS SNA ase aie IO4-IIL itt XT a Te ee pian el caal Ua sie vale: oe taster txt rt to tit aL ana 112-118 ag eaw.Gul Ef fT ll eee a he -, I1Q-127 \ | “oe XII. s ‘i cri bites We Ub gle Wiha s Kaplehp ele Ca ay ont . \ | 5 XIV. “ De OIE INE E oy ae CRU ee MT Cant kh 134-139 : \ i XV: rf BE a SES UTA nn Ts Tee aaa ean 140-147 N Ny XVI. i DL APR pa) SOC Reig a a tae way tall a a a er 148-158 A eT 4 LS OAD arr, UU ee UE aor 5G 6) 159-168 CLOTH, EXTRA, $2.00 PER VOLUME, | OR $34.00 FOR 17 VOLUMES. The various books contained in this library of 17 volumes would cost $300 if bought in separate volumes as published in ~ London and New York. 7 THE HUMBOLDT PUBLISHING CO., " cay I9 Astor Place, New York... MODERN SCIENCE AND MODERN THOUGHT. WITH A SUPPLEMENTAL CHAPTER ~ ON GLADSTONE’S «DAWN OF CREATION” AND “PROEM OF GENESIS,’ AND ON DRUM- MOND’S “ NATURAL LAW IN THE SPIRITUAL WORLD.’ BY S. LAING. New York: THe HUMBOLDT PUBLISHING CO.,, 28 LAFAYETTE PLACE. CONTENTS, PART J. MODERN SCIENCE. CHAPTER I. PAGE BPACE . - : S E : i ‘ ‘ ; LA, Primitive Ideas—Natural Standards—Dimensions of the Earth—Of Sun and Solar System—Distance of Fixed Stars—Their Order and Size— Nebulz and other Universes—The Telescope and the Infinitely Great— The Microscope and the Infinitely Small—Uniformity of Law—Law of Gravity—Acts through all Space—Double Stars, Comets, and Meteors— Has acted through all Time. CHAPTER II. TIME . ; ° i 4 . : 2 : . ne Wg Evidence of Geology—Stratification—Denudation—Strata identified by Superposition—By Fossils—Geological Record shown by Upturned Strata— General Result—Palewozoic and Primary Periods—Secondary—Tertiary— Time required—Coal Formation—Chalk—Elevations and Depressions of Land—Internal Heat of Earth—Earthquakes and Volcanoes—Changes of Fauna and Flora— Astronomical Time—Tides and the Moon—Sun’s Radiation—Earth’s Cooling—Geology and Astronomy—Bearings on Mod- - ern Thought. 1015097 4 CONTENTS. CHAPTER III. PAGE MATTER A ° . : - 382 %, Ether and Light Soler and Hea! Matter a ie Elements—Molecules and Atoms—Spectroscope—Uniformity of Matter throughout the Uni- verse—Force and Motion—Conservation of Energy—Electricity, Magnet- ism, and Chemical Action—Dissipation of Heat—Birth and Death of Worlds. CHAPTER IV. LIFE . : : : : : . ° - 44 Essence of Tite Spin plest Form, HrotopinantetMt share and Protista— Animal and Vegetable Life—Spontaneous Generation—Development of Species from Primitive Cells—Supernatural Theory—Zodlogical Prov- inces—Separate Creations—Law or Miracle—Darwinian Theory—Struggle for Life—Survival of the Fittest—Development and Design—The Hand— Proof required to establish Darwin’s Theory as a Law—Species—Hybrids— ‘Man subject to Law. CHAPTER V. ANTIQUITY OF MAN. : ° : ° ° - 57 Belief in Man’s Recent Origin ARoueter de Perthes’ Discoveries—Con- firmed by Prestwich—Nature of Implements—Celts, Scrapers, and Flakes— Human Remains in River Drifts—Great Antiquity—Implements from Drift at Bournemouth—Bone Caves—Kent’s Cavern—Victoria, Gower, and other Caves—Caves of France and Belgium—aAges of Cave Bear, Mammoth, and Reindeer—Artistic Race—Drawings of Mammoth, etc.—Human Types— Neanderthal, Cro-Magnon, Furfooz, etc.— Attempts to fix Dates—History— Bronze Age—Neolithic—Danish Kitchen-middens—Swiss Lake-Dwellings— Glacial Period—Traces of Ice—Causes of Glaciers—Croll’s Theory—QGulf Stream—Dates of Glacial Period—Rise and Submergence of Land—Ter- tiary Man—Eocene Period—Miocene—Evidence for Pliocene and Miocene -Man—Conclusions as to Antiquity. CHAPTER VI. 'MAN’S PLACE IN NATURE . - 89 Origin of Man from an Hae hike ciher Mammsls—Development of the Embryo—Backbone—Eye and other Organs of Sense—Fish, Reptile, and Mammalian Stages—Comparison with Apes and Monkeys— Germs of Hu- man Faculties in Animals—The Dog—Insects—Helplessness of Human Infant—Instinct—Heredity and Evolution—The Missing Link—Races of ‘Men—Leading Types and Varieties—Common Origin Distant—Language— CONTENTS. 5 PAGE How Formed—Grammar—Chinese, Aryan, Semitic, ete.—Conclusions from Language—Evolution and Antiquity—Religions of Savage Races— Ghosts and Spirits—Anthropomorphie Deities—Traces in Neolithic and Paleolithic Times—Development by Evolution—Primitive. Arts—Tools and Weapons—Fire—Flint Implements—Progress from Palzolithic to Neolithic Times—Domestic Animals—Clothing—Ornaments—Conclusion, Man a Product of Evolution. PART II, MODERN THOUGHT. CHAPTER VII. MODERN THOUGHT . ela ete: Lines from Re yi Ceanal of Modern THoupne Change Scent fied by Carlyle, Renan, and George Eliot—Science becoming Universal— Attitude of Orthodox Writers—Origin of Evil—First Cause unknowable— New Philosophies and Religions—Herbert Spencer and Agnosticism— Comte and Positivism—Pessimism—Mormonism—Spiritualism—Dreams and Visions—Somnambulism—Mesmerism—Great Modern Thinkers— Carlyle—Hero-worship. CHAPTER VIII. MIRACLES . : . . : ° ~Aad Origin of Belief in the iRdpernntormbThander—-Belist in Miracles form- erly Universal—St. Paul’s Testimony—Now Incredible—Christian Miracles —Apparent Miracles—Real Miracles—Absurd Miracles—Worthy Miracles —The Resurrection and Ascension—Nature of Evidence required—Inspi- ration—Prophecy—Direct 'Evidence—St. Paul—The Gospels—What is Known of Them—The Synoptic Gospels—Resemblances and Differences— Their Origin—Papias—Gospel of St. John—Evidence rests on Matthew, Mark, and Luke—What each states—Compared with one another and with St. John—Hopelessly Contradictory—Miracle of the Ascension—Silence of Mark—Probable Early Date of Gospels—But not in their Present Form. CHAPTER IX. CHRISTIANITY WITHOUT MIRACLES . : + 142 Practical and Theoretical Christianity—Example and aeching of Cheat Christian Dogma—Moral Objections—Inconsistent with Facts—Must be 6 CONTENTS. PAGE accepted as Parables—Fall and Redemption—Old Creeds must be Trans- formed or Die—Mahometanism—Decay of Faith—Balance of Advantages —Religious Wars and Persecutions—Intolerance—Sacrifice—Prayer—Ab- sence of Theology in Synoptic Gospels—Opposite Pole to Christianity— Courage and Self-reliance—Belief in God and a Future Life—Based mainly on Christianity—Science gives no Answer—Nor Metaphysics—So-called Institutions—Development of Idea of God—Best Proof afforded by Chris- tianity—Evolution is Transforming it—Reconciliation of Religion and Science. CHAPTER X. PRACTIOAL LIFE . : ° . : ° . : - 153 Conscience—Right is Right—Self-reverence—Courage—Respectability— Influence of Press—Respect for Women—Self-respect of Nations—Democ- racy and Imperialism—Self-knowledge—Conceit—Luck—Speculation— Money-making—Practical Aims of Life—Self-control—Conflict of Reason and Instinct—Temper—Manners—Good Habits in Youth—Success in Prac- tical Life—Education—Stoicism—Conclusion, SUPPLEMENTAL CHAPTER. Gladstone’s ‘Dawn of Creation” and ‘‘Proem to Genesis.” Drummond’s ‘* Natural Law in the Spiritual World’. . . . . - 164. PREFACE TO FIRST EDITION. HE object of this book is to give a clear and concise view of the principal results of Modern Science, and of the revolution which they have effected in Modern Thought. I do not pretend to discover fresh facts or to propound new theories, but simply to discharge the humbler though still useful task of presenting what has become the common property of thinking minds, in a popular shape, which may interest those who lack time and opportunity for studying special sub- jects in more complete and technical treatises. I have endeavored also to give unity to the subjects treated of, by connecting them with leading ideas: in the case of Science, that of the gradual progress from human standards to those of almost infinite space and duration, and the prevalence of law throughout the universe to the exclusion of supernatural interference; in the case of Thought, the bearings of these discoveries on old creeds and philosophies, and on the practical conduct of life. The endeavor to show how much of religion can be saved from the shipwreck of theology has been the main object of the second part. Those who are acquainted with the scientific literature of the day will at once see how much I have been indebted to Darwin, Lyell, Lubbock, Huxley, Proctor, and other well- known writers. In fact, the first part of this book does not pretend to be more than a compendious popular abridgment of their works. T $ PREFACE. prefer, therefore, acknowledging my obligations to them once for all,. rather than encumbering each page by detailed references. The second part contains more of my own reflections on the im- portant subjects discussed, and must stand or fall on its own merits. rather than on authority. Ican only say that I have endeavored to — treat these subjects in a reverential spirit, and that the conclusions: arrived at are the result of a conscientious and dispassionate endeavor: to arrive at “the truth, the whole truth, and nothing but the truth.” S. Larne. MODERN SCIENCE ND M@DENNs THOUGHT: CHAPTER I. SPACE. HE first ideas of space were naturally taken from the standard of man’s Own impressions. ‘Theinch, the foot, the cubit, were the | lengths of portions of his own body, obviously adapted for measuring objects of comparatively small size with which he came in direct contact. The mile was the distance traversed in 1,000 double paces; the league the distance walked in an hour. The visible horizon suggested the idea that the earth was a flat, circular surface like a round table; and as experience showed that it extended beyond the limits of a single horizon, the conception was enlarged, and the size of the table increased so as to take in all the countries known My the geography of successive eriods. ! i In like manner the sun, moon, and stars were taken to be at the dis- tance at which they appeared; that is, first of the visible horizon, and then of the larger circle to which it had been found necessary to expand it. It was never doubted that they really revolved, as they seemed to do, round this flat earth circle, dipping under it in the west at night, and reappearing in the east with the day. The conception of the uni- verse, therefore, was of a flat, circular earth surrounded by an ocean. stream, in the centre of a crystal sphere which revolved in twenty-four hours round the earth, and in which the heavenly bodies were fixed as lights for man’s use to distinguish days and seasons. The maximum idea of space was therefore determined by the size of the earth circle which was necessary to take in all the regions known at the time, with a little margin beyond for the ocean stream, and the space between it and the crystal vault, required to enable the latter to revolve freely. In the time of Homer and the early Greek philosophers, this would prob- ably require a maximum of space of from 5,000 to 10,000 miles. This dimension has been expanded by modern science into one of as many millions, or rather hundreds of millions, as there were formerly single miles, and there is no sign that the limit has been reached. How has this wonderful result been arrived at, and how do we feel certain that itis true? Those who wish thoroughly to understand it must study standard works on Astronomy, but it may be possible to give some clear idea of the processes by which it has been arrived at, and of: 10 MODERN SCIENCE AND MODERN THOUGHT. the cogency of the reasoning by which we are compelled to accept facts 80 contrary to the first impressions of our natural senses. The fundamental principle upon which all measurements of space depend, which are beyond the actual applicationtof human standards, 1s this: that distant objects change their Lane bearings for a given change of base, Cachet more or less Ra ae et they are H less or more distant. Suppose I am on board a steamer sailing down the Thames, and I see two churches on the Essex coast directly opposite to me, or bearing due north, the first of which is one mile and the other ten miles distant. I sail one mile due east and again take the bearings. It is evident that the first church will now bear north-west, or have ap- parently moved through 45°, Ze., one-eighth part of the circumference of acomplete circle, assuming this circumference to be divided into 360 equal parts or degrees; while the more distant church will only have altered its bearing by a much less amount, easily determined by calcu- lation, but which may be taken roughly at 5° instead of 45°. The branch of mathematics known as Trigonometry enables us in all cases, without exception, where we know the apparent displace- ment or change of bearing of a dis- *® tant object produced by taking it from the opposite ends of a known base, to calculate the distance of that object with as much ease and certainty as if we were working a simple sum of rule of three. The first step is to know our base, and for this purpose itis essential to know the size and form of the earth on which we live. ‘These are determined by very simple consid- erations. If I walk a milein a straight line, an object at a vast distance like ie astar will not change its apparent : place perceptibly. Butif I walk the & same distance in a semi-circle, what re: faa a =: was originally on my left hand will “now be on my right, or will have changed its apparent place by 180°. If I walk my mile on the circum- ference of a circle of twice the size, I shall have traversed a quadrant or one-fourth part of it, and changed ‘the bearing of the distant object exactly halfas much, or 90°, and so S; St * t 1 { 4 4 r] ‘ 6 ' t ( { 4 t t i} i] t] 4 4 ( t t % Swe ne OS MO SS POSS reer em =A { ‘ ( { t t ‘ ‘ ‘ | t { ( ' t t ' { t t t t t ' \ \ ( ! { ‘ 1 ' ‘ | SPACE. 11 on, according to the size of the circle, which may therefore be readily calculated from the length that must be travelled along it to shift the bearing of the remote object by a given amount, say of 1°. If, for instance, by travelling 65 miles from north to south we lower the apparent height of the Pole star 1°, it is mathematically certain that we have travelled this 65 miles, not along a flat surface, but along a circle which is 360 times 65, or, in round numbers, 24,000 miles in circumference and 8,000 miles in diameter. And if, whenever we travel the same distance on a meridian or line drawn on the cir- cumference from north to south, we find the same displacement of 1°, we may be sure that our journey has been in a true circle, and that the form of the earth is a perfect sphere of these dimensions. Now, this is very nearly what actually occurs when we apply methods of scientific accuracy to measure the earth. The true form of the earth is not exactly spherical, but slightly oval or flatter at the poles, being almost precisely the form it would have assumed if it had been a fluid mass rotating about a north and south axis. But it is very nearly spherical, the true polar diameter being 7,899 miles, and the true equatorial diameter 7,925 miles, so that for practical pur- poses we may say roughly that the earth is a spherical body, 24,000 miles round and 8,000 miles across. This gives us afresh standard from which to start in measuring greater distances. Precisely as we inferred the distance of the church from the steamer in our first illustration, we can infer the distance of the sun, from its displacement caused by observing it from two oppo- site ends of a base of known length on the earth’s surface. This is the essential principle of all the calculations, though, when great ac- curacy is sought for, very refined methods of applying the principle are required, turning mainly on the extent to which the apparent occurrence of the same event—such as the transit of Venus over the sun’s disc—is altered by observing it from different points at known distances from one another on the earth’s surface. The result is to show that the sun’s distance from the earth is, in round numbers, 93,- 000,000 miles. This is not an exact statement, for the earth’s orbit is not an exact circle, but the sun and earth really revolve in ellipses about the common centre of gravity. The sun, however, is so much larger than the earth that this centre of gravity falls within the sun’s surface, and, practically, the earth describes an ellipse about the sun, the 93,000,000 miles being the mean distance, and the eccentricity, or deviation from the exact circular orbit, being about one-sixtieth part of that mean distance. This distance, again, gives us the size of the sun, for it is easily calculated how large the sun must be to look as large as it does ata distance of 93,000,000 miles. The result is, thatit is a sphere of about 880,000 miles in diameter. Its bulk, therefore, ex- ceeds that of the earth in the proportion of 1,384,000 to 1. Its density, or the quantity of matter in it, may be calculated from the effect of its action on the earth under the law of gravity at the dis- tance of 93,000,000 miles. It weighs as much as 354,936 earths. The same method gives us the distance, size, and weight of the moon and planets; and it gives us « fresh standard or base from which to measure still greater distances. The distance of the earth from the sun being 93,000,000 miles, and its orbit an ellipse nearly circular, it follows that it is in mid-winter, in round numbers, 186,000,000 miles distant from the spot where 1t was at mid-summer. What difference in 12 MODERN SCIENCE AND MODERN THOUGHT. the bearings of the fixed stars is caused by traversing this enormous base? The answer is, in the immense majority of cases, no difference at all; z.¢., their distance is so vastly greater than 186,000,000 miles that a change of base to this extent makes no change perceptible to the most refined instruments in their bearings as seen from the earth. But the perfection of modern instruments is such, that a change of even one second, or sth part of one degree, in the annual varallax, as it is called, of any fixed star, would certainly be detected. This corresponds to a distance of 206,265 times the length of the base of 186,000,000 miles, or of 20,000,000,000,000,000 miles, a dis- tance which it would take light moving at the rate of 190,000 miles per second, three years and eighty-three day to traverse. There is only one star in the whole heavens, a bright star called Alpha, in the constellation of the Centaur, which is known to be as near as this. Its annual parallax is 0:976", or very nearly 1”, and therefore its distance very nearly 20 millions of millions of miles. All the other stars, of which many millions are visible through powerful telescopes, are further off than this. There are about eight other stars which have been supposed by astronomers to show some trace of an annual parallax of less than half a second, and therefore whose distances may be somewhere from twice to ten times as great as that of Alpha Centauri, and from the quantity of light sent to us from these distances, some approximation has been made to their intrinsic splendor as compared with our sun. That of Alpha Centauri is computed to be nearly 24 times that of Sirius, the brightest star in the heavens, 393 times greater than that of thesun. These fisures may or may not represent greater size or greater intensity of light, and they are only quoted to give some idea of the vastness of the scale of the universe, cf which our solar system forms a minute part. Nor does even this nearly fathom the depth of the abysses of space. Telescopes enable us to seea vast multitude of stars of varying size and brilliancy. It is computed by astronomers that there are at least one hundred millions of stars within the range of the telescopes used by Herschel for gauging the depth of space, anda thousand millions within the range of the great reflecting telescope of Lord Rosse. As many as eighteen different orders of magnitude have been counted, and. the more the power of telescopes is increased the more stars are seen. Now, as there is no reason to suppose that this extreme variety of brilliancy arises from extreme difference of size of one star from an- other, it must be principally owing to difference of distance, so that a star of the eighteenth magnitude is presumably many times further off than any of the first magnitude, the distance of the nearest of which has been proved to be something certainly not less than 20,000,000,000,- 000 miles. In fact, these stellar distances are so great that in order to bring them at ali within the range of human imagination we are obliged to apply another standard, that of the velocity of light. Light can be shown to travelat the rate of about 186 millions of miles in 16 minutes, for this is the difference of the time at which we see the same periodical occurrence, as for instance the eclipses of Jupiter’s satellites, according as the earth happens to be at the point ofits orbit nearest to Jupiter or at that farthest away. The velocity of light is therefore about 184,000 miles per second, a velocity which has been fully con- firmed by direct experiments made on the earth’s surface. SPACE. 13 These enormous distances are reckoned, therefore, by the number of years which it would take light to come from them, travelling as it does at the rate of 184,000 miles a second. The nearest fixed star, Alpha Centauri, is seen by the ray which left it three years and eighty- three days ago, and has been travelling ever since at the rate of 184,000 miles per second. Sirius, the brightest of the fixed stars, if the deter- mination of its annual parallax is correct, is six times further off, and is seen, not as it exists to-day but as it existed nearly twenty years ago; and the light we now see from some of the stars of the eighteen magni- tude can hardly have left them less than 2,000 years ago. Even this, however, is far from exhausting our conception of the magnitude of space. Beyond the stars which are near enough to be seen separately, powerful telescopes show a galaxy in which the united lustre of myriads of stars is only perceptible as a faint nebulous gleam. And in addition to stars the telescope shows us a number of nebule, or faint patches of light, sometimes globular, sometimes in wreaths, spiral wisps, and other fantastic shapes, scattered about the heavens. Some of these are resolved by powerful telescopes into clusters of stars incon- ceivably numerous and remote, which appear to be separate universes, like that of which our sun and fixed stars form one. Others again cannot be so resolved, and are shown by the spectroscope to be enor- mous masses of glowing gas, or cosmic matter, out of which other universes are in process of formation. Weare thus led, step by step, to enlarge our ideas of space from the primitive conception of miles and leagues, until the imagination fails to grasp the infinite vastness of the scale upon which the material universe is really constructed. If the telescope takes us thus far beyond the standards of unaided sense in the direction of the infinitely great, the microscope, aided by calculations as to the nature of light, heat, electricity, and chemical action, takes us as far in the opposite direction of the infinitely small. The microscope enables us actually to see magnitudes of the order of x00,000th of an inch as clearly as the naked eye can see those of j,th. This introduces us into a new world, where we can see a whole universe of things both dead and alive of whose existence our forefathers had no suspicion. A glass of water is seen to swarm with life, and be the abode of bacteria, amosbee, rotifers, and other minute creatures, which dart about, feed, digest, and propagate their species in this small world of their own, very much as jelly-fish and other humble organisms do in the larger seas. The air also is shown to be full of innumerable germs and spores floating in it, and ready to be deposited and spring into life, wherever they find a seed-bed fitted to receive them. Given a favor- able soil in the human frame, and the invisible seeds of scarlet fever, cholera, and small-pox ripen into full crops, just as the germs of a fungus invade the potato crops of a whole district, and lead to Irish famines and the extermination of more than a million of human beings. The microscope also enables us to see the very beginnings of life and watch its primitive element, protoplasm, in the form of a minute speck of jelly-like matter, through which pulsations are constantly passing, and we can watch the transformations by which an elementary cell of this substance splits up, multiplies, and by a continued process of development builds up with these cells all the diversified forms of wegetable and animal life. But far as the microscope carries us down to dimensions vastly 14 MODERN SCIENCE AND MODERN THOUGHT. smaller than those of which the ordinary senses can take cognizance, the modern sciences of light, heat, and chemistry carry us as much farther downwards, as the telescope carries us upwards beyond the boundaries of our solar system into the expanses of stars and nebule. We are transported intoa world of atoms, molecules, and hght-waves, where the standard of measurement is no longer in feet or inches, or even in one-hundred-thousandth part of an inch, but in millionths of millimetres, 2. €., 1M 95 000,000,000 of an inch. The dimensions are such that, as we shall see when we come to deal with matter, if the drop of water in which the microscope shows us living animalcula were magni- fied to the size of the earth, the atoms of which it is composed would. appear of a size intermediate between that of a rifle-bullet and a ericket-ball. This, then, is Nature’s scale of space, from millionths of a millime- treup to millions of millions of miles. Throughout the whole of this enormous range of space the laws of Nature prevail. Matter attracts matter by the same law of gravity in the case of double stars revolving about each other at a distance at which a base of 180,000,000 miles has long since become a vanishing point, and in the case of atoms which form the substance of a gas, as in that of an apple falling from a tree at the earth’s surface. Comets, darting off into the remote regions of space, return after long periods, in obedience to the samelaw. Clouds of meteoric dust revolve in fixed orbits, determined. by the law of gravity as surely as the moon revolves round the earth, and the earth round the sun. This is a conclusion of such fundamental importance that it is desirable to give the uninitiated reader some clear idea of what it means. and how itis arrived at. Newton’s great discovery, the law of gravity, is this—that all matter acting in the mass attracts other matter directly as the amount of attracting matter, and inversely as the square of the. distance. That is, 2 or 2,000,000 tons attract with twice the force of 1 or 1,000,000 tons at the same distance, but with only one-fourth of the same force at double, and one-ninth at triple the distance. How is this law proved? This will be best answered by explaining how it was discovered. The force of gravity, or attraction of the earth on bodies at the earth’s surface, is a known quantity. The whole. matter in a spherical body attracts exactly as if it were all collected at the centre. The force of gravity at the earth’s surface is, therefore, that of the earth’s mass exerted at a distance of about 4,000 miles, and. this can be easily measured by observing the space fallen through, and the velocity acquired, by a falling body in a given time, such as 1”. Does the same force act at the distance of the moon, or 207,200: miles? This was the question Newton asked himself, and the answer was got at in the following way. If we swing a stone in a sling round our head, it describes a circle as long as we keep the string tight, and. its pull inwards just balances the pull of the stone to fly outwards, 7.e., to use scientific language, as long as the centripetal just balances the centrifugal force. Butif we let go the string the stone darts off in the direction in which, and with the velocity with which, it was moving when the centripetal force ceased to act. The moon is such asling-stone revolving about the earth. At. each instant it is moving in the direction of a tangent to its orbit, and. would move on ina straight line along this tangent if it were not. deflected from it by some other force. That is, if the moon were now e SPACE. 15. at M,, it would, after a given interval of time, be at M, if no force had. acted on it. But in point of fact it is not at M, but at M;. Therefore it has been pulled down from M, to M,, or if you like, fallen through the space M, M,; in the time in which it would have ‘ Ms travelled over M, M, with its velocity at M, How does this space correspond with the space through which a heavy body would have fallen in the same time at the earth’s surface? It corresponds exactly, assuming the law of gravity to be, that it decreases with the square of the distance. This may be taken as the first approximation, but the more accurate and universal proofs of the law are derived from mathematical calculations of what the } nature of the attractions must be, in the case of the ® sun, earth, moon, and planets, to make them describe such elliptie orbits and observe such laws, as from Kepler’s observations we know actually to be the case. The answer here again is the law of gravity, and no other possible law, and this is confirmed in practice by the fact. that we are able, by calculations based on it, to satisfy the requisite of safe prophecy—that of knowing beforehand, and to predict eclipses, comets, transits, and occultations, and generally to compile Nautical Almanacs, by which ships know their whereabouts in pathless oceans. This, then, affords usa first firm standing-point in any specula- tions as to the nature of the universe. One great law, at any rate, is: universal throughout all space, and, as we shall see later, suns, stars, and nebule are composed of the same matter as the earth and its: inhabitants. In like manner comets and meteors, though presenting in other respects phenomena not yet fully understood, are proved to obey the same laws and to consist of the same matter. Comets are bodies which revolve round the sun, and are attracted by it and by the planets, in obedience to the ordinary law of gravity, though their density is so slight, that although often of enormous volume, they produce no per- ceptible effect on the planets, even when entangled amidst the satellites of a planet, as Lascelles’ comet was among those of Jupiter. Their dimensions may be judged of when it is stated that the comet of 1811 had a tail 120 millions of miles in length and 15 millions of miles in diameter at the widest part, while the diameter of the nucleus. was about 127,000 miles, or more than ten times that of the earth. In order that bodies of this magnitude, passing near the earth, should not affect its motion or change the length of the year by even a single second, their actual substance must be inconceivably rare. If the tail, for instance, of the comet of 1843 had consisted of the lightest sub- stance known to us, hydrogen gas, its mass would have exceeded that. of the sun, and every planet would have been dragged from its orbit. As Proctor says, therefore: “A jar-full of air would probably have out- weighed hundreds of cubic miles of that vast appendage which blazed. across the skies to the terror of the ignorant and superstitious.” The extreme tenuity of a comet’s mass is also proved by the phe- nomenon of the tail, which, as the comet approaches the sun, is thrown out sometimes to a length of 90 millions of milesin a few hours. And what is remarkable, this tail is thrown out against the force of gravity by some repulsive force, probably electrical, so that it always points. away from the sun. Thus a comet which approaches the sun with a 16 MODERN SCIENCE AND MODERN THOUGHT. tail behind it, will, after passing its.perihelion, recede fiom the sun with its tail before it, and this although the tail may be of the length of 200 millions of miles as in the comet of 1848. In the course of a few hours, therefore, this enormous tail has been absorbed and a new one started out in an opposite direction. And yet, thin as the matter of comets must be, it obeys the common law of gravity, and whether the comet revolves in an orbit within that of the outer planets, or shoots off into the abysses of space and returns only after hundreds of years, its path is, at each instant, regulated by the same force as that which causes an apple to fall to the ground; and its matter, however attenuated, is ordinary matter, and does not consist of any unknown elements. The spectroscope shows that comets shine partly by re- flected sunlight and partly by light of their own, the latter part being gaseous, and this gas, in most comets, contains carbon, hydrogen, and nitrogen, possibly also oxygen, in the form of hydrocarbons or marsh gas, cyanogen and possibly oxygen compounds of carbon. One comet has recently given the line of sodium, and the presence of iron is strongly suspected. As regards meteors, which include shooting stars and aérolites, it has been long known, from actual masses which have fallen on the earth, that they are composed of terrestrial matter, principally of iron, which has been partially fused by the heat engendered by the fiction of the rapid passage through the air. The recurrence of brilliant ‘displays at regular intervals, as for instance those of August and November, when the whole sky often seems alive with shooting stars, had also been noticed; but it was reserved for recent times to prove that these meteor streams are really composed of small planetary bodies revolving round the sun in fixed orbits by the force of gravity, and that their display, as seen by us, arises from the earth in its revolution round the sun happening to intersect some of these meteoric orbits, and the fiction of our atmosphere setting fire to and consuming the smaller meteors which appear as shooting stars. This shows the enormous number of meteors by which space must be tenanted. It is proved that the earth encounters more than a hundred meteor systems, but the chance of any one ring or system being intersected by the ‘earth is extremely small, as the earth is such a minute speck in the whole sun-surrounding space of the solar system. Ona scale on which the earth’s orbit was represented bya circle of 10 feet diameter, the earth itself would be only about ,,,th of an inch in diameter, so that if, as astronomers say, the earth encounters about a hundred meteor systems in the course of its annual revolution, space must swarm with ‘an innumerable number of these minute bodies all revolving round the sun by the force of gravity. Has this law of gravity been uniform through all time as it undoubtedly is through all space? We have every reason to believe so. The law of gravity, which is the foundation of most of what we call the natural laws of geological action, has certainly prevailed, as will be shown later, through the enormous periods of geological time, and far beyond this we can discern it operating in those astronomical changes by which cosmic matter has been condensed into nebule, nebule into ‘suns throwing off planets, and planets throwing off satellites, as they ‘cooled and contracted. We cannot speak with quite the same certainty of infinite time as we can of infinite space, for we have no telescopes to gauge the abysses of time, and no certain standards, like those of TIME. 17 the known dimensions of our solar system, to apply to periods too vast for the imagination. But we can say this with certainty, that the present law of gravity must have prevailed when the outermost planet of our system, Nep- tune, was condensed into a separate body and began revolving in its present orbit, and that it has continued to act ever since; while, as a matter of probability, it is as nearly certain as anything can be, that the law by which the apple falls to the ground is an original law of matter, and has existed as long as matter has existed. It certainly extends through all space. Double stars ata distance exceeding 20 millions of millions of miles revolve round their common centre of gravity by this law. Atoms and molecules almost infinitely smaller than millionths of millimetres derive from it their specific weights with as much certainty as if they were pounds or hundred- weights. What space and matter really may be, we do not know, and if we attempt to reason about their essence and origin, or quit the region of science based on fact, we get into the misty realms of metaphysics, where, like Milton’s fallen angels, we Find no end in wandering mazes lost. But this we do know of a certainty, that be matter and space what they may, they are subject to this one, uniform, all-pervading law; and attract, have always attracted, and will always attract, directly as the mass of the attracting matter and inversely as the square of the dis- tance in space at which the attraction acts. CHAPTER II. TIME. EKOLOGY has done for time what astronomy has for space—it \_ 3 _ihas expanded the limited ideas derived from natural impression and early tradition, into those of an almost infinite duration. This result is so important that it is desirable that all educated persons, without being professed geologists, should have some clear idea of the nature of the conclusions and of the evidences on which they rest. This I will endeavor to give. When we come to examine the structure of the earth—or rather of the outer crust of the earth which we inhabit—with the care and precision of scientific methods, we find that it is not of uniform com. position, but consists mainly of distinct layers, or strata, lying one over the other. This is true not only of the larger beds, or distinct formations, but of the details of each formation, many of which are built up as regularly as the layers of the Great Pyramid, while others are made up of layers no thicker than the leaves of a book. Now consider what this fact of stratification implies. In the first place it implies deposit from water, for there is no other agency by which materials can be sorted out and thrown down in horizontal layers, while this agency is now doing the same thing every day and all over the world. The Rhone flows into the lake of Geneva a turbid stream, and flows out of it as clear as crystal. All the matter it brings 18 MODERN SCIENCE AND MODERN THOUGHT. in is deposited at the bottom of the lake, and in course of time will fil} it up. This deposit varies with every alternation of flood and drought; the river depositing sometimes boulders and coarse gravel, sometimes shingle, sand, or fine mud, and carrying this material sometimes to a greater and sometimes to a less distance, according to the velocity of the stream. Ages hence, when the lake has been converted into dry land, it will be as certain, whenever a pit is dug or a well sunk in it, that it was. the work of a river flowing into a lake, as it is to-day, when we can see them at work. And what is true of the Rhone and the Lake of Geneva, is true on a larger scale of the Ganges, the Mississippi, and of every sea or ocean, with every river or torrent pouring into it. Again, the sea is perpetually wearing away the coasts of all lands, and, where the cliffs are soft and the tides and currents strong, at a very rapid rate. The materials swallowed up are rolled as shingle, ground into sand, or floated as fine mud, and all finally assorted and laid down at the bottom of the sea, not in a confused heap, but in regular succession. On some of them, shell-fish and other marine creatures live and die for generations, and their remains are covered. over by fresh sands or clays, and preserved for future geologists. All this is going on now, and when we examine the rocks we find that precisely the same sort of thing has been going on from the newest to the oldest strata. With the exception of a comparatively small amount, of igneous rock, which has boiled up from deep sources of molten. matter, and been poured out in sheets of lava, or masses of trap, porphyry, and granite, according to the amount of pressure it has. undergone and the time it has taken to cool and crystallize, all the earth’s surface may be said to consist of stratified matter, showing clear signs of having been deposited from water. Some of the oldest rocks, such as gneiss, may be a little doubtful, as they have clearly been subjected to great heat under great pressure, until they became plastic enough to crystallize as they cooled, and thus destroy any fossils. embedded in them and obliterate most of the ordinary signs of strati- fication. But the opinion of the best geologists is that they were originally stratified, and have become what is called ‘“‘metamorphic,” or changed by heat and pressure into the semblance of igneous rocks. But even if these are not included, enough remains to justify the general assertion that the outer crust of the earth, as known to us, is made up mainly of stratified materials which have been deposited from water. Now this implies another most important fact, viz., that there must. have been waste or denudation of existing land corresponding to the deposit of stratified materials under water. Water cannot generate these materials, and every square mile of such strata, say 10 feet thick, implies the removal of 10 feet from a square mile of land surface by rains and rivers, or of an equivalent amount of cubical content in some: other way, as by the erosion of a coastline. This is a very important consideration when we come to estimate the time required for the formation of such a thickness of stratified beds as we find existing. There must have been a fundamental crystalline rock as the earth cooled down from a fluid state and acquired a solid crust, and this rock must have been worn down by primeval seas and rivers as the: progressive cooling admitted of the condensation of aqueous vapor into e TIME. 19 water. The waste of this primitive crust must have been deposited in strata at the bottom of those seas in thick masses, covering the original rock, and these again must have been partly crystallized by heat and pressure, and over and over again upheaved and submerged, and themselves worn down by fresh erosion, forming fresh deposits which underwent a repetition of the same process. A third important inference from the fact of stratification is that. all strata must have been originally deposited horizontally, or very nearly so, and in such order that the lowest is the oldest. Suppose we fill a jar with water, and put some white sand into. it, and when that has subsided to the bottom and the water is clear, some yellow sand, and again some red sand, it is clear that we shall have at the bottom of the jar three horizontal deposits or strata, one: white, one yellow, and one red, and that by no conceivable means can the order in which they were deposited have been other than first. white, secondly yellow, and lastly red. This law, therefore, is invaria- ble, that wherever it is possible to trace a series of strata lying one above the other, the lowest is the oldest, and the highest the youngest. in point of time. If, therefore, all the great formations, from the old Laurentian up to the newest Tertiary, had been deposited uniformly all over the world, and had remained undisturbed, and we could have seen them in one vertical section in a cliff twenty-five miles high—for that is. about their total known thickness—we should have been able without. further difficulty to determine their order of succession and respective magnitudes. But this is plainly impossible, for the deposits going on at any one time are of very different character. For instance, we have at: present the Globigerina ooze gradually filling the depths of the Atlan- tic with a deposit resembling chalk; the Gulfs of Bengal and Mexico silting up with fine clay from river deposits; vast tracts in the Pacific, Indian Ocean, and Red Sea, covered with coral and the dédris of coral- reefs. How could these, if upheaved into dry land and explored by future geologists, be identified as having been formed contempora- neously ? Suppose that coins of Victoria had been dropped in each of them, the geologist who discovered these coins would have no difficulty in concluding that the strata in which they were found were all formed in the nineteenth century. The petrified shells and other remains: found in geological strata are such coins. Hvery great formation has: had its own characteristic fauna and flora, or aggregate of animal and vegetable life, varying slowly from one geological age to another, and. linked to the past and future by some persistent types and forms, but. still with such a preponderance of characteristic fossils as to enable. us to assign the rocks in which they occur to their proper place in the volume of the geological record. Innumerable observations have shown that wecan rely, with absolute confidence, on the fossils: embedded in the different strata of the earth’s crust as tests of the period to which they belong, however different the strata may be in mineral composition. The next question is how we can ascertain the thickness and order of succession of these strata. We have seen that all stratified rocks were originally deposited from water and therefore horizontally. Had they remained so, in the first place the process of forming strati- 20 MODERN SCIENCE AND MODERN THOUGHT. fied rocks must long ago have come to an end, for all the land surface must have been worn down to the sea level, and with no more land to be- denuded, deposition must have ceased at an early period of the earth’s history. And, in the second place, we could have known nothing more of the earth’s crust than we saw on the surface, and in the shallow pits and borings we could sink below it. But earthquakes and volcanoes, and the various fractures and pressures due to sub- terranean heat and secular contraction and cooling, have been at work counteracting the effects of denudation, and causing elevations and depressions by which the inequalities of the earth’s surface have been renewed, the balance between sea and land maintained, and strata, originally horizontal at the bottom of the ocean, upheaved until sea- shells are found at the top of high mountains, and we can walk for miles over their upturned edges. 7 Any one who wishes to understand how geologists have been able to measure such a thickness of the earth’s crust, has only to take a book open at page 1 and lay it flat before him. Hecan see nothing but that one page; but if he turns up the pages on the right-hand side of the book until their edges become horizontal, he can pass over them and count perhaps 500 pages in the space of a coupie of inches. This is precisely what geologists have been able to do at various points of the earth’s surface where the upturned edges of the pages of its history are exposed, and they come out, one behind the other, in the due succession in which they were written by Nature. For instance, in travelling from east to west in England we pass continu- ally from newer to older formations—Chalk comes in from below Tertiary; Oolite and Lias from below Chalk; then Permian or New Red Sandstone; Carboniferous, including the Coal measures; Devonian or Old Red Sandstone; Silurian, Cambrian, and in the extreme north-west ~-of Scotland and the Hebrides, oldest of all the Laurentian. There are some omissions and interpolations, but, in a general way, it may be said that within the bounds of the British Empire we have such a view of Nature’s volume as would be got, in the case L have supposed, by travelling over its upturned edges from page 1 to page 500. And if each of the great formations be taken as a separate chapter, each chapter will be found to be made up of anumber of pages, each with its own letter-press and illustrations, though connected with the pages before and after it by the thread of the continuous common subject of their proper chapter; as the chapters again are connected by the continuous common subject-matter of the complete volume. It must not be supposed that the volume is anything like perfect. We have to piece it together from fragments found in the limited number of countries which have thus far been scientifically explored, and which do not constitute more than a small part of the earth’s surface. We know nothing of what is below the oceans which cover three-fourths of that surface, and there are great gaps in the record during times ‘when portions of the surface were dry land, and consequently no deposit of strata or preservation of fossils was possible. Still a great ‘deal has been accomplished, and the general result, as given by common consent of the best geologists, is as follows: The total thickness of known strata is about 130,000 feet or twenty- five miles, or the ,,th part of the distance from the earth’s surface to its centre. Of this, about 30,000 feet belong to the Laurentian, which is the oldest known stratified deposit; 18,000 to the Cambrian, and TIME. 21 22,000 to the Silurian. These form together what is known as the Primary or Palzozoic Epoch. In the lowest, the Laurentian, the only faint trace of life. discov- ered is that of the Hozoon Canadense, which is considered to be an undoubted petrifaction of a foraminiferous living organism with a cham- bered shell. It must be remembered, however, that these earliest formations have been so changed by slow crystallization under great heat and pressure that all fossils and nearly all traces of stratification must have been obliterated. In the Cambrian and Lower Silurian traces of life become more frequent, especially of low forms of sea-weeds, and in the Upper Silurian we find.an abundance of life, consisting of crustacea, shell-fish, and a few true fish in the upper strata. Some of these shells, as the Lingula, have continued without much change up to the present time; and on the whole we find ourselves in the Silurian period, if not earlier, in presence of a state of things in which substantially present causes operated and present conditions were in force. Rains fell, winds blew, rivers ran, waves eroded cliffs, shell-fish lived and died, and crabs and sand-worms crawled about on shores left dry by each tide, very much as is the case at present. The next great divison, which got the name of Primary before the existence of fossils was known in the older or Paleozoic division, com- prises the Devonian or Old Red Sandstone; the Carboniferous which includes the coal; and the Permian or New Red Sandstone. | The aver- age thickness of these three systems taken together is about 42,000 feet. It may be called the era of Fern Forests and of Fish, the former being the principal source of our supplies of coal, and the latter being extremely abundant within the Devonian and Permian formations. The third great division is formed by the Secondary group, which includes the Triassic, the Jura, and the Cretaceous or Chalk systems, and has an average thickness of about 15,000 feet. This epoch is emphatically the age of Reptiles as the preceding one was that of Fish, and the prevailing vegetation is no longer one of ferns and mosses, but of Gymnosperms, or plants having naked seeds, the most important class of which is that of the Coniferze or Pine tribe. Dur- ing this period the Plesiosauri, Ichthyosauri, and other gigantic sea- dragons abounded in the oceans; colossal land-dragons, such as the Dinosauri, occupied the continents, and Pterodactyls, a remarkable form of carnivorous flying lizards, ruled the air. Swarms of other reptiles, nearly related to the present lizards, crocodiles, and turtles, abounded both in the sea and land. A few traces of mammals and birds show that these orders had then come into existence, just as a few traces of reptiles are found in the Primary and of fish in the Paleozoic strata, but the few mammalian remains found are of small animals of the marsupial or lowest type, and the birds are of a transi- tion type between reptiles and true birds. This epoch concludes with the Chalk formation, which is one of deep-sea deposit, where no trace of terrestrial life can be expected. Above this comes the Tertiary epoch, when the present order, both of vegetable and animal life, is fairly inaugurated; mammals predominate over other forms of vertebrate animals; existing order, and species begin to appear and increase rapidly; and vegetation 22 MODERN SCIENCE AND MODERN THOUGHT. consists mainly of Angiosperms, or plants with covered seeds, as in our present forests. The total thickness of these strata, from the lowest or Eocene, to the end of the uppermost or Pliocene, is about 3,000 feet. Above this comes the Quarternary, or recent period, which comprises the superficial strata of modern formation, and is character- ized by the undoubted existence of man and of animal species, which either now exist or have become extinct in quite recent geological times. The details of this and of the Tertiary Epoch will be more fully considered when we come to treat of the antiquity of man, with which they are closely connected. But for the present object, which is that of ascertaining some standard of time for the immense series of ages proved by geology to have elapsed since the earth assumed its present condition, became subject to existing laws and fitted to be the abode of life, it will be sufficient to refer to the older strata. The best idea of the enormous intervals of time required for geological changes will be derived from the coal measures. These consist of part only of one geological formation known as the Carboniferous. They are made up of sheets or seams of condensed vegetable matter, varying in thickness from less than an inch to as much as thirty feet, and lying one above another, separated by beds of rocks of various composition. As a rule, every seam of coal rests upon a bed of clay, known as the ‘“under-clay,” and is covered by a bed of sandstone or shale. These alternations of clay, coal, and rock, are often repeated a great many times, and in some sections in South Wales and Nova Scotia, there are as many as eighty or a hundred seams of coal, each withits own under-clay below and sandstone or shale above. Some of the coal seams are as much as thirty feet thick, and the total thickness of the coal measures is, in some cases, as much as 14,000 feet. Now consider what these facts mean. Every under-clay was clearly once a surface soil on which the forest vegetation grew, whose accumulated débris forms the overlying seam of coal. The under-clays are full of the fibres of roots, and the stools of trees which once grew on them, are constantly found in situ, with their roots attached just as they stood when the tree fell, and added to the accumulation of vegetable matter, which in modern times forms peat, and in more ancient days, under different conditions of heat and pressure, took the more consolidated form of coal. When these vegetable remains are examined with the aid of the microscope it is found that these ancient forests consisted mainly of trees like gigantic club-mosses, mares’-tails, and tree ferns, with a few resembling yews and firs. But in many cases the bulk of the coal is composed of the spores and seeds of these ferns and club-mosses, which were ripened and shed every year, and gradually accumulated into a vegetable mould, just as fallen leaves, beech-mast, and other débris gradually form a soil in our existing forests. The time required must have been very great to accumulate vegetable matter, principally composed of fine spore dust, to a depth sufficient under great compression to give even a foot of solid coal. Dr. Dawson, who has devoted great attention to the coal-fields of America, says: ‘‘ We may safely assert that every foot of thickness of pure bituminous coal implies the quiet growth and fall of at least fifty generations of Sigillaria, and therefore an undisturbed condition of ary TIME. 23 forest growth, enduring through many centuries.” But this is only the first step in the measure of the time required for the formation of the coal measures. Each seam of coal is, as we have seen, covered ‘by a bed of sand or shale, z.e¢., of water-borne materials. How can this be accounted for? Evidently i in one way only—that the land sur- face in which the forest grew subsided gradually until it became first amarsh, and then a lagoon or shallow estuary, which silted up by degrees with deposits of sand or mud, and, finally, was upraised until its surface became dry land, in which a second forest grew, whose débris formed a second coal seam. And so on, over and over again, until the whole series of coal measures had been accumulated, when this alternation of slight submergences and slight rises came to an end, and some more decided movement of the earth’s surface in the locality brought on a different state of things. This isin fact exactly what we see taking place on a smaller scale in recent times in such deposits as those of the delta of the Mississippi, where a well sunk at New Orleans passes through a succession of cypress swamps and forest growths, exactly like those now growing on the surface, which are piled one above the other, and separated by deposits of river silt, showing a long alternation of periods of rest when forests grew, fol- lowed by periods of subsidence when they were flooded and their remains were embedded in silt. Starting on Dr. Dawson’s assumption that one foot of coal represents fifty generations of coal plants, and that each generation of coal plants took ten years to come to maturity, an assumption which is certainly very moderate, and taking the actually measured thickness of the coal measures in some localities at 12,000 feet, Pro- fessor Huxley calculates that the time represented by the Coal forma- tion alone would be six millions of years. Such a figure is, of course, only a rough approximation, but it is sufficient to show that when we come to deal with geological time, the standard by which we must measure is one of which the unit is a million of years. This standard is confirmed by a variety of other considerations. Take the case of the Chalk formation. Chalk is almost entirely composed of the microscopic shells of minute organisms, such as now float in the upper strata of our great oceans, and by their subsidence, in the form of an impalpable shell- dust, accumulate what is called the “Globigerina ooze,” which is brought up by soundings in the Atlantic and Pacific from great depths. In fact, we may say that a chalk formation is now going on in the depths of existing oceans, and conversely that the old chalk, which now forms hills and elevated downs, was certainly deposited at the bottom of similar deep oceans of the Cretaceous period. The rate of deposit must have been extremely slow, certainly much slower than that of the deposit of the much grosser matter brought down by the Nile in its annual inundations, the growth of which has been estimated from actual measurement at about three inches per cen- tury. If one inch per century were the rate of accumulation of this microscopic shell-dust, subsiding slowly to depths of two or three miles over areas as large as Europe, it would take 1,200 years to form a foot of chalk, and 1,200,000 years to form 1,000 feet. Now there are places where the thickness of the Cretaceous formation, exposed by the edges of its upturned strata, exceeds 5,000 feet, so that this gives an approximation eae similar to that furnished by the coal lueasures. 24 MODERN SCIENCE AND MODERN THOUGHT. We have thus, on a rough approximation, a minimum period of about 6,000,000 years for the accumulation of a single member: of one of the separate formations into which the total 180,000 feet of measured strata are subdivided. But this takes no account of the lone periods during which no accumulation took place at the localities in question, and of the long pauses which must have ensued between each movement of elevation and submergence, and especially between the disappearance of an old and appearance of an almost entirely new epoch, with difterent forms of animal and vegetable life. We may be certain also that weare far from knowing the total thickness of strata which will be disclosed when the whole surface of the earth comes to be explored. All we can say is that we have fragmentary pages left in the geological record for, at the very least, 100 millions of years, and that probably the lost pages are quite as numerous as those of which we have an imperfect knowledge. Sir Charles Lyell, the highest authority on the subject, is in- clined to estimate the minimum of sreological time at 200 millions of years, and few geologists will say thas his estimate appears excessive. Another test of the vast duration of geological time is afforded by the oscillations of the earth’s surface. At first sight we are apt to consider the earth as the stable and the sea as the unstable element. But in reality it is exactly the reverse. Land has been perpetually rising and falling while the level of the sea has remained the same. This is easily proved by the presence of sea-shells and other marine. remains in strata which now form high mountains. In the case of chalk, for instance, there must have been in England a change of relative level of sea and land or more than two miles of vertical height, between the original formation of the chalk at the bottom of a deep ocean and its present position in the North and South Downs. In other cases the change of level is even more conspicuous. The Num- mulite limestone, which is formed like chalk from an accumulation of the minute shells of low organisms floating in the oceans of the early Tertiary period, is found in mountain masses, and has been elevated to a height of 10,000 feet and more in the Alps and Himalayas. On a smaller scale, and in more recent times, raised beaches with. existing shells and lines of cliffs and caves, are found at various heights above the existing sea-level of many of the coasts of Britain, Scandi- navia, Italy, South America, and other countries. Now the first question is, were these changes caused by the land rising or by the sea falling? The answer is, by the land rising Had they been caused by the sea standing at a higher level it must have stood everywhere at this level, at any rate in the same hemisphere and anywhere near the same latitude. But there are large tracts of land which have never been submerged since remote geological periods; and in recent times there is conclusive evidence that the changes of level of sea and land have been partial and not general. Thusin the well-known instance of the columns of the ruined temple of Serapis at. Pozzuoli in the Bay of Naples, which forms the illustration on the. title-page of Lyell’s “Principles of Geology,” there can be no doubt. that since the temple was built, either the sea must have risen and since fallen, or the land sunk and since risen, at least twenty feet since the temple was built less than 2,000 years ago, for up to this height the marble columns are riddled by borings of marine shells, whose valves. ¢ TIME. 5: are still to be seen in the holes they excavated. But an elevation of: the level of the Mediterranean‘of twenty feet would have submerged a great part of Egypt, and other low-lying lands on the borders of that sea, where we know that no such irruptions of salt water have taken place within historical, or even within recent geological times. The conclusion is therefore certain, that the land at this particular: spot must have sunk twenty feet, and again risen as much, so as to bring back the floor of the temple t to its present position, which stood. one hundred years ago just above the sea-level, and that so gradually as not to throw down the three columns which are still standing. A. slow subsidence has since set in and is now going on, so that the floor is now two or three feet below the sea-level. Similar proofs may be multiplied to any extent. Along the coasts of the British Islands we find, in some places submarine forests show- ing subsidence, in others raised beaches showing elevation, but they are not continuous at the same level. Along the east coast of Scotland. there is x remarkable raised beach at a level of about twenty-four feet above the present one, showing in many places lines of cliff, sea-worn. caves, and outlying stacks and skerries, exactly like those of the present coast, though with green fields or sandy links at their base, instead of the waves of the German Ocean. But as we go north this. inland cliff gets lower and gradually dies out, and when we get into the extreme north, among the Orkney and Shetland Islands, there are no signs of raised beaches, and everything points towards the recent. period having been one of subsidence. Again, in Sweden, where marks were cut in rocks in sheltered situations on the tideless Baltic more than a century ago, so as to test. the question of an alleged elevation of the land, it has been clearly shown that, in the extreme north of Sweden, the marks have risen. nearly seven feet, while in the central portion of the country they have neither risen nor fallen, and in the southern province of Scania they have fallen. This would be clearly impossible if the sea and not the land had. been the unstable element, and apparent elevations and depressions had been due to a general fall or rise in the level of all the seas of the. northern hemisphere. In fact, the more we study geology the more we are impressed with the fact that the normal state of the earth is, and has always been, one of incessant changes. Water, raised by evaporation from the seas, falls as rain or snow on land, wastes it away and carries it. down from higher to lower levels, to be ultimately deposited at the bottom of the sea. This goes on constantly, and if there were no compensating action, as the seas cover a much larger area than the lands, all land would ultimately disappear, and one universal ocean cover the globe. But inward heat supplies the compensating action, and new lands rise and new mountain chains are upheaved to supply the place of those which disappear. This inward heat of the earth is not a mere theory but an ascertained fact; for as we descend from the surface in deep mines or borings, we find the temperature actually does increase at a rate which varies somewhat in different localities, but which averages about uy Fahrenheit for every 60 feet of depth. At this rate of increase water would boil at a depth of 10,000 feet, and iron and all other metals be melted before we reached 100,000 feet. What actually occurs at great. 26 MODERN SCIENCE AND MODERN THOUGHT. lepths we do not know with any certainty, for we are not sufficiently acquainted with the laws under which matter may behave when under enormous heat combined with enormous pressure. But we do know from voleanoes and earthquakes that masses of molten rocks and of imprisoned gases exist in certain localities, at depths below the surface which, although large compared with our deepest pits, are almost ‘infinitesimally small compared with the total depth of 4,000 miles from that surface to the earth’s centre. This much is clear, that, in order to account for observed facts, we must consider the extreme outer crust, or surface of the earth as known to us, as resting on something which is liable to expand and contract slowly with variations of heat, and occasionally, when the tension becomes great, to give violent shocks to the outer crust, send- ‘ing earthquake waves through it, and to send up gases and molten lava through volcanoes, along lines of fissure, and at points of least resistance. itis clear, also, that these movements are not uniform, but that one part of the earth’s surface may be rising while another is sinking, and portions of it may be slowly tilting over, so that as one end sinks the other rises. The best comparison that can be made is to a sheet of ice which -has been much skated over and cracked in numerous directions, so as to have become a sort of mosaic of ice fragment, which, when a thaw -sets in and the ice gets sloppy, rise and fall with slightly different ‘motions as a skater, gliding over them, varies the pressure, and occasionally give a crack and let water rise through from below in the line of fissure. The difficulty will not seem so great if we consider that the rocks which form the earth’s crust are for the most part elastic, and that an amountof elevation which seems large in itself does not necessarily imply a very steep gradient. Thus, if the elevation which towards the close of the Glacial period carried a bed of existing ‘sea-shells of Arctic type to the top of the hill, Moel Tryfen, in North Wales, which is 1,200 feet high, were, say one of 1,500 feet, this would be given by a gradient of 15 feet a mile, or 1in 333 for 100 miles. Such a gradient would not be perceptible to the eye, and would certainly not be sufficient to cause any tension likely to rupture rocks or disturb strata. Such movements are as arule extremely slow. In volcanic regions there are occasionally shocks which raise extensive regions a few feet at a blow, and partial elevations and subsidences which throw up cones .of lava and cinders, or let mountains down into chasms, in a single explosion. The most noted of these are the instances of Monte Nuovo, near Naples, 800 feet high, and Jorullo, in Mexico, thrown up in one eruption, and the disappearance the other day of a mountain 2,000 feet ‘high in the Straits of Sunda during an earthquake. The largest rise recorded of an extensive area from the shock of an earthquake, is that which occured in South America in 1835, when a range of coast of 500 miles from Copiapo to Chiloe was permanently raised five or six feet by a single shock, as was shown by the beds of dead mussels and other ‘shells which had been hoisted up in some places as much as ten feet. It is probable that the great chain of the Andes, whose highest sum- mits reach 27,000 feet, has been raised in a great measure by a ‘succession of similar shocks. But for the most part these movements, whether of elevation or -depression, go on so slowly and quietly that they escape observation ® LIIME. 27 Scandinavia is apparently now rising and Greenland sinking, but most countries have remained appreciably steady, or nearly so, during the historical period. St. Michael’s Mount, in Cornwall, is still connected with the mainland by a spit, dry at ebb tide and coveredat flood, as it ‘was more than 2,000 years ago when the old Britons carted their tin across to Phoenician traders. Egypt, during a period of 7,000 years, has preserved the same level, or at the most has sunk as slowly as the Nile mud has accumulated. Parts of the English and Scotch coast have risen perhaps twenty feet since the prehistoric period, when canoes were wrecked under what are now the streets of Glasgow, and whales were stranded in the Carse of Stirlng. There is even some evidence that the latest rise may have occurred since the Roman wall was built from the Forth to the Clyde. In any case, however, the movements have been extremely slow, and there have .been frequent oscillations, and long pauses when the level of land and sea remained stationary. The evidence, therefore, from the great changes which have occurred during each geological period, points to the same conclusion as that drawn from the thickness of formations, such as the coal measures and chalk, which must have been accumulated very slowly, viz., that geological time must be measured by a scale of millions of years. Another test of the vast duration of geological time is afforded by the changes which have taken place in animal life as we pass from one formation to another, and even within the limits of the same formation. The fauna, or form of existing life at a given period, changes with extreme slowness. During the historical period there has been no perceptible change, and even since the Pliocene period, which cannot be placed at a less distance from us than 200,000 years, and probably at much more, the change has been very small. In the limited class of large land animals it has been considerable; but if we take the far more numerous forms of shell-fish and other marine life, the old species which have become extinct and the new ones which have appeared, do not exceed five per cent. of the whole. This is the more remarkable as great vicissitudes of climate and variations of sea-level have occurred during the interval. The whole of the Glacial period has come and gone, and Britain has been by turns an archipelago of frozen islands, and part of a continent extending over what is now the German Ocean, and pushing out into the Atlantic up to the one hundred fathom line. Reasoning from these facts, assuming the rate of change in the forms of life to have been the same formerly, and summing up the many complete changes of fauna which have occurred during the separate geological formations, Lyell has arrived at the conclusion that geology requires a period of not less than 200 millions of years to account for the phenomena which it discloses. Long as the record is of geological time, it is only that of one short chapter in the volume of the history of the universe. Geology only begins when the earth had cooled down into a state resembling the present; when winds blew, rains fell, rivers and seas eroded rocks and formed deposits, and when the conditions were such that life became possible by the remains of which those deposits can be identified. But before this period began, which may be called that of the maturity or middle age of our planet, a much vaster time must be allowed for the contraction and cooling of the vaporous ether or cosmic matter of which it is formed, into the state in which the 28 MODERN SCIENCE AND MODERN THOUGHT. phenomena of geology became possible. Andif vast in the case of the earth, how must vaster must be the life periods of the larger planets, such as Jupiter, which from their much greater size cool and contract much more slowly, and are not yet advanced beyond the stage of intense youthfui heat and glowing luminosity which was left behind by our earth a great many tens of millions of years ago! And how vastly vaster must be that of the sun, whose mass and volume exceed those of Jupiter in a far higher ratio than Jupiter surpasses. the earth! And beyond all this in a third degree of vastness come the life periods of those stars or distant suns, which we know to be in some cases aS much as three hundred times larger than our sun, and not. nearly so far advanced as it in the process of emergence from the fiery nebulous into the solar stage. To give some idea of the vast intervals of time required for these changes, a few facts and figures may be given. One of the latest speculations of mathematical science is that the rotation of the earth is becoming slower, or in other words the day becoming longer, owing to the retarding action of the tides, which _act as a brake on a revolving wheel. If so, mathematical calculation shows that the effect of the reaction on the moon of this action of the moon on the earth, must be that as the earth rotates more slowly, the moon recedes toa greater distance. And vice versd, when the earth rotated more rapidly the moon was nearer to it, until at length, when the process is carried back far enough, we arrive at a time when the moon was at the earth’s surface and the length of the day about. three hours. In this state of things the moon is supposed to have been thrown off from the earth, either by one great convulsion, or, more probably, by small masses at a time forming a ring like that of Saturn, which ended by coalescing into a single satellite. With ‘the moon, which is the principal cause of the tides, so much nearer the earth, their rise and fall must have been something enormcus, and. huge tidal waves like the bore of the Bay of Fundy, but perhaps 500 or 1,000 feet high, must have swept twice during each revolution of the earth on its axis, ¢.¢., twice every three or four hours, along all the narrower seas and channels and over all except the mountainous lands adjoining. Now these conclusions may be true or not as regards phases of the earth’s life prior to the Silurian period, from which downwards. geology shows unmistakably that nothing of the sort, or in the least degree approaching to it, has occurred. But what I wish to point. out is that all this superstructure of theory rests on a basis which really does admit of definite demonstration and calculation. Halley found that when eclipses of the sun, recorded in ancient annals, are compared with recent observations, a discrepancy is discov- eredin the rate of the moon’s motion, which must have been slightly slower then than it is now. Laplace apparently solved the difficulty by showing that this was an inevitable result of the law of gravity, when the varying eccentricity of the earth’s orbit was properly taken into account; and the calculated amount of the variation from this cause. was shown to be exactly what was required to reconcile the observa- tions. Butour great English mathematician, Adams, having recently gone over Laplace’s calculations anew, discovered that some factors in the problem had been omitted, which reduced Laplace’s acceleration of ITME. 29 the moon’s motion by about one-hal’, leaving the other half to be explained by a real increase in the length of the sidereal day, or time of one complete revolution of the earth about ils axis. The retarda- tion required is one sufficient to account for the total accumulated Icss of an hour and a quarter in 2,000 years; or in other words, the length of the day is now more by about sith part of a second than it was 2,000 years ago. At this rate it would require 168,000 years to make a difference of 1 second in the length of the day; 10,080,000 years for a difference of 1 minute; and 604,800,000 years for a difference of 1 hour. The rate would not be uniform for the past, for as the moon got nearer it would cause higher tides and more retardation; still, the abyss of time seems almost inconceivable to get back to the state in which the earth could have rotated in three hours and thrown off the moon. It is right, however, to state that all mathematical calculations of time, based on the assumed rate at which cosmic matter cools into suns and planets, and these into solid and habitable globes, are in the high- est degree uncertain. If the original data are right, mathematical calculation inevitably gives right conclusions. But if the data are wrong, or what is the same thing, partial and imperfect, the conclusions will, with equal certainty, be wrong also. Now in this case we certainly do not know “the truth, the whole truth, and nothing but the truth” respecting these processes. ‘Take what is perhaps the most difficult problem presented by science—how the sun keeps up so ' uniformly the enormous amount of heat which itis constantly radiat- ing into space. This radiation is going on in every direction, and the solar heat received by the earth is only that minute portion of it which is intercepted by our little speck of a planet. All the planets together receive less than one 230,000,000th part of the total heat radiated away by the sun and apparently lost in space. Knowing the amount of heat from the sun's rays received at the earth’s surface in a given time, we can calculate the total amount of heat radiated from the sun in that time. It amounts to this, that the sun in each second of time parts with as much heat as would be given out by the burning of 16,436 millions of millions of tons of the best anthracite coal. And radiation certainly at this rate, if not a higher one, has been going on ever since the commencement of the geological record, which must certainly be reckoned by a great many tens of millions of years. What an illustration does this afford of that apparent ‘waste of Nature” which made Tennyson ‘falter where he firmly trod” when he came to consider “her secret meaning in her deeds!” Yet there can be no doubt that vast as these figures are, they are all the result of natural laws, just as we find the law of gravity prevailing throughout space at distances expressed by figures equally ‘vast. The question is, what laws? The only one we know of at present at all adequate to account for such a generation of heat, is the trans- formation into heat of the enormous amount of mechanical force or energy, resulting from the condensation of the mass of nebulous matter from which the sun was formed, into a mass of its present dimensions. Thisis no doubt a true cause as far as it goes. Itis true that as the mass contracts, heat would be, so to speak, squeezed out of it, very much as water is squeezed out of a wet sponge by compressing it. But it is a question whether it is the sole and ‘sufficient cause. Mathematicians have calculated that even if we 30 MODERN SCIENCE AND MODERN THOUGHT. suppose the original cosmic matter to have had an infinite extension, its condensation into the present sum would only have been sufficient to keep up the actual supply of solar heat for avout 15 millions of years. Of this a large portion must have been exhausted before the earth was formed asa separate planet, and had cooled down into a habitable globe. But even if we took the whole it would be altogether insuf- ficient. Ail competent geologists are agreed in requiring at least 100 millions of years to account for the changes which have taken place in the earth's surface since the first dawn of life recorded in the older rocks. Various attempts have been made to reconcile the discrepancy. For instance, it has been said that the constantly repeated impact of masses of meteoric and cometic matter falling into the sun must have caused the destruction of a vast amount of mechanical energy which would be converted into heat. This is true as far as it goes, but it is. impossible to conceive of the sun asa target kept ata perpetual and uniform white heat for millions of years by a rain of meteoric bullets. constantly fired upon it. More plausibly it is said that we know nothing of the interior constitution of the sun, and that its solid nucleus may be vastly more compressed than is inferred from the dimensions of its visible disc, which is composed of glowing flames and vapors. This also may be a true cause, but, after making every allowance, we must fall back on the statement that the continuance for such enormous periods of such an enormous waste of energy as is given out by the sun, though certainly explainable by laws of Nature, depends on laws not yet thoroughly understood and explained. Even in the case, comparatively small and near to us, of the earth, the condition of the interior and the rate of secular cooling afford prob- lems which as yet wait for solution. The result of a number of careful experiments in mines and deep sinkings shows that the temperature, as we descend below the shallow superficial crust which is affected by the seasons, z. €., by the solar radiation, increases at the average rate of 1° Fahrenheit for every 60 feet of depth. Thatis the average rate, though it varies a good deal in different localities. Now, at this rate we should soon reach a depth at which all known substances would be melted. But astronomical considerations, derived from the Precession of the Equinoxes, favor the idea that the earth is a solid and not a fluid body, and require us inany case toassume a rigid crust of not less than ninety miles in thickness. Andif the wholeearth below a thin super- ficial crust were in an ordinary state of fluidity from heat, it is difficult to see how it could do otherwise than boil, that is, establishing circulat- ing currents throughout its mass with disengagement of vapor, in which case the surface crust must be very soon broken up and melted down, just as the superficial crust of a red-hot stream of lava is, if an infusion of fresh lava raises the stream below to white heat, or as a thin film ofice would be if boiling water were poured in below it. All we can say is, that the laws under which matter behaves under conditions of heat, pressure, chemical action, and electricity so totally different as must prevail in the interior of the earth, and 4 fortioré in. that of the sun, are as yet very partially known tous. In the mean- time the safest course is to hold by those conclusions of geology which, as faras they go, depend on laws really known to us. Yor instance, the quantity of mud carried down in a year by the Ganges or Missis- eres L210 Le. dL sippi, isa quantity which can be calculated within certain approximate: limits. We can tell with certainty how much the deposit of this. amount of mud would raise an area, say of 100 square miles, and how long it would take, at this rate, to lower the area of India drained by the Ganges, a sufficient number of feet to give matter enough to fill up: the Gulf of Bengal. Andif among the older formations we find one, like the Wealden for instance, similar in character to that now forming by the Ganges, we can approximate from its thickness to the time. that may have been required to form it. In calculations of this sort there is no theory, they are based on positive facts, limited only by a certain possible amount of error either way. In short, the conclusions of geology, at any rate up to the Silu- rian period when the present order of things was fairly inaugurated, are. approximate facts and not theories, while the astronomical conclusions: are theories based on data so uncertain, that while in some cases they give results incredibly short, like that of 15 millions of years for the: whole past process of the formation of the solar system, in others they give results almost incredibly long, as in that which supposes the moon to have been thrown off when the earth was rotating in three hours, while the utmost actual retardation claimed from observation would require 600 millions of years to make it rotate in twenty-three hours: instead of twenty-four. To one who looks at these discussions between geologists and . astronomers not from the point of view of a specialist in either science, but from that of a dispassionate spectator, the safest course, in the present state of our knowledge, seems to be to assume that geology really proves the duration of the present order of things to have been. somewhere over 100 millions of years, and that astronomy gives am enormous though unknown time beyond in the past, and to come in the future, for the birth, growth, maturity, decline, and death of the solar system of which our earth is a small planet now passing through the habitab’e phase. So far, however, as the immediate object of this work is concerned, viz., the bearings of modern scientific discovery on modern thought, it. is not very material whether the shortest or longest possible standards. of time are adopted. The conclusions as to man’s position in the uni- verse and the historical truth or falsehood of old beliefs, are the same whether man has existed in astate of constant though slow progression for the last 50,000 years of a period of 15 millions, or for the last 500,- 000 years of a periodof 150 millions. It is a matter of the deepest scientific interest to arrive at the truth, both as to the age of the solar system, the age of the earth as a body capable of supporting life, the successive orders and dates at which life actually appeared, and the manner and date of the appearence of the most highly organized form: of life endowed with new capacities for developing reason and conscience in the form af Man. Those who wish to prove themselves worthy of their great good luck in having been born in acivilized country of the nineteenth century, and notin Paleolithic periods, will do well to show that curiosity, or appetite for knowledge, which mainly distinguishes: the clever from the stupid and the civilized from the savage man, by studying the works of such writers as Lyell, Huxley, Tyndall, and Proctor, where they will find the questions here only briefly stated, developed at fuller length with the most accurate science and in the clearest and most attractive style. But for the moral, philosophical, Oo MODERN SCIENCE AND MODERN THOUGHT, cand religious bearings of these discoveries on the current of modern thought, there is such a wide margin that it becomes almost immaterial whether the shortest possible or longest possible periods should be ultimately established. CHAPTER III. MATTER. HAT is the material universe composed of? Ether, Matter, and Energy. Etheris not actually known to us by any test of which the senses can take cognizance, butis a sort of mathematical substance which we are compelled to assume in order to account for the phenomena of light and heat. Light, as we have seen, radiates in all directions from a luminous centre, travelling at the rate of 184,000 miles per second. Now what is light? It is a sensation produced on the brain by some- thing which has been concentrated by the lens of the eye on the retina, and then transmitted along the optic nerve to the brain, where it sets ‘certain molecules vibrating. What is the something which produces this effect? Is it a succession of minute particles, shot like rifle-bullets from the luminous body and impinging on the retina as on a target? Or is it asuccession of tiny waves breaking on the retina as the waves ‘of the sea break on the shore? Analogy suggests the latter, for in the case of the sister sense, Sound, we know as a fact that the sensation is produced on the brain by waves of air concentrated by the ear, and striking on the auditory nerve. But we have a more conclusive proof. If one of a series of particles shot out like bullets overtakes another, the force of impact of the two is increased; but if one wave overtakes another when the crest of the pursuing wave just coincides with the hollow of the wave before it the effect is neutralized, and if the two are of equal size it will be exactly neutralized and both waves will be effaced. In other words, two lights will make darkness. This, there- fore, affords an infallible test. Jf two lights can make darkness, light is propagated, like sound, by waves. Now two lights do constantly make darkness, as is proved every day by numerous experiments. ‘Therefore light is caused by waves. But to have waves there must be a medium through which the ‘waves are propagated. Without water you could not have ocean waves; without air you could not have sound-waves. Waves are in fact nothing but the successive forms assumed by a set of particles which, when forced from a position of rest, tend to return to that position, and oscillate about it. Place a cork on the surface of a still pond, and then throw ina stone; what follows? Waves are propagated, which seem to travel outwards in circles, but if you watch the cork, you will see that it does not really travel outwards, but simply rises and falls in the same place. This is equally true of waves of sound and waves of light. But the velocity with which the waves travel depends on the nature of the medium. In a dense medium of imperfect elasticity they travel slowly, in a rare and elastic medium quickly. Now the velocity of a sound- wave in air is about 1,100 feet a second, that of the light-wave about 184,000 miles a second, or about one million times greater, It is proved by mathematical calculation that, if the density of two media . MATTER. ! 33 are the same, their elasticities are in proportion to the squares of the velocities with which a wave travels. The elasticity of ether, there- fore, would be a million million times greater than that of air, which, as we know, is measured by its power of resisting a pressure of about 15 lbs. to the square inch. But the ether must in fact be almost infi- nitely rare,as wellas almost infinitely elastic, forit causes no perceptible retardation in the motions of the earth and planets. It must be almost infinitely rare also, because it permeates freely the interior of substances like glass and crystals, through which light-waves pass, showing that the atoms or ultimate particles of which these substances are composed, minute as they are, must be floating in ether like buoys floating on water or balloons in the air. The dimensions of the light-waves which travel through this ether at the rate of 184,000 miles a second, can be accurately measured by strict mathematical calculations, depending mainly on the phenomena of interferences, 7.e., of the intervals required between successive waves for the crest of one to overtake the depression of another and thus make two lights produce darkness. These calculations are much too intricate to admit of popular explanation, but they are as certain as those of the Nautical Almanac, based on the law of gravity, which enable ships to find their way across the pathless ocean, and they give the following results: Drm enstons oF Liaut-WAVEs. NuMBER oF WavzEs | NUMBER OF OSCILLATIONS CoLoRs. IN OnE INCH. IN ONE SECOND. Red 39,000 477,000,000,000,000 Orange 42,000 506,000,000, 000,000 Yellow 44,000 535,000,000, 000,000 Green 47,000 575,000,000, 000,000 Blue 51,000 622,000, 000,000,000 Indigo 54,000 658,000, 000,000,000 Violet 57,000 669,000, 000,000,000 These are the colors whose vibrations affect the brain through the eye with the sensation of light, and which cause the sensation of white light when their different vibrations reach the eye simultaneously. But there are waves and vibrations on each side of these limits, which produce different effects, the longer waves with slower oscillations beyond the red, though no longer causing light causing heat, while the shorter and quicker waves beyond the violet cause chemical action, and are the most active agents in photography. We must refer our readers to works treating specially of light for further details, and for an account of the vast variety of beautiful and interesting experiments with polarized light, colored rings, and other- wise, to which the theory of waves propagated through ether affords the key. For the present purpose it is sufficient to say that modern science compels us to assume, as the substratum of the material universe, such an ether extending everywhere, from the faintest star seen at a distance which requires thousands of years for its rays, travel- ling at the rate of 184,000 miles a second, to reach the earth, down to the infinitesimally small interspace between the atoms of the minutest matter. And throughout the whole of this enormous range law pre- 34 MODERN SCIENCE AND MODERN THOUGHT. vails, ether vibrates and has always vibrated in the same definite man- ner, just as air vibrates by definite laws when the strings of a piano are struck by the hammers. I pass now to the consideration of matter. What is matter? In the most general sense it is that which has: weight, or is subject to the law of gravity. The next analysis shows: that itis something which can exist in the three forms of solid, liquid,, or gas, according to the amount of heat. Diminish heat, and the parti- cles approach closer and are linked together by mutual attraction, so as. not to be readily parted; this is asolid.. Increase the heat up to a cer- tain point, and the particles recede until their mutual attractions in the interior of the mass neutralize one another, so that the particles can move freely, though still held together as a mass by the sum of all these attractions acting as if concentrated at the centre of gravity; this is the liquid state. Increase the heat still more, and the particles separate until they get beyond the sphere of their mutual attraction and tend to: dart off into space, unless confined by some surface on which they exert, pressure; this is a gas. _ The most familiar instance of this is afforded by water, which, as we all know, exists in the three forms of ice, water, and vapor or steam, according to the dose of heat which has been incorporated with it. Pursuing our inquiry further, the next great fact in regard to mat- ter is that it is notall uniform. While most of the common forms with which we are conversant are made up of mixed materials, which can be taken to pieces and shown separately, there are, asat present ascer- tained, some seventy-one substances which defy chemical analysis to decompose them, and must therefore be taken as elementary substances. A great majority of these consist of substances existing in minute quan- tities, and hardly known outside the laboratories of chemists. The world of matter, as known to the senses, is mainly composed. of combinations, more or less complex, of a few elements. Thus, water is a compound of two simple gases, oxygen and hydrogen; air, of oxy- gen and nitrogen; the solid framework of the earth, mainly of combina- tions of oxygen with carbon, calcium, aluminum, silicon, and a few other bases; salt, of chlorine and sodium; the vegetable world directly and the animal world indirectly, mainly of complex combinations of oxygen, hydrogen, and nitrogen with carbon, and with smaller quantities of silicon, sulphur, potassium, sodium, and phosphorus. The ordinary metals, such as iron, gold, silver, copper, tin, lead, mercury, zinc, nearly complete the list of what may be called ordinary elements. Now let us push our analysis a step further, Howis matter made up of these elements? Up to and beyond the furthest point visible by aid of the microscope, matter is divisible. We can break a crystal into fragments, or divide a drop into drops, until they cease to be visible, though still retaining all the properties of the original substance. Can we carry on this process indefinitely, and is matter composed of some- thing that can be divided and subdivided into fractional parts ad infini- tum? The answer is, No, it consists of ultimate but still definite par- ticles which cannot be further subdivided. How is this known? Because we find by experience that substances will only combine in cer- tain definite proportions either of weight or measure. For instance, in forming water exactly eight grains by weight of oxygen combine with exactly one grain of hydrogen, and if there isany excess or frac- tional part of either gas, it remains over in its original form uncombined. MATTER. 35 In like manner, matter in the form of gas always combines with other matter inthe same form by volumes which beara definite and very simple proportion toeach other, and the compound formed bears a definite and very simple ratio to the sum of the volumes of the combin- ing gases. Thus two volumes of hydrogen combine with one of oxygen to form two volumes of water in the state of vapor. From these facts certain inferences can be drawn. In the first place it is clear that matter really does consist of minute particles, which do not touch and form a continuous solid but are separated by intervals which increase with increase of temperature. This is evident from the fact that we can pour a second or third gas into a space already occupied by a first one. Hach gas occupies the enclosed space just as if there were no other gas present, and exerts its own proper pressure on the containing vessel, so that the total pressure on it is exactly the sum of the partial pressures. Itis easy to see what this means. If a second regiment can be marched into a limited space of ground on which a first regiment is already drawn up, it is evident that the first regiment must be drawn up in loose order, 7.e., the soldier-units of which itis composed must stand so far apart that other soldier-units can find room between them without disturbing the formation. But the effect will be that the fire from the front will be increased, as for instance if a soldier of the second regiment, armed with a six-shooter repeating rifle, takes his stand between two soldiers of the first regiment armed with single-barrelled rifles, the effective fire will be increased in the ratio of 8 to 2. And this is precisely what is meant by the statement that the pressure of two gases in the same space is the sum of the separate pressures of each. It is clearly established that the pressure of a gas on a containing surface is caused by the bombarding to which it is subjected from the impacts of an almost infinite number of these almost infinitely small atoms, which, when let loose from the mutual attractions which hold them together in the solid and fluid state, dart about in all directions, colliding with one another and rebounding, like a set of little billiard-balls gone mad, and producing a certain average resultant of momentum outwards. which is called pressure. Another simile may help us to conceive how the indivisibility of atoms is inferred from the fact that they only combine in definite pro- portions. Suppose a number of gentlemen and ladies promenading promiscuously in aroom. The band strikes up a waltz, and they at. once proceed to group themselves in couples rotating with rhythmical motion in definite orbits. Clearly, if there are more ladies than gen- tlemen, some of them will be left without partners. So, if instead of a waltz it were a threesome reel, in which each gentleman led out two ladies, there must be exactly twice as many ladies as gentlemen for all to join in the dance. Butif a gentleman could be cut up into frac- tional parts, and each fraction developed into a dancing gentleman, as primitive cells split up and produce fresh cells, it would not matter how many ladies there were, as each could be provided with a partner. Now this is strictly analogous to what occurs in chemical combination. Water is formed by each gentleman atom of oxygen taking out a lady atom of hydrogen in each hand, and the sets thus formed commence to dance threesome reels in definite time and measure, any surplus oxygen or hydrogen.atoms beingyleft out in the cold. Wonderful as it may appear, science enables us not only to say of these inconceivably 36 MODERN SCIENCE AND MODERN THOUGHT. minute atoms that they have a real existence, but to count and weigh them. This fact has been accomplished by mathematical calculations based on laws which have been ascertained by a long series of experi- ments on the constitution of gases. It is found that all substances, when in the form of gas, conform to three laws: 1. Their volume 1s inversely proportional to the pressure to which they are subjected. 2. Their volume is directly proportional to the temperature. 3. At the same pressure and temperature all gases have the same number of molecules in the same volume. From the last law it is obvious that if equal volumes of two gases are of different weight, the cause must be that the molecules of the one are heavier than those of the other. This enables us to express the weight of the molecule of any other gas in some multiple of the unit afforded by the weight of the molecule of the lightest gas, which is hydrogen. Thus, the density of watery vapor being nine times that of hydrogen, we infer that the molecule of water weighs nine times as much as the molecule of hydrogen, and that of oxygen being eight times greater, we infer that the oxygen molecule is eight times heavier than that of hydrogen. These weights are checked by the other law which has been stated, that chemical combination between different substances always takes place in certain definite proportions. Thus, whenever in a chemical process the original substances or the product are or might exist in the state of gas, it is always found that the definite proportions observed in the chemical process are either the proportions of the densities of the respective gases or some simple multiple of these proportions. Thus, the weight of hydrogen being 2, which combines with a weight of oxygen equal to 16 to form a weight of watery vapor equal to 18, the density of the latter is to that of hydrogen as 9 to 1, 4.€., a8 18 to 2. But to get to the bottom of the matter we must go a step further, and as we have decomposed substances into molecules, we must take the molecules themselves to pieces and see what they are made of. The molecule is the ultimate particle into which any substance can be divided retaining its own peculiar qualities. A molecule of water is as tr ruly water as a drop or a tumblerful. But when chemical decom- position takes place, instead of the molecule « of water we have molecules of two entirely different substances, oxygen ‘and hydrogen. Nothing can well be more unlike than the product water and the component parts of which it is made up. Water is a fluid, oxygen a gas; water extinguishes fire, oxygen creates it. Water is a harmless drink, oxy- gen the base of the most corrosive acids. It is evident that the water- molecule is a composite, and that its qualities depend, not on the essential qualities of the atoms which have combined to make it, but on the manner of the combination, and the new modes of action into which these atoms have been forced. In his native war-paint oxygen is a furious savage; with a hydrogen atom in each hand heisa polished gentleman. Our theory, therefore, leads beyond molecules to atoms, and we ‘have to consider these particles of a still smaller order than molecules, as the ultimate indivisible units of matter of which we have been in search. And even these we must conceive of as corks, as it were, float- ge MMAT DLR, 37 ing in ap ocean of ether, causing waves in it by: their own proper movements, and agitated by- all the successive waves which vibrate through this ether-ocean in the form of light and heat. Working on these data, a variety of refined mathematical calcula- tions made by Clausius, Clark Maxwell, Sir W. Thomson, and other eminent mathematicians, have given us approximate figures for the actual size, weight, and velocities of atoms and molecules. The results are truly marvellous. A millimetre is the one thousandth part of a metre, or roughly one twenty-fifth of an inch. The magnitudes with which we have to deal are all of an order where the standard of measurement is expressed. by the millionth part of a millimetre. The volume of a molecule of air is only a small fraction of that of a cube whose side would be the millionth of amillimetre. ‘The learned Swedish physician, Bj6rnstr6m.—Churchman. Itisa strange and mysterious subject this hypnotism.— 7he Sun. Perhaps as concise as any work we have.—S, California Practitioner, - We have found this book exceedingly interesting.—California Homepath fo | +e Bests: PROLouels and scientific examination of a little-understood sub} sct —Epise ee “2007 ers ot Pet Few of the new books have more interest for scientist and layman alike.—Sunday Time Boston) aneehe study of hypnotism is in fashion again. Itisa fea ok Ut and dangerous —- netic subject will be fsdinating to many, and it receives a cautious yet sympathet tment in this book. —Lvangeltst., Be iucoe Swedish alienist known to American students of pavocea psychiatry. —Medica dard (Chicago). his is a highly interesting and instructive book. Hypnotism is on the onward marck sie ie front as a scientific subject for serious thought and investigation. —The Medical fre if ss (Indianapolis). any of the mysteries of mesmerism, and all that class of manifestation, are “her: be d- at length, and explained as far as they can be with our present knowledge of psy- 1e marvels of hypnotic phenomena increase with investigation. Dr. Bjdrnstrém, i in s clear and well-written essay, has given about all that modern science has been ae a elop of these phenomena.—Jedical Visitor (Chicago). has become a matter of scientific research, and engages the attention of some of fda. a meén of the day, like Charcot, of Paris. It is interesting reading, outside of any interesting book contains a. Beye: accoint of the history, acvelopaeeal aspect of hypnotism. As a whole, the book is of great interest and very ins s worthy of careful perusal by all physicians, and contains Nata unfit to he oe oe, and Surgical REDRGLEE Gorse veracity None the aes however doe s it practitioner chabueid what it Goes, even if he cannot. tell just what i it is strom’s book ms to give a jeneral review of the en ire se Greatest Book of he Contury. | Thousands Bh ANC ane ordered every Week. u By EDWARD BELLAMY. In paper covers, 50 cents; in cloth covers Ae “ Bellamy’s wonderful book.” —EDwarD. EVERETT HALE. sheer “Tt is a revelation and an evangel.” — FRANCES E. WILLARD. | “ A romance of surpassing merit and noble purpose.” — EDGAR FAWCETT. “‘ The vital, inspiring, convincing power of this book.” — Literary World. “ Intensely interesting, and more ued vaca ” — Golden Rule, Boston. | The Critic. “A marvelous story, combined with social philosophy and a forecast of the milena ee Transcript. em, That astonishing book, ‘ Looking. Rackwerds how it haunts one, like a grown-up ‘ Alice i in : land.’ nes mind follows entranced.” — Eee Boston. . 7— W. D. HowELLs. neh the charms of the author’s art; . . . his ae Tae _ “The most wonderful book of the nineteenth century. This is the best of the many BA ne ten to make the people think. But’ ‘ Looking Backward’ inspires hope as well as asics ee aS ft ite seriously. ‘The appeal is always made to a man’s reason, and to his monies sentiment —ne ty te his selfishness.” — Boston Post. is ara Backward’ is a well-made book, but it is more —a glowing oan fe peace. He who reads it expecting merely to be entertained, must, we should. think, find hi No. 1. No. No. 4. No. 8. No. 9. No. 10. No. 11. No. 12. No. 13. Ro, 14. No. 15. No. 16. Ro. 17. No. 18. No. 19. Ro, 20. Ro. 21. - Town Geology. 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