Mr. Pengelly"s own estimate of the rate of deposit gives, however, a length of time which is sufficient to show that there must be error somewhere in his calculations. He states the aggregate thickness of the two crusts at twelve feet, and then, a.s.suming a rate of deposit of 0.05 inch in 250 years, or one inch in 5000 years, he arrives at the conclusion that the whole deposit required 720,000 years for its formation. He is "willing to suppose" the mechanical deposits to have acc.u.mulated more rapidly; but allowing one fourth of the time for them, we have nearly a million of years claimed for the residence of man in Devonshire, which, independently of other considerations, would push back the Palaeozoic trilobites and corals of that county into the primitive reign of fire, and which in point of fact amounts to a _reductio ad absurdum_ of the whole argument.
Professor Hughes[154] refers, as a case of rapid deposition of matter akin to stalagmite, to the deposit of travertine in the old Roman aqueduct of the Pont du Gard, near Avignon, where a thickness of fourteen inches seems to have acc.u.mulated in about 800 years. Mr. J.
Carey has given in _Nature_, December 18, 1873, another instance where a deposit 0.75 inch thick was formed in fifteen years in a lead mine in Durham. Mr. W. B. Clarke in the same journal gives a case where in a cave at Brixton, known as Poole"s Hole, a deposit one eighth of an inch in thickness was formed in six months. Such examples show how unsafe it is to reason as to the rate of deposit in by-gone times, and when climatal and local conditions may have been very different from those at present subsisting.
In an able address before the biological section of the British a.s.sociation in 1876, Wallace adduces the following considerations as bearing on these questions; and these are well worthy of attention as showing that it is the necessities of evolution rather than of geological facts that demand the a.s.sumption of a great antiquity for man, and induce so many writers to accept any evidence for this, however doubtful: (1) The great cerebral development of the so-called Palaeolithic men, which shows no indications of graduating into inferior races. (2) The great variety of the implements of these ancient men, and the excellence of their carvings on bone and ivory, point to a similar conclusion. (3) Man is not related to any existing species of ape, but in various ways to several different species. (4) There is an acc.u.mulation of evidence to show that the earliest historical races excelled in many processes in the arts and in many kinds of culture. He instances the wonderful mechanical and engineering skill evidenced in the pyramids of Egypt in proof of this.
His conclusion is either that the origin of man by development from apes must be pushed much farther back than any geologists at present hold, and I may add far beyond any probable date, or that he must have originated by some "distinct and higher agency"--which last is no doubt the true conclusion.
Haeckel, in his recent work, the "History of Creation," sketches the development of man from a monad, in twenty-two stages; but he has to admit that stage twenty-first, or that of the "Ape-like man," nowhere exists, either recent or fossil. He has to a.s.sume that this missing link has perished in the submergence of an imaginary continent of Lemuria, in the Indian Ocean; and it is instructive to observe that, after deducting this, his affiliation of the races of men, as indicated in a map of the distribution of the species, is in the main very similar to that with which we are familiar in ordinary collections of maps ill.u.s.trative of the Bible.
The Post-glacial, Palaeocosmic, or Palaeolithic men of Europe are not improbably antediluvian; and as to their precise date we know little.
As to postdiluvian man, Canon Rawlinson has recently pointed out[155]
the remarkable convergence of all historic dates toward a time between 2000 to 3000 years B.C., or about the date of the Biblical deluge, which may reasonably be inferred to have occurred about 3200 B.C. He gives the following summary of historical origins as ascertained from the best data, and which accord with the representation of the Bible that in the time of Abraham the great monarchies of Egypt and the East were scarcely more powerful than the nomad tribe led by that patriarch:
Oldest date of Babylon 2300 B.C.
" " a.s.syria 1500 " " Iran 1500 " " India 1200 " " China 1154 " " Phoenicia 1700 " " Troad 2000 " " Egypt 2760 Sept. date of Deluge 3200
He rejects, of course, the fabulous chronologies of Egypt, China, and India as mythical, or referring to prehuman and antediluvian periods.
It is to be observed that while these dates place the origins of the oldest civilized nations at periods considerably subsequent to the deluge, they do not prevent us from supposing that these nations commenced their existence wills an advanced civilization borrowed from antediluvian times, which is indeed a fair conclusion from the Biblical history, independently of the monumental evidence referred to by Wallace in a previous paragraph.
The Duke of Argyll, in his excellent little work "Primeval Man," in which he discusses the arguments in favor of primitive savagery advanced by Sir J. Lubbock in opposition to the views of Archbishop Whately in his lecture on the "Origin of Civilization," shows that there is no necessity to suppose a slow progress of mankind in the arts extending over indefinite ages; and his argument in this respect connects itself with the facts as to the high cerebral organization of Palaeocosmic men referred to above by Wallace. In summing up one division of his argument, he truly remarks: "If we a.s.sume with the supporters of the savage-theory that man has himself invented all that he now knows, then the very earliest inventions of our race must have been the most wonderful of all, and the richest in the fruits they bore. The man who first discovered the use of fire, and the use of those gra.s.ses which we now know under the name of corn, were discoverers compared with whom, as regards the value of their ideas to the world, Faraday and Wheatstone are but the inventors of ingenious toys. It may possibly be true, as Whately argues, that man never could have discovered these things without divine instruction. If so, it is fatal to the savage theory. But it is equally fatal to that theory if we a.s.sume the opposite position, and suppose that the n.o.blest discoveries ever made by man were made by him in primeval times."
I may add that this is true, however far into antiquity we may stretch back these primeval times.
Professor E. S. Morse, in his address to the American a.s.sociation, in 1876, as vice-president, takes as a theme the contributions of American zoologists to theories of evolution, and closes with those which refer to what he modestly terms "man"s lowly origin." These contributions he sums up under three heads, as bearing on the following points: "1. That in his earlier stages he reveals certain persistent characters of the ape; 2. That the more ancient men reveal more ape-like features than the present existing men; and, 3. That certain characteristics pertaining to early men still persist in the inferior races of men." Under the first head he gives contributions to the well-known fact that embryonic stages of the human being, like those of other high types, approximate to forms permanent in lower types. This is a fact inseparable from the law of reproduction; and as has been already shown in the text, absolutely without logical significance as even an a.n.a.logical argument in favor of evolution.
Under the second and third heads, he refers to cases of exceptional skulls and bones belonging to idiots and degraded races of men, as showing tendencies to lower forms, which as a matter of course they do, though with essential differences still marking them as human; and he a.s.sumes without any proof that these were relatively more common in primitive times, and that they are cases of reversion to a previous simian stage, instead of being results of abnormal conditions in the individual or variety. He sums up these arguments in the following paragraph:
"If we take into account the rapidly acc.u.mulating data of European naturalists concerning primitive man, with the ma.s.s of evidence presented in these notes, we find an array of facts which irresistibly point to a common origin with animals directly below us, and these evidences are found in the ma.s.sive skulls with coa.r.s.e ridges for muscular attachments, the rounding of the base of the nostrils, the early ossification of the nasal bones, the small cranial capacity in certain forms, the prominence of the frontal crest, the posterior position of the _foramen magnum_, the approximation of the temporal ridges, the lateral flattening of the tibia, the perforation of the humerus, the tendency of the pelvis to depart from its usual proportions; and, a.s.sociated with all these, a rudeness of culture and the evidence of the manifestation of the coa.r.s.est instincts. He must be blind, indeed, who can not recognize the bearing of such grave and suggestive modifications."
Yet Professor Morse knows that there is no true specific or even generic kinship between man and any species of ape; that the phenomena of idiocy and degeneracy have no real resemblance to those of distinct specific types; that the resemblances of man to apes, such as they are, point not in a direct manner to any stock of apes, but in a desultory way to several; and consequently that, if derived from any such animals, it must be from some stock altogether unknown to us as yet, either among recent or fossil animals. Farther, as Cope, himself an evolutionist, admits, while we can trace the skeletons of Eocene mammals through several directions of specialization in succeeding Tertiary times, man presents the phenomenon of an unspecialized skeleton which can not fairly be connected with any of these lines.
Lastly, his quotation from Fiske, with reference to the supposed effect of a protracted infancy to develop the moral characteristics of man, though accompanied with the usual unfair and unreasonable sneer (which a naturalist like Morse should have been ashamed to quote) against men "still capable of believing that the human race was created by miracle in a single day," is the feeblest possible attempt to bridge over the gap between the spiritual nature of man and the merely psychical nature of brutes.
It is plain that if American naturalists have done nothing more in favor of the lowly origin of man than that which Professor Morse has been able, evidently with much industry and pains, to gather, we need not for the present abandon our claims to a higher origin. It is farther significant in connection with this that Professor Huxley, in his lectures in New York, while resting his case as to the lower animals mainly on the supposed genealogy of the horse, which has often been shown to amount to no certain evidence,[156] avoided altogether the discussion of the origin of man from apes, now obviously complicated with so many difficulties that both Wallace and Mivart are staggered by them. Professor Thomas, in his recent lectures,[157]
admits that there is no lower man known than the Australian, and that there is no known link of connection with the monkeys; and Haeckel[158] has to admit that the penultimate link in his phylogeny, the ape-like man, is absolutely unknown.
In Chapter XIII. I have not touched on the question of the absolute origin of language--this not being necessary to my argument. On this interesting subject, however, we have, in the naming of the animals by the first man, recorded in the second chapter of Genesis, not only the primary truth of his superiority to them, but a farther indication that the roots of human speech, other than interjectional, lie in onomatopoeia, and especially in the voices of animals, and that the gift of speech was not the slow growth of ages, but an endowment of man from the first, just as much as any of his other powers or properties. An interesting discussion of this subject will be found in the concluding chapters of Wilson"s "Prehistoric Man," second edition.
Farther, the so-called "tallies" found with the bones of Palaeocosmic men in European caves, and ill.u.s.trated in the admirable work of Christy and Lartet, show that the rudiments even of writing were already in possession of the oldest race of men known to archaeology or geology. (See Wilson, _op. cit._, vol. ii., p. 54.)
I have not noticed, except incidentally, the alleged discoveries of very ancient human remains in America, as they all appear very problematical. There is, however, some evidence of the coexistence of man with the mastodon and other postglacial animals in Illinois and elsewhere.
F.--BEARING OF GLACIAL PERIODS UPON THE INTERPRETATION OF GENESIS.
Whatever views may be taken as to that period of cold which occurs at the close of the Tertiary and beginning of the Modern period, it can not be held to have const.i.tuted any such break as to be considered, as it was at one time, an equivalent for the Biblical chaos. This is proved by the survival through this period of a very large proportion of the animals and plants still existing in the northern hemisphere.
The chronological system of animals and plants has been continuous, as the Bible represents it, since their first appearance on earth.
It is further remarkable that while there is geological evidence of climates colder than the present in the temperate regions, there is equally good proof of warmer climates even within the arctic circle than those of the cold temperate regions at present. It is difficult to account for these vicissitudes of climate, and much controversy exists on the subject; but it seems certain that in the earlier Tertiary and Cretaceous periods, for example, the supplies of heat and light were so diffused over the earth as to permit the growth of a temperate vegetation in Greenland, and even in Spitzbergen.
Geologists, however unwillingly, have been obliged to admit this as one of those great possibilities, altogether unexpected beforehand, which have been developed in the history of our planet. Various modes of explaining this succession of cold and warm periods have been adopted, all more or less hypothetical. Lyell has argued that it may be explained by a different distribution of land and water and of the ocean currents. Croll accounts for it by the varying eccentricity of the earth"s...o...b..t, in connection with the precession of the equinoxes.
Evans by a shifting of the axis of rotation of the earth. Drayson, Bell, Warring, and others, by a change in the inclination of the earth"s axis. Others by the secular diminution of the internal heat of the earth, and of that of the sun. Others by the supposed recurrence of periods in which the sun gives more or less heat, or in which the earth is pa.s.sing through colder or warmer regions of s.p.a.ce. As the subject is of interest with reference to possible correspondences of these great summers and winters of the earth with the stages of the creative work, it may be well to notice shortly the relative merits of these theories.
(1.) The hypothesis of Croll is one of the most ingenious and elaborate of the whole; but it has two great defects. One is that the causes alleged are so uncertain and so complicated that it is difficult to estimate their real value. Another is that it proves too much, namely, a regular succession of cold and warm periods throughout geological time, of which we have no good evidence, and which is on many grounds improbable.
(2.) That the earth"s axis of rotation has continued unchanged throughout the whole of the geological ages seems proved by the fact that the princ.i.p.al lines of crumpling and upheaval from the Laurentian period downward are arranged in great circles of the earth tangent to the polar circle; and that the lines of deposit of sediment in the Palaeozoic age are coincident with the present direction of the arctic currents.
(3.) Astronomers consider it improbable that the obliquity of the ecliptic has materially changed, and serious differences of opinion exist as to the effects which a greater or less obliquity would produce on climate. It seems certain, however, that a less obliquity would occasion a more uniform distribution of heat and light throughout the year; and this, co-operating with other causes leading to a warm climate, might enable a temperate vegetation to approach the pole more closely than at present.
(4.) That the energy of the sun"s radiation and the internal heat of the earth have been slowly decreasing seems certain; but it is now generally admitted that these changes are so gradual that little effect can have been produced by them, except in the older geological periods, and that they can have no connection with the great glacial period of the Post-pliocene.
(5.) It is otherwise with the hypothesis that the sun"s heat may, like that of some variable stars, have increased and diminished. There is, of course, no direct evidence of this, except the small differences observed in cycles of eleven and fifty-five years from the greater or less development of sunspots, and the a.n.a.logy of observed variable stars. Still it is a possible cause of variations of climate. It might also aid in accounting for the extraordinary evidences of desert conditions and desiccation presented by the salt deposits of different geological periods in temperate lat.i.tudes.
(6.) The theory of the pa.s.sage of the earth through zones of s.p.a.ce of variable temperature is now generally abandoned, as there seems no reason to believe that such differences exist.
(7.) The theory of Lyell that changes in the distribution of land and water may, with the possible co-operation of other causes, have produced the observed diversities of climate, is that which seems best to meet the conditions presented. It is based on the known properties of land and water as to the absorption, radiation, and convection of heat, and on the remarkable diversities of climate in similar lat.i.tudes arising from this cause at present. Farther, it accords with the known fact that very great changes of level have occurred in connection with the glacial period. This theory undoubtedly embraces a true cause, admitted by all geologists, and it dispenses with the necessity of believing in the recurrence of glacial periods at regular intervals. It farther accords best with the evidence afforded by fossils, and especially by fossil plants. It has also the merit of directing due attention to the diversities of geographical conditions at different periods, and of dealing with causes of change operating within the earth itself. The only doubt with respect to it is its sufficiency to explain the changes which have occurred, and the view entertained of this will depend very much on the interpretation of the facts as to the intensity of the last glacial period. If moderate views can be taken of this, and if means can be found, by a less obliquity of the ecliptic or otherwise, to furnish a continuous supply of light in the arctic regions, the difficulties which have been alleged against it would disappear.
(8.) In connection with former periods of cold and warmth, and with the existence of temperate and tropical vegetation in polar lat.i.tudes, we should not forget that view which takes into account the probable effects of different conditions of the atmosphere, and the greater quant.i.ty of carbonic acid present in it, in early geological periods.
This would, of course, best apply to the palaeozoic floras, in so far as our present knowledge extends; but there may have been similar conditions in later periods. Dr. Sterry Hunt thus states this hypothesis:
"The agency of plants in purifying the primitive atmosphere was long since pointed out by Brongniart, and our great stores of fossil fuel have been derived from the decomposition, by the ancient vegetation, of the excess of carbonic acid of the early atmosphere, which through this agency was exchanged for oxygen gas. In this connection the vegetation of former periods presents the curious phenomenon of plants allied to those now growing beneath the tropics flourishing within the polar circles. Many ingenious hypotheses have been proposed to account for the warmer climate of earlier times, but are at best unsatisfactory, and it appears to me that the true solution of the problem may be found in the const.i.tution of the early atmosphere, when considered in the light of Dr. Tyndall"s beautiful researches on radiant heat. He has found that the presence of a few hundredths of carbonic-acid gas in the atmosphere, while offering almost no obstacle to the pa.s.sage of the solar rays, would suffice to prevent almost entirely the loss by radiation of obscure heat, so that the surface of the land beneath such an atmosphere would become like a vast orchard-house, in which the conditions of climate necessary to a luxuriant vegetation would be extended even to the polar regions."
It is obvious that, in the production of complex effects of this kind, various causes, whether astronomical or connected with the mutations of the earth"s crust, may have co-operated, and probably in all extreme cases did co-operate.
In any case it is evident that the vicissitudes of climate and the great pulsations of the crust, which have raised and depressed portions of the surface and changed the position of its covering of waters, have been potent agents in the hands of the Creator in effecting the changes and succession of living beings, which are thus, as Genesis intimates, children of the waters and of the land, and of the influences of the heavens. It is also interesting in this connection to observe that the occurrence of such periods of general warm climate as that in the Miocene shows that it would have been possible for man, under certain conditions, to have extended himself far more widely in his Edenic state than we can conceive of in the present condition of the earth. The modern world is perhaps even in this way "cursed" for man"s sake.
G.--DR. STERRY HUNT ON THE CHEMISTRY OF THE PRIMEVAL EARTH.
On looking back to the reference to this subject in Chapter V., I think it may be desirable to present to the reader in some more definite manner the conditions of a forming world; and I can not do this in any other way so well as by quoting the words of Dr. Sterry Hunt, as given in the abstract of his lecture on this subject delivered before the Royal Inst.i.tution of London in 1867:
"This hypothesis of the nature of the sun and of the luminous process going on at its surface is the one lately put forward by Faye, and, although it has met with opposition, appears to be that which accords best with our present knowledge of the chemical and physical conditions of matter, such as we must suppose it to exist in the condensing gaseous ma.s.s which, according to the nebular hypothesis, should form the centre of our solar system. Taking this, as we have already done, for granted, it matters little whether we imagine the different planets to have been successively detached as rings during the rotation of the primal ma.s.s, as is generally conceived, or whether we admit with Chacornac a process of aggregation or concretion, operating within the primal nebular ma.s.s, resulting in the production of sun and planets. In either case we come to the conclusion that our earth must at one time have been in an intensely heated gaseous condition, such as the sun now presents, self-luminous, and with a process of condensation going on at first at the surface only, until by cooling it must have reached the point where the gaseous centre was exchanged for one of combined and liquefied matter.
"Here commences the chemistry of the earth, to the discussion of which the foregoing considerations have been only preliminary. So long as the gaseous condition of the earth lasted, we may suppose the whole ma.s.s to have been h.o.m.ogeneous; but when the temperature became so reduced that the existence of chemical compounds at the centre became possible, those which were most stable at the elevated temperature then prevailing would be first formed. Thus, for example, while compounds of oxygen with mercury or even with hydrogen could not exist, oxides of silicon, aluminium, calcium, magnesium, and iron might be formed and condense in a liquid form at the centre of the globe. By progressive cooling, still other elements would be removed from the gaseous ma.s.s, which would form the atmosphere of the non-gaseous nucleus. We may suppose an arrangement of the condensed matters at the centre according to their respective specific gravities, and thus the fact that the density of the earth as a whole is about twice the mean density of the matters which form its solid surface may be explained. Metallic or metalloidal compounds of elements, grouped differently from any compounds known to us, and far more dense, may exist in the centre of the earth.
"The process of combination and cooling having gone on until those elements which are not volatile in the heat of our ordinary furnaces were condensed into a liquid form, we may here inquire what would be the result, upon the ma.s.s, of a further reduction of temperature. It is generally a.s.sumed that in the cooling of a liquid globe of mineral matter, congelation would commence at the surface, as in the case of water; but water offers an exception to most other liquids, inasmuch as it is denser in the liquid than in the solid form. Hence ice floats on water, and freezing water becomes covered with a layer of ice, which protects the liquid below. With most other matters, however, and notably with the various mineral and earthy compounds a.n.a.logous to those which may be supposed to have formed the fiery-fluid earth, numerous and careful experiments show that the products of solidification are much denser than the liquid ma.s.s; so that solidification would have commenced at the centre, whose temperature would thus be the congealing point of these liquid compounds. The important researches of Hopkins and Fairbairn on the influence of pressure in augmenting the melting-point of such compounds as contract in solidifying are to be considered in this connection.
"It is with the superficial portions of the fused mineral ma.s.s of the globe that we have now to do; since there is no good reason for supposing that the deeply seated portions have intervened in any direct manner in the production of the rocks which form the superficial crust. This, at the time of its first solidification, presented probably an irregular, diversified surface from the result of contraction of the congealing ma.s.s, which at last formed a liquid bath of no great depth surrounding the solid nucleus. It is to the composition of this crust that we must direct our attention, since therein would be found all the elements (with the exception of such as were still in the gaseous form) now met with in the known rocks of the earth. This crust is now everywhere buried beneath its own ruins, and we can only from chemical considerations attempt to reconstruct it. If we consider the conditions through which it has pa.s.sed, and the chemical affinities which must have come into play, we shall see that these are just what would now result if the solid land, sea, and air were made to react upon each other under the influence of intense heat. To the chemist it is at once evident that from this would result the conversion of all carbonates, chlorides, and sulphates into silicates, and the separation of the carbon, chlorine, and sulphur in the form of acid gases, which, with nitrogen, watery vapor, and a probable excess of oxygen, would form the dense primeval atmosphere.
The resulting fused ma.s.s would contain all the bases as silicates, and must have much resembled in composition certain furnace-slags or volcanic gla.s.ses. The atmosphere, charged with acid gases, which surrounded this primitive rock must have been of immense density.
Under the pressure of such a high barometric column, condensation would take place at a temperature much above the present boiling-point of water, and the depressed portions of the half-cooled crust would be flooded with a highly heated solution of hydrochloric acid, whose action in decomposing the silicates is easily intelligible to the chemist. The formation of chlorides of the various bases, and the separation of silica, would go on until the affinities of the acid were satisfied, and there would be a separation of silica, taking the form of quartz, and the production of a sea-water holding in solution, besides the chlorides of sodium, calcium, and magnesium, salts of aluminium and other metallic bases. The atmosphere, being thus deprived of its volatile chlorine and sulphur compounds, would approximate to that of our own time, but differ in its greater amount of carbonic acid.
"We next enter into the second phase in the action of the atmosphere upon the earth"s crust. This, unlike the first, which was subaqueous, or operative only on the portion covered with the precipitated water, is sub-aerial, and consists in the decomposition of the exposed parts of the primitive crust under the influence of the carbonic acid and moisture of the air, which convert the complex silicates of the crust into a silicate of alumina, or clay, while the separated lime, magnesia, and alkalies, being converted into carbonates, are carried down into the sea in a state of solution.
"The first effect of these dissolved carbonates would be to precipitate the dissolved alumina and the heavy metals, after which would result a decomposition of the chloride of calcium of the sea-water, resulting in the production of carbonate of lime or limestone, and chloride of sodium or common salt. This process is one still going on at the earth"s surface, slowly breaking down and destroying the hardest rocks, and, aided by mechanical processes, transforming them into clays; although the action, from the comparative rarity of carbonic acid in the atmosphere, is less energetic than in earlier times, when the abundance of this gas, and a higher temperature, favored the chemical decomposition of the rocks.
But now, as then, every clod of clay formed from the decay of a crystalline rock corresponded to an equivalent of carbonic acid abstracted from the atmosphere, and equivalents of carbonate of lime and common salt formed from the chloride of calcium of the sea-water."[159]
H.--TANNIN AND BHEMAH.
The following synopsis of the instances of the occurrence of the words _tannin_ and _tan_ will serve to show the propriety of the meaning, "great reptiles," a.s.signed in the text to the former, as well as to ill.u.s.trate the utility in such cases of "comparing Scripture with Scripture:"
1. TANNIN.