sitions only that he can work around the obstacles presented to his theory by the apparently abrupt changes of species on the introduction of the Tertiary (Cainozoic), the Secondary (Maesozoic), and the Silurian (Palaeozoic) eras. This appeal to the incompleteness of the geological record is not made by the Darwinians for the purpose of adducing positive argument, but to break the force of the negative arguments which their opponents array against them. By this means they attempt to give a rational explanation of the gaps that appear in their chain of positive evidence. It must be remarked, however, that these asserted hard-and-fast lines of demarcation between the geological eras are gradually disappearing before the advance of scientific discoveries. There is, for example, constantly increasing evidence that birds and marsupial quadrupeds existed in great numbers as early as the middle portion of the Secondary period. "The hiatus, which, in the idea of most geologists, intervened between the close of the Cretaceous and the beginning of the Tertiary, appears to have had no existence so far as concerns the vegetation."2 The sudden appearance of groups of highly developed species, like the Trilobite, in the lowest fossiliferous strata is confessed by Mr. Darwin to remain as yet inexplicable; and he acknowledges that it "may be truly urged as a valid argument against his views "8 At the same time, he presents an hypothesis "to show that it may hereafter receive some explanation." The reader should note carefully the character of Mr. Darwin's reasoning, as distinguished from the multitude of a priori evolutionists who have espoused his cause. His endeavor is to feel his way backwards from manifest present affinities along the converging lines of geological evidence, as far as they are tangible. He would claim that his positive analogies are sufficient to outweigh a large amount of merely negative evidence, and that it is only incumbent on him to show by hypothesis that the 1 See Lyell, Principles of Geology, Vol. i. pp. 155–160. 2 Count Gaston de Saporta, quoted by Gray, in Darwiniana, p. 197. obstacles opposed by negative evidence are not insuperable. Nevertheless, it is incumbent on him to proceed with more and more caution as he gets away from his base of observation. Mr. Darwin's method may be compared to that of astronomers in establishing the unlimited operation of the law of gravitation. It is a mistake to suppose that they have proved the general prevalence of this law with anything like mathematical accuracy. The planetary bodies do not yet all come around on time. No astronomer pretends that he has measured all the disturbing forces which determine the motions of the heavenly bodies. But, after having adduced a certain amount of positive evidence, it is sufficient for his purpose to show that unexpected aberrations could be accounted for on the hypothesis of disturbing powers such as are known to exist. It cannot by any means be said that the proof of the derivative origin of species has reached so high a degree of perfection as that of the theory of gravitation. It might more properly be compared to the condition of that theory just previous to the work of Laplace, who, by explaining a great number of apparent irregularities in the solar system, as the result of gravitation acting on masses of hypothetical size and density, and situated at hypothetical distances from each other, has established the theory beyond peradventure. Astronomy was a science before Laplace. Since his day it has merited the title of an "exact science." The science of Tidology offers a comparison more nearly in point. The tides doubtless, are an effect of gravitation. But no mathematician can deductively work out the problem of those effects for all shores, and for every bay and inlet. The tide of each locality has a law of its own. All that can be done regarding abnormal instances, such, for example, as the enormous rise in the tide in the Bay of Fundy, is to show that they are not inconsistent with the theory of their being the effect of gravitation as conditioned by the changing positions of the earth and moon and sun acting on bodies of water, which are confined by shores that are but partially surveyed, and which rests on a bottom whose character is to a still greater degree unknown. Or, again, those who reconstruct the original text of our sacred scriptures do not pretend that they have a copy as it came from the hands of the authors. They, however, approach the central century, in which Christ and the apostles lived, on converging lines, some shorter, some longer; a few only reaching to the second or third century. By such a process it is believed that we are even more certain that we have the substance of gospel history and apostolic doctrine than we could be if we were supposed to have the original records. For it would be a more difficult matter to prove those alleged original documents to be original than it is to prove their substance from the manuscripts we have. For when manuscripts and versions with minor variations are traced along different lines toward a centre, we may rely on the aberrations of one class to correct those of another. We hope this may not seem a digression; for the arguments of naturalists cannot be weighed without coming back repeatedly to the foundations on which all evidence reposes. It should be put to the credit of Mr. Darwin that, in the main, he tries to adhere to the canons of proof that are generally accepted in all sciences which deal with actual things. III. ABSENCE OF INTERMEDIATE VARIETIES. In the preceding section we have spoken of the "sudden appearance of groups of allied species" at the beginning of the so-called geological eras. The present objection to Darwinism is closely allied to the previous one. It is alleged that, according to theory, there ought to be in any single formation an innumerable number of intermediate forms, shading into each other by imperceptible steps, and connecting the species which lived at the commencement with those living at the close of the period. But the links as best made out, when compared with those that must have actually existed, are few and disconnected. The only reply that can be made is that the geological record, even in the best preserved sections, is poor and beggarly beyond description. To get the force of this reply, one must conceive more fully the contingencies which attend the preservation of fossils.2 1. The "bird must be caught." The animal must die in a situation such that he shall be speedily imbedded in fine sediment. This is one contingency, and can occur only to a comparatively few individuals of a species. 2. The strata in which the fossil is deposited must be preserved from subsequent denudation. 3. "In order to get a perfect gradation between two forms in the upper and lower parts of the same formation, the deposit must have gone on continuously accumulating during a long period, sufficient for the slow process of modification; hence the deposit must be a very thick one, and the species undergoing change must have lived in the same district throughout the whole time." 3 4. In order to have a record of gradations in a single formation, the life of the species must be shorter than the period in which the formation was deposited. Mr. Darwin closes his patient discussion of this objection with the remark that," if there be some degree of truth" in the considerations he presents, "we have no right to expect to find in our geological formations an infinite number of those transitional forms which, on our theory, have connected all the past and present species of the same group into one long and branching chain of life. We ought only to look for a few links; and such, assuredly, we do find. ..... But I do not pretend that I should ever have suspected how poor was the record in the best preserved geological sections, had not the absence of innumerable transitional links between the species which lived at the commencement and close of each formation, pressed so hardly upon my theory." 4 1 See Origin of Species, Chaps. vi. and x. Lyell's Elements, p. 115; Principles, Vol. i. p. 341 f.; Vol. ii. p. 490. 2 See Dana, Manual of Geology (2d. ed.), p. 600. 8 Origin of Species, p. 277. 4 Ibid. p. 282. Professor Agassiz, in the very latest lines that fell from his pen, was proposing to show that we have a geological record which is vastly more complete than Mr. Darwin supposes; and that, "however broken the geological record may be, there is a complete sequence in many parts of it, from which the character of the succession may be ascertained.” 1 But death cut him down before he had elaborated the proposition, and there has been no one else so competent to take it up." IV. LAPSE OF TIME INSUFFICIENT FOR THE EFFECTS. Though we be at the middle point of duration, the world has not existed in its present condition forever. The physical philosophers have something to say about the age of the world. The earth is kept in its present condition by the interaction of a variety of correlated physical forces. Heat, light, electricity, chemical attraction, and motion are passing from one into the other in varying degrees of rapidity. Change can only occur where there is a disturbance of the equilibrium of these forces. To one effect all these modifications are tending, viz. an equilibrium that must be lifeless. The cosmos is running down like a clock. The heat of the world is dissipating. The earth is retarding its pace. Perpetual motion is as much an absurdity in a planetary system as in a human machine. "Nature no more works without friction than we can." "The power man can extract from a ton of coals is limited; but perhaps not one reader in a thousand will at first admit that the power of the sun and that of the chemical affinities of bodies on the earth is equally limited." We are assured, however, on the highest authority, that "the sun will be too cold for our, or Darwin's, purposes before many millions of years - a long time, but far enough from countless ages. Quite similarly, past countless ages are inconceivable, inasmuch as the heat required by the sun to have allowed him to cool from time immemorial would be such as to turn him into mere vapor, which would extend over the whole planetary system and evaporate us entirely...... Darwin's theory requires 1 See Atlantic Monthly, Vol. xxxiii. p. 101. 2 See North British Review, Vol. xlvi. pp. 294–305. 8 Ibid. pp. 297, 300. |