But it seems to me that here we have an enormous amount of energy going to waste. Others have demanded a continent to explain the appearance of a beetle in a certain locality; but here we have a great world-wide catastrophe to explain the sudden disappearance of merely a few species. Why not utilize this surplus energy in doing other necessary work, that has certainly been accomplished somehow, but has hitherto gone a-begging for a competent cause? The only thing I object to in Dana's view of the case is his way of having these "exterminations" take place on the installment plan. For in that way we have to work up a great world catastrophe to do only a very limited amount of work, and then have to repeat the thing another time for a similarly limited work, when one such cosmic convulsion is competent to do the whole thing. I plead for the "law of parsimony," and the economizing of energy.
The vast shoals of carcasses which seem to be piled up in almost every corner of the world are prima facie evidence that our old globe has witnessed some sort of cosmic convulsion. The exact cause, nature, and extent of this event we may never have sufficient facts to determine, though two or three additional facts having a bearing on the subject will be considered in the following chapters.
[CHAPTER X]
CHANGE OF CLIMATE
Another great general fact about the fossil world may be stated about as follows:
All of the fossils (save a very few of the so-called "Glacial Age," and they admit of other easy explanation) give us proofs of an almost eternal spring having prevailed in the Arctic regions, and semi-tropical conditions in north temperate latitudes; in short give us proofs of a singular uniformity of climate over the globe which we can hardly conceive possible, let alone account for.
The proofs of this are almost unnecessary, as this subject of climate has been pretty well discussed of late years. And it was the overwhelming evidence on this point which forced Lyell and so many others to decide against the theory of Croll, which called for a regular rotation of climates, for they said that the fossil evidence was wholly against such a view. Howorth has given an admirable argument on this point in Chapter XI of his second work on the Glacial Theory[68] and to it I would refer the reader for details which I have not the space to reproduce here.
This author first remarks:
"The best thermometer we can use to test the character of a climate is the flora and fauna which lived while it prevailed. This is not only the best, but is virtually the only thermometer available when we inquire into the climate of past geological ages. Other evidence is always sophisticated by the fact that we may be attributing to climate what is due to other causes; boulders can be rolled by the sea as well as by sub-glacial streams, and conglomerates can be formed by other agencies than ice. But the biological evidence is unmistakable; cold-blooded reptiles cannot live in icy water; semi-tropical plants, or plants whose habitat is in the temperate zone, cannot ripen their seeds and sow themselves under arctic conditions.... We may examine the whole series of geological horizons, from the earliest Palaeozoic beds down to the so-called Glacial beds, and find, so far as I know, no adequate evidence of discontinuous and alternating climates, no evidence whatever of the existence of periods of intense cold intervening between warm periods, but just the contrary. Not only so, but we shall find that the differentiation of the earth's climate into tropical and arctic zones is comparatively modern, and that in past ages not only were the climates more uniform, but more evenly distributed over the whole world."
Without attempting to follow through the whole series of formations we may note a few characteristic statements of the text-books. Thus Dana says of the Cambrian: