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Show CHAPTER VI. Proofs that the climate of the Northern hemisphere was formerly hotter-Direct proofs from the organic remains of the Sicilian and Ital~un strata~Proo:s from analogy derived from extinct Quadrupeds-Iml>ecldmg of Ammals m Icebergs-Siberian Mammoths-Evidence in regard to tempcratur<·, from the fossil remains of tertiary and secondary rocks-From the Plants of the Coal formation. 'J.'IIAT the climate of the northern hemisphere has undergone an important change, and that its mean ar~nual te~pe~·ature must once have resembled that now expenenced w1thm the tropics, was the opinion of some of the first naturalists who investigated the contents of ancient strata. 'Their conjecture became more probable when the shells and corals of the secondary rocks were more carefully examined, for these organic remains were found to be intimately connected by generic affinity with species . now living in warmer l~titudes. At a later period, many rept1les, such as turtles, tor!mses, and large saurian animals, were discovered in the European strata in great abundance ; and they supplied new and powerful arguments, from. analogy, in support of the doctrine, that the heat of the climate had been great when our secondary formations were deposited. Lastly, when the botanist turned his attention to the specific determination of fossil plants, the evi· deuce acquired the fullest confirmation, for the flora of a country is peculiarly influenced by temperature; ·and the ancient vegetation of the earth might, more readily than the forms of animals, have afforded conflicting proofs, had the popular theory been without foundation. 'Vhen the examination of animal and vegetable remains was extended to rocks in the most northern parts of Europe and North America, and even to the Arctic regions, indications of the same revolution in climate were discovered. It cannot be said, that in this, as in many other departments of geology, we have investigated the phenomena of former CHANGE OF CLIMATE, 93 eras, and negl~cted those of the present state of things. On t?e contrary, SI?ce the first agitation of this interesting question, the accessiOns to our knowledge of living animals and plants have been immense, and have far surpassed aU the data previously obtained for generalizing, concerning the relation of certain types of organization to particular climates. The ... tropical and temperate zones of South America and of Australia have been explored ; and, on close comparison, it has been. fo~nd, that scarcely any of the species of the animate creatwn m these extensive continents are identical with those inhab~ting th~ old world. Yet the zoologist and botanist, well ~cquamted With the geographical distribution of organic beings In other parts of the globe, would have been able if distinct groups of species had been presented to them 'rrom these regions, to recognise those which had been collected from latitudes within, and those which were brought from without the tropics. . ~e~ore we attempt to explain the probable causes of great VICISSitudes of temperature on the earth's surface we shall take a rapid view of some of the principal data wl~ich appear to warran~, to the utmost extent, the popular opinions now entertat?ed on th.e subject. To insist on the soundness o~ the mference, is the more necessary, because some zoologists have of late undertaken to vindicate the uniformity of ~he l~ws of nature, not by accounting for former fluctuations m ~hmate, but by denying the value of the evidence on this subJect*· !t is not merely by reasoning from analoc:ry that we are led to I n~ e r a d. I' m·m utw· n ?f temperature in the co limate of Europe ; there are direct proofs m confirmation of the same doctrine in the only coun t r1. es hI' t h erto m. vest1. gated by expert geologists ' where we could expect to meet with direct proofs. It is not in England or Northern France, but around the borders of the Mediterranean, from the South of Spain to Calabria, and in the islands of the Mediterranean, that we must look for conclusive evi-dence on thi. s quest·i on; J~. Or I· t I·s not m· strata, where the N * ~~e two articles by the Rev. Dr. Fleming, in the Edinburgh New Phil. J ouru, 0 • "'' P· 277, April, 1829; and No. 15, I'· 651 Jan. 1830, |