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Dunker, of Cassel, and H. von Meyer, in an excellent monograph on the Wealdens of Hanover and Westphalia, have shown that they correspond so closely, not only in their fossils, but also in their mineral characters, with the English series, that we can scarcely hesitate to refer the whole to one great delta. Even then, the magnitude of the deposit may not exceed that of many modern rivers.
It usually occurs in regular horizontal beds, and is occasionally intersected by deep valleys, such as those of Sortino and Pentalica, in which are numerous caverns. The fossils are in every stage of preservation, from shells retaining portions of their animal matter and colour to others which are mere casts.
The identity of so many of the fossils with Miocene species of Central Europe and Italy not only proves that the climate of Greenland was much warmer than it is now, but also renders it probable that a much more uniform climate prevailed over the entire northern hemisphere.
Had been greatly struck from about the month of previous March on character of South American fossils and species on Galapagos Archipelago. From March, 1837, then, Darwin, not without many misgivings and fluctuations of opinion, inclined towards transmutation as a provisional hypothesis.
For, as the species of organic beings contemporaneously inhabiting remote regions are distinct, the fossils of the first of several periods which may be preserved in any one country, as in America for example, will have no connection with those of a second period found in India, and will therefore no more enable us to trace the signs of a gradual change in the living creation, than a fragment of Chinese history will fill up a blank in the political annals of Europe.
"Ah," he said, with superb up-to-date pity, "you are still talking about Trafalgar;" and I could see that Trafalgar and I were thenceforth on the top shelf of fossils in the collections of his memory. This point of view was held by very many. "You won't find much to say about history," was the direct discouraging comment of an older officer.
It is now known that some kinds of fossils are always found in the oldest rocks, and in them only; that some kinds are always found in the newest rocks, and in them only; that some fossils are rarely or never found lower than certain layers; that some fossils are rarely or never found higher than certain other layers. So this fossil arrangement is growing into quite a history of the past.
Two of the men go out with the barometer to climb the cliff at the foot of Whirlpool Canyon and measure the walls; another goes on the mountain to hunt; and Bradley and I spend the day among the rocks, studying an interesting geologic fold and collecting fossils. Late in the afternoon the hunter returns and brings with him a fine, fat deer; so we give his name to the mountain Mount Hawkins.
Of the fact there can be no doubt, for it is not difficult to adduce satisfactory evidence of the shoal-like character of the Silurian deposits of the State of New York; their horizontal position, combined with the gradual recession of the higher beds in a southerly direction, leaves no doubt upon this point; and in the case of the jurassic formation alluded to above, the combination of the crinoids with fossils common upon coral reefs, and their presence in atolls of that period, are satisfactory proofs of my assertion.
Simple creatures belonging with our present crab and snail had begun to make their appearance, but they were not as abundant as we find them later on. The third group of the mollusks to which the nautilus and squid of to-day belong is very abundantly represented in the Silurian by fossils with coiled-up shells. As for the plant life of the time, it is exceedingly difficult to say much about it.
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