. Carnegie Institution of Washington publication. CLIMATES OF GEOLOGIC TIME. 267 ment of the entire organic world of the Pleistocene lands, other than that of the tropics. More than once man and his organic surroundings have been forced to wander into new regions; the life of cool to cold climates has dispossessed that of milder temperatures, and with each moderation of the climate the hardier floras and faunas have advanced with the retreating glaciers, or become stranded and isolated in the mountains. As the organic world is dependent upon sunlight, temperature, and moisture, it is not diffi
. Carnegie Institution of Washington publication. CLIMATES OF GEOLOGIC TIME. 267 ment of the entire organic world of the Pleistocene lands, other than that of the tropics. More than once man and his organic surroundings have been forced to wander into new regions; the life of cool to cold climates has dispossessed that of milder temperatures, and with each moderation of the climate the hardier floras and faunas have advanced with the retreating glaciers, or become stranded and isolated in the mountains. As the organic world is dependent upon sunlight, temperature, and moisture, it is not difficult to see why these same factors are essential to man and his civilization. PERMIC GLACIATION. Hardly had the Pleistocene glacial climate been proven when geologists began to point out the possibility of earlier ones. An enthusiastic Scotch writer. Sir Andrew Ramsay, in 1855 described certain late Paleozoic conglomerates of middle England, which he said were of glacial origin, but his evidence, though never completely gainsaid, has not been generally accepted. In the following year, an Enghshman, Dr. W. T. Blanford, said that. Fig. 88.—Paleogeography and Glaciation of Early Permic Times. the Talchir conglomerates occurring in central and southern India were of glacial origm, and since then the evidence for a Permic glacial period has been steadily accumulating. The land of ancient tills (tiUites of geologists) is Africa, and here in 1870 Sutherland pointed out that the conglomerates of the Karoo formation were of glacial origin, and, further, that they rest on a land surface which has been grooved, scratched, and polished by the movement of glaciers. Australia also has Permic glacial deposits. It is only very recently that the evidence found in many places in the southern hemisphere has become widely known, but so convincing is this testimony that all geologists are now ready to accept the conclusion that a glacial chmate was as widespread in Permic time as was that of the.
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