The Arctic Home in the Vedas c5.21

c5.21

It was once supposed that the duration of each of Dr. Croll’s different periods admirably fitted in with the geological evidence, and fully corroborated the estimates of time supposed to be required for the extensive geographical changes which accompanied the Glacial and Inter-Glacial periods. But geologists have now begun to take a more sober view of these extravagant figures and calculations. According to Croll’s calculation there were three periods of maximum eccentricity during the last three million years, and there should, therefore, be three periods of glaciation corresponding to these, each including several Glacial and Inter-Glacial epochs. But there is no geological evidence of the existence of such Glacial epochs in early geological eras, except perhaps in the Permian and Carboniferous periods of the Palæozoic or the Primary age. An attempt is made to meet this objection by replying that though the eccentricity was greatest at one period in the early geological eras, yet as the geographical distribution of land and water was then essentially different from what it was in the Quaternary era, the high value of the eccentricity did not then produce the climatic changes it did in the Pleistocene period. This reply practically concedes that the high eccentricity of the earth’s orbit, combined with the occurrence of winter when the earth is at aphelion, is not by itself sufficient to bring about a Glacial period; and it may, therefore, be well urged that a Glacial epoch may occur even when the eccentricity is not at its maximum. Another point in which Dr. Croll’s theory conflicts with the geological evidence is the date of the close of the last Glacial epoch, as ascertained, by the American geologists, from estimates based on the erosion of valleys since the close of the last Glacial period. It is pointed out in the last chapter that these estimates do not carry the beginning of the Post-Glacial period much further than about 10,000 years ago at the best; while Dr. Croll’s calculation would carry it back to 80 or 100 thousand years. This is a serious difference, and even Prof. Geikie, who does not entirely accept the American view, is obliged to admit that though Dr. Croll’s theory is the only theory that accounts for the succession of Glacial epochs, and, therefore, the only correct theory, yet the formula employed by him to calculate the values of the eccentricity of the earth’s orbit may be incorrect, and that we may thus account for the wide discrepancy between his inference and the conclusions based upon hard geological facts, which cannot be lightly set aside.¹