Page:Popular Science Monthly Volume 30.djvu/16

6 prevailed over all the Arctic regions. At the same time the tropical lands were locally if not generally lower than now, since in the West Indies and on the borders of the Gulf of Mexico are broad sheets of marine Tertiary; Second, because all evidence is wanting of high northern lands during the ice period; and, at least during a portion of the time when an arctic temperature prevailed from New York northward, the sea stood much higher than now, receiving and precipitating the Champlain clays—the fine flour ground by the land glaciers—and burying in them arctic shells. *

In the article referred to I have shown that no terrestrial causes yet suggested are adequate to produce an ice period, and that we are compelled to look to some cosmical cause for an explanation of its occurrence.

Recently a voluminous and elaborate review of the subject has been published by Professor J. D. Whitney, with the title of "Later Climatic Changes," the object of which is to prove that there has never been an ice period, properly speaking. To establish this, it is claimed that ice has little or no eroding power; and the few ancient glaciers, of which the evidence can not be ignored or sophisticated, are considered as the products of local causes. Following Lecoq and others, Professor Whitney claims that since snow and ice are forms of moisture evaporated elsewhere by heat, the extension of glaciers at any time or place is simply an effect of increased evaporation—of heat and not cold—and hence if there ever was an ice period, meaning a time when glaciers were more widespread than now, it must have been a warmer period than the present; forgetting, apparently, that increased congelation is the only necessary feature in the increase of glaciers, for, without this, increased evaporation and precipitation would be inoperative. Only a few of many facts need be cited to show that this theory is untenable: 1. Glaciers are now confined to altitudes and latitudes where the temperature is low—Alpine summits and the Arctic and Antarctic Continents. To extend the reach of the glaciers now existing, and to reproduce them where they existed formerly but are now absent, it would be only necessary to widen and intensify the conditions upon which their existence depends, viz., lower the temperature and cause the present precipitation to be more generally fixed in ice and snow. A single example will be sufficient to prove the truth of this statement. On the Cascade Mountains in Oregon we find a copious precipitation of rain and snow, but no ice where great glaciers formerly existed. The snow-fall is so heavy that the snow-line is brought down to an altitude of seven thousand feet above the ocean, and there the temperature is high enough to permit the vigorous