6 THE POPULAR SCIENCE MONTHLY. 



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 pre- 

 cipitating 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 Cli- 

 matic 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 con- 

 sidered 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 congela- 

 tion is the only necessary feature in the increase of glaciers, for, with- 

 out 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 exist- 

 ing, and to reproduce them where they existed formerly but are now 

 absent, it would be only necessary to widen and intensify the condi- 

 tions 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 co- 

 pious 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 



* The Champlain clays about Xew York are near the present sea-lcvcl. At Croton 

 Point they are 100 feet higher; at Albany, 200 feet; on Lake Champlain, 350 feet; at 

 Montreal, 500 feet; on Labrador, 800 feet ; on Davis Strait, 1,000 feet; and at Tolaris 

 Bay, 1,600 feet above the ocean. 



