288 THE POPULAR SCIENCE MONTHLY. 



and Eastern Canada were completely covered, and probably deeply 

 buried, in sheets of ice and snow. In the British Islands and Norway 

 the inscriptions made by ancient glaciers are scarcely less broad and 

 profound, and it is even conjectured that the bed of the shallow North 

 Sea is itself glaciated throughout. These evidences of vast accumu- 

 lations of ice and snow on the borders of the Atlantic have led some 

 theorists to suppose that the Ice period was attended, if not in part 

 caused, by a far more abundant evaporation from the surface of the 

 Atlantic than takes place at present ; and it has even been conjectured 

 that submarine volcanoes in the tropics might have loaded the atmos- 

 phere with an unusual amount of moisture. This speculation seems 

 to me, however, both improbable and superfluous ; improbable, be- 

 cause no traces of any such cataclysm have been discovered, and it is 

 more than doubtful whether the generation of steam in the tropics, 

 however large the quantity, would produce glaciation of the polar 

 regions. The ascent of steam and heated air loaded with vapor to 

 the altitude of refrigeration, would, as it seems to me, result in the 

 rapid radiation of the heat into space, and the local precipitation of 

 unusual quantities of rain ; and the effect of such a catastrophe would 

 be slowly propagated and feebly felt in the arctic and antarctic re- 

 gions. The hypothesis is superfluous, because all we want, to restore 

 the conditions recorded in the glaciated area, is simply a depression 

 of temperature ; by this the climate of Greenland, with all the attend- 

 ing phenomena, would be brought down on both sides of the Atlan- 

 tic to the lowest point where the average annual temperature of 

 Greenland prevailed. 



This is, I think, proved by the condition of Greenland itself; re- 

 mote as it is from evaporating surfaces of warm water, the pre- 

 cipitation of moisture upon that continent is, however, sufficient to 

 cover it deeply under sheets of snow and ice ; the whole interior be- 

 ing occupied by a continental glacier ; and it is easy to see that, with 

 a depression of the average annual tenq:)erature 10, the highlands of 

 Labrador would be brought into the same condition. With a still 

 .further depression the elevated portions of New England, the Adi- 

 rondacks, and the highlands north of the lakes, would be completely 

 encased in snow and ice. If the flow of the St. Lawrence were ar- 

 rested, and the annual precipitation of the region drained by it were 

 congealed, and retained from year to year, glaciers would soon form, 

 and creep down from the highlands into the valleys, until the basins 

 of the great lakes and the troughs of the Hudson and St. Lawrence 

 would be completely filled with ice. On the eastern side of the At- 

 lantic this state of things would be still more rapidly reached, inas- 

 much as, from the effect of the Gulf Stream, the coast climate is con- 

 siderably more moist. 



So far, then, as the region bordering the North Atlantic is con- 

 cerned, a simple depression of temperature from any cause whatever, 



