470 Transactions. — Geology. 



Josef and Tasman Glaciers and they will disappear in a defi- 

 nite time, as estimated by the average annual temperature of 

 the area they now occupy ; and the same thing must have 

 held good in Pleistocene times if we assume that the same 

 physical conditions existed then as now. But Geikie says 

 that the Pleistocene period was one of depression in Europe, 

 although, so far as Switzerland is concerned, Heer appears to 

 think that the Alps were somewhat higher than at present. 

 In any case, if glaciers covered the areas they are said to have 

 covered in Europe, America, and elsewhere, there must have 

 been special areas for the accumulation of snow to supply 

 those glaciers. Nor can we conceive of such areas being below 

 the " snow-line," as it is at present understood. But was the 

 snow-line higher or lower during Pleistocene times ? This 

 question is a difficult one to answer, because, if the tempera- 

 ture of the earth was warmer — which has been assumed — 

 it follows that the " snow-line " would be, on the average, 

 higher. 



The question of climate, however, is one of much diffi- 

 culty, as the distribution of the land, the height of moun- 

 tains, the direction of winds, of currents, and of mountain- 

 chains, all tend to modify and influence the temperature of a 

 country. The Gulf Stream that washes the western shores 

 of Europe causes countries like the British Isles, Denmark, 

 and Norway to enjoy a temperature much higher than what 

 is enjoyed by the people along the eastern shores of North 

 America in similar latitudes, and whose shores are washed 

 by the arctic return-current. It is estimated that not less 

 than half the heat received from the sun within the torrid 

 zone is carried by ocean-currents to the north and south, for 

 diffusion among the colder waters of the ocean. But it is 

 quite possible, and, indeed, very probable, that the land- and 

 water-areas were differently arranged during Pleistocene 

 times from what they now are. A cold current passing along 

 western Europe would so modify the climate that glaciers 

 would certainly increase in size, and the conditions of the 

 countries named above would become greatly modified. 

 Assuming that the glaciers have existed in Europe, America, 

 and elsewhere during Pleistocene times, and assuming also 

 that the facts as to elevation, depression, and temperature are 

 such as have been stated, it seems hardly possible to harmonize 

 the differences except on the supposition that some cause 

 outside the earth itself was operating to bring about the con- 

 ditions named. 



Many theories have been offered to account for the in- 

 coming of a cold period and the return to a normal period of 

 temperature over an important portion of the earth's surface. 

 Heer says, in his " Primeval World," that " from the Car- 



