Dr. Bu Riche Treller —Three Glaciations of Switzerland. 35 



only 1° C. is sufficient to cause the snow-line to descend about 300 

 feet while the glaciers advance, unite, and spread at a much more 

 rapid rate. A gradual drop of the present mean temperature of 

 sub-Alpine Switzerland of 2° C, viz. from 9° to 7° C. would suffice 

 to bring the glacier-terminals from their present mean level of 3800 

 feet down to 2800 feet, and a further drop to 4° C. or 39° P. would 

 bring them again to the level of the lakes of Constance, Zurich, 



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Lucerne, Thune, and Geneva. But climatic changes of such com- 

 parative magnitude, so far as they are dependent on purely local 

 phenomena, could only be brought about by a new gradual upheaval 

 or upward thrusting of the Alps, which would largely increase the 

 area, and therefore the quantity of precipitation ; in the meantime, 

 there is now indisputable evidence of three glaciations having 

 already taken place. /Sufficient unto the day is the evil thereof. 



