240 Intelligence, and Miscellaneous Articles. 



penetration of the water, discusses the question from a more theo- 

 retical standpoint, and concludes that the assumption of the im- 

 permeability of the glacier is contrary to fact. He promises, further, 

 to make this a special subject of observation at a later period. 



In regard to the cause of the movement of glaciers, M. Forel 

 places himself on the side of Hugi and Grad in supporting the 

 theory of expansion, although modifying somewhat their hypo- 

 thesis. On the old ddatation theory, it was the expansion of the 

 water contained in the capillary fissures at the moment of their 

 solidification to which the glacial movement was supposed to be 

 due. According to the view of M. Forel, however, this special 

 expansion plays a subordinate part ; and it is rather the gradual 

 increase in volume of the crystalline grain, due to the molecular 

 affinity which causes a crystal to grow in the mother-liquor in which 

 it is placed. 



In discussing further the application of the hypothesis, a distinc- 

 tion is made as to the course of events during the youth and during 

 the old age of the glacier. The glacier may be divided into three 

 parts. The first is in the elevated region where the glacier has its 

 commencement, that of the neve. Here the heat of summer is 

 not sufficient to melt the whole volume of the snow which falls 

 during the year ; only a part of the snow is consequently trans- 

 formed into water ; and this penetrates into the layers below, and 

 is solidified there : the temperature is much below the freezing- 

 point. This is the region of the infancy of the glacier. Following 

 this comes the line of separation, where the heat of summer is just 

 sufficient to melt the winter's snow, and there is no excess of heat 

 to attack the ice. 



The second stage (that of the youth of the glacier) is found 

 below this line of separation, where the summer's heat not only 

 melts the snow but also partially melts the ice ; the water so formed 

 is absorbed and assimilated by the ice ; and the temperature below 

 the surface is, even at the end of summer, below zero. In this 

 region the glacier is increasing in volume, and consequently moving 

 downward. Then follows a second line of separation, where the 

 water absorbed is all used in the increase of volume of the glacial 

 grain. At this point the subglacial torrent has its origin ; and at 

 the summer's end the temperature is at 0°. 



The third stage is that of the old age of the glacier, where the 

 supply of water exceeds that needed to bring the temperature of 

 the ice back to 0° ; the excess of water flows off in the glacial 

 streams. The temperature of the ice is at 0° during the summer ; 

 and the excess of the summer's heat goes to cause the melting and 

 destruction of the glacier. 



In concluding his interesting memoir, the author promises to test 

 his hypothesis by further observations and experiments, bearing 

 especially upon the questions as to the comparative size of the crys- 

 talline grains in the different parts of a glacier, and as to the possi- 

 bility of the penetration of the surface-water into the mass of the ice. 

 ■ — Silliman's American Journal. August 1882. 





