Researches on Exiating Glaciers. 241 



reasons which caused me to reject the theory of Saussure, 

 and to deny the melting action of terrestrial heat on the bot- 

 tom of a glacier. This negation leads to a consequence of 

 great moment for the theory of the motion of glaciers, the 

 immobility of glaciers in winter ; and it does so in the fol- 

 lowing manner : — If, as I suppose, the motion of glaciers 

 be really produced by infiltration and the daily congelation of 

 the rain-water or of the water resulting from the melting of 

 the superficial ice, glaciers ought to be stationary so long as 

 there is no water at their surface, consequently during the 

 whole winter, because they are destitute of water at that sea - 

 son. If, on the contrary, it be the terrestrial heat, which, by 

 melting glaciers at their base, produces partially or entirely 

 their sliding movement, this action ought to be perceptible 

 at all periods of the year, independently of the seasons and of 

 the oscillations of the temperature of the atmosphere ; and if 

 this last be the case, glaciers ought to furnish water during 

 the whole year, in winter as in summer. Saussure himself 

 followed this train of reasoning ; and in order to arrive at a 

 solution of the question, he went during winter to the valley 

 of Chamounix, and witnessed the escape of pretty considerable 

 streams from the arched terminations of glaciers, although 

 they were less abundant than in summer. Thenceforward 

 the point appeared to him to be settled. It was too cold 

 for the sun to have the power of melting the ice ; else- 

 where, the whole country was buried under a thick crust of 

 snow. It was, therefore, there could no longer be any doubt, 

 the terrestrial heat which melted the glaciers beneath. Ne- 

 vertheless, one reflection could not but present itself : if we 

 consider that glaciers generally occupy the bottom of deep 

 valleys, we must admit that it is there where the springs 

 which circulate in the interior of the mountains ought to have 

 their exit. The presence of water does not then prove abso- 

 lutely that it results from the melting of the glacier. On the 

 other hand, if the action of terrestrial heat exercise its in- 

 fluence in winter as in summer, it ought to do so on all gla- 

 ciers, and not one of them should be dry. Further, the wa- 

 ter of glaciers has a peculiar character, which distinguishes it 

 from spring-water ; it is always mixed with earthy matter, 



