Hot and Thermal Springs. 363 



spring rains, which re-open the fissures in the ice, whicli had 

 been stopped up with snow during the winter, and carry down 

 great quantities of water, which burst a passage through the 

 choked caverns. But if the caverns should be thus burst open 

 before the fissures had been cleared out by the rains, the passage 

 could only have been forced by the water which had collected 

 under the glacier during the winter.* But as in glaciers which 

 rise to a considerable height, the lower extremity lies in a much 

 warmer region than the clefts into which the waters are precipi- 

 tated, it might be expected that the caverns would be reopened 

 sooner than the clefts in the glacier. It is not beyond the power 

 of human observation, in the spring, to ascertain the real fact 

 concerning this phenomenon. Well informed chamois hunters, 

 who ascend the glaciers at almost all seasons, would be the 

 most proper persons to undertake such observations. 



There is another method, which, if pursued with caution, 

 would give some information respecting the melting of the gla- 

 ciers from underneath, — namely, if we suppose the glacier 

 streams only to proceed from three sources ; first, from springs 

 and streams which sink into the glacier in higher regions ; se- 

 condly, from the melting of the ice during the summer months 

 on the upper surface of the glaciers ; and, thirdly, from the ice 

 melted away from the under surface of the glaciers, their con- 

 tents of fixed substances must be different in the different sea- 

 sons. The quantity of fixed substances contained in the streams 

 which fall in the course of a year into the glaciers, as well as in 

 the springs which rise underneath them during the same period, 

 may be considered as constant. The water resulting from the 

 melting of the glaciers on their upper surface during the warm 

 season, can contain scarcely a trace of fixed substances, and that 

 only when the glacier is covered with heaps of rubbish (guffer- 

 linien). However, as these waters are precipitated into the fis- 

 sures in the ice, and thus unite beneath the glacier with those 

 of the streams and springs, they are enabled to take up fixed 



• Subterranean accumulations of water actually exist in the winter accord- 

 ing to £bel (part ii. p. 96), between the Valsorc glacier and the perpendicular 

 wall of Monl noir, for a hole in that neighbourhood (called the Gouille a Vassu), 

 104 feel deep, remains from the autumn till July full of water, which in 

 July breaks through under the Vahori glacier, and forms ice caverns. 



