S6© l^rof. BischofK on the Temperature of 



iwhen in the spring, water falls from the Lotsch glacier over a 

 certain rock, which he pointed out to me, three days afterwards 

 it flows out at that periodical spring, which has five outlets, all 

 situated very near together, and, indeed, in such abundance 

 that it might be used for driving a mill. This usually takes 

 place in June ; however, it de|>en(Is upon the earlier or later 

 commencement of the summer. These springs are also more 

 copious the warmer the summer is. When the water ceases 

 flowing over the rocks, the springs also, after three days, disap- 

 pear, and this usually happens at the end of August, or the be- 

 ginning of September. During my stay at LeucTcerhad^ the 3d 

 and 4lh of September, the spring only flowed from one of its 

 onlets, and I learned from an engineer of the place, that the 

 others had only ceased flowing a few days before. And, on the 

 5th, I observed no more water running over the rock. I have 

 the less rcas n to doubt the information of my guide, as the low 

 temperature of the spring (41°. 4) can only be accounted for by 

 supposing it to come either from a great height or out of a gla- 

 cier. In the latter case, it can only proceed from the meltmg 

 of the ice from the upper surface of the glacier during the sum- 

 mer. According to Hugi the lower extremity of the liOtsch 

 glacier lies 5802 feet above the level of the sea, and conse- 

 quently, according to Chap. XVIII., at an elevation where the 

 mean temperature of the soil is 32°.0. 



\n, (it may therefore be assumed, that the glaciers in the ^/p.?, 

 which lie more than €165 feet above the sea, are no longer melt- 

 ed away from underneath, by the internal heat of the earth ; 

 but that they are melted only on the upper surface by the heat 

 of summer, and by rains.* Thus, on the upper surface, a layer 

 of ice, although, perhaps, a somewhat thin one, will be formed, 

 under which there will be nothing but soft snow to an unknown 

 depth.-f- The thickness of this covering of ice will, of course, 

 depend on the depth to which the water, resulting from the 

 melting of the snow during the day, sinks and freezes during 

 the night. 



" On the heights up to which the yearly fall of snow is melted away again, 

 see Escher, p. 123. 



t Von Buch in Gilbert's Annul., vol. xli. 15. l)e Saussure, Voyages, ii 

 214,§5H0. 



