348 Prof. BischofF om the Temperature irf 



can take place, the original temperature of the soil may be some- 

 what raised. At such elevations, therefore, where the mean 

 temperature of the soil is 32°, glaciers can only be melted on 

 their upper surface, and during the warmer seasons, but in the 

 winter no water can possibly flow from them. 



If the mean temperature of the soil in the Alps, at an eleva- 

 tion of 6165 feet, is 32° F. (see Chap. XVIII), glaciers which lie 

 at that height can no longer be melted away from underneath.* 

 It would be very interesting, for the further investigation of 

 this question, to ascertain the height in various parts of the 

 Alps, at which the mean temperature of the soil is zero. 



The lower extremity of the great Lanimern glacier, on the 

 Genimi, in Switzerland, is situated about 7000 feet above ihe 

 surface of the sea.t The mean temperature of the soil at that 

 place must, therefore, be about 34°.47. On the 5th September 

 1835, at a ^ew hundred feet from the glacier, and eight feet from 

 the bed of the brook, which at that time was dry, I found the 

 temperature of the soil at one foot from the surface to be 41°.9; 

 whilst at the highest point of the Pass of the Gemmi, which has 

 about the same elevation above the sea, it was only 38°.5. The 

 former of these must, therefore, have been 44°. 57, and the lat- 

 ter 41°.27 above the mean, a result which nearly accords with 

 the observations made at the depth of one foot, communicated 

 in Chap. VIII. But I also observed the temperature of fifty- 

 one fresh- water springs on the Spital Matte, 5887 feet above 

 the sea on the 3d September, and found the coldest of them to 

 be 37°. 8, and as, according to my observations on the tempera- 

 ture of the springs of the mountains in the vicinity of my resi- 

 dence (see Chap. XVIII), this temperature must have been 



• Hugi (see Berghaus Anrial. iii. 290), has given the height above the sea 

 of the lower extremities of twelve glaciers in Switzerland. Among these the 

 Oberaar glacier (7980 feet above the level of the sea) is the only one which 

 would not melt away from underneath ; all the rest are so situated as to reach 

 below the limit of 6165 feet, and consequently into regions where the mean 

 temperature is above 32°.0. 



f I found by my barometrical measurement, made between 200 and 300 

 feet above its lower extremity, that its height was 7244 feet above the level 

 of the sea. 



