Hot and Thermal Springs. 357 



therefore, obliged to have recourse to the above mentioned 

 sources of heat, in order to account for this high temperature. 



But if, as was to have been expected, a priori, the tempera- 

 ture of the water precipitated into the clefts of the glacier, is 

 32°.0, and if, as our experiments seem to shew, the highest 

 temperature which it assumes before its exit at their lower ex- 

 tremity, is 35°.9, then can the temperature of the soil beneath 

 the glaciers nowhere be much higher than 32°.0. This only re- 

 fers to the warmer seasons ; but as beneath the glaciers the earth 

 is protected from the cooling effects of radiation, as even a very 

 considerable degree of cold in the atmosphere is not capable of 

 penetrating through a mass of ice of several hundred feet m 

 thickness, and as, during the winter, the cold is almost, or per- 

 haps entirely, prevented from penetrating into the caverns in the 

 ice, by their being choked up with snow and ice, the tempera- 

 ture of the soil under the glacier will, even in winter, hardly be 

 reduced below 32°. The yearly mean temperature of the soil 

 under glaciers is, therefore, without doubt 32°. 



The lower extremity of the lower Grindelwald glacier, lies, 

 according to my barometrical measurement, at an elevation of 

 2989 feet above the surface of the sea, in a region where the 

 mean temperature of the soil is much above 32°.0. Up to the 

 Eismeer, at the foot of the Vischhorner, the glacier rises to a 

 height of 2140 feet. So that even the Eismeer, at a height of 

 5129 feet above the level of the sea, lies in a region where the 

 mean temperature of the soil is above 32°.0. Up to this limit, 

 then, the glacier may be melted away from underneath, but not 

 above this. 



In Grindelwald, 248 feet above the lower extremity of this 

 glacier, I found the temperature of the soil one foot below the 

 surface, on the 26th August, to be 56°. 7 ; on the Metterberg, 

 near the Eismeer, and on the same level with it, it was 45°.5. 

 At the former place the mean temperature will, therefore, not 

 be much above 43°.2, at the latter hardly 36°.6. 



Glaciers may be indirectly melted away from underneath at 

 the expense of the internal heat of the earth, when, in the higher 

 regions of the glacier water descends through cracks and fissures 

 deep into the earth, and, having there acquired a higher tem- 

 perature, reappears beneath the glacier at a lower point. This 



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