352 Prof. Bischoff' on the Temperature of 



of the soil beneath the glacier, and that which it would other- 

 wisehave, considering only its latitude and elevation above the sea. 

 The difference between these two is the expression in degrees 

 of the thermometer, for the quantities of heat communicated 

 from the earth to the glacier lying upon it. The quantity of 

 ice melted from the under surface of a glacier, in a certain time, 

 would give an exact measure for the quantity of heat radiated 

 from the earth. But we have no means of ascertaining that 

 quantity with any degree of certainty. It is well known that 

 stones, wood, corpses, &c. which fall into holes and fissures in 

 the ice, but do not reach the bottom of the glacier, are again 

 brought to the surface by the melting of the ice on its surface.* 

 In the year 1S2S, Hugi buried several stones from ten to 

 twelve feet deep in a glacier, and covered them in with ice, and 

 the following year they were all on the surface again. This 

 would give a measure for the quantity of ice melted away from 

 the upper surface, and the absolute sinking of the stones would 

 yield a measure for the melting of its under surface, did not the 

 movement of the glaciers (the openings of the fissures), &c. oc- 

 casion frequent changes in the position of the stones,-f" and if the 

 ano-le which the under surface of the glaciers makes with the 

 horizon were not unknown. % 



* The common people in the Alps say, that the glacier will not suffer any- 

 foreign matter to remain in its interior. And, in fact, I have in vain endea- 

 voured to discover even a single stone in the exposed masses of ice at the ex- 

 tremity of the glaciers. This is very plainly exemplified at the upper Grin, 

 delwald glacier, where perpendicular walls of ice, of more than 100 feet in 

 height, are exposed to view. See Bisselx, in Gilbert's Anna!., vol. ixiv. p. 1 98. 

 However, at the lower Grindelwald glacier, the walls of ice are seen to be tra- 

 versed by stripes, coloured brownish by earth. 



t Kamtz, in Schweigger — Seidel's Journal, vii. p. 2C1. 



X From Mr Stahlin's daily observations of the height oi the Rhine at jBa- 

 se;, continued from 1 809 to 1820, Escher calculates (Gilb. A nnaL, Ixx. 202) 

 that the Rhine carries off one billion and 46,000 million cubic feet of water 

 yearly out oi Switzerland. Now, supposing only one-half of this quantity to pro- 

 ceed immediately from the glaciers, and that of the fifty square German miles, 

 which are said by Ebel (Part iii. p. 121) to be occupied by the glaciers of the 

 Alps between Mont Blanc and the frontiers of Tyrol, only twenty squai'e 

 miles are tributary to the Rhine ; then, if the specific gravity of the water 

 be considered equal to that of the ice of the glaciers, we find that, on an 

 average, a mass of ice of fifty feet in thickness is melted away yearly from 



