216 DISCUSSIONS IN CLIMATOLOGY. 



part, if not nearly all, the heat possessed by the ice 

 must have been received through the upper, and not 

 the under, surface of the sheet. But what we are at 

 present concerned with is not so much the amount of 

 heat received by the ice as the temperature at which 

 the heat can maintain the ice. In short, the question 

 to be determined is — What is the temperature of the 

 Antarctic ice ? Now, if nearly all the heat possessed 

 by the ice has been received from the upper surface of 

 the sheet, the temperature of the mass must be mainly 

 determined by that of the surface, and cannot be far 

 above the mean temperature of the surface. If so, the 

 temperature of the ice must evidently be very 

 considerably below the freezing-point. 



(1.) If we suppose the heat to be transmitted from 

 the surface downwards by Conduction, we must 

 necessarily conclude that the surface is at a higher 

 temperature than the ice below, for conduction can 

 only take place from a hot to a colder body ; and this 

 process could not possibly maintain the mass of the 

 ice below at a temperature equal to the mean tem- 

 perature of the surface. The general tendency of 

 conduction would, therefore, be to keep the ice beneath 

 at a lower temperature than that at the surface. 



(2.) The work of Radiation, however, would proba- 

 bly have the opposite tendency. The heat received by 

 direct radiation from the sun could not possibly raise 



expansion of the ice, or the water in the act of freezing ; which is 

 sufficient to overcome perhaps any resistance whatever; and the 

 consequence seems to be, either that the water will freeze, and, by 

 expanding, burst the containing body, be it ever so thick and strong ; 

 or else, if the resistance of the body exceeds the expansive force of 

 the ice, or of water in the act of freezing, then, by preventing 

 the expansion, it will prevent the freezing, and the water will remain 

 fluid, whatever the degree of cold may be." (Trans. Roy. Soc. Edin., 

 vol. ii., p. 27). 



