228 DISCUSSIONS IN CLIMATOLOGY. 



melting-point corresponding to the pressure, and the 

 ice will always keep the floor at sensibly the same 

 temperature as itself. In short, in determining the 

 thickness of the Antarctic ice, underground heat does 

 not enter as an element into our calculations, and, so 

 far as the melting of the ice produced by the lowering 

 of the melting-point is concerned, the Antarctic ice at 

 the Pole may be a dozen of miles in thickness as 

 readily as 1400 feet. 



(b.) Melting produced by Work of Compression and 

 Friction.—" The pressure upon the deeper beds of 

 ice," says Sir Wy ville Thomson, " must be enormous ; 

 at the bottom of an ice-sheet 1400 feet in thickness it 

 cannot be much less than a quarter of a ton on the 

 square inch. It seems, therefore, probable that, under 

 the pressure to which the body of ice is subjected, a 

 constant system of melting and regelation maybe taking- 

 place, the water passing down by gravitation from 

 layer to layer until it reaches the floor of the ice- 

 sheet, and finally working out channels for itself 

 between the ice and the land, whether the latter be 

 subaerial or submerged." 



As has already been stated, no amount of pressure, 

 however great, has the least tendency whatever to 

 produce a melting of the ice by heat unless this 

 pressure performs work, and the quantity of ice 

 melted will then be, not in proportion to the pressure, 

 but to the work performed by the pressure. The 

 pressure here referred to, which is supposed to pro- 

 duce the melting, is the weight of the ice, or, in other 

 words, the force of gravity. 



When considering the amount of heat derived from 

 work of compression, it was proved that, in the case 

 of the Antarctic ice-sheet, the total amount of work 

 which can possibly be performed by gravity is deter- 



