238 DISCUSSIONS IN CLIMATOLOGY. 



of water to that of ice must be much less than on 

 Greenland. The quantity of ice melted in the Antarctic 

 regions from all causes, we have seen, cannot be great; 

 and of that quantity the greater part must be re- 

 solidified long before it can reach the sea. I can 

 hardly think that it will be regarded as an over- 

 estimate to affirm that at least one-half the precipita- 

 tion must reach the sea in the form of ice. Assuming 

 the annual precipitation to be no greater than that of 

 Greenland, viz., 1 foot per annum, the quantity carried 

 off in the form of ice would in this case be 6 inches. 

 At what rate, then, would the edge of the cap require 

 to be advancing outwards in order to discharge this 

 6 inches of ice? If we assume the cap to extend on 

 an average down to latitude 70°, its area will be about 

 5,940,000 square miles, or 165,611,000,000,000 square 

 feet. A layer 6 inches thick covering that area would 

 contain 82,805,500,000,000 cubic feet of ice. The 

 circumference of the cap is 45,300,000 feet, and its 

 thickness at the edge is assumed, of course, to be 1400 

 feet. Were the ice, therefore, to move outwards 

 at the rate of 1300 feet per annum, and to break 

 up into bergs as it advanced, the quantity of ice 

 discharged annually in the form of icebergs would be 

 82,446,000,000,000 cubic feet, an amount equal to the 

 layer of ice 6 inches in thickness covering the area. 

 Consequently, if 6 inches of ice be carried annually off 

 the Antarctic continent, the edge of the cap must be 

 moving outwards at the rate of about a quarter of a 

 mile annually. Even supposing there were only 2 

 inches of ice discharged, the rate of motion would 

 require to be between 400 and 500 feet per annum. 



A quarter of a mile per annum cannot be regarded as 

 an improbable rate of motion for continental ice, when 

 we reflect that the Greenland ice has in some places a 



