CONDITIONS OF CONTINENTAL ICO. 237 



snow." Lieut. Wilkes, of the American Exploring 

 Expedition, estimated the snowfall to be 30 feet per 

 annum, and Sir James Ross says that during a whole 

 month they had only three days free from snow. The 

 very fact that perpetual snow is found at the sea-level 

 at lat. 64° S. proves that the amount of precipitation in 

 the form of snow in those regions must be great. 



But there is one circumstance which must tend to 

 make the snowfall near the Pole great, and that is the 

 inflow of moist winds in all directions towards it; and 

 as the area on which these currents deposit their snow 

 becomes less and less as the Pole is reached, this must 

 to a corresponding extent, as was shown in Chapter V., 

 increase the quantity of snow falling on a given area. 



Rate of Motion of the Antarctic Ice. — If we knew 

 the rate at which the edge of the Antarctic ice-cap is 

 advancing outwards, we could form a rough estimate 

 of the amount of snowfall on the continent. Or, 

 conversely, knowing the amount of snowfall, we could 

 tell approximately the rate at which the ice is moving 

 outwards. 



Dr. Rink calculates that the yearly precipitation on 

 Greenland in the form of snow and rain amounts to 

 about 12 inches. About 2 inches he considers is carried 

 off by ice into the sea, and the remaining 10 inches is 

 carried to the sea in the form of sub-glacial rivers. 

 He believes that the quantity disposed of by evapora- 

 tion is trifling. 



The amount of precipitation on the Antarctic con- 

 tinent is probably much greater than on Greenland. 

 On the Antarctic continent it is all in the form of 

 snow or hoar-frost, whereas in Greenland a consider- 

 able portion of it — in summer at least — is in the form 

 of rain. For reasons already stated the proportionate 

 amount carried off the Antarctic continent in the form 



