136 ISLiND LIFE 



only where there are lofty moimtains or plateaus — as in 

 Greenland, Spitzbergen, and Grmnell's Land — that glaciers, 

 accompanied by perpetual snow, cover the country, and de- 

 scend in places to the level of the sea. In the Antarctic 

 regions there are extensive highlands and lofty mountains, 

 and these are everywhere exposed to the influence of moist 

 sea-air ; and it is here, accordingly, that Ave find the nearest 

 approach to a true ice-cap covering the whole circum- 

 ference of the Antarctic continent, and forming a girdle of 

 ice-cliffs which almost everywhere descend to the sea. 

 Such Antarctic islands as South Georgia, South Shetland, 

 and Heard Island, are often said to have perpetual snow at 

 sea-level ; but they are all very mountainous, and send down 

 glaciers into the sea, and as they are exposed to moist sea- 

 air on every side, the precipitation, almost all of which 

 takes the form of snow even in summer, is of course 

 unusually large.^ 



That high land in an area of great precipitation is the 

 necessary condition of glaciation, is well shown by the 

 general state of the tw^o polar areas at the present time. 

 The northern part of the north temperate zone is almost 

 all land, mostly low but with elevated borders ; while the 

 polar area is, with the exception of Greenland and a few 

 other considerable islands, almost all water. In the 

 southern hemisphere the temperate zone is almost all 

 water, while the polar area is almost all land, or is at least 

 inclosed by a ring of high and mountainous land. The 

 result is that in the north the polar area is free from any 

 accumulation of permanent ice (except on the highlands 

 of Greenland and Grinnell's Land), while in the south a 

 complete barrier of ice of enormous thickness appears to 

 surround the pole. Dr. Croll shows, from the measured 

 height of numerous Antarctic icebergs (often miles in 

 length) that the ice-sheet from which they are the broken 

 outer fraOTnents must be from a mile to a mile and a half 



o 



some of them rise to a height of more than 2,000 feet." It must be 

 remembered that the north coast of Eastern Siberia is in the area of 

 supposed greatest winter cold on the globe. 



^ Dr. Croll objects to this argument on the ground that Greenland and 

 the Antarctic continent are probably lowlands or groups of islands. 

 {Climate and Cosmology, Chap. Y.) 



