CHAP. VIII.] THE CAUSES OF GLACIAL EPOCHS. 



L31 



and covered with a rich vegetation with abundance of bright 

 flowers. The reason of this is evidently the scanty snow-fall, 

 which rendered it sometimes difficult to obtain enough to form 

 shelter-banks around the ships ; and this was north of 80° N. 

 Lat., where the sun was absent for 142 days. 



Perpetual Snoio nowhere exists on Lowlands. — It is a very 

 remarkable and most suggestive fact, that nowhere in the world 

 at the present time are there any extensive lowlands covered 

 with perpetual snow. The Tundras of Siberia and the barren 

 grounds of N. America are all clothed with some kind of summer 

 vegetation ; ^ and it is only where there are lofty mountains or 

 plateaus — as in Greenland, Spitzbergen, and Grinnell's Land — 

 that glaciers, accompanied by perpetual snow, cover the country, 

 and descend 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 we find the nearest approach to 

 a true ice-cap covering the whole circumference of the Antarctic 

 continent, and forming a girdle of ice- cliffs which almost every- 

 where 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 moun- 

 tainous, 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 neces- 

 sary condition of glaciation, is well shown by the general state 

 of the two polar areas at the present time. The northern part of 

 the north temperate zone is almost all land, mostly low but with 



1 In an account of Prof. Nordenskjold's recent expedition round the 

 northern coast of Asia, given in Nature, November 20th, 1879, we have 

 the following passage, fully supporting the statement in the text. ^ " Along 

 the whole coast, from the White Sea to Behring's Straits, no glacier was 

 seen. During autumn the Siberian coast is nearly free of ice and snow. 

 There are no mountains covered all the year round with snow, although 

 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. 



