134 



ISLAND LIFE. 



[part I. 



were it a northerly extension of a lofty Antarctic continent ? 

 We may be quite snre that glaciation would then be far more 

 severe, and that an ice-sheet corresponding to that of Greenland 

 might extend to beyond the parallel of 50° S. Lat. Even 

 this is probably too low an estimate, for on the west coast of 

 New Zealand in S. Lat. 43° 35' a glacier even now descends to 

 within 705 feet of the sea-level ; and if those islands were 

 the northern extension of an Antarctic continent, we may 

 be pretty sure that they would be nearly in the ice-covered 

 condition of Greenland, although situated in the latitude of 

 Marseilles. 



Conditions determining the presence or absence of perpetual 

 Snow. — It is clear, then, that the vicinity of a sea or ocean to 

 supply moisture, together with high land to serve as a con- 

 denser of that moisture into snow, are the prime essentials of 

 a great accumulation of ice ; and it is fully in accordance with 

 this view that we find the most undoubted signs of extensive 

 glaciation in the west of Europe and the east of North America, 

 both washed by the Atlantic and both having abundance of high 

 land to condense the moisture which it supplies. Without these 

 conditions cold alone, however great, can produce no glacial 

 epoch. This is strikingly shown by the fact, that in the very 

 coldest portions of the two northern continents — Eastern Siberia 

 and the north-western shores of Hudson's Bay — there is no per- 

 ennial covering of snow or ice whatever. No less remarkable 

 is the coincidence of the districts of greatest glaciation with 

 those of greatest rainfall at the present time. Looking at a 

 rain-map of the British Isles, we see that the greatest area of 

 excessive rainfall is the Highlands of Scotland, then follows 

 the west of Ireland, Wales, and the north of England ; and 

 these were glaciated pretty nearly in proportion to the area of 

 country over which there is an abundant supply of moisture. 

 So in Europe, the Alps and the Scandinavian mountains have 

 excessive rainfall, and have been areas of excessive glaciation, 

 while the Ural and Caucasian mountains, with less rain, never 

 seem to have been proportionally glaciated. In North America 

 the eastern coast has an abundant rainfall, and New England 



