CHAP. VIII 



THE CAUSES OF GLACIAL EPOCHS 



139 



Conditions Determining the Presence or Absence of Perpet- 

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

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

 condenser of that moisture into snow, are the prime essen- 

 tials 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 perennial 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 glacia- 

 tion, 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 with North-eastern Canada 

 seems to have been the source of much of the glaciation 

 of that continent.^ 



^ "The general absence of recent marks of glacial action in Eastern 

 Europe is well known ; and the series of changes which have been so well 

 traced and described by Prof. Szabo as occurring in those districts seems to 

 leave no room for those periodical extensions of ' ice-caps ' with which 

 some authors in this country have amused themselves and their readers. 

 Mr. Campbell, whose ability to recognise the physical evidence of glaciers 

 will scarcely be questioned, finds quite the same absence of the proof of 

 extensive ice-action in North America, westward of the meridian of 

 Chicago." (Prof. J. W. Judd in Geol. Hag. 1876, p. 535.) 



The same author notes the diminution of marks of ice-action on going 

 eastward in the Alps ; and the Altai Mountains far in Central Asia show 



