38 GLACIERS 



river ! At Geneva it stood as a solid, continuous sheet 

 more than 3000 ft. over the level of the present city and 

 lake ; and it spread out as an immense covering of solid 

 ice right away to the Jura Mountains beyond Neuchatel 

 and its lake, its surface there being 3000 ft. above the 

 present level of the lake ! A vast sea of ice in fact 

 covered the whole country, with the exception of the high 

 mountain-tops, from Lyons to Basle and along the Rhine- 

 land to Coblenz in one direction, and across Bavaria to 

 beyond Munich and Salzburg ! Whilst this was the con- 

 dition of Switzerland more northern regions were also 

 completely involved in an ice-covering. Glaciers existed 

 in Wales and Scotland, as proved by the moraines still 

 left there, the erratic blocks, and the ice-polished and 

 scratched rocks of the mountain valleys. The whole 

 Scandinavian peninsula was overwhelmed by a vast 

 glacier. The ice from the Norwegian glaciers extended to 

 our Eastern shores, and immense deposits of irregular ice- 

 borne fragments were accumulated there, and again and 

 again torn up and redeposited by the water and by float- 

 ing ice (the " drift " and the " boulder clay " of East 

 Anglia). The whole of the northern half of the temperate 

 zone was thus glaciated or ice-ridden. This astounding 

 and terrible state of things is what is referred to as " the 

 glacial period." 



The inquiry as to what were the causes of this extremely 

 different condition of regions of the earth, now so fertile 

 and richly inhabited, is a pressing one. We must be 

 anxious to know how it came about and whether it is 

 likely to come again. One result of the great amount of 

 study given to the subject during late years is the discovery 

 that there has not been one glacial period but at least 

 four, separated from one another by long warm periods 

 in which the ice retreated to something like its present 

 limitations and then again overwhelmed the land. And 



