104 T^^^ Scottish Naturalist. 



This was the state of Britain during the final stage of the 

 glacial period. All Scotland, and the northern half of England, 

 were covered with a thick sheet of ice, pouring down from the 

 mountain-ranges and concealing all the low ground; from the 

 Welsh mountains another ice-sheet descended and joined the 

 northern one ; all the north as well as the centre of Ireland was 

 also covered with ice, and in the mountainous south-west portion 

 of that island were large local glaciers ; the rest of England and 

 Ireland was covered with thick snow, partially melting in summer, 

 and giving rise to great floods; certainly no animal, and probably 

 no vegetable life, existed anywhere in the whole country. 



On the continent of Europe the same arctic climate existed. 

 All the northern half was covered with an ice-sheet coming from 

 the north, and which, in addition to overrunning the land, filled 

 the bed of the German Ocean, and impinged upon the British ice- 

 sheet. Then from the mountains of central Europe, from the 

 Alps and Pyrenees, great glaciers descended, and spread for 

 hundreds of miles over the low country. Where the ice-sheet 

 did not reach, snow covered the ground in winter and heavy 

 floods inundated it in summer. No plants, no animals anywhere 

 except in the far south, and even there the climate was more of 

 an arctic or sub-arctic than of a temperate nature, as we know 

 from the remains of the plants and animals (including such species 

 as the reindeer, musk-ox, lemming, &c.). 



But at last a temperate climate began to predominate over a 

 sub-arctic one ; the ice-sheets began to melt and retreat to the 

 north or up the mountains; the snow-fall was less heavy; and the 

 plants and animals seized the ground vacated by the snow and 

 ice, and occupied the territory from which their ancestors had 

 been driven by the ice- sheet in its southward march. 



In course of time the altered condition of things would be felt 

 in Britain, but the English Channel would as yet cut it off from 

 the advancing tide of life. Still it is probable that the winds and 

 sea-currents would carry thither the spores of mosses, lichens, 

 and other cryptogamic vegetation, and perhaps even the seeds of 

 some of the higher plants, which would find suitable restirig-places 

 out of reach of the great floods which continued to sweep over 

 much of the low ground. 



Finally, after several variations in the relative heights of the 

 land or sea (the latter being at one time loo feet higher on our 

 shores than it is at present ^), tlie land rose so much that tiie bed 



^ About 80,000 years ago. 



