204 GLACIAL HISTORY. 



Organic nature will be found to confirm the inferences de- 

 rived from the rocks as to the aspect of Switzerland during the 

 drift period. If the same phenomena which are now witnessed 

 in high northern latitudes, as well as in the Alps, formerly oc- 

 curred in Switzerland, the traces of them will remain in the 

 flora and fauna of that country. 



At the time of the greatest extension of the glaciers, when an 

 icy mantle some thousands of feet in thickness was spread over 

 the low Swiss grounds, organic life must have been almost 

 entirely banished. Yet even then some islets stood out of the 

 sea of ice, such as the land between the Napf and the Aar ; and 

 in the highest regions rocky peaks projected above the ice which 

 is proved by the numerous erratic blocks which constituted a 

 part of the moraine. 



Organic life in plants * and insects is met with at the present 

 day on the highest summits of the Alps, and on the remotest 

 islets and moraines of the granular snow, to an elevation of 

 11,000 feet; and, in like manner, during the Glacial epoch some 

 life was preserved. In connexion with this question it must be 

 remembered that Prof. Heer is acquainted with 111 species of 

 Phanerogamous plants from Spitzbergen, and with more than 

 320 from Greenland, although boundless glaciers cover these 

 countries and descend even to the sea. When, in Switzerland, 

 the glaciers melted and left the plains no longer covered with 

 ice, vegetation pushed its way over the low grounds and clothed 

 afresh the desert country. The plants of the lignite beds in- 

 form us that the flora which then penetrated into Switzerland 

 was the same as the vegetable kingdom now flourishing there, as 

 well as in other parts of Central Europe and of the temperate 

 portions of Asia, but that to the modern flora one or two 

 mountain-plants (Pinusmontana and Acer pseudoplatanus) should 

 be added. 



When the glaciers again advanced from the Alps and extended 

 into the plain, the change of climate essentially altered the flora. 

 At the time when the numerous terminal moraines were depo- 

 sited, Alpine plants were no doubt conveyed by them, and by 



* In the Grisons Prof. Heer has collected 106 species of flowering plants 

 in the highest region, between 8500 and 11,000 feet above the sea-level. 



