212 GLACIAL HISTORY. 



lay as (although these are situated so far south), plants are found 

 belonging to the northern flora. These are, for the most part, 

 species which also occur in the Alps ; so that the Swiss mountains 

 have a number of plants in common with American and Asiatic 

 ranges, and these plants have issued from the north as from a 

 common source. It is therefore very probable that, during the 

 Glacial epoch, the Scandinavian flora was spread over a great 

 part of Germany and also dispersed in Switzerland. As only 

 the principal glacier of Eastern Switzerland (the Rhine glacier) 

 extended as far as Germany, while the other Swiss glaciers 

 were bounded by the chain of the Jura, greater opportunities 

 for the immigration of the northern flora were presented at 

 the eastern side, which may explain the remarkable fact that 

 Eastern Switzerland, and especially the Canton of the Orisons, 

 has a number of rare plants and animals* in common with high 

 northern latitudes, which are wanting to the rest of Switzerland. 

 Hence a considerable portion of the Swiss Alpine flora probably 

 came from the north, and reached Switzerland during the Gla- 

 cial epoch. Afterwards, as the climate became warmer and 

 drier, they found in the Alps suitable places for their develop- 

 ment, where they have maintained their position, as in- the 

 north, down to the present day, whilst they have disappeared 

 from the plain, except in the colonies of northern plants, and 

 are now almost entirely wanting in the whole of that wide region 

 that lies between the Alps and Scandinavia. 



[Sir Charles Lyell mentions, in his ' Student's Elements of 

 Geology/ p. 144, that the boulder formation had been termed 

 ({ Diluvium," but that geologists observed it to be characteristic 

 of high latitudes, and that the great development of the boulder 

 formation with large erratics so far south as the Alps, favoured 

 the hypothesis that there was some intimate connexion between 

 it and accumulations of snow and icefj 



Remains of Mollusca and Mammalia have been found in the 

 deposits of the drift. It has been noticed (p. 189) that 

 the glacier- streams contain much mud and sand produced 



* Carex Vahlii, Juncus castaneus, J. styyius, Trientalis europcea, Thalictrum 

 alpinum ; Leiochiton arcticum, Cymindis angularis, Attains Cardiacce, Linn., 

 sp., Biston lapponarius, Boisd., Chelonia Quc.melii. 



t Editor. 



