268 GENERALIZATIONS. 



sea was in connexion with the Baltic a circumstance which must 

 have lowered the temperature of the Baltic as well as of sur- 

 rounding countries. 



Professor Escher de la Linth first called attention to a second 

 cause. Every inhabitant of the Swiss mountain-regions is aware 

 that the warm south wind (known under the name of the "Fohn") 

 exerts a great influence on the melting of the snow. It probably 

 owes its existence, at least in part, to currents of hot air pro- 

 duced by the sands of the African deserts, and directed towards 

 the north. But at the drift-epoch part of the desert of Sahara 

 was submerged by the sea, as is proved by the marine animals 

 that it contains ; and this circumstance must have had an influ- 

 ence on the climate of Europe. 



Charpentier and Lyell have expressed the opinion that the 

 invasion of Switzerland by the glaciers might have been due to 

 the greater altitude of the mountains, and to the general level 

 of the country having been some thousands of feet higher than 

 at present. If the whole mass of the Alpine rocks which now 

 cover the plains of Switzerland could be replaced upon the moun- 

 tains, the sides of the peaks and ridges would be considerably 

 enlarged, and ravines and valleys would be filled up, but the 

 absolute heights of the mountains would not be much increased. 

 No evidence exists of a sinking of the whole of Switzerland since 

 the Glacial epoch. At the level of the sea the temperature was 

 lower in the drift-period than at the present day. This is proved 

 by the discovery of species belonging to the Arctic fauna in the 

 marine deposits of the drift-epoch in England, in Scandinavia, 

 and even in Sicily. In whatever manner we regard the pheno- 

 mena connected with glaciers, we find their traces not only in 

 Europe, but also in the Caucasus, the Himalayas, in the Leba- 

 non, the north of America, and even in New Zealand. 



Dr. Blandet has maintained the hypothesis of a change pro- 

 duced in the sun itself to account for the changes of temperature 

 in geological formations. He bases his theory on the ground 

 advanced by Kant and Laplace > that at its origin the system 

 consisted of an immense gaseous [revolving] mass, in which the 

 planets were successively detached by the movement which had 

 been impressed upon it. According to this hypothesis, the sun 

 had at first a much greater volume, and by degrees became 



