1849.] 



exercised hy Trees on Climate. 



433 



M. de Humboldt ascertained that tlie process of desiccation was every 

 where greatly augmented by the effects of cultivation. 



Europe also possesses its lakes, and these we have still to examine 

 in relation to the subject before us. My own progress through Swit- 

 zerland was much too rapid to allow me sufficiently to attend to the 

 light these waters throw on this interesting point. My regret, how- 

 ever, is the less severe as fortunately a most illustrious observer has 

 left some valuable documents which supply new proofs of the influ- 

 ence of cultivation upon the diminution of the quantity of water in 

 the district. 



Saussure, in his first researches concerning the temperature of the 

 Swiss lakes, examined those which are placed at the foot of the low- 

 est line of the Jura range. The lake of Neufchatel is eight leagues 

 long whilst its greatest breadth does not exceed two leagues. In vi- 

 siting this lake Saussure was impressed with the conviction that its 

 limits at an early period must have been much more extensive ; for, 

 says he, the great level meadows and the swamps which terminate 

 at the south-west extremity, have undoubtedly been covered with its 

 waters. The lake of Bienne is three leagues long and one broad. 

 It is separated from that of Neufchatel by a succession of plains 

 which to all appearance were formerly under water. The lake Mo- 

 rat is also separated from Neufchatel by a level morass which no one 

 doubts was formerly submerged. Formerly then, says Saussure, the 

 three great lakes of Neufchatel, Bienne, and Morat were united in 

 one great basin. In Switzerland, then, as in America and Asia, the 

 ancient lakes which we may distinguish as the primitive ones, those 

 which occupied the lower portions of the valleys, when the country 

 was wild and uncultivated, have subsequently been separated into a 

 certain number of independent ones by the drying processes to which 

 it has been subjected. 



I shall terminate my task by availing myself in this discussion, of 

 the observations of Saussure upon the lake of Geneva. This inter- 

 esting object was, as it were, the spot from whence the celebrated 

 philosopher commenced his immense labours. No one ever studied 

 it more deeply than he did. 



Saussure admits that, at an epoch much anterior to the times of 

 history the mountains which surround the lake were buried under 

 water ; some vast catastrophe occasioned a great disruption and 



