465 



this region, which has been measured with pre- 

 cision, the different basins lower from the equa- 

 tor, very sensibly towards the north. In ge- 

 neral the elevation of the bottom of the in- 

 closed basins merits great attention from those 

 who reflect on the causes of the formation of 

 the vallies. I do not deny that the depressions 

 in the plains may be sometimes the effect of 

 ancient pelagic currents, or slow erosions. I 

 am inclined to believe that the transversal val- 

 lies, resembling crevices, have been widened 

 by running waters; but these hypotheses of 

 successive erosions cannot well be applied to the 

 completely inclosed basins of Titicacaand Mexi- 

 co. These basins, as well as those of Jauja, Cuen- 

 ca, and Almaguer, which lose their waters only 

 by a lateral and narrow issue, are owing to a 

 cause more instantaneous, more closely linked 



bottom of the valley of the Adige and of Eysack near Seizes 

 to be only 1 82 toises of absolute height, an elevation which 

 exceeds but 117 toises that of Milan. (See above, Vol. iv, 

 p. 311.) Frorn Botzen however, to the ridge of Brenner 

 (culminant point of 746 toises), is only 1 L leagues. The 

 Valais is a longitudinal valley j and in a barometric measure- 

 ment which I made very recently from Paris to Naples and 

 Berlin, I was surprised to find that from Sion to Brigg, the 

 bottom of the valley only rises to from 225 to 350 toises of ab- 

 solute height 5 nearly the level of the plains of Switzerland, 

 which, between the Alps and the Jura (for instance, be- 

 tween Berne, Thoun and Fribroug), are only from 274 to 

 300 toises. 



VOL. VI. 2 1 



