318 OPERATION OF CUBftENTS. 



Jauja, and the Upper Marailon ;* but I was fortunate 

 enough to be able to determine the six other basins, or long- 

 titudinal valleys, which succeed each other, as if by steps, 

 towards the north. The bottom of the valley of Cuenca, 

 between the knots of Loxa and Assuay, is 1350 toises ; the 

 valley of Allansi and of Hambato, between the knot of the 

 Assuay and the ridge of Chisinche, 1320 toises ; the valley 

 of Quito in the eastern part, 1340 toises, and in the western 

 part, 1490 toises ; the basin of Almaguer, 1160 toises ; the 

 basin of the Eio Cauca, between the lofty plains of Cali, 

 Buga, and Cartago, 500 toises; the valley of Magdalena, first 

 between Neiva and Honda, 200 toises ; and further on, 

 between Honda and Mom pox, 100 toises of average height 

 above the level of the sea.f In this region, which has been 

 carefully measured, the different basins lower very sen- 

 sibly from the equator northward. The elevation of the 

 bottom of enclosed basins merits great attention in connec- 

 tion with the causes of the formation of the valleys. I do 

 not deny that the depressions in the plains may be some- 

 times the effect of ancient pelagic currents, or slow erosions. 

 I am inclined to believe that the transversal valleys, re- 



* I am inclined to believe that the southern part of the basin of the 

 Upper Maraiion, between Huary and Huacarachuco, exceeds 350 toises. 



f- In the region of the Andes comprehended between 4 of south 

 latitude and 2 of north, the longitudinal vallies or basins inclosed by 

 parallel chains, are regularly between 1200 and 1500 toises high ; while 

 the transversal vallies are remarkable for their depression, or rather the 

 rapid lowering of their bottom. The valley of Patias, for instance, run- 

 ning from N.E. to S.W. is only 350 toises of absolute height, even above 

 the junction of the Rio Guachion with the Quilquasi, according to the 

 barometric measures of M. Caldas ; and yet it is surrounded by the 

 highest summits, the Paramos de Puntaurcu and Mamacondy. Going 

 from the plains of Lombardy, and penetrating into the Alps of the Tyrol, 

 by a line perpendicular to the axis of the chain, we advance more than 

 20 marine leagues towards the north, yet we find the bottom of the 

 valley of the Adige and of Eysack near Botzen, to be only 182 toises of 

 absolute height, an elevation which exceeds but 117 toises that of Milan. 

 From Botzen however, to the ridge of Brenner (culminant point, 746 

 toises), is only 1 1 leagues. The Valais is a longitudinal valley ; and in a 

 barometric measurement 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 rises only to from 225 to 350 toises of absolute height ; 

 nearly the level of the plains of Switzerland, which, between the Alps and 

 the Jura, are only from 274 to 300 toises. 



