ATE it AGE OF TIIE ELEVATIONS. 291 



meridians of 75 and 77, at 2450 toises ; the Andes * (at 

 Peru, Quito, and New Grenada), at 1850 toises ; the summit 

 of the Alps and Pyrenees at 1150 toises. The difference of 

 the mean height of the Cordilleras (between 5 north and 

 2 south lat.) and the Swiss Alps, is consequently 200 toises 

 less than the difference of their loftiest summits ; and in 

 comparing the passes of the Alps, we see that their average 

 height is nearly the same, although peak Nethou is 600 

 toises lower than Mont Blanc and Mont B,osa. Between 

 the Himalayaf and the Andes, on the contrary, (considering 

 those chains in the limits which I have just indicated), the 

 difference between the mean height of the ridges and that 

 of the loftiest summits presents nearly the same proportions. 



Taking an analogous view of the groups ol mountains 

 at the east of the Andes, we find the average height of 

 the coast-chain of Venezuela to be 750 toises ; of the Sierra 

 Parime, 500 toises; of the Brazilian group, 400 toises; 

 whence it follows that the mountains of the eastern region 

 of South America, between the tropics, are, when compared 

 to the medium elevation of the Andes, in the relation of 

 one to three. 



The following is the result of some numerical statements, 

 the comparison of which affords more precise ideas on the 

 structure of mountains in general.} 



* In the passage of Quindiu, between the valley of the Magdalena and 

 that of the Rio Cauca, I fonnd the culminant point (la Garita del Parama), 

 to be 1798 toises; it is however, regarded as one of the least elevated. 

 The passages of the Andes of Guanacas, Guamani, and Micuipampa, are 

 respectively 2300, 1713, and 1817 toises above sea- level. Even in 33* 

 south latitude, the road across the Andes between Mendoza and Valpa- 

 raiso is 1987 toises high. I do not mention the Col de I'Assuay, where I 

 passed, near la Ladera de Cadlud, on a ridge 2428 toises high, because it 

 is a passage on a tranverse ridge joining two parallel chains. 



f The passes of the Himalaya that lead from Chinese Tartary into Hin- 

 dostan (Nitee-Ghaut, Bamsaru, &c.), are from 2400 to 2700 toises high. 



J The Cols or passes indicate the minimum of the height to which the 

 ridge of the mountains lowers in a particular country. Now, looking at 

 the principal passes of the Alps of Switzerland (Col Terret, 1191 toises, 

 Mont Cenig, 1060 toises; Great Saint Bernard, 1246 toises; Simplon, 

 1029 toises; and on the neck of the Pyreenees, Benasque, 1231 toises 

 Pinede, 1291 toises; Gavaraic, 1197 toises; Cavarere, 1151 toises; it 

 would be difficult to affirm that the Pyrenees are lower than the averugc 

 height of the Swiss Alps. 



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