AVERAGE or THE ELEVA*IT0y3. 
291 
nieridiana of 75° and 77°, at 2150 toises ; the Andes* (at 
Fern, 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 Eosa. Between 
the Himalayat 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 of 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 foUow's 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 
oiie to three. 
The following is the result of some numerical statements, 
the comparison of which affords more precise ideas on the 
Btructuro of mountains in general. J 
* 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 lea,st elevated. 
Thepassage.s of the Andes of Guanacas, Guamani, and Mieuii)ampa, 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’Assiniy, where I 
passed, near la Ladcrade Cadlud, on a ridge 2428 toises liigh, because it 
•s a passage on a tranverse ridge joining two parallel chains. 
t The passes of the Himalaya that lead from Chinese Tartary into Hin- 
dustan (Nitee-Ghaut, Bamsaru, &c.), are from 2400 to 2700 toises high. 
t 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 Tcrret, 1191 toises, 
Mont Cenis, 1060 toises; Great Saint Bernard, 1246 toises; !»implon, 
1029 toises; and on the neck of the Pyreenees, Benasqiie, 12SI toises 
vinede, 1291 toises; Gavarnie, 1197 toises; Cavarere, 1151 toises ; it 
Would he difficult to affirm that the Pyrenees are lower than the average 
height of the Swiss Alps. 
