405 



contrary, (considering- those chains in the limits 

 which 1 have just indicated,) the difference be- 

 tween the mean height of the ridges and that 

 of the loftiest summits preserves nearly the 

 same relations. In applying an analogous rea- 

 soning to those groupes of mountains which we 

 have made known, at the east of the Andes, we 

 find the mean height of the chain of the shore of 

 Venezuela to be 750 toises ; of the Sierra Pa- 

 rime, 500 toises ; of the Brazilian groupe, 400 

 toises ; whence it follows that the mountains of 

 the eastern region of South America, are, be- 

 tween the tropics, to the mean elevation of the 

 Andes, in the relation of 1 to 3. The following 

 is the result of some numerical statements, of 

 which the comparison affords more precise 

 ideas on the structure * of mountains in general. 



to give the preference to the peak Iewahir, measured by Mr, 

 Herbert. Those measures will be discussed in another place. 



* The necks or passages indicate the minimum of the height 

 to which the ridge of the mountains lowers in such or such a 

 country. Now, in casting a look on the principal passages 

 of the Alps of Switzerland, (col de Seigne, 1263 t. ; col 

 Terret, 1191 t. ; Mont-Cenis, 1060 t. ; Petit Saint-Bernard, 

 1125 t. 5 Grand Saint-Bernard, 1246 t. ; Simplon, 1029 t. ; 

 Saint-Gothard, 1065 t. ; la Fourche, 1250 t.) ; and on the 

 neck des Pyrenees (Picade, 1243 t. ; Benasque, 1231 t. ; la 

 Glere, 1196 t. ; Pinede, 1291 t. j Gavarnic, 1197 t. ; Cava- 

 rere, 1151 t. ; Tourmalet, 1126 t.) ; it would be difficult to 

 affirm that the top of the Pyrenees is lower than the mean 

 height of the Swiss Alps. (Rarnond, Voijage au Mont- Perdu, 



