403 



ences do not furnish the relations of the mean 

 height of the Himalaya, the Andes, the Alps, 

 and the Pyrenees, that is, the height of the back 

 of the mountains, on which arise the peaks, 

 needles, pyramids, or rounded domes. It is 

 that part of the back where the passages are 

 made, that furnishes a precise measure of the 

 minimum of the height attained by the great 

 chains. In comparing the whole of my mea- 

 sures with those of Moorcroft, Webb and 

 Hodgson, Saussure and Ramond, I estimate the 

 mean height of the top of the Himalaya, be- 

 tween the meridians of 75° and 77°, at 2450 

 toises ; the Andes * (at Peru, Quito, and New 



Mont Perdu 40 toises. (Vidal and Reboul, in the Annates 

 de chimie, torn, v, p. 234, and in the Journal de physique, 

 1822, Dec. p. 418, Charpentier, Essai sur la constit. geognost. 

 des Pyrenees, p. 823, 539.) 



* In the passage of Quindiu, between the valley of Mag- 

 dalena and that of the Rio Cauca, I found the culminant point 

 (la Garita del Parama), at 1798 toises of absolute height ; it 

 is however, regarded as one the least elevated. The passages 

 of the Andes of Guanacas, Guamani, and Micuipampa are 

 respectively 2300, 1713, and 1817 toises above the surface of 

 the ocean. Even in 33° south latitude, the road which crosses 

 the Andes between Mendoza and Valparaiso is 1987 toises 

 high. See my A.stron. Obs. Vol. i, p. 312, 314, and 316, 

 Caldas, Semanario de Santa Fe de Bogota, torn, i, p. 8 and 

 38. I do not mention the Col de l'Assuay, where I passed, 

 near la Ladera de Cadlud, on a ridge 2428 toises high, be- 

 cause it is a passage on a transversal ridge that joins two pa- 

 rallel chains. 



