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On the Height of ifie Perpetual Snows on the Cordilleras of 

 Peru. 



JVl. Pentland ascertained that the lower limit of the perpetual 

 snows on the acclivities of the eastern Cordillera of Upper Peru, 

 is very rarely under 17,061 feet, while on the Andes of Quito, 

 although much nearer to the equator, this limit is only 15,749 

 feet. M. Pentland, when travelling through the pass of Al- 

 ios de Toledo, in the month of October, found that upon Incho- 

 cajo, which belongs to the western Cordillera, the inferior limit 

 of the snow was 1312 feet above the pass, or 16,831 feet above 

 the sea. 



The northern back of the Himalaya has already exhibited a 

 similar anomaly, and produced by the same cause. We allude 

 to the influence which the great table-lands ought necessarily to 

 exercise on the law of the decrease of heat in the atmosphere. 

 It is evident if this law had been found for a free atmosphere, 

 by means of aerostatic voyages, the numbers it would furnish 

 would make known very nearly the temperature of the differ- 

 ent zones of a mountain, if this mountain was isolated, shot up 

 rapidly into the air, and supported itself on a base of incon- 

 siderable extent, and at the level of the sea. The same would 

 not be the case if the mountain rested upon an elevated table- 

 land ; at an equal height the temperature would be more con- 

 siderable than in the first case- It is also through the influence 

 of the table-land on which the two Cordilleras of Peru rest, 

 that we are enabled to explain how organic life is preserved at 

 so great an elevation. In the Andes of Mexico, between 18° 

 and 19° north latitude, all vegetation ceases at a height of 1 4,075 

 feet ; while in Peru, at a greater height, in the continuation of 

 the same chain, there exists not only a numerous agricultural 

 population, but also villages and large towns. At present one 

 third of the population of the mountainous districts of Peru and 

 Bolivia, live in regions situated much above that where all ve- 

 getation ceases under the same latitudes in the northern hemi- 

 sphere. 



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