304 On the Snow-line in the Himalaya. [April* 



The height to which the snow-line has been shown to recede on the 

 southern face of the Himalaya, though considerably greater than had 

 been supposed by M. Humboldt, still does not exceed what the analogy 

 of mountains in similar latitudes in the other hemisphere might have 

 led us to expect. In the central part of Chili, in Lat. 33° S. we find 

 that the lower limit of perpetual snow is at 14,500 or 15,000 feet, while 

 in Bolivia, in Lat. 18° S. it reaches 16,000, and even on some of the 

 peaks 19,000 feet.* There is therefore no appearance of any thing 

 unusual in the general height of the snow-line, which need induce us to 

 suppose the existence of any extraordinary ascending current of heated 

 air, regarding which M. Humboldt enquires. The exceedingly high 

 temperature, surpassing that known at any other part of the earth's sur- 

 face, which the air over the plains of North-Western India acquires dur- 

 ing the summer, must of course produce a sensible effect in heating the 

 upper strata of the atmosphere. But as far as I am enabled to form an 

 opinion from the few facts that have come to my knowledge regarding 

 the temperature of the higher regions in these mountains, I think there 

 is little doubt that the same cause which produces this great tempera- 

 ture in the plain, that is, the direct radiation of the sun, acts immediately 

 so powerfully in heating the surface of the mountains, and thereby 

 raising the temperature of the air over them, and in melting the snow, 

 that the secondary effects of the heated air that rises from the plains of 

 India must be almost imperceptible. 



From the way in which the term north declivity was introduced into 

 the enunciation of the phoenomenon of the greater elevation of the 

 snow-line at the northern edge of the belt of perpetual snow, an idea 

 naturally arose that it was observed only on the declivity immediately 

 facing the plains of Tibet, and M. Humboldt, in the quotation I before 

 gave from f Cosmos,' is careful to restrict it to the peaks which rise 



appearance of the distinction it will not bear examination. The association of moun- 

 tains into chains should be based upon the physical character and affinities of the 

 mountains themselves, quite irrespective of any adventitious circumstances of snow 

 or of vegetable and animal life. Botanical or zoological regions will almost always 

 be found to follow closely the configurations of the earth's surface, on the accidents 

 of which they chiefly depend ; but to make the classification of the latter depend 

 upon the former would be a manifest absurdity, 

 * Asie Centrale, T. 3, pp. 275, 277, 329. 



