344 Lieutenant R. Strachey on the 



radiation of the sun, acts immediately so powerfully in heat- 

 ing the surface of the mountains, and thereby raising the 

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

 that the secondary eifects 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 in- 

 troduced into the eminciation of the phenomenon of the 

 greater elevation of the snow-line, at the northei'n edge of 

 the belt of perpetual snow, an idea naturally arose, that 

 it was observed only on the declivity immediately facing the 

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

 gave from Cosmos, is careful to restrict it to the peaks 

 which rise above the Tartarian plateau. But this, as may 

 have been inferred from what I have already said on the 

 state of the three ranges that are crossed in succession be- 

 tween Milam and Thibet, is quite a mistake ; the fact being 

 that the greater elevation is obseiwed on the Thibetan face in 

 common with the whole of the more northern part of the 

 chain. From the remarks before made on the state in which 

 I found the Barj-Kang pass, it will be seen that even so near 

 as it is to the southern limit of the belt of perpetual snow, 

 a perceptible increase of elevation had already taken place. 

 M. Jacquemont, as quoted by M.Humboldt, says " Les neiges 

 perpetuelles descendent plus has sur la pente meridionale de 

 THimalaya, que sur les pentes septentrionales, et leur limite 

 s'eleve constamment a mesure que Ton s'eloigne vers le nord 

 dela chaine qui bordel'Inde." {Asie Centrale, t. iii., p. 303.) 

 With the proviso that the rise here spoken of is not regular, 

 but more I'apid as we cross the first great masses of perpetual 

 snow, I entirely concur in M. Jacquemont's way of putting 

 the case. 



That the radiation from the plains of Thibet can have no- 

 thing to do with the greater height to which the snow-line 

 recedes generally iii the northern part of the Himalaya, is 

 evident, for it must be all intercepted by the outer face of 

 the chain ; and that its effects even on this outer face are of 

 a secondary order, seems to me sufficiently proved by the 

 consideration, that on the Balch range, which rises imme- 

 diately from those plains, what little snow is to be seen is 



