1849.] Limits of Perpetual Snow in the Himalayas. 695 



Relative heights on extreme edges of mountain belts. — It will indeed 

 be found that in any broad mountain chain resting on a plane inclined 

 to the sea level, and running nearly east and west, the effect of latitude 

 on temperature may be discarded, and that elevation above the parti- 

 cular country, and not above the general ocean, is mainly, although not 

 solely, to be considered in determining the limits of perpetual snow on 

 the two edges of the belt. The line of snow will rise as the plane of 

 the country rises, and keep above it at a continually decreasing distance, 

 until the diminishing temperature due to increasing height causes the 

 two to coincide — a phenomenon which of course cannot occur in the 

 temperate zones, as we know of no table-land so high as to be always 

 frozen on the surface. 



Relative heights on opposite sides of the same single hill of a chain, 

 — This reasoning does not however apply to the limits of snow on the 

 northern and southern slopes of any one hill or mountain, of a broad 

 and complex chain, and as a rule, the snow will be found to lie lower 

 on the northern than on the southern face of a single peak. In such 

 an instance neither difference of latitude nor inclination of plane can 

 ordinarily have any effect, and the only element to be taken into con- 

 sideration is the direct play of the sun's rays, which in the northern 

 hemisphere have most power on a hill side looking to the south. 

 Captain Hutton, in his papers on Dr. McLelland's Journal of Natural 

 History, had such isolated hills in view when he asserted that the 

 southern limit of snow was higher than the northern one, and when 

 he sought the support of my experience on the subject, as I was then, 

 1842, moving about in Ludakh and Kunawur. 



Description of illustrative sketch. — The accompanying sketch repre- 

 sents what I believe to be the true state of the case with regard to the 

 Himalayas, whether a line be drawn north and south across them, be- 

 tween the Gogra and Ganges, or east and west in the neighbourhood of 

 Cashmlr. Towards the plains of India the limit of snow on the 

 southern sides of the extreme hills will be found at about 15,000 feet 

 above the sea, as Lieutenant Strachey shows, and on the northern face 

 of the same hill, at about 12,000 feet, a figure however which I have 

 assumed for the sake of illustration, as I know of no observations 

 directly bearing on the subject. On the Tibetan side of the chain the 

 heights will be found to be about 20,000 feet on the south, and 18,000, 



