VI NOTES. 



collection and combination of many data furnished by Webb, Gerard, Herbert, 

 and Moorcroft, (vide my two Memoires sur les Montagues de 1'Inde, in 

 1816 and 1820, in the Annales de Chimie et de Physique, T. iii. p. 303, and 

 T. xiv. pp. 6, 22, 50). The greater elevation to which the snow line recedei 

 on the Thibetian declivitv is the result conjointly of the radiation of heat from 

 the neighbouring: elevated plains, the serenity of the sky, and the infrequent 

 formation of snow in very cold and dry air (Huinboldt, Asie Centrale, T. iii. 

 pp. 281326). The result wliich I have given as the most probable for the 

 elevation of the snow line on the two sides of the Himalaya, had Colebrooke's 

 great authority inrits favour. He wrote to me in June, 1824 : " I also find, 

 from the materials in my possession, 13000 English feet (2033 toises) for the 

 elevation of the line of perpetual snow, on the southern declivity, under the 

 parallel of 31. Webb's measurements would give me 13500 English feet 

 (2111 toisesl, being 500 feet higher than by Captain Hodgson's observations. 

 Gerard's measurements fully confirm your statement that the snow line is 

 higher on the northern than on the southern side." It has not been until 

 the present year (1840), that we have obtained, through Mr. Lloyd, the publica- 

 tion of the collected journals of the two brothers, Gerard, (Narrative of a 

 Journey from Caunpoor to the Boorendo Pass in the Himalaya, by Captain 

 Alexander Gerard and John Gerard, edited by George Lloyd, Vol. i. pp. 291, 

 311, 820, 327, and 341). Much information respecting different localities is 

 brought together in a " Visit to Shatool, for the purpose of determining the 

 Line of Perpetual Snow on the Southern Face of the Himalaya, in August* 

 1822 ;" but, unfortunately, the travellers always confound the elevation at 

 which sporadic falls of snow take place with the highest elevation to 

 which the snow line recedes above the Thibetian plateau. Captain Gerard 

 distinguishes between the summits in the midst of the elevated plateau^ 

 where he gives the limit of perpetual snow at from 18000 to 19000 English 

 feet (2815 to 2971 toises), and that portion of the northern declivities of 

 the Himalaya chain which abut on the deep valley of the Sutlej, where the 

 plateau, being interrupted, can radiate but little heat. The elevation of the 

 village of Tangno is given at only 9300 English feet, or 1454 toises ; while 

 that assigned to the plateau round the sacred lake Manasa is 17000 English 

 feet, or 2658 toises. Where the chain of the Himalaya is broken through, 

 Captain Gerard finds the snow line on the northern declivity 500 feet lower 

 than on the side facing India, where he estimates it at 15000 English feet, 

 (2346 toises). As respects vegetation, the most striking differences are 

 presented between the Thibetian plateau and the Indian declivity of the 



