Moreover, on the southern declivity of the Himalaya, where the ascending
current deposits the exhalations rising from a vigorous Indian vegetation,
the region of perpetual snow begins at an elevation of 11,000 or 12,000 feet
above the level of the sea,* thus setting a limit to the development of
organic
p 31
life in a zone that is nearly 3000 feet lower than that to which it attains
in the equinoctial region of the Cordilleras.
[footnote] *On the southern declivity of the Himalaya, the limit of
perpetual snow is 12,978 feet above the level of the sea; on the northern
declivity, or, rather, on the peaks which rise above the Thibet, or
Tartarian plateau, this limit is at 16,625 feet from 30 1/2 degrees to 32
degrees of latitude, while at the equator, in the Andes of Quito, it is
15,790 feet. Such is the result I have deduced from the combination of
numerous data furnished by Webb, Gerard, Herbert, and Moorcroft. (See my
two memoirs on the mountains of India, in 1816 and 1820, in the 'Ann. de
Chimie et de Physique', t. iii., p. 303; t. xiv., p. 6, 22, 50.) The
greater elevation to which the limit of perpetual snow recedes on the
Tartarian declivity is owing to the radiation of heat from the neighboring
elevated plains, to the purity of the atmosphere, and to the infrequent
formation of snow in an air which is both very cold and very dry.
Pages:
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71