10 COSMOS. 



organic life in a zone that is nearly 3000 feet lower than 

 that to which it attains in the equinoctial region of the Cor- 

 dilleras. 



But the countries bordering on the equator possess another 



pp. 281-326.) My opinion on the difference of height of the snow-line on 

 the two sides of the Himalaya has the high authority of Colebrooke in its 

 favour. He wrote to me in June, 1824, as follows : " I also find, from 

 the data in my possession, that the elevation of the line of perpetual snow 

 is 13,000 feet. On the southern declivity, and at lat. 31, Webb's mea- 

 surements give me 13,500 feet, consequently 500 feet more than the 

 height deduced from Captain Hogdson's observations. Gerard's mea- 

 surements fully confirm your opinion that the line of snow is higher on 

 the northern than on the southern side " It was not until the present 

 year (1840) that we obtained the complete and collected journal of the 

 brothers Gerard, published under the supervision of Mr. Lloyd. (Narra- 

 tive of a Journey from Cawnpoor to the Boorendo Pass, in the Himalaya, 

 by Captain Alexander Gerard and John Gerard, edited by George Lloyd, 

 vol. i. pp. 291, 311, 320, 327, and 341.) Many interesting details re- 

 garding some localities may be found in the narrative of A visit to the 

 Shatool,for the purpose of determining the line of perpetual snow on the 

 southern face of the Himalaya, in August, 1822. Unfortunately, how- 

 ever, these travellers always confound the elevation at which sporadic 

 snow falls, with the maximum of the height that the snow-line attains on 

 the Thibetian plateau. Captain Gerard distinguishes between the summits 

 that rise in the middle of the plateau, where he states the elevation of the 

 snow-line to be between 18,000 and 19,000 feet, and the northern slopes 

 of the chain of the Himalaya, which border on the defile of the Sutledge, 

 and can radiate but little heat, owing to the deep ravines with which they 

 are intersected. The elevation of the village of Tangno is given at only 9300 

 feet, while that of the plateau surrounding the sacred lake of Manasa is 17, 000 

 feet. Captain Gerard finds the snow-line 500 feet lower on the northern 

 slopes, where the chain of the Himalaya is broken through, than towards 

 the southern declivities facing Hindostan, and he there estimates the line of 

 perpetual snow at 15,000 feet. The most striking differences are presented 

 between the vegetation on the Thibetian plateau, and that characteristic 

 of the southern slopes of the Himalaya. On the latter the cultivation 

 of grain is arrested at 9974 feet, and even there the corn has often to 

 be cut when the blades are still green. The extreme limit of forests 

 of tall oaks and deodars is 11,960 feet; that of dwarf birches 12,983 

 feet. On the plains, Captain Gerard found pastures up to the 

 height of 17,000 feet; the cereals will grow at 14,100 feet, or even at 

 18,540 feet ; birches with tall stems at 14,100 feet, and copse or brush- 

 wood applicable for fuel is found at an elevation of upwards of 17,000 

 feet, that is to say, 1280 feet above the lower limits of the snow-line at the 

 equator, in the province of Quito. It is very desirable that the mean 

 elevation of the Thibetian plateau, which I have estimated at only about 

 8200 feet between the Himalaya and the Kouen-Lun, and the difference in 



