Dr. Thomson on the Climate and Vegetation of the Himalaya. 193 



XXrV. — Sketch of the Climate and Vegetation of the Himalaya. By 

 Thomas Thomson, M.D., Assistant Surgeon in the H.E.I.C Service, 

 Bengal Establishment. 



The great range of the Himalaya, when taken in conjunction with the 

 still more elevated mountains behind, which are in nowise distinguishable 

 from it, constitutes the most stupendous mass of mountains in the world, 

 not only from containing the highest peaks, but also, and still more re- 

 markably, as presenting by far the greatest area of elevated land. 



This gigantic mountain mass lies to the north of the great plain of 

 India, from which it rises on the whole very abruptly. It has a direction 

 very nearly from east to west, its west extremity is however a little more 

 northerly than the east, the latitude rising from 26° at the east, to 33° 

 at the west extremity. 



The mountain chain to which the name of Himalaya is most properly 

 applied, may be considered as bounded at the south by the plains of 

 India, and on the north by the rivers Indus and Burrampooter, which 

 have their sources in the same spot, and run one to the east, the other 

 to the west, among lofty mountains, till they enter the Indian flat country. 

 Nearly in the centre of this chain, in the most westerly part of Nepal 

 proper, lies the point of separation between the two river great systems, 

 that of the Indus and that of the Burrampooter, constituting a north and 

 south axis, which, when better known, will probably prove to be the 

 grand axis of Asia. 



From this centre the chain of the Himalaya extends to nearly an equal 

 distance in both directions, the central axis of the chain being the line 

 of water-shed between the streams which run toward the plains of India 

 on the south, and those which flow toward the Burrampooter and Indus 

 on the north. This line of water-shed or central axis will, on inspection 

 of a map, be seen to be in general somewhat to the north of half way 

 between the two boundary lines of the chain, so that the distance from 

 the axis to the plains of India, is greater than from the same place to 

 the northern rivers. The mean width of the whole chain may be stated 

 roughly to average about 150 miles, of which 90 are to the south of the 

 line of water-shed and 60 to the north of it. 



From the central axis of the chain, lateral ranges of mountains run 

 both to the north and south, stretching in the latter direction as far as 

 the plains of India, and separated from one another by deep narrow 

 valleys, which extend far into the interior of the mass of mountains. 



The number of lateral chains of the first class which form the line of 

 division or water-shed between the basins of the great rivers on the south 

 side of the central axis of the Himalaya, is about fourteen, separating 

 from one another in a series from left to right the waters of the Jhelum, 

 the Chenab, the Bcas, the Ilavi, the Sutlej, the Jumna, the Ganges, 

 the Gogra, the Gandak, the Kosi, tlie Teesta, and the Subhansheri. 

 These great chain.s, like the central axis, throw oil lateral branches 



