]9i Dr. Thomson 07i the Climate and Vegetation of the Himalaya. 



which separate from one another the different branches, by the union of 

 which within the mountains the great rivers are formed. 



The elevation of the centi'al axis of the Himalaj'a is probably at a 

 mean about 18,000 or 20,000 feet; it is nearly uniform at about these 

 elevations throughout a great part of the chain, but gradually diminishes 

 toward both ends. Like all mountain chains, it presents alternations of 

 high and low portions, the lower parts or passes as they are called, from 

 their affording the means of passage to travellers from one side to the 

 other, being at the upper extremities of the river basins. These passes 

 are, with a few exceptions, rarely under 17,000 or 18,000 feet. The 

 lateral chains, starting from the more elevated portions of the central 

 axis between the passes, gradually diminish in elevation as they approach 

 the plains of India, not however with any exact uniformity of progression, 

 for it is not unfrecjuent to find them rise into lofty peaks considerably 

 more elevated than any known part of the central axis. The greater 

 part of the giant peaks, which rise to an elevation of 26,000 or 28,00u 

 feet, are situated in this manner, not on the central axis, but to the south 

 of it ; it is however by no means improbable that masses of equal eleva- 

 tion not yet measured or observed may occur behind them, it being un- 

 questionable that the general elevation of the country continues to increase 

 as we advance to the north, and that we have not yet (except in one place) 

 attained to any point from which a descent is commenced towards the 

 northern plains. 



The direction of the principal lateral chains and of their included 

 valleys, is on the whole perpendicular to the main axis, but with an in- 

 clination from the centre ; those on the extreme east inclining to the 

 eastward, while those on the extreme west have a very westerly direction. 

 There are certain anomalies in the courses of the rivers, particularly at 

 the north-west extremity of the chain; which, however, maybe overlooked 

 in a view so general and cursory of these rivers, as must necessarily be 

 taken on the present occasion. The most marked of these peculiarities 

 may be observed in the course of the Sutlej, which runs for a very con- 

 siderable part of its course nearly parallel to the Indus before it turns 

 toward the plains, thus separating the western part of the Himalayan 

 chain almost from its very origin into two branches, one of which separates 

 the Sutlej from the Indus ; the other to the south of, and nearly parallel to 

 the other, divides the basin of the Sutlej|from that of the Jumna and Ganges. 



From the great depth of the valleys which separate the different moun- 

 tain chains, it but seldom happens that any road crosses from one valley 

 to another, a traveller has therefore, in general, excellent opportunities of 

 studying the direction and ramifications of the different chains, either in 

 following the course of the valleys, or by travelling along the top of the 

 ridges. In both cases he will find that his course is an undulating one, 

 each chain and each branch of a chain being a curve, which bends first to 

 one side and afterwards to the other, giving off generally a spur on the 

 convex side, while the head of a valley insinuates itself into the concavity. 



