316 Dr T. Tliomson on the Climate and 



bounded externally, does not deviate much, if at all, from the tropical 

 type. They nowhere exceed an elevation of 4000 feet, which is not 

 sufficient in isolated ridges to bring about a sufficient change of mean 

 temperature to produce much alteration in the vegetation. They 

 are only known I believe to the westward of Nepal, and therefore, 

 in the drier parts of the region, they are generally covered with trees 

 the same as those of the forest belt, with, in addition, a good deal of 

 Pinus longifolia, a subtropical species of vine, and of a dwarf species 

 of Phoenix, almost the only palm of the western Himalaya. 



From these valleys where they exist, or from the open plains in 

 other cases, the exterior ranges of the Himalaya generally rise 

 abruptly to a height of 7000 or 8000 feet, in all parts of the chain, 

 except at the point of exit of the great rivers, where of course the 

 outline of the mountains is much modified. I shall probably better 

 explain the structure of the mass of mountains, by saying that the 

 lateral chain which separates any two adjacent river basins, generally 

 terminates abruptly towards the plains in a bold promontory 7000 

 or 8000 feet in height, from which lateral branches parallel to the 

 plains run in each direction, gradually diminishing in elevation till 

 they are terminated by the great rivers. After the first sudden 

 rise, the different ridges increase much more gradually, generally 

 running nearly level for a number of miles, and then rising abruptly 

 from 1000 to 2000 feet. 



In ascending on the Himalaya (or indeed. on any range of moun- 

 tains) from the base to the line of perpetual snow, the change of 

 vegetation is extremely gradual, and within a limited change of alti- 

 tude barely perceptible, any division into groups must therefore be in 

 a great measure arbitrary. Still some mode of subdivision is quite 

 necessary for the purpose of description, as otherwise the mind would 

 be puzzled by the multitude of facts. The less complicated, however, 

 the mode of division is, the more intelligible it will be; it appears 

 therefore quite sufficient to refer the forms of vegetation to three 

 groups, similar to the three zones interposed between the equator 

 and the pole, namely, tropical, temperate, and arctic; or to use the 

 term more commonly applied in the case of mountains, alpine vege- 

 tation. 



There is so great a diversity in the vegetation of different parts 

 of the Himalaya, that I should entirely fail, were I to attempt to give 

 any general idea of the vegetation of these different zones. I shall 

 therefore select two particular spots, and by relating in some detail 

 the gradual changes of the vegetation in each of these, I shall, I 

 hope, be able to give a good general idea of the general appearance 

 of the phenomena of vegetable life. 



The hill station of Darjiling is distant from the plains of Bengal a 

 little more than 36 miles; the road follows a ridge which ascends in the 

 first 13 miles rapidly to about 7000 feet, and then runs gradually with 

 little change of level for the remainder of the way. Throughout the 



