SCENERY AND SUPERFICIAL ASPECTS OF THE COUNTRY. 13 



What is the relation, if any, between the geological formation of the 

 Sub-Himalayan zone and the covering of forests? This is a difficult 

 question to answer directly, because so many secondary results follow 

 on a certain rock-structure, that it is often more probable that the 

 favoured trees depend rather on these secondary results or on the 

 aspect of the hill slopes than on the primary structural causes. A 

 comparison of the stock maps (which have been kindly lent me by 

 the Forest Department) with my own geological maps, is to a 

 large extent disappointing ; the stratigraphical zones do not, at the 

 first blush, seem to show much resemblance to the different stock 

 areas. Large portions of the Pcitli dun, for instance, are composed of 

 Siwalik conglomerate, and these are covered with a growth of fine 

 young Sell. But the Chokhamb and Kotri duns, where the conglo- 

 merate is absent, have also many fine Sal forests. So that the parti- 

 cular petrological constitution of any part of the sub-Himalaya, 

 varying but slightly in its chemical elements and state of solidity 

 from its neighouring zones of tertiary age, does not seem to be a 

 very important factor in determining the nature of the stock. In some 

 measure this is what we should expect, for, as will be seen in the 

 following chapter, the several rock stages of the Sub-Himalayan 

 formations being very much alike in their general facies and in the 

 ultimate material into which they can be reduced, produce, of neces- 

 sity, a very similar soil under like conditions of drainage and aspect. 

 The following generalizations seem to hold to a certain extent; 

 though numberless modifications, dependent on those natural and 

 more superficial causes which I need not stop to mention, have great 

 prominence : — 



(1) The northern limit of the Tertiary zone is practically the 



limit of the Sal tree, and therefore of the reserved forests 

 of this region. This geological boundary is a very im- 

 portant and marked one, and seems to have a real and 

 direct effect on the prevailing forest species. 



(2) The Middle Siwalik sand-rock 1 generally forms low undulat- 



1 See Chap. Ill,— Petrology. 



( 71 ) 



