J 62 SUB-HIMALAYAN ROCKS OF N. W. INDIA. [CHAP. VI. 



These deposits are very thick in some places, nearly 3,000 feet, 

 and cover an immense area, being probably the same as have been 

 described far to the west and to the east of this region. It is principally 

 on this circumstance of uniformity and extent that Colonel Strachey 

 bases his opinion, that the deposits are of marine origin. No marine 

 remains have been found in them, but, on the contrary, they contain 

 bones of large mammalia of extinct varieties. 



Besides the more special observations that have just been enumerated, 

 there are general features upon which Colonel Strachey' s hypothesis 

 more immediately rests. The area to which he extends his generaliza- 

 tions reaches from the plains of India to those of Central Asia, and 

 longitudinally, in a north-west and south-east direction to the supposed 

 limits of the chain. On the transverse outline of this mass the Hima- 

 laya and the Kuenlun occupy the line of demarcation of the southern 

 and northern slopes, and the table land of Thibet occupies the summit 

 of the protuberance, — an arrangement with which is connected the great 

 central longitudinal, and the deep lateral, systems of drainage. Through- 

 out the whole area we may notice the mutual parallelism of the great 

 ridges and of the outer limits of the area, of the strike of the strata, 

 of the lines of igneous action, and of the distribution of the rock 

 groups. Attention is further drawn to the fact of the constancy main- 

 tained for great distances longitudinally both in geological structure and 

 in the elevation of the mountains. 



At this point of the argument the author's opinion regarding the 

 marine origin of the plains of Thibet leads him into what I cannot 

 but consider inextricable difficulties. The elevation of the Himalayan 

 mass, as we know it, and through at least 17,000 feet, is thus 

 brought within a very late period of the earth's history ; it is this 

 last great movement of Himalayan elevation that forms the principal 

 subject of Colonel Strachey's second paper. It is not the question 

 of time, against which we can raise no a priori objection, which 



