Chap. VI] general structure of hills. 163 



makes tlie problem a difficult one ; the difficulties are principally physical 

 and mechanical, for, these depositSj be it remembered, rest undisturbed 

 in the great valleys of Thibet. Nor again can we assign limits to 

 the powers of continental elevation, — elevation without rupture or 

 disturbance. But this is not the agency to which Colonel Strachey 

 appeals ; his theory (which is that of Mr. Hopkins) is essentially 

 one of local (as opposed to cosmical), special upheaval. This being the 

 problem, it is evident that a great part, we might almost say, all the 

 positive part, of the evidence already stated, becomes irrelevant, namely, 

 the parallelism and constancy of the granitic axis, of the observed 

 dislocations, and of the attendant trappean intrusions, of the strike of 

 the strata, and of the groups of strata, these being demonstrably 

 anterior to the upheaval under discussion only prove the coinci- 

 dence in direction of distinct acts of upheaval and leave the supposed 

 case entirely dependent upon its own independent evidence. The 

 author was perhaps aware of this irrelevancy, but he does not state it 

 with quite sufficient distinctness, nor does he keep his independent 

 evidence sufficiently separated from that of the other phenomena. He 

 gives his opinion that the granitic axis is of pre-Silurian origin, and that 

 none of the igneous rocks were "specially related to the last great 

 movement." Hence, having nothing tangible to point to, he infers that 

 the agent of elevation was probably a development of elastic vapours at 

 a great depth. In this, as in every other feature, Colonel Strachey 

 assimilates the Himalayan elevation to the theory of Mr. Hopkins, in 

 which the form of the area affected and the relations of the fissures 

 produced by upheaval were the main elements of discussion. 



Thus, finally, Colonel Strachey has to rest his theory upon a few 

 " observed facts" of very doubtful validity. These are : 



1st. The existence of longitudinal and transverse fissures. — But 

 any longitudinal fissures of which observations have been published, 

 even by the author himself, can be referred with very great probability 



