532 R. D. Oldham, — Origin of the Himalayas. 



II. — The recent Discussion on the Origin of the Himalayas. 



By E. D. Oldham, F.E.S., V.P.G.S., etc. 



rilHE discussion on the oiigin of the Himalayas, started by Sir T. H. 

 X Holland's review' of Colonel Burrard's memoir, appears to have 

 been led, by the concluding sentence of that review, into an un- 

 profitable channel ; for alike in the review and in the succeeding 

 articles by Mr. Fisher^ and Colonel Burrard^ it seems to have been 

 accepted that only two theories are applicable, firstly, Mr. Fisher's 

 discussion of the theory of the disturbed tract contained in chapter x 

 of the first and chapter xiii of the second edition of his Physics of the 

 Earth's Crust, and, secondly, that developed by Colonel Biirrard. 

 Further, it is assumed that the former is dependent on the hypothesis 

 of a fluid earth and the latter such as should follow from the 

 hypothesis of a solid, highly heated, and cooling globe ; the connexion, 

 in either case, being so close that the acceptance of one or other 

 hypothesis, of the constitution of the earth, necessitates the acceptance 

 of one and the rejection of the other of the theories of the origin of 

 the Himalayas. This, however, is not the case ; Mr. Fisher's 

 treatment of the disturbed tract, though originally a development 

 of his theory of a fluid earth, and quite consistent with it, is equally 

 consistent with the hypothesis of a solid earth, for it is hardly 

 conceivable that the substance of the most solid of globes would not 

 yield and flow under stresses of the magnitude and duration of those 

 involved by the support of a mountain I'ange such as the Himalayas, 

 and, once such a flow commenced, there would be developed a system 

 of quasi-hydrostatic support, and an isostasy caused by a species of 

 flotation, which is all that is demanded by the general theory or by 

 the adaptation to the particular case of the Himalayas contained in 

 chapter xviii of the second edition of the Mmmal of the Geology of 

 India. I, at least, have never regarded this as having any but a very 

 remote bearing on the hypothesis of a solid or fluid condition of the 

 interior of the earth. 



On the other hand, Colonel Burrard's explanation, so far from 

 being in accord with the hypothesis of a solid, cooling, earth, is in 

 reality inconsistent with it, and his view, that, in such a globe, rifts 

 would open by contraction from the surface downwards, is the reverse 

 of what would actually take place. The conditions existing in 

 a partially cooled solid globe are well understood ; I believe they 

 were first pointed out by Mr. Mellard Reade in 1876, but once 

 indicated thej^ became a truism, and ma^^ be very briefly explained. 

 In such a globe there would be, on the outer surface, a crust, which 

 has fully cooled and is incapable of further contraction, and in the 

 centre a heated core, to which cooling has not penetrated ; between 

 the two lies a belt of material which is gradually losing heat and 

 contracting in bulk. At the inner limit the contraction of this layer 



' Sir T. H. Holland, " Origin of Himalayan Folding " : Geol. Mag., 1913, 

 p. 167. 



2 Eev. 0. Fisher, " Eigidity of the Earth," Geol. Mag., 1913, p. 250; 

 " Origin of Mountains," Geol. Mag., 1913, p. 434. 



* Colonel S. G. Burrard, " Origin of Mountains " : Geol. Mag., 1913, p. 385. 



