134 M1DDLEM1SS: PHYSICAL GEOLOGY OF SUB-HIMALAYA. 



tains which were crushed up during the earlier periods of the earth's 

 history. A few lines further he adds — " this great truth remains that 

 "it is impossible to point to a range of mountains which have been 

 11 built up of old denuded rocks. Old rocks certainly accompany and 

 " form part of all great mountain-ranges ; but they are only discover- 

 14 able through the removal by denudation of the enormous masses of 

 " more modern sediment with which they were originally covered. • • 

 11 . . . If we could point to one example where a mountain-range had 

 "been built up solely of old rocks that had long suffered denudation, 

 " and remained at their upheaval uncovered by newer sediment, the 

 u significance of this association of great sedimentary deposits with 

 " mountain-building would be considerably weakened." 1 



Among particular examples in illustration of the above principle 

 he says, referring to India, that the "Tertiary [system] alone, 

 " measuring 30,000 ft., has been upheaved and carved by denudation 

 " into the greatest mountain system of the globe— the Himalaya." 1 



If it be borne in mind that the principle and the supposed facts 

 alluded to here by the author form an important part of his reasoning 

 throughout the whole of his work, it will be seen how necessary it is 

 that there should be no doubt whatever of the validity of either the 

 principle underlying his argument, or of the facts that he brings 

 forward in support of it. 



Now, with regard to the greatest mountain-ranges being, geolo- 

 gically speaking, comparatively modern ; there is one consideration 

 which the author does not seem to have taken any account of, namely, 

 that to begin with a mountain-range must grow ; and that we should 

 therefore expect to find some mountain-ranges, not yet completed, 

 which would be still more modern and of very low elevation. It has 

 been pointed out by Prof. Judd that the life history of crystals in 

 many respects bears a great resemblance to the life-history of ani- 

 mals and plants : they have their time of birth, of growth to maturity, 

 and their ultimate decay and disintegration, And, without adopting 



1 Page 30. 



2 Page 73. 



( 192. ) 



