The Gneissose- Granite of the Himalayas. 311 



These facts are interesting as far as tbey go ; but they fall far 

 short of proving that the intrusion of the granite is Pre-Triassic, or 

 Pre-Infra-Triassic. 



As already stated (loc. cit.), Oldham has shown that the gneissose- 

 granite is intrusive in Infra-Krol rocks in the Satlej Valley, which 

 cannot be older than Carboniferous, for the Infra-Krol beds rest 

 on the Blaini group, for which a Carboniferous age has been 

 assigned (compare Mr. Middlemiss's Memoir, pp. 129, 133, 135, 

 and 206). 



Mr. Lydekker's description of the rocks in the Shigar and Braid u 

 regions ^ shows that the Trias and " gneiss " are constantly associated 

 together, and a future detailed examination of that and other 

 regions in the Himalayas, now that we know the igneous character 

 of the gneissose-granite, may show that it is intrusive in rocks 

 of later age than the Carboniferous period. As long as the granite 

 was supposed to be a gneiss — natnely, a converted sedimentary 

 rock — no one took notice of contact- metamorphism, for that was 

 supposed to be a part of the general metamorphism of which 

 a gneissic structure was the extreme expression. 



Mr. Griesbach has shown that granite traverses and alters rocks of 

 Permo-Cal'boniferous,'^ Cretaceous,^ and Eocene* ages in Afghanistan. 

 Whether these hornblendic granites (which appear to be either gneissic 

 in part, or to be associated with gneisses) are related to the gneissose- 

 granite of the Himalayas, 1 do not pretend to say ; but, at all events, 

 it is clear that the intrusion of gi^anite took place in Afghanistan, the 

 mountains of which seem genetically related to the Himalayas, down 

 to Eocene times. The evidence at present collected does not, I think, 

 require us to believe that the history of the Himalayas, especially as 

 regards the age of its granite, presents essentially different features 

 from that of the Hindu Kush. If we have Eocene granite in the 

 latter, why not in the Himalayas ? 



Even if, in the Himalayas, no outcrop of granite should hereafter 

 be found in strata of later age than Infra-Triassio or Triassic, 

 I should not hold that this fact, taken alone, proves that the age 

 of the granitic intrusion is Pre-Triassic. 1 should not expect to 

 find granite, as granite, in rocks of Miocene or Pliocene age. 

 1 should expect to find the representative of the granite in such 

 rocks less holocrystaliine in structure than a true granite and 

 more like a porphyrite, or porphyry. In my original description 

 of the Dalhousie rock 1 mentioned that in places the matrix 

 became so fine-grained that the rock assumed " the outward 

 aspect of a felspar porphyry." This aspect, and the " crj'pto- 

 crystalline " structure of the mica described in my orighial 

 papers, and in my address as President of the Geologists Association 

 (Proc. Geol. Assoc, vol. xiv, p. 245), are incompatible with the 

 supposition that the final consolidation of the rock took place under 



1 Records G.S. I., xiv (1881). 



2 Eecords G.S.I., xix, p. 241. 



3 Memoirs G.S.I., xviii, p. 348. Eecords G.S.I. , xix, pp. 64, 242; xx, pp. 22, 23. 

 * Records, xx, pp. 102, 103. 



