312 C. A. McMahon — Gneissose- Granite of the Himalayas. 



plutonic conditions, but indicate a more rapid cooling than is con- 

 sistent with those conditions. These structures, it seems to me, 

 would not now be visible if the rock had taken long ages to cool 

 at a great depth below the surface, with all the rocks later than those 

 of Carboniferous age piled up on the top of it. 



I will now pass on to offer a few words of explanation regarding 

 the following observation made by Mr. Middlemiss in the Memoir 

 under consideration. He writes at p. 274 as follows : " Probably 

 the first idea of many people after superficially studying the 

 Himalaya would be to regard the great crystalline axis as having 

 been the cause of the upheaval of the mountain mass, the prime 

 mover, which bursting through the other rocks wedged them apart 

 and folded and contorted them." A footnote to this passage refers 

 to some remarks of mine in my Presidential Address already 

 alluded to. 



This reference to ray views appears to imply a misunderstanding 

 of their scope. I said that " The contortion, compression, and 

 upheaval which marked the earth movements that set in at the 

 close of the Eocene period, were connected with the intrusion of 

 the gneissose-granite." I said "connected with" advisedly. I did 

 not assert that the granite was the sole cause of the contortion, com- 

 pression, and upheaval, and I did not assert that the " earth move- 

 ments " were caused by the rise of the granite. I did not for 

 a moment lose sight of the fact that tangential pressure (apart 

 from the rise of the granite) was a potent factor to be taken into 

 consideration ; and I spoke (Proc. Geol. Assoc, xiv, p. 289) of" the 

 granite being "forced, under conditions of great lateral and upward 

 pressure, between the jaws of faults." I remarked that the granite 

 " runs, on the whole, with the strike of the sedimentary rocks, and 

 its outcrop seems to be directly connected with the wrinkling 

 of the strata and the formation of overthrust faults " (loc. cit., 

 p. 93); and again, that the granite was "implicated in the folding 

 in a way to suggest intrusion along overthrust faults." These 

 overthrust faults were, I presumed, caused by tangential pressure. 

 I wished to point out that the intrusion of beds of granite — in some 

 cases twelve miles thick, along the whole line of the Himalayas — 

 must have contributed greatly to the compression of the strata. 

 I thought that it would be sufficiently obvious that the compression 

 due to the intrusion of the granite followed, and did not precede tbe 

 formation of the faults, fissures, and planes of weakness, which 

 enabled the granite to penetrate the sedimentary strata. When 

 I spoke of intrusion along overthrust faults I thought the reader 

 would understand that the faults must be formed before the granite 

 was forced into them ; and consequently I did not think it necessary 

 to explain that the granite was not the cause of the faulting. 



As regards the question of elevation, Mr. Middlemiss remarks 

 at p. 273 : — " So far as Hazara and such parts of the higher and 

 lower Himalaya that I have seen are concerned, the rock, if 

 originally a gneiss, must have been so heated as to get at least 

 into a plastic state in which it was capable of considerable movement 



