Col. McMahon — Granite of the Himalayas. 213 



not, produced by pressure-metamorphism, a point not touched on in 

 my published papers. 



As the Himalayas cover a large area, I shall limit my remarks 

 almost exclusively to the rocks in the neighbourhood of Dalhousie, 

 a sanitarium in the mountains nearly due east from Lahore, the capital 

 of the Panjab. Want of space obliges me, however, to make my 

 observations on the stratigraphy extremely brief. Any one requiring 

 more detailed information will be able to find it in the volumes of 

 the Records of the Geological Survey of India. 



In the neighbourhood of Dalhousie the gneissose-granite appears 

 in two bands striking in a north-westerly direction. The inner 

 band at Dalhousie itself is six miles and a half in thickness ; 

 further to the south-east the thickness increases to eleven miles, 

 and this broad belt extends for some hundreds of miles in a south- 

 easterly direction. In its north-westerly extension from Dalhousie 

 the band suddenly contracts to a width of two hundred and fifty 

 yards : but twenty-one miles further on it expands again as abruptly 

 as it contracted. 



This outcrop is in contact along both margins with Silurian rocks ; 

 those along its eastern margin being older, and those along its 

 western margin younger Silurians. The interpretation which I 

 have put on this section is that the granite has risen through the 

 axis of a flexure that resulted in an overfold fault. ^ 



The outer band of gneissose-granite, roughly speaking, runs a 

 course parallel to the western margin of the inner band, being 

 divided from it by a broad belt of Silurian beds. To the south of 

 Dalhousie it dies out altogether. Its general width is between four 

 hundred and five hundred feet ; but to the north-west of Dalhousie 

 it widens out to several thousands of feet in thickness. Along its 

 eastern margin it is in contact with Lower Silurian, or Cambrian, 

 mica-schists (no fossils have ever been found in them, so their precise 

 age cannot be determined) ; and along its western margin with 

 limestone and slaty beds of Carboniferous age. The latter are not 

 greatly altered rocks ; the limestones are never more than sub- 

 crystalline ; and though the slaty rocks have often a thin micaceous 

 glaze, they are sometimes shaly in appearance ; and are frequently 

 so highly charged with carbonaceous material, and so coal-black 

 in colour, that they have from time to time, in various parts of the 

 Himalayas, raised fallacious hopes of finding coal in the minds of 

 non -geologists. 



The strike of the Silurian and Carboniferous beds conforms to 

 that of the granite, following all its curves. The beds in contact 

 usually dip into the granite ; but occasionally dip away from it. 



The Gneissose-Granite. 



The gneissose-granite is almost always decidedly porphyritic, 

 though it occasionally passes into a fine-grained non-porphyritic rock. 

 The matrix is usually a granite of moderately large grains (it is 



1 A geological map of the Dalhousie area and diagrammatic sections explaining it 

 mU be found at page 110, vol. xviii. Records Geol. Survey of India. 



