DESCRIPTIVE GEOLOGY: CRYSTALLINE AND METAMORPHIC ZONE. 249 



Agror on the west, whilst it has as its western boundary the Indus 

 R. It is really only a small patch of country of about 64 square 

 miles, descending in steep ridges and ravines from the crest of the 

 Black Mountain ridge to the Indus. The steepness of the slopes may 

 be gathered from the fact that a descent from 8,160 ft. to 1,500 ft. 

 takes place within a horizontal distance of 2| miles. Again, the drop 

 from Makranai to the Indus is from 4,550 ft. to 1,400 ft. in one mile, 

 which gives a gradient of 3 in 5. The highest peaks on the main 

 ridge are Machai, 9,825 ft., and Akhund B3ba, 9,170 ft, which, with all 

 the higher parts of the same, are covered with dense forest of Biar, 

 Paludar, etc. The slopes nearly everywhere steepen downwards near 

 the bed of the river, a fact which, together with the large scale of this 

 profound valley, may be realised when it is remarked that during the 

 expedition the brigade taking the hill route via Tilli and Ril had to 

 plough their way through deep snow, whilst the river column marched 

 through rain and mud, the operations of the one being generally 

 completely hidden from the sight of the other. 



A word is perhaps necessary to explain why I have taken such an 

 out-of-the-way bit of country for detailed description when I might 

 have addressed myself to the more familiar and easily accessible 

 parts of the country in Hazara itself. The reason is that having 

 been deputed with the Hazara Field Force, my movements were limit- 

 ed within the area occupied by our troops ; and as no one could say 

 (when the operations began) how far afield we might or might not 

 go, we could not know that we should be confined to the aforesaid 64 

 square miles. Such, however, turning out to be the case, I could do 

 nothing but study this small area in as close detail as possible. Hence 

 it comes about that it forms one of the portions of the crystalline and 

 metamorphic zone which I have sampled and taken as typical of the 

 whole. 



The rocks exposed in the Black Mountain, and also along the 

 approaches to it up the Indus river, belong to the divisions (3), (4), 

 and (5), or the more intensely crystalline rocks, presumably repre- 

 sentatives of the Slate series on the main, and with great intrusive 



( 249 ) 



