1842.] of the Himmalay a Mountains. cxiii 



immediately being minutely intersected by cleavages, the effect of which 

 is to resolve them into rhombohedral fragments on the slightest im- 

 pulse being communicated. The small hill on which fort Loudon is 

 built consists of this rock, and on its summit, lay some very large 

 boulders of a very tough and hard greenstone, the removal of which 

 occasioned the Officers employed in clearing the ground, not a little 

 trouble. 



247. This rock I call greenstone, for it has not the smallest re- 

 semblance to hornblende rock in appearance. I have already mentioned 

 its frequent occurrence in tracts of argillaceous schist, and I shall 

 endeavour here to collect all the particulars I have observed with regard 

 to it. It is a composite rock, consisting of two distinct substances, the 

 one a dark olive green, the other a lighter colour, more perhaps of 

 a greenish grey. The structure is small grained granitic ; that is to say 

 the minerals are obviously distinct, while yet they are in perfect contact 

 throughout. The fracture is subconchoidal, taking its character in the 

 small from the size of grain which it discloses. It is very hard, and 

 in toughness I know not its equal. The specific gravity is upwards of 

 3.0, sometimes as high as 3.2. It is very fusible under the blow-pipe, 

 and will bear drawing out into threads similarly to glass. If there 

 be really a distinct species of felspar which has been hitherto described 

 as the compact, I should be inclined to view the lighter coloured ingre- 

 dient as an example of it. The dark one is either hornblende or 

 augite, but the grain is too small to allow of a satisfactory determina- 

 tion. 



248. This rock is not seen here in situ ; these blocks being the only 

 traces of it, but in other places, as already detailed, regular gradations 

 occur, uniting it with the most ordinary schistose rocks, very frequently 

 the transition is made through quartz rock ; altogether it is a very in- 

 teresting member of our mountain strata, and the full developement 

 of all its relations is a task the execution of which I expect will throw 

 considerable light on some interesting questions in geology. 



249. From Petorahgurh in the descent to Surjoo, argillaceous schist 

 is the prevalent rock, indeed the only one, with the exception of a few 

 beds of limestone. It is mostly of the type just described, (Art. 246), 

 but some others are also met with. In particular one, having a suite of 

 colours between olive and bright red, in hardness about equal to gypsum, 



