GEOLOGY OF CENTRAL INDLV. 



65 



to pass into an imperfect variety of granitic rock. In this the quartz is 

 associated with a considerable proportion of felspar, generally of a red- 

 dish color — an instance of this kind was alluded to in page 38, and I shall 

 have occasion to describe in my next a series of rocks of this kind, 

 which occur in the boundary ranges of the valley. They are composed 

 of reddish colored felspar and quartz,— the felspar having a tendency to 

 be decomposed and crumble down on exposure. They are sometimes 

 fine grained, but more frequently intermediate betwixt fine and large 

 grained — they have, generally speaking, a porphyritic structure, and pass 

 insensibly into the quartz rocks. 



It is not my object in this sketch to trace the different rock forma- 

 tions throughout their whole extent, or to define correctly their limits. 

 I merely wish to give a general account of their structure and mode of 

 occurrence, and as opportunities occur, hereafter to give a more detailed 

 account of individual portions of this extensive tract. To trace correctly 

 the different quartz rock formations, would be a work of great difficulty. 

 They occur very extensively distributed and associated with all kinds of 

 rock. I may remark, however, in a general way, that a belt of quartz, 

 exhibiting, in many situations, craggy and precipitous hills, seems to 

 skirt this great primitive district through a large extent of country, 

 and to separate it from the newer rocks described at the commence- 

 ment of this paper. Captain Stewart's section exhibits it interposed 

 between the sandstones and the granitic rocks on the route from Moiu 

 to Baroda,— west of the sandstones near Cliitor I have also seen it, 

 and north of this last mentioned city it still makes its appearance. 

 It is probably a continuation of a similar formation which occurs in 

 the neighbourhood of Sdhar, forty miles from Biann, in the Bharutpur 

 district, which extends to the south and north of the former place, and 

 which is bounded to the east by the rocks described in a former paper as 



. s 



