Chap. IV. 1.] metamorpiiic rocks. 49 



character of the rock is not so apparent, the felspar having become 



segregated, as it were, into bodies of an almond-shape, which are arranged 



closely and sinuously together in lines parallel to the foliation. Many 



of these segregated portions are binary compounds of quartz and felspar. 



Such are some of the more marked varieties of the gneissose rocks 



in the series. But a very peculiar form of altered rock, which is quite 



irresjpective of any general variety in the series, occurs in the Ahtoor 



division of the Salem district, to an extent suffi- 

 Trap-shotten gneiss. 



ciently great to warrant our noticing- it specially. 



This rock is gneiss of various kinds, altered, through more or less immediate 

 contact with trappean rocks, to such an extent and in such a manner 

 that it is, as it were, very largely impregnated or shot with strings of 

 dark-green or bluish-black compact trap, and on first seeing it, the term 

 trap-shotten gneiss immediately occurred as a very appropriate one. 

 Where this rock occurs, the foliation of the gneissose rocks is very distinct, 

 having generally an east by north and west by south direction, while 

 numerous trap-dykes traverse the rocks with a north by east and south 

 by west direction, (or generally in the north and south system of jointing,) 

 thus crossing the lines of foliation obliquely at an angle of about 65°. 

 The gneissose rocks have, however, been so thoroughly altered and impreg- 

 nated with trap in this general north and south line, that long bands of 

 this trap-shotten gneiss stand out boldly from the main mass of the series, 

 and now look like (and have the same effect in giving character to the features 

 of the couifctry as) great dykes of some rock quite distinct from that 

 which is adjacent. This is especially seen in a ridge of hills which have 

 a north-north-east and south-south-west direction, to the south-east of 

 Ahtoor, in which ridge the Munjinny and Sharooye hills are both trigono- 

 metrical survey stations. These long bands of altered gneiss, together with 

 trap-dykes, appear to form the back bone, as it were, of the ridge. A 

 band of this altered rock is well seen in a gorge due west of Gungawlly, 

 where an attempt has been made to form a large tank-bund. Indeed, 



G ( -^n ) 



