THE GNE1SSIC SERIES. 33 



of one or the other series, while to some extent my discrimination has been 

 more guided by the experience gained while working over such rocks in the 

 field. It is a well-known fact, as may be fully exemplified in the ex- 

 perience of some of my colleagues, over the Goudwana groups for in- 

 stance, that one can very often tell to which members certain very similar- 

 looking rocks belong, without being able to explain why he so recognises 

 them ; and it was thus with both Mr. Oldham and myself after some 

 time among the rocks of this field. There are certain outcrops of quartz- 

 ites which we were not able to discriminate, and which possibly never 

 can be relegated with certainty to one or other series ; but these are either 

 on or very close to my approximate boundary, and they are so small as 

 to have little or no effect on the main division. 



A very curious band of quartzose rocks, already slightly noticed, 

 The pistacite quartz- occurs just east of the boundary, among the 

 schlsts " hornblende schists, which are highly charged with 



epidote, either in a minute way so as to give them a green colour : or with 

 the mineral scattered through them in the lamination : or irregularly, like 

 the garnets in a garnetiferous schist, when also the beds sometimes 

 assume the appearance of a vesicular igneous rock, the epidote having 

 weathered out leaving small cavities. These quartzites occur as a narrow 

 band among the schistose acicular hornblende rocks and traps of the more 

 finely schistose crystallines running through Dasiir nearly to Tumoy, and 

 again — possibly by a throw — further to the eastward of the latter village 

 from Thocapalem south-eastward. This form of quartzite is often so 

 hard and compact that it looks almost like a jaspideous rock, and in my 

 notes I find it often referred to as jaspery quartzite. It occurs 

 frequently in the schistose gneisses between Yarabali and the boundary 

 at Kaluvaya, and thence southwards as far as the Kaudleru river, always 

 associated with hornblende schists and occasionally with what I cannot 

 consider as other than strong intrusive sheets of diorite ; but they are in 

 greatest force in some low ridges extending from Dasiir past Tiimo} r , 

 where also there is a great deal of extravasated trap. Again to the south 

 of Thocapalem, on the Turamulla stream about Chiuapalem and westward 

 a ( 141 ) 



