48 GEOLOGY OF TRIcniKOrOLY^ &C. [ClIAP. IV. 1. 



stitute a regular hornblende-rock, in which any trace of foliation is gen- 

 erally most obscure, rendering the rock very like many igneous rocks. 

 The bedded or banded structure of the mass, however, alternating as it 

 does with the same structure in other varieties of the metamorphic series, 

 readily determines the true nature of the rock. 



Talcose schists occur in the Salem-Ahtoor valley, on the southern 



flank of the Godumullay, whence they trend con- 



Talcose schists. . , j -ji • • •jj.i, xi, i. 



tmuously and with increasing width up the east 



side of the TainandamuUay hill, finally crossing the Punniar at Munnikul 



hill. They underlie the great Godumullay iron beds. Course quai-tzo- 



hornblendic schists, also containing talc, occur north of Huroor in the 



Baramahal. 



Chlorite-schists occur over much of the country between Tathengara- 



paittai in the extreme south-east corner of the 



Salem district, and Cunnanoor, in the Trichinopoly 



district ; and among these chloritic schists, beds containing garnet in 



abundance occur at Tholya-nuttum and Poodooputty, in the Moosery 



taluq, in Trichinopoly district. 



Associated with the chloritic rocks in the same district is a consi- 

 derable development of a quasi-porphyritic gneiss, 

 (4uasi-poipiyr i ^ ■ higj^ly quartzose, with imperfectly formed crystals 

 of drab, pink, or purplish felspar; these imperfect crytals dissemi- 

 nated in the general matrix, and frequently causing the mass at first 

 sight to have much the appearance of a conglomerate ; the foliation, how- 

 ever, is almost invariably well marked. A similar rock occurs at Caudpu- 

 toor, a few miles north-east of the junction of the Ambrawutty with the 

 Cauvery, and also at different localities between this and the places noted 

 above, indicating the extension of beds of this variety across the country. 



South of the Cauvery, gneiss of a similar character was observed (but 

 not to so great an extent) at Munnicondum-choultry, 8 miles south- 

 south-west of Trichinopoly, and again further to the west at Ramchander 

 TrimuUay. At the former of these places, the irregularly porphyritic 

 ( 270 ) 



