Chap. IV. 1.] metamorphic eooks. 77 



nation that seems to offer itself is that the area over which these beds are 

 found was subjected to an amount of metamorphism greater than that 

 which has affected the adjoining portions^ probably in consequence of the 

 greater or more continued proximity of some vast quantity of plutonic 

 rock as granite or syenite, and that thereby the beds, which must be 

 regarded as part of the general series of metamorphic rocks in that 

 region, were in part (and especially the more felspathic varieties) sub- 

 jected to a process of partial fusion and re-arrangement of particles, yet 

 were not sufficiently altered to efface all evidences of their original strati- 

 fied structure. This may account for the very highly crystalline condi- 

 tion of the gneiss under description. - 



Tlie finest development of this rock may be seen at and near Tia- 



gar-Droog, at Yellanasur (Ellavanasur) ; at the 

 Typical localities. 



Yedda Kul rock, south-east of the latter place ; at 



the Cunatur hill, 8 miles north by west of Oolundoorpetti (Wulen- 



durpett of map) , and between the Paushur hill and Tirukovilur, on the 



south side of the Punniar river. North of that river these rocks may be 



well studied almost anywhere between the line drawn from Mannalurpett 



to Tandri and the great bay of alluvium which runs up the Gingee river 



northwards from Vicravandy. In the northern part of this area the beds form 



the Gimga varum cluster of hills, east and south of Vaturvallum, which 



may be regarded as merely the southern portion of the Gingee group of 



hillsj into which the beds appear to be continued. Tliese hills present a 



very unusual appearance when compared with those 

 Appearance of the hills. . . . . 



of the normal varieties of gnieissic rock ; they ap- 

 pear to be made up of innumerable, large, more or less rounded blocks, 

 which on the ridges often stand out as fine tors. The spaces between 

 the blocks are closely filled by a luxuriant growth of generally thorny 

 climbing and other shrubs ; more rarely by trees. Between the wea- 

 thered blocks and the dense shrub growth the solid rock is l)ut rarely to 

 be seen, and the hills themselves are rendered almost inaccessible. The 



( 299 ) 



