ClIAr. VIII.] ECONOMIC GEOLOGY. 147 



mentioned. These rings, the links within which are moveable, and the 

 projecting corners, are carved out of single blocks of gneiss. Such may 

 be seen at the Strimustrum pagoda. 



Rough and undressed blocks of every variety of gneiss are exten- 

 Uses of undressed sively used in all parts of the gneiss countiy for 

 ^ °^^' bunds of tanks and rude walls, while they have 



also been employed with very great advantage in the construction of the 

 beach groynes at Tranquebar. In the neighbourhood of Caroor and in 

 the Coimbatoor district generally, culverts and small bridges on the high 

 roads have been put together in a Cyclopean style of unhewn gneiss blocks. 

 In enumerating the applications to which rude blocks of gneiss 

 have been put, we must not omit one which is of more interest perhaps 

 to antiquarians than to geologists ; we refer to those ancient druid-like re- 

 mains called " Karumbar rings,^^ scattered here and there over the countiy. 



They were observed at Orundamullay, on the 

 Karumbar rings, , • -, n -n n i 



east side or roonganoormullay, a low rocky hill 



about 4 miles south-west of Trichinopoly. Also in considerable num- 

 ber south and south-west of the village of Mala Nungaveram, about a 

 mile and a half north-west from the old ^ PubKc Bungalow^ at Nun- 

 gaveram (Nm*asaveram on the Atlas Sheet,) 13 miles west of Tri- 

 chinopoly, on the upper road to Caroor. Again close to the road a mile 

 and a half south-east of the bungalow at PoodoopoUiam, beside a num- 

 ber of projecting ridges of gneiss ; and in many other places. 



Where these Karumbar rings are imperfect, as are some at the two 

 latter localities, it is easy to mistake them for rocks in situ, and to find 

 great apparent contortion and variation in the strike of the beds, the 

 blocks being placed on end, as if to show the fohation. 



The crystalline limestones of our area, so far as we are aware, have 



never been put to any use in masonry, excepting 



Crystalline limestones. , „ i ii i i i •^ i , n 



perhaps a lew rough blocks, loosely piled together 



in the bund of a tank. Those, however, lying to the west, both at 



Sunkegherrj^ Droog, in Salem district, and at Miiddakurray, to the south- 



( 369 ) 



