50 GEOLOGY OF TRICHINOPOLY, &C. [ChAP. IV. 1. 



this band of hard roek itself seems to have once formed a very ancient 

 bund across the gorg-e^ backing up the waters, which formed the thick 

 alluvial deposit lying to the west of this rocky band ; but it, like the 

 more recent artificial one, had been broken through. 



I. Crystalline Limestone. — This rock is of rare occurrence in the 

 districts under consideration, being found only at five or six places. 

 It occurs at Naivailie on the left bank, and at Mootum on the 

 right bank, of the lyaur, both in the Moosery division : at and near 

 Culputty, in the Vettycutty division : and it crosses the Madura road 

 16 miles to the south of Caroor; all partly or entirely in the district 

 of Trichinopoly. It occurs also at Shattumboor, 7 miles to the 

 south-west of Namcul, in the Salem district. In the country at the 

 south-west corner of the map, are bands of limestone extending 

 over a length of more than 12 miles, and stretching far into the 

 district of Coimbatore. The Madura road is crossed by four of these 

 at a short distance to the north of Polliam, 16 

 miles south of Caroor. From this point they 

 stretch in continuous Imes in an east-north-east direction to a large boss 

 of gneiss, around which two of the limestone bands make a slight bend 

 or curve, and then pursue their original course (although occasionally 

 covered up and concealed by alluvium and gneiss-debris) to a point south- 

 west of Keeranore. In addition to the three principal bands, there are 

 others of greater or less extent and magnitude, running in the same direc- 

 tion, which are best seen between Kurrinculputty and Nursingaparum. 

 A great number of small bands cross the old boundary bank between the 

 districts of Coimbatore and Trichinopoly, but these are eventually united 

 into thicker beds or spread out into rocky surfaces of thirty or forty 

 yards in width, which disappear beneath the alluvial deposits of the two 

 streams running to the north, and re-appear as a nearly equal number of 

 beds crossing the country further to the east. Two beds also occur about 

 a miles to the north-east of these at Keeranore, one of which was 



