168 CRETACEOUS ROCKS OF S. INDIA. [PaRT II. § 2. 



Two miles South of Vellum a bed of laterite, which is exposed at the 



surface, (and probably belongs to the Cuddalore 

 Laterite bed at Vellum. 



beds,) is largely worked for building purposes by 



the natives. It is, when freshly cut, a porous, ferruginous, sandy clay, 



which hardens on exposure to the weather, and only after some months 



becomes brown and glazed on the surface, in the manner characteristic 



of laterite. 



The group does not probably extend much to the West of Vellum, 



Extent of formation ^here it forms a little escarpment such as usually 

 South of the Cauvery. founds the formation. But as nothing is seen of 



any rock for some miles to the Westward, owing to the thickness of the 

 soils which cover the face of the country, its exact limit in that direction 

 cannot be ascertained. To the Eastward it extends as far as near 

 Pamani and then disappears beneath the alluvium of the Cauvery delta, 

 which also bounds it on the North ; but to the South it appears to extend 

 into Tondiman's country, and how much further is not ascertained. The 

 only other good section exposed to the South of the Cauvery, besides 

 that of Vellum, is in the moat of Tanjore, the fort of which stands just 

 on the Northern edge of the formation, overlooking the delta of the 

 Coleroon and Cauvery. 



In the Trichinopoly district, North of the Coleroon, the formation re- 

 appears to the South of WodiarpoUiam, and occu- 



Formation North of the 

 Coleroon in Wodiarpol- pies the greater part of the talook of the same name. 

 liam. 



Its occurrence at Kondamungalum, where it forms 



a very fine escarpment from 60 to 80 feet in height, has already been 



described. Beyond this very little is seen as far as the Vellaur, where a 



fine section of the lowest beds, of about a mile in length, is exposed in 



the bank of the river, above Plaunthoray. The rock 

 At riaunthoray. -^ 



which is here a soft sandstone, is mottled white and 

 pink. The latter, which is the prevalent color of the rock, being due 

 to ferruginous infiltration, while the former marks those spots where 



