216 CRETACEOUS ROCKS OF S. INDIA. [PaRT III. 



great part of a similar soil ; small patches of " Soial" are also frequently 



met with on the gneiss, to the West of the Cretaceous rocks in South 



Arcot, chiefly where the prevailing soil is regur. The earth is collected 



by washermen and used instead of soap for washing cloth. The soda is 



frequently mixed with common salt, and probably with other soluble 



salts, but it has not been analysed. 



Iron Ores. The cretaceous rocks contain in several places ferruginous 



„ , , . nodules, which mounds of old slags prove to have 



Cretaceous rocks lor- ' ° *■ 



merly used, been worked by the natives at some former period. 



The greater part of the plains is now too denuded of jungle to allow 



of fuel being consumed in the production of iron, however abundant 



its ores may be, and no iron has been made in either Trichiuopoly or 



South Arcot (so far as I could learn from frequent interrogations,) 



within the memory or even the traditional knowledge of the existing 



generation. All iron used by the natives of these districts is obtained 



from Salem, where the neighbouring hills still yield wood, for smelting 



the rich magnetic ores so abundant in that district. 



Ferruginous concretions, which have been at one time worked by 



the natives, occur in the Ootatoor beds to the 

 Localities. c^ ^ p i-\ 



South of Ootatoor, and in the lower beds of the 



Arrialoor group, to the South of Arrialoor : also in higher beds of the 

 same group near Thaloor fragments of rich iron ores occur, cover- 

 ing the ground, and bedded in the ferruginous soil, near Konda- 

 mungalum (page ]S8), being derived, in part at least, from the 

 ferruginous beds of the Cuddalore group. 



The iron ores used at the Porto Novo Iron Works were the magnetic 

 ores of Salem district. 



Co^'per Ores. The gneiss in the neighbourhood of Olapaudy and Vapoor 



(in the North of Trichinopoly,)shows frequent stains 

 At Vapoor. ,, iit.,ioi 



of copper, and m a small nullah, to the South 

 of the latter place, I found two or three pieces of cupriferous veinstone, 



