Chap. I.] economic geology. 211 



purpose, the shells being washed previous to burning. Similar deposits 

 occur at Pondicherry, and also at the Adyar, a few miles from 

 Madras. 



Brick Clays. The only clays used by natives for brick -making, are those 



All v'l -1 -sib of the fluviatile alluvial deposits, and more rarely of 

 "'^''^^"'^^- the superficial deposits, which cover the gneiss of 



the low country. The latter are in general but little adapted for the pur- 

 pose, consisting either of a sand, with too small a proportion of clay, or of 

 regur which, on the other hand, is an almost pure loam. Where the two 

 forms of soil meet and intermingle, are the best spots for the purpose of 

 brick manufacture. It is only in towns and some few large villages 

 that bricks are much used, the huts of the agricultural classes being, as 

 is usually the case throughout India, built of mud Avith thatched roofs. 

 The native process of brick-making is a rude form of that commonly 

 practised in more civilized countries. The clay, which is always so 

 sandy, as to enable the workmen to dispense with the preliminary process 

 of pugging, is mixed by the aid of a shovel, with sufficient water to 

 render it a semi-fluid paste, which is rudely and rapidly moulded in 

 a wetted mould, and the bricks, being dried in the sun, are burnt in a 

 kiln in the usual manner. 



The native bricks are soft and bad, frequently containing cavities 

 and irregular in shape, but this is due to want of proper cai-e in niixino- 

 and moulding and to insufficient burning. It is probable that the same 

 clays used by them would yield excellent bricks under an improved 

 process. 



Fine clays and pottery materials. The Cretaceous rocks and plant 



beds of Trichinopoly yield several fine clays 



^Pottery materials avail- .^^j^ adapted for the manufacture of pottery ; 



and other materials used in the ceramic arts_, viz., 

 China stone and kaolin, felspar, flints, and gypsum, are all obtainable 

 within the area described in the foregoing report. None of these are 



