NOTE ON THE LATEUITB OF OIIISSA. 281 



The term laterite has been vaguely applied to many forms of rock, 

 , , all agreeing in being ferruginous, but A'arying 



Employment of the o a a a ' Jo 



term •' Jatcrite." j„ Coherence and in composition. In Orissa and 



Bengal, it has usually been confined to the dark reddish brown substance 

 so commonly seen on the surface of the ground ; and which, when 

 exposed to the action of the weather, assumes a rough nodular surface, 

 and is freq^uently permeated by hollows of irregular shape and direction, 

 It also becomes covered with a glaze-like coating of brown peroxide of 

 iron. 



On a careful examination of this rock in situ, it is seen that it corn- 

 Comprises two differ- P^''^^^ *^^° ^i"'^^' essentially distinct in nature and 

 entrociis. Composition, and that one particular form invari- 



ably overlies the other wherever the two occur together. 



I. The form which generally appears at the surface, (it being rarely 



that the lower kind is exposed by tlie denudation 

 Surface " laterite." 



of the upper), consists mainly of round ferruginous 



nodules, about | to i of an inch in diameter, in a matrix of dark reddish 

 brown clay, which is generally more or less sandy. The nodules have 

 a coating of brown hydrated peroxide of iron, and, when broken, some 

 are seen to be black inside, others appear to be formed of concretionary 

 peroxide of iron, others again are evidently ferruginous pebbles of de- 

 composed gneiss, or of sandstone, if that rock prevail in the neigh- 

 bourhood. These little nodules are frequently scattered over the 

 country by the denudation and disintegration of the deposit containing 

 them. " ' 



In places this substance is so soft that it may be cut, though with 

 Its state of aggrega- ^^ifficulty, with a spade ; in other places it hardens 

 ''O"- into a firm rock, sometimes cohering only in the 



form of large blocks, the intermediate portion remaining loose and 

 gravelly, but frequently forming a hard mass which covers the surface 

 for considerable areas. It is only at the surfoce that this rock becomes 



