NOTE ON THE LATERITE OF ORISSA. 285 



in wliich unaltered blocks of the subjacent gneiss rock, preserving its 

 foliation, were seen entirely surrounded by a mass of " Laterite." 



When sandstone forms the underlying stratum, it is seen to pass into 

 a ferruginous deposit, in a similar manner to that 

 in which the gneiss does. The resulting " La- 

 terite" is generally much more gritty, but sometimes it much resembles 

 tliat formed above gneiss. This is probably where the sandstone is 

 very felspathic. The rock, when formed by the alteration of sandstone, 

 may however always be distinguished by containing fragments of that 

 rock strongly impregnated with iron. 



* From the preceding description of these two forms of rock con- 



„ founded under the name of laterite, it fol- 



IrreconcilabiUty ot 

 the two forms. lows ' 



1. That the overlying form contains pebbles and boulders evidently 

 transported from some distance, and is consec[uently the result of depo- 

 sition from water. 



2. That the underlying form is clearly and unmistakeably the result 

 of the alteration, in situ, of the rock on which it rests. 



These two different rocks are clearly distinct therefore, both in com- 

 position and in origin. It is manifestly unscientific to continue to con- 

 found them under the same name. 



The name laterite was applied by Dr. Buchanan Hamilton in all 

 probability genericaliy. The name (brick-stone) however, was given 

 on account of the employment of the rock in building, a purpose to which 

 the detrital form is far more frequently applied, at all events in Orissa, 

 than is the variety formed by the" alteration of igneous or metamorphic 

 rock or of sandstone. The detrital form moreover is that most com- 

 monly seen and best known, and to it I shall consequently in the present 

 paper restrict the term of Laterite. 



* The two forms of Laterite have been remarked by several previous observers, and the 

 difference in their constitution is clearly explained in Lieut. A. Aytoun's account of the 



