102 



On the Geological characters of the 



[July 



the red ochry part is the matrix, and the kidney shaped interstices are 

 rilled with white earth : the whole is alluvial being formed from the 

 washings of the ghaut mountains. In these the hornblende uniformly 

 decays into a red oxyd, and the felspar into porcelain earth. Why these 

 are aggregated in their present form, the red particles forming the 

 matrix, the white the kidneys, I cannot explain. Whenever the allu- 

 vial rock, thus formed, is exposed, the white parts are washed away, and 

 a porous ferruginous stone is left behind. Such is the general formation 

 of Malabar. The primitive rocks underneath possibly appear in many 

 places above this Coast: I know them to do so, at the place about mid- 

 way between Calicut and Tellicherry, at Moy and at Tellicherry. 

 Four or five miles inland from Calicut, there are two low hills, com- 

 posed of cubic iron ore. These are probably in beds in the primitive 

 rock of the country, though I could perceive nothing but the laterite 

 around. From Tellicherry the laterite forms the hills, until you arrive 

 at the foot of the ghauts, which mountains are composed in general of 

 a compound rock, which I call gneiss, though in some places quartz is 

 intermixed with mica. The mountains formed by this rock, and which 

 line the western side of India, are not of very rugged outline; on the 

 contrary, they are in general wooded to the top : they are very high. 

 Bannason hill, which is among the highest, is said to be 7,000 feet 

 above the sea. This rock is every where in strata highly inclined, 

 almost vertical. It has in some places more quartz, in some more 

 felspar, in some more hornblende ; thus varying in colour, and aggre- 

 gating in streaks. Further on between Peria and Manantoddy, it con- 

 tains much precious garnet, and is exceedingly tough. In its decay it 

 becomes of an ochry red. Near Manantoddy, there is no fresh exposi- 

 tion of rock : there is indeed a quarry of laterite, about a quarter of a 

 mile from the hill, on the old Madras road. It is worked close to the 

 surface, and the workmen seem never to cut down beyond the depth of 

 a few feet. When the workman has chopped away at the four sides 

 and made the stone flat at the top, he makes a cut or two horizontally 

 underneath, and the mass immediately splits in that direction." 



It will be here seen, that, instead of a relation between laterite and 

 trap, or any erupted rocks, being alluded to, a detrital origin is dis- 

 tinctly indicated by this author ; which again is stated to be his opi- 

 nion at p. 338, when speaking of the rocks in Mysore. 



" Their (the rocks) decay leaves a whitish soil beneath the surface, 

 I suppose from the quantity of felspar they contain. The dark parti- 

 cles of hornblende become ferruginous, and this is in general the top 

 of the soil, which is reddish. Little fragments also become rounded, 

 and in some cases, as at Bangalore, the w^hole is settled into the ferru- 

 ginous stone mentioned as seen on the Malabar Coast. In the detritus 

 of these rocks, it does not seem that particles of felspar are washed 



