1838.] 



On the Lateritic Formation. 



343 



into the sea. A section just on entering- the town shows a rock decom- 

 posing apparently into lithomarge, and in some spots almost into laterite. 

 About 7 miles from Cannanore, in the direction of Manantoddy, there 

 is. a good deal of quartz rock, having a pinkish and decomposing aspect, 

 and further on the rocks are ahnost altogether of hornblende or sienitic 

 granite. The prevalence of laterite all along the western coast, may 

 truly attach to it the character of an iron bound coast, used more gene- 

 rally in poetic than scientific language. This laterite is of a soft con- 

 sistence, and of a very iithomargic character in some specimens — it is 

 mottled red and white, contains numerous sinuosities, which resemble 

 the worm-eaten cavities in decayed wood ; and its colour is lighter, and 

 more inclined to pink, than in the laterite of the interior. When re- 

 moved from its bed, it is perfectly soft, but hardens on exposure, and in 

 this state is employed for building by the natives, whose houses in most 

 parts of India are of mud, but frequently here of laterite. 



But to leave the coast and take to the interior. Around Bangalore, and 

 in many other localities, there is a harder and more quartzose kind of la- 

 terite ; less lithomargic and less clayey in appearance, and containing 

 fewer sinuosities. On inspecting many of the granite rocks v.'hich ele- 

 vate themselves above the surface of the ground and stand up several 

 feet from it, there will often be found a coating of quartz, the softer 

 portion of the rock having fallen away, leaving this as if plastered on. 

 This appearance shows us in some measure the mode in which the quartz 

 laterite may be formed. Imagine a small mass of gneiss, just showing 

 itself above ground, or in some places slightly covered with a soil the 

 result of decomposition. If the surface of the rock should contain 

 much quartz, say a large bed of it, instead of sulfering decomposition 

 like the felspar or mica, the pieces of quartz, now formed or forming 

 into pebble, would arrange themselves together, the softer and more fer- 

 ruginous parts decomposing, and a laterite, simple in its nature, and 

 having fewer cavities and sinuosities, would be formed. A thick 

 bed of quarl2s laterite of this kind is found near a village on 

 the road to the fort, close along gneiss, only a few feet from the 

 ground, and attached to it ; a laterite has therefore been formed, the 

 thickness of the quartz bed ; and it is the presence of quartz in 

 large quantity on the surface of a rock which may account for the forma- 

 tion. It is not universal, but confined apparently to spots vvhere quartz 

 abounds. For instance, immediately on a line with this place and on the 

 Other side of the cantonment close to the last building appropriated for 

 the stand of arms of a native regiment, there is a deep pit from which 

 a very pebbly kind of laterite is taken to repair the roads. It is no 

 here well defined, and is generally merely a congeries of pebbles which 



