60 



Sketch of the Malayan Peninsula. 



[Jan. 



overlaid by a thin crust of laterite (a ferruginous clay considered as 

 associated with the trap formation)." This opinion of Mr. Conybeare 

 in regard to the igneous origin of laterite is evidently founded on that 

 of Yoysey, a name well known in Indian geology ; who regarded late' 

 rite to have a common origin with greenstone, basalt and wacke, from 

 the insensible degrees by which, he says, they pass into one another, 

 differing only as to the degree of pressure to which they were sub- 

 jected when under fusion. 



The opinion of some later Indian geologists is in favour of its hav- 

 ing resulted from the decomposition of granite, sienite, hornblende, 

 and other crystalline rocks. I have little doubt however that essen- 

 tially different rocks have been described under the name of laterile. 

 The true laterite, first described and named by Buchanan, is that of 

 Malabar and Canara, which I have seen between the western ghats or 

 Cordilleras, and the coast, occurring like overlying basalt, in tabular 

 and dome-shaped masses; as also at Malacca. I have seen a hand 

 specimen of sandstone from Singapore, penetrated and shattered by 

 the laterite. But whether it rises through the associated rocks by 

 dykes or fissures, I have not hitherto had an opportunity of witnessing. 

 As far as my own observation extends, no marks of true stratification 

 or the presence of organic remains have been detected. The exterior 

 of detached weather-exposed blocks of primitive greenstone of the 

 western ghdls decomposes into a thin ferruginous crust, which might 

 easily be taken for laterite at first sight ; and I have seen veins and 

 thin beds of a cellular haematitic iron ore traversing the gneiss of 

 Mysore, which closely resembles some varieties of the true laterite. 

 Dykes and organic remains should be diligently searched for, in order 

 to set the question at rest: their not hitherto having been met with is 

 by no means a proof that they do not exist. It must not be under- 

 stood from what has been said above that laterite exists only as a thin 

 crust covering the granite, and other rocks near the coast. I have seen 

 it in the middle of both the Malayan and Indian peninsulas, composing 

 entire hills, rising to the apparent height of four hundred feet. The 

 Observatory at Trevandrum is said to be erected on a hill composed of 

 a solid mass of it. At Beder it occurs on granite and passes into both 

 vracken and basalt (Voysey). The laterite of the red hills near 

 Madras is supposed by Mr. Cole to be of detrital origin. That of the 

 Malay peninsula and contiguous islets resembles in mineralogical 

 character, the rock of the Malabar coast is quarried in a similar man- 

 ner, and was extensively employed by the Dutch and Portuguese, in 



