254 



Memoir on the Geology of the 



[Oct. 



Neelgherries, which appears also to have been the case with the laterite 

 of the other parts of the peninsula. 



As it is by accumulated facts, and accurate information on the struc- 

 ture, associating rocks, &c. that a rock may be properly characterized, 

 I hope that my observations, (such as they are), will contribute to aug- 

 ment the number of facts, respecting the nature, composition, and 

 origin of the laterite ; and prove acceptable as an addition to the 

 data, indispensably necessary in enquiries on such subjects ; which, 

 when collected in sufficient number, it is only required that an able, 

 patient, laborious and active geologist should arrange, and compare 

 with those he himself has attained by personal inspection, and exa- 

 minations of the different localities where the rock is found, to arrive 

 at something like a definitive conclusion regarding this, as yet, ob- 

 scure subject ; because to trust to hand-specimens, in researches and 

 enquiries of this sort, would be equivalent to the fodere Isthmum. 



As far as my short stay in India, and my limited and confined obser- 

 vations, enable me to speak, on this intricate question, I think that* 

 among well informed people, under the name of laterite two, or rather 

 three, sorts of rocks are included ; to say nothing of the common mis- 

 take of misapplying the name to the decomposed rocks of the primi- 

 tive class, or to any other that has a red, ochreous colour, and 

 softish consistence. 



The first species, of which I am going to say a few words, I only 

 know by hand specimens in my possession, by having examined those 

 in the Museums of Madras and Calcutta, and by the description of 

 the late Dr. Ward ; therefore I can say but very little regarding its 

 geological position, and associating rocks. It appears that it is very 

 common in the eastern Islands and Malacca ; it seems to be an unstrati- 

 fied rock, perforated by numerous tortuous, tubular cavities, which 

 are either filled or lined with pale yellow decomposed felspar ; the 

 texture of the rock between these perforations is compact, with a 

 dull fracture, and adheres to the tongue. The colour is ochreous, 

 with spots of pale yellow decomposed felspar ; it does not appear to 

 contain any other mineral, or extraneous substance, except the felspar, 

 and ferruginous clay — fragments or grains of quartz are never met 

 with in this rock (at least in the specimens I mentioned)— -there is not 

 the most distant appearance of a breccioide or conglomerate structure, 

 and its specific gravity is a good deal less than the other two species. 

 In short it is a simple, compact, tubular, or perforated iron stone. I 

 have not Dr. Ward's account of this rock to consult ; I therefore can- 

 not say positively, but I think he says that it is invariably in an over- 

 laying position. 



The second is one which appears to have been described by many 

 geologists, and I also contributed my little portion of facts, on this 



