APPENDIX. 39 



APPENDIX. 



Previous views on the Origin of Laterite. 



An account of the geology of Malabar would hardly be complete without some 

 reference to the views which have been held as to the origin of laterite. These views 

 vary so much that I have preferred to discuss the origin of the Malabar laterite 

 on the evidence found in Malabar alone, and to keep all reference to the laterite 

 of other areas quite separate. 



Much of the difference of opinion on the subject seems to have arisen from 

 a want of agreement as to the exact meaning of the term. 



Some writers appear inclined to restrict the term to rock formed in one parti- 

 cular way, and to exclude all laterite rocks that can be shown to have originated 

 in any other manner. But the name, as originally proposed by Buchanan, 

 appears to have been a purely lithological term, for he does not discuss the mode 

 of origin. If any rock is, in hand specimens, undistinguishable from laterite, 

 there is no reason why it should not be called laterite, whatever its mode of origin 

 may have been. 



Other writers, on the other hand, have used the term too laxly, and have called 

 rocks laterite which should rather be called lateritic ; but it must be admitted that 

 it is hard to draw a line between a laterite containing pebbles and a conglomerate 

 in which the pebbles are cemented together by laterite. 



The number of writers who have discussed the origin of laterite is very great, 

 and it would be useless to enumerate all ; but the following account contains 

 references to all the more important. 



Dr. Buchanan, who first gave the name of laterite, does not, in his first account 

 of it, discuss the mode of origin of the rock ; but in a paper on the minerals of the 

 Rajmehal Hills he says that the laterites observed there must " be considered as 

 a kind of breccia, as they contain ferruginous nodules in an argillaceous cement." 1 

 By the term breccia he evidently means conglomerate. 



Benjamin Babington, 2 who in 182 1 described a journey from Tellicherry (in 

 North Malabar) to Madras, says that the hornblende of the gneiss of the country 

 decomposes into red oxide and the felspar into porcelain earth, thus forming 

 laterite. Where exposed, the earth is washed away leaving the red oxide in the 

 form of a porous ferruginous stone. This view, it will be seen, does not differ very 

 much from that put forward in this report. 



Another view was brought forward by Dr. Voysey, 3 who in 18 19 examined 

 parts of the Nizam's Dominions. His observations on laterite were not publish- 

 ed till after his death, and the fullest account of them will be found in the Journ. 

 As. Soc, Beng., for 184.4. ar| d 1850 ; but a short notice was published in the same 

 journal for 1833. At Bidar he found iron clay — this was his term for laterite — pass- 

 ing down " into wacke and thence into basalt." 4 He looks upon the iron clay as a 

 " muddy eruption." 5 



1 Gleanings in Science, III, 5. 

 Geol. Trans., 1st series, V, 328. 



3 Journ. As. Soc, Beng., II, 29S, 392; XIII, 853; XIX, 190, 26> The last' two partly re- 

 printed in Carter's Geol. Papers on Western India, 48-65. 



4 Geol. Papers on Western India, 61. 

 * Loc. cit., 63. 



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