Dr. L. Leigh Fermor — What is Laterite ? 513 



already been quoted by Mr. Crook, 1 whilst Dr. Evans 2 puts the matter 

 in a nutshell when he says — 



"Buchanan found a rock widely extended in India which was unlike anything 

 with which he was familiar, and he thought that it required a name. As bricks 

 were made of it (not because it resembled a brick) he called it laterite, certainly 

 without intending to include under it all materials of which bricks could be 

 made. I admit that he did not know its true chemical composition, but in s'pite 

 of that it must be accepted as the type of what we ought to call laterite." 



Buchanan's term was adopted by Indian geologists, and has been 

 widely applied in many parts of India; laterite has consequently been 

 described in very numerous papers on Indian geology, 3 but until the 

 last few years without much knowledge on the part of the author^ of 

 the chemical composition of the rock ; it follows, therefore, that this 

 term has sometimes been applied to rocks that, had they occurred in 

 a temperate clime, would have been called by some more ordinary 

 name, such as clay, lithomarge, iron-ore, etc. 



Mr. Philip Lake, in the Appendix to his memoir on the Geology of 

 the South Malabar, 4 says — 



' ' Some writers appear to restrict the term to rock formed in some particular 

 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 pure 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 rock laterite which should rather be called lateritic; 5 but it must be 

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

 a conglomerate in which the pebbles are cemented together by laterite." 



As long as no chemical work had been carried out on laterite it was 

 necessary to accept Lake's view that any rock indistinguishable from 

 laterite in hand-specimens should be called by this name. But. how 

 that we have chemical information on the composition of these rocks 

 it seems necessary to use more discrimination, and in refusing the 

 term laterite to lithomarges, and in advocating the qualification by 

 the adjective lithomargic of those laterites containing considerable 

 quantities of this mineral, we shall be acting in spirit with Buchanan, 

 Avho would not have wished to comprise under one term such 

 dissimilar substances as lithomarge and the mixture of hydrated oxides 

 to which the term laterite should be restricted ; we are also not departing 

 far from Lake's view, for when once one has established by the aid of 

 analysis the difference between true laterites and those containing a 

 considerable quantity of lithomarge, and between both of these and rocks 

 that are almost wholly lithomarge, it is easy in most cases to recognize 

 the differences in hand-specimens; in any case it is not difficult to 

 make a qualitative test for combined silica in any doubtful case. 



1 Geol. Mag., 1909, p. 525. 2 Loc. cit., 1910, p. 381. 



3 Resumes of this work and of that of other previous writers are to be fpund 

 in the following works : P. Lake, "Geology of South Malabar," Appendix (Mem. 

 Geol. Surv. India, xxiv, pp. 239-46,1891); G. C. Du Bois, "Beitragzur Kenhtnis 

 der surinamischen Laterit, etc." (Tschermak's Mitt., xxii, pp. 4-18, 1903) ; 

 C. Guillemain, "Beitrage zur Geologie von Kamerun " (Abh. Konig. Prpuss. 

 Geol. Landesanstalt, N.S., vol. lxii, pt. viii, on Laterite, pp. 242-323). 



4 Mem. Geol. Surv. India, xxiv, p. 239, 1891. 5 The italics are mime. 



DECADE V. — VOL. Vin.— NO. XI. 33 



