Dr. L. Leigh Fermor — What is Laterite ? 455 



the Indian manganese- ore deposits, many chances of striking a field 

 acquaintance with laterite. Consequently, following the fashion of 

 theorizing about laterite, I took the opportunity, in my memoir on the 

 Manganese-Ore Deposits of India, 1 of expressing my own views, at 

 the same time summarizing some of the theories previously advanced, 

 especially with reference to Indian laterite. Concerning the origin 

 of this rock I advanced the views (1) that rocks of more than one 

 origin were included under the term laterite, (2) that in discussing 

 the origin of this rock geologists had not always recognized this fact, 

 and (3) that consequently the divergent theories put forward were in 

 some cases invented to explain dissimilar occurrences. Further, the 

 opinion was expressed that no profit could he derived from the further 

 discussion of this question unless each author discussed a specific 

 occurrence, of which a detailed description was at the same time given, 

 so that no confusion should arise in the future. An actual case was 

 then discussed, showing that two parts of one deposit of laterite have 

 probably been formed in two different ways — one by the alteration 

 of rock in situ, and the other by chemical deposition from a body 

 of water. 



In this chapter (p. 370) the term laterite was defined implicitly, 

 hut not explicitly, in the following passage : — 



' ' This rock consists essentially of a mixture of hydrated oxides of iron and 

 alumina, with often a considerable percentage of titania," 



this definition being intended to apply to all varieties of laterite 

 formed in situ, but not to such varieties of the so-called low-level 

 laterites as are of detrital origin, nor to any detrital or reconstructed 

 varieties of high-level laterite ; it is only to laterites formed in situ 

 that the present paper applies, except where otherwise stated. 



I may quote also another passage (p. 379), which does not advance 

 any theory as to the origin of laterite, but states what I helieve to be 

 the result of lateritization of a rock. The passage is as follows : — 



"It is also generally recognized that the formation of this type of laterite 

 involves the disappearance, probably in solution, of the silica, lime, magnesia, 

 and alkalies, of the original rock, with the concentration of the oxides of 

 aluminium, iron, titanium, and sometimes manganese, to form laterite." 



In holding these views I was, of course, but repeating Professor 

 Bauer's 2 and Sir Thomas Holland's 3 ideas on the composition of 

 laterite, and consequently on the definition as to what is laterite that 

 naturally follows. 



During 1909 and 1910, however, current geological literature was 

 enlivened by two discussions ahout laterite : one of them, in the 

 pages of this Magazine, referring to the use of the words laterite 

 and bauxite; and the other relating to a paper entitled "The Origin 

 of Laterite " read before the Institution of Mining and Metallurgy 

 by Mr. J. Morrow Campbell. 4 As many of the participants in these 

 discussions do not seem to have given sufficient attention to the views 

 of Indian geologists on a rock which is, after all, primarily an Indian 



1 Mem. Geol. Surv. India, xxxvii, ch. xix, pp. 370-89, 1909. 



2 Bauer, Neues Jahrb. filr Min., etc., ii, p. 163, 1898. 



3 Holland, Geol. Mag., Dec. IV, Vol. X, pp. 59-69, 1903. 



4 Trans. Inst. Min. Met., xix, pp. 432-57, 1910. 



