190 Correspondence—J. W. Evans. 
and popular language. Mr. Scrivenor appeals to the usage of 
engineers, but to the best of my recollection I never heard the term 
applied to any other material by a South Indian engineer during my 
four years’ residence in the State of Mysore. 
Curiously enough, at the date of the publication of the second 
edition of the Manual of the Geology of India in 1893, no complete 
analysis of laterite from the Peninsula of India was known, and its 
characteristic chemical composition was still unrecognized. Since 
that date numerous analyses of laterites from widely distant tropical 
localities have been made. The most recent information on the 
subject may be obtained from a second paper by Max Bauer (Veues 
Jahrb. fir Min., etc., Festband, 1907, pp. 33-90), a report from the 
Imperial Institute on specimens from the Balaghat District of the 
Central Provinces of India (Rec. Geol. Surv. Ind., 1908, vol. xxxvu, 
pp. 2138-20; Bull. Imp. Inst., 1909, vol. vii, pp. 278-85), both of 
which contain full information on previous literature and analyses, 
and an interesting contribution by J. Chantard & P. Lemoine ( Comptes 
Rendus Acad. Sct., vol. cxlvi, pp. 239-42; Bull. Soc. de 0 Indust. 
Min. St. Etienne, 1909, ser. rv, vol. ix, pp. 1-37), in which are 
traced out the changes that have taken place in the formation of 
laterite on the assumption that the amount of titanium oxide has 
remained unaltered. 
As a result of the work that has been done it is found that the 
chemical composition of laterite varies within wide limits according 
to the nature of the original rock, so that it is not necessarily the 
same as that of bauxite. One feature, however, remains constant— 
the small amount of combined silica in proportion to the alumina 
present, and it is in this respect that laterites differ from clays, which 
also occur as tropical decomposition products and are sometimes 
incorrectly described as laterites. If, again, the amount of ferric 
oxide is large, it is apt to form ferruginous concretions, which are 
commonly referred to as lateritie iron ore; and if, as sometimes 
happens, the aluminium hydrate is in course of time washed away, 
an accumulation of scoriaceous iron ore may be left behind which is 
certainly not laterite, though it may be derived from it. It is 
probably this which has given rise to the misuse of the term for 
surface iron ore, which is common in some of our colonies. 
It would be difficult to conceive a stronger case for the application 
of the rule of priority than the present. The term laterite was 
applied as early as 1807 to a well-marked rock type, and has 
continued in use ever since with the same signification, which has 
been adopted by writers on tropical geology in Germany and France, 
and received the endorsement of authorities like Keyser (Lehrbuch, 
1909, vol. i, pp. 282-3). At the same time it has met with general 
acceptance in this country. Yet we are told that it must be 
abandoned because it has been wrongly employed by Colonial 
engineers who are unacquainted with the material to which it is 
properly applied. 
Joun W. Evans. 
ImpEriaL Institute, S.W. 
