Dr. L. Leigh Fermor — What is Laterite ? 457 



In a second letter ' Mr. Scrivenor, in order to illustrate the confusion 

 surrounding the use of the term laterite, calls attention to the opinions 

 of Dr. Maclaren 2 and Mr. Mennell 3 that an alternation of wet and dry 

 seasons is necessary for the formation of laterite, and produces statistics 

 of rainfall at Malacca to show that at that place there is no such 

 alternation of seasons. And, whilst he admits that the rock called 

 laterite hy engineers in the Federated Malay States is ironstone 

 deposited in weathered rocks, Mr. Scrivenor maintains that there 

 exists in the State of Malacca an occurrence of rock that agrees with 

 Buchanan's definition of laterite. He concludes by conjoining the 

 doubt raised by Mr. Kilroe, 4 as to the necessity of tropical conditions 

 for the formation of laterite, with his own deduction that ati 

 alternation of wet and dry seasons is unnecessary. 



In another letter Mr. Scrivenor 5 replies to Mr. Crook to the effect 

 that the essential point of Buchanan's original definition of laterite 

 is that laterite sets when exposed to the air. Hence, if Crook's 

 dictum that laterite must contain free aluminium hydroxides is to be 

 accepted, he must prove that the setting of laterite is due to the 

 dehydration of aluminium hydroxides and not to that of hydroxides of 

 iron, as has been previously held. Mr. Scrivenor thinks that we can 

 dispense with the term laterite altogether, as having now too loose 

 a meaning, and use the term bauxite instead, for, according to passages 

 he quotes from Holland and H. and F. J. Warth, laterite and bauxite 

 are essentially similar. 



Dr. J. W. Evans 6 now comes to Mr. Crook's assistance to combat 

 Mr. Scrivenor' s suggestion referred to above, and maintains that in 

 India the term laterite is still applied, both in scientific, technical, 

 and popular language, in the sense in which it was used by 

 Buchanan over a century ago. He gives recent literature on the 

 subject, and summarizes matters in the following clear words : — 



"Asa 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 some- 

 times 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 lateritic iron ore.'" 



Mr. Crook 7 next returns to the attack and objects very strongly to 

 Mr. Scrivenor's proposed misuse of the term bauxite, and denies that 

 this word is yet available for petrographical use, maintaining that the 

 non-existence of the compound Al 2 3 2HoO as a mineral must first 

 be definitely established. 



Mr. Scrivenor, 8 in a further communication, replying to Dr. Evans, 

 reiterates his point that the term laterite must not be held to imply 

 the presence of free aluminium hydroxides in quantity ; he states that 



1 Geol. Mag., 1909 p. 574. 2 Op. cit., 1906, p. 546. 



3 Op. cit., 1909, p. 350. 4 Op. cit., 1908, p. 539. 



5 Op. cit., 1910, p. 139. 6 Op. cit., p. 189. 



7 Op. cit., 1910, p. 234. s Op. cit., p. 336. 



