T. H. Holland — Constitution of Laterite. 59 



but I do say that so far both evidence for and against has been 

 unsound. We must carefully collect and examine all available 

 facts both archseological and geological, as only by a combination 

 of both can the question of the age of different groups of flints and 

 the presence or absence of Palaeolithic man be determined. 



IV. — On the Constitution, Origin and Dehydration of Laterite. 



By T. H. Holland, A.R.C.S., F.G.S., Geological Survey of India. 

 I. Introduction. 



A DESCRIPTION by Professor Max Bauer ^ of rock-specimens 

 collected in the Seychelle Islands includes a special discussion 

 of the laterite, which, he shows, agrees in essential characters with 

 bauxite. As bauxite is the most valuable source of aluminium, and 

 its origin has hitherto been without a completely satisfactory 

 explanation, this work by Bauer opens a question of double interest 

 to the owners of land in the humid parts of the tropics. 



As with many such interesting questions, more than one worker 

 has blundered near the correct solution without feeling his con- 

 victions suflSciently mature for publication.'^ 



Apart from priority secured by publication, I shall not be 

 departing far from justice to others in giving Dr. H. Warth, then 

 of the Geological Survey of India, the credit of having first, or at 

 any rate independently, suspected laterite and bauxite to be 

 essentially similar. In 1893 Dr. Warth found a specimen in the 

 Palni Hills, Madras Presidency, which so strongly reminded him of 

 bauxite that he had an analysis made, and this showed over 60 per 

 cent, of alumina (Alj O3). The analysis did not, however, show 

 the constitution of the laterite, and did not distinguish between the 

 alumina combined with silica and that present as a simple hydrate. 

 For various reasons, constituting a story in itself, this question had 

 to give place to others, and was merely noted by Dr. Warth and 

 myself as one to be kept in mind. 



During the four years following, my observations in Peninsular 

 India gradually led me to suspect that kaolin and many other 

 hydrated minerals, generally regarded as weathering products, have 

 not originated by the action of subaerial agents, but some, if not all, 

 of them are produced by vapours from subterranean sources, whilst, 

 on account of its peculiar distribution, serpentine must remain under 

 the suspicion of being due to submarine action until its mode of 

 occurrence in India can be explained on other grounds.^ Kaolin 



1 Bauer, " Beitrage zur Geologie der Seychelleii" : Neues Jahrb. flir Miu., etc., 

 1898, vol. ii, p. 163. 



- Cf. Henatsch, " Ueber Bauxite und ihre Verarbeitung " : Inaug. Dissertation, 

 Breslau, 1879. Mr. F. E. Mallet, to whom I am indebted for reading the proofs of 

 this note during my absence from England, approached dangerously near comparing 

 laterite with bauxite when he pointed out in 1881 that the ferruginous beds of Ulster, 

 associated with bauxite, resembled the laterite on the Deccan Trap in India. ( " On 

 the ferruginous beds associated with basaltic rocks of North -Eastern Ulster, in relation 

 to Indian laterite": Bee. Geol. Surv. Ind., vol. xiv, p. 139.) 



' Holland, "A Contribution to the Discussion on Ecck- "Weathering and Serpenti- 

 nization" : Geol. Mag., 1899, Dec. IV, Vol. VI, p. 540. 



