Dr. L. Leigh Fermor — What is Laterite ? 563 



of non-lateritic material, and, although just within the limits for 

 laterite, yet judging from Professor Harrison's descriptions and the 

 composition of the earths taken individually, I think he would be 

 more in conformity with usage were he to use the term lateritic earths 

 when speaking of these substances as a whole, and not to use the 

 terms 'laterite' and 'lateritic earth' as equivalent and interchangeable. 



On p. 494 analyses are given of two pisolitic ' laterites ' which 

 evidently deceived Professor Harrison as much as the similar Indian 

 pisolitic lithomarge of which the analysis is given on p. 510 deceived 

 Maclaren and me ; for the analyses quoted show that instead of 

 obtaining rocks to correspond to Du Bois' pisolitic iron-ore and oolitic 

 bauxite as he intended, Harrison has collected merely a ferruginous 

 kaolin in one case, and a less impure kaolin or lithomarge in the other. 



The Laterite of Surinam. — On p. 558, Table XXIV, three technical 

 analyses of laterites from Surinam are quoted from Du Bois' 

 monograph. These show respectively 91 '4, 84*1, and 945 per cent 

 of hydrated oxides of alumina and iron, and two of them are nearly as 

 pure as some of the best Indian laterites. 



On the bottom of p. 558 Harrison refers, in the following words, to 

 the only laterite he has seen in Surinam : — 



"Here there is a gradual change of the decomposing schist into its laterite, 

 the change extending to considerable depths in the schist. The lateritic earth, 

 covered in places by concretionary masses of ironstone, reminded me of 

 Logan's account of the ferruginous and silico-ferruginous rocks and laterite 

 of Singapore . . . and of Mr. Scrivenor's description of the laterite of the 

 Malay Peninsula ..." 



Judging from the description this Surinam rock is not a residual 

 deposit, but a metasomatic replacement deposit, for which I have 

 offered the term lateritoid, which I have already remarked seems 

 applicable to Mr. Scrivenor's laterite. 



Professor Harrison is, however, only following Du Bois 1 in his wide 

 extension of the term laterite, for the latter in his paper on the laterite 

 of Surinam divides his laterites into — 



(1) Primary (Eluviale) laterite, or laterite rich in silica, and 



(2) Secondary (Alluviale) laterite from laterite detritus, or laterite 



rich in aluminium hydroxide. 



But Du Bois has also, I think, extended the term too widely, and 

 although some of the analyses given in his paper represent rocks that 

 can fairly be designated laterite, the remainder cannot, in my opinion, 

 be so classed ; for example, the decomposition products of diabase 

 given on p. 24 of Du Bois' paper, which are merely partially altered, 

 diabase. The analyses on p. 28 represent substances that contain 

 some 65 per cent of quartz and clay, and might be called lateritic sand 

 or earth, but might also be allowed the names alluvial or secondary 

 laterite, given to them by Du Bois. The analyses given on p. 37, 

 however, represent true laterites. These are the ones quoted by 

 Harrison. 



Prom the foregoing it will be seen that if one accepts the ideas as 

 to what is a true laterite put forward in this paper, it becomes 



1 Tschermak's Mittheilungen, 1903, p. 18. 



