382 Correspondence—J. W. Evans. 
required a name. As bricks were made of it (not because it resembled 
a brick) he called it laterite, certainly without intending to include 
under it all materials of which bricks could be made. I admit that 
he did not know its true chemical composition, but in spite of that it 
must be accepted as the type of what we ought to call laterite. 
As a matter of fact the majority of geologists and of scientific 
mining engineers are now using the word in this sense, the sense 
which I and others are defending, and that this is so a recent 
discussion in the pages of the Transactions of the Institution of 
Mining and Metallurgy, in connexion with a paper by Mr. G. 
Morrow Campbell on the ‘‘ Origin of Laterite ’’, is sufficient evidence. 
As to the word ‘bauxite’ I have no objection to its being applied to 
a laterite exceptionally poor in silica and iron, and therefore suitable 
for use as a source of aluminium and its compounds, as long as it is 
understood that it is so employed as a commercial mineral term and 
not asarock name. Scientifically, however, it should be restri¢ted to 
a mineral, if such exist, in which two molecules of water are combined 
with one of alumina. 
We shall all look with interest for the results of Mr. Scrivenor’s 
investigation of the chemical nature of the products of tropical 
denudation—under whatever name or names he may describe them. 
Joun W. Evans. 
IMPERIAL INSTITUTE. 
July 1, 1910. 
LATERITE AND BAUXITE. 
Srr,—I am glad to learn from Mr, Crook’s letter in the May 
number of the Grotocicat Macaztne that I am not alone in holding 
certain views regarding the term laterite and also the term bauxite, 
but it is a pity that either side should be led into criticisms that are 
stronger than the occasion warrants. 
I can understand Mr. Crook’s surprise that anyone should decline 
to accept, without question, the new definition of laterite, seeing by 
what authority it is supported, and I grant that the proposed definition 
is attractive. But what, in my opinion, has been lost sight of, is 
that laterite was defined more than a hundred years ago, and that the 
extension of the term in tropical countries has been based on the early 
descriptions, the keynotes of which are brick andiron. When an 
innovation is proposed—for I must with all deference ask still to be 
allowed to consider this ‘aluminous’ definition an imnovation—the 
first question is whether it is practicable, the next whether it is 
necessary. I do not think the change practicable, because the ideas 
of brick and iron have taken firm root and have led to the term being 
widely used for ferruginous rocks, useful in public works and in ~ 
building. As its practicability is denied there is no question of its 
necessity ; but were the change practicable, would the new be better — 
than the old definition? The brick and iron characteristics are easily 
recognized; the aluminous is not. The word ‘laterite’ has no etymo- 
logical connexion with aluminium ; it has with brick, and so, indirectly, 
with iron, since the setting of laterite is dependent, mainly at any 
rate, on the presence of ferric hydroxide. Both Dr. Evans and 
