440 Professor J. B. Harrison—‘ Laterite’ in British Guiana. 
of alumina. I drew attention to this in a report on the soils of the 
interior of British Guiana published in 1902 in the following words: 
‘A very large proportion of the alumina present is in the form of the 
hydrate, bauxite.” As in the work on the Geology of the Gold 
Fields I was not dealing with the question of the presence of free 
alumina in the decomposition products of igneous rocks, but with the 
movements, the segregation, and the concentration into grains of the 
gold originally disseminated in certain of them, I contented myself by 
giving a reference to the full account and discussion of the Guiana 
laterites in Dr. G. C. Du Bois’ monograph ‘ Beitrag zur Kenntnis der 
Surinamischen Laterit”’, which was published in 1903 in Zschermak’s 
Mineralogische und Petrographische Mitteilungen. A reference to this 
work would have shown that aluminous masses occur in the laterites 
of the Guianas and in Surinam, more especially in the re-arranged 
detrital deposits classed by Du Bois as ‘alluviale laterite”’. 
Unfortunately a reviewer of the work in the Imperial Institute 
Bulletin, vol. vu, No. 1, 1909, did not realize my object in thus referring 
to Du Bois’ monograph, and therefore made unfavourable comments 
on my use of the term ‘laterite’, which term he stated ‘‘should be 
restricted to that product of weathering in hot moist climates which 
contains free aluminium hydroxide ”’. 
His comments have given rise to the recent correspondence between 
Mr. J. B. Secrivenor and Mr. T. Crook, in which the latter writes 
somewhat scathingly of ‘‘some people”, amongst whom I am not 
ashamed to be included, who use the term laterite in the wide sense 
it is at present very largely employed by technical geologists, mining 
engineers, and tropical agriculturists. But in my opinion Mr. Crook 
is too severe in his strictures, strictures which appear to be based on 
a somewhat restricted view of the nature of the deposits in question, 
on the assumption that they mainly consist of masses of hydrated 
alumina—bauxite, gibbsite, or diaspore, or mixtures of them—which 
actually occur only in places in laterite; and I am quite unable to 
agree with him that the application of the term to such clays, iron- 
ores, etc., as I used it for is ‘‘ wholly unwarranted ”’, and that my use 
of the term is “‘ unscientific’? and one that ‘‘ cannot properly be 
adopted by geologists”. The British Guiana deposits are ‘‘ a complex 
product .. . characterized by the presence of hydrated alumina, but 
usually containing also notable amounts of titanium and iron oxides, 
whilst free silica is generally present and hydrate of silicate of alumina 
is not necessarily absent”, and the following account of these deposits 
formed by the decomposition of igneous rocks in situ and in some of 
which in parts hydrated alumina occurs may be of interest. 
As far as my experience goes, the presence of free alumina in 
quantity in the residual earths resulting from the decomposition of 
igneous rocks in British Guiana characterizes rocks the felspars of 
which are mainly of the albite-anorthite series, whilst the residual 
deposits from rocks in which alkali-felspars such as orthoclase, 
anorthoclase, microcline, and albite are predominant, consist largely of 
kaolinite or of sericitic micas with kaolinite. 
The general compositions of the soils found in aluminous lateritic 
areas are shown in the following analyses :— 
— ~~. 
