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Published online by Cambridge University Press: 01 May 2009
On approaching the problem of the origin of laterite, the first thought that strikes one is that there is an apparently fundamental difference between the modes of decomposition of aluminous silicates in temperate and in tropical regions. For in temperate regions the end product is a clay, in which the original aluminous silicates are represented by hydrated aluminium silicates approximating in composition to kaolinite, whilst in the tropics the end product is laterite, in which the original aluminous silicate is represented by a mixture of hydrated aluminium oxides. The two processes may be expressed by the following chemical equations:—
page 126 note 1 Trans. Inst. Min. Met., xix, p. 454, 1910Google Scholar.
page 126 note 2 Geol. Mag., 1903, pp. 61–4Google Scholar.
page 127 note 1 “The Occurrence of Aluminium Hydrates in Clays”: Economic Geology, ix, pp. 112–21, 1914Google Scholar.
page 127 note 2 See also Ries, H., op. cit., p. 402, 1914, for criticisms of Edwards’ paperGoogle Scholar.
page 128 note 1 See Meigen, , Geol. Rundschau, ii, pp. 197–207, 1911, for a recent though incomplete résumé of theories of lateritizationCrossRefGoogle Scholar.
page 128 note 2 This first proposition is, however, not self-evident.
page 128 note 3 Fühling's Landw. Zeitung, lix, p. 873, 1910 (Lacroix)Google Scholar.
page 128 note 4 Geol. Mag., p. 546, 1906Google Scholar. In his contribution to the discussion of Campbell, J. M.’s paper, Trans. Inst. Min. Met., xix, p. 414, 1911Google Scholar, Maclaren states that while he regards an alternation of wet and dry seasons as essential in humid regions, nevertheless a truer statement may be given, as follows: “Laterization may take place in intra-tropical regions in a desiccated zone overlying a zone charged with oxidized waters, capillary attraction translating the waters from the lower to the upper zone.” “The upper zone, in humid regions with heavy monsoon rainfall, where the ground water level is near the surface, may be at the surface; in more arid regions it may be as much as three feet below.” This modification is to account for the laterite in arid parts of Western Australia, believed by Maclaren still to be growing. This condition, namely, alternation of wet and dry seasons, does not, however, fit all known cases. Thus, as shown by Scrivenor, there is no alternation of seasons at Malacca; but it has yet to be shown that the laterite of Malacca is still in process of formation, or at least that its formation was not initiated under different climatic conditions. For the present, however, it is necessary to admit the formation of laterite in regions of constant rainfall.