1909-10.] Composition and Character of Oceanic Red Clay. 195 
But the irregular ratios are not to be accounted for by a mixture of definite 
chemical individuals, unless the presence of very finely divided kaolinite, for 
which there is no direct evidence, be assumed ; rather is it probable that 
definite chemical compounds, in the strict sense, are altogether absent. It 
will be observed that the argillaceous portion of Red Clay is considerably 
more acid than terrestrial clays, for which, if the analytical data available 
are to be trusted, the ratio 
A1 2 0 3 : Si0 2 = 1 : 2 
is understood to hold good. 
Under the microscope the characteristic portion of Red Clay is seen to 
consist of transparent isotropic rounded particles, mean diameter about 0001 
mm., of which the majority are colourless, whilst others, doubtless owing to 
the presence of iron, are more or less deeply brownish-yellow. With the 
exception of crystalline and vitreous fragments not coated with decomposed 
matter, and of opaque manganese specks, all the particles are readily stained 
by a dye such as methylene blue ; that is, they are of colloidal habit. On 
extraction with dilute acid and alkali alternately (the specimen experimented 
upon was No. 4) the successive extracts contain silica and sesquioxides in 
gradually varying non-stoichiometrical proportions, like the soils and clays 
studied by Van Bemmelen,* and the amounts extracted vary greatly with 
the concentration, temperature, etc., of the solvent. Chemically well-defined 
silicates, therefore, appear to be absent. 
Hydrochloric acid alone, even at boiling temperature, is unable to 
dissolve the whole of the clay-substance. In this respect one Red Clay is 
apt to differ from another : that from the South Pacific, for instance, yields 
more readily to acid attack than that from the North Atlantic.^ 
As to the iron in Red Clay, there is no warrant for supposing it to 
be present in a distinct form, as limonite. If the ferric hydroxide existed 
independently it would tend, under the influence of salt-water and deep-sea 
pressure, to become anhydrous and crystalline, J and would be found as 
crystals of hematite, like those occurring, e.g., in carnallite. As it is, the iron 
behaves altogether as if it formed part of the argillaceous agglutinate. At 
the same time, it is undoubtedly more loosely bound than alumina, since it 
is more easily extracted by acids ; and, as the microscope shows, it appears 
to be not quite regularly distributed in the clay particles. 
Turning now to the molecular constitution of submarine clay, it seems 
difficult to hold other views than those arrived at by Van Bemmelen § with 
* Zeitschr. Anorg. Chem ., xlii. 265-324, 1904. 
t Caspari, Mem. Mus. Comp. Zodl., xxxviii. p. 169, 1909. 
J Wittstein, Vierteljahrsschr. f. Pharm ., i. p. 275 ; Spring, Neues Jahrb., 1899, p. 47. 
§ Loc. cit. 
