171 
1906-7.] The Composition of the Red Clay. 
The minor elements, not shown in the Challenger analyses, only sum up 
altogether to 1*36 per cent. Apart from these, the comparison is satisfactory 
in some respects, not so in others. In silica, alumina, and water the 
agreement is fairly good, but in iron the old analyses range much higher 
than the new. Possibly for the individual analyses the reddest, and 
therefore the most ferruginous, samples were chosen for examination, as 
being presumably the most typical. 
On the proximate or mineralogical composition of the red clay I have 
no important suggestions to offer. That problem was discussed at some 
length in the Challenger report, on the basis of Brazier’s analyses. In 
those analyses there was discrimination between the portion of the clay 
soluble in strong hydrochloric acid, and the portion insoluble. In nearly 
every case the soluble ferric oxide was reported in excess of the insoluble ; 
from which I am inclined to suspect that the iron of the clay is present, at 
least partially, in limonitic or glauconitic combination. The new composite 
analysis shows a quantity of potash which suggests the presence of 
glauconite. The latter compound may well exist in a diffused form, quite 
unlike its common granular variety, and therefore not so readily recognised. 
This is a mere suspicion, not entitled to much weight at present, but worth 
considering in future investigations. My specific problem has been to 
study the distribution of the chemical elements in nature, and to that 
end the composite analysis of the red clay is a step forward. 
{Issued separately July 19, 1907.) 
