786 F. W. CLARKE 
lithium and fluorine is noteworthy. The unusually high proportion 
of manganese suggests the presence of disseminated or incipient 
manganese nodules, like that so admirably analyzed by Gibson.? 
In his work several of the rarer elements were determined; so 
that their existence in the oceanic sediments is no new discovery. 
The fact of their general distribution, however, remained to be 
proved. 
In order to establish the true composition of the clay substance, 
some deductions must be made from the analysis as it is now stated. 
Hygroscopic water and soluble matter must be eliminated, and also 
the calcium carbonate which is represented by the CO,. The com- 
position of the aqueous extract, as given by Mr. Steiger’s figures, 
is very near that of the sea salts. I have therefore taken Dittmar’s 
analysis of sea salts as a standard, and subtracted their equivalent, 
as measured by the chlorine in the unleached clay, from the analysis 
of the latter. A slight excess of SO, remained, which I have also 
thrown out as representing gypsum. In short, from the general 
analysis I have withdrawn the water lost below 106°, the sea salts, 
the calcium carbonate, and a little gypsum, and recalculated the 
remainder to roo per cent. 
For comparison, I have combined the twenty-five analyses of the 
“Challenger” report into an average, from which similar subtrac- 
tions, so far as they were needed, have been made. In this case 
only gypsum and calcium carbonate were rejectable. As for the 
combination, its value is not very great, because of the inequality 
shown by the individual analyses. Only in four of the latter were 
alkalies determined, and the mean of those four I have assumed 
to be representative of all. The ferrous oxide is even more doubtful, 
for it was only determined in one of Hornung’s analyses, and neglected 
in the others. Still, as will be seen in the subjoined table, the com- 
parison is not without significance, and even if it is not perfect, it is 
better than none at all. oes Eonar , 
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, 
t Deep Sea Deposits, pp. 422, 423. 
