784 F. W. CLARKE 
analysis of it, therefore, seemed to be required, and to that end two 
methods of investigation were available. First, it was possible to 
make a number of individual analyses of separate samples, from 
which an average might be computed. Secondly, one composite 
sample could be analyzed, giving the desired information once for 
all. The first method, evidently, would have involved much labor, 
too much, indeed, to be justifiable. The second method would 
solve the problem equally well, but with greater ease and vastly less 
expenditure of time. The second, therefore, was chosen. ‘Through 
the kindness of Sir John Murray, and his secretary, Mr. James 
Chumley, fifty-one samples of the red clay, from as many localities, and 
approximately equal in weight, were combined into a single sample, 
and that was analyzed by my associates in the laboratory of the 
United States Geological Survey.t The results of the composite 
analysis will be given presently. 
The composite sample, as made up by Mr. Chumley, contained 
35 samples from the dredgings of the Challenger expedition, 12 col- 
lected by the “ Egeria,” 2 by the “ Waterwitch,” and 2 by the “ Pen- 
guin.” Of these, 8 samples were collected in the Atlantic, 2 in the 
Indian Ocean, and a1 in the Pacific. The “Challenger’’ localities 
were stations Nos. 5,9, 26, 27, 29, 160, 165, 181, 215, 221, 226, 228, 220, 
239; 238, 240, 241, 244, 247, 251, 253, 254, 255, 250, 258, 259, 275; 
277, 285, 286, 288, 294, 329, 330, and 353. ‘These stations can be 
identified by reference to the published reports of the expedition.? 
The geographic range of the collection is evidently large enough to 
give a significant average, and the number of individual samples was 
also adequate. ‘Twelve of the localities enumerated above are repre- 
sented among the analyses already published in the volume on Deep 
Sea Deposits and are there indicated by their station numbers. The 
other localities furnished material hitherto unstudied chemically. 
The new analysis of the clay was made upon the air-dried and 
unwashed sample. It, therefore, included adherent sea salts, and 
hygroscopic moisture, varying in these respects from the earlier 
t The analytical methods employed were those prescribed by Hillebrand, in 
U. S. G. S. Bulletin, No. 305. 
2 A chart showing the position at which each sample was taken, was also furnished 
with the material sent for analysis. 
