168 Proceedings of the Royal Society of Edinburgh. [Sess. 
of separate samples, from which an average might be computed. Secondly, 
one composite sample could be analysed, giving the desired information 
once for all. The first method, evidently, would have involved much labour 
— 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 assistants, Dr G. W. Lee and Mr James Chumley, 
fifty-one samples of the red clay, from as many localities, and approxi- 
mately equal in weight, were combined into a single sample, and that was 
analysed by my associates in the laboratory of the United States Geological 
Survey.* The results of the composite analysis will be given presently. 
The composite sample, as made up by Sir John Murray, contained thirty- 
five samples from the dredgings of the Challenger Expedition, twelve 
collected by the Egeria, two by the Waterwitch, and two by the 
Penguin. Of these, eight samples were collected in the Atlantic, two in 
the Indian Ocean, and forty-one in the Pacific. The Challenger localities 
were stations Nos. 5, 9, 26, 27, 29, 160, 165, 181, 215, 221, 226, 228, 229, 230, 
238, 240, 241, 244, 247, 251, 253, 254, 255, 256, 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.j- 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 represented 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 analyses. The magnitude of these 
variations, however, was determined, and appears in the figures given below. 
The final data are as follows : 
A. General analysis, by Mr George Steiger. 
B. Portion soluble in cold water, Steiger. 
C. Special determinations, by Dr W. F. Hillebrand. 
D. Special determinations, on material concentrated from 150 
grammes of clay, by Dr E. C. Sullivan. 
* The analytical methods employed were those prescribed by Hillebrand in U.S.G.S. 
Bulletin 305. 
t A chart showing the position at which each sample was taken was also furnished with 
the material sent for analysis. 
