THE COMPOSITION OF THE RED CLAY 
F. W. CLARKE 
In the volume upon Deep Sea Deposits, issued as one of the 
reports of the ‘‘ Challenger” expedition, there are published twenty- 
five analyses of the “red clays.”* This sediment is now recognized 
as the most extensive and important of all oceanic deposits, for it covers 
51,500,000 square miles of the sea floor and is characteristic of the 
greatest depths. It is, therefore, obviously desirable to know its 
average composition as exactly as possible, and for that reason the 
following investigation was undertaken. 
Of the analyses above mentioned 21 were by Brazier, 2 by Hor- 
nung, 1 by Klement, and 1 by Renard. They are, however, not 
strictly comparable, as a glance at the recorded data will show, nor 
are they, from the point of view of the modern analyst, so complete 
as they should be. For example, that ubiquitous element, titanium, 
was not determined in any of the analyses, for at the time they were 
made, its importance and relative abundance were not appreciated. 
Other substances, which are common in clays, were neglected for 
similar reasons, but their significance is now better understood, and 
improvements in analytical methods have made it easier to search 
for them. In Brazier’s analyses the alkalies were not estimated, but 
were teported by the other analysts; an omission in the first group 
that was not due to oversight, but to the limitations of the purposes 
for which the work was done. The general nature of the red clay 
was well established, its great variability in composition was clearly 
shown, and its relations to other clays were made sufficiently plain 
to satisfy all ordinary requirements. 
Of late years, however, it has become a matter of interest to deter- 
mine the relative abundance and distribution of the chemical ele- 
ments; and in an inquiry of that sort so notable a substance as the 
red clay could not well be neglected. A new and more elaborate 
t Deep Sea Deposits, pp. 198, 201, 425-35. 
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