192 Proceedings of the Royal Society of Edinburgh. [Sess. 
As regards the total analyses, Nos. 1 and 2 claim a moment’s attention. 
No. 1 is a typical Red Clay, quite free from calcium carbonate, in a deep 
basin of the North Atlantic; No. 2 was originally a Globigerina Ooze from 
a much higher level not many hundred miles distant ; the analysis refers 
to the siliceous matter remaining (about one-fourth of the whole) after the 
calcareous bulk had been removed by means of dilute acetic acid. It will 
be observed from the marked similarity between the two analyses that this 
siliceous matter is itself a characteristic Red Clay. Additional proof, if any 
such were needed, is thus afforded that the formation of Red Clay is a 
process independent of the biological activity which brings the Globigerina 
Ooze deposits into being. The percentage of lime in such an ooze gives the 
relative rates at which, at the locality concerned, calcareous shells and Red 
Clay (from floating pumice) reach the bottom. 
The elements which show the greatest absolute variation in these 
analyses are manganese and barium. Both are most abundant in the South 
Pacific and least in the North Atlantic. Manganese appears always to be 
present as peroxide : even the feebly manganiferous No. 1 evolves chlorine 
when heated with hydrochloric acid. In the more manganiferous Red 
Clays opaque specks of black oxide (mean diameter not exceeding 0005 mm.) 
can be observed under the microscope, and it seems probable that manganese 
exists in Red Clays in this independent form, though part of it may perhaps 
be an ingredient of the colloidal aggregates constituting the argillaceous 
portion. Certain it is that no other element is so readily detached from 
the Red Clay mass, either on the floor of the ocean ( e.g . by organic matter 
in decay) or in the laboratory {e.g. by dilute sulphurous acid). 
The experimental data at hand leave it undecided whether any im- 
portant proportion of the barium present belongs properly to the anhydrous 
residue.* Some of it, at any rate, is adsorbed by the hydrous silicates in 
the same way as magnesium and alkalies, since it can be partially extracted 
by ammonium chloride or nitrate solutions. The abundance of barium in 
South Pacific deposits is suggestive with regard to the proneness of this 
element to co-precipitate radioactive elements. Possibly the high activity 
found by Joly f in one of the Red Clays examined by him may thus be 
accounted for. Joly’s figures for activity in Red Clays, together with the 
barium-contents now determined, are as follows : — 
Radium. BaO. 
Challenger Station 5 (North Atlantic) . . 15'4x 10~ 12 0‘02 
„ „ 276 (South Pacific) . .52-6 „ 0-50 
* The volcanic glass from Challenger Station 302 (analysis, Challenger Rejwrts, “ Deep- 
Sea, Deposits,” p. 307) was tested and found to contain not a trace of barium. 
t Radioactivity and Geology , London, 1909, p. 50. 
