206 
THE VOYAGE OF H.M.S. CHALLENGEK. 
the average depth being 2894 fathoms, which is deeper than the average depth of the 
Red Clay samples, viz., 2730 fathoms. 
The carbonate of lime in these nine samples ranges from a trace in five cases to 20 per 
cent, in 2550 fathoms at Station 269, the average percentage being 4'01. This carbonate 
of lime is chiefiy made up of pelagic Foraminifera, but the shells of bottom-living species 
of Rotalidae and Nummulinidse are also present. Teeth of fish are mentioned in seven of 
the samples, and otoliths of fish, Ostracode shells, Echinoderm fragments, Gasteropod 
shells, and Coccoliths, occur, but never in great abundance. 
The residue after the removal of the carbonate of lime by dilute acid, which is red 
or red-brown, ranges from 80 to nearly 100 per cent, in the nine samples, the average 
l)eing 95’99 per cent. In this residue the remains of siliceous organisms are estimated 
to make up from 30 per cent, at Station 273 in 2350 fathoms to 80 per cent, at Station 
225 in 4475 fathoms. The remains of Radiolarians make up the principal part of these 
siliceous organisms, but Diatoms and Sponge spicules are also present, and among 
arenaceous Foraminifera, species of Lituolidse and Astrorhizidse can nearly always be 
observed. 
The mineral particles with a mean diameter of over 0‘02 mm. are all angular, and 
average O’l mm. in diameter. They make up from 1 per cent, of the deposit in most 
cases to 5 per cent, at Station 274 in 2750 fathoms, the mean percentage of mineral 
particles present in the nine samples being 1’67 of the whole deposit. 
The fine washings range from 17 per cent, in 4475 fathoms to 67 per cent, in 2350 
fathoms, the average being 39‘88. These fine washings are largely made up of the 
minute undeterminable fragments of siliceous organisms. 
The following table shows the average composition of the Challenger samples of 
Radiolarian Ooze : — 
1 
Pelagic Foraminifera, 
3-11 
Carbonate of Lime, . . < 
Bottom-living Foraminifera, 
Oil 
Other organisms. 
0-79 
Siliceous organisms, . 
. 54’44 
Residue, 
Minerals, 
1-67 
Fine Washings, .... 
. 39-88 
95-99 
10000 
When this average composition is compared with that of the Red Clay, it will be 
observed that the difference lies almost wholly in the large pereentage of the siliceous 
organisms present in the residue. 
The constitution of the Radiolarian Ooze as revealed by the above microscopic 
examination is confirmed by the two following analyses : — 
