EEPORT ON THE DEEP-SEA DEPOSITS. 
211 
carbonate of lime is due to the presence of the dead shells of pelagic Foraminifera, the 
other carbonate of lime organisms present not making up more than 3 or 4 per cent, of 
the whole deposit in any case. 
The mineral particles vary greatly in nature, size, and abundance in the Diatom Oozes, 
sometimes volcanic rocks and minerals, sometimes those of ancient and sedimentary 
formations predominating. This was to be expected, for all the Challenger samples of 
this deposit lie within the region of floating ice in the southern hemisphere. The 
minerals range from 3 per cent, in 1950 fathoms to 25 per cent, in 600 fathoms, the 
average being 15 '6 per cent. The mean diameter is 0*12 mm., but rocks and minerals 
from the Antarctic Continent and islands are found of all dimensions, and are spread 
over the whole region from their source in the shallow water near the Ice Barrier to 
north of the latitude of 40° south, for they were dredged in considerable numbers by 
the Challenger in all the Diatom ooze areas. These consist of fragments of granite, 
granitite, chloritic sandstone, micaceous sandstone, amphibolite, gneiss, schists and slates, 
and other ancient and recent volcanic rocks. 
The fine washings range from 12’53 in 1260 fathoms to 27'92 in 1975 fathoms, the 
average being 20*44 per cent. 
The average composition of the five samples of Diatom Ooze is as follows ; — 
Pelagic Foraminifera, 
. 18-21 
Carbonate of Lime, . . - 
Bottom-living Foraminifera, 
1-60 
Other organisms. 
3-15 
22-96 
Siliceous organisms, . 
. 41-00 
Residue, 
Minerals, ..... 
. 15-60 
Fine Washings, .... 
. 20-44 
77-04 
100-00 
The Challenger’s trawlings revealed the presence of a large number of deep-sea animals 
living at the bottom in the Diatom ooze areas; at Station 157, 1950 fathoms, a single 
haul of the trawl procured over 150 specimens belonging to 77 species and 68 genera. 
The following is an analysis of an average sample of the deposit from Station 157, 
1950 fathoms : — 
Portion soluble in HCl. 
Portion insoluble 
IN HCl. 
station. 
Depth in 
Fathoms. 
No. 
Loss on 
Ignition. 
SiOa 
AI2O3 
F 6203 
MnOj 
CaC 03 
CaS 04 
Ca 32 P 04 
MgC 03 
Total. 
SiOs 
AI2O3 
Fe 203 
157 
1950 
31 
5-30 
67-92 
0-55 
0-39 
19-29 
0-29 
0-41 
1-13 
89-98 
4-72 
