EEPORT ON THE DEEP-SEA DEPOSITS. 
235 
The mineral particles range from 10 to 25 per cent., the average being 21 T1 per 
cent. The particles are rounded and angular ; in size they vary from 0 '07 to 0*30 mm. in 
diameter, the average being 0'15 mm. Quartz is the most abundant mineral, and the 
other minerals are similar to those found in the other terrigenous deposits along con- 
tinental shores. 
The fine washings range from 28‘21 to 68‘25 per cent., the average being 45‘61 
per cent. 
By arranging the amount of minerals, their size, and the fine washings according 
to depth, it is seen that the mineral particles are larger and the amount of fine washings 
less in the shallower depths. 
Minerals. 
Size. 
Fine Washings. 
Under 500 fathoms, . 20 per cent. 
0‘30 mm. 
33 "37 per cent. 
500-1000 
,, . 20 ,, 
0T26 „ 
49-04 
Over 1000 
jj • 25 ,, 
0-075 „ 
49-24 
The following table shows the average composition of the Challenger samples of Red 
Mud : — 
( Pelagic Foraminifera, .... 13 '44 
Carbonate of lime, \ 
1 
Bottom-living Foraminifera, 
[ Other organisms, . 
r Siliceous organisms. 
. 
3-33 
15-51 
32-28 
1-00 
Residue, . . < 
Minerals, . 
[ Fine washings, 
. 
21-11 
45-61 
67-72 
10000 
The following analysis was made to determine the chemical composition of a Bed 
Mud, from Station 120, 675 fathoms: — 
g 1 station. 
° 1 
Deptli in 
Fathoms. 
No. 
Loss on 
Ignition. 
SiOa 
AI2O3 
Fe^Oa 
CaO 
MgO 
NaaO 
K 2 O 
SO 3 
CO, 
Cl. 
Total. 
675 
54 
6-02 
31-66 
9-21 
4-52 
25-68 
2-07 
1-63 
1-33 
0-27 
17-13 
2-46 
101-98 
In combining the carbonic acid with the oxide of calcium indicated by the analysis 
we obtain 38 '93 per cent, of carbonate of calcium, with an excess of oxide of calcium, 
which may come from the silicates containing lime, or from the phosphate and sulphate 
of lime. There must be, according to the analysis, a relatively large quantity of argillaceous 
matter and hydrated peroxide of iron in the deposit, and free silica in the form of quartz 
or hydrated silica from organic remains. The presence of alkalies indicates that alkaline 
silicates are among the minerals, as indeed was shown by microscopic analysis, but a good 
