242 
TIIE VOYAGE OF H.M.S. CHALLENGER. 
The fine washings vary from 15 ‘3 7 to 6070 per cent., the average being 36 ’87 
per cent. 
The following table shows the average percentages of minerals and fine washings and 
the average size of the mineral particles, arranged in groups of 500 fathoms, and it will 
be observed that there is no definite relation between the size and abundance of either 
of these and the depth ; — 
Minerals. Size. 
Under 
500 
fathoms. 
42*00 per cent. 
0*126 
mm, 
From 
500 to 1000 
99 
27*22 
0*09 
99 
J9 
1000 „ 1500 
99 
55*00 
0*11 
99 
99 
1500 „ 2000 
99 
28*33 
0*09 
9 9 
99 
2000 „ 2500 
99 
45*00 
0*20 
99 
Over 
2500 
9 9 
57*00 
0*125 
99 
Fine Washings. 
31*51 per cent. 
45-07 „ 
23*49 „ 
38*70 „ 
52*00 „ 
40*00 „ 
The following table shows the average 
Volcanic Mud : — 
composition of the 
Challenger samples of 
Carbonate of lime, 
Residue, 
Pelagic Foraminifera, . 
Bottom-living Foraminifera, 
Other organisms, . 
Siliceous organisms. 
Minerals, 
Fine washings. 
10-50 
2-82 
7*17 
20-49 
1-82 
40-82 
36-87 
79-51 
100-00 
Volcanic Sands . — Within depths of 500 fathoms there are in the Tables of Chapter II. 
7 samples which are called Volcanic Sands. These sands are found in positions where the 
particles making up the deposit are set in motion by the action of waves and currents, so 
that the finer materials are carried away into deeper or stiller water. It thus arises that 
these sands differ from the Volcanic Muds chiefly in the absence of the fine clayey and 
calcareous matter so abundant in the muds. The seven samples above referred to range from 
100 to 420 fathoms, the average depth being 243 fathoms. The percentage of carbonate 
of lime in these samples ranges from 6*93 to 71*65, the average being 28*79. Of this 
carbonate of lime the proportion due to the presence of the shells of pelagic Foraminifera 
is estimated to range from 2 to 50 per cent., the average being 13 per cent. ; that 
derived from the shells of Ijottom-living Foraminifera ranges from 1 to 5 per cent., and 
averages 3*80 per cent.; that due to the presence of other organisms varies from 2*93 to 
16*65 per cent., the average being 11*99. 
The residue of these sands is black or brown in colour, and makes up from 28*35 to 
93 07 per cent, of the whole of the deposit, the average being 71*21 per cent. 
