REPORT ON THE DEEP-SEA DEPOSITS. 
245 
In colour the muds are of various shades of white, due to the large amount of 
carbonate of lime, which ranges from 77‘38 per cent, in 1500 fathoms to 89‘68 per cent, 
in 380 fathoms, the average being 8 5 ‘5 3 per cent. The following shows the average 
percentage of carbonate of lime at various depths, arranged in groups of 500 
fathoms, and it will be observed that there is little or no relation to depth ; — 
Under 500 fathoms, 
From 500 to 1000 ,, 
1000 „ 1500 
Over 1500 „ 
87 ’34 mean per cent. CaCOg 
89-36 
84-59 
82-78 
>5 
55 
The carbonate of lime derived from pelagic Foraminifera ranges from 10 to 56 per 
cent., and averages 31-27 per cent. ; that derived from bottom-living Foraminifera 
ranges from 2 to 40 per cent., the average being 14-64 per cent. ; that derived from 
other organisms varies from 26-31 to 59-68 per cent,, and the mean percentage is 
39-62. 
The residue is always of a brown or reddish colour, and varies from 10-32 to 22-62 
per cent,, the average being 14-47 per cent. This residue consists of clayey matter, 
oxides of iron, and mineral particles, generally of volcanic origin, together with a few 
siliceous organisms. 
Siliceous organisms do not make up more than 1 or 2 per cent, of the whole deposit, 
the average in the above samples being 1-36 per cent. Sponge spicules are always 
present, and Diatoms and Radiolaria can generally be recognised during the examination 
of a sample. 
The mineral particles are estimated in each of the above samples to make up 1 per 
cent. ; they are always angular, and have an average diameter of 0-07 mm. 
The fine washings vary from 8-32 to 20-62 per cent., the average being 12-11 per 
cent. 
Arranged in groups of 500 fathoms, the following table shows the estimated average 
amount of fine washings and minerals, and the mean diameter of the latter ; it will be 
noticed that no relation to depth is indicated except the greater abundance of fine wash- 
ings in deep water : — 
Minerals. 
Size. 
Fine Washings. 
Under 500 
fathoms. 
. 1 per cent. 
0-065 mm. 
9-96 per cent. 
From 500 to 1000 
55 
. 1 „ 
0-060 „ 
8-64 „ 
„ 1000 „ 1500 
55 
. 1 » 
0-077 „ 
13-41 „ 
Over 1500 
55 
. 1 » 
0-067 „ 
14-88 „ 
The following shows the average composition of the Challenger 
Mud 
samples of Coral 
