246 
THE VOYAGE OF H.M.S. CHALLENGER. 
Carbonate of lime, 
Residue, 
Pelagic Foraminifera, . 
■ Bottom-living Foraminifera, 
Other organisms, . 
Siliceous organisms, 
- Minerals, 
Fine washings. 
31-27 
14-64 
39-62 
85-53 
1-36 
1-00 
12-11 
14-47 
100-00 
Coral Sands . — In addition to the Coral Muds, there are 5 samples that are called 
Coral Sands in the Tables of Chapter II. These scarcely differ from the Coral Muds in 
composition except in the fact that the more finely divided calcareous matter is less 
abundant than in the Coral Muds, and the fragments of calcareous organisms are on the 
whole larger. These sands are indeed met with in positions where we have reason to 
believe that the particles composing the deposit are frequently set in motion by the 
action of waves or currents, being found in depths of less than 300 fathoms, the average 
depth of the above samples being 176 fathoms. Their colour is white or dirty white. 
The average percentage of carbonate of lime in the samples is 8 6 ‘8 4. The carbonate 
of lime derived from pelagic Foraminifera averages 36'25 per cent., from bottom-living 
Foraminifera 20 per cent., and from tlie remains of other organisms 30 "59 per cent. 
The siliceous organisms and mineral particles are more abundant than in the Coral 
Muds, but on the other hand the proportion of fine washings in the residue is much less. 
The following shows the average composition of the Challenger samples of Coral 
Sand : — 
Pelagic Foraminifera, . 
. 36-25 
Carbonate of lime, 
Bottom-living Foraminifera, . 
. 20-00 
Other organisms, . 
. 30-59 
86-84 
Siliceous organisms, 
5-00 
Residue, . . . ■ 
Minerals, .... 
3-75 
Fine washings. 
4-41 
13-16 
100-00 
The following analysis of a Coral Sand from Station 172, 18 fathoms, off Tongatabu, 
shows the usual compo.sition : — 
d 
o 
3 
n 
s 
5^ 
No. 
CaO 
MgO 
AlA 
FcA 
PaO(j 
o 
o 
Organic 
Su1)stancc. 
Mn 
Alkalies. 
SiOg 
Total. 
172 
18 
71 
60-27 
3 00 
1-42 
42-28 
2-78 
tr. 
tr. 
tr. 
99-75 
Tliis analysis shows that the chemical composition corresponds in a general manner 
with what has been said of the nature of this deposit from a macroscopic and micro- 
