220 
THE VOYAGE OF H.M.S. CHALLENGER. 
of the Glohigerina shells present in these deposits. Take for example a sample with 
about the highest percentage of carbonate of lime, 91 ’32 (Station 302), where there is 0*30 
per cent, of carbonate of magnesia, while in that with the least carbonate of lime, 37‘51 
per cent. (Station 64), there is 1'13 per cent, of carbonate of magnesia. 
In examining the insoluble portion of the analyses, it will be seen that, generally 
speaking, this portion indicates that the mineral particles are relatively less numerous 
than in a Red Clay. In some samples, however, the percentage of silica indicates the 
presence of quartz and of silicates in some abundance. In all these respects the analyses 
confirm the macroscopic and microscopic examination in showing the presence of silicates, 
similar to those in other pelagic deposits, in the residue of a Glohigerina Ooze. This view 
is confirmed Ijy the following additional analysis of a Glohigerina Ooze from the Tropical 
Pacific, at Station 176, in 1450 fathoms : — 
Station. 
S T. 
'Z £ 
w 2 
No. 
SiOj 
AIjO, 
Fe-jOj 
MnOj 
CaO 
MgO 
KjO 
NaaO 
CO 2 
H.,0 
Cu 
Ni 
Co 
PA 
Total. 
176 
1450 
56 
17-71 
4-86 
6-80 
1-69 
35-08 
1-64 
0-32 
0-65 
29-10 
2-95 
tr. 
tr. 
tr. 
tr. 
100-80 
In comparing the figures in this analysis with those given in the previous table for a 
sample from the same station, there is a coincidence in most cases, but in some cases there 
are small divergences which cannot be accounted for by different methods of analysis, and 
this shows how samples from the same station may vary in composition. This remark is 
applicable also to the results indicated in the Tables of Chapter II,, which again are 
<lirtercnt from the results of this complete analysis. It will thus be seen that, notwith- 
standing the care taken in selecting a medium sample, we are in reality not dealing with 
a homogeneous substance ; this is true for all the deposits, as might be expected, and as 
we have already pointed out. However, the examination of the preceding analysis leads 
to the same general results as the others ; that is to say, the percentage of carbonate of lime 
is that of a Glohigerina Ooze. Along with the carbonate of lime organisms there is a 
residue composed of argillaceous matters united with hydrated silica, siliceous organisms, 
and anhydrous silicates containing alumina, iron, magnesia, and alkalies, referable to 
minerals and fragments of rocks of volcanic origin. 
In order to know as exactly as possible the nature of this mineral matter mixed with 
the remains of Glohujerinw, the residues of two samples of Glohigerina Ooze have been 
submitted to a detailed examination. The samples were in the first place boiled for a long 
time in distilled water to remove the soluble .salts. They were then treated with dilute acid 
• Tliir fart may be eaaily cxplniiiol : admitting that the carbonate of magnesia comes from the action of the 
milidiate of magnesia in tlie sea-water on the Glohiycrina shells, it will be seen that this action must he stronger on a 
given quautity of shcllii, when the rate of their dejKjsition is slow than when they arc abundant, and accumulate rapidly 
in the dej»o»it. It may, however, l>e urge<l that the carlwnate of magnesia has accumulated in the greater depths simply 
from the removal of the ciirlx>nate of lime in solution. 
