REPORT ON THE DEEP-SEA DEPOSITS. 
387 
green casts, 60 per cent, of dark green casts, along with. 5 per cent, of mineral particles 
and siliceous organisms. The substance used for Analysis No. 87 contained 30 per cent, 
of white, pale grey, and yellow casts, 40 per cent, of pale green casts, 20 per cent, of dark 
green casts, together with 10 per cent, of mineral particles and siliceous organisms. The 
substance used for Analysis No. 88 contained about 10 per cent, of mineral particles 
similar to those mentioned in the description of the deposit (see p. 93), in spite of every 
care to obtain the red-coloured casts as pure as possible. 
Station. 
Depth 
in 
Fathoms. 
No. 
SiO^ 
ai ,03 
Fe20s 
FeO 
MnO 
CaO 
MgO 
K 2 O 
Na20 
H 2 O 
Total. 
164b 
410 
84 
56-62 
12-54 
15-63 
1-18 
trace 
1-69 
2-49 
2-52 
0-90 
6-84 
100-41 
164b 
410 
85 
50-85 
8-92 
24-40 
1-66 
trace 
1-26 
3-13 
4-21 
0-25 
5 55 
100-23 
164b 
410 
86 
51-80 
8-67 
24-21 
1-54 
trace 
1-27 
3-04 
3-86 
0-25 
5-68 
100-32 
164b 
410 
87 
55-17 
8-12 
21-59 
1-95 
trace 
1-34 
2-83 
3-36 
0-27 
5-76 
100-39 
185b 
155 
88 
27-74 
13-02 
39-93 
1-76 
trace 
1-19 
4-62 
0-95 
0-62 
10-85 
100-68 
While, then, there is a certain amount of agreement as to the chemical composition of 
glauconite, there is a wide divergence of opinion as to the immediate conditions which 
determine the formation of this mineral at the sea-bottom. Two principal opinions have 
been expressed.’- Before the time of Ehrenberg attention had not been called to the 
remarkable fact that the grains of glauconite sometimes carried the impress of the cal- 
careous organisms in whose cavities they were moulded. He concluded that this mineral 
was always formed through the activity of the creatures whose impress he had discovered.^ 
This opinion was disputed in 1860 by Reuss,^ who believed that the grains of glauconite 
might be concretions, not moulds, formed outside of the Foraminiferous and other shells, 
although he admits that some glauconitic grains are internal casts. 
From all that we have already stated in this chapter, it appears certain that glauconit^^ 
is principally developed in the interior of Foraminiferous shells and other calcareous 
structures, and that all the transitions can be observed from chambers filled with a 
yellowish brown mass to grains that have almost completely lost the impress of the 
organisms in which they were formed. From this fact, as well as from direct observations 
of the various constituents of the deposits, it is uncertain, and indeed little probable, that 
there are any minute grains of glauconite formed in a free state in the mud. We are 
therefore inclined to regard glauconite as having its initial formation in the cavities of 
calcareous organisms, although we have admitted above that some grains, which might be 
1 For the various hypotheses as to the mode of formation of glauconite see Giimhel, “ Uber die Natur und 
Bildungsweise des Glaukonits,” Sitzungsh. d. h. Akad. Munchen, Bd. xvi. Math. Phys. KL, pp. 417-449, 1886. 
^ Ehrenberg, “ Ueher den Griinsand und seine Erlauterung des organischen Lehens,” Ahh. d. k. Akad. Wiss. Berlin, 
1855, Phys. Ahh., pp. 85-176. 
^ Reuss, “Einige Bemerkungen liber den Griinsand,” Sitzungsb. d. k. Akad. TFiss. Wien, Bd. xl. Naturw. KL, pp. 
167-172, 1860. 
