664 
Proceedings of the Pioyal Society 
sieves, and the washings thus obtained consisted of sandy and 
calcareous Foraminifera, small Gasteropod and Lamellibranch shells, 
a few fragments of Pteropod shells, worm-tubes, sponge spicules, 
a few Radiolaria, and grains of quartz. 
When the mud itself is passed between the finger and thumb 
small hard particles are felt. 
Chemical analysis gave the following : — ■ 
From Station 4. Sounding tube. 555 fathoms. 
Microscopically examined, the carbonate of calcium appears to make 
up fully one-half of the deposit in bulk, and consists almost entirely 
of the dead shells of Globigerina, Pulvinulina, and Orbulina, along 
with Coccoliths and Coccospheres, which have fallen from the surface 
to the bottom. Many other genera of Foraminifera, as Textularia, 
Uvigerina, Nonionina, Truncatulina, Hodosaria, &c., together with 
fragments of Polyzoa, Echinoderms, Gasteropods, Lamellibranchs, 
Pteropods, and Cypridina valves were observed, but these do not 
seem to make up more than 2 per cent, of the total quantity of 
carbonate of lime in the deposit. 
The insoluble residue is essentially composed of grains of quartz, 
often covered with hydrate of iron, and having a diameter of ‘5 mm., 
associated with these are many black particles, which may be 
extracted by the magnet and are magnetic iron, while others are 
particles of mica and hornblende. 
There are numerous glauconitic casts of Foraminifera and other 
organisms of a yellow and greenish tinge ; radiolarians and sponge 
spicules are also present. 
When the deposit is hardened and made into thin microscopic 
slides, it can be observed that the quartz is of clastic origin, and 
generally rounded or of an irregular shape, the black mineral particles 
are seen to be transparent, green, clicroscopic, and formed of biotite. 
The magnetic iron and hornblende particles are much less abundant 
than the mica, one rarely sees the cleavage characteristic of horn- 
blende; some small particles of a blue colour, very dicroscopic, might 
Insoluble in HC1, . 
69*43 
1*17 
28*96 
99*56 
