1 
REPOE-T ON THE DEEP-SEA DEPOSITS. 
143 
RESIDUE. 
t. ' 
Siliceous Organisms. 
Minerals. 
Fine Washings. 
Additional Observations. 
I'OO %), a few Radiolaria, im- 
perfect casts of Foraminifera, 
AstrorMzidse, Lituolidse. 
(I'OO %), m. di. 0'06 mm., 
angular; sanidine, plagioclase, 
hornblende, mica, magnetite, 
glassy volcanic particles. 
'00 %), Sponge spicules, 
Radiolaria, Lituolidae, imper- 
fect casts of Foraminifera. 
(I'OO %), m. di. 0'06 mm., 
angular ; felspar, hornblende, 
grains and crystals of 
magnetite, glassy volcanic 
fragments, pumice, manga- 
nese grains. 
'00 %), Radiolaria, Lituolidae. 
. few large Radiolaria, frag- 
ments of Sponge spicules, 
&.strorhi 2 ids, LituoUdm. 
(I'OO %), m. di. O'lO mm., 
angular ; fragments of brown 
glassy volcanic rock with 
the conchoidal fracture of 
obsidian, sanidine, magnetite, 
vesicular felspathic lapilli, 
small particles of manganese. 
M. di. 0'06 mm., angular ; a few 
particles of felspar and mag- 
netite. 
(12'79 %), amorphous matter, 
many fine mineral particles, a 
few fragments of siliceous 
organisms. 
(4 '23 %), amorphous matter, 
many fine mineral particles, 
some fragments of siliceous 
spicules. 
(18 '98 %), flocculent amorphous 
matter, with minute fragments 
of minerals, manganese, and 
Radiolaria. 
Traces of flocculent matter. 
The sounding tube had sunk about a foot (30 cm.) into 
the bottom and brought up a litre of the deposit. Of 
this there were two layers separated by a thin dark 
line, an upper layer of a light brown colour and about 
8 inches (20 cm.) in thickness, composed essentially 
of the shells of pelagic Foraminifera, and a lower, milk 
white and over an inch (25 mm. ) in thickness, chiefly 
made up of amorphous calcareous matter and Cocco- 
liths. On analysis the upper layer gave 84'65 percent, 
of carbonate of lime, the lower 85'77 per cent. The 
annexed analysis is the mean of these two results. 
The passage between the two layers appeared to be 
quite abrupt, so far as could be judged from a careful 
examination of the contents of the sounding tube. The 
tow-nets at the weights and at the trawl contained a 
little of the ooze, which was the same as the upper 
layer above described. A fragment of the hardened 
deposit about 1 cm. in diameter was taken from the 
washings from the trawl. 
The sounding tube had not apparently sunk far into the 
bottom as there were no traces of mud or ooze on the 
outside, and in the inside only about half a pint (0 '3 
litre) of the ooze. In the dredge and attached tow-nets 
there were about 10 litres of the ooze and three pieces 
of pumice, measuring fully an inch (25 mm.) in dia- 
meter, and more or less rounded. They are white and 
scoriaceous, although the pores are generally small and 
contain only a few porphyritic minerals, felspar and 
augite. These porphyritic minerals in many instances 
project above the rounded smooth surface of the 
pumice. Some of the shells of the arenaceous Fora- 
minifera are formed of agglomerations of microliths 
of hornblende, little fragments of felspar and mag- 
netite, and of vitreous particles. Many of the shells of 
the pelagic Molluscs are black and brown from a coat- 
ing of manganese, and are macroscopic. A Pteropod 
Ooze, it must be remembered, only indicates a relative 
abundance and not a predominance of these shells in 
the deposit. 
The sounding tube brought up only a small quantity of 
the deposit. The splinters of volcanic rook are some- 
times 0 '5 mm. in diameter, and make up almost the 
whole of the mineral particles in the deposit. Note 
the absence of Pteropod and Heteropod shells in this 
deposit. 
The sounding tube brought up about half a pint (0 '3 litre) 
of the deposit, which contains very little amorphous 
calcareous or clayey matter, and is chiefly composed of 
the shells of pelagic Molluscs and Foraminifera. Many 
of the shells are fully 1 cm. in length, some of them 
black or brown with a thin coating of manganese, some 
transparent. The tow-nets had not been at the bottom, 
and the dredge seemed just to have touched. This is 
the shallowest depth far removed from land of any 
kind met with during the cruise. 
Rio de la Plata to Tristan da Cunha — continued. Tristan da Cunha to Ascension Island. 
