264 J. Murray on Sea-bottom Deposits. 
4, Diatomaceous Ooze.—South of the latitude of the Crozets, 
on our southern trip, we found Diatoms abundant, both in the 
surface waters and in the bottom. 
bout the Crozets, Kerguelen, M’Donald’s Islands, and close 
to the ice-barrier, the frustules of these organisms were ¥ 
abundant in the soundings, but were masked by much land- 
débris. Between the parallels of 53° and 63° S., 1. e., betw 
the north edge of the ice and the latitude of M’Donald’s Islands, 
we got in three soundings a pale straw-colored deposit, com- 
posed principally of the frustules of Diatoms and their broken- 
down parts. In addition, they contained a good many Radio- 
larian remains, a few specimens of one small species of Globr- 
gerina, a few particles of mica, quartz, and granitic pebbles, also 
a little amorphous blue clayey matter. No manganese particles 
were noticed. The one of these soundings which is nearest to 
e ice contains much amorphous clayey matter and larger 
mineral particles than the other two. When dried this deposit 
is of a white color, and is very light. 
The depths of the soundings referred to above are 1260, 1975, 
and 1950 fathoms. 
fathoms. The red and chocolate-colors of many of het 
are due to the presence of oxide of iron in the first and oxide ze 
manganese in the latter instance. ost of them contain som 
carbonate of lime in the form of Globigerina shells; in call 
not amorphous in the sense in which a chemical precip ee 
3 co 
the microsco They contain amorphous matter, tof 
but it is doubtful if this . erry 
any samplein bulk. They also contain larger mineral 
as quartz, mica, pumice, scoria, peroxide of manganese, to 
other mineral particles. Quartz and mica_particles ne and 
be present only in some localities, as the North Atlanh t 
elsewhere. Peroxide of manganese is perhaps alway re some 
in the form of grains or nodules, sparingly distributed 1 
ei 
