rch 3,
lat. 53 deg. 55' S., long. 108 deg. 35' E., the sounding instrument came up
filled with a very fine cream-coloured paste, which scarcely effervesced
with acid, and dried into a very light, impalpable, white powder. This,
when examined under the microscope, was found to consist almost entirely
of the frustules of Diatoms, some of them wonderfully perfect in all the
details of their ornament, and many of them broken up. The species of
Diatoms entering into this deposit have not yet been worked up, but they
appear to be referable chiefly to the genera _Fragillaria, Coscinodiscus,
Choetoceros, Asteromphalus_, and _Dictyocha_, with fragments of the
separated rods of a singular silicious organism, with which we were
unacquainted, and which made up a large proportion of the finer matter of
this deposit. Mixed with the Diatoms there were a few small
_Globigerinoe_, some of the tests and spicules of Radiolarians, and some
sand particles; but these foreign bodies were in too small proportion to
affect the formation as consisting practically of Diatoms alone. On the
4th of February, in lat. 52 deg., 29' S., long., 71 deg. 36" E., a little to the
north of the Heard Islands, the tow-net, dragging a few fathoms below the
surface, came up nearly filled with a pale yellow gelatinous mass. This
was found to consist entirely of Diatoms of the same species as those
found at the bottom. By far the most abundant was the little bundle of
silicious rods, fastened together loosely at one end, separating from one
another at the other end, and the whole bundle loosely twisted into a
spindle. The rods are hollow, and contain the characteristic endochrome
of the _Diatomaceoe_. Like the _Globigerina_ ooze, then, which it
succeeds to the southward in a band apparently of no great width, the
materials of this silicious deposit are derived entirely from the surface
and intermediate depths. It is somewhat singular that Diatoms did not
appear to be in such large numbers on the surface over the Diatom ooze as
they were a little further north. This may perhaps be accounted for by
our not having struck their belt of depth with the tow-net; or it is
possible that when we found it on the 11th of February the bottom deposit
was really shifted a little to the south by the warm current, the
excessively fine flocculent _debris_ of the Diatoms taking a certain time
to sink. The belt of Diatom ooze is certainly a little further to the
southward in long. 83 de