able. Captain Vidal ascertained, by soundings made off Tory
Island, on the northwest coast of Ireland, that Crustacea, Star-fish,
and Testacea occurred at various depths between fifty and one hundred
fathoms; and he drew up Dentalia from the mud of Galway Bay, in 230 and
240 _fathoms_ water.

The same hydrographer discovered on the Rockhall Bank large quantities
of shells at depths varying from 45 to 190 fathoms. The shells were for
the most part pulverized, and evidently recent, as they retained their
colors. In the same region a bed of fish bones was observed extending
for two miles along the bottom of the sea in eighty and ninety fathoms
water. At the eastern extremity also of Rockhall Bank, fishbones were
met with, mingled with pieces of fresh shell, at the depth of 235
fathoms.

Analogous formations are in progress in the submarine tracts extending
from the Shetland Isles to the north of Ireland, wherever soundings can
be procured. A continuous deposit of sand and mud, replete with broken
and entire shells, Echini, &c., has been traced for upwards of twenty
miles to the eastward of the Faroe Islands, usually at the depth of from
forty to one hundred fathoms. In one part of this tract (lat. 61 degrees
50 minutes, long. 6 degrees 30 minutes) fish-bones occur in
extraordinary profusion, so that the lead cannot be drawn up without
some vertebrae being attached. This "bone bed," as it was called by our
surveyors, is three miles and a half in length, and forty-five fathoms
under water, and contains a few shells intermingled with the bones.

In the British seas, the shells and other organic remains lie in soft
mud or loose sand and gravel; whereas, in the bed of the Adriatic,
Donati found them frequently inclosed in stone of recent origin. This is
precisely the difference in character which we might have expected to
exist between the British marine formations now in progress and those of
the Adriatic; for calcareous and other mineral springs abound in the
Mediterranean and lands adjoining, while they are almost entirely
wanting in our own country. I have already adverted to the eight regions
of different depths in the AEgean Sea, each characterized by a peculiar
assemblage of shells, which have been described by Professor E. Forbes,
who explored them by dredging. (See above, p. 649.)

During his survey of the west coast of Africa, Captain Sir E. Belcher
found, by frequent soundings between the twenty-third and twentiet