The Sun.
London, England, 1858-11-08 00:00:00

THE VANGUARD ROCK.

PLYMOUTH, Saturday.—During the Russian war,
when the entrance to Sebastopol was interrupted
by sunken ships, several cylindrical powder maga-
zines, the invention of Mr. Armstrong, of New-
castle, were sent out, but not used, and one of these
has since been transferred by the War Department
to the Lords of the Admiralty. In consequence of
the successful operations for clearing the obstruc-
tions in New York harbour by simple blasting on
the rock, when the water alone became the ful-
crum, their lordships determined to use this maga-
zine in order to reduce the 'Vanguard Rock, which
has only about 18 feet over it at low tide, andwhich
lies nearly mid-channel between the Sound and Ha-
moaze. The magazine consisted of an outer cylin-
der, 14 feet long by 4 feet 6 inches diameter, and
an inner cylinder 10 feet long by 2 feet 8 inches
thus leaving a considerable air-chamber between
the two. -The lesser cylinder_ contained. more than
la ton of gunpowder, connected with which were
certain wires intended to convey ignition by the
aid of a galvanic battery. This mode having failed,
two Bickford's fuses were tried on Thursday, but
one of these burst only to within 11 feet, and the
other within four feet of the charge. As the mode
of ignition was not the special object in view, and
as the title was dropping fast and the winter ap-
proaching, it was determined yesterday to apply
six Bickford's fuses, selecting the best parts from
those sent, all of which had been a long time in
store. The arrangements were most complete. A
number of guardboats were placed at the point of
danger, and as the expected time approached they
diverged in a constantly-increasing circle, and en-
tirely prevented accident. The explosion occurred
exactly at the time named-17 minutes to 5 p.m.,
half an hour before high water. The magazine had
been placed in a concave hollow of the rock between
two hummocks, about 40 feet below the surface of
the sea. A palpable shaking of Stonehouse Point,
350 yards off, composed of solid limestone rock;
preceded the appearance of a pyramidical cone of
snow-white water, apparently in a boiling state.
The rise was variously estimated at from 50 to 70
feet, and the base 100 to 150 feet in diameter. It
was some seconds before this magnificent object
gradually subsided, when a circle of ten times the
size enclosed a turbulent sea, the darkness of which
gave conclusive evidence of the powerful effects of
the charge among the rocks and soil below, The
smoke from the explosion was entirely absorbed in
the water. An immense quantity of fish was sent
to the surface and easily caught. The operations
were under the directions of Capt. Jerningharn, of
her Majesty's gunnery-ship Cambridge, of this port,
and were carried out by Lieut. Dawson and a suffi-
cient staff of subordinate officers of that ship. Sir
William Harris, the inventor of the lightning con-
ductor, and Mr. Hearder, of Plymouth, [cave the
advantage of their experience to Capt. Jernmgham.
Over the Vanguard Rock there is constantly run-
ning a strong current, the velocity of which in-
creases as the spring tides advance. At times there
are two currents. the one below running in a direc-
tion contrary to that above. This condition of the
sea impedes the attempts of the diver who has been
down tc-day to examine the rock. He has, how-
ever, ascertained that the rock is considerably
shaken and split. Large pieces from 1 cwt. to 2
tons are lying near, and one portion of the cylinder
about 501 b. or 601 b., has been recovered. It will
be necessary to postpone a more complete survey
until the tides slacken.