The Sun.
London, England, 1859-07-28 00:00:00

THAMES GRAVING DOCK COMPANY.

A large company connected with the commercial
and scientific world assembled yesterday at the
Victoria Docks, to witness an experiment carried
out under the auspices of the Thames Graving Dock
Company for testing the efficacy of Mr. Edwin
Clark's patent process of raising ships for the pur-
pose of examination and repair by hydraulic pres-
sure. Under the old plan of graving, careening, or
repairing docks it was necessary to excavate each
dock to a depth sufficient to float the largest ship
intended to be repaired, and to construct at the
entrance of each dock a flood gate, or pair of gates,
to keep the water out. For ships of the size now
in common use the depth of a repairing dock must
be about 24 feet, causing a heavy expense for exca-
vation and retaining walls of masonry, indepen-
dently of the cost of the tidal gates. An entry into
docks of this construction is effected at, or soon be-
fore, or after, high water. The gsite is then closed,
and at lower water, on a .tidal sea, the water is
allowed to run out until the ship is left dry for exa-
mination or repair in a sort of pit, always damp, and,
in winter, soon dark. In tideless seas a graving
dock must be emptied by the slow and expensive
process of pumping. The new process obviates
these difficulties and delays. A floating stage or
pontoon is placed in a basin or water-way, and the
vessel requiring examination or repair is floated
upon it, and by the application of hydraulic pumps
the stage, with the vessel upon it, is raised, and be-
comes a working platform, upon which the vessel,
lifted up high and dry as in a dry dock, may be
caulked or coppered or repaired as her necessities
may require. The hydraulic lift consists of two
parallel rows of 16 cast-iron columns, each 5 feet in
diameter, and 60 feet in length, sunk into the ground,
under the water, about 12 feet. These columns are
20 feet apart in each row, and the clear space be-
tween the two rows is 60 feet. Each column con-
tains a hydraulic press 10 inches in diameter, and
of 25 feet stroke, the top of the press being at the
ordinary level of the water. The ram of each press
carries a small cross-head, from which are suspended,
by means of descending rods two wrought-iron
girders 60 feet in length, which extend entirely
across the dock to the corresponding column and
press on the opposite side. There is thus a series
of 32 suspended girders extending entirely across
the dock ; and when the presses are lowered, lying
at the bottom of the dock in 28 feet of water, these
form a large wrought-iron gridiron, which by means
of the presses may, with a vessel upon it, be raised
out of the water or lowered at pleasure. The vessel
to be docked is not raised directly upon the grid-
iron, but upon a wrought-iron pontoon, propor-
tioned to the size of the ship to be docked. This
pontoon is first placed on the gridiron, and sunk
with it to the bottom of the water. Then the
ship is brought between the columns and over the
pontoon, and a 50-horse engine working the
hydraulic presses, raises the whole pontoon to-
gether. At this stage of the proceedings the
pontoon empties itself of water through valves
provided for the purpose; the valves are then
closed, and the gridiron being again lowered
to the bottom, the pontoon, with the vessel seated
upon it, is left afloat on the surface. The shorinc,
of the vessel (a work of difficulty and cost under the
old plan) is accomplished by large moveable frames
or slidinr, wedges, which, while under water, are
drawn into close contact with the vessel, so that
she sits on a large timber cradle without possibility
of being strained. In less than 40 minutes a ves-
sel drawing 18 or 20 feet of water is thus left
afloat on a shallow pontoon, drawing only 4 or 5
feet. At the Victoria Docks the lift consists of 16
columns, which give a working length of more
than 340 feet. Perfect horizontality while lifting
is secured, by arranging the presses in three inde-
pendent groups. According to the statement of
the company, the general advantages of the new
system may be summed up under the following
heads :-1. Independent of tides, and at all times,
whether by night or by day, vessels of the largest
dimensions, whether empty or loaded, may be raised
out of the water for examination. 2. The vessel
thus raised is transferred by floatation, without
rails or slip, to suitable docks for its repair, where
it lies high and dry on a convenient timber plat-
form, on the same level as the repairing shops with
which it is surrounded. In painting vessels, the
free exposure to the air is a most important advan-
tage. 3. One single lift or apparatus for raising
is sufficient for docking an unlimited number of
vessels. 4. The method employed in raising and
transporting vessels renders it impossible to
damage them by asy unequal strains. 5. The sup-
port of the vessel by cast-iron columns affords
means of constructing such docks either in open
water, in tideless seas, or in almost any locality,
independent of the character of the soil.
As confirmatory of thi ; statement the experiment
of yesterday was a perfect success. The vessel ex-
perimented upon was a fine ship of 870 tons regis-
ter, and some 1,200 or 1,250 tons burden, the
Jason, an Aberdeen clipper, which was floated upon
the stage, and by the application of the hydraulic
pumps was in about twenty minutes brought up
out of the water, and handed over to the manipu-
lative ingenuity of some 'two or three score of ship-
wrights, caulkers, and coppersmiths, by whom her
defects were in a very few minutes verified, and by
this time probably—owing to the facilities which
this new species of graving dock affords—are
remedied.

Amongst the company who werepr,sent to wit-
ness the experimeat, which was eminently success-
ful, were Sir J. Paxton, Sir S. M. Peto, Lord C.
Paget, Lord C. Hamilton, Messrs. R. Long, M.P.,
Hume, M.P., Crutchley, E. H. Stanley, Cooke,
Reid, G. F. Young, Crayshaw,_ J. Clarke. Lee
Stevens, A. Brett, Gen. Wylde, Col, Hume, P. Le
Neve Forster, &c. &c.