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EXPLANATION OF THE PLATES.
PLATE XL.
ENGINES OF THE GRAVESEND PACKET RUBY.
This celebrated vessel, undoubtedly the fastest in Europe, and perhaps in the world,
was built by Mr. Wallis, of Blackwall, near London, in the year 1836, from the de
signs and specifications of Mr. 0. Lang, Jun., of Her Majesty’s Dock Yard, Woolwich.
The engines were made by Messrs. Seawards and Co., of the Canal Iron Works, near
London.
The very great success of this vessel, she having beaten all competitors from the
time of her starting to the present, may be attributed to two principal causes :—
First, to a most judicious arrangement in the form and construction of the vessel,
by which the quantity of materials used in the building are brought so to bear upon
one another that each piece performs the office assigned to it; and no more timber
is used than what is requisite to give the ship the necessary strength and solidity.
From the method of planking which is adopted, consisting of three thicknesses of oak
placed diagonally and longitudinally, the vessel is completely trussed from end to end,
and at once combines strength and lightness in an eminent manner. The length of the
Ruby is 155 feet between the perpendiculars, 19 feet beam, and 9 feet 6 inches
depth of hold; she will carry with ease 800 passengers. When launched she drew
about two feet of water. Her after cabin is 33 feet long, and will dine 100 pas
sengers ; the ladies’ cabin is about 15 feet long, and the fore cabin 33 feet.
Secondly, her superiority is attributable to her engines, which consist of two 50
horse power engines, (100 horse power the two,) in the making and fixing of which,
every care was taken to have them as light and efficient as possible, without endan
gering their stability; and the calculation of weights and of displacement was so
nicely adjusted, that when the whole of the weights were on board, and the vessel
equipped for service, her real draught of water, 4 feet fore end and 4 feet 6
inches aft, was within a quarter of an inch of the builder’s estimate. The weight of
the engines complete with the water in the boiler is exactly 90 tons 5 cwt., being
about 18 cwt. to the horse power; the diameter of the cylinder is 40 inches, length
of stroke 3 feet 6 inches, diameter of outer edge of paddle wheel 17 feet, and
length of board 9 feet 2 inches, with a dip of 17 inches with 200 passengers
on board; then the speed of the engines is 30 strokes per minute, the pressure of the
steam being only lbs. above the atmosphere. The speed of the piston is there
fore 210 feet per minute, the speed of the outer edge of the paddle board is nearly
20 miles per hour, and the speed of the vessel through still water by repeated trials
is exactly 13J miles per hour.