364 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 1 8 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 3-| Ibs. 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 13^ miles per hour. 



