88 NAVAL SCIENCES. 



B, the steam chamber ; D, the furnaces with the grates, G ; and the ash- 

 pans, which are shut by the doors, e. The flame passes through F, behind 

 the tubes, then through them, when it heats the water, which also surrounds 

 all the heated tubes, converting it into steam, and finally passes through the 

 front flue, I, into the chimney, C. The valves, a, give access to the tubes, 

 for the purpose of repairing them, and the state of the fire may be ascer- 

 tained by the sliders, b, b', b"; c and d are gauges showing the height of the 

 water. It will be perceived that here are two boilers, adjacent to each 

 other, with a common chimney. 



The earliest method of propelling steamships, and the most usual to the 

 present day, is by paddle-wheels. PL IS, Jig. 20, shows a longitudinal sec- 

 tion ; fig. 21, the upper part of the deck and the lower half of the frame ; and 

 fig. 22, the vertical cross-section of such a steamship. In the middle of the 

 ship, at F, is the engine, which, by its motion on the crank a, turns the 

 axis A, as we have seen above in the description of the steam-engine. On 

 each end of this axis. A, are two large paddle-wheels, G, which by their 

 revolution act as oars and propel the ship. The boilers are at E, and D is 

 the sheet iron chimney. O is the engineer's room, and GG are the wheel- 

 houses. The paddle-wheels are from 11 to 35 feet in diameter, and from 

 3 ft 12 feet in breadth. Their frames are of wrought iron ; the floats are 

 of wood, standing obliquely to the surface of the water, in order to avoid 

 the tremendous noise when the wheel strikes, and to diminish the loss of 

 power which always takes place at that time. The wheels sink about the 

 breadth of their paddles into the water. In order to take advantage of a 

 favorable wind, steamships are fitted out with masts and a pretty complete 

 set of sails, consisting both of yard-sails and gaff*-sails. The bowsprit 

 carries a jib and stay-sail. 



The first war-steamer was built in America in 1814. It was bomb-proof, 

 five feet thick in the sides, in order the better to resist the shot of the 

 enemy, and consisted of two vessels connected together, one of which had 

 the furnace and boiler and the other the steam-engine. Between the two 

 was the paddle-wheel. It also carried masts. The main-deck bore 32 

 18-pounder carronades, the balls for which were heated in the furnace. It 

 had an apparatus by which sixty casks of hot water could be thrown upon 

 an enemy who should attempt to board. PL 17, fig. 6, represents a French 

 steam-frigate with three masts, and which in case of necessity can be 

 propelled altogether by sails. PL 16, fig. 6, is the Bremen steamboat 

 Gutenberg, plying between Bremen and Bremen-haven, and carrying no 

 sails. Fig. 7 is the American steamer Washington, built in New York in 

 1846-7. The deck of this ship measures 230 feet. Its tonnage is 2000 tons 

 carpenters' measure. The keel is 16 inches square. The frame is of white 

 oak. The main-mast is 80 feet high and 28 inches in diameter, the fore- 

 mast 78 feet high and 25 inches in diameter, and the mizen-mast 76 feet 

 high and 21 inches in diameter. The bowsprit is 45 feet long, and the jib- 

 boom 24 feet. The ship has two engines with 72-inch cyHnders and 10 feet 

 stroke. The frame, the axis, and the working-beam are of wrought-iron. 

 The wheels are 30 feet in diameter. Each of the boilers is 36 feet long 

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