MECHANICS AND USEFUL ARTS. 71 



frames are joined. There are no projecting armor shelves on the 

 sides, but the vessel is protected from shot by single plates four and a 

 half inches in thickness with the additional protection of a layer of 

 nine-inch locust and three-inch oak timber, covered again with two- 

 inch solid plates of iron, thus making the mail in reality 18^ inches 

 thick, 6 of which are iron. The draught of the ship will be ten feet. 



There are two propellers or screws, one on each side under the 

 stern, each propeller being driven by two engines. The turrets are 

 the same as those upon all the monitors ; eleven inches thick in the 

 walls, nine feet high and twenty-one feet in diameter inside. There 

 are two fifteen-inch guns in each turret. Neither the bow nor stern of 

 the Onondaga overhangs the hull, the stern projecting only enough to 

 cover the screws and protect them from damage by shot. There are 

 thirteen transverse water-tight compartments, and the coal bunkers 

 surround the boilers in addition to the protection afforded by the iron 

 plating. 



The .Dictator. This name has been given to an iron-clad war-ship 

 constructed during the past year in New York, from designs by Erics- 

 son, based on the principles of the first monitor, but superior, so far as 

 relates to size, speed, sea-worthiness, and impenetrability, to any armor- 

 clad vessel hitherto constructed in the United States. The following- 

 statement of the points and dimensions involved in her construction we 

 copy from the Scientific American : u The extreme length of the 

 vessel over all, is 314 feet ; its aft overhang being thirty-one feet, and 

 forward overhang thirteen, leaving 260 feet between perpendiculars ; 

 extreme breadth fifty, and depth 22^ feet. The hull, in sides and 

 frame, is constructed of iron. The armor shelf extends outside of the 

 hull four feet on each side, and is prodigiously strong. Some idea of 

 its impenetrable character will be derived from the following account 

 of its construction. The outside is covered with six one-inch plates of 

 iron fastened in the most substantial manner, and inside of this are 

 three feet of oak timber and an armor lining formed of 4J inch bars 

 extending all around. The armor shelf therefore consists of 10^ inches 

 in thickness of iron, and three feet of timber, and between the metal 

 and timber is interspersed a thick layer of felting. No gun yet fabri- 

 cated can project a shot that will pierce this armor-jacket. 



The keel-plate of the Dictator is of one-inch plate, the side plates -|th 

 inch, and the frame of Double angle-iron, six by four inches. The in- 

 terior is divided into several water-tight compartments by plate bulk- 

 heads, and the space forward of the third bulk-head below will be used 

 for coal bunkers, through the middle of which will be a railway to 

 carry the fuel to the boilers. The deck beams are of kyanized oak. 

 Two engines, each having a cylinder of one hundred inches in diame- 

 ter and four feet stroke, will be employed to drive the screw, which is 

 four-bladed, 21|- feet in diameter, and of thirty-four feet pitch. Six 

 boilers, capable "of furnishing 5000 horse-power to the engines, supply 

 the motive force. The boilers have fifty-six furnaces and an aggregate 

 grate surface of 1,000,100 feet ; and allowing twelve pounds of coal 

 per square foot of grate surface, the vessel will require, at the least, 175 

 tons of coal per day of twenty-four hours, steaming at full speed. 



As the Dictator is furnished with a strong bow, its speecf, strength, 

 and mass will render it a must eiiicieut marine rani. . It is provided 



