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A History of the Growth of the Steam-Engine

000 less than that of the Minotaur


British Minotaur was one of the earlier iron-clads. The great length and consequent difficulty of man[oe]uvring, the defect of speed, and the weakness of armor of these vessels have led to the substitution of far more effective designs in later constructions. The Minotaur is a four-masted screw iron-clad, 400 feet long, of 59 feet beam and 26-1/2 feet draught of water. Her speed at sea is about 12-1/2 knots, and her engines develop, as a maximum, nearly 6,000 indicated horse-power. Her heaviest armor-plates are but 6 inches in thickness. Her extreme length and her unbalanced rudder make it difficult to turn rapidly. With _eighteen men at the steering-wheel_ and sixty others on the tackle, the ship, on one occasion, was 7-1/2 minutes in turning completely around. These long iron-clads were succeeded by the shorter vessels designed by Mr. E. J. Reed, of which the first, the Bellerophon, was of 4,246 tons burden, 300 feet long by 56 feet beam, and 24-1/2 feet draught, of the 14-knot speed, with 4,600 horse-power; and having the "balanced rudder" used many years earlier in the United States by Robert L. Stevens,[102] it can turn in four minutes with eight men at the wheel. The cost of construction was some $600,000 less than that of the Minotaur. A still later vessel, the Monarch, was constructed on a system quite similar to that known in the United States as the Monitor type, or as a turreted iron-clad. This vessel is 330 feet long, 57-1/2 feet wide, and 36 feet deep, drawing 24-1/2
feet of water. The total weight of ship and contents is over 8,000 tons, and the engines are of over 8,500 horse-power. The armor is 6 and 7 inches thick on the hull, and 8 inches on the two turrets, over a heavy teak backing. The turrets contain each two 12-inch rifled guns, weighing 25 tons each, and, with a charge of 70 pounds of powder, throwing a shot of 600 pounds weight with a velocity of 1,200 feet per second, and giving it a _vis viva_ equivalent to the raising of over 6,100 tons one foot high, and equal to the work of penetrating an iron plate 13-1/2 inches thick. This immense vessel is driven by a pair of "single-cylinder" engines having steam-cylinders _ten feet_ in diameter and of 4-1/2 feet stroke of piston, driving a two-bladed Griffith screw of 23-1/2 feet diameter and 26-1/2 feet pitch, 65 revolutions, at the maximum speed of 14.9 knots, or about 17-1/2 miles, an hour. To drive these powerful engines, boilers having an aggregate of about 25,000 square feet (or more than a half-acre) of heating-surface are required, with 900 square feet of grate-surface. The refrigerating surface in the condensers has an area of 16,500 square feet--over one-third of an acre. The cost of these engines and boilers was L66,500.

[102] Still in use on the Hoboken ferry-boats.

Were all this vast steam-power developed, giving the vessel a speed of 15 knots, the ship, if used as a "ram," would strike an enemy at rest with the tremendous "energy" of 48,000 foot-tons--equal to the shock of the projectiles of eight or nine such guns as are carried by the iron-clad itself, simultaneously discharged upon one spot.

But even this great vessel is less formidable than later vessels. One of the latter, the Inflexible, is a shorter but wider and deeper ship than the Monarch, measuring 320 feet long, 75 feet beam, and 25 draught, displacing over 10,000 tons. The great rifles carried by this vessel weigh 81 tons each, throwing shot weighing a half-ton from behind iron-plating two feet in thickness. The steam-engines are of about the same power as those of the Monarch, and give this enormous hull a speed of 14 knots an hour.

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