Parrott Gun

—The Parrott rifled gun is a cast-iron piece of about the usual dimensions, strengthened by shrinking a coiled band or barrel of wrought iron over that portion of the reinforce which surrounds the charge. The body of the larger Parrott guns are cast hollow, and cooled from the interior on the Rodman plan. The barrel is formed by bending a rectangular bar of wrought iron spirally around a mandrel, and then welding the ma together by hammering it in a strong cast-iron cylinder, or tube. In bending the bar, the outer side being more elongated than the inner one, is diminished in thickne , giving the cro -section of the bar a wedge shape, which po e es the advantage of allowing the cinders to escape through the opening, thereby securing a more perfect weld. The barrel is shrunk on by the aid of heat, and for this purpose the reinforce of the gun is carefully turned to a cylindrical shape, and about one-sixteenth of an inch to the foot larger than the interior diameter of the barrel in a cold state. To prevent the cast iron from expanding when the barrel is slipped on to its place, a stream of cold water is allowed to run through the bore. At the same time, and while the band hangs loosely upon it, the body of the gun is rotated around its axis to render the cooling uniform over the whole surface of the barrel. The proof of the Parrott guns consists in firing each piece 10 rounds with service charges.