But while these upright walls will resist a direct shot, it is equally necessary to guard against a plunging fire, and therefore the space between the turrets, at least, must be roofed over with a steel deck, two or three inches thick, to deflect shot that come just over the top of the armor-belt. In addition to this, on each side of the vessel are erected one or two smaller turrets, carrying somewhat smaller guns than those of the forward and after turrets, and also protected by heavy barbettes which reach down to the armor-belt and thoroughly protect the turning mechanism, passage of ammunition, etc. These various upper parts are connected by defenses which may not resist the largest shells, but are safe against smaller shot. Now, what is the armament of this fortress which thus protects all the motive power and interior machinery of the ship, by which she can be made so terrible an engine of combative force? Well, it is as different from the bronze “long-toms” and carronades of the old three-deckers, or even from ten-inch smooth-bore “Dahlgrens” of the days of our Civil War, as is the ship itself from old-time models. In place of broadside batteries of forty or fifty cannon hidden in clouds of smoke, there are now six or eight big rifles, from whose muzzles wreaths of thin gas only drift to leeward; and, more striking still, in contrast, a ship is no longer comparatively helpless when headed or turned sternward to an enemy,—when the “raking,” formerly so justly dreaded, would be received,—but is rather more able to do damage in that position than by a “broadside.” The guns themselves are marvels of structure and power. All of those used in the United States navy are made by the government in the gun-shops at the Washington navy-yard, and are “built up.” The methods and tools required for this are the invention of Americans, as well as the complicated arrangements for closing the breech, and the carriages and mechanism for overcoming the tremendous recoil and handling the ponderous ammunition; the latter, often weighing hundreds of pounds, is handed up to the gunners from the magazines below by hoists worked by electricity. The history of the development of heavy ordnance, especially that applied to naval uses, is one of the most interesting chapters in mechanics; and a surprising number of ways of making a ship’s cannon have been tried and rejected. Out of this two things seem now to be settled: namely, that a gun composed of steel in separate parts welded together is best, and that the best missile to shoot from it is a conical shell, very hard and heavy, yet containing an explosive small in quantity but exceedingly powerful.