From an old lithograph.
However, the success of the Princeton as a ship was so pronounced that money was appropriated from time to time for others designed much as she was until the navy had six screw frigates—the Niagara, the Roanoke, the Colorado, the Merrimac, the Minnesota, and the Wabash; six screw sloops of the first class—the San Jacinto, the Lancaster, the Brooklyn, the Hartford, the Richmond, and the Pensacola, besides eight screw sloops of the second class, of which the Iroquois was a type, and five of the third class, of which the Mohawk was a type. There was also a screw frigate on the stocks at the Portsmouth, New Hampshire, dock-yard. The guns that these ships carried, when compared with those of the war of the Revolution, were quite as interesting as the ships themselves.
U. S. Frigate Pensacola off Alexandria.
From a photograph taken in 1865.
The prejudices in the way of improving great guns were not only strong, but they were founded on experiences that were seemingly convincing beyond peradventure. For instance, under Charles V a cannon was cast at Genoa that was fifty-eight calibres long; that is, it was of about six inches diameter of bore and twenty-nine feet long. When fired, its ball of thirty-six pounds weight had less range than an ordinary twelve-pounder. So they cut off four feet of the gun and found that its range increased. Cutting off three feet more still further increased the range, as did another cut of six inches—“which shows,” says Simpson’s text-book on gunnery, printed in 1862, “that there is for each piece a maximum length which should not be exceeded.” So that dictum stood in the way of arriving at the design of a gun like the modern rifle, that would really give the greatest possible range to a projectile. Then, the distribution of the metal in the cannon with which Arnold fought on Lake Champlain seems now ridiculous. One must needs see a picture of the old gun beside one of the guns as developed just previous to the Civil War to realize the difference; but it may be said that, with the bell-shaped muzzle and the “rings” and “reinforces,” the old gun in outline had as many ups and downs as some step-ladders, while the cast-iron weapon of 1860 was as smooth and symmetrical as the hull of a Yankee clipper.
A Twelve-pound Bronze Howitzer—the First One Made in the United States.
From a photograph of the original at the Brooklyn Navy Yard.
A curious series of experiments, made by Colonel Bomford of the United States Ordnance Department, told for the first time where the greatest strain was exerted on the bore of a gun, and gave some idea of the relative strain elsewhere along the bore. Taking an old cannon, he drilled a hole from the side near the muzzle directly into the bore and inserted a pistol-barrel. Then he put a bullet into the pistol-barrel, and after loading the cannon in the ordinary way, he fired it. Of course, as the cannon-ball was driven from the big gun the powder gas behind it drove the pistol-ball from the pistol-barrel. The colonel measured the velocity of the pistol-ball and made a note of it. Then he drilled another hole in the cannon some inches farther from the muzzle, and repeated the experiment. The force exerted on the pistol-ball was slightly greater there. By drilling other holes he learned approximately the pressure all along the bore. It appeared that the greatest pressure was directly over the shot when it was rammed home against the powder. From there the pressure decreased rapidly, being only about half as much when the ball had travelled four times its own diameter from its original resting place.