more water was used. After cooling the gun the machining process began. The bore was bored out to proper size, the exterior was turned smooth, the trunnions were turned on a trunnion lathe, and a vent was drilled. Columbiads were not the only guns cast using Rodman's method. Dahlgren XV-inch shell guns for the U.S. Navy were also hollow cast. A 20-inch hollow cast gun, which may not have been identical to the two guns supplied to the U.S. Army, was sold to Peru. Rodman guns were cast at the Fort Pitt Foundry, Pittsburgh, Pennsylvania; the Scott Foundry, Reading, Pennsylvania; Cyrus Alger & Co., Boston, Massachusetts; and the West Point Foundry, Cold Spring, New York. Carriages Rodman guns were mounted on three types of carriages—a front-pintle barbette carriage, a center-pintle barbette carriage, and a casemate carriage. All of these carriages were made of wrought iron. All three types of carriage were similar in design, having an upper carriage that was placed on a two-rail chassis. The gun and upper carriage recoiled along the chassis. The chassis would pivot to train the gun left or right. The barbette carriages were designed to fire over a parapet and could be used in either permanent or temporary fortifications. The front pintle carriage pivoted at the front of the chassis. This made the gun mount more compact and allowed the gun and detachment to be better protected by embrasures and traverses. The center pintle carriage gave the gun a 360° traverse and was stronger for guns firing at high angles because the pintle, the strongest part of the carriage, would have been under the breech when the gun was fired at high angles. The casemate carriage was designed to fire from casemates which were chambers in permanent fortifications. The carriage was essentially a front-pintle design, with the pintle fixed in the masonry in front of the chassis and below the guns embrasure. A "tongue" connected the chassis to the pintle. The casemate carriage has a lower profile than the barbette carriages. The 8-inch and 10-inch Rodman guns could be mounted on all three types of carriages. The 15-inch Rodman guns were mounted on both types of barbette carriage. The two 20-inch guns were mounted on front-pintle barbette carriages. Sling carts were used to transport these guns to the carriages. Production Rodman guns were all nearly identical in design, with a curving soda bottle shape,