world's largest airguns?

USS Vesuvius used in the Spanish-American War of 1898 basically had airguns as her main armament. designed by Edmund Zalinski and known as dynamite guns these weapons were actually air guns. 15" smooth bore cast iron tubes were mounted on the forward part of the ship. they were charged by large air compressors which gave them an operating pressure of 1000psi. the projectiles were large brass or steel containers 7ft. in length with fins which gave the projectiles spin thus stabilizing their flight. the explosive was not actually dynamite but a combination of nitrocellulose and nitroglycerine. these huge airguns could hurl their load up to 11/2 miles. apparently the resulting explosion was quite impressive. the guns were aimed by pointing the ship at the target. the range was varied by the amount of air pressure used for the shot. as it turned out this was an interesting but not practical proposition for a warship. the Vesuvius was thus the only dynamite cruiser ever used by the USN or any navy.