The original gun, which was invented by Colonel Bomford, and whose dimensions were carried to General Paixhan in France, is now lying at the ordnance depot, in New York harbor.] All these, except the smaller mortars, are made of cast iron.

This substance is less tenacious than wrought iron or bronze, and the cannon made of it are, on this account, much heavier than of the other materials; but for the naval service, and the attack and defence of fortifications, the weight required to secure the necessary strength is not very objectionable.

Wrought iron and bronze are much more expensive and less durable.

Moreover, the difficulty of forging wrought iron in masses of sufficient size has been such as to prevent its being brought into general use for artillery.

Numerous attempts have been made, at different periods, to construct large guns of this material, but none have yet been successful.