Laminated steel gun-barrels were well known in 1851; but the English bugbear, prejudice, raised a clamour against them, which was echoed by interest and ignorance, and thus their general adoption was for a long time prevented. However, in the short space of seven years, they have become universally adopted, with the most beneficial results; better shooting, less annoyance from recoil, less weight to carry, and greater safety to the sportsman, being the principal. And so it will be with steel cannon; as a short time will suffice to enable scientific investigation to remove all prejudices against them. The external form of cannon is a question of vital importance, but one which is little understood by artillerists of the present day. Whilst it is a demonstrable fact that all excessive bulk of cast-iron causes weakness in proportion to the excess, no effectual steps have as yet been taken by the Government to ascertain what is the due proportion of metal which ought to exist in different parts of the gun. The American authority on naval gunnery, Captain Dhalgren, has paid considerable attention to this subject; and if the reports on the durability of American heavy ordnance can be relied on (and there is no reason why they should not) his investigations have been attended with much success. Captain Dhalgren has extended the principle acted upon many years ago by Mr. Monck; his great improvement consisting in lessening the weight of iron in front of the trunnions, and adding to that of the breech. In cannon, as in fowling-pieces, weight in the fore part is useless; conducing neither to the safety of the gun, nor to the smartness of its shooting. For endurance, it is necessary that the expansion should be equal in every part of the gun; rigidity in one part increasing the strain on the immediately adjacent parts, which, if much reduced, are thus rendered liable to fracture. The breech has to endure the lengthened explosion produced by the burning of the gunpowder; and, as this continues until it has overcome the inertia of the projectile, it is necessary in all cases that the maximum of strength should be in the breech of the gun. When the projectile is once in motion the strength of the tube may be rapidly decreased; the only strain it has to bear is exerted whilst the projectile is passing over it; and this strain, in properly constructed guns, becomes of shorter and shorter duration as the projectile attains its highest velocity at the muzzle of the gun. The greatest strain a gun has to bear near the muzzle is that produced by the condensation of the column of air in front of the charge; and in almost every form of English ordnance the weight of metal here is greater than is necessary.