Mr. Brunel had also considered the advantages of making the bore of the gun polygonal, with a projectile shaped to fit it. He had a portion of cannon tube and a projectile made by Mr. Armstrong in the beginning of 1855, but he did not himself pursue the question further.
Indeed, after the middle of the year 1856, when the works of the ‘Great Eastern’ steam-ship began to occupy a large portion of his time, Mr. Brunel was unable any longer to take part in gunnery investigations; but he watched with unabated interest the proceedings of those friends who have continued their experiments, with the great practical success of which he lived to see only the beginning.
Floating Gun-Carriage.
The plan of a gun-boat, or, as it would be more correctly called, a floating gun-carriage, which Mr. Brunel designed for an attack on Cronstadt and other Baltic forts during the Russian war, is clearly described in the following memorandum, which he drew up for the information of the Admiralty:—
December 20, 1855.
The principle is simply the fixing a very heavy gun in a floating shot-proof chamber or casemate, exposing the smallest possible surface; that surface to be of such a form as to be struck by shot only at a very oblique angle; and the gun being a fixture, with the means only of elevating and depressing to an extent of 10 or 12 degrees, but with no lateral motion, the port or embrasure need be only of the size of the muzzle of the gun, so that the gun, the men working the gun, and everything on board will be perfectly protected.
The gun will be directed by elevating the breech, and by slewing the vessel slightly and slowly backwards and forwards across the line of aim, by means afterwards explained.
The men loading the gun will simply load as quickly as they can, and when the gun is loaded push out a trigger.
The governor or person directing the gun will stand behind the hood or chamber, looking direct at the object through a telescope of low power, fixed horizontally in the axis of the vessel, and made to move vertically parallel with the axis of the gun, and mounted with reflectors; so that both telescope and man are completely under cover, and he, keeping the vessel truly in range and the elevation correct, will only touch the trigger whenever his line of sight crosses the object.
The vessel will carry a small engine, of power sufficient to drive it for a short time at a good speed, say eight or nine knots, and at other times to keep up a small forward motion to counteract the recoil, and to keep the vessel’s head moving a few degrees right and left across the line of range.