BORE is a name for the internal cavity of a carmen, mortar, howitzer, rifle, musket, fowling-piece, pistol, or other kind of fire-arm. It is in most cases cylindrical; but in the Lancaster gun the B. is oval ; in the Whitworth gun, it is hexagonal ; while in the Arm strong, and many Other kinds of gun, It Is furrowed by spiral grooves. Technically, the B. of 'a gun often means simply the diameter of the cavity, as when we speak of a gun "of 8-inch bore;" and in that ease its meaning is equivalent to "caliber." The Botinio• of a cannon is a process which may best be described in connection with CANNON FOUNDING. It is desirable to mention in the present place, however, that there is an' operation called " boring-up " conducted at Woolwich arsenal, for enlarging the bore of a gun. has been found in recent years that many of the old Cannon are thicker and heavier than needful for the Size of shot propelled, and that they could be fitted for the discharge of larger shot without danger. A change was
begun the armament of the British fleet in 1839 by substituting heavier broad sides; and, as One part of the process, many of the old 24-pounders were " bored-up" to 32s; some of the 18-pounders were found to be thick and strong enough to undergo this process. More than 2000 iron naval guns were thus treated at Woolwich preparatory to the change in 1839; and many others have since been similarly bored-up. About 1860, important experiments were carried on at Woolwich, to determine whether the Old smooth-bore iron guns could not onlybe bored-up, but rifled at the same time. There were 15,000' of such guns belonging to the British government, and it was suggested that they ought to be improved, instead of being cast aside as useless in the event of the success Of the Armstrong and Whitworth guns. The process has not proved altogether satisfactory.