The modern long-range guns and improved howitzers have, however, virtually superseded mortars. _Machine-guns_ of various forms are comparatively small and light, transportable by hand, and filling a place between cannon and small-arms, the latter term embracing the soldier’s personal armament of rifle and pistol or revolver, which are carried in the hand. A group of guns of the like design are generally given the name of their first inventor, or the place of manufacture: such as the Armstrong gun, the Vickers-Maxim, the Martini-Henry rifle, or the Enfield. The indifferent use of several expressions in describing the same weapon is, however, rather confusing. One particular gun may be thus referred to:--by its _weight_ in tons or cwt., as “the 35-ton gun”; by the weight of its _projectile_, as “a 68-pounder”; by its _calibre_, that is, size of bore, as “the 4-inch gun.” Of these the heavier breech-loading (B.-L.) and quick-firing (Q.-F.) guns are generally known by the size of bore; small Q.-F.’s, field-guns, &c., by the weight of projectile. It is therefore desirable to enter these particulars together when making any list of service ordnance for future reference. No individual gun, whether large or small, is a single whole, but consists of several pieces fastened together by many clever devices. The principal parts of a cannon are:-- (1) The _chase_, or main tube into which the projectile is loaded; terminating at one end in the muzzle. (2) The _breech-piece_, consisting of (_a_) the chamber, which is bored out for a larger diameter than the chase to contain the firing-charge. (_b_) The _breech-plug_, which is closed before the charge is exploded and screwed tightly into place, sealing every aperture by means of a special device called the “obturator,” in order to prevent any gases passing out round it instead of helping to force the projectile forwards towards the muzzle. The whole length of inside tube is termed the _barrel_, as in a machine-gun, rifle, or sporting-piece, but in the two latter weapons the breech-opening is closed by sliding or springing back the breech-block or bolt into firing position. Old weapons as a rule were smooth-bored (S.-B.), firing a round missile between which and the barrel a considerable amount of the gases generated by the explosion escaped and caused loss of power, this escape of gas being known as _windage_.