Cement. Hydraulic cements are much used in building permanent fortifications. The cement used by the Romans in their great sea-walls, aqueducts, etc., which are still standing as monuments of their civil engineering, was pozzuolana, a volcanic earth from near Baiæ, Italy. It is still an article of export from Italy. The most noted modern cement is Portland, made artificially in England by burning a mixture of the chalk and clay from the valley of the Medway.
Cementation. In metallurgy, is the process of converting metals by absorption under great heat. Specially applied to the conversion of iron into steel by causing it to absorb carbon. The iron bars are imbedded in charcoal and exposed to prolonged heat in a closed furnace. The qualities of the resulting steel vary with the degree and duration of the heating. The bars, when removed, are called blistered steel from their appearance. See [Ordnance, Metals for, Blistered Steel].
Cenotaph. The empty tomb of a hero, or monument erected in honor of a person, without the body of the deceased being interred in or near it.
Centesimation. In ancient military history, a mild kind of military punishment, in cases of desertion, mutiny, and the like, when only every one hundredth man was executed.
Central America. Includes the republics of [Guatemala], [San Salvador], [Honduras], [Nicaragua], and [Costa Rica] (which see). They declared their independence September 21, 1821, and separated from the Mexican Confederation July 21, 1823. The states made a treaty of union between themselves March 21, 1847. There has been among them since much anarchy and bloodshed.
Centre. A point equally distant from the extremities of a line, figure, or body; the middle point or place of anything.
Centre of an Army. The body of troops occupying the place in the line between the wings. See [Target].
Centre of Gravity. The point of a body about which all its parts are balanced. This is a matter of great importance in cannon, both for mechanical manœuvres and for ordinary handling. In all large guns in the United States, and in many in Europe, the axis of the trunnions passes through the centre of gravity of the gun. Such guns have no preponderance, and need no support in firing except the trunnions. This innovation was introduced by the genius of Rodman, and brought many advantages in the handling of heavy guns. In projectiles, the centre of gravity, or inertia, is also a thing of moment. Spherical projectiles in which this point does not coincide with the centre of figure are said to be eccentric, and are subject to certain deviations (see [Projectiles]); deviation of the relative position of these points influences the flight also of rifle projectiles.
Centre of the Bastion. In fortification, is the intersection made by the two demi-gorges.
Centrifugal Gun. A form of machine gun in which balls are thrown from a chambered disk rotating with great speed.