LIGHT-BALIS, for military purposes, are hollow cases, either spherical or in the form of cylinders, terminated at each extremity by a hemisphere : they are filled with a combustible composition, and being thrown, by night, in a burning state from mortars, or in some cases from the hand, they serve to discover the artlee or troops of the enemy.
The spherical cases are made of canvas or cartridge-paper, cut into eight equal gores of a proper form and the edges sewn together, a hole being left for the introduction of the composition and the application of a fuze. The oblong cases combat, frequently, of two hollow hemi spheres of iron, which are connected with each other by four "lender bars of iron attached to their bases, in positions parallel to the axis of the case, and the whole is then covered with canvas : the entire length is about If calibre of the piece of ordnance from which the ball is to be projected,—a mortar of one of the four different kinds, the calibre varying from 41 inches to 10 inches.
The composition consists of pulverised saltpetre (Gf lbs.), pulverised rosin (11 lbs.), ground sulphur (24 lbs.), and linseed oil (f lb.). The dry materials, after having been passed through a sieve, are mixed with the oil while the latter is in a boiling state; and sometimes a small quantity of monied gunpowder is added. The oblong balls are filled by paining the composition through a fuse-hole in one of the hemispheres and are afterwards strengthened by cord wound about them. The fire is communicated to either kind of ball, at the time of being projected, by means of a piece of in the fuse.
Previously to besieging a fortified place, the works and the ground about them arc reconnoitred, usually by night ; the first trenches are also traced and formed during the hours of darkness, and therefore the defenders, at the commencement of the siege, prepare some mortars charged with : these balls being thrown beyond the glacis, enable them to discover the operations of the enemy, and direct afire of shot against them. The assault of a breach is also frequently made by
night; and in this case are thrown by the defenders into the ditches of the place for the same purpose. These may be made by merely filling grenades with the composition above mentioned, and they may be thrown by hand.
Major-General Sir J. T. Jones states (' Journal that the defenders of the towns which were besieged by the British army in Spain threw in order to discover the operations of the attack; and that two or three men of the brigade were kept in readiness to run up and extinguish them as they fell. That officer adds that the men generally succeeded, in a few seconds, in smothering them with filled sand-bags, or by shovelling earth over them. Some casualties are stated to have occurred among the men so employed, but the fire of the enemy being directed against them was thereby diverted from the working-party often employed at only a few yards distance from the ball. On account of the great utility of such balls for illuminating the ground occupied by the enemy, Sir J. T. Jones recommended that grenades or other missiles should be connected with them by pieces of chain, in order that, through the risk of the explosion, men might be deterred from attempting to extinguish the light.
It may be added hero that spherical cases of pasteboard or canvas filled with a composition which while burning emits a great quantity of smoke, are frequently discharged from mortars in order to conceal a movement of troops from the view of the enemy : they are also occasionally thrown from the hand either to suffocate the inen employed in the galleries of military mines or to compel them to quit their work : these are called smoke-balls. The composition consists of mauled powder (5 lb.), pulverised saltpetre (I lb.), pulverised seacoal (1 f lb.), pitch (2 lb.), and tallow (f lb.): the pitch and tallow are melted together, and the dry materials, after being sifted, are mixed with the liquid.