Fire-BALLS, are bags of canvas filled with gunpowder, sulphur, salt-petre, pitch, &c. to be thrown by the soldiers, or out of mortars, in order to fire the houses, incommoding trenches, advanced posts, or the like.—The Greeks had divers kinds of fire-balls, or Πυροβολία λίβη; one kind called, more particularly, σκούλας, or σκούλας, made of wood, sometimes a foot or even a cubit long; their heads being armed with spikes of iron, beneath which were hemp, pitch, and other combustibles, which being set on fire, they were cast among the enemy. The preparations of fire-balls, among the moderns, consists of several operations, viz. making the bag, preparing the composition, tying, and, lastly, dipping the ball. 1. The bags for this purpose are either oval or round. 2. The composition wherewith fire-balls are filled, is various: To ten pounds of meal-gunpowder add two of salt-petre, one of sulphur, and one of colophony; or, to six pounds of gunpowder, add four of salt-petre, four of sulphur, one of powdered glass, half a pound of antimony, as much camphor, an ounce of sal-ammoniac, and four of common salt, all pulverised. Sometimes they even fill fire-balls with hand grenades. 3. For tying the fire-balls, they prepare two iron rings, one fitted round the aperture, where the ball is to be lighted, the other near its base. A cord is tied to these rings in such a manner, as that the several turns represent semicircles of the sphere cutting the globe thro' the poles: over the cords, extended according to the length of the ball, others are tied, cutting the former at right angles, and parallel to each other, making a knot at each intersection: lastly, after putting in a leaden-bullet, the rest of the space is filled with tow or paper. 4. Thus completed, the fire-ball remains to be dipped in a composition of melted pitch four pounds, colophony two, and linseed oil or oil of turpentine two; after dipping, they cover it round with tow, and dip again, till it be brought to the just diameter required.