or BALLISTRÆA, in antiquity, a military song or dance used on occasions of victory. Vopiscus has preserved the balistæum sung in honour of Aurelian, who, in the Sarmatian war, was said to have have killed 48 of the enemy in one day with his own hand. *Mille, mille, mille, mille, mille, mille decollavit; unus homo mille, mille, mille, mille decollavit; mille, mille, mille vivat, qui mille, mille occidit.* Tantum vini habet nemo, quantum judet sanguinis. The same writer subjoins another popular song of the same kind: *Mille Francos, mille Sarmatas, semel occidimus; mille, mille, mille, mille, Persos, quarinus.* It took the denomination *ballistum* from the Greek βαλλων, jacio, or jacto, to cast or toss, on account of the motions used in this dance, which was attended with great elevations and swingings of the bands. The *ballista* were a kind of popular ballads, composed by poets of the lower class, without much regard to the laws of metre.

**BALLISTIC PENDULUM,** an ingenious machine invented by Benjamin Robbins for ascertaining the velocity of military projectiles, and consequently the force of fired gunpowder. It consists of a large block of wood, annexed to the end of a strong iron stem, having a cross steel axis at the other end, placed horizontally, about which the whole vibrates together like the pendulum of a clock. The machine being at rest, a piece of ordnance is pointed straight towards the wooden block, or ball of this pendulum, and then discharged: the consequence is this; the ball discharged from the gun strikes and enters the block, and causes the pendulum to vibrate more or less according to the velocity of the projectile, or the force of the blow; and by observing the extent of the vibration, the force of that blow becomes known, or the greatest velocity with which the block is moved out of its place, and consequently the velocity of the projectile itself which struck the blow and urged the pendulum. *Hutton's Mathemat. Dict.*

**BALLOON,** or **BALON,** in a general sense, signifies any spherical hollow body, of whatever matter it be composed, or for whatever purposes it be designed. Thus, with chemists, balloon denotes a round short-necked vessel, used to receive what is distilled by means of fire; in architecture, a round globe on the top of a pillar; and among engineers, a kind of bomb made of pasteboard, and played off, in fire-works, either in the air or on the water, in imitation of a real bomb.

**Air-Balloon.** See **AEROSTATION.**