machine used by the ancients for shooting darts; it resembled in some measure our crossbow. The word is Latin, signifying a cross-bow; and is derived from the Greek, βαλλειν, to shoot, or throw.

Vegetius informs us, that the ballista discharged darts with such rapidity and violence, that nothing could resist their force: and Athenaeus adds, that Agathitas made one of little more than two feet in length, which shot darts 500 paces.

Plate LVI. fig. 4, represents the ballista used in sieges, according to the chevalier Folard: 2, 2, the base of the ballista; 3, 4, upright beams; 5, 6, transverse beams; 7, 7, the two capitals in the upper transverse beam, (the lower transverse beam has also two similar capitals, which cannot be seen in this transverse figure); 9, 9, two posts or supports for strengthening the transverse beams; 10, 10, two skins of cords fastened to the capitals; 11, 11, two arms inserted between the two strands, or parts of the skins; 12, a cord fastened to the two arms; 13, darts which are shot by the ballista; 14, 14, curves in the upright beams, and in the concavity of which cushions are fastened, in order to break the force of the arms which strike against them with great force when the dart is discharged; 16, the arbor of the machine, in which a groove or canal perfectly straight is formed, and in which the darts are placed in order to their being shot by the ballista; 17, the nut of the trigger; 18, the roll or windlass, about which the cord is wound; 19, an hook, by which the cord is drawn towards the centre and the ballista cocked; 20, a stage or table on which the arbor is in part sustained.