BALLISTA, in antiquity, a military machine used by the ancients in besieging cities, to throw large stones, darts, and javelins.
It resembled our cross-bows, though much larger and superior in force.
From this engine, stones of a size not less than mill-stones, were thrown with so much violence, as to dash whole houses in pieces at a blow. It is described thus: A round iron cylinder was fastened between two planks, from which reached a hollow square beam, placed cross-wise, and fastened with cords, to which were added screws; at one end of this stood the ingincer, who put a wooden shaft with a big head into the cavity of the beam; this done, two men bent the engine by drawing some wheels: When the top of the head was drawn to the outmost end of the cords, the shaft was driven out of the ballista, &c.