The artillery were used both for hurling missiles in battle, and for the attack of fortresses. The _tormentum_, which was an elastic instrument, discharged stones and darts, and was continued until the discovery of gunpowder. In besieging a city, the ram was employed for destroying the lower part of a wall, and the balista, which discharged stones, was used to overthrow the battlements. The balista would project a stone weighing from fifty to three hundred pounds. The _aries_, or battering-ram, consisted of a large beam made of the trunk of a tree, frequently one hundred feet in length, to one end of which was fastened a mace of iron or bronze, which resembled in form the head of a ram, and was often suspended by ropes from a beam fixed transversely over it, so that the soldiers were relieved from supporting its weight, and were able to give it a rapid and forcible motion backward and forward. And when this machine was further aided by placing a frame in which it was suspended upon wheels, and constructing over it a roof, so as to form a _testudo_, which protected the besieging party from the assaults of the besieged, there was no tower so strong, no wall so thick, as to resist a long-continued attack. Its great length enabled the soldiers to work across the ditch, and as many as one hundred men were often employed upon it. The Romans learned from the Greeks the art of building this formidable engine, which was used with great effect by Alexander, but with still greater by Vespasian in the siege of Jerusalem. It was first used by the Romans in the siege of Syracuse. The _vinea_ was a sort of roof under which the soldiers protected themselves when they undermined walls. The _helepolis_, also used in the attack of cities, was a square tower furnished with all the means of assault. This also was a Greek invention, and that used by Demetrius at the siege of Rhodes, B.C. 306, was one hundred and thirty-five feet high and sixty- eight wide, divided into nine stories. Towers of this description were used at the siege of Jerusalem, [Footnote: Josephus _B. J._, ii. 19.] and were manned by two hundred men employed upon the catapults and rams. The _turris_, a tower of the same class, was used both by Greeks and Romans, and even by Asiatics. Mithridates used one at the siege of Cyzicus one hundred and fifty feet in height. This most formidable engine was generally made of beams of wood covered on three sides with iron and sometimes with raw hides. They were higher than the walls and all the other fortifications of a besieged place, divided into stories pierced with windows. In and upon them were stationed archers and slingers, and in the lower story was a battering-ram. They also carried scaling-ladders, so that when the wall was cleared, these were placed against the walls. They were placed upon wheels, and brought as near the walls as possible. It was impossible to resist these powerful engines,