The artillery were used both for hurling missiles in battle, and for the attack on fortresses. The _tormentum_, which was an elastic instrument, discharged stones and darts, and was held in general use 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 resembling in form the head of a ram; it 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 swinging motion backward and forward. When this machine was further perfected by rigging it 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, the great length of the beam enabling the soldiers to work across the defensive ditch, and as many as one hundred men being 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 Titus 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 on cities, was a square tower furnished with all the means of assault. This also was a Greek invention; and the one 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. 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. These most formidable engines were generally made of beams of wood covered on three sides with iron and sometimes with rawhides. They were higher than the walls and all the other fortifications of a besieged place, and divided into stories pierced with windows; in and upon them were stationed archers and slingers, and in the lower story was a battering-ram. The soldiers in the turris were also provided with scaling-ladders, sometimes on wheels; so that when the top of the wall was cleared by means of the turris, it might be scaled by means of the ladders. It was impossible to resist these powerful engines except by burning them, or by undermining the ground upon which they stood, or by overturning them with stones or iron-shod beams hung from a mast on the