(Aries)**, a military engine used before the invention of gunpowder, for beating down the walls of besieged fortresses. Generally speaking, it consisted of a long heavy beam of timber, armed at the extremity with iron fashioned something like the head of a ram, which being violently propelled with constant successive blows against a rampart or tower, shook the fabric of masonry, and in time caused it to tumble down.

In its simplest form it consisted of a beam such as we have described, which the soldiers carried in their arms, and with one end of which they assailed the walls by main force. The improved ram was composed of a vast beam, like the mast of a ship, shod with iron at one end, and suspended either by the middle, or from two points, from another beam laid across two posts; and hanging thus equally balanced, it was successively drawn backwards and driven forwards with accumulated momentum against the wall or rampart. This is the kind described by Josephus as having been used at the siege of Jerusalem (*B. J.* iii. 7.§19). It was also covered over with a roof, shell, or screen of boards, to protect the men employed in working it from the stones, darts, and other missiles discharged by the besieged from the walls; whence it was called *testudo arrietaria*. It was also provided with wheels, which greatly facilitated its operations. (Vitruv. x. 19.)

Plutarch informs us that, in the Parthian war, Mark Antony made use of a ram 80 feet in length; and Vitruvius states that this engine was sometimes 106, sometimes even 120 feet in length; a circumstance to which we are to ascribe its prodigious force when vigorously worked. The battering-ram required a century of soldiers at a time to manage it; and as the working parties were regularly relieved as they became exhausted, it was kept in continual action, and from incessant iteration produced the most extraordinary effects. In fact, the momentum of a battering-ram 180 feet in length, 28 inches in diameter, armed with a head of iron weighing a ton and a-half, and moved by the united strength of a hundred men, must have been equal to the momentum of a thirty-six pound shot discharged point blank from a modern piece of heavy ordnance; and hence it is not difficult to conceive how effective the constant reiteration of such impulses would become in the work of demolition.