Battering Ram (Lat. aries), the earliest machine for destroying stone walls and the ordinary defences of fortified towns. The primitive form of this instrument was a huge beam of seasoned and tough wood, hoisted on the shoulders of men, who ran with it at speed against the obstacle. The second step was strengthening and weighting the impinging end of the machine with a mass of bronze, brass, or iron. The third improvement was suspending it by chains or ropes from a crane or trivet, in such a manner as to allow it to swing some 30 or 40 feet to and fro, under the impulse of human force, as nearly as possible on the plane of the horizon. When the impetus was once given to this vast beam of wood, 100 or 150 feet in length, all that was requisite was to impart to it such continued motive force as to keep it in play, when its own impetus would of course gradually increase; and it would necessarily act with the force of its own natural weight, multiplied by a constantly increasing measure of velocity, upon the object on which it impinged.
To this must be added that the ram being, in its most highly improved state, played in exact time, it acquired a perfect vibratory motion itself; and its blows being directed continually on one spot, at regular intervals, a similar vibration was communicated to the wall; which, increasing with the increased weight of the blows, a second wave being always put in circulation from the centre of the attack before the preceding wave had subsided, soon set the whole mass of masonry surging and swaying backward and forward. The objections to it were, that it could only be used at close quarters, where direct access could be had to the foot of the fortification which was to be beaten down, by bodies of men, who necessarily worked for the most part in full view, and exposed to the missiles of the defenders at an exceedingly short range. The former of these requirements rendered it necessary to fill up or bridge over the moats or ditches in front of the work. The latter led to the construction of towers of planking, covered with raw hides, of many stories in height, rolling on wheels; in the lower stage of which the ram was slung so that the men who worked it could do so perfectly under cover, while the upper stages were filled with archers and slingers, whose duty it was to operpower the fire of the defenders.
From the top of these machines a sort of bridge was also contrived, which could be lowered and hauled out with chains and pulleys so as to fall on the summit of the tower or castle wall, and give free access to the assailants. These towers, which were the last improvement on the ram, were so arranged that they were not only fought but propelled by men, either within the structure, or placed behind it, in such a manner as to be protected by it from the shot of the enemy. They continued to be in use during all the middle ages, and were still effective until ordnance was so much improved that it could be discharged "rapidly and with correct aim.
See Battering Ram.