(Machina), in the general, signifies any thing that serves to augment or to regulate moving powers: Or it is any body destined to produce motion, so as to save either time or force. The word comes from the Greek μηχανή, "machine, invention, art;" And hence, in strictness, a machine is something that consists more in art and invention, than in the strength and solidity of the materials; for which reason it is that the inventors of machines are called ingeniours or engineers.

Machines are either simple or compound. The simple ones are the seven mechanical powers, viz. lever, balance, pully, axis and wheel, wedge, screw, and inclined plane. See Mechanics.

From these the compound ones are formed by various combinations, and serve for different purposes. See Mechanics and Hydrostatics; also the articles A-Machinery, Agriculture, Cannon, Centrifugal, Fire, Steam, Furnace, Burroughs, Ramsden, &c. &c.

MACHINES used in war amongst the Greeks, were principally these: 1. Κλίμακες, or scaling ladders; 2. The battering ram; 3. The helepolis; 4. The τορτούσιον or tortoise, called by the Romans testudo; 5. The χωμά or agger, which was faced with stone, and raised higher than the wall; 6. Upon the χωμά were built πύργοι or towers of wood; 7. Πέργαλα, or other hurdles; 8. Cata-pulta, or καταπέλται, from which they threw arrows with amazing force; and, 9. The λιθόβαλτοι, περιβολοί, or apinaria, from which stones were cast with great velocity.

The principal warlike machines made use of by the Romans were, the ram, the lupus or wolf, the testudo or tortoise, the ballista, the catapulta, and the scorpion.