The subject of the ancient machines is treated with great knowledge and ingenuity by the Chevalier Folard (Polybe, tom. ii. p. 233-290). He prefers them in many respects to our modern cannon and mortars. We may observe, that the use of them in the field gradually became more prevalent, in proportion as personal valour and military skill declined with the Roman empire. When men were no longer found, their place was supplied by machines. See Vegetius, ii. 25. Arrlan.