Note 90 — Chapter IV · THE PROGRESS OF ATTACK AND DEFENCE

This is the usual distinction. But the use of the names varies. In Vitruvius (op. cit., x. 10, 11) the catapulta or scorpio is a machine for shooting arrows, while the ballista is used for throwing stones. The pointed stakes at the siege of Marseilles (Cæsar, De Bell. Civ., ii. 2) were shot from ballistae. Vitruvius indicates several methods of working the ballista by torsion: “aliae enim vectibus et suculis (levers and winches), nonnullae polyspastis (pulleys), aliae ergatis (windlasses), quaedam etiam tympanorum (wheels) torquentur rationibus.”