Figure 1—BALLISTA. Caesar covered his landing in Britain with fire from catapults and ballistas.
The trebuchet was another war machine used extensively during the Middle Ages. Essentially, it was a seesaw. Weights on the short arm swung the long throwing arm.
Figure 2—CATAPULT.
Figure 3—TREBUCHET. A heavy trebuchet could throw a 300-pound stone 300 yards.
These weapons could be used with telling effect, as the Romans learned from Archimedes in the siege of Syracuse (214-212 B.C.). As Plutarch relates, "Archimedes soon began to play his engines upon the Romans and their ships, and shot stones of such an enormous size and with so incredible a noise and velocity that nothing could stand before them. At length the Romans were so terrified that, if they saw but a rope or a beam projecting over the walls of Syracuse, they cried out that Archimedes was leveling some machine at them, and turned their backs and fled."
Long after the introduction of gunpowder, the old engines of war continued in use. Often they were side by side with cannon.