This engine was of much more recent invention than either the catapult or the balista of the Greeks and Romans. It is said to have been introduced into siege operations by the French in the twelfth century. On the other hand, the catapult and the balista were in use before the Christian Era. Egidio Colonna gives a fairly accurate description of the trebuchet, and writes of it about 1280 as though it were the most effective siege weapon of his time.

The projectile force of this weapon was obtained from the terrestrial gravitation of a heavy weight, and not from twisted cordage as in the catapult and balista.

From about the middle of the thirteenth century, the trebuchet in great measure superseded the catapult. This preference for the trebuchet was due to the fact that it was able to cast stones of 300 lbs. and more in weight, or five or six times as heavy as those which the largest catapults could project.

The stones of 50 to 60 Lbs. thrown by siege catapults would no doubt destroy towers and battlements, as the result of the constant and concentrated bombardment of many engines. One huge stone of 300 Lbs., as slung from a trebuchet, would however shake the strongest defensive masonry and easily break through the upper parts of the walls of a fortress.

The trebuchet was essentially an engine for destroying the defences of a fortification, so that it might be entered by means of scaling ladders or in other ways.

From experiments with models of good size and from other sources, I find that the largest trebuchets - those with arms of about 50 ft. in length and counterpoises of about 20,000 Lbs.- were capable of slinging a stone 300 Lbs. in weight to a distance of 300 yards, a range of 350 yards being in my opinion more than these engines were able to attain.¹

¹ Egidio Colonna tells us that the trebuchet was sometimes made without a counterpoise, and that in such a case the arm of the engine was worked by a number of men pulling together instead of by a heavy weight. I cannot believe this, as however many men pulled at the arm of a trebuchet they could not apply nearly the force that would be conveyed by the terrestrial gravitation of a heavy weight.