[13] 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 gravitation of a heavy weight. [Illustration: FIG. 18.--THE TREBUCHET. The arm is fully wound down and the tackle of the windlass is detached from it. The stone is in the sling and the engine is about to be discharged by pulling the slip-hook off the end of the arm. The slip-hook is similar to the one shown in fig. 10, p. 18. N.B.--A Roman soldier is anachronistically shown in this picture. The trebuchet was invented after the time of the Romans.] [Page 29] The trebuchet always had a sling in which to place its missile. The sling doubled the power of the engine and caused it to throw its projectile twice as far as it would have been able to do without it. It was the length of the arm, when suitably weighted with its counterpoise, which combined with its sling gave power to the trebuchet. Its arm, when released, swung round with a long easy sweep and with nothing approaching the velocity of the much shorter arm of the catapult. The weight of a projectile cast by a trebuchet was governed by the weight of its counterpoise. Provided the engine was of sufficient strength and could be manipulated, there was scarcely any limit to its power. Numerous references are to be found in mediæval authors to the practice of throwing dead horses into a besieged town with a view to causing a pestilence therein, and there can be no doubt that trebuchets alone were employed for this purpose. As a small horse weighs about 10 cwt., we can form some idea of the size of the rocks and balls of stone that trebuchets were capable of slinging. When we consider that a trebuchet was able to throw a horse over the walls of a town, we can credit the statement of Stella,[14] who writes ‘that the Genoese armament sent against Cyprus in 1376 had among other great engines one which cast stones of 12 cwt.’ [14] Stella flourished at the end of the fourteenth century and beginning of fifteenth. He wrote _The Annals of Genoa_ from 1298–1409. Muratori includes the writings of Stella in his great work, _Rerum Italicarum Scriptores_, 25 vols., 1723–38.