[Illustration: _Summoning the Castle._] But the assailed may succeed in throwing down the ladders; or in beating the enemy off them by hurling down great stones ready stored against such an emergency, or heaving the coping-stones off the battlements; or they may succeed in preventing the assailants from effecting a lodgment on the wall by a hand to hand encounter; and thus the assault may be foiled and beaten off. Still our mediæval captain has other resources; he will next order up his "gyns," _i.e._ engines of war. The name applies chiefly to machines constructed for the purpose of hurling heavy missiles. The ancient nations of antiquity possessed such machines, and the knowledge of them descended to mediæval times. There seems, however, to be this great difference between the classical and the mediæval engines, that the former were constructed on the principle of the bow, the latter on the principle of the sling. The classical _ballista_ was, in fact, a huge cross-bow, made in a complicated way and worked by machinery. The mediæval _trebuchet_ was a sling wielded by a gigantic arm of wood. In mediæval Latin the ancient name of the ballista is sometimes found, but in the mediæval pictures the principle of the engines illustrated is always that which we have described. We meet also in mediæval writings with the names of the _mangona_ and _mangonella_ and the _catapult_, but they were either different names for the same engine, or names for different species of the same genus. The woodcut here introduced from the MS. Add. 10,294, f. 81 V., gives a representation of a trebuchet. A still earlier representation--viz., of the thirteenth century--of machines of the same kind is to be found in the Arabic MS. quoted in a treatise, "Du feu Grégois," by MM. Favé and Reinaud, and leads to the supposition that the sling principle in these machines may have been introduced from the East. There are other representations of a little later date than that in the text (viz., about A.D. 1330) in the Royal MS. 16 G. VI., which are engraved in Shaw's "Dresses and Decorations." We also possess a contemporary description of the machine in the work of Gilles Colonne (who died A.D. 1316), written for Philip the Fair of France.[379] "Of _perriers_," he says, "there are four kinds, and in all these machines there is a beam which is raised and lowered by means of a counterpoise, a sling being attached to the end of the beam to discharge the stone. Sometimes the counterpoise is not sufficient, and then they attach ropes to it to move the beam." This appears to be the case in our illustration. The rope seems to be passed through a ring in the platform of the engine, so that the force applied to the rope acts to the greater advantage in aid of the weight of the beam. "The counterpoise may either be fixed or movable, or both at once. In the fixed counterpoise a box is fastened to the end of the beam, and filled with stones or sand, or any heavy body."