They were called “bombards,” and were mounted upon a wooden cradle or frame. Towards the end of the 14th century, they had become of large dimensions, firing heavy _stone_ shot of from 200 to 450 lbs. weight. All the shot were stone until, because they did not do sufficient damage in battering down a wall, it became the practice to bind and otherwise strengthen them with iron. The earliest cannon were of the rudest possible description. They were made of bars or thin sheets of iron, arranged longitudinally over a wooden core, in the form of a tube, around which were welded iron hoops to hold them together. In 1338 there existed breech-loading guns, with one or more movable chambers, to facilitate loading, but, even then, the fire was very slow; “three shots an hour was fair practice for a big bombard.” It is not certain when wheeled carriages were introduced, though mention is made of two-wheeled bombard carriages in 1376; but it must be remembered that the gun at first was looked upon as a substitute for the balista and other war machines employed in the siege of a fortified place. Its value as an effective and movable weapon on the battlefield was not realised for some time. The powder was fired at first by the insertion of a red-hot wire, but this was often very dangerous to the gunners, because the gun was so liable to burst. James II. of Scotland was killed by the bursting of a gun at the siege of Roxburgh in 1460. It became the custom, in the case of large bombards, for a small train of powder to be laid from the ground leading to the touchhole. The gunners fired the train, and then hastily betook themselves to a place of safety. The earliest known representation of a gun in England is contained in a MS., “De Officiis Regum,” at Christ Church, Oxford, of the time of Edward II. (1326). It shows a knight in armour, firing a short, primitive weapon, shaped something like a vase, and loaded with an incendiary arrow--that is, one charged with an inflammable substance. Firearms of this type were evidently very small, as only 2 lb. of gunpowder was provided for firing forty-eight arrows. From the beginning, contrivances had been made to resist the recoil of the gun when it was fired; heavy timbers, etc., were packed up against the breach to prevent the gun from flying backwards, but this plan often brought about the bursting of the gun. About the middle of the 15th century, trunnions (small cylinders of solid metal projecting from the sides, at right angles to the axis of the gun) were formed with the gun, and by means of these the recoil of the gun could be transferred to the carriage, and the pivoting of the gun up and down on the trunnions made the laying and sighting an easier task.