The transport of the heavy and cumbrous guns of the fourteenth century was found to be attended with so much difficulty and expense that lighter cannon were introduced in the century following for field use, and rude carriages on wheels drawn by oxen were added. The bombard thus mounted was called “cerbotana ambulatoria.” Gun carriages were vastly improved during the reign of Henry VIII., when horses were employed to draw them. Means of sighting and convenience for trajectory had to be thought of, and trunnions were invented towards the middle of the fifteenth century. There was another contrivance for raising and depressing by means of a long thin prolongation, a sort of tail in fact, attached to the piece behind, and a fork was sometimes used for holding up the breech. There is a specimen with this adjustment at the Musée d’Artillerie at Paris, with an inscription bearing the date 1490. Projectiles of iron did not become common until a little later, but there was nothing specially new in a metal projectile, for such had long been used for early war engines, throwing balls both cold and hot. The English army before Orleans in 1428 had a train of fifteen breech-loading mortars. Valturio, an Italian, writing in 1472 describes the engines of war then in use, including cannon. Specimens of ancient ordnance are not very numerous in England. There is a very interesting wrought-iron bombard in the collection at the Rotunda, Woolwich, dating from the commencement of the fifteenth century, or possibly somewhat earlier. It is lined with cast-iron,[52] has a calibre of 15.1 inches; interior diameter of chamber, 14 inches; capacity of chamber, about 3.5 lb.; length of chase, 34 inches; present weight, 6 cwts. Also a wrought-iron cannon of about the same date--length, 24 inches; original calibre about 2 inches, without trunnions or cascabel, but provided with a couple of rings for transportation. Double cannon, strengthened with coils, were common at this period, with the breech in the centre, and barrels running in two opposite directions. There are specimens at Woolwich, and at the Porte de Hal Museum, Brussels. There are several wrought-iron pieces at Woolwich, of the reign of Henry VI., and among them a serpent gun 8 feet 6 inches long, without trunnions, but provided with two rings for lifting--calibre, 4.25 inches; weight, about 9 cwts. A wrought-iron breech-loading gun with carriage was recovered from the wreck of the _Mary Rose_, sunk off Spithead in 1545, which is now at Woolwich; original calibre about 8 inches; the gun is a tube 9 feet 8 inches long, strengthened by a succession of heavy hoops, and is fixed by iron bolts to a beam of wood. The breech-block being removed for loading and charge inserted, the block is replaced and wedged, and the recoil was sustained by an upright piece of wood. There is no arrangement visible for raising or lowering the gun for taking aim. Similar guns may be seen at the Tower.