From the small truck, _trochos_, or wheel on which it ran, the four-wheeled carriage which served for centuries as a mounting for the long guns of fighting ships has come to be known as a truck carriage: the gun, with trunnions cast upon it, as a truck gun. Artillery being from the first an affair common, in almost all respects, to land and to sea service, and being applied to ships as the result of its prior development on land, it would be expected that naval practice should in its evolution follow in the wake of that on land. And so it has, in the main, until the time of the Crimean War; since when, completely revolutionizing and in turn revolutionized by the rapid development of naval architecture and material, it has by far surpassed land practice both in variety and power. But while the wooden ship imposed its limitations no branch of affairs, perhaps, appeared to be more conservative in its practice than naval gunnery. No material seemed less subject to change, no service less inclined to draw lessons from war experience. And in recent years the truck carriage has often been taken as typifying the great lack of progress in all naval material which existed between the sixteenth and the nineteenth centuries. Whether there was in fact so great a stagnation as is commonly supposed, and to what causes such as existed may have been due, we may discern from an examination of the truck carriage itself and of its development from the earliest known forms of naval gun mounting. § The first large ordnance to be used on land, having as its object the breaching of walls and gates and the reduction of fortresses, was mounted solidly in the ground in a way which would have been impracticable on board a ship at sea. In time, as the energy of discharge increased, this method of embedding the gun in soil grew dangerous: a certain recoil was necessary to absorb and carry off the large stresses which would otherwise have shattered the piece. In time, too, as the power of explosives and the strength of guns increased, their size diminished; cannon, as we have seen, became more portable. No longer embedded in earth or fixed on ponderous trestles, they were transported from place to place on wheeled carriages. And on these carriages, massive enough to stand the shock of discharge and well adapted to allow a certain measure of recoil, the land ordnance were fired with a tolerable degree of safety. Both of these methods were followed in principle when guns came to be used at sea.