As for this quoin or primitive wedge by which the gun was roughly laid, this had a great advantage over the screw (which gained a footing, as an alternative, when the carronade came into use) in that it allowed of rapid changes of elevation of the gun. Hence, though the quoin was liable to jump from its bed on gunfire and do injury to the crew, it kept its place as an accessory almost as long as the truck carriage itself survived. There was one advantage possessed by the truck carriage which was perhaps the most important of all: its superior transportability. The gun equipment was easily transferable, and what this meant to the seaman may be gathered from the accounts of the way in which, in sailing-ship days, ships’ armaments were continually being shifted. The armament, we have noted, was not embodied, as it is to-day, as an integral part of the design of the ship. The guns and their carriages were in the nature of stock articles, which could be changed in size, number and position according to the whim of the captain or the service of the ship. And there was every reason why all parties concerned, and especially the ordnance people, should tend to standardize the forms of guns and carriages, to keep them self-contained and as independent as possible of the special requirements of individual ships or positions. The shifting of guns was constantly going on in a commissioned ship. At sea they were lashed against the sides so as to leave as clear a deck as possible. In chase a shifting of guns, among other heavy weights, was resorted to in order that the vessel should not lose way by plunging heavily. If she set sail on a long voyage some of the guns were struck down into the hold, to stiffen her and give her an increased stability. And on her return to harbour the guns might be removed for examination and repair by the ordnance officials, the ship being laid alongside a sheer hulk for the purpose. In the days before the sheathing of ships’ bottoms was successfully practised, and in the absence of docks, it was constantly necessary to careen ships for the repair of their ground-timbers, for the cleaning of their sides and the caulking of their seams. This, again, necessitated a shifting or complete removal of most of their stores and ordnance. Great advantages were offered, therefore, from having gun-carriages compact, self-contained, and capable of being quickly removed from one place to another. § Having inspected the truck carriage in some detail, let us now briefly glance at the development of its use which took place in the last hundred years of its service, between the middle of the eighteenth and the middle of the nineteenth centuries.