But perhaps the truck carriage may more properly be regarded as a derivative of the wheeled mounting on which, as we have seen, land ordnance came eventually to be worked. The ship being a floating fort, the mode of mounting the guns would be that in vogue in forts and garrisons ashore, and the land pieces and their massive carriages would be transferred, without modification, for use on shipboard. How different the conditions under which they worked! The great cannon, whose weight and high-wheeled carriages were positive advantages when firing from land emplacements, suitably inclined, were found to work at great disadvantage under sea conditions. Their great weight strained the decks that bore them, and their wheeled carriages proved difficult to control and even dangerous in any weather which caused a rolling or pitching of the gun platform. With the introduction of portholes their unfitness for ship work was doubtless emphasized; there was neither height nor deck-space enough to accommodate them between decks. Hence the necessity for a form of carriage suitable for the special conditions of sea service, as well as for a size of gun which would be within the capacity of a ship’s crew to work. In the early Tudor ships the forms of mounting were various: guns were mounted on two or four-wheeled carriages, or sometimes, especially the large bombards, upon “scaffolds” of timber.[91] By Elizabeth’s reign the limit had been set to the size of the gun; the demi-cannon had been found to be the heaviest piece which could be safely mounted, traversed, and discharged. This and the smaller guns which were plied with such effect against the Spanish Armada were mounted on low, wheeled, wooden carriages which were the crude models from which the truck carriage, the finished article of the nineteenth century, was subsequently evolved. Even then the carriages had parts which were similar and similarly named to those of the later truck carriage; they had trunnion-plates and sockets, capsquares, beds, quoins, axle-trees, and trucks.[92] On them the various pieces--the demi-cannons, the culverins, the basilisks and sakers--were worked by the nimble and iron-sinewed seamen; run out by tackles through their ports, and traversed by handspikes. Loaded and primed and laboriously fired by means of spluttering linstocks, the guns recoiled upon discharge to a length and in a direction which could not be accurately predicted. The smaller guns, at any rate, had no breechings to restrain them: these ropes being only used for the purpose of securing the guns at sea, and chiefly in foul weather.[93]