But small progress was made. One reason alleged was that the shape of hull which the Surveyor had made peculiarly his own was ill-adapted for steam machinery. “Nothing more unpropitious,” observed a later writer, “for Sir William Symond’s mode of construction than the introduction of steam can be conceived. His sharp bottoms were the very worst possible for the reception of engines; his broad beam and short length the most unfavourable qualities that could be devised for steam propulsion. As much as he could, he adhered to his principles.... Rather than yield to the demands of the new power, he sacrificed the armaments of his vessels, kept down the size of their engines, and recklessly exposed the machinery to shot should they go into action.”[149] There doubtless was something in this criticism. And yet, as we have seen, experience in America led to a form of hull for paddle steamers in many respects approaching that condemned as being favoured by the Surveyor! Another and more valid reason for the slow progress made lay in the inherent unsuitability of the paddlewheel steamer as a substitute for the large sailing warship. Not only did the paddlewheels offer a large and vulnerable surface to destruction by enemy shot, but the wheels and their machinery could not be embodied in a ship design without interference with its sails and sailing qualities and, still more, without serious sacrifice of broadside armament. The machinery monopolized a large section of the midship space, the huge wheels covered the sides and interfered with the training of those guns for which room remained. The problem of arming steam-vessels was novel and difficult of solution. The guns must be few and therefore powerful. Hence it appeared that paddlewheel steamers, notwithstanding the advantages they possessed of speed and certainty of motion, could only sustain a small concentrated armament, consisting of the heaviest and most powerful ordnance: guns of large calibre, which possessed large power of offence at ranges where the broadside cannon would be deprived of much of their efficiency. Hence in ’31 a 10-inch shell gun of 84 hundredweight was expressly designed and cast for this purpose; and all the classes of steamers in early use in the navy were armed with it until, in ’41, it was displaced by the 68-pounder pivot gun, which then became the principal pivot gun of the service. Thus the development of paddlewheel machinery reacted on the development of artillery. The steamer was a stimulus to the development of large ordnance worked on the pivot system. And this form of armament in turn influenced the form of the ship. The main weights--those of the propelling machinery--were already concentrated in the waist of the vessel, and it was now possible so to place the few pivot guns that the ends of the vessel were left very lightly loaded. Thus it was possible to give unprecedentedly fine lines to the new steamers, a sharp and