The boilers are shown in the inboard profile about as described and drawn by Marestier but with two stacks on each boiler, one to each flue; Marestier's sketch in his report on American steamships shows the flues of each boiler trunked into a single stack. The battery had two boilers and the stacks are at the boilers' fire-door end. The steam lines came off the crown of the boilers and probably passed through the ends of the wheelbox to the engine; a trunk for the steam lines would undoubtedly have been necessary.
[Illustration: Figure 15.--SKETCH OF 130-GUN SHIP proposed by Patrick Miller to King Gustav III of Sweden in 1790. In Statens Sjöhistoriska Museum, Stockholm.]
[Illustration: Figure 16.--PATRICK MILLER'S manually propelled (paddle-wheel) catamaran ship _Experiment_, built at Leith, Scotland, 1786. Scale drawing in Statens Sjöhistoriska Museum, Stockholm.]
The engine is shown to have had counterbalanced side levers, one on each side, and a single flywheel on the outboard side. The cylinder is over the condenser or "cistern," connected by the steam line and valve box on the side. The cylinder crosshead is shown in the inboard profile to have reached the underside of the beams of the upper deck. The crosshead was connected by two connecting rods to the side levers. These levers operated the paddle wheel by connecting rods to cranks on the paddle-wheel shaft. There is another pair of connecting rods from the side levers to the crosshead of the air pump. All connecting rods are on one arm of the side levers, the other end having only a counterbalance weight beyond the fulcrum bearing. The flywheel has a shaft fitted with two gears, and is driven through idler gears from gears on the paddle-wheel shaft; it turns at about twice the speed of the paddle wheel. No other pumps or fittings are shown in the engine hull, although manual pumps were probably fitted to fill and empty the boilers. Piping is not shown.
[Illustration: Figure 17.--PAINTING OF THE _Experiment_ in the Statens Sjöhistoriska Museum, Stockholm.]
The four rudders, toggled in pairs, are shown in both the lines and inboard drawings, but the shape is different in the two plans. Operation must have been by a tiller under the gun-deck beams. The outer end of the tiller may have been pivoted on the toggle bar and the inboard end fitted, as previously described, with steering cable or chain tackles. This seems to be the only practical interpretation of the evidence.