This arrangement resembles the preceding one by Messrs. Maudslay and Field in the circumstance of each engine being composed of two cylinders, but in all other respects it is different. The cylinders in this engine are inverted, and the four cylinders composing the pair of engines are ranged in a line across the vessel. The engraving shows a transverse section of a portion of one side of the vessel, with an end view of the engines. At a a are the cylinders, standing upon four strong wrought-iron columns, only one of which is shown, in order to bring the piston-rods into view. The columns rest on, and are secured to, the foundation plate c; and passing through suitable bosses on the sides of the cylinders support the entablature plate d, and the crank pedestals above. The cylinders are placed at a sufficient height from the bottom of the vessel, to allow the piston-rods to work downwards. The two piston-rods f f are connected fig. 2.
together by n cross-liead g; the stuffing-boxes e e are of double form, or in other words they have a space for packing both at top and bottom, being furnished with self-acting oil cups for lubricating the rods. The power is transmitted directly from the main cross-head g below to the cranks h h above the cylinders, by the connecting rod i; the two piston-rodsff, and the connecting cross-head g, are further secured and made to work uniformly together by means of a strong vibrating frame k of cast iron, forming part of the parallel motion; and which, with the side levers l, serves also to work the air-pump as well as the feed, bilge, and brine-pumps. Each cylinder is furnished with a separate slide valve, the two being connected together by a cross-head, worked by one eccentric motion. The object of thus dividing the valve is to shorten the lengths of the steam ports; the valves being brought much closer up to the face of their respective cylinders than would be the case if one only were used for both. The condenser is placed immediately underneath the slide valve case, and the air-pump, foot, and discharge-valves, are similar in construction to those of ordinary engines. The air-pump and condenser are connected together by a passage underneath the foundation plate.