1712. Millar, M., [Sinclair, J. C.]. Jan. 25. Compound engines; valves and valve gear; starting.- Relates to engines in which the same steam is caused to do the double work of operating the piston both ways. Fig. 2 shows a section through the cylinder of a marine engine embodying the invention. The cylinder a is surrounded by a jacket or casing a' enclosing a space j, and at the ends is surrounded by annular valvechests k, k<1>. The former is the admission valvechest, and receives boiler steam at e, and the latter is the intermediate valvec h e s t and communicates with the space i. At the upper end of the cylinder is an exhaust chamber l, and at the lower end an exhaust chamber f The slide valves m, n are annular in form, and are connected together so as to be operated simultaneously by rods o. The steam cycle effected is as follows :- Steam is admitted to the lower end of the cylinder, and drives the piston b upwards ; the cut-off is made to occur at any desired point in the stroke, say, <5>/10 ths, and at, say, <5>/10 ths a portion of the steam under the piston is allowed to pass into the space j ; at <7>/10 ths of the stroke the communication of the space under the piston with the space is closed ; and at or beyond <9>/10 ths the steam under the piston is exhausted. During the down-stroke, the steam in the space j works expansively ; this steam is exhausted during the up-stroke. The valves are worked by levers q connected with the rods o by the joint shown in Figs. 9 and 10. The rods o are each made in two parts, the ends of which have recesses for the reception of segmental blocks o<6>. A flat part of the lever is placed between these blocks, and rings o<3>, 0<3> are then attached to the two parts of the rod, which are thereby connected. Wedges o<5> are provided for taking up slack in the joint. A portion of a locomotive embodying the invention is shown in Fig. 12. In this there are two cylinders A, B, each driving a single crank C. Provision is made for working these cylinders as ordinary double-acting cylinders when required. For this purpose, a pipe D connecting the two valve-chests is provided, also a pipe F connecting the space j with the exhaust pipe F<1>, and a valve ring H working over ports G connecting the valve-chest k' with the space j. The pipes D and F are each controlled by plug valves, which can be simultaneously actuated by a rod 0, which at the same time effects the extension of the valve ring H through the medium of a pinion and circular racks. The adjustment of these several valves results in boiler steam being supplied directly to each valve-chest, and gives a direct exhaust to each end of the cylinder.