This engine, exhibited at South Kensington by Fielding and Platt, of Gloucester, consists virtually of a universal joint connecting two shafts whose axes form an obtuse angle of about 157 degrees. It has four cylinders, two being mounted on a chair coupling on each shaft. The word cylinder is used in a conventional sense only, since the cavities acting as such are circular, whose axes, instead of being straight lines, are arcs of circles struck from the center at which the axes of the shafts would, if continued, intersect. The four pistons are carried upon the gimbal ring, which connects, by means of pivots, the two chair couplings.



Fig. 10 shows clearly the parts constituting the coupling, cylinders, and pistons of a compound engine. CC are the high-pressure cylinders; DD the low pressure; EEEE the four parts forming the gimbal ring, to which are fixed in pairs the high and low pressure pistons, GG and FF; HHHH are the chair arms formed with the cylinders carrying pivots, IIII, which latter fit into the bearings, JJJJ, in the gimbal ring. Figs. 1, 2, 3, 4 show these parts connected and at different points of the shaft's rotation. The direction of rotation is shown by the arrow. In Fig. 1 the lower high-pressure cylinder, C, is just about taking steam, the upper one just closing the exhaust; the low-pressure pistons are at half stroke, that in sight exhausting, the opposite one, which cannot be seen in this view, taking steam.

In Fig 2 the shaft has turned through one-eighth of a revolution; in Fig. 3, a quarter turn; Fig. 4, three-eighths of a turn. Another eighth turn brings two parts into position represented by Fig. 1, except the second pair of cylinders now replace the first pair. The bearings, KL, support the two shafts and act as stationary valves, against which faces formed on the cylinders revolve; steam and exhaust ports are provided in the faces of K and L, and two ports in the revolving faces, one to each cylinder. The point at which steam is cut off is determined by the length of the admission ports in K and L. The exhaust port is made of such a length that steam may escape from the cylinders during the whole of the return stroke of pistons.

Fig. 5 shows the complete engine. It will be seen that the engine is entirely incased in a box frame, with, however, a lid for ready access to the parts for examination, one great advantage being that the engine can be worked with the cover removed, thus enabling any leakage past the pistons or valve faces to be at once detected. The casing also serves to retain a certain amount of lubricant.

The lubrication is effected by means of a triple sight-feed lubricator, one feeder delivering to steam inlet, and two serving the main shaft bearings.

Figs, 6 and 7 are an end elevation and plan of the same engine. There is nothing in the other details calling for special notice.

Figs. 8 and 9 show the method of machining the cylinders and pistons, the whole of which can be done by ordinary lathes, which is evidently a great advantage in the event of reboring, etc., being required in the colonies or other countries where special tools are inaccessible.

Figs. 11 and 12 are sections which explain themselves.--The Engineer.