The accompanying illustration represents an ingenious rotary engine, which we have copied, and translated the description from Dingler's Polytechnic Journal published at Augsburg, Germany. The cylinder of this engine requires no boring out, there is no piston, no slide or exhaust valve, and, in fact, no sliding friction—the friction of the journals excepted. Oti the shaft which carries the fly wheel, A, a pulley, B, with two projecting flanges, is rigidly fastened, and between the two flanges an india rubber tube is placed all round the pulley, B ; one end of the tube is closed by a plate, C, while the other end communicates with an opening, E, in the side of the pulley. A roller, F, presses the tube down, so that no steam can escape between the roller and the pulley. If steam is admitted between the roller, F, aiid the plate, C, the pulley, B, begins to revolve, and the plate, C, recedes from the roller, F, until the whole tube is filled with steam. As soon as the roller comes on the top of the plate, C, the steam from the tube escapes through the exhaust port, E, and so enables the wheel to keep on rotating. Steam is admitted through an arm, D, and it is hardly necessary to state that the shaft is hollow, except that part on which the pulley, B, is fastened; and one end connects with the steam pipe, while the other serves to exhaust. In order to lessen the friction, the roller, F, can be made to press from below. We illustrated a pump which worked on this same principle on page 324, Volume XI, Scientific American.