The wheel is somewhat like an overshot water-wheel, and does not touch any part of the case. It is turned by a jet of steam issuing from the steam-pipe of the boiler, into the exhausted case, through a tube, which is inclined in the direction of a tangent to the circumference of the wheel, so that the steam impinges against the buckets of the wheel and turns it round with great rapidity. The shaft of the wheel passes through stuffing-boxes at the centre of the circular case, and is supported externally by bearings.
Fig. 1 is an end view of the wheel, and a transverse section of the case, and Fig. 2 is a side view of the wheel, with the case in section; a is the engine shaft, b the revolving wheel, c the air-tight steam cases, d the steam pipe, e the throttle valve,/ the exhausting passage, opening into g the condenser, h the injection cock, i the cold water cistern. The exhausting apparatus is not shown.