153

General Description .

from the engine-room ; and by this plan a consider-able saving in the height of the engine-house isalso effected.

We have already stated that Mr. Watt’s greatimprovement consisted in condensing the steamin a separate vessel : the internal part of thecylinder being kept at the temperature of boilingwater, so that the continued waste of steam, andconsequently of fuel, that occurred by forming avacuum beneatli the piston in the atmosphericengine, was in this case avoided.

The nature of this improvement will be best un-derstood by reference to the Single-acting Engine,that forms the subject of Plafelll. in w'hich a repre-sents the boiler, enclosed in a casing of brick work.

h. The steam-pipe, connecting the cylinder cw’ith the boiler.

c. The cylinder, firmly attached to the floor ofthe engine-room by the bolts d d, and having itsupper end enclosed by the cap e, through whichthe piston-rod is made to work air-tight.

f.g. The beam, working on its axis or fulcrumat h, the socket in which the axis revolves restinsron the floor and wall i.

j. The pump-rod, suspended at the end g ofthe working-beam.

k. The piston-rod, connected by the parallelmotion at f with the working-beam fg.

in. The condensing cistern, containing the air-pump n, the condenser, and hot-well o : a con-