there is a movable piece, K, which, pressing against the rim, renders
steam-tight the channel in which the pistons move when driven by the
steam. At the extremities of this channel there are plates which
are kept pressed against the wheel by means of spiral springs, thus
rendering the channel perfectly tight.

The steam enters the closed space (which forms one-fourth of the
circumference) through the slide-valve, S, presses against the pistons,
d, and causes the wheel to revolve in the direction of the arrows.
The slide-valve is closed by the action of the external distributing
mechanism, the piston passes beyond the steam-outlet, A, and a new
piston then comes in play. Altogether, there are six of these pistons,
each one working in an aperture in the rim, and kept pressed outwardly
by means of a spiral spring. The steam acts constantly on the same lever
arm and meets with no counter-pressure. The other defects, likewise, of
the ordinary steam engines in use are obviated to such an extent that
the effective power of the steam-wheel is 50 per cent, greater than that
of other and more complicated machines--at least this is the experience
of the inventor.

[Illustration: IMPROVED STEAM-WHEEL.]

To the inner ends of the pistons there are attached rods which
pass through the rim of the wheel (where they are provided with
stuffing-boxes) and abut against spiral springs. These rods are, in
addition, connected with levers, h, which are pivoted on the spokes of
the wheel, and whose other extremities carry rods, 2. These latter run
through guides on the external face of the rim of the wheel and engage
by means of friction-rollers, in an undulating groove formed in the
inner surface of the jacket. When a piston arrives in front of the upper