work developed at every stroke is varied by regulating the temperature
of the gas that fills the cylinder. When the temperature falls, the
pressure, and consequently the work developed, diminishes. This result
is obtained by varying the respective quantities of air that pass
through the fire box and around the piston. In measure as less air
passes through the fire box, the quantity that passes around the
piston augments by just so much, and the pressure diminishes. A valve,
_n'_, in the conduit that runs to the fire box is controlled by the
regulator, L', in the interior of the column. When the work to be
transmitted diminishes, the regulator closes the valve more or less,
and the work developed diminishes.

The coke is put by shovelfuls into a hopper, I. Four buckets mounted
upon the periphery of a wheel, I', traverse the coke, and, taking up a
piece of it, let it fall upon the cover, J, of the slide valve, _j_,
whence it falls into the cavity of the latter when it is uncovered,
and from thence into the conduit, _c'_, of the box, _j'_, when the
cavity of the valve is opposite the conduit. From the conduit, _c'_,
the coke falls upon the grate.

A small sight hole covered with glass, in the cover, J, permits the
grate to be seen when the cavity of the valve is opposite _c'_.

As in gas engines, a current of water is made to flow around the
cylinder, C', in order to keep the sides from getting too hot.

In order to set the engine in motion, we begin by opening the bottom,
C, of the cylinder, C', to clean the grate. This done, we close C and
introduce lighted charcoal through the conduit, _c'_ (the valve being
open). The valve is put in place, two or three revolutions are given