alternately put in communication with the receptacle and with a
discharge outlet. In this passage are fixed a number of wire gauze
screens or pieces of metal with interstices. These constitute a
regenerator of heat, and also prevent a communication of flame from the
cylinder to the receptacle. In the upper end of the cylinder or of the
piston shield are provided electrodes which give an electric spark, or
a platinum wire which is rendered incandescent by a current from an
inductor or other source of electricity to ignite the combustible charge
of the cylinder. After the engine has been for some time at work,
the heat at the upper part of the cylinder may suffice for effecting
ignition without provision of other means for this purpose.

In combining such an engine with means for generating the combustible
gas, a gas producer is employed. In this producer a current of heated
air is introduced into the heart of a body of kindled fuel, and
the gases produced--partly by distillation and partly by imperfect
combustion of the fuel--are conveyed to the gas inlet of the cylinder
or pump of the engine. As the gas in leaving the producer is hot, it is
caused to pass through regenerating apparatus, to which it delivers a
large portion of its heat before it reaches the engine, and the air
which supplies the producer is made to pass through this regenerating
apparatus so as to take up the heat abstracted from the gas.

In the accompanying engravings, Fig. 1 shows a front elevation (partly
in section) of a pair of engines constructed according to this
invention. The lower part, A, of each cylinder is cooled by water
circulating through its casing. The upper part, B, is lined with
refractory material, such as fire-clay. The trunk piston, C, is made
hollow, and formed with a shield covered by refractory material to
protect the packing of the piston and the surface of the lower part of