to the axle by means of an endless chain. On this axle are three conical
gear wheels, two of which are furnished with hooked teeth, and the third
with wooden projections and fixed permanently in place. This arrangement
enables the engine to be moved forward or backward according as it is
thrown in right or left gear. When the conical pinions are thrown out of
gear, the motive force is no longer applied to the axle, and by the aid of
the brakes the engine may be instantly stopped. The movement of the pinions
is effected by two sets of wheels on each of the platforms of the engine,
and near the door for the conductor. By turning one of the wheels to the
right or left on either platform, the conductor imparts either the less or
the greater speed to the engine. In case he has caused the engine to move
forward by turning the second wheel, he will not have to touch it again
until the end of the trip. The brake, which is also operated from the two
platforms, is applied to all four wheels at the same time. From this
arrangement it is seen that the movement is continuous. Nevertheless, the
conductor has access to the regulator by a small chain connected with the
outside by a wheel near at hand, but the action is sufficiently regular not
to require much attention to this feature.

[Illustration: GAS ENGINE FOR USE ON RAILROADS.]

The gas is produced by the Wilford apparatus, which regularly furnishes the
requisite quantity necessary for an explosion, which is produced by a
particular kind of light placed near the piston. The vapor is produced by
passing hot water from the envelope of the cylinder of the motor through
the Wilford apparatus. The water is cooled again in a reservoir (system
Koerting) placed in direct communication with the cylinder. Any permanent
heating is therefore impossible.

The noise of the explosions is prevented by a device invented by Mr.