t when extra work has to be done the other
cylinders will be called into requisition by the opening of the steam
valves leading to them. Provision can be made for the automatic
working of this adjustment by the introduction of a spring upon the
piston-rod, so arranged that, as soon as the resistance reaches a
certain point, a lever is actuated which opens the valves to admit
steam to the reserve cylinders of the engine. On such occasions, of
course, the consumption of steam must necessarily be greatly
increased; but on the other hand the automatic system of the admission
to each cylinder also results in a shutting off of the steam when
little or no work is required. In fact, with a fully automatic action,
regulating the consumption of steam exactly according to the amount of
force necessary to drive the automobile, it would be possible to work
even a single cylinder to much greater advantage than is done by the
machines generally in use.

So heavy are the storage batteries needed for electric traction of the
road motor-car that practically it is not found convenient to carry
enough of cells to last for more than a twenty-mile run. The batteries
must then either be replaced, or a delay of some three hours must
occur while they are being recharged. The idea of establishing
charging stations at almost every conceivable terminus of a run is
quite chimerical; and, even if hundreds of such stations were
provided for the convenience of the users of electric traction, the
limitation imposed by being forced to follow the established routes
would always give to the non-electric motor an advantage over its
competitor.

The best hope for the storage battery on the automobile rests upon its
convenience as a repository of reserve power in conjunction with such
a prime motor as the steam-engine. A turbine worked by a jet of steam,
as already described, and moving in a magnetic field to generate
electricity for storage in a few cells, is a convenient form in which
steam and electricity can be yoked together in order to secure a power
of just the type suitable for driving an automobile. In the machine
indicated the supply of the motive power is direct from the storage
batteries, which can be coupled up in any required number according to
the exigencies of the road. Automatic gear may be introduced by an
adaptation of the principle already referred to.

In a light road-motor for carrying one or two persons on holiday trips
or busines