ent that is insignificant
compared to the advantages gained. Other cases may be cited in which
this method of increasing friction will probably be found useful,
aside from its application to railway purposes, but these will
naturally suggest themselves and need not be further dwelt upon.

In the course of the experiments above described, another and somewhat
different method of increasing the traction of railway motors has been
devised, which is more particularly adapted to electric motors for
street railways, and is intended to be used in connection with a
system of electric street railways now being developed by the author.
In this system _electro-magnetism_ provides the means whereby the
increase in tractive adhesion is produced, and this result is attained
in an entirely novel manner. Several attempts have heretofore been
made to utilize magnetism for this purpose, but apparently without
success, chiefly because of the crude and imperfect manner in which
most of these attempts have been carried out.

The present system owes its efficiency to the formation of _a complete
and constantly closed magnetic circuit_, moving with the vehicle and
completed through the two driving axles, wheels, and that portion of
the track rails lying between the two pairs of wheels, in a manner
similar to that employed in the electrical method before shown. We
have here a model of a second motor car equipped with the apparatus,
mounted on a section of track and provided with means for measuring
the amount of tractive force exerted both with and without the passage
of the current.

You will notice that each axle of the motor car is wound with a helix
of insulated wire, the helices in the present instance being divided
to permit the attachment to the axles of the motor connections. The
helices on both axles are so connected that, when energized, they
induce magnetic lines of force that flow in the same direction through
the magnetic circuit. There are, therefore, four points at which the
circuit is maintained closed by the rolling wheels, and as the
resistance to the flow of the lines of force is greatest at these
points, the magnetic saturation there is more intense, and produces
the most effective result just where it is most required. Now, when
the battery circuit is closed through the helices, it will be observed
that the torque, or pull, exerted by the motor car is fully twice that
exerted by the motor with the traction circuit open,