ls in circuit, even under the most unfavorable conditions of the
weather. In practice the primary current necessary is preferably
generated by a small high speed alternating dynamo on the locomotive,
the current being converted by means of an inductional transformer. To
avoid the necessity for electrically bridging the rail joints, a
modified arrangement may be employed, in which the electrical
connection is made directly with a fixed collar on the forward and
rear driving axles, the current dividing itself in parallel between
the two rails in such a manner that, if a defective joint exists in
the rail at one side, the circuit is still complete through the rail
on the other; and as the rails usually break joints on opposite sides,
this arrangement is found very effective. The insulation of the
driving wheels is very easily effected in either case.

As the amount of additional tractive adhesion produced depends upon
the _quantity_ of current flowing rather than upon its pressure, the
reason for transforming the current as described will be apparent, and
its advantages over a direct current of higher tension and less
quantity, both from an economical and practical standpoint, will for
this reason be clear. The amount of heat produced at the point of
contact between the wheels and rails is never large enough to injure
or otherwise affect them, although it may be quite possible to
increase the current sufficiently to produce a very considerable
heating effect. The amount of current sent through the traction
circuit will of course vary with the requirements, and as the extent
to which the resistance to slipping may be increased is very great,
this method is likely to prove of considerable value. While in some
cases the use of such a method of increasing the tractive power of
locomotives would be confined to ascending gradients and the movement
of exceptionally heavy loads, in others it would prove useful as a
_constant_ factor in the work of transportation. In cases like that of
the New York elevated railway system, where the traffic during certain
hours is much beyond the capacity of the trains, and the structure
unable to support the weight of heavier engines, a system like that
just described would prove of very great benefit, as it would easily
enable the present engines to draw two or three additional cars with
far less slipping and lost motion than is the case with mechanical
friction alone, at a cost for tractive curr