. grade, whereas with the traction circuit open it slips down
in very short order, notwithstanding the efforts of the driving
mechanism to propel it up.

The resistance of the helices on this model is less than two ohms, and
this will scarcely be exceeded when applied to a full sized car, the
current from two or three cells of secondary batteries being probably
sufficient to energize them.

The revolution of the driving axles and wheels is not interfered with
in the slightest, because in the former the axle boxes are outside the
path of the lines of force, and in the case of the latter because each
wheel practically forms a single pole piece, and in revolving presents
continuously a new point of contact, of the same polarity, to the
rail; the flow of the lines of force being most intense through the
lower half of the wheels, and on a perpendicular line connecting the
center of the axle with the rail. In winter all that is necessary is
to provide each motor car with a suitable brush for cleaning the track
rails sufficiently to enable the wheels to make good contact
therewith, and any tendency to slipping or skidding may be effectually
checked. By this means it is easily possible to increase the tractive
adhesion of an ordinary railway motor from 50 to 100 per cent.,
without any increase in the load or weight upon the track; for it must
be remembered that even that portion of the increased friction due to
direct attraction does not increase the weight upon the roadbed, as
this attraction is mutual between the wheels and track rails; and if
this car and track were placed upon a scale and the circuit closed, it
would not weigh a single ounce more than with the circuit open.

It is obvious that this increase in friction between two moving
surfaces can also be applied to _check_, as well as augment, the
tractive power of a car or train of cars, and I have shown in
connection with this model a system of braking that is intended to be
used in conjunction with the electro-magnetic traction system just
described. You will have noticed that in the experiments with the
traction circuit the brake shoes here have remained idle; that is to
say, they have not been attracted to the magnetized wheels. This is
because a portion of the traction current has been circulating around
this coil on the iron brake beam, inducing in the brake shoes
magnetism of like polarity to that in the wheels to which they apply.
They have therefore been _r