s and the other is
utilized as a part of the negative return of the power system.
Adjacent rails to be used for the latter purpose are bonded with two
copper bonds having an aggregate section of 400,000 c. m. These bonds
are firmly riveted into the web of the rail by screw bonding presses.
They are covered by splice bars, designed to leave sufficient
clearance for the bond.

The return rails are cross-sectioned at frequent intervals for the
purpose of equalizing currents which traverse them.

[Sidenote: _Contact Rail
Guard and
Collector Shoe_]

The Interborough Company has provided a guard in the form of a plank
8-1/2 inches wide and 1-1/2 inches thick, which is supported in a
horizontal position directly above the rail, as shown in the
illustration on page 113. This guard is carried by the contact
rail to which it is secured by supports, the construction of which is
sufficiently shown in the illustration. This type of guard has been in
successful use upon the Wilkesbarre and Hazleton Railway for nearly
two years. It practically eliminates the danger from the third rail,
even should passengers leave the trains and walk through a section of
the tunnel while the rails are charged.

Its adoption necessitates the use of a collecting shoe differing
radically from that used upon the Manhattan division and upon the
elevated railways employing the third rail system in Chicago, Boston,
Brooklyn, and elsewhere. The shoe is shown in the photograph on
page 114. The shoe is held in contact with the third rail by
gravity reinforced by pressure from two spiral springs. The support
for the shoe includes provision for vertical adjustment to compensate
for wear of car wheels, etc.

CHAPTER VI

ELECTRICAL EQUIPMENT OF CARS

In determining the electrical equipment of the trains, the company has
aimed to secure an organization of motors and control apparatus easily
adequate to operate trains in both local and express service at the
highest speeds compatible with safety to the traveling public. For
each of the two classes of service the limiting safe speed is fixed by
the distance between stations at which the trains stop, by curves, and
by grades. Except in a few places, for example where the East Side
branch passes under the Harlem River, the tracks are so nearly level
that the consideration of grade does not materially affect
determination of the limiting speed. While the majority of the curves
are of large radius, the