145th
Street on the West Side, two from 145th Street to Dyckman Street, and
three from Dyckman Street to the northern terminal of the West Side
extension of the system. From 96th Street, the East Side has two
tracks and two contact rails to Mott Avenue, and from that point to
the terminal at 182d Street three tracks and three contact rails.

[Illustration: CONTACT SHOE AND FUSE]

Contact rails south of Reade Street are supplied from sub-station No.
11; from Reade Street to 19th Street they are supplied from
sub-stations Nos. 11 and 12; from 19th Street they are supplied from
sub-stations Nos. 12 and 13; from the point last named to 96th Street
they are supplied from sub-stations Nos. 13 and 14; from 96th Street
to 143d Street, on the West Side, they are supplied from sub-stations
Nos. 14 and 15; from 143d Street to Dyckman Street they are supplied
from sub-stations Nos. 15 and 17; and from that point to the terminal
they are supplied from sub-station No. 17. On the East Side branch
contact rails from 96th Street to 132d Street are supplied from
sub-stations Nos. 14 and 16; from 132d to 165th Street they are
supplied from sub-stations Nos. 16 and 18; and from 165th Street to
182d Street they are supplied from sub-station No. 18.

Each contact rail is insulated from all contact rails belonging to
adjacent tracks. This is done in order that in case of derailment or
other accident necessitating interruption of service on a given track,
trains may be operated upon the other tracks having their separate and
independent channels of electrical supply. To make this clear, we may
consider that section of the subway which lies between Reade Street
and 19th Street. This section is equipped with four tracks, and the
contact rail for each track, together with the direct current feeders
which supply it from sub-stations Nos. 11 and 12, are electrically
insulated from all other circuits. Of each pair of track rails one is
used for the automatic block signaling system, and, therefore, is not
used as a part of the negative or return side of the direct current
system. The other four track rails, however, are bonded, and together
with the negative feeders constitute the track return or negative side
of the direct current system.

The diagram on page 109 illustrates the connections of the contact
rails, track rails and the positive and negative feeders. All negative
as well as positive feeders are cables of 2,000,000 c. m. section and