----
Total, 37 393

The total number of signals, both block and interlocking, is as follows:

Home signals, 354
Dwarf signals, 150
Distant signals, 187
----
Total, 691
Total number of switches, 224

It will be noted that in the case of the City Hall Station three
separate plants are required, all of considerable size, and intended
for constant use for a multiplicity of movements. It is, perhaps,
unnecessary to state that all the mechanism of these important
interlocking plants is of the most substantial character and provided
with all the necessary safety appliances and means for rapidly setting
up the various combinations. The interlocking machines are housed in
steel concrete "towers," so that the operators may be properly
protected and isolated in the performance of their duties.

CHAPTER X

SUBWAY DRAINAGE

The employment of water-proofing to the exterior surfaces of the
masonry shell of the tunnel, which is applied to the masonry, almost
without a break along the entire subway construction, has made it
unnecessary to provide an extensive system of drains, or sump pits, of
any magnitude, for the collection and removal of water from the
interior of the tunnel.

On the other hand, however, at each depression or point where water
could collect from any cause, such as by leakage through a cable
manhole cover or by the breaking of an adjacent water pipe, or the
like, a sump pit or drain has been provided for carrying the water
away from the interior of the tunnel.

For all locations, where such drains, or sump pits, are located above
the line of the adjacent sewer, the carrying of the water away has
been easy to accomplish by employing a drain pipe in connection with
suitable traps and valves.

In other cases, however, where it is necessary to elevate the water,
the problem has been of a different character. In such cases, where
possible, at each depression where water is liable to collect, a well,
or sump pit, has been constructed just outside the shell of the
tunnel. The bottom of the well has been placed lower than the floor of
the tunnel, so that the water can flow i