the ground below the bottom of the well,
and the water is elevated by the air producing a rising column of
water of less specific weight than the descending column of water
which is in the pipe extending below the bottom of the sump well.

In the case of Nos. 3 and 5 sumps, and for Location No. 1, automatic
air-operated ejectors have been employed, for the reason that the
conditions did not warrant the employment of air lifts or electric or
air-operated pumps.

In the case of Nos. 6, 8, 9, and 10 sumps and for Locations Nos. 2, 4,
and 5, air-operated reciprocating pumps will be employed. These pumps
will be placed in readily accessible locations, where air lifts could
not be used, and this type of pump was selected as being the most
reliable device to employ.

In the case of Location No. 3, where provision has to be made to
prevent a large amount of yard drainage, during a storm, from entering
the tunnel where it descends from the portal, it was considered best
to employ large submerged centrifugal pumps, operated by reciprocating
air engines. Also for the portal, at Location No. 6, similar
centrifugal pumps will be employed, but as compressed air is not
available at this point, these pumps will be operated by electric
motors.

The air supply to the air-operating pumping devices will be
independent from the compressed air line which supplies air to the
switch and signal system, but break-down connections will be made
between the two systems, so that either system can help the other out
in case of emergency.

A special air-compressor plant is located at the 148th Street repair
shop, and another plant within the subway at 41st Street, for
supplying air to the pumps, within the immediate locality of each
compressor plant. For the more remote pumps, air will be supplied by
smaller air compressors located within passenger stations. In one
case, for the No. 2 sump, air will be taken from the switch and signal
air-compressor plant located at the No. 11 sub-station.

CHAPTER XI

REPAIR AND INSPECTION SHED

While popularly and not inaccurately known as the "Subway System," the
lines of the Interborough Company comprise also a large amount of
trackage in the open air, and hence the rolling stock which has
already been described is devised with the view to satisfying all the
peculiar and special conditions thus involved. A necessary corollary
is the requirement of adequate inspection and repair shops, so that