[Sidenote:  Cranes, Shops, Etc.]

The power house is provided with the following traveling cranes:  For the operating room:  One 60-ton electric traveling crane and one 25-ton electric traveling crane.  For the area over the oil switches:  one 10-ton hand-operated crane.  For the center aisle of the boiler room:  one 10-ton hand-operated crane.  The span of both of the electric cranes is 74 feet 4 inches and both cranes operate over the entire length of the structure.

The 60-ton crane has two trolleys, each with a lifting capacity, for regular load, of 50 tons.  Each trolley is also provided with an auxiliary hoist of 10 tons capacity.  When loaded, the crane can operate at the following speeds:  Bridge, 200 feet per minute; trolley, 100 feet per minute; main hoist, 10 feet per minute; and auxiliary hoist, 30 feet per minute.  The 25-ton crane is provided with one trolley, having a lifting capacity, for regular load, of 25 tons, together with auxiliary hoist of 5 tons.  When loaded, the crane can operate at the following speeds:  bridge, 250 feet per minute; trolley, 100 feet per minute; main hoist, 12 feet per minute; and auxiliary hoist, 28 feet per minute.

The power house is provided with an extensive tool equipment for a repair and machine shop, which is located on the main gallery at the northerly side of the operating room.

[Illustration:  5,000 K. W. ALTERNATOR—­MAIN POWER HOUSE]

CHAPTER V

SYSTEM OF ELECTRICAL SUPPLY

[Sidenote:  Energy from Engine Shaft to Third Rail]

The system of electrical supply chosen for the subway comprises alternating current generation and distribution, and direct current operation of car motors.  Four years ago, when the engineering plans were under consideration, the single-phase alternating current railway motor was not even in an embryonic state, and notwithstanding the marked progress recently made in its development, it can scarcely yet be considered to have reached a stage that would warrant any modifications in the plans adopted, even were such modifications easily possible at the present time.  The comparatively limited headroom available in the subway prohibited the use of an overhead system of conductors, and this limitation, in conjunction with the obvious desirability of providing a system permitting interchangeable operation with the lines of the Manhattan Railway system practically excluded tri-phase traction systems and led directly to the adoption of the third-rail direct current system.

[Illustration:  SIDE AND END ELEVATIONS OF ALTERNATOR.]

[Illustration:  SIDE ELEVATION AND CROSS SECTION OF ALTERNATOR WITH PART CUT AWAY TO SHOW CONSTRUCTION.]