three-drum, steam-driven, Lambert, hoisting engine. This engine was
later changed to the derrick on the south side of the dock, and a
motor-driven Lambert engine from that derrick was substituted.

Eight electric telphers.

Ninth Avenue Twin-Tunnels Plant.

One stiff-leg derrick, previously used in retaining-wall work.

One Smith concrete mixer, 1 cu. yd. capacity, driven by attached air
engine.

Two cableways taken from the retaining-wall plant and used for mucking
out the tunnels after the center pier had been built; driven by air
supplied to the original engine.

One Robbins belt conveyor, driven by a 30-h.p. engine run by air.

Three 1-cu. yd. Hopple dump-cars.


CONSTRUCTION.

Ground was broken for work under the principal contract on July 9th,
1904, on which date the contractor began cutting asphalt for Trench No.
1 in 31st Street, and also began making a roadway from Ninth Avenue into
the pit just south of 32d Street.

_Excavation for Retaining Walls._--Two essentially different methods