Illustration: PLATE LVIII, FIG. 3.--HEADWORKS AT 33D STREET:
INTERMEDIATE SHAFT.]

[Illustration: PLATE LVIII, FIG. 4.--LOADING SPOIL ON BARGES, 35TH
STREET PIER.]

A concrete-mixing plant was placed in each shaft, the mixer being
located high enough to discharge into cars at about the level of the
springing line of the arch. Above the mixers were the measuring
hoppers set in the floor of a platform which was large enough to carry
half a day's supply of cement. At the South Shaft the cement was
delivered to this floor from the loading platform through a spiral steel
chute; at the North Shaft it was lowered in buckets by the telpher. The
sand and stone were drawn into the hoppers through short chutes from the
base of the storage bins which occupied the remaining height of the
shaft--about 50 ft. At the South Shaft the bins were of concrete and
steel, about 6 by 12 ft. in section, and attached to the central wall of
the caisson. Sand and stone were delivered into them from dump-wagons on
the loading platform. At the North Shaft steel-plate bins were used, and
were supplied with material by the buckets handled by the telpher. The
mixers were No. 5 Smith, belt-connected to 25-h.p. motors, and about 0.8
cu. yd. of concrete was mixed at a batch. The concrete cars were steel
side-dumpers of the Wiener or Koppel type.

In order to be able to continue concreting during the winter, when
neither sand nor stone could be obtained by water, practically all the
space under the loading platforms in the South Shaft yards not occupied
by the blacksmith shop was filled with these materials, which were
placed in storage in the late fall.

_Intermediate-Shaft Plant._--The air-compressing plant was located at
the rear of the 33d Street Intermediate Shaft, and supplied air for
driving the tunnels east and west from the Intermediate Shafts on both
32d and 33d Streets. Two compressors, the same as the large
Laidlaw-Dunn-Gordon machine at First Avenue, were installed here, with a
similar water-cooling tower.

Both shafts were on private property, owned by the Railroad Company, on
the north side of the streets, and each was equipped with two telphers
supported on timber trestles, similar to those at First Avenue. Here,
however, the buckets were placed on wagons standing at the curb, as
shown by Fig. 3, Plate LVIII.

Blowers for ventilation were installed at each shaft, as at First
Avenue, and, after the excavation had proceeded some distan