considerable
space of great value for other purposes. The installation of a steam
plant at the Intermediate Shafts, which were located in a high-class
residential district, would have been highly objectionable to the
neighboring property owners, on account of the attendant noise, smoke,
and dirt, and, in addition, the cost of the transportation of fuel would
have been a serious burden. Except for the forges and, toward the last,
the steam locomotives, not a pound of coal was burned on the work. The
use of the bucket and telpher also eliminated most of the objectionable
noise incident to the transfer of spoil from tunnel cars to ordinary
wagons at the shaft sites. Power plants were installed at the North
Shaft near First Avenue and at the rear of the 33d Street Intermediate
Shaft.

_First Avenue Plant._--Fig. 1, Plate LVIII, is a general view of the
First Avenue plant. The power-house at the corner of 34th Street and
First Avenue supplied compressed air for operating drills, shovels,
pumps, and hoists in the tunnels driven from the river shafts, and in it
three Laidlaw-Dunn-Gordon compressors were installed. The largest was a
32 by 20 by 30-in., two-stage, cross-compound, direct-connected to a
Fort Wayne 480 h.p., 230-volt, direct-current, constant-speed motor run
at 100 rev. per min. This compressor was rated at 2,870 cu. ft. of free
air per minute at a pressure of 100 lb. It was governed by throttling
the suction, the governor being controlled by the pressure in the air
receiver and the motor running continuously at a constant speed. The two
others were of similar type, one was 22-1/2 by 14 by 18-in., rated at
1,250 cu. ft. of free air at a pressure of 100 lb., the other was 16 by
10 by 18-in., rated at 630 cu. ft. They were fitted with 9-ft.
fly-wheels, and were driven at 150 rev. per min. by 105-h.p., General
Electric, 220-volt, compound-wound, direct-current motors running at 655
rev. per min. The larger of these two compressors was driven by two of
the motors belted in tandem, and the smaller was belt-connected to a
third motor. The compressors were water-jacketed and had small
inter-coolers, the water supply for which was itself cooled in a Wheeler
Condenser and Engineering Company's water-cooling tower. The pump and
the blower operating it were electrically driven.

The telphers, used for hoisting muck from the tunnels and for lowering
supplies, were each hung from single rails on a timber trestle, about
40 ft.