y and not quite as hard or dry as that in 33d Street, and timbering
was required for practically the full depth to the crown of the drift.
Sinking was started on May 15th, 1905, and was completed on October
26th, 1905. The daily average rate was 0.30 ft. in earth and 0.52 ft. in
rock. The drift was excavated in much the same manner as the one in 33d
Street, but the rock being softer the radialax machine was not used.

TUNNEL EXCAVATION.

During the early part of the work, the contractor devoted his entire
attention to the work of excavation. Nearly all the excavation east of
Fifth Avenue was done before any of the lining was placed. At a number
of points west of Fifth Avenue and at a few points to the east the
nature of the rock was such that the two operations had to be done
simultaneously.

_Single-Tunnel Method._--For an average distance of 350 ft. west from
the First Avenue Shafts there were four single tunnels. The rock was
sound and comparatively dry. A top heading of the full size of the
tunnel and about 8 ft. high was first driven. It was drilled by four
drills mounted on two columns, and was blasted in the ordinary way. The
bench was about 13 ft. high. Tripod drills, standing on the bench,
drilled the usual holes, but, owing to the lack of head-room, steels
long enough to reach the bottom of the bench could not be used. Tripod
drills were set as low as possible at the foot of the bench and drilled
lifting holes. These holes were inclined downward from 10 deg. to 15 deg. to the
horizontal, and were spaced to converge at the location of the drainage
ditches. The heading was usually driven from 10 to 20 ft. in advance of
the bench. At this distance a large part of the muck from the heading
was shot backward over the bench. In the single tunnels the muck was
loaded by hand.

_Twin-Tunnel Methods._--From the end of the single-track tunnel westward
to Fifth Avenue on 33d Street, and to Madison Avenue on 32d Street, with
some exceptions, each pair of tunnels was excavated for the entire width
at one operation. Three different methods of work were extensively used.
They were the double-heading method, the center-heading method, and the
full-sized-heading method, and these differed only in the manner of
drilling and blasting. The bench was usually within 10 or 15 ft. of the
face of the heading, and was drilled and fired in the same way as in the
single tunnels. After the installation of the permanent plant, most of