total weight being 9,102 lb.
per lin. ft. of tunnel. Fig. 1 shows the details of the standard heavy
lining.

In addition to the standard cast-iron lining, cast-steel rings of the
same dimensions were provided for use in a short stretch of the tunnel,
when passing from a rock to a soft ground foundation, where it was
anticipated that unequal settlement and consequent distortion and
increase in stress might occur, but, aside from the small regular drop
of the lining as it passed out of the tail of the shield, no such
settlement was observed.

Two classes of lighter iron, one with 1-in. web and 8-in. flanges and
the other with 1-1/4-in. web and 9-in. flanges--the former weighing
5,166 lb. per lin. ft. of tunnel and the latter, 6,776 lb.--were
provided for use in the land sections between East Avenue and the Long
Island City shafts. Two weights of extra heavy segments for use at the
bottom of the rings were also furnished. The so-called _XX_ plates had
webs and flanges 1/4 in. thicker than the standard segment and the _YY_
plates were similarly 1/2 in. heavier. The conditions under which they
were used will be referred to later. All the castings were of the same
general type as shown by Fig. 1.

Rings tapering 3/4 in. and 1-1/2 in. in width were used for changes in
alignment and grade, the former being used approximately at every fourth
ring on the 1 deg. 30' curves. The 1-1/2-in. tapers were largely used for
changes in grade where it was desired to free the iron from binding on
the tail of the shield. Still wider tapers would have been advantageous
for quick results in this respect.

No lug was cast on the segments for attachment to the erector, but in
its place the gadget shown on Fig. 4, Plate LXX, was inserted in one of
the pairs of bolt holes near the center of the plate, and was held in
position by the running nut at one end.

In the beginning it was expected that the natural shape of the rings
would not show more than 1 in. of shortening of the vertical diameter;
this was slightly exceeded, however, the average distortion throughout
the tunnels being 1-7/16 in. The erectors were attached to the shield
and in such a position that they were in the plane of the center of the
ring to be erected when the shove was made without lead and just far
enough to permit placing the segments. If the shield were shoved too
far, a rare occurrence, the erection was inconvenienced. In driving with
high vertical leads, which occu