lagging. This served to keep the pipes in position and to locate them
after the lagging was taken down.

The cost of labor in the tunnels directly chargeable to concrete was
$1.80 per cu. yd. The top charges, exclusive of the cost of materials
(cement, sand, and stone), amounted to $3.92.


ELECTRIC CONDUITS.

In one bench wall of each tunnel there were fifteen openings for power
cables and in the other, between the river shafts, there were forty
openings for telephone, telegraph, and signal cables. East of the Long
Island shaft, the number of the latter was reduced to twenty-four. The
telephone ducts were all of the four-way type. The specifications
required that the power ducts should have an opening of not less than
3-1/2 in., nor more than 3-7/8 in., and that after laying they should
pass a 4-ft. mandrel, 3-3/8 in. at the leading end and 2-5/8 in. at the
other. The outside dimension was limited between 5 and 5-3/8 in. The
openings of the four-way ducts were required to be not less than 3-3/8
in., nor more than 3-5/8 in., and after laying to pass a 5-ft. mandrel,
3-1/4 in. at the leading end and 2-1/2 in. at the other. The outside
dimensions were limited between 9 and 9-1/2 in. All were to be laid in
1/4-in. beds of mortar. The specifications were not definite as to the
shape of the opening, but those used were square with corners rounded to
a radius of 3/8 in. The four-ways were 3 ft. long, and the singles, 18
in.

A study of the foregoing dimensions will show that the working limits
were narrow. Such narrow limits would not pay for the ordinary conduit