e
surface under the trolley tracks, and only 18 in., the depth of
stringers and planking, beyond. The stringers under the trolley tracks
were 8 by 16-in. yellow pine, spaced three to a track, and those for the
driveway were 6 by 14-in., spaced 1 ft. 6 in. on centers, the planking
being 4-in. yellow pine.

The first step in the construction was to excavate a trench 15 ft. wide
on the west side of the street, the east side of the trench being 4 ft.
west of the westernmost trolley rail. While this work was in progress,
all vehicular traffic was turned to that part of the avenue east of the
westerly trolley rail. The trench was sheeted and timbered, and carried
to a depth sufficient to receive the intermediate cap. That portion of
the bent from the bottom of the intermediate cap to the bottom of the
top cap was then erected for the width of the trench, after which the
60-in. cast-iron sewer and the 48-in. water main were laid in position
and caulked. The top cap, stringers, and planking were then laid, for
the full width of the trestle west of the trolley tracks. This work was
finished and the sewage turned into the new sewer in April, 1905.

As the planking was laid west of the trolley tracks, traffic was turned
to that side of the street, and the material east of the tracks was
excavated to its natural slope. Trenches were then dug under the tracks
on the line of the bents, and the caps were set in position on blocking.
The material between these trenches was then removed, the tracks being
supported meanwhile by blocking at least every 6 ft., and the stringers
and planking were shoved into place. Excavation was next made between
the caps to a depth of about 5 ft. below them, needle-beams being placed
under the caps, one or two at a time, and supported on posts erected in
these excavations; the material on line of the bents was excavated to
the depth of the intermediate caps, which were then set, together
with the posts and bracing for the upper deck of the structure. This
operation was repeated for the lower deck, about 10 ft. being gained for
each change of posts, and three shifts, therefore, were required.

At the beginning of the train-transportation period, May 22d, 1905, two
shifts of 10 hours each were inaugurated, and the earth was handled at
the rate of from 85,000 to 90,000 cu. yd. per month; but, by the end of
August, when a little more than 60% of the total earth had been disposed
of, the rock began to interf