-in.
water main was carried over the excavation on cables from the temporary
shoring girders, except when they were being jacked up, at which time posts
were placed beneath it.

Anchor-bolts were put in place between the column bases and the bents
directly beneath, in order to increase the lateral stiffness, and raker
braces were also used. This having been done, the temporary shoring girders
were moved south to the next column, where the process was repeated. The
timber bents, shown in detail by Fig. 2, were then put in place as shown by
Figs. 4 and 5, and by Fig. 3, Plate XLVII. These bents were framed as
tightly as possible, using generally a 20-ton jack, and they were erected
simultaneously at each pair of columns. The weight was taken on these
columns by jacking up directly beneath the column base and taking out the
blocking between this base and the bent directly beneath the column. On
releasing the jack the weight was transferred to the permanent timber
bents, and the east and west columns of each pair were transferred on the
same day. One 80-ton jack was used on the easterly columns and two were
necessary on the westerly columns, one on each side of the 24-in. water
main. The raker braces of these permanent bents were not framed as tightly
as the main posts, in order that the main post should carry the entire
weight and the raker braces merely steady the structure.

Timber bents were erected on girders "C" to carry the I-beams under the
surface railway structure, as shown on Fig. 3, and all temporary posts
under these I-beams were removed. The bents were framed with a jack, as
tightly as possible, and very little settlement of the track occurred.

A cradle was then built under the 24-in. water main and placed on girders
"C," and, as a temporary footwalk had been constructed on the west side of
the avenue, it will be seen that all structures were thus carried on
girders "C."

All structures were put on the girders "C" before continuing the excavation
on the sides of the avenue because, in case of a slide of rock, there would
be less danger than to individual structures. The outside piers, on
which the girders "C" rested, might even be lost, without affecting the
stability of the structure, and posting could readily be done beneath these
girders in case of necessity.

A very careful record of levels, taken on the elevated railway columns, was
kept, observations being made during each jacking up and at least tw