viaduct completed. New foundations were then placed on the deck of the
viaduct to carry all structures.

Fifty-four of these girders were required, each weighing about 19,000 lb.
The bents carrying the ends of these girders on the sides of the viaduct
are shown on Fig. 2. They were of long-leaf yellow pine. These girders were
located so that a cradle could be laid on them east of the elevated railway
structure to carry a proposed 48-in. cast-iron water main.

_Girders "B."_--Eighteen of these girders were required, each weighing
about 6,000 lb. The timber bents supporting these girders, shown on Fig. 2,
were of long-leaf yellow pine.

The total weight, including the elevated railway structure, surface railway
structure, pipes, etc., supported during the work, amounted to about 5,000
tons.

_Details of the Work._--The method in general is shown on Figs. 4 and 5. At
first the east side of the avenue was closed and excavated down to rock,
the earth was mined out under alternate yokes of the surface railway
structure, and temporary posts were placed under the yokes to support the
structure while the remainder of the earth was being removed. Then
needle-beams and posts were placed under each yoke. The concrete forming
the track structure was then enclosed with planking to prevent it from
cracking and falling. I-beams were then placed under the needle-beams
carrying the structures, and these were carried on posts; they were changed
alternately until the excavation had been taken out to a depth of about 16
ft. below the surface. In placing these I-beams, heavier blocking was used
in the center of the span than at the ends where the bents would come, to
prevent the subsidence of the track owing to the sag in the I-beams. As