183+50, showing excavation under Ninth Avenue, permanent concrete piers
under Elevated Railway Columns and removal of temporary shoring girders
"C". April 8, 09.]

[Illustration: PLATE XLIX, FIG. 4.--TW 95, P.T. & T.R.R. Co. N.R. Div.
Terminal Station West. View under Ninth Avenue looking Southward from 100
feet South of center line, showing underpinning of Ninth Avenue structure
taken at sub-grade. May 25, 09.]

It was made a practice all through the work to transfer the weight of the
structures very positively from one support to another by lifting them
bodily by jacks, and putting in filler pieces before releasing the jacks,
not trusting to wedging to transfer the loads. In fact, apart from the
boxing-in of the surface railway concrete, no wedges whatever were used.
This appears to have been a decided advantage, for, with the constant
pounding of trains on the elevated railway and the jarring due to heavy
trucks on the pavement blocks, it is very likely that wedging would have
become loosened and displaced, whereas, with blocking, there was little or
no tendency toward displacement due to vibration. Although the vibration of
the structure, when a long length was supported on girders "C" resting on
the permanent viaduct girders on the sides of the avenue, appeared to be
considerable, not only vertically but transversely, very careful
observation showed that the sag in the girder "C" due a live load of three
elevated railway trains, one surface railway car, and one heavy truck,
amounted to 1/8 in. The sideway vibration did not amount to more than 1/32
in. on either side of the normal position. More vibration was caused by
heavy trucks and wagons going over the stone pavement than by the elevated
railway trains or surface cars.

No blasting was done near the supports of the elevated railway structure