in. mortar
plaster coat, after which the concrete of the 4-ft. inverted arch was
placed. While the water-proofing and concreting were being done, the air
pressure was kept at from 30 to 33 lb. per sq. in., the full hydrostatic
head at the cutting edge. After standing for ten days, the air pressure
was taken off, and the removal of the roof of the working chamber was
begun. The water-proofing was done by the Union Construction and
Waterproofing Company.

TABLE 1.--RELATION OF THE FINAL POSITION OF THE CAISSONS TO THAT
DESIGNED.

================================================================
LOCATION.| LONG ISLAND CITY. |
----------------------------------------------------------------
Shaft. | North. | South. |
----------------------------------------------------------------
Corner. | High. | East. | North. | High. | East. | North. |
----------------------------------------------------------------
Northeast|0.21 ft.|0.08 ft.|0.05 ft.|0.32 ft.|0.15 ft.|0.28 ft.|
Northwest|0.22 " |0.08 " |0.02 " |0.00 " |0.15 " |0.12 " |
Southwest|0.27 " |0.14 " |0.02 " |0.18 " |0.45 " |0.12 " |
Southeast|0.23 " |0.14 " |0.05 " |0.39 " |0.45 " |0.28 " |
================================================================

=============================================================================
LOCATION.| MANHATTAN. |
-----------------------------------------------------------------------------
Shaft. | North. | South. |
-----------------------------------------------------------------------------
Corner. | High. | East. | South. | High. | East or West.|North or South.|
-----------------------------------------------------------------------------
Northeast|0.23 ft.|0.74 ft.|0.38 ft.|0.00 ft.|0.06 ft. east.|0.04 ft. south.|
Northwest|0.00 " |0.74 " |0.22 " |0.08 " |0.06 " " |0.13 " north.|
Southwest|0.11 " |0.31 " |0.22 " |0.21 " |0.45 " west.|0.13 " " |
Southeast|0.46 " |0.31 " |0.38 " |0.04 " |0.45 " " |0.04 " south.|
=============================================================================

The cost of labor in compressed air chargeable to concreting was $3.40
per cu. yd.

After the roof of each working chamber had been removed, the shield was
erected on a timber cradle in the bottom of the sh