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 shaft, in position to be shoved out of the opening in the west side of the caisson. Temporary rings of iron lining were erected across the shaft in order to furnish something for the shield jacks to shove against.
The roof of the working chamber was then re-erected about 35 ft. above its original position and about 8 ft. above the tunnel openings. This time, instead of the two small shafts which were in use during the sinking of the caisson, a large steel shaft with a T-head lock was built. This is illustrated in [Fig. 2, Plate LXIV]. The shaft was 8 ft. in diameter. Inside there was a ladder and an elevator cage for lowering and hoisting men and the standard 1-yd. tunnel cars. At the top, forming the head of the T, there were two standard tunnel locks.