The specifications called for a final rodding after completion. A group of the apparatus used in this process is shown in [ Fig. 1, Plate XXXV]; the various parts are identified by the following key:

[Key to Fig. 1, Plate XXXV].

1.—4-way duct, for telephone and telegraph cables,
2.—2-way duct, for telephone and telegraph cables,
3.—1-way duct, for high- and low-tension cables,
4.—Plug for closing open ends of ducts,
5.—Plug for closing open ends of ducts in position,
6, 7, and 8.—Cutters for removing obstructions,
9.—Hedgehog cutter for removing grout in ducts,
10.—Rodding mandrel for multiple ducts,
11.—Laying mandrel,
12.—Rodding mandrel, with jar-link attached,
13.—Laying mandrel,
14 and 15.—Rubber-disk cleaners, used after final rodding,
16 and 17.—Sectional wooden rods used for rodding,
18.—Section of iron rods used for rodding,
19.—Jar-link,
20.—Cotton duck for wrapping joints of multiple ducts,
21.—Hook for pulling forward laying mandrel,
22.—Top view of trap for recovering lost or broken rods left in ducts.

Ordinary ¾-in. gas pipe was used for the rod, and a cutter with rectangular cross-section and rounded corners was run through ahead of the mandrel: following the cutter came a scraper consisting of several square leather washers, of the size of the ducts, spaced at intervals on a short rod. The mandrel itself was next put through, three or four men being used on the rods. All the ducts in a bank were thus rodded from manhole to manhole. When a duct was rodded it was plugged at each end with a wooden plug. A solid wooden paraffined plug was used at first, but afterward an expansion plug was used.

Very little trouble was met in rodding the power conduits, except for a few misplaced ducts, or a small mound of mortar or a laying mandrel left in. At such points a cut was made in the concrete and the duct replaced.

In the subgrade telephone and telegraph ducts east of the Manhattan Shaft, much trouble was caused by grout in the ducts. The mandrel and cutters were deflected and broke through the web of the ducts rather than remove this hard grout. Trenches had to be cut from the floor to the top of the water-proofing, the latter was then cut and folded back, and the ducts replaced. To do this, a number of ducts had to be taken out to replace the broken ones and get the proper laps. The water-proofing was then patched and the concrete replaced. This grout had not penetrated the water-proofing, but had got in through the ends of the ducts where they had not been properly plugged and protected. The duct gang, both for laying and rodding, generally consisted of

1 Foreman, at $3.50 per day,
and 9 laborers, at $1.75 per day.

When laying: 4 men were laying, 2 men mixing and carrying mortar, and 3 were transporting material. When rodding: 4 men were rodding, 2 men at adjacent manholes were connecting and disconnecting cutters and mandrels, 1 was joining up rods, and 2 men assisting generally.

The cost of this work is shown in [Table 17].