The gangs placing the arches were paid over-time when they were required to work after 6 o’clock to finish their section, which was generally only necessary when the quantity of rock packing to be placed was very large. If they finished their section before 6 o’clock, however, they were allowed to quit when this was done, and were given a full day’s pay. The difference in time, when there was any, was usually due to the greater or less quantity of rock packing, as the excavation varied from the standard section line. In building the arches, the night gang set the two ribs (one at the center and one at the forward end of the section to be built), placed the lagging on the sides, 4 or 5 ft. high, built the shoveling platform on the horizontal cross-braces of the ribs, and placed the traveling gantry in position for use. The forward end of the gantry (that is, the end farthest from the arch being built), as shown in Fig. 1, Plate XXVI, was loaded with rock packing to be used as required. As the concrete was brought into the tunnel it was hoisted and dumped on the end of the gantry next the arch, and shoveled from there to the platform on the ribs and from there into place. The rock packing brought in during the day was dumped on the front or back end of the gantry, as was most convenient, and handled into the work in the intervals between batches of concrete. The concrete and rock packing, with the back-lagging and water-proofing, where these were used, were placed simultaneously, or nearly so, and brought up the sides together until the key was reached; the latter was then worked from the back toward the front. The key was usually made about 5 ft. wide, the lagging for this width was made 5 ft. long and put up in two sections. It was found to be more convenient to have the key of this width than narrower. The method used in making the closures where two sections of the arch came together is shown by Fig. 17. [Illustration: Fig. 17. [Full Page] SKETCH SHOWING METHOD OF MAKING ARCH CLOSURE CROSS-SECTION OF TUNNEL SHOWING JACK PARTLY EXTENDED LONGITUDINAL SECTION OF TUNNEL SHOWING JACK PARTLY EXTENDED PLAN OF BOX; END VIEW PLAN OF PLUNGER, BOTTOM OF BOX; END VIEW OF PLUNGER, JACK FULLY EXTENDED]