Fig. 1. K 26. P.R.R. Tunnels, N. R. D. Sect. K. (Bergen Hill Tunnels,) Weehawken Shaft. Scaffold car in South Tunnel at Sta. 267+60. Jan. 11, 06.
Fig. 2. K 31. P.R.R. Tunnels, N. R. Div. Sect. K. (Bergen Hill Tunnels) Weehawken Shaft. Headhouse at ? elevator frame work, looking West. Oct. 17, 06.
Fig. 3.—Round Holes in Concrete Forms.
Fig. 4.—Round Holes in Concrete Forms Completed.
Drilling.—Where no timbering was required, several different methods were used in drilling and excavating the solid rock, though in all cases a center top heading was driven. The four diagrams, Figs. 1, 2, 3, and 4, give typical examples of these methods and show, in the order of their numbers, the general tendency of the development from a small heading kept some distance ahead of the bench, to a large heading with the bench kept close to it. The notes on each diagram give the general details of the quantity of drilling and powder used, methods of blasting, etc., and on the progress profile, [Fig. 6], is indicated those portions of the tunnels in which each method was used.