_Conduits._--The arrangement of the conduit lines is shown in the general cross-section.[3] On the core-wall side there are 48 lines for telegraph and telephone cables, built of 4-way multiple conduit, each piece of which is 3 ft. long and about 10 in. square outside. On the other side there are the high- and low-tension lines, built of single conduit 18 in. long and a little more than 5 in. square outside. Manholes or splicing chambers are built every 400 ft., and are about 8 ft. long and 4 ft. wide. General views of the conduits as built are shown in Fig. 4, Plate XXV, which shows all the lines in one tunnel, and in Fig. 1, Plate XXV, which shows the telegraph and telephone lines, with the expanding mandrels used in laying them. [Footnote 3: Plate VIII in the paper by Mr. Jacobs.] [Illustration: Plate XXV. Fig. 1: K 173. P.R.R. Tunnels, N. R. Div. Sect. K. (Bergen Hill Tunnels.) Hackensack Portal and Approach. Telephone and Telegraph ducts and mandrels. Nov. 20, 08. Fig. 2: K 125. P.R.R. Tunnels, N. R. Div. Sect. K. (Bergen Hill Tunnels) Weehawken Shaft, North Tunnel. View showing general construction of tunnel lining forms, and clearance to allow disposal of excavated material. June 17, 07. Fig. 3: K 156. P.R.R. Tunnels, N. R. Div. Sect. K. (Bergen Hill Tunnels) Weehawken Shaft, South Tunnel. North side looking East, showing method of placing waterproofing. Oct. 22, 07. Fig. 4: K 147. P.R.R. Tunnels, N. R. Div. Sect. K. (Bergen Hill Tunnels) Weehawken. General view showing center and first section of arch and completed lining, North Tunnel. Sept. 24, 07.] In attempting to plan the work of placing the lining, two methods of building the bench-wall were considered. One was to build the wall in longitudinal sections, each section separated by a line of ducts; and the other was to attempt to build the wall in the manner called for by the specifications, which required the concrete to be carried up in layers as the conduits were laid. In this latter method, it was proposed to bond the concrete together with the forked bonds, the details of which are shown by Fig. 15, _A_, but, as it might have been impractical to use these if the wall had been built in sections, provision was made in the contract to place expanded metal, as shown by Fig. 15, _B_, if this was thought advisable. The method of construction necessary, if the wall had been built in sections, is shown graphically by the five sketches, Fig. 15, _B_, 1, 2, 3, 4, and 5.