also the disposal of the materials.  In the earlier part of the work, they were used as fill in the freight terminal of the Pennsylvania Railroad at Greenville on the west side of the Upper Bay; when the fill at this place was completed, the materials were sent to the tunnel company’s yard on the Passaic, at Harrison, N. J., and a small part to the embankment in the Meadows Division.  On account of the occasional closing of the Passaic by ice, this involved the possibility of, and to some extent resulted in, interruptions to the work of excavation.  The contract for the cross-town tunnels carried an option in favor of the company to require the contractor for those tunnels to dispose of materials at a stated price, and in the latter part of 1907, when the excavation in these tunnels was being pushed rapidly, the railroad company, unwilling to incur the responsibility for delays during the winter, availed itself of this option.  The disposal of materials was an important part of the work, and will be dealt with more fully by the Resident Engineers.

[Illustration:  PLATE XIV.—­Map and Profile, Cross-Town Tunnels]

At the time the contract was made with S. Pearson and Son, Incorporated, it had not been determined whether mechanical ventilation would be provided for the tunnels, and therefore the contract with that firm did not include the final concrete lining at the shafts, above the inverts of the tunnels.  After the adoption of plans for mechanical ventilation, in the latter part of 1908, the plans for lining the shafts with concrete, including flues for conducting air to the tunnels, and stairways for ingress and egress, were completed, and the work was placed under contract; it will be described in detail by F. M. Green, Assoc.  M. Am.  Soc.  C. E.

At the east end of the work under the Pearson contract, the rising grade of the tunnels brought them so near the surface of the ground that their extension eastward could be carried out more readily in open cut than by tunneling.  The locations of the portals could be varied somewhat, and they were built on rock which was found in rather narrow ridges at convenient places.  Tunnels B and D have a common portal; Tunnels A and C have separate ones, the portal for Tunnel C being located about 800 ft, west of the others as a result of its crossing over Tunnel B, as already explained.  Eastward from the portals, the track system expands, in order to provide connections with the tracks of the Long Island Railroad to and from Long Island City, with the New York Connecting Railroad and New England lines, and with the storage and cleaning yard known as the Sunnyside Yard extending to the west side of Woodside Avenue, 2-3/4 miles east of the East River. (Plate XV.) The yard and approaches are designed to avoid grade crossings by opposing trains.  The various general features of the yard and tunnel approaches, bridge crossings, and street closings, have been described in sufficient detail by General Raymond in the introductory paper.