When the face of the bench had been brought to within 3 or 4 ft. of the forward end of the wall plate, the process of widening out and timbering another 20 ft. length of heading was begun. In some places the rock, though needing permanent support, was such that the work of taking out the bench and widening the heading was carried on simultaneously without increasing the danger; but the greater portion of the work, when strutting was required, was done as has been described. [Illustration: FIG. 66.--Diagram Showing the Arrangement of Drill Holes in the Heading and Bench of the Gallitsin Tunnel.] =Hauling.=--The excavated material was loaded at the foot of the bench in dump cars which were run by mule power to the portal or the shaft according to location, on 36 in. gauge-service tracks. Inclines at 159th Street were graded from the portal at 158th Street to the street surface. The cars were formed at this portal into a train and were taken up the incline to the dump at 162nd Street and the North River by construction locomotives. At the 168th Street and 181st Street shafts, the cars were hoisted to the surface in cages (elevators). In the former case, they were taken to the dump at 165th Street and the North River by mules and gravity; in the latter case, to various dumps by teams. At both shafts, stone crushers were located, therefore a great part of the material did not have to be hauled to the dumps or even taken to the surface as a great deal of stone was used in dry packing over the concrete arch. The material from the portal at Fort George was hauled by mules directly to the dump near by. =Lining.=--The entire tunnel was lined with concrete, consisting of a floor 4 ins. thick and vertical side walls 18 ins. thick and 25 ft. apart, which carried a semicircular arch 18 ins. thick except in the timbered portions where the thickness was increased to 21 ins. and to 24 and 27 ins. in some places. The springing line of the arch is 6 ft. 2 ins. above the concrete floor (5 ft. 6 ins. above the base of rail), hence the maximum clearance above the base of rail is 18 ft. The side walls and arch were built solid of rock to a height of 8 ft. above springing line and the space above that point between the concrete and the rock was packed by hand with small stones. The concrete of the arch was laid on timber centers erected for that purpose.