Figure 34.—Beach's Broadway Subway. Advancing the shield by hydraulic rams, 1869. MHT model—1½" scale. (Smithsonian photo 49260-E.)
Unlike the driving of the Tower Subway, no excavation was done in front of the shield. Rather, the shield was forced by the rams into the soil for the length of their stroke, the material which entered being supported by the shelves. This was removed from the shelves and hauled off. The ram plungers then were withdrawn and a 16-inch length of the permanent lining built up within the shelter of the shield’s tail ring. Against this, the rams bore for the next advance. Masonry lining was used in the straight section; cast-iron in the curved. The juncture is shown in the model.
Figure 36.—Interior of Beach Subway showing iron lining on curved section and the pneumatically powered passenger car. View from waiting room. (Scientific American, March 5, 1870.)
