From these figures it will be seen that, at their centres, the main girders of the bridge are bolted down to a casting of the form shown in the upper part of Fig. 10, the metal of this casting, which consists of a ring of section, 18 in. deep, connected to a central boss by radial arms, being 2 in. thick throughout. On the top of the pier is fixed another casting of similar form to that just mentioned, this casting, the metal of which is also 2 in. thick, being shown in plan in the lower half of Fig. 10, and in section in Fig. 2. These two castings from the upper and lower paths for the conical rollers by which the bridge is carried, these rollers, which are 11½ in. wide, and have a mean diameter of 1 ft. 3 in., being seventeen in number, and being connected by a frame, as shown in Fig. 2. In the central boss of the lower casting is fixed a pin 7 in. in diameter, this pin projecting upwards into the boss of the upper casting, and thus serving to keep the various parts in place. It does not, however, carry any of the weight of the bridge.

The arrangement of the gearing for turning the bridge is shown in Fig. 5. It consists, as will be seen, of an annular rack bolted to the top of a cast-iron cylinder forming the supporting pier ; this rack being geared into by a pinion fixed at the lower end of a vertical shaft carried by bearings contained in a short cast-iron pillar placed outside one of the girders, as shown.