286 MODERN GASWORKS PRACTICE
thé motions being obtained by means of a hydraulic ram (N) situated at the foot of the machine. The suspending chains (0) are carried over guide pulleys (P) to the points of support at the front and back of the beam. The beam is guided in the machine frame so that no side movement can take place. All the operations are practically automatic ; and a suitable platform (Q) is provided for the attendant, with all operating levers for valves and cocks placed in a convenient position within his reach. The hydraulic pressure may vary from 400 1b. to 600 1b. per square inch., and the water is conveyed by a flexible armoured hose pipe sufficiently long to ■carry the machine over a number of beds of retorts. When the outreacli of the pipe is attained, the hose Connection, as with. the Arrol-Foulis chargers, is shifted to'the next swivel joint on the main supply pipe and the machine carried on. Swivel joints are placed on the pressure main and are spaced to suit the length of the flexible liose pipe and adjusted to suit the particular arrangement used in the retort house.
The Williams-MacPhee Pusher
The Williams-MacPhee hydraulic pusher is one of the more recent of these
Fig. 203.— The Williams-MacPhee Pusher.