THE CONQUEST OF NATURE 



swings while remaining in contact with the piston. 

 Steam is admitted to the chamber on one side of the 

 flap, and so causes an unbalanced pressure upon the 

 radial arm." 



This arrangement has been re-invented several times. 

 Essentially the same principle is utilized by Joshua 

 Routledge, whose name is well known in connection 

 with the engineer's slide-rule. A model of this engine 

 is preserved in the South Kensington Museum, and the 

 apparatus is described in the catalogue of the Museum 

 as follows: 



"The piston revolves on a shaft passing through the 

 centre of the cylinder casing. The flap or valve hinged 

 to the casing, with its free end resting upon the piston, 

 acts like the bottom of an ordinary engine cylinder. 

 The steam inlet port is on one side of the hinge, and 

 the exhaust port on the other. The admission of steam 

 is controlled by a side valve, actuated by an eccentric 

 on the fly-wheel shaft, so that the engine could work ex- 

 pansively, and the steam pressure resisting the lifting 

 of the flap would also be greatly reduced, so diminishing 

 the knock at this point, which, however, would always 

 be a serious cause of trouble. The exhaust steam 

 passes down to a jet condenser, provided with a supply 

 of water from a containing tank, from which the in- 

 jection is admitted through a regulating valve. The air 

 pump, which draws the air and water from the condenser 

 and discharges them through a pipe passing out at the 

 end of the tank, is a rotary machine constructed like the 

 engine and driven by spur gearing from the fly-wheel 

 shaft. Some efforts have been made to prevent leakage 



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