SOME REMARKS ON SEWERAGE SYSTEMS. 107 



converging to various stations, which are placed at the 

 lowest convenient points with reference to the general level 

 of the ground. At each station the sewage is received into 

 a Shone ejector, worked by compressed air, which pumps it 

 along cast-iron mains under pressure to the outfall. These 

 ejectors are, therefore, the distinctive features of the " system," 

 so-called. The sewage is delivered through a cast-iron main 

 into the cylindrical vessel. In the delivery-pipe is a box con- 

 taining a lignimi vitce spherical ball, which falls below its 

 seat when the ejector is filling and rises tight against it when 

 discharging. To the bottom of the ejector the discharge- 

 pipe is fixed, and contains a similar ball, which falls down 

 tight on its seat when the ejector is filling and rises when 

 it is discharging. At some central station the air-com- 

 pressing engines are placed, and a cast-iron air-main is led 

 to each ejector. The compressed air here enters a cylinder 

 in which works a slide valve, which, as it moves to and fro, 

 enables the compressed air to enter the cylindrical vessel 

 into which the sewage is flowing. Inside the cylindrical 

 vessel are a cup and bell upon an iron spindle, which is 

 continued through a stuffing-box in the top of the ejector 

 and connected to the slide valve. The action is as follows : 

 As the sewage flows into the ejector it compresses the air 

 in the bell, causing at last sufficient pressure to lift the 

 spindle. This moves the slide-valve, and immediately ad- 

 mits the compressed air into the ejector, which, closing the 

 inlet ball against its seat and driving the outlet ball above 

 its seat, forces the sewage up the discharge-pipe. "When 

 the sewage has fallen low enough in the ejector, the weight 

 of the cup and ball and the sewage remaining in the cup, 

 pulls down the spindle, closes the air inlet port, and the 

 ejector begins to fill again. This process goes on con- 

 tinually, and perfectly automatically, so long as there is 



