XX. J. G. S. PURVIS. 



the float and closed the valve. This has been found to work 

 admirably, and the rate of flow is now practically constant. 



With regard to the controlling gear for regulating the distribu- 

 tion of the elfluent from the cultivation tank into the coal and 

 coke filters, the whole thing depends on the filling of each tank 

 in succession. When one tank fills it* shuts off the supply to 

 itself, starts the next one in sequence to fill, and starts the next 

 one behind it to empty. This is brought about in the following 

 manner: — The sewage after rising up through the cultivation tank 

 passes over a weir and is collected in a distributing channel. The 

 external wall of this channel is provided with four cast iron traps, 

 one to each tank. Each contact tank is provided with an air bell 

 placed at such a level that just at that moment when the tank is 

 full, air is forced out of the bell, locks the trap and shuto off the 

 supply. Each contact tank is also provided with a trapped syphon 

 standing on the floor and discharging through the wall into a 

 channel common to all. 



A cistern built into the external wall of each tank, contains a. 

 float arm actuating two valves — one connected to the bell of that 

 particular outgoing syphon to which the cistern belongs, and the 

 other connected to the trapped inlet of the next tank in sequence. 

 Each cistern is connected to the next tank in sequence by a pipe 

 which conveys the overflow when the said tank is full. When a- 

 tank is filling, the one behind it is standing full and the one in 

 front of it is standing empty. When full, air is forced out of the 

 air bell, locks the trapped inlet and stops any further supply as 

 has already been stated. At the same time sewage overflows inta 

 the cistern of the tank behind it, raises the float arms, releases, 

 the air from the trapped outgoing syphon, causing its discharge, 

 and also releases the trapped inlet to the next tank in sequence- 

 causing it to start filling, and so on without ceasing. The out- 

 going syphons are regulated so that the rate of discharge can be 

 controlled to anything predetermined. 



In concluding this short review, seeing that the results from 

 the septic tank and the Scott-Moncrieff systems as laid down here 



