106 SOME REMARKS ON SEWERAGE SYSTEMS. 



Firstly. It is inconvenient and unhealthy to be obliged to 

 retain sewage in the house or receptacle until stated times, 

 instead of removing it directly. 



Secondly. There is great liability to break down. (It is 

 imperative to keep the whole apparatus as air-tight as 

 possible.) 



Thirdly. As it is impossible to guarantee an absolutely 

 air-tight apparatus, it is necessarily a costly system with 

 regard to the work done. 



Fourthly. It requires special fittings in the houses. 



Fifthly. It deals only with a portion, and with the more 

 solid portion, of the sewage, such as that from water-closets, 

 leaving a large quantity of liquid sewage to be still dealt 

 with by ordinary means. 



The other method of utilizing air has only been in exist- 

 ence about twelve years, and is the invention of Isaac 

 Shone. Mr. Shone calls it a new system — the hydro-pneu- 

 matic ; but it is properly simply a modification of a gravita- 

 tion system, in which patent automatic ejectors, worked by 

 compressed air, are introduced for lifting the sewage at 

 various points, and thus avoiding the necessity of flat 

 sewers of deposit, where the lie of the ground does not 

 admit of proper falls by gravitation. In this there is no 

 doubt that Shone's apparatus is a distinct advance in the 

 healthy drainage of towns. Engineers have often been 

 hampered, and costly drainage systems spoilt, by the im- 

 possibility, without enormous expense, of obtaining by 

 simple gravitation, either to an outfall or to a pumping 

 station, a sufficient velocity to render the sewers much 

 better than elongated cesspools, always giving off foul 

 odours, and always needing attention. 



The Shone system may be shortly stated as follows : — 



The usual stoneware pipe sewers are laid gravitating and 



