i : | 
VENTILATION OF SEWERS AND DRAINS. 143 
is sewered strictly upon, or very nearly upon, the separate 
system. But the immense advantages of the separate systen soon 
impressed themselves—as they must impress themselves upon 
every engineer who practically adopts it on however small a scale 
or for whatsoever special reason: Shone’s ‘system ” was then 
advocated for the sewerage, not of small areas, but of town areas 
in general ; and it was differentiated from Waring’s claims and 
works by the suggestion that Waring’s small conduits required 
a much greater fall to keep them clear than could generally be got 
uniformly over any area in the usual way, and that artificial falls — 
must therefore be got by leading the sewage to district-centres, 
whence it must be pumped (or ejected) to the main outfall sewer 
_ —which latter as being larger and carrying a greater volume might 
_ have an ordinary fall. This, no doubt, entitles ejector-sewerage 
to a distinctive title; but itis to be observed that the alleged 
necessity on which it is based has never been felt in the fifty or 
sixty cities of America which are now sewered on the separate — 
system. 
VENTILATION OF SEWERS AND DRAINS. 
By Joun M. SAIL, M. Inst. C.E. 
[With Plate IV.] 
[Read before the Royal Society, N.S. Wales, July 6, 1892. | 
THE ventilation of sewers and drains has in modern times been 
admitted to be a most important one in connection with preserva- 
tion of public health. It has exercised the minds, and has been 
a fruitful field of speculation among scientists and others for 
nearly forty years. 
