PROCEEDINGS OF THE SECTIONS, 339 
The Ventilation of Sewers and the Dwelling. 
By J. Trevor Jones, City Engineer, 
[Read before the Sanitary Section of the Royal Society of N.S.W., 
10 August, 1886.] 
as a vehicle for any morbific germs that may be mixed with the 
sewage from the dejecta of fever patients, it becomes the duty of 
the Engineer, as the constructor of sewers, to devise means where- 
by such. exhalations may be discharged in situations where they 
will not enter into the composition of the breathing air of the 
city or dwelling. 
The emanations referred to are a compound body, known under 
the generic name of “sewer gas”; its component parts being, as 
stated in Mr. Baldwin Latham’s elaborate work on the subject, 
varying proportions of carbonic dioxide, uitrogen, carburetted 
hydrogen, sulphuretied hydrogen, ammoniacal compounds, vapour 
suffer from the attacks of such germs of fever, cholera, small-pox, 
typhoid, &c., as may be projected into the sewage, of which the 
gases arising from the sewage form a convenient vehicle for the 
dissemination thereof. ; ‘cee 
The buoyancy, or tendency to float upwards in atmospheric air, 
of this compound gas varies in the proportion that it is compo 
of the lighter or heavier of the above constituents, and in pro- 
portion to its excess of heat over the surrounding air, but 
ordinarily it is found a little lighter than air. 3 
rom this tendency to rise, it flows from the lower towar 
upeast shaft for it to escape into such space as it will do least 
harm, or where it cannot mix with the air of the streets or 
i 
dwellin, 
