VENTILATION OF SEWERS AND DRAINS. 169 
bearing on air currents in sewers can be extended and broadened. 
This matter alone would occupy the attention of one person, but 
as the practical work of a department has to be carried on, inves- 
tigations on these lines can only be carried out in connection with 
others as time permits. The question is too important to be 
allowed to remain uninvestigated. With regard to the possible 
danger of the air becoming charged with germs from the sewer 
ventilating shafts and being entangled with vapour during fogs 
as mentioned in connection with London and other British cities, 
I think the danger re fogs is so remote, considering the different 
climatic conditions of this city as compared with the ones referred 
to—the other question is however one for consideration. If the 
shafts were attached to sewers badly constructed, and were what 
is termed “sewers of deposit,” no doubt the gases from such ducts 
would be inimical to public health, but if on the other hand the 
sewers, notwithstanding constructive defects in some cases, are 
flushed and the deposit of solid filth prevented in addition to being 
air-swept by pure air being passed into the sewer, it will I think 
be admitted that the danger to public health is reduced to a mini- 
mum. Stagnation of the sewage and air in sewers leads to serious 
results, and the object of a sanitary authority should be to substi- 
tute motion for stagnation to both. The drying of the sewer 
walls by the currents of air passed into the sewers being likely to 
be a source of danger, is a question which can only be settled in 
any way satisfactorily by bacteriological investigation. So much 
has this matter impressed me that the Board on, my suggestion, 
intend having the matter scientifically investigated. There can 
be no doubt as to the purifying effect of the quantity of oxygen 
which is passed into the different systems annually, and as the 
exhaust shafts are carried well up above the living zone, the 
danger of vitiating the atmosphere appears to me to be remote. 
There is not the slightest doubt that to cremate the gases passing 
from a sewer would place the question of danger beyond all doubt 
—this matter is under trial and results will shortly be known. 
The temperature maintained in the shaft is, according to scientific 
