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generated at all, or how to get rid of them when once
they are formed. Charcoal ventilators have been
pronounced by most observers to be successful only in
exceptional instances, and it is only with special
attention they can be used for the deodorization of the
sewers, or for disinfecting on any permanent or extensive
scale. Street ventilation or open grids have the
objection just pointed out, in giving out noxious smells,
and are too much at the mercy of changing winds
and currents of air, and have no regulated action.
Flushing therefore, when thoroughly understood,
supersedes all other operations. It will keep the
temperature of the air, and of the liquid matters of the
sewers at a low temperature, and so materially check
decomposition and putrefaction, in fact, it is extremely
doubtful whether a temperature 45° to 50° will permit
of any smell or decomposition sufficient for creating
gases to any extent appreciable outside. The temperature
of air in sewers at present is often as high as
70°, and becomes in proportion favorable for putrefaction
and diffusing vapours.
After all that can be said, and experiments tried,
I venture to predict that water is the only agent, that
in sufficient quantity, and at all times, can be used as
a deodorizer for sewage, while as a motive power
it is the cheapest means for carrying it away, and
especially of matters, that if permitted to lodge,
create the nuisances complained of. It is an affair of
engineering detail to show how cold water shall be
properly and so usefully employed.