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extreme case, but such instances do actually exist. I believe that the flushers
are very diligently employed in removing accumulations in the sewers, and
keeping the passages as free as possible; and I am informed by your Chief
Surveyor that the sewers are more free from deposits at the present time
than they have been for years; but when a sewer is badly constructed, no
diligence on the part of the flushers can prevent the deposition of putrifying
matter in it. When a sewer is inefficient, it is no matter for surprise that the
gulley gratings and sewer ventilators should disgust the passers-by, and poison
the air with noxious gases. There is then an outcry that the gulleys be
trapped ; if this demand is acceded to, and the trapping is effectual, foul gases
are concentrated in the sewer, and the sewers-men ran the risk of being suffocated
either with or without explosions. These accidents are by no means of
very rare occurrence. If the foulness of the sewer does not reach such a degree
as that above indicated, yet still, from the increased pressure of air in them,
caused by the traps, there is a greater tendency for the gases to force themselves
into dwellings in the various methods I have above alluded to.
A very able Report on the Ventilation of Sewers has been written by Mr.
Haywood, the Surveyor to the Commissioners of Sewers, and another on Sewer
Gases and the Ventilation of Sewers, by Dr. Letheby, the Medical Officer of
Health for the City. There appear to be very great practical difficulties in
efficiently ventilating sewers, and the methods alluded to by Mr. Haywood are
attended with a very great expense. Dr. Letheby proposes a method not
exactly of ventilating the sewers, but of deodorizing the gases which escape
from them. For this purpose he has suggested the use of vegetable charcoal,
which has for some time been known to have a very remarkable power in
absorbing gases, and rendering those which arise from decomposition completely
innocent by promoting rapid oxidation after the manner of combustion in a fire.
Dr. Letheby says, " It is manifest that we have in common wood charcoal a
powerful means of destroying the foul gases of sewers. How it is to be applied
is fortunately a matter of but little embarrassment, for let the sewers be
ventilated as they may, either by open gratings in the street, or by the rainwater
pipes of the houses, or by the pillars of the gas lamps, or by tubes carried
up at the landlord's expense from the drains of every house, or by especial
shafts in the public streets; in fact, let the gases go out of the sewers how they
will, and where they will, you have but to place a small box containing a few
pennyworths of charcoal in the course of the draft, and the purification of the
air will be complete." The experiment is about to be tried in one large
district in the City, and it will be better to await the results of this experiment
before much is said as to the general adoption of such a scheme as this. The
suggestion is no doubt ingenious, and will probably lead to useful results ; the
points to be feared are that the charcoal will soon lose its power through
damp and saturation with the sewer products, and that the friction of gases on
the charcoal filters, though not offering great obstruction to the exit of air, will
be quite sufficient to divert the currents into other channels. It is quite certain
that to be of much use, the filters must be applied to all the openings out of the
sewers within the district to which they are applied. The principle may be
used in a variety of ways; an ingenious apparatus has been contrived by Mr.
Burge, the Medical Officer of Health for Hammersmith, for deodorizing the
gases escaping by the galley gratings and sewer ventilators, and this may be
advantageously applied to sewers at isolated points, where, from any cause the
gases are very foul, and the persons exposed to them are very numerous, and yet
a complete trapping of the sewer is undesirable. For instance, in a crowded
court, with a sewer not very efficient, and terminating in a blind extremity (at
which point the sewer gases are usually concentrated), such an apparatus would
be very useful. Mr. Burge finds that charcoal is not the best ingredient for
these filters, and is at present engaged on experiments as to what disinfectant is