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37
foul gases from such sewer into the house drain. The fouler
the sewer, the more important becomes the necessity for this
interception.
Having regard to the present state of many Metropolitan
sewers (e.g., elongated underground cesspools, with foul
deposits and silt, varying in amount at times from a few inches
in depth to almost the whole of the lumen of the sewer being
blocked), it is clear that the ventilation of house drains must
be kept definite and distinct from that of the sewers, and
that any attempt to ventilate sewers by, and through, house
drains must result disastrously, and be a danger to health.
There are two important questions involved in the Report
of the Borough Engineer of Lewisham which have not by
him been kept separate and distinct, as they must at all times
be, viz.: (i) the need for efficient ventilation of sewers, and
(2) the need for efficient ventilation of drains—the former
resting with the Sanitary Authority, and the latter with the
private owner.
(1) Ventilaition of Sewers.
Practically all sanitarians are agreed that sewers require
freely ventilating, though opinions vary as to how this ventilation
may best be practically carried out, whether by
means of open gratings, at the level of roads (and, if so,
how many), or by means of outlet ventilating shafts (and, if
so, of what size and calibre). Personally, I have always
held the view (which I see no reason to alter to-day) that
the alleged danger to health from open ventilating grids at
the level, and in the middle, of the roads has not yet been
satisfactorily proved, provided such roadways are sufficiently
wide, and that, as far as Lambeth Borough is concerned,
I have no reason for believing that any such danger to
health therefrom exists (statistics pointing rather to the contrary
conclusion). I have always advised the closure of
open ventilating grids situated in narrow streets and courts,
but that advice must not be taken to carry with it a wholesale
condemnation of all open grids as sewer ventilators at the
level of roads; indeed, for efficiency, they appear to be
better than shafts, which, by virtue of their construction,
are lessened in practical utility by reason of friction, due to
bends in the pipes, etc. It is more a question of