wing soap
bubbles can show you, will force a way through a basin full, and the
same thing would happen if there should chance to be a backward current
of air through these pipes, with this difference, that while the soap
bubbles are harmless beauties, these may be filled with the germs of
direful diseases. Still another danger to which this light water-seal
is exposed is that a downward rush of water may cause a vacuum in the
small pipes, somewhat as the exhaust steam operates the air-brakes, and
empty the trap, leaving merely an open crooked pipe. Both these weak
points may be strengthened by a breathing hole in the highest part of
the small pipe below the trap. This must, of course, have a ventilating
pipe of its own, which, to be always effectual, should be as large as
the waste-pipe itself. (Fig. 3.)

[Illustration: Fig 3.]

[Illustration: Fig 4]

"Now, if the water that fills these traps and stops the open mouths of
the drains were always clean, there would be no further trouble from
this source. Unfortunately it is not; and although constant
watchfulness might keep it so, the safety that only comes from eternal
vigilance is an uncomfortable sort of safety--if we have too much of
it life becomes a burden. This particular ill might be remedied by some
contrivance whereby the upper ends of the waste-pipes should be
effectually corked--not simply covered, but _corked_ as tightly as a
bottle of beer--at all times except when in actual use. This would
doubtless be more troublesome, but indolence is at the bottom of most
of our woes: our labor-saving contrivances bring upon us our worst
calamities. Even this thorough closing of the outlet of washbasins and
bath-tubs, as they are usually made, would be of little avail, for they
are furnished with an 'overflow' (Fig. 4), through which exhalations
from the trap would rise, however tightly the outlet might be sealed.
It is also customary and doubtless wise, considering our habit of doing
things so imperfectly the first time that we have no confidence in
their stability, to place large basins of sheet-lead under all plumbing
articles, lest from some cause they should 'spring a leak' and damage
the floors or ceilings below them. One strong safeguard being better
than two weak ones, I would dispense with the 'overflow' and arrange so
that when anything ran over accidentally the lead basin or 'safe'
should catch the water and carry it through an ample waste-pipe of its
own t