eing constructed of bricks set in cement, the
privy being placed at a distance from the house, the shed over it
ventilated, and the contents of the privy removed regularly and at
stated intervals, before they become a nuisance. At its best, however,
the privy vault is an abomination, as it can scarcely be so well
constructed as not to contaminate the surrounding soil, or so often
cleaned as to prevent decomposition and the escape of poisonous gases.

_The Pail System_ is an economic, simple, and, on the whole, very
efficient method of removing fresh excreta. The excreta are passed
directly into stone or metal water- and gas-tight pails, which, after
filling, are hermetically covered and removed to the places for final
disposal. This system is in use in Rochedale, Manchester, Glasgow, and
other places in England.

The pails may also be filled with dried earth, ashes, etc., which are
mixed with the excreta and convert it into a substance fit for
fertilization.

_The Pneumatic System_ is a rather complicated mechanical method
invented by Captain Lieurneur, and is used extensively in some places.
In this system the excreta are passed to certain pipes and
receptacles, and from there aspirated by means of air exhausts.

=The Water-carriage System.=--We now come to the modern mode of using
water to carry and flush all sewage material. This method is being
adopted throughout the civilized world. For it is claimed a reduction
of the mortality rate issues wherever it is introduced. The
water-carriage system presupposes the construction and existence of
pipes from the house to and through the street to the place of final
disposition. The pipes running from the house to the streets are
called house sewers; and when in the streets, are called street
sewers.

=The Separate and Combined Systems.=--Whenever the water-carriage
system is used, it is either intended to carry only sewage proper,
viz., solid and liquid excreta flushed by water, or fain water and
other waste water from the household in addition. The water-carriage
system is accordingly divided into two systems: _the combined_, by
which all sewage and all waste and rain water are carried through the
sewers, and the _separate_ system, in which two groups of pipes are
used--the sewers proper to carry sewage only, and the other pipes to
dispose of rain water and other uncontaminated waste water. Each
system has its advocates, its advantages and disadvantages. The
advantag