VENTILATION.

"_The House_ [_of Commons_] _met to-day_ [_27th April_] _after the
Easter holidays--and honourable members, on entering, seemed highly to
appreciate the unusual luxury of a little fresh air._"--THE TIMES, 28th
April.

The failure of some late attempts to ventilate public buildings invites me
to set forth an _Encyclopaedia of ventilation_--at a cheap rate, and in a
compendious form.

Aware of the abilities and celebrity of many of the writers on this
subject--from Whitehurst and Franklin to Reid and Gurney--I must ward off
the imputation of self-conceit by expressing my belief that the errors of
those who have failed should be chiefly ascribed to excessive cleverness;
to unadvised attempts at outwitting nature! I hope to escape that snare. In
the execution of my humble task, I shall entirely rely on common sense and
common experience.

Air is essential to human life, and as respiration destroys its vital
qualities, the _ventilation_ of rooms which are intended for habitation
should be a primary object in all architectural plans.

Architects, however, seldom provide for the ventilation of rooms otherwise
than as they provide for the admission of light. Now the properties of
light and air, with reference to our domestic requirements, differ in some
important particulars--of which it may not be amiss to give a brief
enumeration.

_Light_ moves with uniform velocity: _air_ is sometimes quiescent, and
sometimes moves at the rate of thirty miles an hour. _Light_ diffuses
itself with much uniformity: _air_ passes in a current from the point of
its entrance to that of its exit. _Light_, whatever be its velocity, has no
sensible effect on the human frame: _air_, in the shape of a partial
current, is both offensive to the feelings and productive of serious
diseases. _Light_, once admitted, supplies our wants till nightfall: _air_
requires to be replaced at very short intervals. _Light_ may be
conveniently admitted from above: _air_ requires to be admitted on the
level of the sitter. _Light_, by the aid of ground glass, may be modified
permanently: _air_ requires to be variously adjusted according to its
direction, its velocity, the seasons, the time of the day, the number of
persons assembled, &c.

An attentive consideration of the above circumstances leads me to certain
conclusions which I shall now state aphoristically, and proceed to describe
in more detail.

A room designed for a numerou