e outside of such posts
up to the line of the windows. A sheathing on the outside plank
between the timbers is laid vertically and fastened to horizontal
furring strips. In some instances a small amount of mortar is placed
over each of the furring strips. The reason for this arrangement is to
prevent the formation of vertical flues, which are such a potent
factor in the extension of fires.

WINDOWS.

Light is often limited or misapplied on account of faulty position or
size of windows. The use of pilastered walls permits the introduction
of larger windows, which are in most instances virtually double
windows, the two pairs of sashes being set in one frame separated by a
mullion. A more recent arrangement, widely adopted in English
practice, is to place a swinging sash at the top of the window, which
can be opened, when necessary, to assist in the ventilation, while the
main sashes of the window are permanently fixed.

Rough plate glass is used in such windows, because it gives a softer
and more diffused light, which is preferred to that from ordinary
clear glass. White glass may be rendered translucent by a coat of
white zinc and turpentine.

The top of a window should be as near the ceiling as practicable,
because light entering the upper portion of a room illuminates it more
evenly, and with less sharply marked shadows, than where the windows
are lower down.

The walls below the windows should be sloped, in order that there may
be no opportunity to use them as a resting place for material which
should be placed elsewhere.

FIRE WALLS.

Brick division walls should be built so as to constitute a fire wall
wherever it is practicable to do so. Such walls should project at
least three feet above the roof, and should be capped by stone, terra
cotta, or sheet metal. They must form a complete cut-off of all
combustible material, especially at the cornices.

FIRE DOORS.

All openings in such walls must be provided with such fireproof doors
as will prove reliable in time of need. Experience with iron doors of
various forms of construction show that they have been utterly
unreliable in resisting the heat of even a small fire. They will warp
and buckle so as to open the passageway and allow the fire to pass
through the doorway into the next room.

A door made of wood, completely enveloped by sheets of tinned iron,
and strongly fastened to the wall, has proved to resist fire better
than any door which can be a