fire-doors to satisfactorily fulfil the purpose of resisting fire. The
best form of fire-door is that made of two thicknesses of matched
boards, placed at right angles to each other and nailed together, being
covered on the outside with tin, securely locked together and held to
the door by numerous hanging-strips. The door should be secured to the
hangers by means of bolts, and not screws, and the rail upon which it
runs strongly bolted to the wall. When closed, such a door should fit
into a jamb and be securely held in this manner against the wall. Such
doors are frequently hung upon an inclined track, and, by some
application of highly fusible solder at the catch, are so arranged that
they will be closed by the heat of a fire, if not closed by hand.

In this treatment of the arrangement of buildings to resist fire,
consideration has not been given to the cost of land, which is, of
itself, an important factor in determining what arrangement will be the
most expedient for an establishment. Where land is expensive, or there
are limitations in the space suitable for building, it is frequently
necessary to build mills and shops higher than would be warranted by
good judgment under other conditions; but where circumstances will
permit it, the one-story mill has been very successful, not merely in
immunity from fire, and very low cost per square foot of floor, but also
in the advantages of manufacturing, particularly in regard to cost of
supervision and movement of the stock in process of manufacture. These
are questions which must be determined, not merely in regard to the
various processes of manufacture, but the individual needs of each
concern; the position of the fire-risk in the matter being that the
hazard of a building increases very rapidly with its height, and to some
extent with its area.

The extension of one-story buildings over too large an area will not be