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 applied to general use. I have seen such doors in division walls where they had successfully resisted the flame which destroyed four stories of a building filled with combustible material, without imposing any injury upon the door except the removal of the tin on the sheet iron; and the doors were kept in further service without any repairs other than a coat of paint.

The reason for this resistance to fire is that the wood, being a poor conductor of heat, will not warp and buckle under heat, and cannot burn for lack of air to support combustion. A removal of the sheet metal on such a door after a fire in a mill shows that the surface of the wood is carbonized, not burned, reduced to charcoal, but not to ashes.

Many fire doors are constructed and hung in such a manner that it is doubtful whether they could withstand a fire serious enough to require their services.

The door should be made of two thicknesses of matched pine boards of well dried stock, and thoroughly fastened with clinched nails. It should be covered with heavy tin, secured by hanging strips, and the sheets lock-jointed to each other, with the edge sheets wrapping around, so that no seam will be left on the edge.

Sliding doors are preferable to swinging doors for many reasons, especially because they cannot be interfered with by objects on the floor. But, if swinging doors are used, care should be taken that the hinges and latches are very strong, and securely fastened directly to the walls, and not to furring or anything in turn attached to the walls. The portion of the fixtures attached to the doors must be fastened by carriage bolts, and not by wood screws.

Sliding on trucks is the preferable method of hanging sliding doors, inclined two and one half inches to the foot, and bolted to the wall. The trucks should be heavy "barn door hangers," bolted to the door; and a grooved door jamb, of wood, covered with tin similar to the door, should receive it when shut. A step of wood will hold the door against the wall when closed. A threshold in the doorway retards fire from passing under the door, and also prevents the flow of water from one room to another.

These doors are usually placed in pairs, and sometimes an automatic sprinkler is placed between them.

Fire doors should always be closed at night. In some well ordered establishments there is a printed notice over each door directing the night watchmen to close such doors after them. In a storage warehouse in Boston, the fire doors are connected with the watchman's electric clock system, so that all openings of fire doors are matters of record on the dial sheet.

Fire doors should certainly be closed at times of fire; yet, that such doors are open at night fires, or left open by fleeing help at day fires, is an old story with underwriters. A simple automatic device can be used to shut such doors. It consists of two round pieces of wood with a scarfed joint held by a ferrule, forming a strut which is placed on two pins, keeping the door open, as other sticks have long since served like purposes.

The peculiarity of this arrangement is that the ferrule is not homogeneous, but is made up of four segments of brass soldered together with the alloy fusible at 163 degrees Fahr., which is widely known for its use in automatic sprinklers. When the solder yields, the rod cripples, and the door rolls down the inclined rail and shuts. At any time the door can be closed by removing one end of the rod from one of the pins and allowing it to hang from the other pin.

Mill Towers

Because of economic reasons for preserving the space within the walls of the mill so that it may be to the greatest extent available for the best arrangement of machinery, the stairways should be placed outside of the building. Such stairways should not be spiral stairways, but should be made in short straight runs with square landings, because in the spiral stairway the portion of the stairs near the center is of so much steeper pitch that it renders them dangerous when the help are crowding out of the mill.

The wear of stairs from the tread of many feet presents a difficult problem. A very common practice consists in covering each tread with a thin piece of cast iron marked with diagonal scores, and generally showing the name of the mill. These treads wear out in the course of time, but for this use they answer very well, although somewhat slippery.

A wood tread gives a more secure foothold upon the stairway; and in some instances stairs have been protected by covering the treads with boards of hard wood, containing grooves about three-eighths of an inch deep, and of similar width, with a space of half an inch between them. These boards are grooved on both sides and placed on the stairs. After the front edge is worn, they are turned around so as to present the other edge to the front, and, in course of time, turned from the exposed side to do service in two positions on the other side. In this manner these tread covers are exposed to wear in four different positions.