4. Elevators, stairways, and other openings from floor to floor should be cut off by properly constructed hatches, doors, or other means, automatic in action, if possible.
5. Openings in party-walls and exposed windows should be protected by wooden doors or shutters, covered with tin, preferably self-acting.
6. Rooms in which special danger exists should be plastered on wire lathing close to the surface of the ceiling, and following the line of the timbers. All iron posts in exposed places, or iron or stone posts, on which the safety of a building greatly depends, should be protected from fire, either with wood or tin, or by wire lath and plastering.
Of materials for walls, brick is best, and sandstone next best. Limestone calcines and crumbles at high temperatures, and granite breaks and cracks most dangerously. When gas is used in lighting a mill, it is proper to have a controlling valve external to the mill, so as to cut off the supply in case of fire. Sometimes gas is carbureted with gasoline, in which case, fifteen minutes before a mill ceases work at night, the uncarbureted gas is alone permitted to be used, so as to take up any liquid deposited in the pipes. When electric lighting is adopted, approved rules for its installation and use must be observed.
Whenever possible, mills should not exceed one story in height. When so constructed, they can be better lighted than lofty buildings, and they are much less liable to costly vibration. This latter source of loss in a mill four or five stories in height may absorb a fifth of the motive power. A one-story mill, in case of fire, is much more safe and manageable than a lofty structure. It is pleasant to find so potent economic arguments against the tendency which, in recent years, has piled up factories so high, and crowded them together so closely.
Steam-pipes, for heating purposes, have been found quite as effective when suspended from the ceiling as when placed upon the floor; while, in the former case, they do not furnish lodgment to cotton-waste, paper, shavings, and other combustible material. Similar refuse is apt to gather dangerously about a steam-pipe rising through a floor—the means of safety here being its inclosure in a cast-iron shield of conical form. Steam-pipes require careful protection from contact of inflammable substances. Of non-conducting covering materials, asbestus, hair-felt, cork, fossil-meal, magnesia, and rice-chaff are the best.
The rules here presented in mere outline arc given in detail by Mr. C. J. H. Woodbury, inspector of the Boston Manufacturers' Mutual Insurance Company, in his work on the "Fire Protection of Mills." They are the outcome of the long and varied experience of the Mutual Companies of New England. Of these companies, the one I have just mentioned is the foremost, and I am indebted to its president, Mr. Edward Atkinson, for data included in this sketch. From an analysis of the causes of fires in which his company was interested
