The entrance halls, vestibules, lobbies, staircases, and corridors do not need so much ventilation, but should be kept warm to prevent annoying draughts. They are usually heated by abundantly large direct steam or hot-water radiators, whereas the auditorium and foyers, and often the stage, are heated by indirect radiation. Owing to the fact that during a performance the temperature in the auditorium is quickly raised by contact of the warm fresh air with the bodies of persons (and by the numerous lights, when gas is used), the temperature of the incoming air should be only moderate. In the best modern theater-heating plants it is usual to gradually reduce the temperature of the air as it issues from the mixing chambers toward the end of the performance. Both the temperature and the hygrometric conditions of the air should be controlled by an efficient staff of intelligent heating engineers. But little need be said regarding theater lighting. Twice during the present century have the system and methods been changed. In the early part of the present century theaters were still lighted with tallow candles or with oil lamps. Next came what was at the time considered a wonderful improvement, namely, the introduction of gaslighting. The generation who can remember witnessing a theater performance by candle or lamp lights, and who experienced the excitement created when the first theater was lit up by gas, will soon have passed away. Scarcely twenty years ago the electric light was introduced, and there are to-day very few theaters which do not make use of this improved illuminant. It generates much less heat than gaslight, and vastly simplifies the problem of ventilation. The noxious products of combustion, incident to all other methods of illumination, are eliminated: no carbonic-acid gas is generated to render the air of audience halls irrespirable, and no oxygen is drawn to support combustion from the air introduced for breathing. It being now an established fact that the electric light increases the safety of human life in theaters and other places of amusement, its use is in many city or building ordinances made imperative--at least on the stage and in the main body of the auditorium. Stairs, corridors, entrances, etc., may, as a matter of precaution, be lighted by a different system, by means of either gas or auxiliary vegetable oil or candle lamps, protected by glass inclosures against smoke or draught, and provided with special inlet and outlet flues for air.