94 POPULAR SCIENCE MONTHLY. 



tance in preventing the smoke and fire gases from being drawn 

 into the auditorium and suffocating the persons in the gallery 

 seats. 



Wliere the stage is lit with gaslights it is important to provide 

 a separate downward ventilation for the footlights. This, I be- 

 lieve, was first successfully tried at the large Scala Theater, of 

 Milan, Italy. 



The actors' and supers' dressing rooms, which are often over- 

 crowded, require efiicient ventilation, and other parts of the build- 

 ing, like the foyers and the toilet, retiring and smoking rooms, 

 must not be overlooked. 



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 abun- 

 dantly large direct steam or hot-water radiators, whereas the audi- 

 torium and foyers, and often the stage, are heated by indirect 

 radiation. Owing to the fact that during a performance the tem- 

 perature 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 efiicient staff of intelligent heating 

 engineers. 



But little need be said regarding theater lighting. Twice dur- 

 ing 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. I^ext 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 elec- 

 tric light was introduced, and there are to-day very few theaters 

 which do not make use of this improved ilium inant. 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 beine: now an established fact that the electric liffht in- 



