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Page:Popular Science Monthly Volume 56.djvu/100

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and boxes; in the gallery the openings for fresh air were located in the risers of the steppings. The air was exhausted by numerous openings under the seats in the parquet. This ventilating system was carried out at the Théatre Lyrique, the Théatre du Cirque, and the Théatre de la Gaieté.

Dr. Tripier ventilated a theater in 1858 with good success on a similar plan, but he introduced the air partly at the rear of the stage and partly in the tympanum in the auditorium. He removed the foul air at the floor level and separately in the rear of the boxes. He also exhausted the foul air from the upper galleries by special flues heated by the gas chandelier.

The Grand Amphitheater of the Conservatory of Arts and Industries, in Paris, was ventilated by General Morin on the downward system. The openings in the ceiling for the admission of fresh air aggregated 120 square feet, and the air entered with a velocity of only eighteen inches per second; the total air supply per hour was 630,000 cubic feet. The foul air was exhausted by openings in steps around the vertical walls, and the velocity of the outgoing air was about two and a half feet per second.

The introduction of the electric light in place of gas gave a fresh impetus to the downward method of ventilation, and mechanical means also helped to dispel the former difficulties in securing a positive downward movement.

The Chicago Auditorium is ventilated on this system, a part of the air entering from the rear of the stage, the other from the ceiling of the auditorium downward. This plan coincides with the proposition made in 1846 by Morrill Wyman, though he admits that it can not be considered the most desirable method.

A good example of the downward method is given by the New York Music Hall, which has a seating capacity of three thousand persons and standing room for one thousand more. Fresh air at any temperature desired is made to enter through perforations in or near the ceilings, the outlets being concealed by the decorations, and passes out through exhaust registers near the floor line, under the seats, through perforated risers in the terraced steps. About 10,000,000 cubic feet of air are supplied per hour, and the velocity of influx and efflux is one foot per second. The air supplied per person per hour is figured at 2,700 cubic feet, and the entire volume is changed from four and a half to five times per hour. The fresh air is taken in at roof level through a shaft of seventy square feet area. The air is heated by steam coils, and cooled in summer by ice. The mechanical plant comprises four blowers and three exhaust fans of six and seven feet in diameter.

The downward method of ventilation was suggested in 1884