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 for the improvement of the ventilation of the Senate chamber and the chamber of the House of Representatives in the Capitol at Washington, but the system was not adopted by the Board of Engineers appointed to inquire into the methods. The downward method is also used in the Hall of the Trocadéro, Paris; in the old and also the new buildings for the German Parliament, Berlin; in the Chamber of Deputies, Paris; and others. Professor Fischer, a modern German authority on heating and ventilation, in a discussion of the relative advantages of the two methods, reaches the conclusion that both are practical and can be made to work successfully. For audience halls lighted by gaslights he considers the upward method as preferable.