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EXPOSITION AT VIENNA.
metres in diameter, above the central chandelier of the auditorium. A steam-engine, of twelve horse-power, situated in the cellar below the main vestibule, sets a fan some three metres in diameter in revolution, which can force one hundred and twenty thousand cubic metres of air per hour into the rooms above. The cellar, which is more than seven metres in height, acts as a reservoir for the air, which is drawn iu through various channels, and has here in summer the opportunity to cool. It then passes upwards by several openings into the upper rooms, or, in winter, can be first led through a chamber heated by steam-pipes. The system is on the largest scale ever as yet applied. Below the auditorium is situated the inspection-room, from which all the machinery is regulated. Here the temperature is observed, the position of the valves, the steam pressure, etc., while speaking-tubes and electrical wires communicate with all parts of the building.
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Further information in regard to this building can be obtained from various works published in Vienna ; among them the " Technical Guide,”—also translated into French,—which appeared at the commencement of the Exhibition; also the work of A. Folsch,—"Fires in Theatres and their Protection against the Same,” and others.
The subject of ventilation, especially of that of schools, theatres, public buildings, etc., is still being investigated abroad, and eveiy year finds some advance in the methods employed. In Glasgow a university building, recently completed, is provided with a tower of great height, in which a steam-fan sucks in the air from the summit and diffuses it through the building. In this way a pure atmosphere is secured which does not exist in the lower strata of the air of this great manufacturing town. This is introduced through numerous small openings, placed under the seats in the lecture-rooms and at the lower parts of the walls, while the exit of the bad air above is assisted by an additional engine. In the new Exchange building of Vienna, extensive provision is being made for thorough ventilation, and below the cellar, channels of great size, connecting with exterior openings, twelve to fifteen feet square, furnish the requisite fresh air. Some of the simpler contrivances iu coffee-houses and dwell-