324 WARMING AND VENTILATION. 



fire in spectacles, &c., which requires that special precautions be taken 

 to air them and to remove the hot gases. 



The auditorium aud the waiting-rooms are the parts in which it is especi- 

 ally desirable to maintain salubrity, change of air, and a moderate tem- 

 perature. The amount of air to be changed an hour to each sjjectator 

 should be 1,400 cubic feet, and it is well to reserve means of increasing 

 it to 2,100 cubic feet during the summer. 



The heating may be effected either by means of hot-air heaters with 

 sufficiently large mixiug-chambers, as has been previously mentioned, or 

 by hot-water apparatus, of which the first cost need not be greater than 

 the preceding, while it will be very easy to regulate. 



123. Air-supply. — The fresh air should be taken, if possible, from the 

 neighboring gardens, far from dwelling-houses, or from court-yards, or 

 by special chimneys, drawing it from the top of the edifice. Care should 

 be taken that these chimneys should be as far as possible from the 

 ventilating-chimneys, and that their tops be not as high as the ventilat- 

 ing chimneys, in order that they may not reverse the draught. 



If fresh air be introduced by subterranean passages, the walls, the 

 vaults, and the floor of these passages should be made of hydraulic 

 masonry, perfectly tight, and nothing should be done to them by the 

 custodians of the building, except to examine their state of cleanliness. 



124. Admission of air. — The air should be carried into the auditorium : 



1. By interjoists, formed between the floor of one gallery and the 

 ceiling of that below ; the air should issue horizontally from the whole 

 circumference of the interjoists, which should be at least 5 or 6 inches 

 in clear height. 



It may be assumed that the horizontal velocity with which it flows 

 out will be 3 feet a second ; but it is necessary to take care that the 

 openings through the gratings which terminate the interjoist-spaces 

 have at least a surftice corresponding to this velocity, and that none of 

 these openings be placed horizontally above the spectators of the lower 

 tier of seats. 



2. By openings arranged at the height of about 10 feet in the walls 

 separating the stage from the auditorium ; and there may also be formed 

 there a chamber for mixing the warm air from the heaters with the cold 

 air from outdoors. 



3. By auxiliary pipes, intended especially for summer-ventilation, 

 arranged, if possible, under the floors of the corridors of each gallery. 

 They should take air from outdoors, and their section should be cal- 

 culated, so that the velocity of passage shall not exceed 2 feet or 28 

 inches a second. All these pipes should be supplied with valves to 

 close them when required in cold weather. 



125. Necessary precautions.— Ventilation, by drawing out the foul air, 

 necessarily causing the entrance of fresh air, it is necessary to see that 

 the opening of doors does not occasion unpleasant currents. For 

 this purpose, corridors, passage-ways, and staircases should be heated in 



