WARMING AND VENTILATION. 323 



Valves should be arranged to regulate the amounts of hot and cold 

 air so as to give a proper temperature to the mixture. 



When the lecture-room is not occupied, it will be well to close all the 

 communications with the ventilating-chimuey, the mixing-chamber, and 

 the fresh-air openings, in order to avoid reversed di;aughts which would 

 cool the interior. 



The intermittent use and heating of lecture-rooms causes a much 

 greater expense for fuel than if they were constantly occupied. 



These places also being only ventilated when they are in use, it is 

 well to reserve means of warming through special openings different 

 from those which are used in connection with ventilation, the openings 

 to be afterward closed. 



The mean results for heating and ventilating lecture-rooms arranged 

 similarly to those in the conservatory will be as follows : 



C" For heating — to 1,000 cubic feet con- 

 Consumption of coal ] tent 2-2^ lbs. 



in 12 hours. 1 For ventilation — to 1,000 cubic feet 



I of air renewed |-1 lb- 



Large reception-rooms, such as those of legislative halls, should be 

 warmed and ventilated upon the same principles. 



In all cases, it should be remembered that staircases, vestibules, &c., 

 which give access to these jjlaces with strong ventilating-draughts, should 

 be warmed without being ventilated, and kept at a temperature a little 

 above that of the main room, so that the occasional opening of doors 

 will only admit warm air, which would not be unpleasant. 



Experiment has shown at the Conservatory that, when these places 

 are thus heated and kept closed, they form a sort of air-lock, and the 

 velocity with which the air enters through the doors, which being 

 opened put them in communication with the interior of the lecture- 

 room, is barely one foot a second, and consequently almost insensible, 

 especially if the temperature of the air is at least equal to that in the 

 main room. 



THEATERS. 



122. A theater is composed of three principal parts — 



1. The stage and its accessories. 



2. The auditorium, waiting-rooms, and dependencies. 



3. The vestibules, staircases, and business-offices. 



The stage, the flies, and the corridors which lead to the dressing-rooms 

 and green room should be kept at a temperature of 04° to 08° in winter. 

 Generally, the latter places will not require to be ventilated, as they con- 

 tain but a small number of people, occupying a large space. Still, as 

 the green-room and the rooms in which the chorus rehearses often con- 

 tain a large number of artists, it may be necessary in certain cases to 

 ventilate them. The upper portions of the stage are often raised to a 

 high temperature on account of the heat produced by the lights, by the 



