WARMING AND VENTILATION. 303 



When ordinary heaters are used for heating, the warm air which 

 they supply should be introduced before its admission into the halls 

 into a mixing-chamber, where a sufficient quantity of external air is 

 also admitted, in order to moderate as required the temperatjire of the 

 air supplied to the rooms. 



To secure the proper mixture of external air with the warm air from 

 the heating-apparatus, it will be necessary to keep the fresh air above 

 the current of warm air by means of more or less wide partitions. It 

 will then happen that, as the first or denser stratum tends to fall while 

 the second or lighter stratum rises, the mingling will necessarily take 

 place. This applies as well to separate and direct openings for the ad- 

 mission of warm and fresh air in halls as to those for the admission of 

 air into the mixing-chambers. The partitions should be made of brick 

 laid flat, and be at least two inches thick. 



During the period of fires, the temperature of the inflowing air should, 

 for healthful ventilation, differ as little as possible from that intended 

 to be kept up in the halls, which should be uniformly about 00°. 



The mixing-chambers should be formed either in the floor above the 

 the heaters or in the corridors or small rooms. 



Eegisters should be placed in the mixing-chambers, to permit the 

 temperature of the air suj^plied by them to be regulated at will. 



Similar arrangements should be made when hot-water or steam heat- 

 ing-apparatus is used. 



If the hospital stands by itself and is in a healthial location, the 

 external-air supply may be taken either at the ground-level from the 

 middle of a lawn or flower-bed, as at Vincennes and the lying-in hospital 

 at St. Pptersburg, or at the level of each floor. 



Descending currents will not be required to carry the air from a cer- 

 tain height, except in cases where the jiroximity of more or less un- 

 healthful buildings would lead to the fear of infection in the air at the 

 ground-level. 



In that case, the chimney for bringing in air should be placed as far 

 as possible from that for carrying it off. The sectional area of the 

 former, and in general that of all external openings for the admission 

 of air, should be calculated so that the velocity of admission should 

 not exceed 2 feet a second, in order that the draught produced in the 

 vicinity of the openings may only extend a small distance. 



The openings for the admission of air entering at a considerable height 

 should be provided with valves or doors, which may close them if re- 

 quired. 



In summer, when the action of the draught in drawing in fresh air is 

 not assisted by the increase of temperature which the heating-apparatus 

 gives to the fresh air in winter, there should be made in the walls, espe- 

 cially on the faces exposed to the north or the east, auxiliary openings 

 similar to those previously mentioned, and capable of being opened or 



