WAEMING AND VENTILATION. 



279 



most cases, should be carried directly to the foot of the ventilatiug- 

 shaft. 



The latter should be placed for its whole length beside the smoke-pipe 

 of the heater, the heat from which will assist the draught. Bui tliis heat 

 will not usually be suflicient to give proper activity to the draught eveu 

 when the external temx>erature is very low, and it will be necessary to 

 keep up a little coal-fire at the bottom of the ventilating-shaft in a. grate 

 detached from the walls. 



If local arrangements prevent making the fire at the bottom, it may 

 be made at the floor-level or at the top, keeping the ventilatiiig-opeu- 

 ings, however, in the vertical walls and near the floor. 



The fresh air, warm or cold, should be admitted near the ceiling, and 

 preferably parallel to its surface. In the season for fires, the air sup- 

 lilied by the heater should be mixed with the external cold air. The 

 jn'oportion of each may be regulated by means of registers easily con- 

 trolled from the interior of the room, so that the mixture may have only 

 the temperature of 85° to 95° at most. 



The fresh-air openings should be arranged, if possible, along the 

 whole length of the room, or at least be very numerous, and their sec- 

 tion calculated so that the entering air should have a velocity of 40 

 inches a second, if it is directed horizontally parallel to the ceiling, or 

 20 inches, if it has a vertical direction. 



G2. Example. ScJiool in the Rue des 

 Fctits-HoteJs, Paris, (Fig. 15.)— This 

 school-building is intended for two 

 perfectly distinct uses. The ground 

 floor is used for the children's play- 

 room. It is unnecessary to ventilate 

 it, and a single stove is sufhcient to 

 warm it. 



The second floor is occupied by the 

 primary school kept by the Christian 

 Brothers, and is divided into four 

 rooms, intended for 400 children. 

 The capacity of these rooms corre- 

 sponds to a mean of 155 cubic feet for 

 each child, which is about the pro- 

 portion adopted by the city govern- 

 ment, and seems to us totally insuffi- 

 cient; 250 to 280 cubic feet for eacli 

 child appears the proper amount, es- 

 pecially as many schools for children 

 are used in the evening as schools for 

 adults. 



The third floor is devoted to a drawing-school under the charge of a 

 private professor, and contains 270 desks, of which 200 are in the main 



