24 JOURNAL AND PROCEEDINGS 



raised to 65° would take up double what it required to saturate 

 it at 40°, and if this moisture is not supplied it becomes very 

 dry and consequently irritating to the air passages. There 

 should therefore be provision made to supply this aqueous 

 vapor. Careful investigation has shown that the most 

 healthful condition of the air is 73 per cent, of saturation. 

 The amount of moisture is of vital importance. How fre- 

 quently we see people leave church or public halls with a fit 

 of coughing. This is caused by the dryness of the air, or by 

 some animal matter which has become burnt in contact with 

 highly heated iron. 



The openings for admitting the air should be as low as 

 possible if the openings for escape are high, otherwise the 

 pure air will escape without being of much benefit to the 

 occupants of the room. This is especially true when the air 

 is warm when admitted. It is better to admit the warm air 

 above the breathing line and draw it off from a lower level, or 

 as near the floor as possible, this insures the passing of the 

 pure air across the breathing line. We have two well-defined 

 systems of ventilation, the Plenum system and the Vacuum 

 system. In the former the air is forced into the room by 

 artificial means, and is only lately coming into use. It should 

 always be supplemented by the natural system when it will 

 give much better results. A fan is placed in a flue which 

 propels the air over heated steam coils, and then into the 

 rooms. After becoming heated the air should pass over pans 

 of warm water to supply the necessary moisture, the air then 

 passes into the room at a medium height, while the foul air is 

 drawn off from the room through openings near the floor con- 

 nected with a ventilating shaft, kept warm to assist the 

 motion of the air. This system could be used in the summer, 

 for the air drawn from the higher level is cooler, or might be 

 still more cooled by passing cold water through the pipes. 

 This system will likely come into general use for all public 

 buildings. The Vacuum system has a large ventilating shaft 

 in which there is a fire, steam or hot water coils, or the pipe 

 from the furnace may pass up through it. The air in the shaft 



