4 6 



rises and seeks an outlet. The outlet is necessarily at the ceiling 

 and consists of a flue which passes through the roof. At the Experi- 

 mental Farm, the flues pass through an upper story. These should 

 extend well above the building for the same reason that a chimney 

 must do so in order to draw well. 



The inlets enter the stable at the floor level. The inlet pipe is 

 U-shaped and passes beneath the foundation wall. If the fresh 

 air is taken from a covered shed, the mouth outside may be near 

 the ground level and be protected by a grating. If however, the 

 air has to be drawn from outside, more especially in districts subject 

 to snow r fall, the pipe should extend 4 or 5 feet above ground and the 

 opening should be roofed so as to avoid the entrance of snow or rain, 

 or undue influence from the wind. The roofed pipe is built against 

 the wall, and the air enters through slots in the sides close against 

 the building. The size of these openings corresponds with the 

 capacity of the pipe inside. 



The ventilator works by virtue of the natural tendency of warm 

 air to rise. As the air warms, it becomes foul, rises and escapes by 

 the outlets. As nature abhors a vacuum, the escape of the warm 

 air creates a suction of fresh air by way of the inlet pipes. Since 

 the animals are constantly giving off warmth and expelling carbonic 

 acid gas, the warm, foul air is constantly escaping and cold, fresh 

 air is at the same time entering the stable, thus keeping up a 

 gentle, almost imperceptible, system of ventilation. To regulate 

 the ventilation, a damper is provided in the outlet flue. The clos- 

 ing of this also stops to a large extent the inflow of fresh air, as 

 the draught ceases, stopping the suction. By the original system, 

 the inlet pipe enters at the floor level. This is to facilitate a steady, 

 unobstructed, almost imperceptible flow of air through the stable 

 towards the outlets. To guard against chaff, and dust falling into 

 the opening, Mr. Grisdale, in the main cattle barn at the Farm 

 raised the openings about four inches above the floor level. 



The amount of ventilation necessary for a barn depends upon 

 the number of animals to be housed. Sufficient is needed to maintain 

 in cold weather a temperature of from 40 to 45 degrees Fahrenheit. 

 A well-built stable, stocked to a reasonable capacity, should have 

 the air changed every 30 to 45 minutes. Air removed at this rate 

 will carry off the foul air as it is expelled from the stock; it will also 

 remove the vapour, which, if allowed to remain, would condense 

 on the walls and ceilings. 



The intake and outlet flues should be about the same in capacity, 

 that is, provided the stable is tightly constructed. Because more 



