546 



Ri-:al)Ixg-Cul"rsi-: ixjr Farmers. 



than five minutes. It would doubtless be necessary for the wind to blow 

 more than ten miles an hour for it to enter an opening at that rate, but 

 the principle is not different from air forced into th.e room by means of 

 an electric fan. 



Under these conditions the air passes out because it is forced to do 

 so. The resistance will be slightly greater if the air is taken out nearer the 

 bottom of the room than at the ceiling, assuming that there is no other 

 force acting on the outlet. With a jiressure equal to wind blowing ten 

 miles an hour, the difference in resistance due to the position of the open- 

 ing would probably not materially affect the results. 



The wind, however, may also be made use of in exhausting the air 

 from the building. If an outlet flue extends above the roof so that the air 

 may blow freely across the top of it, the wind will act as an aspirator and 

 ])ull the air up the flue. A familiar example of the aspirator is the hand 

 sprayer used in spraying insecticides and fungicides. It is important that the 

 wind blow freely directly across the top of the flue. Care should be taken 

 so to construct the cover to the flue that the wind may cross freely from 

 every direction. The outlet flues should not empty into the ol 1-fashioned 

 slatted cupola because the cupola offers an obstruction to the free passage 

 of air across the top of the flue. It may be possible, however, to bring 

 the outlet of the flues into a group and combine them into a cupola which 

 will be effective. The important 

 thing is to allow the wind to 

 blow freely from all directions 

 across the top of the flues. 



Since in the temperate cli- 

 mates all conditions of weather 

 must be dealt with, it is a matter 

 of prudence to be able to modify 

 the rate at which the exchange 

 of air may take place. To those 

 who contemplate putting in the 

 so-called King system of ventila- 

 tion (too well known to need to 

 be described here), the writer 

 would suggest provision for an 

 ample exchange of air, the 



amount of which may be modified at will and also that an outlet be placed 

 both near the floor and also near the ceilin? in order that the rate of 



Fig. 324. — Outlet for air. Tin's tube may 

 be let down on cold n?.£,'/;/5 and hooked up 

 during daytime and during xvarni weather. 



