72 YETERINAEY HYGIENE 



air is thrown before it reaches the ground. The window on 

 the lee side is the principal outlet, but the air does not 

 escape from it until the incoming air is well mixed. If, on 

 the other hand, the lee window be fully open while that on 

 the windward side be only half open, the tendency of the 



Fig. 9. — Direction taken by air currents when opposite windows are 

 half open. 



incoming air is to escape direct at the lee window without 

 proper mixing. 



When the windward window is half open and the lee 

 window closed, the incoming current is directed towards 

 the ceiling, descending fan-shaped and well mixing with 



Fig. 10.— Direction taken by air cnrrents when all doors and windows 

 are closed. 



the stable air; the ridge under these conditions acts as a 

 fairly regular outlet. 



If all the windows be closed and the doors only left open, 

 the ridge acts as a fairly regular outlet. With doors and 

 windows shut the ridge is an inlet on the windward side 

 and an outlet on the lee side (Fig. 10.) 



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