168 



wind strikes. Hence the openings serving as inlets one day or at 

 one moment may be outlets the next moment or any other day, 

 depending of course upon the direction of the wind. When calm 

 prevails, internal influences will exert the controlling forces as to 

 which openings shall act as inlets and which others as outlets. 



The controlling and limiting of the rate of inflow of air is 

 essential. The outflow will (usually require that the controls or keys 

 be fully open. The temptation to partially plug the holes with wisps 

 of hay or straw must be guarded against. 



SYSTEM OF VENTILATION ' B/ VENTILATION BY CONVECTION. 



Plan B rVentilation by Convection^ 



In the system described below, the proper distribution of pure 

 air throughout the stable depends for the most part upon convection 

 or circulation of air in the lower half of the stable due to the heat 



