DAIRY CATTLE AND THE DAIRY FARM 127 



barn prevent it from working successfully. The circulation in and out 

 of the building is through specially constructed flues. The inlets are 

 placed on all sides of the barn and take air from the outside of the build- 

 ing, being located between the walls if they are hollow or, if they are of 

 solid masonry, through pipes and other special contrivances. The inlets 

 on the outside, open at the level of the window sill or lower, and on the in- 

 side, near the ceiling. This prevents the warm air rushing out as it 

 would if the inlets were carried straight through the walls, and on the 

 inside allows the fresh, cool, heavy outside air to slowly spread through 

 the stable without causing drafts. The combined area of the inlets 

 should equal or exceed that of the outlets, for air cannot leave the stable 

 faster than it comes in. 



The outlets are the vital part of the King system and so they should 

 be built with the greatest of care. Except where openings are provided 

 they should be made with permanently air-tight walls that only air from 

 the space to be ventilated rnay contribute to the current passing through 

 them. They should be of ample and uniform cross-section throughout 

 their length; it is the smallest section that determines the capacity of 

 the duct. Out-takes of circular or square cross-section are preferable 

 to long, narrow ones because there is relatively less surface to cool the air 

 and to make friction, hence there is less loss of pressure and greater 

 flow of air. The suctional effect of the wind and the motive power for 

 ventilation generated by temperature differences, increase with the height ; 

 but friction is augmented by height as it is also by bends and its effect 

 in decreasing motive power must be taken into account. The outlets 

 are located in the line of the stanchions in those barns in which the cows 

 face outward, and against the walls in those wherein the cows face inward. 

 The ducts are built of wood because it is a non-conductor of heat, and are 

 extended upward through the cupola or through the roof, either right above 

 the stanchions, if built in the stanchion line, or near the eaves, if built 

 against the walls. The latter way is least satisfactory because it gives 

 the barn an unsightly appearance, since the ducts have to be carried above 

 the ridge in order that downdrafts may not cause them to draw faultily. 

 At the top the duct is covered by a hood to keep out rain and to increase 

 the circulation by the passing of .air currents over the top but care should 

 be taken not to put the hood so close to the top of the outlet flue as to im- 

 pede circulation. For several reasons the outlets exhaust near the floor. 

 First, by doing so they effect the greatest movement of air possible with 

 the maintenance of proper temperatures. Second, by taking air at this 

 level they tend to promptly remove odors of the animals and of the manure ; 

 they also draw out the breathed air somewhat directly because on being 

 exhaled from the lungs it is cooled to about. 81F., at which temperature, 

 on account of its carbon dioxide content, it is heavier than the surrounding 

 air and tends to sink. Third, since it is the air of the lower levels that is 



