112 Barn Construction. 



they can get it pure. We have now provided for 

 the entrance of fresh and the exit of heated and im- 

 pure air, but we should still provide a place of exit 

 for the impure air that is heavier than the fresh air. 

 This is accomplished by an air duct opening lower 

 than the entrance of the fresh air, and must be car- 

 ried by a tile duct or conductor pipes and allowed to 

 discharge underneath the barn or lower than the 

 barn floor, or allowed to discharge into the liquid 

 manure cistern, in which case a swinging damper 

 closes automatically if air attempts to enter through 

 this duct from the outside. The cut (page 1 1 1) shows 

 this air taken from the gutter behind the cows and 

 in a tile drain discharging into the liquid manure 

 cistern. This same- pipe also provides an escape 

 for the light foul air or gases that may rise from 

 the cistern, as shown in the cut at B. This is 

 simply a galvanized conductor pipe that is carried 

 above the building on the principle of trapping a 

 sewer pipe discharging into a cesspool. If cattle 

 barns were thoroughly and properly ventilated, there 

 would in all probability be less tuberculosis among 

 our herds than there is at present. Pure invigorating 

 air is the best of all preventives, if not a cure, to con- 

 sumption in the human family; why not in cattle? 

 The fresh air comes into the barn through shaft 

 A 7, and is conducted along on an air duct directly in 

 front of the cattle, as shown, discharging into each 

 manger (see page in). This air shaft in front of 

 the manger comes into the stable at each end of the 

 barn (as shown on page 1 1 1 for a small number of 



