HOUSING AND CARE OF COWS 83 



of the barn, and should be carried straight upward like a chimney, 

 six feet higher than the top of the roof. 



The shaft or flue should be absolutely air-tight, and may be 

 made of metal, covered with building paper, or preferably of two 

 layers of wood, with filling of sawdust or building paper between, 

 and covered with a cap, to keep the rain out, one foot above the top. 

 The openings near the floor and at the ceiling should be provided 

 with doors or dampers of some kind. The number of flues and size 

 of flues are governed by the number of cows in the barn. Only 

 one flue is necessary for the out-take of air when there are less 

 than thirty cows in the barn. 



1 flue 1 ft; square for 6 cows. 



I " 1X2 " " " 10 " 



1 " 2X2 " " " 20 



2 " 2X2" " " 40 " 



3 " 2X2 " " " 100 " 



The movement of air in the ventilating system is brought 

 about by the following forces : Wind pressure against the barn, 

 forcing air into the building; wind suction on leeward side, tending 

 to suck air out ; wind blowing across top of ventilating shaft, tend- 

 ing to suck air out of it ; by difference of temperature between the 

 air inside and that outside the building. Thus air enters the intake 

 near the ceiling and is distributed over the building. The air at 

 the bottom of the barn is the coldest. In cold weather the bottom 

 opening of the out-take shaft should be open, and the upper opening- 

 near the ceiling shut. The cold air is then sucked from the 

 floor of the barn up the flue into the outer air. In hot weather 

 the upper opening in the out-take flue may be opened, and the 

 lower closed. This permits of escape of heated air from the stable, 

 and may be done at any time to secure. better ventilation, but at 

 the expense of the animal heat. In order that the system work 

 well, it is essential that every part of the barn be absolutely tight, 

 with well-insulated walls to prevent chilling and condensation of 

 moisture, as about ten pounds of water are eliminated daily from 



