Barn Construction. 115 



of cattle it may be found desirable to force air into the 

 barn from the outside. Ventilators regulated by the 

 action of the wind, with automatic check damper, as 

 shown in cuts (pages 113, 114). W. E. H. Massey, of 

 Toronto, has adopted this method with great success. 



The first cut shows an automatic ventilator which 

 revolves on ball bearings, and is kept facing the wind 

 on the principle of a weather vane, which keeps the 

 opening of the ventilator always facing the wind, 

 thus forcing the fresh air down the shaft. An auto- 

 matic damper in the shaft regulates the supply so 

 that a wind-storm could not drive in more air than 

 was needed. This automatic damper can be regu- 

 lated to suit any strength of current, or closed en- 

 tirely by hand. 



The draft of an outlet ventilator may likewise be 

 greatly increased by making the opening always face 

 in the opposite direction to the wind, as shown. 



While discussing this question of ventilation, I 

 may take this opportunity to call the reader's atten- 

 tion to the reason why it is particularly necessary 

 that dairy cows especially should be supplied with 

 a great abundance of fresh air aside from its health- 

 giving properties to all animals. Milk is a product 

 of the blood. Therefore, no cow can manufacture a 

 large quantity of milk without first manufacturing 

 a correspondingly large quantity of blood. The 

 blood is made from the food the cow consumes, but 

 in manufacturing a large quantity of blood a large 

 quantity of pure air is required to enter the lungs of 

 the animal to purify the same. So you see the re- 



