AIR AND VENTILATION 



97 



lets for cow byres are ordinary fireclay drain pipes of about 4 inch 

 diameter. These may be set level through the wall or placed 

 at an angle that gives the incoming air an upward trend. In the 

 west of Scotland it is the 

 common custom to put one 

 drain pipe between each pair 

 of cows placed level and just 

 above the food-trough. In 

 some byres they are placed on 

 a level with the cows' heads 

 when they are standing. In 

 some instances bent pipes are 

 used in order to break the 

 force of the incoming air. To 

 those unaccustomed with this 

 free method of ventilating 

 byres it might appear to be 

 too " draughty," but those 

 dairymen who have adopted 

 it speak very highly in its 

 favour. Inlet boxes are 

 sometimes fitted with regul- 

 ating valves. 



Air Bricks and Gratings. 

 Air bricks, as their name 

 suggests, are perforated 

 bricks for the admission of 

 air. They are of various 



j 



designs and sizes. Theoretic- 

 ally the inlet area is con- 

 sidered to be one-third of the 

 brick face area. When the 

 bricks have been in place for 

 any length of time they get 



partly blocked with dust and FIG. 34. Tobin's Tube. A box containing 



11 A i i a regulator is fitted at the top of the 



cobwebs. Air bricks are tube * The broken line ^ the 



usually placed in a COntinu- method of building a Tobin's tube in- 

 ous row along the wall just 



under the eaves ; when large enough and in sufficient number they are 

 useful adjuncts to the main ventilating system. Jennings' bricks 

 are air bricks constructed so that the incoming air is given an upward 

 trend. Another type, Ellison's brick, has the holes on the outside of 

 the building smaller than those inside, so that as the air enters its 

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