VENTILATION 



77 



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entering the tube is directed upwards towards the ceiling, 

 and gradually mixes with the air of the stable without 

 causing a draught. 



These tubes externally require to be protected from 

 vermin, while their interior, it must be borne in mind, 

 requires to be periodically cleaned. They are not recom- 

 mended for stable purposes if any other 

 plan is available. 



A ventilating pillar somewhat on the 

 principle of a Tobin's tube is sometimes 



employed in stables (Fig. 20). It embodies 



the objection most tubes possess. 



Perforated bricks may be used as a 



useful inlet under some conditions. They 



are made in two sizes giving respectively 



11 J square inches and 24 square inches 



of ventilating surface. A form of air-brick 



with conical holes, the small hole being 



turned to the outside air, may also be use- 

 fully employed ; they are known as Ellison's 



(Fig. 19). The effect of the conical holes 



is to break the current and distribute the 



air. 



Air-bricks can only be a supplemental 



means of ventilation, when that afforded by 



windows is insufficient owing to structural 



defects in the building. In stable hygiene 



the drying and sweetening of the floor 



is a matter of the utmost importance, 



and this may be assisted by ventilating 



bricks being placed near the ground, espe- 

 cially where the other means of ventilation are defective. 

 In stables with bails if there be good window and door 



ventilation, ground inlets or air-bricks for drying the floor 



are not required. 



It is usual to regard the ridge ventilator as an outlet ; as 



a matter of fact it is both an outlet and inlet as previously 



described. The boards forming the louvre must be wide 



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Fig. 19. —Tobin's 

 tube. In the wall 

 above may be 

 seen Ellison's 

 Air-Brick. 



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