68 



VETEEINAEY HYGIENE 



therefore, under natural ventilation to point out any open- 

 ings as being always inlets or always outlets, though we 

 shall presently have to qualify this statement somewhat, in 

 dealing with the mechanical contrivances known as cowls. 

 With this caution we shall continue to employ as a matter 

 of convenience the terms inlet and outlet as applied to 

 ventilators. 



Inlets and outlets are of various kinds, viz. doors, 

 windows, tubes surmounted by downcast or upcast cowls, 

 perforated bricks, openings in the ridge of the roof with or 

 without louvres, and holes placed in the wall. 



Doors need no special consideration, the tendency is 



Fig. 4. — Sheringham ventilating'window (Musgrave). 



always to shut them, and in calculating the air require- 

 ments they must be left out of question as they will 

 certainly be closed at night, at which time the greatest air 

 impurity exists. As a means of flushing the stable during 

 the day, drying the floor, and thoroughly perflating the 

 building, they have no equal if they exist in sufficient 

 number for the size of the structure, and especially if they 

 are placed on opposite sides of the stable. 



Winclou's as the chief means of natural ventilation require 

 some detailed consideration. In most modern stables they 

 are arranged on the principle of a Sheringham valve 

 (Fig. 4), by which the air is directed upwards in order to 

 prevent a draught. 



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