VENTILATION 



79 



that there need be no difference in the size of the two 

 openings. 



In calculating the size of inlets for natural ventilation no 

 other force than that of the wind need be regarded. The 

 size of the inlet must depend upon the velocity of the 

 incoming air. 



One square foot of inlet with a calm wind, viz., a mean 

 velocity of three miles an hour, will supply a horse with 

 the full amount of air required. But there are many 

 conditions which render it undesirable to limit ourselves to 

 inlet openings of one square foot, for example, one window 

 has frequently to be an inlet for two horses or even more, 

 it is, therefore, safer to say the ventilating inlet area shall 



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» «» «» «B» ^» ^ss, <g 

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Fig. 21. 



Fig. 22. 



Air-bricks. 



not be less than three square feet per head, and shall be 

 under control. This latter, as pointed out previously, can 

 be effected with a Sheringham window. 



Under some circumstances, especially in private stables, 

 it may be considered desirable that some portion of the 

 ventilating area should not be under control, in this case 

 air-bricks near the ground and under the eaves may be 

 employed. 



If the question of air-currents in the type of stable 

 described on p. 63 has been made clear, it is evident that 

 each inlet window must supply air to two horses, viz., those 

 opposite to each other on either side of the stable. If only 

 one row of horses exist then the calculation of the size of 

 inlet is made for one horse only, provided each animal has 

 a window to itself. 



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