VENTILATION 81 



The width of each window is 2 feet 6 inches = 30 inches. 



Therefore 57-6-1-30 = 1-9. Or, in other words, each 

 window or ventilator must be opened 2 inches to admit, at 

 a velocity of 13 miles per hour, 15,000 cubic feet of air per 

 head. 



This calculation, then, shows the size to which the inlet 

 windows should be opened ; but it is obvious, from what 

 has been previously stated, that the outlet windows should 

 be opened the same width, not only that they may act as 

 outlets for an equal bulk of air which is admitted by the 

 inlets, but for the reason that the wind may shift round, 

 and they must then act as inlets. 



In calculating the width which ventilators should be 

 open when both sides of the stable are occupied by horses, 

 it is necessary to remember that the inlet windows must 

 be calculated for supplying two rows of horses, viz., those 

 under the windows, and those on the opposite side of the 

 stable. 



No difficulty should be felt in estimating approximately 

 the velocity of the wind from the table given above. The 

 average velocity of the wind in Great Britain is from six to 

 twelve miles per hour. 



The leading principles to guide us in the natural ventila- 

 tion of stables are : — 



1. The wind is the great ventilating agent, in order that 

 it may act to full advantage window should be opposite to 

 window, and door to door. 



2. The distance between ojoposite doors and windows 

 should not be more than 80 feet. 



3. In order that effective ventilation may occur only two 

 horses should be placed between opposite sources of air, as 

 in Pig. 23 ; the transverse arrangement of horses in stables, 

 where several are placed between opposite sources of air, is 

 bad, see Pig. 24. 



4. Stables with open roof as in Pig. 23 are easily venti- 

 lated, those with living-rooms above as in Pig. 24 can never 

 be effectively ventilated. 



5. In natural ventilation any opening may be an inlet or 



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