STABLES 71 



in the opposite or front wall, and will assist in keeping the stable bright 

 and sweet. The importance of having windows on both sides of a range 

 of stables cannot be overestimated. 



VENTILATION AND AIR SPACE 



It will not be questioned that a supply of pure air is absolutely essential 

 to health, and accordingly the subject of ventilation has always attracted 

 a large amount of attention from sanitary authorities. In theory nothing 

 can be more simple ; it is only necessary to provide openings through which 

 pure air may pass in at one point, and other openings, in a different 

 position, out of which the contaminated air may escape. This is, un- 

 doubtedly, the true principle of ventilation, but in practice it has been 

 found extremely difficult to attain the results which are desired. The pure 

 air is commonly found to enter with sufficient rapidity, and often in 

 sufficient quantity, not only at the point through which it was intended to 

 enter, but also at the opening which was intended for the escape of the 

 contaminated air. The down-draught, as it is called, is the great trouble of 

 the sanitary engineer, and it has not up to the present time been found 

 possible to avoid this and to create an upward current wjth perfect cer- 

 tainty and regularity except by the use of machinery, or the employment 

 of heat to rarefy the air at the intended point of exit, so that the air con- 

 tained in the building may be induced to rise and escape as required. 



Some interesting experiments were performed by Veterinary Major Fred 

 Smith of the Army Veterinary Department, and described by him in his 

 work on Veterinary Hygiene. The object was to ascertain the direction of 

 currents, after entering a building by the means of windows, tubes, shafts, 

 perforated bricks, or holes in various parts of the walls. The first thing 

 which was noticed was the diminution in the rate of motion of a current of 

 air in the act of passing through a shaft or tube, owing to the friction 

 against the sides of the passage. It follows, therefore, that the loss of 

 motion in the air will be considerably less in a wide than in a narrow 

 passage. A further cause of diminution of velocity and interference with 

 escape of air exists in the bends or angles in the passage, and it is impor- 

 tant to remember that in such bends accumulation of dust is inevitable, and 

 that when bends are unavoidable some method must be devised for the 

 purpose of keeping them clean. 



A very common device for ventilating a building is that of the shaft 

 divided into two by a diaphragm running down the centre. By this method 

 it is presumed that one side of the shaft will act as an inlet, and the other 

 side as the outlet; but in practice the operation is by no means always satis- 



