66 VETEEINAEY HYGIENE 



and the air passing over it has its temperature raised. The 

 inventors claim the incoming air can be raised from 30 to 

 130° Fahr. The cost of gas in raising the temperature 

 sixty degrees is less than one farthing an hour, and for 

 this sum 18,000 cubic feet of air can be heated. 



Fig. 3. — Section of a stable heated artificially by means of Boyle's gas- 

 bracket. On the ridge may be seen the exhaust ' air-pump ' of the same 

 firm. 



Gas may also be employed for extracting impure air by 

 being placed under suitable tubes for this purpose. One 

 cubic foot of gas will extract 3,000 cubic feet of air, and as 

 an ordinary burner uses five cubic feet per hour 15,000 

 cubic feet per hour may in this way be got rid of. 



Gas is not always available, but we are not limited to 

 this, there are other methods by which stables and cow- 



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