116 CAUSES AND PREVENTION OF DISEASE. 



close to the floor, so that their use can be regulated according 

 to season and temperature. The upper openings of the shaft 

 being used in hot weather, and the lower openings in cold weather. 

 There should be a number of medium sized or even small 

 windows in this system rather than a few large ones. The same 

 amount of air can be allowed to enter through the small openings 

 without direct draft, and with much better distribution. 



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