RELATION OF AIR TO THE HOUSE WE LIVE IN. 213 



and crevices is of greater influence than large communications with 

 the outer air at a small difierence of temperature. 



The roaring fire and tbe draught of the stove produced only an 

 increase of 700 cubic feet one-third only of the necessary ventilation 

 per head. I have examined a number of stoves opening into the room 

 for the quantity of air which they abstract while the fire burns. The 

 anemometer showed that it was never more than 3,105 cubic feet. 

 Large wards in hospitals, schools, etc., heated by one open fireplace 

 or stove, are sometimes wrongly believed to be well ventilated, because 

 one perceives the air rushing into the same. But the main point is to 

 know the quantity of required air and the quantity of outgoing air. 



The free wall of a room of mine has been examined for its venti- 

 lating power. The room contained 2,650 cubic feet, and at 9.5 Fahr. 

 difference of temperature between outside and inside, the spontaneous 

 ventilation through each square yard amounted to about seven cubic 

 feet, or forty-three gallons per hour. 



Marker and Schultze, in their researches on the siDontaneous ven- 

 tilation of stables, have found for one square yard of a free wall, at 

 9.5" Fahr. difference of tempei-ature, that the spontaneous ventilation 

 amounted per hour 



With walls of sandstone 

 " " quarried limestone 



" " brick 



" " tufaceous limestone " 10.1 



" " mud " 14.4 " " 



Domestic animals, according to Marker, require a proportionately 

 smaller change of the air than man. Stable-air may contain up to 

 three per mil. carbonic acid. While man's ventilation requires 2,100 

 cubic feet per hour, 1,050 are sufiicient for full-grown cattle, although 

 their bodies and consumption of air are so much larger. The ven- 

 tilation of stables depends chiefly on the size and porosity of their 

 free walls. It has been found that the 1,050 cubic feet mentioned 

 above were furnished by 



21.16 square feet of a free wall of sandstone. 



15.33 " " *' " quarried limestone. 



12.6 " " " " brick. 



9 Y '< " " " tufaceous limestone. 



7 " " " mud. 



A stable built up of mud can therefore shelter many more animals 

 than one built of sandstone, etc. " As the strength of the natural 

 ventilation of a stable does not depend on the cubic space of the sta- 

 ble, but on the extent of its ventilating walls, it follows that in a 

 small stable a proportionately greater ventilation takes place than in 

 a greater one, because for each animal there is more ventilating sur- 

 face with equal cubic space." 



