84 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 60 



atmosphere. Air saturated at i8° F. holds only i grain of water 

 vapor per cubic foot, while air saturated at yo° F. holds 8 grains. 

 Thus if in winter the outside air is saturated at i8° F. and this air 

 is heated up and driven into a room which is kept at 70 ° F., the air 

 will hold the same absolute amount of moisture, but the relative 

 humidity will only be 12.5 per cent against 100 per cent outside. 

 Suppose the air outside is only half saturated; then the relative 

 humidity inside will be only 6.25 per cent. This is an unusual con- 

 dition of affairs in the moist and temperate climate of Britain, but 

 a common occurrence during the rigorous winters of North America, 

 and there the schools and dwellings are heated with this desert air. 



In Britain if the air were saturated at 32° F. and raised to 6o° F., 

 the relative humidity would be only 34.9 per cent ; and if the relative 

 humidity of the outside air at 32 F. were 70 per cent, that inside 

 would be only 24.5 per cent. 



The Chicago Ventilating Commission say " it is probably safe to 

 say that not more than 2 per cent of the public schools in the United 

 States have any humidifying apparatus. The air, having been 

 heated to about ioo° F. and cooled to about 70 F. before it reaches 

 the children, is superdried and seeks to obtain its proper balance of 

 moisture from the school structure and the bodies of the children ; 

 hence shrunken furniture, dust, dry throats, parched lips, and a 

 rapid rate of skin evaporation, rendering it necessary to maintain a 

 high temperature for comfort." " In the high-grade installations the 

 temperature is held at 72 ° F. One thousand eight hundred cubic 

 feet of air per pupil are pumped into the room. In the older instal- 

 lation we frequently find the temperature well over 75 F." (Dr. 

 Evans, Chicago). The citizens of Chicago are paying for a system 

 which is most expensive, and no less pernicious and absurd. The 

 dry, hot " desert " air makes the children stupid, spoils their com- 

 plexions, swells up the respiratory tract and lowers the immunity. 



In contrast with American women, the fresh complexion of 

 English women, and still more of Irish women, seems to be corre- 

 lated with a moist atmosphere and less indoor life. 



The Chicago Commission say that in cold weather it is not possible 

 to ventilate unoccupied rooms in that climate, except with air pre- 

 viously warmed, but that heating and ventilating are separate ques- 

 tions and must always be so considered. It is economic not only to 

 health but to fuel to maintain a sufficient relative humidity and avoid 

 " desert " air. We agree that the dry-bull) temperature for the 

 schools ought not to exceed 55 ° to 58 ° F. and the relative humidity 

 ought to be 60 per cent. This will cause the window-panes to frost 



