12 GENERAL SCIENCE 



very uncomfortable because little evaporation can take place from 

 the surface of the body when the air is humid. 



On clear, dry days we feel more comfortable because evaporation 

 from the skin removes the perspiration, the percentage of relative 

 humidity being so low that the air can rapidly evaporate great 

 quantities of water vapor. It is because of this that the tem- 

 perature of 90 to 100 or more in Arizona is not accompanied by 

 such uncomfortable conditions as we experience under equal tem- 

 peratures in the Mississippi Valley or near the Atlantic Coast 

 where the relative humidity is greater. 



Humidity. To most of us " humidity " is a very indefinite 

 term. We know that when the humidity is high there is much 

 moisture in the air; when it is low there is little moisture in the 

 air, but the significance and importance of all this is very hazy 

 in our minds. Few persons take note of "humidity" at all, par- 

 ticularly as an element of conditions which affect their health. 

 They realize that " muggy weather," especially in summer, is de- 

 pressing and uncomfortable, but they do not know why " humidity " 

 so affects them. Yet humidity is of the utmost importance in 

 the consideration of healthful temperatures for the home and 

 elsewhere. The lack of humidity, or moisture, causes much dis- 

 comfort, ill health, catarrh, colds, and other diseases of the mucous 

 membrane. If we had the proper percentage of humidity in our 

 homes in winter, we should not only be more healthy and com- 

 fortable, but we should also save from 12J% to 25% of our total 

 cost of heating. 



Health authorities state that in the average home, heated by 

 steam or hot water to a temperature of 72 F., the relative humidity 

 averages but 28%, while with hot air furnaces it is as low as 24%. 

 In the great desert wastes the humidity averages 30%. Now, if 

 a person passes from this dry " indoor climate " into the outdoor 

 air, the percentage of humidity in which may be 70% or more, 

 the violent change seriously affects the air passages and mucous 

 membrane. This causes bronchitis, pneumonia, and kiildred ills. 

 The importance of determining and regulating the humidity of 

 the home, school, office, factory, or wherever people congregate 



