24 SCIENCE OF HOME AND COMMUNITY 



it the result will be only approximate as the liquid will not 

 rise quite to the body temperature) ; the proper living tempera- 

 ture of the schoolroom in winter. 



Into how many degrees is the space between the freezing 

 and boiling points marked on each scale ? What advantage do 

 you think the Centigrade scale has over the Fahrenheit? Do 

 you see any disadvantage ? 



2. The thermometers found in houses are often incorrect. 

 Bring yours from home so that you can test it. Place the end 

 of the thermometer in a tumbler and fill the tumbler with cracked 

 ice. Allow it to stand till the water from the melted ice covers 

 the bulb, and the liquid in the thermometer falls no lower. 

 Record the reading. ' The correct reading is 32. Hang up your 

 thermometer beside a tested chemical one furnished by the 

 instructor. Note the difference. The average of this difference 

 and of the error at the freezing point may be taken as the cor- 

 rection to be made in using your thermometer. 



Humidity. If the air is too moist, evaporation in the skin 

 takes place too slowly and the body becomes too warm. If 

 the air contains too little moisture, evaporation takes place 

 too rapidly. The lack of moisture in the heated air in our 

 homes in winter has an injurious effect on the nose and throat. 

 As this dry air passes over the membrane lining the nose 

 and throat, it causes an excessive amount of evaporation 

 from these surfaces, which become dry, parched, and 

 irritated. As a result they afford a lodging place for germs, 

 and we become more easily subject to colds and other 

 diseases of the throat and nose. Furthermore, these mem- 

 branes are not able to do so well their ordinary work of 

 filtering the air of impurities. 



This extreme dryness found indoors during the winter 

 produces an artificial and unnatural condition because it 

 is such a contrast to the natural condition found outdoors. 



The amount of moisture in the air is measured in terms 

 of per cent. When the air is saturated (that is, holds all it 

 can, as just before a rain) , the humidity of the air is said to 



