MOISTURE IN THE ATMOSPHERE 11 



wetting his finger at his mouth and holding it high above his 

 head? 



19. Would the man who kept a wet cloth over his gas meter 

 be able to get more gas for his money? 



20. Why is a healthy dog's nose always cold? 



MOISTURE IN THE ATMOSPHERE 



Value of Moisture in the Atmosphere. Water vapor is hidden 

 away in many of the secret recesses of our wonderful air ocean. 

 If moisture could be taken away from us, not only would all green 

 things wither for lack of it, but the sun would shine down upon 

 us with a fierceness beyond conception, for the floating mists, 

 clouds, or other moisture in the air keep these burning rays from us. 

 They act in another way also. Their presence keeps a great quan- 

 tity of the sun's light from us. Acting as a screen, not only do they 

 steal heat from the traveling sunbeams, but they diffuse the sunlight. 



Again, the " night work " of moisture is very important, During 

 the day the earth gathers heat from the sun's rays as they beat 

 downward. When the sun " sets," the stored up heat begins to 

 release itself into space. The vapor in the air prevents this heat 

 from radiating too rapidly. If it were not for this blanket of moisture 

 to check the heat, the suddenness of the chill would be terrible. 



Cloudy nights are warmer than clear nights, for the clouds 

 act as a blanket, sending back to the earth the heat which is radiated. 

 On clear nights the earth loses its heat much more rapidly, for 

 the light veil of vapor in the air does not arrest the warmth from 

 the earth as well as heavy clouds do. 



Relation of Evaporation to our Bodily Comfort. In deserts, 

 where the relative humidity is small, evaporation goes on very rap- 

 idly. Wherever there is a large amount of moisture on surfaces, the 

 relative humidity is great and only a little evaporation can take 

 place. Such conditions may be found in forests of the tropical 

 countries. The same conditions apply to temperate zones in the 

 United States and Europe where there is a small amount of rain- 

 fall in summer time. This lack of evaporation affects our comfort, 

 because some days are humid, close, or muggy. At such times 

 the heat becomes very oppressive. We perspire easily and are 



