APPLICATIONS OF EVAPORATION, CONDENSATION 35 



'References : 



1. 1503 : 397-398. Regulation of Body Temperature. 



2. 1803 : 100-101. Cooling Effects of Evaporation Explained. 



3. 1803 : 210. Intense Cold by Evaporation. 



a. 1507 : 241-244. Perspiration as a Heat Regulator. 



b. 1801 : 281. Cold by Evaporation. 



c. 1804 : 289. Heat Consumed in Evaporation. 



d. ^805 : 340. Cold by Vaporization. 



e. $06 : 365-366. Cooling by Evaporation. 



/. 18)7 : 193. Disappearance of Heat during Vaporiza- 



tion. 



25. APPLICATIONS OF EVAPORATION AND CONDENSATION 



As fast as man really understands the phenomena of nature, 

 he makes use of them for his own comfort, or for profit. Ac- 

 cordingly, life means most to the one who knows most, and 

 can use his knowledge in his daily life. Cooling by evapora- 

 tion, and the reverse, that is, warming by condensation, are 

 but two more examples of the application of knowledge to 

 practical ends. 



The saying that it is a poor rule which does not work both 

 ways applies more strictly to science than to anything else. 

 In fact, there are but few physical or chemical changes of form 

 or energy which are not reversible. Evaporation requires 

 heat ; that is, heat is absorbed by the material which is evap- 

 orating. When this vapor is condensed, exactly the same 

 amount of heat is given out. There is no loss in nature. 



If water is placed in a porous earthen jar, the water which 

 seeps through evaporates into the air and cools the remainder. 

 The drier the air, and the more air that is brought into con- 

 tact with the surfac.e of the water, the lower will become the 

 temperature. 



