8 GENERAL SCIENCE 



Canton flannel, or duck. Of these materials duck is by far the 

 best. A number of flannel wicks are sewed to the covering material 

 and the other ends of the wicks allowed to rest in a pan of water 

 on the top of the frame. Shelves are built into the frame for 

 holding food supplies. The water soaks into the covering through 

 the wicks from the pan. As the water evaporates, large quantities 

 of heat are removed, keeping the temperature inside the refrig- 

 erator sometimes as low as 50 F. 



Relation of Evaporation to Life. So powerfully cooling is 

 perspiration that this process is Nature's first relief in the pro- 

 tection of the body from high temperature. As the surrounding 

 temperature rises, the amount of perspiration increases, and the 

 body is able to maintain, for a time, its normal standard of health 

 at an incredibly high degree of heat. Strong, perfectly healthy men 

 have been able to remain for some time in rooms whose temperature 

 was as high as 48 degrees above the boiling point of water (212 F.), 

 without any marked rise of bodily temperature. Nor was there 

 any severe discomfort, the temperature of the body being kept 

 down solely by the evaporation of perspiration from the skin. 

 But it must be remembered that, to make this means of cooling 

 possible, it is absolutely essential that the air be dry, and capable 

 of taking up moisture. 



The body generates large quantities of heat during the process 

 of changing food into substances that it can use. Much of this 

 heat must be removed. Moisture comes out of our pores and 

 evaporates from the body. If the moisture did not evaporate 

 there would be no cooling process. If we are very hot, we fan 

 ourselves, because the air around our faces is so full of moisture 

 that it cannot absorb the perspiration. The fan, like the wind, 

 causes drier air to come in contact with our faces and absorbs the 

 drops of perspiration. 



If anything prevents the evaporation of moisture from the 

 body, it stores up large quantities of heat and the temperature 

 rises. If a person does not get relief before the temperature reaches 

 106 or above, death will soon follow. The doctor tries to cool 

 the body by evaporation. If he is not able to get perspiration 

 started, he gives the patient an ice bath. This, of course, removes 



