CONSERVING HEAT 



91 



Jrc 



preventing its escape. We build thick walls to our houses 

 in order that the heat from our stoves and furnaces may not 

 escape. We put on clothing in order that the heat of the 

 body may be retained. Ovens of cookstoves are surrounded 

 by air spaces and non-conducting materials so that the heat 

 will not be lost. In fact there are scores of arrangements 

 in every home for conserving heat. 



Dark surfaces absorb heat more readily than light surfaces, 

 and thus increase more rapidly in temperature. Light 

 surfaces reflect heat, and absorb 

 it very slowly. This is why we 

 wear dark clothing in winter 

 and light-colored clothing in 

 summer. Dark surfaces not 

 only absorb heat more readily 

 but they radiate it more rapidly. 

 Light surfaces are slow to heat 

 up, and when they are heated 

 up they are just as slow to 

 radiate their heat. There is 

 the same difference in these 

 respects between smooth surfaces and rough surfaces as 

 between light and dark surfaces. 



The fireless cooker (Figure 46) is a device to save heat in 

 cooking. It consists of two boxes, one within the other and 

 separated from each other on all sides by a space of several 

 inches. This space is filled with sawdust, ground cork, as- 

 bestos, or any other substance that is a poor conductor of 

 heat. A tightly fitting cover is provided, containing similar 

 non-conducting material. The food to be cooked is heated 

 on the stove in a covered vessel, and this is placed within 

 the cooker. Since the heat can escape only very slowly, the 



REVOLVING DOORS 

 An arrangement to conserve heat. 



