no GENERAL SCIENCE 



It is not necessary to go to any great expense to enjoy 

 the use and advantages of a fireless cooker. All you 

 need to do is to get two store boxes of proper size and 

 some packing material to be placed between the two as 

 described above. Any family desiring the use of a fire- 

 less cooker can easily make one and enjoy the 

 I I increased flavor of their food cooked in such 

 '( i\ a manner. 



The "thermos bottle" is a modified form of 

 the fireless cooker. It is made of two glass 

 bottles, one sealed inside of the other at the 

 neck in such a way that air cannot pass in or 

 out between the two bottles. Just before seal- 

 ing the inside bottle to the outside one, the air 

 CROSS between the bottles is pumped out, thus leav- 

 SECTION OF ing nothing between the two bottles which can 

 THERMOS transmit heat from the inside bottle to the out- 

 side one by convection or conduction. The out- 



riafiifthe In- side bottle is lmed on tne inside by a bright, 

 side bottle, reflecting metal which prevents the escape of 

 side bottle, any heat from the inside bottle by radiation. 



QUESTIONS AND EXERCISES 



1. Why do gardeners make hotbeds with glass tops? 



2. Why does an iron handle of a cooking utensil get so much 

 hotter than a wooden handle? 



3. What advantage is it to birds to have their feathers standing 

 out straight from their bodies in winter instead of lying down smooth 

 as in summer? 



4. Why do animals living in cold regions have a heavy coat of 

 fur? 



5. How does clothing keep you warm in winter? In summer? 



6. Why are cold storage rooms built with a double wall and the 

 space between filled with sawdust or other material? 



7. Why will ice packed in sawdust not melt? 



