8 



SCIENCE OF HOME AND COMMUNITY 



The explanation of the circulation of the water is similar 

 to that of the circulation of the air in the hot-air system. 

 When water is heated, it expands and becomes lighter and 

 is pushed up by the cold water, which descends to the furnace 

 where it is reheated, thus keeping a constant circulation of 



water through the pipes. 

 This is called the direct 

 method of heating. 



In another method of 

 heating, the coils contain- 

 ing the hot water are 

 placed in the basement, 

 and fresh air from outside 

 is drawn in and heated and 

 then distributed to the 

 various rooms by means 

 of pipes and registers, as 

 in the hot-air system. This 

 is called the indirect method 

 of heating. (See figure 5.) 

 This system has an ad- 

 vantage over the direct 

 FIG. 2. - Hot-water system. method in that it provides 



better ventilation. 



In still another system the radiators are placed in each 

 room as in the direct method, and an opening from outside 

 near the radiators brings in fresh air, which is heated by 

 passing over the radiators. This is called the direct-indirect 

 method. (See figure 6.) 



DEMONSTRATION 2 



Purpose. To study the principles applied in hot-water heating. 



Apparatus. Flask, stopper and tube used in previous ex- 

 periment, two flasks with two-hole rubber stoppers, two pieces 

 of glass tubing about ten inches long. 



