CHAPTER XXVII 

 METHODS OF HEATING 



382. Starting a Fire. In countries where the winters are 

 cold it is necessary to devote a great deal of time and labor 

 to the heating of dwellings. Heat is usually obtained by the 

 burning of wood, coal, etc. Such substances are called fuel. 

 The harder the fuel, the more difficult it is to kindle. Coal is 

 harder to light than wood because of its density, which in- 

 creases the difficulty of raising it to the temperature which is 

 necessary for burning. If the heat of another fuel, such as kin- 

 dling wood, be applied to the coal in sufficient quantity and 

 long enough to ignite it, it will then produce a fire much more 

 powerful and much more durable than will the lighter fuel. 

 Lighter fuel kindles easily, but the mixture of air in its pores 

 causes it to burn out rapidly. Hence the heat it produces is 

 but temporary, though often very strong. The usual method 

 of getting rid of the smoke from a fireplace is through a 

 chimney. 



383. Methods of Heating. Modern buildings and houses 

 are heated by stoves, steam, hot water, or furnaces. The 

 choice of any particular method will depend upon special 

 conditions arid requirements. Heat is given from a stove by 

 radiation (Fig. 172) ; that is, the stove becomes hot, due to the 

 burning of coal, and the metallic parts radiate the heat. A 

 stove is not an economical means of heating, because much 

 of .the hot air goes up the chimney and is wasted. Moreover, 



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