CHAPTER XXVII 

 COMBUSTION 



If you have ever been the keeper of a furnace fire, you 

 know that "firing" is not so easy as it seems. There is 

 a good deal more to it than simply throwing in the coal and 

 taking out the ashes. The fireman of a locomotive or of 

 a steam-power plant, if he is efficient, must understand 

 how to fire so as to secure the maximum of heat with the 

 minimum consumption of fuel. This is a rather compli- 

 cated matter and requires a thorough understanding of the 

 laws of combustion. 



There are various kinds of combustion. Burning is one 

 kind. Rusting is another. The combustion of food 

 within our bodies is yet another. Evidently, if these 

 phenomena are examples of it, it must be a process which 

 is important to understand. 



What Combustion Is. Combustion is the chemical 

 uniting of a combustible substance with oxygen. It names 

 a process which you have already considered under the 

 name of oxidation. Oxidation names this process from 

 the standpoint of oxygen; combustion names it rather from 

 the standpoint of the substance which is oxidized. 



That combustion is so common a process is due to the 



commonness of what we may call ' ' oxygen-hunger." Many 



familiar substances show a sort of eagerness to change by 



uniting with oxygen whenever they have a chance. Since 



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