156 NATURE STUDY BY GRADES 



stove, and may be used before the class for a lesson. The 

 oil is the fuel, supplied through the wick and regulated by 

 the raising or lowering of the wick. The chimney creates a 

 draft, supplying air for combustion, and conducting the gases 

 that are the product of combustion. As no ashes are made, 

 no ash pan is needed. For legs, it rests upon a stand. 



Let the pupils themselves discover all these resemblances, 

 and they will better understand the principles of combus- 

 tion. 



LESSON XXX 



FIRE MAKING 



How do we build a fire in a common stove ? Why do we 

 first put in paper or shavings? Why do kindlings come 

 next? What common fuel takes longest to start? What 

 things take fire easily and quickly? What accidents often 

 occur because of this ? Is it safe to pour coal oil on a slow- 

 burning fire to hasten it? Why not? Some substances 

 ignite with very little heat, while others require a greater 

 degree. 



Experiment. On a piece of tin, place a small piece of 

 phosphorus, of sulphur, of wood, and of coal. Hold the pieces 

 over the flame of an alcohol lamp or bunsen burner, keeping 

 the tin moving so as to equalize the heat under each of the 

 substances. Notice the order in which they ignite. A very 

 little heat starts the phosphorus; the sulphur is next, then 

 the wood, and the chances are that the coal will refuse to 

 burn altogether in this experiment. The degree of tempera- 

 ture at which substances begin to burn is called the kindling 

 point, or flash point. 



