THE EEASON WHY. 41 



Yet man is born to trouble, as the sparks fly upward. I would seek unto God, 

 and unto God would I commit my cause." JOB y. 



82. What is fire? 



It is a violent chemical action attending the combustion of tha 

 ingredients of fuel with the oxygen of the air. 



83. What are the properties of fire ? 



It imparts* heat, which has the effect of expanding both 

 fluids and solids. 



It cannot exist without the presence of combustible materials. 

 It has a tendency to diffuse itself in every direction. 

 It cannot exist without oxygen or atmospheric air. 



84. What elements take part in the maintenance of a fire ? 

 Hydrogen, carbon, and oxygen. Hydrogen and carbon exist in 



the fuel, and oxygen is supplied by the air. 



85. How does the combustion of a fire begin ? 



A match made of phosphorous and sulphur (highly inflammable 

 substances) is drawn over a piece of sand-paper the friction of the 

 match induces the presence of caloric, which developes heat, and 

 ignites the match, the burning of which is sustained by the oxygen 

 of the air. The flame is then applied to paper or wood, and 

 the heat of the flame is sufficient to drive out hydrogen gas, which 

 unites with the oxygen of the air, and burns, imparting greater 

 heat to the carbon of the coals, which assumes the form of carbonic 

 acid gas by union with oxygen, and in a little while all the 

 conditions of combustion are established. 



86. What are the properties of heat ? 

 It may exist without fire or light. 



It is not sensible to vision. 



It makes an impression upon our feelings. 



It acts powerfully upon all bodies. 



It has KO weight. 



It attends, or is connected with, all the operations of nature. 



It radiates from all bodies in straight lines, and in all directions. 



It strikes most powerfully in direct lines. 



Its rays may be collected into a focus, just as the rays of the sun. 



It may be reflected from a polished surface. 



It is more easily conducted by some substances than by others. 



