94 CHEMICAL AFFINITY. 



are just like this unlighted candle. It stands 

 here quietly on the table, waiting until we 

 want to light it. But it is not so in this other 

 case: here is a substance, gaseous like the 

 oxygen, and if I put these particles of metal 

 into it the two combine at once. The copper 

 and the chlorine unite by their power of chemi- 

 cal affinity, and produce a body entirely unlike 

 either of the substances used. And in this 

 other case, it is not that there is any deficiency 

 of affinity between the carbon and oxygen, for 

 the moment I choose to put them in a condi- 

 tion to exert their affinity, you will see the 

 difference. [The piece of charcoal was ignited, 

 and introduced into the jar of oxygen, when the 

 combustion proceeded with vivid scintillations.] 

 Now this chemical action is set going exactly 

 as it would be if I had lighted the candle, or 

 as it is when the servant puts coals on and 

 lights the fire : the substances wait until we do 

 something which is able to start the action. 

 Can anything be more beautiful than this com- 

 bustion of charcoal in oxygen ? You must 

 understand that each of these little sparks is a 

 portion of the charcoal, or the bark of the 

 charcoal, thrown off white hot into the oxygen, 



