82 FARADAY 



all the way round in this arrangement, and where I have 

 inserted the platinum, which offers some resistance to the 

 passage of the force, you see what an amount of heat is 

 evolved; this is the heat which the zinc would give if 

 burnt in oxygen; but, as it is being burnt in the voltaic 

 battery, it is giving it out at this spot. I will now shorten 

 this wire for the sake of showing you that, the shorter the 

 obstructing wire is, the more and more intense is the heat, 

 until at last our platinum is fused and falls down, breaking 

 off the circuit. 



Here is another instance. I will take a piece of the 

 metal silver, and place it on charcoal connected with one 

 end of the battery, and lower the other charcoal pole on 

 to it. See how brilliantly it burns! (Fie. 49.) Here is a 



FIG. 49 



piece of iron on the charcoal: see what a combustion is 

 going on; and we might go on in this way, burning almost 

 every thing we place between the poles. Now I want to 

 show you that this power is still chemical affinity; that if 

 we call the power which is evolved at this point heat, or 

 electricity, or any other name referring to its source, or 

 the way in which it travels, we still shall find it to be 

 chemical action. Here is a colored liquid which can show 

 by its change of color the effects of chemical action; I 

 will pour part of it into this glass, and you will find that 

 these wires have a very strong action. I am not going 

 to show you any effects of combustion or heat, but I will 

 take these two platinum plates, and fasten one to the one 

 pole and the other to the other end, and place them in this 

 solution, and in a very short time you will see the blue 

 color will be entirely destroyed. See, it is colorless now ! 

 I have merely brought the end of the wires into the solu- 



