144 CORRELATION OF THE PHYSICAL FORCES. 



source, or the way in which it travels, we still 

 shall find it to be chemical action. Here is a 



Fig. 49. 



coloured liquid which can show by its change 

 of colour 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 combus- 

 tion 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 colour will be entirely destroyed. See, 

 it is colourless now! I have merely brought 

 the end of the wires into the solution of indigo, 

 and the power of electricity has come through 

 these wires and made itself evident by its che- 

 mical action. There is also another curious 



