source, or the way in which it travels, we still shall find it to be chemical action.
Fig. 49.
Here is a 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 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 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 chemical action. There is also another curious
