Page:On the various forces of nature and their relations to each other.djvu/165

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 (fig. 49). Here is a piece of iron on the charcoal—see what a combustion is going on; and we might go on in this way, burning almost everything we place between the poles. Now, I want to shew 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 coloured liquid which can Fig. 49.shew 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