which we have not as yet come to, but which stands next on our list—Chemical Affinity. And thus you see we can have a violet vapour or an orange vapour, and different other kinds of vapour, but they are always perfectly transparent, or else they would cease to be vapours.
I am now going to lead you a step beyond this consideration of the attraction of the particles for each other. You see we have come to understand that, if we take water as an illustration, whether it be ice, or water, or steam, it is always to be considered by us as water. Well, now prepare your minds to go a little deeper into the subject. We have means of searching into the constitution of water beyond any that are afforded us by the action of heat, and among these one of the most important is that force which we call voltaic electricity, which we used at our last meeting for the purpose of obtaining light, and which we carried about the room by means of these wires. This force is produced by the battery behind me, to which however I will not now refer more particularly; before we have done we shall know more about this battery, but it must grow up in our knowledge as we proceed. Now here (fig. 24) is a
