Page:On the various forces of nature and their relations to each other.djvu/161

Rh when I discharged the large electrical machine, when you saw one single bright flash; it is the same thing, only continued, because here we have a more effective arrangement. Instead of having a machine which we are obliged to turn for a long time together, we have here a chemical power which sends forth the spark; and it is wonderful and beautiful to see how this spark is carried about through these wires. I want you to perceive, if possible, that this very spark and the heat it produces (for there is heat) is neither more nor less than the chemical force of the zinc—its very force carried along wires and conveyed to this place. I am about to take a portion of the zinc and burn it in oxygen gas, for the sake of shewing you the kind of light produced by the actual combustion in oxygen gas of some of this metal. [A tassel of zinc-foil was ignited at a spirit-lamp, and introduced into a jar of oxygen, when it burnt with a brilliant light.] That shews you what the affinity is when we come to consider it in its energy and power. And the zinc is being burned in the battery behind me at a much more rapid rate than you see in