that jar, because the zinc is there dissolving and burning, and produces here this great electric light. That very same power, which in that jar you saw evolved from the actual combustion of the zinc in oxygen, is carried along these wires and made evident here; and you may, if you please, consider that the zinc is burning in those cells, and that this is the light of that burning [bringing the two poles in contact, and shewing the electric light]; and we might so arrange our apparatus as to shew that the amounts of power evolved in either case are identical. Having thus obtained power over the chemical force, how wonderfully we are able to convey it from place to place! When we use gunpowder for explosive purposes, we can send into the mind chemical affinity by means of this electricity; not having provided fire beforehand, we can send it in at the moment we require it. Now, here (fig. 47) is a vessel containing two charcoal points, and I bring it forward as an illustration of the wonderful power of conveying this force from place to place. I have merely to connect these by means of wires to the opposite ends of the
