piece of copper or of silver, and it would have no action of its own on this solution; but the moment the zinc was introduced and touched the other metal, then the action would take place, and it would become covered with copper. Now, is not this most wonderful and beautiful to see? We still have the identical chemical force of the particles of zinc acting, and yet in some strange manner we have power to make that chemical force, or something it produces, travel from one place to another—for we do make the chemical force travel from the zinc to the platinum by this very curious experiment of using the two metals in the same fluid in contact with each other.
Let us now examine these phenomena a little more closely. Here is a drawing (fig. 45) in which I have represented a vessel containing the acid liquid, and the slips of zinc and platinum or copper, and I have shewn them touching each other outside by means of a wire coming from each of them (for it matters not whether they touch in the fluid or outside—by pieces of metal attached—they still by that communication between them have this power transferred from
