Page:On the various forces of nature and their relations to each other.djvu/171

Rh if I break contact again; so you see we have this wire evidently affecting the magnetic needle under these circumstances. Let me shew you that a little more strongly. I have here a quantity of wire, which has been wound into a spiral; and this will affect the magnetic needle in a very curious manner, because, owing to its shape, it will act very like a real magnet. The copper spiral has no power over that magnetic needle at present; but if I cause the electric current to circulate through it, by bringing the two ends of the battery in contact with the ends of the wire which forms the spiral, what will happen? Why, one end of the needle is most powerfully drawn to it; and if I take the other end of the needle, it is repelled: so you see I have produced exactly the same phenomena as I had with the bar magnet,—one end attracting, and the other repelling. Is not this, then, curious, to see that we can construct a magnet of copper? Furthermore, if I take an iron bar, and put it inside the coil, so long as there is no electric current circulating round, it has no attraction,—as you will observe if I bring a little iron filings or nails near the iron. But now, if