Page:On the various forces of nature and their relations to each other.djvu/130

126 each other strongly.] You see, therefore, what a difference there is between these two attractions,—they are actually two kinds of attraction concerned in this case, quite different to anything we have met with before; but the force is the same. We have here, then, a double attraction—a dual attraction or force—one attracting, and the other repelling.

Again, to shew you another experiment which will help to make this clear to you. Suppose I set up this rough indicator again [the excited shell-lac suspended in the stirrup]—it is rough, but delicate enough for my purpose; and suppose I take this other piece of shell-lac, and take away the power, which I can do by drawing it gently through the hand; and suppose I take a piece of flannel (fig. 34), which I have shaped into a cap for it and made dry. I will put this shell-lac into the flannel, and here comes out a very beautiful result. I will rub this shell-lac and the flannel together (which I can do by twisting the shell-lac round), and leave them in contact; and then, if I ask, by bringing them nearer our indicator, what is the attractive force?—it is nothing! But if I take them apart,