Page:On the various forces of nature and their relations to each other.djvu/134

130 down. And here is another substance, gutta-percha, in thin strips: it is astonishing how, by rubbing this in your hands, you make it electrical. But our time forbids us to go further into this subject at present. You see clearly there are two kinds of electricities which may be obtained by rubbing shell-lac with flannel, or glass with silk.

Now, there are some curious bodies in nature (of which I have two specimens on the table) which are called magnets or loadstones—ores of iron, of which there is a great deal sent from Sweden. They have the attraction of gravitation, and attraction of cohesion, and certain chemical attraction; but they also have a great attractive power, for this little key is held up by this stone. Now, that is not chemical attraction,—it is not the attraction of chemical affinity, or of aggregation of particles, or of cohesion, or of electricity (for it will not attract this ball if I bring it near it); but it is a separate and dual attraction—and, what is more, one which is not readily removed from the substance, for it has existed in it for ages and ages in the bowels of the earth. Now, we