Page:On the various forces of nature and their relations to each other.djvu/140

136 rendered evident at the end of the mass. You will understand all this in a little while; but what you have now to consider is, that every part of this steel is in itself a magnet. Here is a little fragment which I have broken out of the very centre of the bar, and you will still see that one end is attractive and the other is repulsive. Now, is not this power a most wonderful thing? and very strange the means of taking it from one substance and bringing it to other matters? I cannot make a piece of iron or anything else heavier or lighter than it is. Its cohesive power it must and does have; but, as you have seen by these experiments, we can add or subtract this power of magnetism, and almost do as we like with it.

And now we will return for a short time to the subject treated of at the commencement of this lecture. You see here (fig. 41) a large machine, arranged for the purpose of rubbing glass with silk, and for obtaining the power called electricity; and the moment the handle of the machine is turned, a certain amount of electricity is evolved, as you will see by the rise of the little straw indicator (at A). Now, I