falling the whole of the mass is acted upon by the force of gravitation. I have here (fig. 40) a steel bar, and I am going to make it a magnet, by rubbing it on the large magnet (fig. 39). I have now made the two ends magnetic in opposite ways. I do not at present know one from the other, but we can soon find out. You see when I bring it near our magnetic needle (fig. 38) one end repels and the other attracts; and the middle will neither attract nor repel—it cannot, because it is half way between the two ends. But now, if I break out that piece (n. s.) and then examine it—see how strongly one end (n) pulls at this end (s fig. 38) and how it repels the other end (n). And so it can be shown that every part of the magnet contains this power of attraction and repulsion, but that the power is only 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
