When, as children, you played with toy magnets in the nursery, little did you think that there was a host of tiny electrons amusing you. And yet we electrons are responsible entirely for all magnetic effects, as I shall proceed to explain. CHAPTER VIII A USEFUL DANCE _THE SCRIBE'S NOTE ON CHAPTER EIGHT_ We believe magnetism to be due to electrons revolving around atoms of iron and other magnetic substances, as related by the electron in this chapter. We have seen that the steady motion of electrons along a wire produces a magnetic field around the wire. Therefore if we have electrons revolving round and round the atoms in a piece of iron, there will be a miniature magnetic field around each atom. The electron explains why a piece of iron does not show the magnetic power locked up within it until it is "magnetised." The electron refers to electro-magnets; an electro-magnet is simply a piece of soft iron with a coil of insulated wire wound around it. The iron only shows its magnetic power as long as a current of electricity is kept passing through the surrounding coil of wire, for reasons which the electron explains. CHAPTER VIII A USEFUL DANCE I may tell you quite frankly that I have never taken part in the perpetual dance of which I am about to tell you. I am of a free and roaming disposition, but I have often watched some of my fellow-electrons at this work. Of course, it is pleasant work, as all our duties are, now that man acknowledges our services. We are responsible for the behaviour of the mariner's compass needle. It is we who cause it to point continually in one definite direction. If we ceased to dance around the iron atoms in the compass needle aboard a ship, the man at the helm could not tell in what direction he was going, and sooner or later he would be almost certain to wreck his vessel. For this service alone man ought to be grateful to us, but before I have finished my story, you will find that even this important duty is but a small affair when compared with many of our other tasks. There is one matter I should like to make quite clear to you. Although we electrons are all identical, we have different stations to fill. You have doubtless become familiar with my roving disposition, and you probably think of me as a detachable electron. Then there are our friends who are locked up within the atoms of matter--part and parcel of the atom. And now I am introducing you to those electrons who act as satellites to the atoms, revolving around them at a comparatively great distance, just as the moon revolves around the earth. These are the electrons which give rise to the magnetism in a piece of iron. There are other electrons which perform very rapid revolutions around all classes of atoms, but I shall introduce these friends later on. [Illustration: A TOBACCO-TIN DEFYING GRAVITATION