We may remark that other bodies besides iron and steel are capable of magnetization; nickel and cobalt have the like property. Magnetism, properly so called, treats of certain bodies known as MAGNETS, describes the properties they possess, and the influence of magnetic force upon other substances. Electricity and magnetism are always associated, but practically the force is the same, electricity being the current or motive power, so to speak; and it is to Faraday that the world is indebted for the discovery of magneto-electricity. Epinus’ theory of magnetism was that all bodies possessed a substance he termed magnetic fluid, the particles of which repelled each other. But while supposed to repel each other, they attracted particles in other bodies. Thus they attracted iron. Coulomb asserted that there were two fluids—a north and south fluid. Ampère’s theory was that magnetic bodies are made up of molecules, round which currents are always circulating in all directions when non-magnetized, but when magnetized the currents all flow in the same direction. The space through which a magnet diffuses its influence was called by Faraday the _Magnetic Field_. The lines of _magnetic force_ will be understood from the accompanying illustration (fig. 263). If we cover a magnet with a paper and scatter iron filings over it, we shall see the manner in which the filings arrange themselves. They radiate in curves from the poles of the magnet, and are dependent upon its form. If it be a straight bar magnet, evenly magnetized, they will turn inward in oval curves. [Illustration: Fig. 263.—Lines of magnetic force.] [Illustration: Fig. 264.—Magnetization.] The manner of magnetization has already been mentioned, but here we will give further illustrations of the method of _magnetization_. Four magnets are used, two being placed with their opposite poles apart, and upon them is placed the bar of which a magnet is to be made. Two other magnets separated by a piece of wood are then brought near, and subsequently drawn from the centre to the ends of the bar. This is the _separated touch_ system; the _double touch_ of Mitchell is completed by moving the upper two magnets from end to end backwards and forwards, and finally lifting them away from the centre. A magnet, then, is a bar of steel endowed with certain properties, such as attracting iron, etc.; and electro-magnetism is the term applied to the production of magnetism by means of electricity, the medium being the electro-magnet. To understand the science it will be necessary to mention Ampère’s theory of magnetism.