769. Magnetism is a constant process of excitation. This process of excitement is the process of imparting and of propagation. Magnetism has not been given, but excited. It breathes life into the iron bar, whereby the latter awakes, and that is magnetism. 770. Every action, which induces differences in a line of iron, renders it therefore magnetic; thus electricity, unequal calefaction and a blow, whereby it is thrown into a state of vibration. An iron bar planted perpendicularly becomes magnetic, because it is then a radius to the earth. From the same reason it becomes magnetic, if placed in the magnetic meridian. e. TERRESTRIAL MAGNETISM. 771. If all metals are in idea magnetic; so must the metallic veins, as products of magnetism, be magnetic lines. Every vein has a north and a south pole. 772. As every vein is a magnetic line or magnetic needle upon a large scale; so must two veins abutting against each other represent likewise a magnetic tension. A mountain of ores is a net of numerous magnets interlacing each other. As one vein is related to the other, so must one metalliferous mountain be related to the other; and thus two mountains of this character stand in magnetic polarity with each other. The whole earth is surrounded by a magnetic net. 773. As every metal, every vein, every rock is in miniature a magnet, so must the earth be a magnet upon a large scale. There is a _Terrestrial magnetism_. 774. This magnetism belongs only to the earth only in so far as it possesses a metallic quality, for magnetism is only the spirit of the metals, not of the other terrestrial bodies, as the earths, Inflammables, and salts. 775. Magnetism is no general character of the earth, still less of the whole solar system, except in so far as the metallic principle lies at the basis of every thing earthy. Magnetism does not operate outwardly over the earth. 776. The determinants of terrestrial magnetism are the _metallic veins_, or the metallic beds in the crust of the earth. 777. Terrestrial magnetism has not been produced or determined by a magnetic nucleus; since a metal in the middle of the earth is a contradiction. All determinations of terrestrial magnetism depend upon the nature, character, distribution, number and direction of the metallic veins or beds. 778. Thus the direction of the magnetic axis of the earth, its mutability, the declination of the magnetic meridian, the inclination or dip of the needle, in short every phenomenon without distinction that concerns magnetism, must be derived from the nature of the metallic veins. Another momentum does not indeed exist for magnetism.