. Electricity simplified. The practice and theory of electricity ... d for by assuming itto be girdled by electric currents approximately inplanes parallel to the equator, and going from east towest, opposite in direction to those encircling a mag-net whose north pole is pointing north. The ten-dency of the nearer portions of the two sets of circu- TERRESTRIAL MAGNETISM. 89 lar currents, one around the earth, the other aroundthe magnet, to coincide in direction, and to be par-allel, causes the magnet to point north and earth currents may involve the expenditure ofenergy, and probably
. Electricity simplified. The practice and theory of electricity ... d for by assuming itto be girdled by electric currents approximately inplanes parallel to the equator, and going from east towest, opposite in direction to those encircling a mag-net whose north pole is pointing north. The ten-dency of the nearer portions of the two sets of circu- TERRESTRIAL MAGNETISM. 89 lar currents, one around the earth, the other aroundthe magnet, to coincide in direction, and to be par-allel, causes the magnet to point north and earth currents may involve the expenditure ofenergy, and probably do. Poor conductor as the sur-face of the earth may be, its interior may be better;and .in any case the great volume of the earth wouldcompensate for its normally high resistance. As amber was the material with which the firstexperiment in static electricity was performed, andgave its name to the science, so the natural loadstonewas the first magnet experimented with. It wasfound at Magnesia in Asia Minor, and the name magnet is derived from that of the Fig. 21. If we follow out the fact that currents in the samedirection attract each other, the same diagram willshow that the opposite poles of magnets should attracteach other for the same reason. The direction of 90 ELECTRICITY SIMPLIFIED. the theoretical Amperean currents in a magnet beingin opposite directions at the two poles, it is evidentthat when opposite poles are brought face to face theAmperean currents will coincide in direction. To an observer facing the north pole of the earth,the Amperean earth currents would seem to go inthe direction of the hands of a watch. Thence itfollows that, if the earth be considered a giganticmagnet, what we call its north pole would be reallyits negative or south pole. The confusion would beavoided if we call the positive pole of a magnet, thenorth-seeking, instead of north pole, and viceversa. Again, if the earth is a magnet, lines of force shouldemanate from it, running fro
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Keywords: ., bookcentury1800, bookdecade1890, bookidel, booksubjectelectricity
