The Encyclopedia britannica; a dictionary of arts, sciences, and general literatureWith new maps, and original American articles by eminent writersWith American revisions and additions, bringing each volume up to date . 236 MAGNETISM ijowever many poles of the same kind iimre may be, trueand false, the whole number must be odd. This of coursedisposes of the notion formerly held by some physiciststhat the earth actually had tioo north poles. As alraadj-Tadicated, Gauss conclsded from his reduction of themagnetic observations at his disposal that, apart frompurely local disturbances, the earth h
The Encyclopedia britannica; a dictionary of arts, sciences, and general literatureWith new maps, and original American articles by eminent writersWith American revisions and additions, bringing each volume up to date . 236 MAGNETISM ijowever many poles of the same kind iimre may be, trueand false, the whole number must be odd. This of coursedisposes of the notion formerly held by some physiciststhat the earth actually had tioo north poles. As alraadj-Tadicated, Gauss conclsded from his reduction of themagnetic observations at his disposal that, apart frompurely local disturbances, the earth has, as a matter of fact,Cnly one north and one south pole. The effect of a deposit of magnetic ore, or other the kind, might of course produce a disturbance, withinf a limited area, of the equipotential lines. It may assist* the practical magnetist to indicate the nature of thisdisturbance in a particular case. Let us suppose that amagnet is placed some distance underground, vertical, withits north pole uppermost. Then, if its moment besufficiently great, the equipotential lines will be as in The upper side of the figure is supposed to bemagnetic north, and it is supposed that the undisturbed. Fig. 27. parallels .would be straight lines running magnetic eastand west, which is sufficiently near the truth in mostcases. It should be observed that fig. 27 is in reality atransformation of figure 26, one of tHe poles being projectedto infinity. The reader should notice that the double pointF, due south of the point a vertically over the disturbingmagnet, is a point of equilibrium at which the horizontalcomponents Qf. the forces of the earth and the magnetdestroy each other; it will be a false pole, south or northaccording as the magnet or the earth prevails. Experimental Foundation foe the Law of theInverse Square. Diffical- From what has already been laid down, it will be ties of seen that the determination of the elementary law of *^^^ magnetic action is a very co
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