Davis's manual of magnetism : including galvanism, magnetism, electro-magnetism, electro-dynamics, magneto-electricity, and thermo-electricity (1854)
Davis, Daniel · Boston : Palmer and Hall · leaf 241
the positionC D. As the bar is raised, the north pole recedesfrom C, as indicated by the dotted lines in the cut.The strongest action is exerted when the bar is inthe ine of the dip, or in this latitude nearly verticallyover the needle. By carrying the bar below theneedle, still preserving the same… … versmg the bar, so as to bring the end D downwards^C immediately becomes the south pole: thus thepolarity may be changed at pleasure, the inducedmagnetism being only temporary. If the bar isbrought very near to the pole of the needle, the in-ductive action of the earth will be overpowered bythat of…
