Iron fences invariably exhibit only the polarity by vertical induction;
so also small buckets, bells, etc. But in the case of a bell about 3 ft.
in diameter at its base, and over two feet deep, tapering to about a
foot in diameter at the top, I found that although the top attracted the
marked end of the needle, the bottom attracted the unmarked end of the
needle only around the northerly half of the circumference, while
the southern portion of this lower rim attracted the marked end in
consequence of lateral induction, as in N. and S. rails.
Thus, upon a comparison of all these facts, it would appear that, if
the magnetism induced by the earth is due to so-called currents of
electricity, those currents must be _underneath_ the rails, and must
move from west to east, under the south to north rails, and from south
to north under the west to east laid rails, as indicated by the arrows
in the diagram.
This accords perfectly with what we should theoretically expect, in our
northern hemisphere, if the electricity in the earth's crust is due to
thermo-electrical currents from east to west, namely, from the more
heated to the less heated portion, on any given latitude, while the
earth revolves from west to east; as well as also from electrical
currents trending from tropical to Arctic regions.
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