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order, and to supply what is needed to render the explana-
tion complete. Do not quit the subject until you thor-
oughly understand it; and if you are able to look with
your mind’s eye at the play of forces around a magnet, and
see distinctly the operation of those forces in the produc-
tion of the magnetic curves, the time which we have spent
together has not been spent in vain.

In this therough manner we must master our materials,
reason upon them, and, by determined study, attain to clear-
ness of conception. Facts thus dealt with exercise an
expansive force upon the boundaries of thought; they
widen the mind to generalization. We soon recognize a
brotherhood between the larger phenomena of Nature and
the minute effects which we have observed in our private
chambers. Why, We inquire, does the magnetic needle set
north and south? Evidently it is compelled to do so by
the earth; the great globe which we inherit is itself a
magnet. Let us learn a little more about it. By means of
a bit of wax or otherwise attach your silk fibre to yOur
magnetic needle by a single point at its middle, the needle
will thus be uninterfered with by the paper loop, and will
enjoy to some extent a power of dipping its point or its
eye below the horizon. Lay your magnet on a table, and
hold the needle over the equator of the magnet. The
needle sets horizontal. Move it toward the north end of
the magnet; the south end of the needle dips, the dip
augmenting as you approach the north pole, over which
the needle, if free to move, will set itself exactly vertical.
Move it back to the centre, it resumes its horizontality;
pass it on toward the south pole, its north end now dips,
and directly over the south pole the needle becomes ver-
tical, its north end being now turned downward. Thus
we learn that on the one side of the magnetic equator the
north end of the needle dips; on the other side the south
end dips, the dip varying from nothing to ninety degrees. If

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