An introduction to the mathematical theory of attraction ...

Physical Mode of Action of Forces. 3
similar to those resulting from electricity, as they may be
either attractive or repulsive, but in the case of magnetism,
forces of the two kinds are always manifested simultaneously.
The observed phenomena of magnetism ean be explained by
supposing that equal quantities of opposite kinds of magnetism are present in every element of the magnetized body,
and are located at the extremities of an infinitely short
straight line whose direction is that of the magnetization of
the element.
5. Problems to be considered.-The main problems
in the Theory of Attraction are, to find the resultant force
between t bodies, and to determine the distributions of
Electricity and Magnetism which take place under given
conditions. These problems are however, in general, so difficult that much preliminary knowledge of theorems which, in
certain cases, lead indirectly to their solution, is requisite.
6. Physical Mode of Action of Forces.-The researches of Faraday and others have shown that the electric
forces acting between two charged conductors are dependent
on the intervening medium, and are not direct action at a
distance. A similar proposition in the case of the forces due
to gravitation seems, up to the present, to be only a hypothesis.
The mechanism by which the final action is brought
about need not be considered so far as the mathematical
theory of Attraction is concerned. That theory rests only
on the hypothesis that there are certain forces having certain
definite magnitudes and directions.
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