# J. C. Maxwell’s, ‘Dynamical theory of the electromagnetic field’

```                                Note on the Attraction of Gravitation

82 After tracing to the action of the surrounding medium both the
magnetic and the electric attractions and repulsions, and finding them
to depend on the inverse square of the distance we are naturally led
to enquire whether the attraction of gravitation which follows the
same law of the distance is not also traceable to the action of a surrounding
medium.
Gravitation differs from magnetism and electricity in this, that the
bodies concerned are all of he same kind, instead of being opposite
signs lie magnetic poles and electrified bodies and that the force between
these bodies is an attraction not a repulsion as is the case between
like electric and magnetic bodies.

The lines of gravitating force near two dense bodies are exactly
of the same form as the lines of magnetic force near two poles of the
same name, but whereas the poles are repelled, the bodies are
attracted. Let E be the intrinsic energy of the field surrounding two gravitating
bodies M<sub>1<\sub>M<sub>2<\sub> and let E' be the intrinsic energy of the field surrounding
two magnetic poles m<sub>1<\sub>m<sub>2<\sub> <s>proportional<\s> equal in numerical value to
M<sub>1<\sub>M<sub>2<\sub> and let X be that gravitating force during the displacement [delta]x
and X' the magnetic force
X[delta]x = [delta]E x'[delta]x = [delta]E'
Now X and  X' are equal in numerical value but of opposite signs
so that [delta]E = - [delta]E'
or E = C - E'
= C - [capital sigma]1/8[pi]([alpha]<sup>2<\sup> + [beta]<sup>2<\sup> + [gamma]<sup>2<\sup>)dV
where [alpha] [beta] [gamma] are the components of magnetic intensity. If R be the
resultant gravitating force and R' the resultant magnetic force at a
corresponding part of the field. R - R' and
[alpha]<sup>2<\sup> + [beta]<sup>2<\sup> + [gamma]<sup>2<\sup> = R<sup>2<\sup> = R'<sup>2<\sup>
Hence E = C = [capital sigma]1/8[pi] R<sup>2<\sup> dV  47
The intrinsic energy of the field of gravitation must therefore be
<s>diminished<\s> less wherever there is a resultant gravitating force

```
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## Manuscript details

Author
James Clerk Maxwell
Reference
PT/72/7
Series
PT
Date
1864
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## Cite as

J. C. Maxwell’s, ‘Dynamical theory of the electromagnetic field’, 1864. From The Royal Society, PT/72/7