ch fully agrees
with our physical conception of the Aether which was arrived at by
purely philosophical reasoning, based on Newton's Rules of Philosophy.

Thus we are able to combine into one whole by our conception that Aether
is matter, and therefore atomic and gravitative, not only Faraday's
Lines of Force, but also Maxwell's physical conception of the same,
apart from the solutions given to the other problems of science by the
self-same conception, which solutions will be dealt with in their proper
order.

As further evidence of Maxwell's belief in the physical existence of
Faraday's Lines of Force, let me again quote from his paper on "Action
at a Distance,"[36] already referred to in Art. 43. He writes: "Its
minute parts may have rotatory as well as vibratory motions, and the
axes of rotation form those lines of Magnetic Force which extend in
unbroken continuity into regions which no eye has seen.... These lines
must _not be regarded as mere mathematical abstractions_. They are the
directions in which the medium is exerting tension like that of a rope,
or rather like that of our own muscles."

[Footnote 34: _Exp. Res._]

[Footnote 35: _Magnetism and Electricity._]

[Footnote 36: _Collected Works_, by Niven.]

ART. 90. _Terrestrial Magnetism._--We have already seen that the earth
is a magnet, and like any other magnet will therefore possess its
magnetic field with its magnetic lines of force. The earth's magnetic
field is co-existent and co-equal with its electric field (Art. 80), and
that is co-existent with the earth's aetherial atmosphere which is held
bound to the planet by the force of gravity.

How far the earth's magnetic field reaches, is impossible to say, but we
know that it extends at least as far as 260,000 miles, the distance of
the moon; as we find that this satellite of the earth is affected very
considerably by the electro-magnetic attractive power of the earth. Any
body which is placed in the earth's magnetic field is affected by the
lines of force which exist in the magnetic field; for wherever the field
exists, there the lines of force exist also.

These lines of force, which are associated with the earth, extend
therefore into space, and any body such as the moon would become a
magnet, if not already one by the process known as magnetic induction,
which physical process is well illustrated in the action of a magnet
upon iron filings strewed over it as in the illustration (Art. 88).