onclusion, without affirming some such hypothesis as we have affirmed
in relation to the cause of all solar magnetism.

Let me at once point out, this solution has already been offered by one
whose name has been referred to several times. I refer to Professor
Challis. Let us see what he has to say as to the cause of the earth's
magnetism. In dealing with this subject, and writing in the _Phil.
Mag._, 1872, par. 42, he states: "With respect to all magnetism which
has a cosmical origin, the view I now take is that it is due to
gyrations of the Aether, produced by the impulses which it receives from
the motions of the constituent atoms of the bodies of the solar system.
The gyrations may either be immediately generated by the rotations of
the bodies about their axes, or directly result from disturbances of the
Aether caused by their motions of translation. This impressed motion
will be converted into circulatory or gyratory motion. Such circulatory
motion will necessarily partake of the motion of translation of the
bodies which generate them, so as to have always the same geometrical
relation to these bodies provided their motion be uniform."

In paragraph 46 he continues: "From what has been already argued (42),
the motions impressed on the Aether by the earth in consequence of its
rotatory or orbital motions result in circulating motions which would be
steady motions, having always the same geometrical relation to the
position of the earth's centre."

Again, Ampere and Faraday were also of the opinion that the magnetism of
the earth was due to the circulation of electric currents round it, for
in par. 446, _Exp. Res._, Faraday states: "Assuming with Ampere that the
magnetism of the earth is due to electric currents circulating round it,
parallel to the equator."

I think it will be seen from these extracts that the hypothesis
suggested for all planetary and stellar magnetic bodies is thus
confirmed by Professor Challis, and by Faraday and Ampere. Professor
Challis in these passages clearly and definitely points out that there
are circulatory motions in the Aether, which motions are produced by the
rotation of the earth or other body on its axis, and that these circular
motions of the aetherial medium always maintain the same geometrical
shape relative to the earth's centre. So that we have only to combine
with his hypothesis the electro-magnetic basis of the Aether, and we at
once get the circulating currents of elect