s with the
electricities; when evolved at the poles, they are de-electrified.

516. I have sought amongst the various experiments quoted in support of
these views, or connected with electro-chemical decompositions or electric
currents, for any which might be considered as sustaining the theory of two
electricities rather than that of one, but have not been able to perceive a
single fact which could be brought forward for such a purpose: or,
admitting the hypothesis of two electricities, much less have I been able
to perceive the slightest grounds for believing that one electricity in a
current can be more powerful than the other, or that it can be present
without the other, or that one can be varied or in the slightest degree
affected, without a corresponding variation in the other[A]. If, upon the
supposition of two electricities, a current of one can be obtained without
the other, or the current of one be exalted or diminished more than the
other, we might surely expect some variation either of the chemical or
magnetical effects, or of both; but no such variations have been observed.
If a current be so directed that it may act chemically in one part of its
course, and magnetically in another, the two actions are always found to
take place together. A current has not, to my knowledge, been produced
which could act chemically and not magnetically, nor any which can act on
the magnet, and not _at the same time_ chemically[B].

[A] See now in relation to this subject, 1627-1645.--_Dec. 1838._

[B] Thermo-electric currents are of course no exception, because when
they fail to act chemically they also fail to be currents.

517. _Judging from facts only_, there is not as yet the slightest reason
for considering the influence which is present in what we call the electric
current,--whether in metals or fused bodies or humid conductors, or even in
air, flame, and rarefied elastic media,--as a compound or complicated
influence. It has never been resolved into simpler or elementary
influences, and may perhaps best be conceived of as _an axis of power
having contrary forces, exactly equal in amount, in contrary directions_.

* * * * *

518. Passing to the consideration of electro-chemical decomposition, it
appears to me that the effect is produced by an _internal corpuscular
action_, exerted according to the direction of the electric current, and
that it is due to a force either _super to_,