Not only its rapidity of progression, but its ability to
produce the motion of light and heat, indicates that the electric
current is also motion.[1] Further, there is a striking resemblance
between the action of good and bad conductors as regards electricity,
and the action of diathermanous and adiathermanous bodies as regards
radiant heat. The good conductor is diathermanous to the electric
current; it allows free transmission without the development of
heat. The bad conductor is adiathermanous to the electric current,
and hence the passage of the latter is accompanied by the
development of heat. I am strongly inclined to hold the electric
current, pure and simple, to be a motion of the ether alone; good
conductors being so constituted that the motion may be propagated
through their ether without sensible transfer to their atoms, while
in the case of bad conductors this transfer is effected, the
transferred motion appearing as heat.[2]
I do not know whether Faraday would have subscribed to what is here
written; probably his habitual caution would have prevented him from
committing himself to anything so definite. But some such idea
filled his mind and coloured his language through all the later
years of his life. I dare not say that he has been always
successful in the treatment of these theoretic notions. In his
speculations he mixes together light and darkness in varying
proportions, and carries us along with him through strong
alternations of both.
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