In the researches now under review the ratio of speculation and
reasoning to experiment is far higher than in any of Faraday's
previous works. Amid much that is entangled and dark we have
flashes of wondrous insight and utterances which seem less the
product of reasoning than of revelation. I will confine myself here
to one example of this divining power. By his most ingenious device
of a rapidly rotating mirror, Wheatstone had proved that electricity
required time to pass through a wire, the current reaching the
middle of the wire later than its two ends. 'If,' says Faraday,
'the two ends of the wire in Professor Wheatstone's experiments were
immediately connected with two large insulated metallic surfaces
exposed to the air, so that the primary act of induction, after
making the contact for discharge, might be in part removed from the
internal portion of the wire at the first instance, and disposed for
the moment on its surface jointly with the air and surrounding
conductors, then I venture to anticipate that the middle spark would
be more retarded than before. And if those two plates were the
inner and outer coatings of a large jar or Leyden battery, then the
retardation of the spark would be much greater.' This was only a
prediction, for the experiment was not made.[2] Sixteen years
subsequently, however, the proper conditions came into play, and
Faraday was able to show that the observations of Werner Siemens,
and Latimer Clark, on subterraneous and submarine wires were
illustrations, on a grand scale, of the principle which he had
enunciated in 1838. The wires and the surrounding water act as a
Leyden jar, and the retardation of the current predicted by Faraday
manifests itself in every message sent by such cables.

The meaning of Faraday in these memoirs on Induction and Conduction
is, as I have said, by no means always clear; and the difficulty