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 will
be most felt by those who are best trained in ordinary theoretic
conceptions. He does not know the reader's needs, and he therefore
does not meet them. For instance he speaks over and over again of
the impossibility of charging a body with one electricity, though the
impossibility is by no means evident. The key to the difficulty is this.
He looks upon every insulated conductor as the inner coating of a Leyden
jar. An insulated sphere in the middle of a room is to his mind such a
coating; the walls are the outer coating, while the air between both is
the insulator, across which the charge acts by induction. Without this
reaction of the walls upon the sphere you could no more, according to
Faraday, charge it with electricity than you could charge a Leyden jar,
if its outer coating were removed. Distance with him is immaterial. His
strength as a generalizer enables him to dissolve the idea of magnitude;
and if you abolish the walls of the room--even the earth itself--he
would make the sun and planets the outer coating of his jar. I dare not
contend that Faraday in these memoirs made all his theoretic positions
good. But a pure vein of philosophy runs through these writings; while
his experiments and reasonings on the forms and phenomena of electrical
discharge are of imperishable importance.

Footnotes to Chapter 8

[1] Newton's third letter to Bentley.

[2] Had Sir Charles Wheatstone been induced to resume his
measurements, varying the substances through which, and the
conditions under which, the current is propagated, he might
have rendered great service to science, both theoretic and
experimental.

Chapter 9.

Rest needed--visit to Switzerland.

The last of these memoirs was dated from the Royal Institution in June,
1838. It concludes the first volume of his 'Experimental Researches on
Electricity.' In 1840, as already stated, he made his final assault on
the Contact Theory, from which it never recovered.[1] He was now feeling
the effects of the mental strain to which he had been subjected for so
many years. During these years he repe