experimental apparatus were
quite similar, especially the "dark box" with micrometer adjustment,
used by both in observing the spark. [25]

[Footnote 25: During the period in which Edison exhibited
his lighting system at the Paris Exposition in 1881, his
representative, Mr. Charles Batchelor, repeated Edison's
remarkable experiments of the winter of 1875 for the benefit
of a great number of European savants, using with other
apparatus the original "dark box" with micrometer
adjustment.]

There is not the slightest intention on the part of the authors to
detract in the least degree from the brilliant work of Hertz, but, on
the contrary, to ascribe to him the honor that is his due in having
given mathematical direction and certainty to so important a discovery.
The adaptation of the principles thus elucidated and the subsequent
development of the present wonderful art by Marconi, Branly, Lodge,
Slaby, and others are now too well known to call for further remark at
this place.

Strange to say, that although Edison's early experiments in "etheric
force" called forth extensive comment and discussion in the public
prints of the period, they seemed to have been generally overlooked
when the work of Hertz was published. At a meeting of the Institution of
Electrical Engineers, held in London on May 16, 1889, at which there
was a discussion on the celebrated paper of Prof. (Sir) Oliver Lodge on
"Lightning Conductors," however; the chairman, Sir William Thomson (Lord
Kelvin), made the following remarks:

"We all know how Faraday made himself a cage six feet in diameter, hung
it up in mid-air in the theatre of the Royal Institution, went into it,
and, as he said, lived in it and made experiments. It was a cage with
tin-foil hanging all round it; it was not a complete metallic enclosing
shell. Faraday had a powerful machine working in the neighborhood,
giving all varieties of gradual working-up and discharges by 'impulsive
rush'; and whether it was a sudden discharge of ordinary insulated
conductors, or of Leyden jars in the neighborhood outside the cage, or
electrification and discharge of the cage itself, he saw no effects on
his most delicate gold-leaf electroscopes in the interior. His attention
was not directed to look for Hertz sparks, or probably he might have
found them in the interior. Edison seems to have noticed something of
the kind in what he called the etheric force. His name 'et