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Sixty or more pieces of ...
silver, applied each to a piece of tin or zinc ... and as many strata of cardboard,
soaked in salt solution, interposed between every pair of metal discs, and always
in the same order, constitutes my new instrument.
. . . an apparatus having resemblance in its effects
. . . to an electric battery . . .
— Alessandro Volta, in a letter
to Sir Joseph Banks, 1800.
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Now twist a copper wire into
a ring very nearly of the same circumference as the flat zinc ring, and putting
it round the plant, let it rest upon the zinc, as in the illustration. No slug or
snail will cross that magic circle; they can drag their slimy way upon the zinc
well enough, but let them but touch the copper at the same time and they will receive
a galvanic shock sufficient to induce them at once to recoil from the barrier.
— Septimus Piesse in Scientific
American May 2, 1863, p. 276.
For the sake of portability,
many forms of Leclanché cell have been constructed in which there is no free liquid
present. In most of these there is a paste containing manganese dioxide surrounding
a carbon rod. This is in contact with a layer of sawdust, or in some cases, plaster
of Paris, saturated with sal-ammoniac. The whole is contained in a zinc case which
forms the negative electrode.
— J. Duncan and S. G. Starling,
A Text Book of Physics, Macmillan, 1918, p. 912.
. . . the magnetic needle was
moved from its position by the help of the galvanic apparatus when the galvanic
apparatus was closed, but not when open . . .
— Hans Christian Oersted (1777-1851
Oersted would never have made
his great discovery of the action of galvanic currents on magnets had he stopped
in his researches to consider in what manner they could possibly be turned to practical
account; and so we would not now be able to boast of the wonders done by the electric
telegraphs. Indeed, no great law in Natural Philosophy has ever been discovered
for its practical implications, but the instances are innumerable of investigations
apparently quite useless in this narrow sense of the word which have led to the
most valuable results.
— Lord Kelvin (1824-1907), quoted
in R. A. Gregory, Discovery (1916), p. 241-2.
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Electric relay |
— Edward Davy, (1806-1885),
inventor of the electrical relay.
Few of our readers have heard
of the name of Edward Davy in connection with the history of the telegraph . .
. nothing has been published of his labours. Yet it is certain that, in those days,
he had a clearer grasp of the requirements and capabilities of an electric telegraph
than, probably, Cooke and Wheatstone themselves . . .
— J. J. Fahie, The Electrician,
July 7, 1883.
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