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Saturday, 31 January 2015

Batteries included

Some more bits from my quotations collection:The world changed in a curious way in 1800, when Alessandro Volta wrote to Sir Joseph Banks about his piles. Voltaic piles were batteries, though. Once the pile was common, people could discover electrolysis, chemistry got a leg-up, and in time, teenagers would be able to share boom-tish and doof-doof with their fellow passengers on train and bus.You can't win them all.  Mind you, the fellow on the right was a bigger loser than most.

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.

Having a few pet plants which slugs and snails are particularly fond of as food, I have devised the following simple and efficacious mode of protecting them against their and my enemies ; and as this plan may be useful to some of your readers, I herewith send you a description of my galvanic circle. Procure a flat ring of zinc, large enough to encircle the plant; make a slit in the ring after the manner of a keyring, so that it can be put round the stem of the plant and then rest upon the ground.

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.

Electric relay
The quantity of electricity requisite to deflect a magnetic needle is so inconsiderable, that if the current of a moderately-sized pair of plates were sent into one end of a wire, and only one-hundredth part of it came out at the other end, it would still be sufficient.
— 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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