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electric clocks

 A history of the evolution of electric clocks

Before considering electrical horology, let's take a quick glance at the history of electricity and magnetism.
Electricity and Magnetism


Mankind has know electric effects in the form of lightning from the earliest times but the nature of these effects was of course unknown to him. Sailors were sometimes startled to see a flickering luminous light at the tips of a ship's mast and spars: the famous Saint Elmo's fire.

The first man-made electricity was discovered by the rubbing of amber. Amber, a pale yellow translucent fossil, has the ability to attract light objects such as paper and feathers when it is rubbed.

Some 3,000 years B.C. the Chinese were already aware that lodestone, a magnetic oxide of iron, attracts small pieces of iron. The Chinese were also aware of lodestone pointing to the North Pole and used it for navigational purposes.

In 1600 William Gilbert (1540-1603), physician to Queen Elisabeth and King James, was the first to explain the nature of magnetism. In his book "De Magnete" he called the mysterious forces involved: "electrics". This illustration shows how hot steel was magnetized by hammering it while held in the magnetic meridian.

In 1660 Otto von Guericke (1602-1686) was the first to make a machine producing electricity.
Von Guericke is also well known for his invention of the vacuum air pump and his famous experiment with the Magdeburg hemispheres in 1654.


By rotating a globe of sulphur, it is electrically excited by the friction of a hand held against it. The globe could be carried about to attract, and repel, light objects such as paper and feathers.


This effect is now known to us as static electricity, meaning very high voltage but of extreme low power.
In 1745 .Pieter van Musschenbroek (1692-1761), a Dutch physicist, was engaged in a research to determine the strength of electricity. In doing so, he probably was the first to experience, quite accidentally, the discharge of a Leyden jar through the human body.

With the invention of the Leyden jar electricity could now be stored in large quantities, held sometimes for days, and discharged at will.
In 1678 Jan Swammerdam (1637-1680), a Dutch microscopist , demonstrated the contraction of a dissected frog's leg when its nerve is touched by a metal wire.

It was not until 1786 that Luigi Galvani (1737-1798), professor of
anatomy at Bologna, explained this phenomenon by the production of a "nerveo-electrical" fluid similar to that of frictional electricity.
Alessandro Volta (1745-1827), an Italian physicist, disagreed with Galvani'sVolta pile explanation. In 1796 Volta constructed a pile of a large number of alternate silver and zinc disks and placed a piece of cloth,crown of cups moistened with a salty solution, between every other disk.
The fi
rst battery was invented: the Volta pile.
However, this battery was n
ot very practical and had very little power.
Volta soon improved his invention by devising his "Crown of Cups", a number of cups filled with sulphuric acid into which metal strips were dipped. Half of these strips were copper and the other half zinc.
The difference  between static electricity and electro-dynamic electricity was now fully understood. Assuming that the tiny figures are electrons, one can better understand the difference between a static electric charge and an electric current. In a static charge all the electrons are on the surface and at rest, except here and there an occasional electron that escapes. In the case of an electric current the electrons rush along the inside of the conductor.
Inventions now followed in rapid succession:

1820
André Marie Ampčre (1775-1836), a French physicist, discovered the solenoid: a spiral coil of wire that behaves like a magnet when an electric current flows through it.
1825
William Sturgeon (1783-1850), an English army physicist, invented the first electro-magnet by winding bare copper wire, insulated by silk thread, around a soft iron bar. When a current flows through the copper wire the iron becomes a magnet. When the current ceases the iron is no longer a magnet.
1827
George Simon Ohm (1789-1854), a German physicist, formulated his famous law connecting voltage, current and resistance in an electric circuit (V=I.R).
1828
Joseph Henry (1797-1878), professor of Princeton N.J., created an electro-magnet of much greater strength and efficiency by winding the iron core with several more layers of wire and bending its shape:
the horse-shoe magnet.
1831
Michael Faraday (1791-1867), professor of physics, devised a machine to convert mechanical energy into electricity. A copper disk was mounted between the poles of a big horse-shoe magnet and the rim and axle of the disk were connected to a galvanometer. When the disk rotates the galvanometer needle moves.
The dynamo was invented, for the first time a steady current of electricity could be produced without the use of a battery.Daniell battery
1836
John Frederic Daniell (1790-1845), an English chemist, invented the first reliable galvanic element: the Daniell battery.

Now reliable sources of energy are available electricity can be applied to horology.
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Electricity & Horology    A. Electrostatic clocks


Introduction
Electricity & Magnetism
Electricity & Horology
   A.Electrostatic clocks
   B.The first inventors
   C.Independency of battery
   D.Reliability of contact making
   E.Synchronization
   F.Count-wheel and impulse
   G.The first free pendulum
   H.Shortt's free pendulum
Conclusion
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