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1850 __ The coherence of electrified dust particles in air
Pierre Guitard (?-?)
Comment : The coherence of dust particles in air, when electrified, was discovered by Pierre Guitard of France.In 1850 Pierre Guitard found that when dusty air was electrified, the particles of dust would tend to attach themselves together in the form of strings. Again, in 1879, it was observed that drops of water from a small fountain, when exposed to the influence of a charged piece of sealing-wax, would not separate into small drops, but would cohere into large ones. It is probably due to the same principle that the drops of rain are so much larger in thunderstorms than in ordinary showers: electric charge on the clouds probably causes the drops of water to cohere into large ones. Temistocle Calzecchi-Onesti is thought to have performed the first experiments with a predecessor of the coherer in 1884. These phenomena had been observed for many years, but it was not until 1890 that Edouard Branly made a practical application of the principle in the form of the filings coherer as it is now known. The invention of the device is usually credited to Branly. (Compiled from various sources)
French comment : 1850 : Découverte par le Français Pierre Guitard de l’attraction mutuelle des poussières de l’air lorsqu’elles sont chargées.En 1891, le physicien et médecin Français Édouard Branly présenta ses travaux relatifs à la cohésion de petites particules sous l’effet de l’électricité. Cet effet avait déjà été observé par le français Guitard en 1850, puis par des chercheurs en Angleterre et en Italie, mais il n’avait pas encore donné lieu à une application pratique. En augmentant la portée des liaisons, le cohéreur mis au point par Branly joua un rôle essentiel lors des premières liaisons hertziennes. Branly fut également un expérimentateur dans le domaine de la télécommande par radio. En 1911 il fut élu à l’Académie des Sciences. (In Freddy GARDIOL, Yves FOURNIER, "Salvan, berceau de la Télégraphie Sans Fil TSF", avril 2008)
Source : Coe, Douglas (1943), "Marconi, pioneer of radio", J. Messner Inc., p. 22.
Source : Dunlap, Orrin Elmer (1951), "Radio & Television Almanac : men, events, inventions, and dates that made history in electronics from the dawn of electricity to radar and television", Harper, p. 16.
Urls : http://www.see.asso.fr/htdocs/upload/1106_Invite_08_04.pdf (last visited )

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