Written by Lightning: A short story of lightning recorders: ceraunographs, electrographs, klydonographs Part 2 From Lancetta's Electrograph to Peters's Klydonograph and its Improvements

摘要

Lancetta's Electrograph: In 1901 Pietro Lancetta, who was professor of physics at the Technical Institute of Girgenti (Agrigento) proposed an apparatus called recording electrograph. The original instrument was manufactured in the workshop of the above-mentioned institute and was composed by a detector and a recorder. The former was a usual metallic powder coherer connected to an antenna, while a moving needle galvanometer acted as a relay, exactly like in the Schreiber-Fenyi device (Fig.l). When the resistance of the coherer suddenly decreased under the action of an electric discharge, the current of a battery flowed into the coil and deflected the magnetic needle which closed a contact of a second circuit including an electric bell. Its oscillating arm not only tapped the coherer, but thanks to a pencil fixed on it, at the same time recorded the discharge on a paper disk fixed to a clockwork mechanism. Lancetta also proposed to use this instrument as a Hertzian wave detector in classroom demonstrations. The electrograph was successfully presented at the 1901 Roman 'Esposizione Internazionale Grandinifuga' (see cover) where Lancetta was awarded a silver medal.