Tracking Down the Origin of Arc Plasma Science. II. Early Continuous Discharges

II. Early Continuous Discharges André Anders, Fellow Lawrence Berkeley National Laboratory, University of California, 1 Cyclotron Road, Berkeley, California 94720-8223 [email protected] ABSTRACT Continuous discharges could only be obtained after enduring energy sources became available, namely in the form of a battery of electrochemical cells, invented by Volta in late 1799. Humphry Davy is generally credited with the discovery of the arc discharge and the invention of the carbon arc lamp. Indeed, as early as 1800, he obtained short pulsed arcs with his Voltaic pile. Independently, and earlier than Davy in the sense of continuous discharges, the Russian Vasilii Petrov of St. Petersburg made carbon arcs in 1802. Petrov used a pile of 4200 electrochemical cells to drive what was the most powerful discharge at that time. Petrov’s publication of 1803 appeared only in Russian, and his work was ignored and forgotten for over century. Davy pursued highly successful electrochemical experiments and was unaware of Petrov’s work. He increased the size of his battery in several steps, which led to increasingly powerful discharges, most likely an undesired side effect. After 1808, using the new 2000-element battery of the Royal Institution, Davy demonstrated continuous arc discharges in the institution’s theatre before large audiences, thereby establishing arc physics as a lasting science.