How did the Yablochkov candle work?

The Yablochkov candle was a pioneering arc lamp developed by Russian engineer Pavel Nikolayevich Yablochkov in 1876. It served as the first arc lighting system to achieve widespread practical application, particularly for street lighting in European cities.21

The device functioned by maintaining an electric arc across a gap between two parallel carbon rods. Unlike earlier designs that required complex mechanisms to maintain the gap as the electrodes consumed, the Yablochkov candle utilized a nonconducting clay partition placed between the two rods. As the carbons burned away during operation, this clay partition gradually vaporized, ensuring the arc remained stable.2

While highly effective for its time, the system was eventually superseded by the development of incandescent lighting.2