All About Inventions and Discoveries
The Romance of modern scientific and mechanical Achievements

222 All About Inventions carbon, each about one-sixth of an inch in diameter, set parallel and separated by a thin insulating barrier formed of kaolin porcelain. At the top the two carbons were connected by a carbon paste to strike the arc. When the current, supplied from a Gramme machine, was switched on, this paste connection was readily heated up to such a degree as to volatilise. While this action was taking place the extremities of the carbon rods were also becoming heated to a sufficient degree, so that, when the paste connection had disappeared, the arc could be maintained across the gap between the two rods, and also the intervening porcelain insulator. The latter was burned away at the same speed as the carbons themselves, so that the arc was maintained without difficulty until the carbons had been burned out. But, as already explained, with two carbons of equal dimensions the positive rod is consumed about twice as rapidly as the negative rod. To overcome this inequality in consumption carbons of varying diameter were first used, though subsequently alternat- ing current was employed, which enabled carbons of one diameter to be used. The light emitted from this electric “ candle,” while not very brilliant, was far superior to that given by gas-burners of the period. Consequently the Jablochkoff candles had quite an exciting vogue in Europe, several thousands being sold. Electric arc-lighting was introduced thereby to London, the exterior of the old Gaiety Theatre in the Strand being one of the first places to be illumin- ated in this manner. The candles, however, suffered from a comparatively short life, the average duration of the light being from ij to 2 hours. When they