Berthelot later obtained acetylene directly by passing hydrogen between the poles of a carbon arc. Carbon arc lights were the first electric lights. At first, carbon electrodes were used in carbon arc welding. Wabash used a new type of carbon arc light invented by Charles Brush in 1870. In 1915, Elmer Ambrose Sperry began manufacturing his invention of a high-intensity carbon arc searchlight. In a carbon arc lamp, the electrodes are carbon rods in free air. In the late 1930s he passed fluorine gas through a carbon arc creating fluorocarbon. Carbon arc lamps operate at high power and produce high intensity white light. A Klieg light is an intense carbon arc lamp especially used in filmmaking. The lighthouse's carbon arc lamps were powered by a steam-driven magneto. In Paris, the electric carbon arc lamp first came into use in the 1840s. In those sites, carbon arc lamps were used to simulate the flash of tram cables. In popular use, the term "arc lamp" means "carbon arc lamp" only. Elihu Thomson discovered that a carbon arc shunted with a series tuned circuit would "sing". Invented by Humphry Davy around 1805, the carbon arc was the first practical electric light.