A MODERN WONDER

Greymouth Evening Star, 12 January 1929, Page 12

A MODERN WONDER

LAMPS LIT BY DARKNESS. For nine months the street lamps in Sheen Common Drive, Barnes, London have been lighted by the agency of darkness and put out by the action of daylight. Local residents have been unaware of the wonder at work in their thoroughfare. On a recent evening I watched the miracle happening (says a special correspondent of the London “Daily Mail”). As darkness fell the lamps, one by one, lighted up simply because a selenium cell attached to them, had been influenced by the fading light. The apparatus is technically known as a light-sensitive selenium bridge. This is an apparatus which when connected across an electrical circuit lowers its electrical resistance if subjected to light—artificial or daylight. In the case of the street lamps in Harnes the mechanism switches the

lamps on and off according to whether the selenium bridge is influenced by light or darkness “The bridges affixed to the lamps in Sheen-Common Drive,” said Mr C. S. Davidson, chief engineer to the Barnes Urban District Council, “have not failed during the nine months we have been using them., We have kept the matter secret at the request of Radiovisor Patent Ltd., -which supplied them. The' selenium bridges are affected equally by fog as by darkness.”