The standard electrical dictionary : a popular encyclopaedia of words and terms used in the practice of electrical engineering (1898)
Sloane, T. O'Conor (Thomas O'Conor), 1851-1940 · London : Crosby Lockwood and Son · leaf 417
Sometimes a Leeson disc is used. Thisconsists of three pieces of paper, two thin ones between which athicker piece, out of which a star is cut, is laid. WTien equally illu-minated on both sides the star appears equally bright oh both sides. The bar photometer is the stardard form. A candle or pair… … Fig-. 259. Bar Photometer. Photometer, Calorimetric. A photometer in which the radiantenergy, so called radiant heat, is used as the measurer of the light. In one type a differential air thermometer is used, one of whosebulbs is blackened. On exposing this bulb to a source of light itwill become…
Electricity
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