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<p>In America the Hefner lamp is taken as the primary standard, but the luminous intensity of a source is expressed in British parliamentary candles (using the ratio 1 Hefner = 0.88 British candle). Recent experiments, however, have not confirmed this number. It is 2 per cent. different from that obtained from the Bureau of Standards glow-lamps. If the British candle be taken as one-tenth the intensity of the Harcourt (10-c.p.) pentane lamp at the National Physical Laboratory, according to the values assigned the Bureau of Standards glow-lamps, it is 2 per cent. different from the candle in America obtained from the Hefner lamp by means of the ratio 0.88. If the British candle be taken as one-tenth the intensity of /b any/ (10-c.p.) Harcourt lamp, expe
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<br>Subjects: photometry; lamps and lighting</div>
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