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<p>The photometry of the high-efficiency gas-filled lamp presents difficulties not yet experienced with other types of lamps. The consumption and candle power are found to vary with the position of the lamp, both being greater with the lamp mounted tip up than when it is mounted tip down; if the lamp be rotated to obtain its mean candle-power it is found that the consumption and candle-power vary with the speed of rotation and that the flickering in the photometer is much greater than when rotating other types of lamps. This excessive flickering is due to the usual tack of symmetry of the filament about the axis of the lamp, and may be counteracted by placing two inclined mirrors behind the lamp so that the photometer is simultaneously illuminated by the%
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<br>Subjects: lamps and lighting/ B8530B Light sources</div>
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