Illuminating Engineering Society, Association of Public Lighting Engineers (Great Britain) · [London] · leaf 339
ure makes it possible to obtain amore perfect photometric balance than is the case with probablv any instrumentexcept the Lummer Brodhem. The advantage of this arrangement isthat there is no line of demarcation visiblebetween the two screens as the thicknessof thesilver deposit ed is… … A 4-
Lighting
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