Illuminating Engineering Society, Association of Public Lighting Engineers (Great Britain) · [London] · leaf 66
t regular intervals. It wouldprobably be better (if more frequentcleaning is not permissible) to arrangefor the intervals to be four months insummsr and two months in the darkAvinter months, Avhen dust tends toaccumulate and daylight is naturallyleast effectiAT. And it Avould also be a good plan…
Lighting
Internet Archive · Gerstein Library, University of Toronto · Public Domain Mark 1.0. Free to use for anything.
