Illuminating Engineering Society, Association of Public Lighting Engineers (Great Britain) · [London] · leaf 545
isitor coming to the door to be recog- point in a long passage at which a step nized at once. occurs. Originally this was difficult The second illustration shows a very to distinguish from a distance owing simple device employed in the chemical to the fact of the upper and lower levels laboratories… … Fig. 5.—The piece of cardboard mark:step which is difficult to see. the Fig. (>.—The same step made visible by a whiteline extending some distance up the wall. base block, and fitted with a curvedwhitened zinc shade as sho\\n. Thelamp is then completely screened fromthe students eyes, and the…
Lighting
Internet Archive · Gerstein Library, University of Toronto · Public Domain Mark 1.0. Free to use for anything.
