Illuminating Engineering Society, Association of Public Lighting Engineers (Great Britain) · [London] · leaf 258
rce of light, butkeeping it always perpendicularly ex-posed. (Fig. 2.) The other was keptalways at the same distance, but wasinclined at various angles.* The apparentbrightness of the two surfaces was * Bouguer used the old notation, measuringangles with the surface, not with the normalto the… … Fki. 3.—Bouguers numeratrix curve. The similarly-inclined facets are dis-tributed uniformly over the whole roughsurface ... we express them all to-gether by the lines CD CG which areperpendicular to them, and these linesare the ordinates of our curve to whichwe might give the name of Numeratrixof…
Lighting
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