Illuminating Engineering Society, Association of Public Lighting Engineers (Great Britain) · [London] · leaf 32
fact 1 li.it we have only been accustomed to the use of the hitter for say 160 years or SO—B periodwhich is extremely minute in comparisonwith the countless ages through which our have developed under natural light. Also, ii may be noted that the supremeindifference of our eyes to huge variations… … FIG. 1. ZENITH SKY BRICHTNESS DIURNAL VARIATION LONDON ISOBCLEAR SKY ONLY £2000 1800 1600 1400 « 1200 6 1000 t 800 t 600 400 < 200 2 o V $ % \ / / >» / ft& £> ^^ j ^* ^Gec? 0^- A.M. RM. Fig. 3. 18 THE ILLUMINATING ENGINEER (jaw.) of ample natural illumination is replacedat low…
Lighting
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