Light and lighting . URCH UGHTinQ, This angle is 39° 10, giving an areaon the reference plane of approximately1700 square feet. 200 THE ILLUMINATING ENGINEER (april). THE ILLUMINATING ENGINEER (arun.) 201 values show a heaping up of the illumina-tion towards the middle of the figures are given in Tablj VI. Table of Kesults. Fig. 11. Position. Calculated value of horizontal illumination. Observedvalues. 1-601-44 1-88 1-51-51-5 falling off in illumination in a space of18 days continuous use varies from18*5 per cent, to 45 pei cent., dependingon the conditions o
Light and lighting . URCH UGHTinQ, This angle is 39° 10, giving an areaon the reference plane of approximately1700 square feet. 200 THE ILLUMINATING ENGINEER (april). THE ILLUMINATING ENGINEER (arun.) 201 values show a heaping up of the illumina-tion towards the middle of the figures are given in Tablj VI. Table of Kesults. Fig. 11. Position. Calculated value of horizontal illumination. Observedvalues. 1-601-44 1-88 1-51-51-5 falling off in illumination in a space of18 days continuous use varies from18*5 per cent, to 45 pei cent., dependingon the conditions of service. The estimation of the mean horizontalillumination by the flux method is inthis case particularly easy. The sym-metrical arrangement of the points, andthe flat plane of reference, neglecting theactual booking office, make it unnecessaryto draw cones for more than two lamps,as shown in Fig. 11. The summation isshown in Table VII. Hence flux for 8 lamps=4x9513=3805 lumens.
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