322 



LIGHTING OF INTERIORS. 



Without shades, if taking- into account the mean spherical 

 candle power of the lamp we get Fig. 13. 



P£R CENT tNCRE^S»E IN ILLUMINATION 



WHITE 



mmom 



CnEM 



CREAn 

 5ILVEQY 



LIGHT YELLOy 



100 200 ^> 00 CENTIMETPES 



DISTANCE OF LA HP A50YE TESTING PLANE . 



Fig. II. 



The figures given in these curves hold, of course, strictly 

 speaking, only for a particular room, but experiments tell me that 

 they can be used with fair accuracy for any other room with 

 distributed lights. 



Example. — We are asked to fit up a room with a floor space 

 of 100 sq. metres, with electric light so as to give an average illu- 

 mination of 25 candle-metres. The walls are light yellow. From 

 Fig. 12 it follows that per square metre surface we require 3.2 

 candles if the lamps are fixed 200 cms. above the testing plane, 

 or 3 metres above the floor. For any other illumination or height 

 of lamps, the light can be easily determined. 



INDIRECT LIGHTING. 



In the tests the same room was used ; also the same lamps and 

 shades, which were simply reversed. The illumination depended 



