3i8 



LIGHTING OF INTERIORS. 



the colour of the surroundings, (b) the height of the illuminants 

 above the plane in which the light is tested, and (c) somewhat on 

 the size of the room. Numerous tests were made in a room 

 measuring lo metres by 6J metres, having thus an area of 65 

 square metres. The lamps were arranged according to Fig. i., in 

 such a way that they could easily be placed at different heights. 



They were tested first 

 with metal shades, enamel- 

 led white, and then without 

 shades. The room had a 

 white ceiling and light yel- 

 low walls, but the paint was 

 not new, though in fair 

 condition. The lower por- 

 tion — about 1.2 metres high 

 — was painted a dark green, 

 but this had little influence 

 on the reflection, as the 

 horizontal test plane was 

 placed one metre above the floor. The average diffused reflec- 

 tion co-efficient of the room with all the furniture was approxi- 

 mately 0.5, as nearly as it could be determined. 



The light was tested by means of an illumination photometer 

 of fair accuracy along the middle of the room and along its sides, 

 and the average taken. Next the illumination was calculated 

 from the polar-curves of the lamps, taking into account the illu- 

 mination due to all the lamps in the room (4). Siemen's one watt 

 Tungsten lamps were used, with polar-curves as shown in Fig. 2. 



Fi6.1. 



Fig. 2. 



