1896.] of Moonlight and Starlight compared with Candle. 319 



Diagram 2 shows the curves plotted from the above table, and 

 from it is derived the distance apart of the parallel curves, which is 

 0"47, that is, the light of the moon on this occasion is 2 0,47 = ]'38 

 times less photographically bright than the candle at 5 feet from the 

 plate. The moon was therefore equal to 0725 candle at 5 feet, or 



DlAGrEAM 2. 



HQ , . . . , , , 1 , , r- 1 , , r — i — . 



10 



I 1 1 1 t 1 I 1 I I 1 1 11 8 1 I I 1 I 11 1 11 11 



Intensity in powers of 2. 



to one standard' candle at 5*32 feet, or to O035 standard candle at 

 1 foot distant from the plate. The moon was almost exactly at its 

 first quarter. If the light of the full moon were only double, then 

 the value would be 0*07 standard candle at 1 foot distance. 



Not having an opportunity to make a measurement of the light at 

 f nil moon at Chamounix, the investigation was continued in England. 

 In February the weather was intensely cold, and the nights were 



