REVERSIBLE AND IRREVERSIBLE SYSTEMS UNDER INFLUENCE OF LIGHT. 367 
curve shows that the constant maximum was very nearly reached, i.e., the deflection 
was 118 millims. = 125"3x 1CT 9 ampere = 110 x 10“ a volt. (In all the above curves 
the deduction period was allowed to become complete.) 
We get the law of intensity also with red light (curves N2, 3, 4, 5, taken in about 
half an hour): 116 2 x 28 5 = 383,600 ; 80 2 x 60 = 384,000 ; 57 2 x 118 - 383,500. 
Curves N6 and 7 were taken with the blue and yellow-green screen at a distance 
of the light from quartz vessel = 80 centims., and the deflections obtained were 
48'5 and 41 millims. 
Thus we get for the same 80 centims. distance of light from quartz vessel :— 
Total light 
(without screen). 
Total light passing 
red screen. 
Total light passing 
blue screen. 
Total light passing 
yellow-green 
screen. 
Deflections ob- 4 
served . . .j 
168 millims. 
= 156*6 x 1CU 6 volt 
60 millims. 
= 55-9 x 10~ 6 volt 
48'5 millims, 
= 45-2 x 10~ 6 volt 
41 millims. 
= 38-2 x 10“° volt 
In per cent, of 1 
total light . . J 
100 
35-7 
28-9 
24-4 
We get the remarkable result that the light of acetylene passing the red screen 
gives with the above system the greatest deflection, and the yellow-green the 
smallest, as if two maxima were present, one near the red end of the spectrum, the 
other near the blue end of the spectrum. (This result compare with the results 
obtained with the arc.) 
The above results change very little when corrected for the thermo E.M.F., which 
is = 1 to 1'5 per cent, of the total E.M.F. created by light (see § 2). 
For the law at intensity at a constant temperature we get (July 29) :— 
In («) : 80-4 : 71 = 1T3 43’3 : 39 = I’ll 31*3 : 28 5 = 1*10 
80-8: 71 = 1-14 43*6 : 39 = 1-12 3F5 : 28*5 = 1*11 
instead of l'15, 1'13, 1’12. 
In (b) : 116 2 x 28'1 = 378 x 10 3 , 80 2 x 59’l = 378 x 10 3 , 
116 2 x 28-2 = 380 x 10 3 , 80 2 x 59‘4 = 380 x 10 3 , 
instead of 384 x 10 3 ; 384 xlO 3 ; 384 xlO 3 ; 387 xlO 3 . 
57 2 x 116-2 = 378 x 10 3 , 
57 2 x 116-8 = 380 x 10 3 , 
Arc (Duboscq) and Coloured Screens , Plate 13 of July 29, 1903 ( Curves N 3, 9, 10, 
11, 12, 13). Experimental data , see Table III. 
We get for the total light without screen in N8 = 76 millims., in NlO = 69 millims., 
in Nl4 = 71‘5 millims., for the blue screen in N9 = 23 millims., for the red screen in 
Nil = 5 millims., for the yellow-green screen in Nl2 = 3"5 millims. (for the thinner 
