854 
dish in the light path of the lamp Lp is filled with an asphalt 
solution; filter Fr is superfluous here. 
c. For rays of 0,640 u to 0,535 u; centre of the intensity estimated 
at 0,58 wu; we shall therefore indicate this wave-length region by 
“yellow”. 
d. For rays of from 0,590 u to 0,435 u, with the centre of 
intensity estimated at 0,54 u. This region is indicated by “green”. 
At c and d in the light path is placed a 3°/, copper-chloride 
solution, and besides a coloured gelatine filter as is sold by the firm 
Kipp, at c the filter 3Cc, at d the filter 5Ac. 
e. For the whole spectrum, Neither dish Ct nor Pr is placed in 
the light path. 
We find in fig. 2 both for hydroquinone and for gelatine the ratio 
b c . 
7 and ji plotted against d as independent variable. Thus two curves 
C ( 
120 | ake tei a ae 
as Cea 
HM, =Hydrochinon ;ultrarood. O 
[y= : Geel MES 
G,=Glycine —_,ultrarood. D 
Gy = ; „geel .® 
at ==] JE | 
ES 04 06 08 10 12 LA 18 20 22 2 
Fig. 2. 
are obtained for glycin, denoted by the letters G, and G, and two 
for hydroquinone, indicated by H, and H,’). 
1) Only the four blackenings of plate 1 have been measured, besides for 
b, c and d, also for the whole spectrum and for the whole spectrum except 
ultra-red. 
In fig. 2 only 5 and - of plate 1 have been plotted against d. All the 
measurements, however, are found in the table 1 adjoined to this communication. 
