sequent after-oscillation. 
INORGANIC RESPONSE 
163 
effect attains a maximum at which it remains constant 
for some time. 
If the exposure be maintained after 
this for a longer period, there will be a decline, as 
we found to be the case in other instances of continued 
stimulation. 
The appearance of this decline, and its 
rapidity, depends on the particular condition of the 
substance. 
When the sensitive element is considerably strained 
by the action of light, and if that lHght be now cut 
— 
= 
=— 
- 
Sy 
\ 
en ae 
Fic. 105.—ArrEer-OscILLATION 
Exposure of one minute followed by obscurity of one minute. 
Note the decline 
during illumination, and after-oscillation in darkness. 
off, there is a rebound towards recovery and a sub- 
That is to say, the curve of 
recovery falls below the zero point, and then slowly 
oscillates back to the position of equilibrium. We 
have already seen an instance of this in fig. 102. Above 
is given a series of records showing the appearance 
of decline, from too long-continued exposure and re- 
covery, followed by after-oscillation on the cessation 
of light (fig. 105). 
Certain visual analogues to this 
phenomenon will be noticed later. 
M 2 
