INORGANIC RESPONSE 107 
recovery is delayed, as the effect of overstrain. Curve 
(a) is for a single stimulus due to a vibration of 
amplitude 20°, and curve (6) for a stimulus of 40° 
amplitude of vibration. It will be noticed how rela- 
tively prolonged is the recovery in the latter case. 
Molecular Model.— We have seen that the electric 
response is an outward expression of the molecular 
disturbance produced 
by the action of the 
stimulus. The rising 
part of the response- 
curve thus exhibits the 
effect of molecular upset, 
and the falling part, or 
recovery, the restoration 
to equilibrium. The me- 
chanical model (fig. 62) 
will help us to visualise 
many complex response 
phenomena. The mo- 
lecular model consists 

c a e 
Fic. 62.—Moprn sHow1NG THE EFFECT OF FRICTION 
of a torsional pendulum—a wire with a dependent 
sphere. By the stimulus of a blow there is produced 
a torsional vibration—a response followed by recovery. 
The writing lever attached to the pendulum records 
