Page:Collected Physical Papers.djvu/223

positive or negative responses, the acted wire becoming on different occasions either Z or C.

Fig. 46.

A. Effect of stimulus of short duration.

(a) Effect of electric radiation on Ag′ (conductivity variation).
(b)⁠„⁠light on HgBr (E.M. variation).

(c)⁠„⁠mechanical vibration on Tin (E.M. variation).

B. Effect of continued action of stimulus.

(d) Effect of continued action of electric radiation on Ag′ (conductivity variation).
(e)⁠„⁠„⁠„⁠mechanical vibration on Tin (E.M. variation).
(f)⁠„⁠„⁠„⁠light on AgBr E.M. variation).

(g)⁠„⁠„⁠„⁠mechanical vibration on Nickel (E.M. variation).

8. Reversal Effects

Reversed Effect due to Sub-minimal Stimulus.—Just like the negative effect (i.e., opposite to the normal) often exhibited under electric radiation when the stimulus is below the critical intensity, so also feeble mechanical stimulus often produces an effect opposite to the normal. Thus with strain cell made of lead,