184 Prof. J. C. Bose. [Apr. 18, 



then comparatively slow, the curve of recovery being thus convex to 

 the abscissa. 



6. Under rapidly succeeding stimuli, there is a fusion of individual 

 effects ; the curve rises to a maximum, when the force of restitution is 

 kept balanced by the distorting force. 



7. Sub-normal stimulus often produces a reverse effect. Too long- 

 continued disturbance produces, or tends to produce, a reversal. 



8. Under peculiar moleculiar modification, the response is of 

 opposite sign to the normal. Continued stimulation converts abnormal 

 to normal. The response curve may thus exhibit, at the beginning, 

 a negative twitch followed by the normal positive. 



A few curves are selected from experiments already described, and 

 given below, in order to illustrate graphically the remarkable simi- 

 larities of response to different kinds of stimulus. (See fig. 15.) 



They show how essentially similar are the molecular effects produced, 

 though the modes of stimulation and the methods used for the detec- 

 tion of effects produced are so different. 



10. Effect of Light Vibration balanced by Mechanical Vibration, 



I have hitherto spoken of the similarities of the radiation and 

 mechanical strains, but have not yet said anything about their mutual 

 relation. 



It is known that in cases where electric radiation produces an 

 increase of conductivity, mechanical vibration produces an opposite 

 effect, i.e., an increase of resistance. It thus appeared that we have 

 here an exhibition of two opposite molecular effects. No definite con- 

 clusion could be drawn from this, however, as the increase of resistance 

 may have been due to the mechanical separation of the conducting 

 particles. 



I then thought of trying the effects of light and mechanical vibration 

 in producing electromotive variation in a strain cell. For this purpose 

 I took a tin cell, and subjected one of the wires to the action of light 

 and mechanical vibration alternately. The upper curve of fig. 16 



t 



1 



"«4 



TiG. 16.— Effect of light and torsional vibration on a Tin cell. Light makes the 

 acted wire cuproid, torsional vibration makes it zincoid. 



