1902.] accompanying Mechanical Disturbance in Metals. 281 



vals of one minute by means of a torsion head at the other end. (See 

 fig. 2.) Owing to after effects of previous applications of Na 2 C0 3 , the 

 sensitiveness of A is at the beginning great, hence the resultant response 

 is at the beginning positive or upward. Dilute solution of Na 2 C0 3 is 

 next applied to B. The response of B (down) begins earlier, and con- 







Fig. 4. — Transformation from positive to negative through intermediate diphasic- 

 variation. Thick dots represent times of application of stimulus. 



tinues to grow stronger and stronger. Hence, after this application,, 

 the response shows a preliminary negative twitch of B followed by 

 positive variation Of A. The negative grows continuously. At the- 

 fifth response, the two phases, negative and positive, of the double 

 response become equal ; after that, the negative becomes very promi- 

 nent, the positive dwindling into a feeble after vibration. 



Modification of the Apparatus into " Cell Form." 



The series in fig. 5 explains the transformation from the " straight 

 wire " to " cell " form. The wires A and B, cut from the same piece, 

 are clamped separately below ; vibration of A (the amplitude of which- 

 is measured by a graduated circle) gives rise to a responsive current in 

 one direction, vibration of B gives rise to a current in an opposite 

 direction. Every experiment may thus be verified by corroborative 

 and reversal effects. The electromotive effect varies with the substance, 

 and is sometimes considerable, for example, with " tin," a single vibra- 

 tion may give rise to as high a value as 0'4 volt or more. The 

 intensity of response does not depend on the chemical activity of the 

 substance, for the electromotive variation in the relatively inactive tin 

 is greater than in zinc. Again, the sign of response, positive or 



