Page:On Electromotive Wave accompanying Mechanical Disturbance in Metals in Contact with Electrolyte.djvu/9

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 Na₂CO₃, the sensitiveness of A is at the beginning great, hence the resultant response is at the beginning positive or upward. Dilute solution of Na₂CO₃ is next applied to B. The response of B (down) begins earlier, and continues

Fig. 4.—Transformation from positive to negative through intermediate diphasic variation. Thick dots represent times of application of stimulus.

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 prominent, 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 vibration 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