1902.] accompanying Mechanical Disturbance in Metals. 293 



on carefully applying just the proper amount, I find that the stimulus 

 evokes a responsive electric variation which is less than the normal, 

 and the period of recovery is very much prolonged from the normal 

 1 minute before to 5 minutes after the application of the reagent 

 (fig. 13 (a)). In the next record (fig. 13 (&)) the arrest is more pro- 

 nounced, i.e., there is now no recovery. Note also that the maximum 

 is attained much later. Stimuli applied after the arrest produce no 

 effect, as if the molecular mechanism became locked up. 



RisumL 



1. Molecular disturbance produced by mechanical stimulus gives rise 

 to an electrical disturbance. In the majority of cases, under normal 

 conditions, the responsive electrical current in a wire is from the less 

 to the more disturbed. 



2. Eesponse may be obtained by (1) method of block, (2) by 

 methods of negative or positive variation. 



3. The electromotive variation disappears on the cessation of dis- 

 turbance. 



4. The intensity of the electrical variation produced by a given 

 disturbance is modified by the molecular condition of the wire. 

 Annealing, or previous continued vibration, enhances the electric 

 effect. 



5. The abnormal response due to molecular modification is trans- 

 formed into normal by continued vibration. 



6. The intensity of electromotive variation is increased with increas- 

 ing intensity of stimulation. 



7. In a curve — the ordinates representing the electrical effects, and 

 the abscissae the amplitudes of vibration — the first part is slightly 

 convex to the abscissa, the second is approximately straight, and the 

 third concave. With increasing stimulation there is a tendency for the 

 electrical variation to reach a limit. 



8. A maximum electrical effect is produced by continuous vibration, 

 which is definite for a given amplitude of vibration. A curve showing 

 the relation between the maximum effect and the amplitude of vibra- 

 tion exhibits the same characteristics as in the last case. 



9. Hysteresis is exhibited in cyclic curves. The forward and return 

 curves tend to coincide after several cycles. Previous annealing 

 reduces hysteresis, and after one or two cycles the wire assumes a con- 

 stant condition of sensibility. 



10. Chemical reagents may profoundly modify the electric excita- 

 bility. Some increase the excitability. Others depress or even abolish 

 the excitability. The after-effects are sometimes very persistent. 



11. The effect of weak solution is sometimes the opposite to that of 

 strong solution. 



