1901.] 



between Radiation and Mechanical Strains* 



177 



If the conductivity variation under the stimulus of electric radiation 

 and the electromotive variation under mechanical stimulus are but 

 expressions of some molecular effect, we may expect the peculiarity of 

 one kind of response reflected in the other. "We shall presently see 

 how closely the normal effects in the two classes resemble each other. 

 Still more extraordinary are the similarities that exist even in abnor- 

 malities, several instances of which will be given later. I shall men- 







































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V 





























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Time. 



Fig. 12. — E.M. variation due to torsion of zinc wire. Successive dots in the 

 ascending portion of the curve represent effect of rotation through 360°. 

 The descending curve represents recovery. 



tion here only one case. We have seen in experiments with electric 

 radiation that substances sometimes fall into a sluggish molecular 

 condition, when the responses almost disappear. Strong stimulation 

 (induction shocks, &c.) or annealing is found to restore the sensitive- 

 ness. The same peculiarity is observed in the strain-cell. Lead, for 

 example, specially on cold days, is apt to fall into a sluggish condi- 

 tion, when it becomes almost irresponsive. But it regains its sensi- 

 tiveness after intense vibration or annealing. 



All metals (including the noble metal Pt) when molecularly dis- 

 turbed exhibit electromotive effect. The intensity of electromotive 

 variation depends on the nature and physical condition of the sub- 

 stance. The intensity of effect does not, however, depend on the 

 chemical activity of the substance, for the electromotive variation in 

 the relatively inactive tin is greater than that of zinc. The electro- 

 lyte used in the following experiments is common tap-water, but 

 similar effects are also obtained with distilled water. 



