336 BELL SYSTEM TECHNICAL JOURNAL 



carbon, no sound could be heard. Those small electromotive forces 

 which must have resulted from the motion of any of the specimens in 

 the earth's magnetic field were totally inappreciable with the apparatus 

 employed. 



Now the appearance of a potential difference between the two ends 

 of a wire consequent to its vibration necessarily must have implied one 

 of two situations — either there was some external influence or some 

 relation to its surroundings which was capable of discriminating be- 

 tween the two ends, or else the wire possessed inherently some property 

 that differentiated between the two directions along its length. Ac- 

 cordingly, exhaustive efforts were made to learn if orientation had 

 any influence on the phenomenon. A stretched soft iron wire about 

 three feet long yielding a clear sound in the speaker upon being 

 plucked was employed. First, the ends of the wire were held station- 

 ary, and the wire was plucked time and again so that its plane of 

 vibration covered representatively the various inclinations possible 

 for this. Then there was tried a large number of positions for the 

 axis of the wire, spread uniformly over the complete sphere. No 

 response to orientation could be found. This negative result meant 

 that the phenomenon under investigation must have arisen funda- 

 mentally through some condition of polarity resident within the 

 specimen.^ 



With the phenomenon associated so definitely with the ferro- 

 magnetic property of the substance, and attributable so certainly to 

 some quality of polarity of the specimen, it was but natural to recall - 

 the considerable changes in their states of magnetization which ac- 

 company the applications of stresses with ferro-magnetic materials. 

 In order to have produced an electromotive force along the axis, the 

 state of magnetization of a rod or wire would have had to change in 

 that same sense in which magnetization would have been acquired 

 when an electromotive force was applied, and current allowed to flow, 

 between its two ends; i.e., magnetization in closed circular paths 

 centered upon the axis and at right angles thereto. Having formed 

 this reasonable hypothesis of the fundamental process, experiment 

 then was carried along the lines of testing its validity. 



Any circular magnetization of the wires and rods, since its circuit 

 would have been along paths of low reluctance wholly within the 

 material, should have been comparatively stable and free from dis- 

 turbance by external magnetic fields of moderate intensity. The 

 observed fact that the phenomenon was quite independent of the 

 orientation of the specimen in the earth's magnetic field was consistent 

 with this view. The further fact that the imposition of a strong 



