the Vibration of Wires and Metallic Rods. 263 



beautiful manner pointed out by Strehlke*, that is, by cover- 

 ing small drops of water with lycopodium, and placing these 

 globules on the bar, when the directions of the vibrations will 

 be shown by the motion of the particles of lycopodium. 



I could obtain no satisfactory results in my attempts to in- 

 crease the deviation of the galvanometer-needle produced by 

 a current flowing along a conducting wire by setting the latter 

 vibrating, as was naturally to be expected from the nature of 

 the current produced. In some cases the deviation was ma- 

 terially increased, whilst in others it appeared to be very much 

 diminished. It is unnecessary for me to say, that whenever a 

 current was observed to be produced in the vibrating wire, 

 it acted on the magnetic needle as all conductors under si- 

 milar circumstances. Indeed, there must be some intimate 

 connection between magnetism and vibration, from the fact 

 that if a bar o{ steel be struck with a hammer, so as to occa- 

 sion a ringing sound, the bar will become magnetic; whilst if 

 struck with anything soft, the effect so produced is very tri- 

 fling ; and also when a magnet is allowed to fall on any hard 

 body which causes it to vibrate rapidly, it will be much more 

 injured than if no such vibration be produced. 



I do not think two metals necessary for the production of 

 electricity by vibration ; for when I tried the effects of vibra- 

 tion on a bar composed of crystalline hard iron and soft fibrous 

 iron, I obtained results which certainly lead me to think that 

 the arrangement of the particles has much more to do with the 

 matter than their nature. Such an arrangement certainly 

 gives decisive thermo-electric effects, as does also a wire com- 

 posed of crystalline copper and fibrous copper. The subject 

 however is not decided, as it would require much more deli- 

 cate apparatus than I at present possess. 



Just as I was about to publish these results, I read an ac- 

 count of the experiments of Ermann, which were communi 

 cated to the last meeting of the British Association, from which 

 he obtained some very beautiful results so closely connected 

 with my own that 1 was induced to repeat all my experiments 

 again ; but my results did not differ from those which I ob- 

 tained at first, although the galvanometer which I used on the 

 second occasion was not very sensible, at least for such pur- 

 poses. One of Ermann's results certainly coincides in a very 

 remarkable manner with mine, namely, " that the tribo-ther- 

 mical effect is instantaneous, and that the deviation vanishes 

 quite as instantaneously as it commenced ; the return of the 

 needle to its primitive station being one of the most striking 

 features of the phaenomena." To these facts he adds, that the 

 * Poggendorflf's Annal.y vol. xl. p. 146. 



