262 Mr. W. Sullivan oti Currents of Electricity produced by 



molecular motion than was generally supposed. In order to 

 test the accuracy of my views, I took a flat piece of board 

 about two feet long and morticed two uprights, each three 

 inches high, into it about eighteen inches apart. I then took 

 a piece of No. 15 brass wire and soldered it to a similar piece 

 of iron wire, and stretched it tight over the uprights so as to 

 produce, when set in vibration, a musical note; the ends of 

 this compound wire were then connected with an exceedingly 

 delicate galvanometer, similar to that used by Melloni in his 

 researches on radiant heat; when this was set in rapid vibra- 

 tion, a slight deviation of the needle took place, the direction 

 of the current being from the iron to the brass, as in a similar 

 thermo-electric circle; this was not, however, always the case, 

 but seemed to depend upon the kind of vibration, though I 

 could not discover how. That this effect did not depend on 

 any heat produced is quite certain, as the current ceased the 

 moment the vibration ceased. I could not always produce a 

 deviation, and very often, when there was a current produced, 

 it was scarcely appreciable until I increased the oscillation of 

 the galvanometer-needle by frequently breaking contact. On 

 one or two occasions I noticed a deviation equal to that pro- 

 duced by heating the junction of the two wires to dull redness. 

 From some of my experiments, it would appear that when the 

 wire vibrated continuously from end to end, the greatest effect 

 was obtained ; but when from some cause a nodal point was 

 produced in the centre of the wire, and the two halves of the 

 wire vibrated in opposite directions, no effect was produced. 

 This point indeed was the cause of all my difficulties, as I 

 found it almost impossible to detect when this took place. As 

 the amount of electricity developed by such an arrangement 

 as that just described must naturally be very small, I thought 

 it would be well to increase the masses set in vibration : for 

 this purpose I took a bar of antimony, five inches long, three- 

 eighths of an inch wide, and a quarter of an inch thick, and 

 soldered it to a similar bar of bismuth ; to the ends of this 

 compound bar copper wires were attached, which communi- 

 cated with a galvanometer. When this was set in vibration, 

 by striking it with a piece of iron, as a file, suspended from a 

 piece of string, results similar to the former were obtained : at 

 times considerable deviations were thus obtained, whilst very 

 often no deviation whatever could be observed ; the whole 

 effect seeming to depend on the manner in which the vibra- 

 tions are propagated along the wire. The results were on the 

 whole much more satisfactory with this arrangement than with 

 the former. I could also detect the nature of the vibrations 

 occurring in such a bar much better than with wires in the 



