of Snl) stances upon Voltaic Action. 447 



that the larger the total resistance in the circuit, the longer 

 was the period of time required for the lead to produce its 

 full effect. 



General Influence of Time. 



In all the experiments of these three series, a short period of 

 time elapsed before any effect of the proximity of the lead 

 upon the deflexion was manifest ; in some cases it was distinct 

 in less than five minutes, whilst in others it was not observable 

 in less than a quarter of an hour. (N.B. In later experi- 

 ments with apparatus " No. 3 " offering very much less 

 resistance, the visible effect commenced at once.) As the 

 delay could not be attributed to any other cause, and as in 

 all cases the maximum effect with the total amount of re- 

 sistance in the circuit was usually only attained in about two 

 hours, I conclude that a state of strain of the superficial 

 molecules of the electrodes and lead bars was probably pro- 

 duced, and required that period of time to be completely 

 overcome. 



Both with the lead bars and with the plates, by leaving the 

 circuit open all night (equal to about 15 hours), with the 

 electrodes in proximity to the bars, the effects of the lead had 

 disappeared, and it required about two hours to entirely 

 recover after the circuit had again been closed through the 

 galvanometer. As the bars produced a much larger maximum 

 effect than the thin plates (see ante, p. 444) , and produced it 

 in about the same period of time, viz. two hours, they must 

 have produced it at a much faster rate. 



Effect of Short-circuiting the Apparatus. 



As the maximum effect of the lead was more quickly 

 attained the smaller the total amount of resistance in the 

 circuit, the effect of short-circuiting the pile alone whilst the 

 electrodes were under the influence of the lead was tried. In 

 four separate experiments, by short-circuiting the apparatus, 

 with an external resistance of only 60 ohms and no gal- 

 vanometer in the circuit, during ten minutes, and then at 

 once including the galvanometer, the maximum effect was 

 attained in about 25 minutes ; this result indicated that the 

 retardation was largely due to the total resistance. 



Influence of Temperature, §c. 



A few experiments were made with the same apparatus to 

 examine this. A strip of lead 16 J inches long, 1 inch wide, 

 and J inch thick was uniformly heated throughout to a 



2L2 



