of Substances upon Voltaic Action, 445 



afternoons and evenings of 13 days, the position of the lead 

 with regard to the " A" and "B" electrodes being usually 

 reversed between the hours of 2 and 3 each day, and the 

 circuit was left open every night. 



In nearly all these cases the proximity of the lead to the 

 "A" electrodes was attended by an increase of the deflexion, 

 and to the " B " electrodes by a decrease ; and whilst the 

 average magnitude of deflexion in the former case was 21'7, 

 in the latter it was 13*3 ; in some cases with the " B " elec- 

 trodes the influence of the lead was sufficient to overcome 

 the previous current and slightly reverse the deflexion. These 

 results are consistent with the view that the proximity of 

 the lead to either series of electrodes increased its electro- 

 positive or decreased its electro-negative state, and they agree 

 with those obtained with the larger apparatus (see ante, p. 443). 

 In these experiments the usual period after reversal of position 

 of the electrodes in which the effect of the lead attained its 

 maximum was about 2\ hours. 



In some additional experiments 181 observations were made 

 during 12 forenoons, the circuit being left open all night and 

 closed each following morning. The average magnitude of 

 deflexion obtained with the "A" electrodes was 27*5, and 

 with the " B " ones 1*4. In some of these cases also the 

 influence of the lead was sufficient to reverse the deflexion. 

 It usually required about 2 J hours for the effect of the lead 

 to attain its maximum. These results agree with the imme- 

 diately preceding ones. 



2nd Series. — Influence of Mass of Lead, 8fc. 



With bars of lead about 1 inch wide and 1 inch thick sub- 

 stituted for the strips, and all the other conditions remaining 

 the same.— During the afternoons and evenings of a further 

 period of 9 days 57 observations were made, the periods of 

 reversal of position of the electrodes and of closing the circuit 

 being as above. 



In nearly every case the deflexions obtained in the presence 

 of the lead with the " A " electrodes were larger than those 

 obtained with the " B " ones, and whilst the average magni- 

 tude of those obtained with the u A " ones was 34*4, that with 

 " B " was 16*] ; i. e., the proximity of the lead increased the 

 positive condition of the "A ;; electrodes and decreased the 

 negative condition of the " B " ones, and the presence of the 

 larger mass of lead was attended by a greater amount of effect 

 upon the electromotive force. The usual period required to 

 attain a maximum after reversal was about two hours. 



In some additional experiments the circuit was closed as 

 Phil. Mag. S. 5. Vol. 43. No. 265. June 1897. 2 L 



