Electric Currents by Sulphur Cells. 331 



(6) The last-mentioned cell was taken to pieces and remade 

 after the addition of about an equal part of sublimed sulphur 

 to the mixture of sulphur and sulphide. Its resistance was 

 now found to be many megohms, yet it produced a larger 

 galvanometer-deflection than before. 



(7.) Once more the cell was taken to pieces and a little 

 more sulphide added. When remade, its resistance was at 

 first about 2700 ohms ; but it varied considerably. It pro- 

 duced a galvanometer-deflection of about 100 divisions, which 

 in a few minutes increased in a somewhat irregular manner 

 to 250 divisions. It was then disconnected from the galva- 

 nometer, and, when again connected after an interval of six 

 hours, it deflected the spot of light off the scale. Shunting the 

 galvanometer (the resistance of which was 3483 ohms) with 

 a coil of 300 ohms, the deflection amounted to 130 divisions; 

 and on the following day with the same shunt, the deflection 

 was at first about 250 divisions, rapidly diminishing, however, 

 when the circuit was closed. 



(8) A cell was made by compressing precipitated silver 

 sulphide unmixed with any free sulphur between plates of 

 silver and copper. When connected with the galvanometer, 

 this cell produced a deflection which, with a shunt of 35 ohms, 

 exceeded 400 divisions. But in this case the silver was the 

 negative plate, the direction of the current being from copper 

 through sulphide to silver. The B.M.F. was less than that of 

 the cell described in (2). 



(9) Another cell was made in the same manner as that 

 described in (2); but the sulphur was mixed with sulphide 

 of silver instead of sulphide of copper. This gave a strong 

 current in the same direction as that produced when sulphide 

 of copper was used, and opposite to that generated by the cell 

 containing silver sulphide without free sulphur. 



(10) Pure sulphur was melted on a clean plate of copper, 

 and, when just liquid, a warmed plate of silver was laid upon 

 it and pressed down with a weight until cold. This cell gave 

 a strong current from silver through sulphur to copper. 

 Sulphides were of course formed during the process of 

 construction. 



(11) A melted mixture of sulphur and silver sulphide was 

 spread upon a copper plate, and a plate of silver pressed upon 

 it. When cold, the silver plate was split off with a knife, and a 

 piece of silver-leaf, sufficiently thin to appear blue by trans- 

 mitted light, was attached (by rubbing) to the exposed surface 

 of the mixture. As before, there was a comparatively strong 

 current from the silver to the copper. The silvered surface 

 was then exposed to the light of burning magnesium wire, and 



