Electric Currents by Sulphur Cells. 335 



Summary. 



Plates of silver and copper imbedded in a mixture of sulphur 

 with sulphides of copper or silver constitute a cell which at 

 the ordinary temperature is capable of generating and main- 

 taining a constant current, the silver being the positive 

 element. Such a cell, in which the mixture consisted of 5 

 parts of sulphur w r ith one of copper sulphide between plates 

 3 centim. square and *3 millim. apart, had an E.M.F. of *0712 

 volt and an internal resistance of 6537 ohms. 



If the proportion of copper sulphide to sulphur is increased, 

 the internal resistance of the cell is diminished ; but its E.M.F. 

 is also diminished. 



A cell containing copper sulphide unmixed with free sul- 

 phur fails to produce any appreciable current. 



A cell containing silver sulphide only generates a current 

 in the opposite direction to that produced when the sulphide 

 is mixed with free sulphur. 



Copper used in conjunction with iron or gold gives no 

 current whatever at the ordinary temperature. 



The current generated by a silver-copper cell containing 

 free sulphur mixed with sulphide is diminished by the action 

 of light and increased by heat. It has not been ascertained 

 whether the effect is upon the E.M.F. or the internal resist- 

 ance, or both. 



If a battery-current is caused to pass for a short time through 

 a cell consisting of two silver electrodes imbedded in a mixture 

 of sulphur and copper sulphide, the cell, after being discon- 

 nected from the battery, will generate a current of very short 

 duration in the direction opposite to that of the battery-current, 

 followed by a current which may be maintained for several 

 hours in the same direction as the battery-current. A second 

 reversal has in one case been found to occur after an interval 

 of four hours. 



The experiments, of which an account is here given, must 

 be considered as being merely of a preliminary nature. A 

 complete investigation of the phenomena in question would 

 require more time than I am at present able to devote to the 

 subject. 



Addition, August 3rd. 



From (4), (5), and (6) it appears that a cell consisting of 

 copper and silver plates is incapable of generating a current 

 unless a certain proportion of free sulphur is mixed with the 

 sulphide. Thinking that the function of the free sulphur 



