Electric Currents by Sulphur Cells. 333 



battery was also placed in the circuit. Sulphide of copper 

 was of course formed by the action of the hot sulphur upon 

 the copper. 



(15) A melted mixture of 5 parts of sulphur with 1 part of 

 copper sulphide was pressed between plates of silver and iron, 

 and cooled. When first made, this cell generated a sufficiently 

 strong current to deflect the galvanometer-needle as far as 

 the stop would allow; but two hours later, when an attempt 

 was made to measure the E.M.F., it was found to have almost 

 completely disappeared, being less than a hundredth of that 

 of the cell described in (2). The E.M.F. was temporarily 

 restored by connecting the iron and silver plates with the 

 positive and negative terminals of a battery of ten Leclanche 

 cells for a few minutes. The result was of course merely a 

 polarization-current. 



(16) Two silver wires A, B were imbedded in a fused mass 

 consisting of equal parts of sulphur and copper sulphide. 

 When cold, the wire A was connected with the carbon pole 

 of a battery of ten Leclanche cells, and the wire B with the 

 zinc pole. After the current had passed for about a second, 

 the cell was detached from the battery and connected with 

 the galvanometer. A current was at once indicated in the 

 direction A B, i. e. in the same direction as that of the battery- 

 current which had been caused to pass through the cell. This 

 experiment was repeated many times and on different days, 

 with the same result*. A period of some seconds necessarily 

 elapsed between the separation of the cell from the battery 

 and its attachment to the galvanometer. In order to render 

 this interval as short as possible, the apparatus was so arranged 

 that by depressing a key the transfer could be effected in a 

 small fraction of a second. It was then found that the first 

 effect of the transfer was a strong momentary current in the 

 direction B A, which was immediately followed by the more 

 permanent current previously observed in the direction A B. 

 With the view of retarding the first effect, a battery of 

 two Leclanche cells was used, and the connection was made 

 for a longer period. After the battery had been connected 

 for one minute, the cell was transferred to the galvanometer 

 by means of the key, and the swing of ihe spot of light through 

 280 scale-divisions again indicated a current in the direc- 

 tion B A. Though this was not, as before, a current of only 

 momentary duration, it rapidly decreased in strength, becoming 

 zero in almost exactly 30 seconds. After zero was passed, a 

 current was at once set up in the opposite direction A B, which 



* The experiments described in the remainder of this paragraph were 

 made after the paper was read. 



