ELECTRICAL EXPERIMENTS 57 



the oil-drop, placed in the middle between the electrodes. 

 Shortly before the apex of the blue region reached the 

 margin of the drop, the first trace of the system of extension- 

 currents made itself noticeable at the edge of the drop. 

 After this negatively directed extension-current had lasted a 

 short period, a condition of rest followed for some time, the 

 same phenomenon which has already been mentioned above, 

 and which was also as a rule observed under similar con- 

 ditions in drops of foam, investigated in glycerine. The cause 

 of this transitory quiescent state was equally intelligible 

 under the arrangement of the experiment that was chosen. 

 For during the streaming of the drop the red acid fluid of 

 the positive side spread itself out in a peculiar manner com- 

 pletely round the drop, so that the latter was now surrounded 

 on the negative side as well by a narrow red zone, and the 

 blue triangle had entirely altered its form. In consequence 

 the cause of the negative streaming was removed, and it 

 died down. After a short time the blue zone approached 

 the drop again, and now called forth persistent negative 

 streaming movements, which, after interruption of the electric 

 current, became immediately weak, and soon died away. 

 The phenomenon described can be reversed at will by reversal 

 of the poles. The length of time involved up to the setting 

 in of the persistent negative current was, with electrodes 

 3 mm. apart, about five minutes. 



If, moreover, one takes into consideration the fact that 

 with a slight acidulation of the glycerine by means of HC1, 

 and the use of non-polarisable brush electrodes, a negative 

 current could not be obtained, it is certainly a legitimate 

 conclusion, if all these considerations are taken together, 

 that the earlier described negative streaming of the 

 drops of foam depended solely on the electrolytic action ' 

 of alkali. 



In further experiments on drops of foam, using pla- 

 tinum electrodes, it was soon proved, on the other hand, 

 that, in opposition to an earlier idea, immediately after 

 closing the current a moderately strong centre of extension- 

 currents made its appearance at the positive margin of the 

 drop ; this fact was ascertained just as plainly and fre- 



