Phenomenon of Motion. 537 



distinguished from similar phenomena which are produced by 

 voltaic currents in liquids, and especially from the motion of 

 mercury in reference to which P. Erman made a communication 

 to our Acadeuiy as long ago as 1808*, and also from those 

 which Professor Quincke accurately examined in 1861. 

 think it probable, however, that the phenomenon I have ex 

 amined depends essentially on the same principle as that inves- 

 tigated by the last-named physicist ; and I am not at all reluc- 

 tant to adopt, at all events for the present, the theory he has 

 propounded. 



According to this theory, before any motion of the enclosed 

 substance, it becomes electrified by contact with what is next to 

 it; and the current acts on the substance thus electrified, car- 

 rying it to the positive or negative pole according as the prece- 

 ding electricity was negative or positive. 



By contact with glass, mercury becomes negative, and was 

 so in fact in the tube mentioned as having acted so well. 

 Hence there was nothing enigmatical in its transference to the 

 positive pole. If this view be correct, the conclusion seems ad- 

 missible that the transfer of mercury may occur in any quantity. 

 I must, however, remark that in some of the tubes the mercury 

 had a positive reaction, even before I had been able to observe 

 a corresponding motion towards the negative pole. It may be 

 that it was negative during the current. 



* This phenomenon, which differs from ours in that the motion of the 

 mercury is reversed (that is, from the positive to the negative pole) has 

 been recently described by M. Daniel as new (Phil. Mag. vol. xxxiii. p. 482), 

 whereas he can only claim to have first produced it by the current of the 

 induction-coil and of the magneto-electrical machine, by which he states it 

 is more easily produced than by the voltaic current. I have repeated part of 

 his experiments, and have found that with the induction-current the motion 

 of the mercury towards the negative pole is unaltered, whether spring-water 

 or water mixed with a small quantity of alkali or of acid be used as a con- 

 ducting liquid. I observed at the same time that particles which had de- 

 tached themselves from the oxide formed at the anterior end of the mer- 

 curial column, moved on the surface of the mercury in the opposite direc- 

 tion, apparently towards the positive pole, but really towards the posterior 

 end of the column, which must of necessity be negative. By separate 

 openings and closings of the circuit I found that the opening current exerts 

 a stronger action than the current on closing — which explains why, when a 

 mechanical make and break is used even without introducing a layer of air, 

 the motion of the mercury ensues in the direction mentioned. If only the 

 current on opening be used, at each impulse a wave is seen proceeding on 

 the surface of the mercury from the positive to the negative pole, which 

 has just the appearance of the column being pushed from behind, whereas 

 in the phenomenon in the exhausted tube the mercury appears as if at- 

 tracted in front. By the current of the electrical machine, both Holtz's 

 and the ordinary one, I did not succeed in producing any motion of mer- 

 cury in liquids. 



Phil. Mag. S. 4. No. 233. Suppl Vol. 34. 2 N 



