1824.] Conductors when transmitting the Electric Current. 171 



force so long as the pile remains in activity, and only flags, 

 and at length ceases, when ils energy is quite exhausted. The 

 mercury is not sensibly tarnished or otherwise acted on, and, 

 after the experiment, is found to have undergone no change ; 

 nor is the acid sensibly altered, with the exception of the trifling 

 portion decomposed, and a minute quantity of mercury taken up. 



4. If we examine the phenomena more attentively, we shall 

 observe that the particles of the acid in immediate contact with 

 the mercury, are those which move most actively, being darted 

 along its surface with surprising violence ; those above them, 

 and more remote, appearing rather to be dragged or forced along 

 by them, than impelled by any force acting directly on them- 

 selves. We shall perceive too, that, if some distance intervene 

 between the wires and the edges of the mercury, the current 

 will be confined, and the circulation take place in the immediate 

 neighbourhood of the mercury only, the liquid around the wires 

 being nearly, or quite at rest. 



5. If the centre of the globule or disc of mercury be situated 

 in one straight line with the extremities of the wires, the current 

 will set diametrically across it ; but if this be not the case, it 

 will follow a curvilinear course, every elementary filament of it 

 having a different curvature, and each traversing the mercury 

 in a path having a common origin and termination, viz. the 

 points (z) and (c) of its surface nearest to the negative and posi- 

 tive poles respectively. 



6. If the globule of mercury be of considerable size (four 

 hundred or five hundred grains for instance), it will be observed 

 to elongate itself in the direction of its axis towards the negative 

 wire, and if near enough, will reach and amalgamate with it : 

 but if it be small, its whole mass will move bodily with more or 

 less rapidity, as if attracted to the negative wire. This appa- 

 rent attraction is often very energetic, the globule moving with 

 great velocity towards the negative wire, to which it imme- 

 diately adheres. If the wires form a triangle with the situation 

 of the globule while at rest, the latter advances neither directly 

 to the negative, nor directly from the positive wire, but in a 

 direction oblique to both, approaching the negative wire in a 

 spiral, and describing frequently several revolutions with in- 

 creasing velocity before it ultimately falls into and amalgamates 

 with it, like a body acted on at once by an attractive force tend- 

 ing to the negative, and a repulsive, from the positive wire. 



7. These apparent attractions and repulsions, this elongation 

 of large masses of mercury and bodily motion of small ones 

 toward the negative pole, are in reality, however, only secon- 

 dary effects ; their immediate cause, as well as that of the 

 cuii cuts in the surrounding acid, will be discovered by a more 

 minute attention to what takes place in the mercury itself, while 

 under the influence of the electric action. 



