164 Mr. Herschel on certain motions produced in 
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 di- 
rectly on themselves. 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 termina- 
tion, viz. the points (%) and (c) of its surface nearest to the 
negative and positive poles respectively. 
6. If the globule of mercury be of considerable size (four 
hundred or five hundred grains for instance ) , it will be ob- 
served to elongate itself in the direction of its axis towards 
the negative wire, and if near enough, will reach and amal- 
gamate with it : but if it be small, its whole mass will move 
bodily with more or less rapidity, as if attracted to the ne- 
gative wire. This apparent attraction is often very energetic, 
the globule moving with great velocity towards the negative 
wire, to which it immediately 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, ap- 
proaching the negative wire in a spiral, and describing fre- 
quently several revolutions with increasing velocity before it 
