1824.] new Phenomenon of Electromagnet ism. 23 



experiments on electromagnetic rotation, I was induced to try 

 the action of a magnet on mercury connected in the electrical 

 circuit, hoping that, in this case, as there Avas no mechanical 

 suspension of the conductor, the appearances would be exhibited 

 in their most simple form; and I found that when two wires were 

 placed in a basin of mercury perpendicular to the surface, and 

 in the voltaic circuit of a battery Avith large plates ; and the pole 

 of a powerful magnet held either above or below the wires, the 

 mercury immediately began to revolve round the Avire as an axis, 

 according to the common circumstances of electromagnetic 

 rotation, and Avith a velocity exceedingly increased when the 

 opposite poles of two magnets Avere used, one above, the other 

 below. 



Masses of mercury of several inches in diameter were set in 

 motion, and made to revolve in this manner, whenever the pole 

 of the magnet Avas held near the perpendicular of the wire ; but 

 when the pole was held above the mercury between the two 

 wires, the circular motion ceased ; and currents took place in 

 the mercury in opposite directions, one to the right, and the 

 other to the left of the magnet. These circumstances, and 

 various others Avhich it would be tedious to detail, induced me 

 to believe that the passage of the electricity through the mer- 

 cury produced motions independent of the action of the magnet ; 

 and that the appearances Avhich I have described were owin°-to 

 a composition of forces. 



I endeavoured to ascertain the existence of these motions in 

 the mercury, by covering its surface Avith weak acids ; and dif- 

 fusing over it finely divided matter, such as the seeds of lycopo- 

 diuiu, Avhite oxide of mercury, &c. but Avithout any distinct 

 result. It then occurred to me, that from the position of the 

 Avires, currents, if they existed, must occur chiefly in the lower, 

 and not the upper surface of the mercury; and I consequently 

 inverted the form of the experiment. I had two copper wires, 

 of about one-sixth of an inch in diameter, the extremities of 

 which Avere flat and carefully polished, passed through two 

 holes three inches apart in the bottom of a glass basin, and per- 

 pendicular to it ; they were cemented into the basin, and made 

 non-conductors by sealing-wax, except at their polished ends ; 

 the basin Avas then filled with mercury, which stood about a 

 tenth or twelfth of an inch above the wires. The Avires were 

 now placed in a powerful voltaic circuit. The moment the con- 

 tacts Avere made, the phenomenon, which is the principal object 

 of this paper, occurred : the mercury was immediately seen in 

 violent agitation ; its surface became elevated into a small cone 

 above each of the wires ; Avaves flowed off' in all directions from 

 these cones ; and the only point of rest Avas apparently Avhere 

 they met in the centre of the mercury between the two wins. 

 On holding the pole of a powerful bar magnet at a considerable 

 distance (some inches) above one of the cones, its apex Avas 



