508 Prof. S. P. Thompson on the Action of 



These experiments have moreover demonstrated that the 

 convection of a quantity of electricity by a flight of electri- 

 fied molecules is, electromagnetically, the same thing as the 

 conduction of the same amount of electricity by a conductor — 

 these flights of electrified molecules, which usually take place 

 in straight lines normally to the surface of the negative pole 

 of the exhausted tube, taking curved paths under the influ- 

 ence of a magnetic field. 



VI. Systems of Conductors of which a Liquid Vein forms a 

 Part. — The present author has experimented on the action of 

 magnets upon liquid veins traversed by currents, and has 

 observed the following phenomena : — 



A liquid vein traversed by a current obeys a similar law of 

 displacement to that obeyed by a movable wire conductor 

 under the same circumstances. A horse-shoe electromagnet 

 was placed with its poles horizontal ; and a vein of dilute sul- 

 phuric acid was made to flow vertically downwards from a 

 reservoir above into a vessel below; and a current from a 

 small Grove's battery was made to traverse the vein. When 

 the circuit of the electromagnet was closed the vein was drawn 

 aside, being attracted towards or repelled from between the 

 poles of the electromagnet, according to the sense of the cur- 

 rent and the direction of the magnetization, just as in the 

 well-known apparatus of Marsh*. 



When a vein of mercury was substituted for one of dilute 

 acid, these attractions and repulsions became much more 

 marked. It was also curious to observe that the vein, instead 

 of falling simply obliquely, fell in a path which curved more 

 and more away from the perpendicular (fig. 1, Plate XIV.). 

 The author did not succeed in imparting a double curvature 

 to the vein. 



When a liquid vein carrying a current flows near the pole 

 of a bar electromagnet whose axis is placed vertically, the vein 

 is bent aside, the flexure being such as to tend to bring the 

 vein into parallelism with the hypothetical Amperian currents 

 (fig. 2, Plate XIV.). If the vein falls against the magnet- 

 pole or into an annular trough surrounding the pole, a motion 

 of reaction is set up between the vein and that against which 

 it falls, tending to make it rotate about the magnet-pole in a 

 sense opposed to that of the Amperian currents, precisely as 

 the voltaic arc observed by Walker, and the luminous dis- 

 charge in a partial vacuum by De la Rive. 



When a liquid vein carrying a current falls exactly upon 

 the pointed pole of a powerful magnet placed vertically below 

 it, instead of being subjected to a rotatory displacement around 

 * Noad, op. cit. p. G65. 



