IV. Electric currents returning on their own path. 



When only one of the wires of Ruhmkorff's apparatus is in contact 

 with one of the electrodes of a long and large exhausted tube, while 

 the second wire is isolated, or, what is preferable, communicates with 

 the earth, an electric current is obtained entering the tube and re- 

 turning on its own path. The existence of the two currents is most 

 evidently proved by the magnet, which, acting differently on both, 

 divides the double current into two of the same intensity. This 

 intensity is much increased by touching the tube with the hand at 

 any distance from the electrode which communicates with Ruhm- 

 korff's apparatus. 



A double current of exactly the same description is obtained in a 

 narrow tube, which may be one foot long, communicating with a 

 larger tube, both electrodes of which are connected with the wires of 

 Ruhmkorff's apparatus. When the extremity of the narrow tube is 

 touched with the hand, a current starting from the principal tube 

 enters the narrow one, proceeds to its extremity, and finally returns 

 to the principal tube : which is proved by the magnet. 



When, through a tube whose shape is represented by the drawing, 



the discharge was sent from A to B, the current, passing from the 

 narrow tube into the surrounding larger one, was, when it arrived at 

 the extremity of the narrow tube, partly branched off in an oppo- 

 site direction towards A, and then, changing its course again, moved 

 towards B. 



There is another case where returning currents are obtained. 

 When the discharge on its way through a highly exhausted tube 

 passes from a large space into a narrow channel, a part of the current 

 is reflected, and returns on its own path within the larger space : 

 which is again proved by the magnet. 



Mr. Gassiot first observed and described what he calls "recipro- 

 cating currents," and the separation of such currents by the magnet. 

 That celebrated philosopher had the kindness himself to show me his 

 experiment, and even enabled me to repeat it, by obliging me with 

 one of his fine Torricellian-vacuum tubes. I do not exactly know his 



