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vacuum-tube withdrawn from its influence, the luminous discharge 

 was reproduced. 



To test whether a complete disruption of the electrical current 

 had taken place, two gold-leaf electroscopes were attached, one to the 

 zinc and the other to the copper terminal of the water-battery ; the 

 leaves diverged with considerable energy ; connection was then made 

 from the electroscopes to the wires of the vacuum-tube ; the luminous 

 discharge became visible, and the leaves of both electroscopes par- 

 tially collapsed ; the vacuum-tube was then placed as before, between 

 the armatures of the electro-magnet, and immediately the magnet 

 was excited, the luminous discharge disappeared, and the leaves of 

 the electroscopes diverged to their original maximum extent, thus 

 proving the disruption to be complete. 



If the smaller tube B is placed across both poles of the magnet, 

 the luminous discharge at its centre assumes the appearance of being 

 nearly separated into two parts, each part showing a tendency to 

 rotate round the pole of the magnet on which it is placed, the one 

 in an opposite direction to the other. I endeavoured to obtain a 

 disruption of the battery discharge when in this state, and possibly 

 with a more powerful electro-magnet this experiment would succeed ; 

 but although I reduced the intensity of the battery discharge and 

 increased the power of my electro-magnet, I could not in this manner 

 obtain an actual discontinuity of the battery discharge ; but when the 

 same vacuum-tube was placed in a longitudinal or equatorial position 

 between the poles, or even approached them within three or four 

 inches in that direction, an immediate interruption of the dis- 

 charge took place. 



When both vacuum-tubes are placed in the battery circuit, the 

 interruption can be shown in a very striking manner : the general 

 arrangement of the apparatus represented in the figure shows how 

 this experiment is. made. A is fixed on a wooden support. One 

 wire (5) is attached to the copper terminal of the battery, the other 

 wire () being connected to one of the wires in B, which is held by 

 the hand, the other wire (') being connected with the zinc terminal 

 of the battery, gold-leaf electroscopes being placed as before. In 

 this manner all the apparatus is fixed except B, which being held by 

 the hand, and the connecting wires being flexible, can be placed in 

 any required position. 



