356 



WRITINGS OF JOSEPH HENRY. 



[1855- 



made to diverge, to converge, and diverge again, by simply- 

 changing its elevation. 



Fig. 18. 



Fig 18 is intended to illustrate the condition of the elec- 

 troscope in the three positions in which it is supposed to be 

 supported on three metallic conductors of different heights. 

 The electroscope brought into neutral condition by the ball 

 is shown in the middle of the figure at B, in which the con- 

 nection of the rod with the ball is indicated by the dotted line. 

 When the electroscope is raised by the hand to a higher ele- 

 vation its condition is exhibited by C, in which the greater 

 height of the rod causes a greater amount of electricity to be 

 drawn down, and the top of the rod and the bottom of the 

 electroscope in connection with it to become more intensely 

 negative, and hence to draw down into the leaves a portion of 

 the natural electricity of the ball, and cause the former to di- 

 verge with positive excitement relative to the air around. 



The condition of the electroscope when brought to a lower 

 level is illustrated by A, in which the shortening of the con- 

 ductor reduces the number of atoms on which the electricity 

 of the earth acts, and hence those at the top are more pressed 

 upward by their self-repuision than in the former case, con- 



