46 ELEMENTS OF STATIC ELECTRICITY. 



showing that the difference of potential was created and 

 existed during the earth connection. 



This point has an important bearing on phenomena to 

 be considered hereafter, in regard to which prominent 

 writers have been betrayed into serious mistakes from 

 having overlooked it. 



INFLUENCE OF DISTANCE. It is important to notice, 

 that when the electroscope has been charged by induc- 

 tion in this manner, and the electrified body is again 

 brought near, the leaves continue to converge as the 

 body approaches, and come together when it is in the 

 same position as when the disc was touched with the 

 finger. A nearer approach produces divergence, which 

 increases as the body is brought still nearer. 



Let it now be gradually withdrawn, and the leaves 

 gradually converge and come together, when the body 

 reaches the same point, as before. Further withdrawal 

 produces divergence, which continues to increase, and 

 reaches its limit when the body is wholly removed. 



If the electroscope be placed at various points, equally 

 distant from the electrified body, the effect of induction 

 will be the same, so long as the same distance from the 

 earth and surrounding objects is maintained. Hence 

 it is evident that electric energy, like other forms of 

 radiant energy, as light and heat, radiates equally 

 in all directions when not interfered with by other 

 influences. 



Suppose the electrified body to be a small globe, 

 entirely removed from the earth, and surrounded with 

 a perfectly homogeneous medium, it would be the 

 center of a sphere of inductive influence. And suppose 

 the lines of force radiating from it to be cut by the 

 surfaces of two imaginary concentric spheres of differ- 



