CHAPTER IV. 

 INDUCTION. 



IT is noticeable that in all our experiments thus far 

 the electrified body acts on the other bodies before there 

 is any actual contact. The knife-handle attracts the 

 spoon ; the sealing-wax, ebonite, or glass attracts the 

 balanced rod or the pith ball while separated from them. 

 And when either of these electrified bodies approaches 

 the gold-leaf electroscope, there is first a divergence of 

 the leaves before contact occurs. 



It will also be noticed that this effect increases or 

 diminishes as the distance is increased or diminished. 

 And, further, that while the interposition of different 

 substances, as glass, paraffin, ebonite, air, wood, metal, 

 produce great variations in the effect, none of them 

 wholly prevent it. 



There is evidently, then, an invisible influence ex- 

 tending to a certain distance from the electrified body 

 in every direction, and affecting everything within its 

 sphere, and this effect is called induction. 



When an electrified body is brought near the disc of 

 the electroscope without touching it, the leaves diverge, 

 and on its removal converge again, showing no perma- 

 nent effect. But if it is allowed to touch the disc, the 

 leaves are electrified, and remain divergent after its 

 removal. 



But if, instead of touching the disc, it be held near 



