88 



ELEMENTS OF STATIC ELECTRICITY. 



The substance to be operated on is placed in the 

 receptacle on the tablet, the inner terminals of the 

 sliding rods adjusted on opposite sides of it, and the 

 outer terminal of one rod connected with the outer 

 coating of the jar or battery ; and the circuit completed 

 by connecting the outer terminal of the other rod with the 

 knob of the jar or battery, by the discharger, as shown. 

 The wet string, or other imperfect conductor, when 



used, can be intro- 

 duced into any con- 

 venient part of the 

 circuit, as at S. 



SPONTANEOUS DIS- 

 CHARGE. A sponta- 

 neous discharge is 

 liable to occur in 

 attempting to charge 

 a jar beyond its ca- 



Fig. 25 Universal Discharger. pacity : and, if the 



glass is thin at any point, it may be fractured in this 

 way ; but if the resistance of the insulating margin is 

 less than that of the glass, the discharge will take place 

 over that surface, without injury to the jar, electricity 

 always following the path of least resistance, whether 

 longer or shorter. 



DISRUPTIVE DISCHARGE. When a discharge takes 

 place through the air or any other dielectric, it is 

 termed disruptive; since the electricity must force a 

 passage and break down opposing barriers. Such a 

 discharge is always accompanied with light, heat, and 

 sound ; as expressed by the terms spark and snap, flash 

 and report effects due to the resistance encountered, 

 and not qualities inherent in electricity. 



