MEDIUM OF MECHANICAL ACTION. 



2 9 



originally adopted by moving two metallic plates, 



held by insulating 



glass handles (Fig. 3), 



which, after contact 



and separation, excite 



movements of electro- Fift 3< 



scopes. 



To intensify the excitation of the plate, a cake 

 of sealing 

 wax, c, ex- 

 cited by fric- 

 tion with fur, 

 is commonly 

 used, as rep- 

 resented by 

 Fig. 4. Hold- 

 ing the plate c 

 D by the in- 

 sulating glass Fig. 4 . 

 handle K, and reaching the finger toward the 

 metallic knob N, a spark is seen to leap through 

 the air from N to the finger, when the plate D is 

 brought near and in contact with c ; on lifting 

 the plate and again bringing the finger toward N, 

 a similar bright spark leaps back to the plate. 



This simple apparatus, by the alternate move- 

 ment of the upper plate toward and from the 

 lower plate, produces such dazzling sparks, that 

 the original inventor gave to it the name of 

 ELECTROPHORUS ; from ELEKTOR, sunshine, and 

 PHOREO, 7 bring. 



