320 ELECTRICITY. 



consist of the electricity which is thus excited. 

 Many bodies are capable of thus exhibiting elec- 

 trical appearances when rubbed ; the chief of these 

 are glass, amber, sealing-wax, resin, sulphur, hair, 

 wax, the precious stones, &c. from which they are 

 called electrics. On the contrary, such substances 

 as are not capable of being excited, are called non- 

 electrics. 



The explanation of these phenomena is as follows: 

 When the square piece of wood LM1K (which 

 may represent the shutter of a window), is fixed 

 into the hole, so that the wire I K stands in the 

 dotted representation L M, then the metallic com- 

 munication from H to N is complete, and the in- 

 strument represents a house furnished with a proper 

 metallic conductor ; but if the square piece of wood 

 L M I K is fixed so that the wire I K stands in the 

 direction I K, as represented in the figure, then 

 the metallic conductor H N from the top of the 

 house to its bottom is interrupted at L M ; in which 

 case the house is not properly secured. 



Fix the piece of wood LMIK, so that its wire 

 may be as represented in the figure, in which case 

 the metallic conductor H N is discontinued. Let 

 the ball G be fixed at about half an inch perpen- 

 dicular distance from the ball Hj then, by turning 

 the glass pillar C, remove the former ball from the 

 latter ; by a wire, or chain, connect the wire E F 

 with the wire Q of the jar Pj and let another wire, 

 or chain, fastened to the hook O, touch the outside 

 coating of the jar. Connect the wire Q with the 

 prime conductor, and charge the jar : then, by 

 turning the glass pillar D C, let the ball G come 

 gradually near the ball H, and when they are ar- 

 rived sufficiently near one another, you will ob- 

 serve that the jar explodes, and the piece of wood 



