ELECTRIC EXPERIMENTS. 229 



(12.) If a pupil, standing upon an insulating stool (a board sup- 

 ported by four warm tumblers will answer) and having one hand 

 upon the prime conductor of an electric machine in action, bring a 

 knuckle of the other hand near one end of the balanced meter stick 

 ( 323), it will follow the knuckle. Explain. 



(13.) If, instead of placing one hand upon the prime conductor, he 

 hold a Leyden jar by the outer coat and by a wire connect the knob 

 of the jar with the prime conductor, his knuckle will attract the 

 balanced meter stick when the machine is worked. Explain. 



(14.) Half fill a wide glass vessel with water. Within this place 

 a glass beaker and fill this to the same level with water. By a 

 wire, connect the water in the outer vessel with the earth ; in 

 similar manner connect the water in the beaker with the electric 

 machine. Give the handle of the machine a single turn. Dipping 

 one finger into the outer water and another into the inner water, a 

 shock is felt. Explain. 



(15.) Coat both sides of a pane of glass with tinfoil to within three 

 inches of the edge. Place the under coat in, communication with 

 the ground and the upper coat with the prime conductor. Place a 

 coin upon the upper coat and work the machine. Try to remove 

 the coin and a shock will be felt. Explain. 



(16.) Let a pupil stand upon an insulating stool and place his left 

 hand upon the prime conductor. Let him with his right hand clasp 

 the left hand of another pupil not insulated, their hands being pre- 

 vented from actual contact by an intervening sheet of india-rubber 

 cloth. After the machine has been worked a moment, let the insu- 

 lated pupil remove his left hand from the prime conductor and clasp 

 the free hand of his companion. At this moment of clasping hands 

 a shock will be felt. Explain. 



(17.) Fasten a small paper kite by a linen thread to the prime 

 conductor. When the machine is worked, the kite^will float around 

 the knob. Explain. 



(18.) Place a few bits of paper upon the cover of the electropho- 

 rus. When the cover has been touched with the finger and lifted 

 by the insulating handle, the paper will be thrown off. Explain. 



(19.) Cover one knob of the discharger with gun cotton sprinkled 

 with powdered rosin. When the Ley den jar is discharged with 

 this discharger, the cotton and rosin are ignited. 



(20.) The " electric bomb," represented in Fig. 1G9, may be made 

 of ivory, heavy glass, or thoroughly-seasoned wood. The ends of 

 the two metal wires are rounded and placed a short distance apart. 



