ELECTRICAL APPARATUS. 



279 



very light, and supporting near its extremities small figures. 

 A glass pillar supports a brass ball at one end of the stand, 

 and a metal rod another ball at the other end ; these balls 

 connected with the Leyden jar, will cause the beam to move 

 up and down with a pleasing effect. Price, $3.00. 



Fig. 310. 



Fig. 309. 



L 



O 



Electrical Pendulum. (Fig. 310, as above.) This is a 

 plate of glass about ten inches square, mounted on a wooden 

 base, and having a delicate balance suspended on the top of 

 the plate, the ends having pith balls attached ; this is made 

 so as to vibrate easily, the balls alternately touching the 

 sides of the glass plate, which is coated with tin foil to within 

 an inch and a half of the edge, which, when charged, will 

 cause the pendulum to vibrate, and thus discharge the plate. 



Price, $2.50. 



Electrical Spider and Jar. (Fig. 311, next page.) A 

 small object in the shape of a spider, formed of cork, or pith, 

 having legs of thread, and supported by a silken thread 

 between two Leyden jars, or between one jar and a ball con- 

 nected with the outside coating of the jar, the spider will 

 be attracted from the one to the other, thus discharging the 

 jar. Price, $2.75. 



Jar with Ball from Outer Coating. (Fig. 312, next page.) 

 There is attached to the outside coating of the jar, a, ex- 

 posing about a square foot of coated surface, a curved wire, 

 b, terminated by a metallic ball, c, rising to the same height 

 as the knob of the jar, d ; charge the jar, and suspend 



