ELECTRIC EXPERIMENTS. 



333 



coat will be beautifully illuminated at 

 the passage of each such spark. 



(28.) The "luminous pane" is repre- 

 sented in Fig. 175. A continuous tin- 

 foil strip is pasted back and forth upon 

 the surface of a plate of glass. The 

 upper end of this strip is connected with 

 the prime conductor ; the lower end 

 with the earth. A series of breaks in 

 this continuous conductor may be made 



by cutting it 



across with a 



sharp pen- 

 knife. When 



the machine 



is worked a 



small spark 



will appear 



at each break 



thus made. FIG. 175. 



These breaks 



may be arranged so as to represent a 



flower, star, arch, 



word or other design. 



The sparks are really 



successive, but they 



seem to be simulta- 

 neous. Explain. 



(29.) The "luminous 



globe " is represented 



in Fig. 176. and the 



"luminous tube " in Fig. 177. The first of these 

 consists of a hollow glass globe, on the inner 

 surface of which small discs of tinfoil are placed 

 very near each other. The first disc is in con- 

 nection with the prime conductor, and the last 

 one, with the ground. When the machine is 

 worked, bright sparks appear at each break 

 between the discs. The construction and action 

 of the luminous tube are similar. Like the 

 "luminous pane," these pieces of apparatus are 

 intended for use in the dark. All of these lu- p IG 



FIG. 176. 



