230 



ELECTRIC EXPERIMENTS. 



The bomb may be filled with gunpowder. One wire is connected 



by a chain with the outer 



coat of a charged Leyden 



jar. The other wire is to 



be connected with the 



inner coat by a wet string 



and the discharger. The 



FIG. 169. 



spark between the ends 

 of the two wires ignites 

 the powder. Try the ex- 

 periment with air instead 

 of powder. 



(21.) Fig. 170 illus- FIG. 170. 



trates a method of igniting an inflammable liquid, like ether or 

 alcohol, by the electric spark. Through the bottom of a small glass 

 vessel, a, passes a metal rod, having a knob at its upper extremity. 

 The lower end of this rod may be brought into electrical connection 

 with the outer coat of a Leyden jar. Enough ether or alcohol is 

 poured into a just to cover the knob. When the jar is discharged 

 in the way showai in the figure, the spark ignites the liquid. If 

 alcohol is used it may have to be warmed to render the experiment 

 successful. 



(22.) Let a pupil, standing on an insulating stool, become charged 

 by holding one hand on the prime conductor when the machine is 

 in operation. If he then bring his knuckle to a metal burner from 

 which a jet of gas is issuing, a spark will pass between the knuckle 

 and the burner, igniting the gas. An Argand or Bunsen burner 

 answers well for this experiment. The experiment may be modi- 

 fied by using, instead of the knuckle, an icicle held in the hand. 



(23.) The " universal discharger," shown in Fig. 171, consists of a 

 glass table and two insulated metal rods. The rods are provided 



