ELECTRIC EXPERIMENTS. 



235 



the upper side of the pane directly over this pointed conductor place 

 a drop of oil. From an insulated support lower a second pointed 



FIG. 1 80. 



conductor until it touches the pane at the oil. Through these two 

 pointed conductors (Fig. 180) discharge a Leyden jar or battery. 

 Unless the glass is very thin, a single jar will not be sufficient. If 

 the experiment fails the first time, do not use the same piece of glass 

 for the second trial. 



(34.) With corks, plug the ends of a glass tube filled with water. 

 Through the corks, introduce copper wires until the ends in the 

 water are within a quarter of an inch of each other. Through 

 these wires discharge a Leyden jar. The mechanical shock due to 

 the repulsion of the electrified water molecules will break the tube. 



(35.) Fig. 181 represents "Volta's Pistol," which consists of a 

 metal vessel through one side of which passes an insulated metal 

 rod with knobs at both ends. The knob at the 

 inner end of this rod is near the opposite wall, 

 so that a spark may easily be made to pass 

 between the knob and the body of the pistol. 

 The pistol being filled with a mixture of illu- 

 minating gas and common air in equal volumes 

 or with oxygen and hydrogen in the proportion 

 of one volume of the former to two of the latter, 

 and the mouth being closed by a cork, the pas- 

 sage of the spark brings about a chemical union 

 of the mixed gases, a violent explosion ensues, 

 and the cork is thrown some distance. The FTG. 181. 



