LESSORS IX E.ECTKICITr. 



make a jar for yourself. Bad glass, re- 

 member, is not rare. In fig. 35 you 

 have such a jar. T is the outer-, T' the 

 inner coating, reaching to within irn inch 

 c-f the edge of the tumbler G. ^' is the 



FIG. 33. 



Fia.36. 



wire fastened below by wax, and sur- 

 mounted by a knob, which may be of 

 metal, or of wax or wood, coated with 

 tin-foil. In charging the jar you con- 

 nect the outer coating with the earth 

 ay with a gas-pipe or a water-pipe and 

 present the knob to the conductor of 

 your machine. A few turns will charge 

 the jar. It is discharged by laying one 

 knob of a ** discharger" against the 

 outer coating, and causing the other knob 



to approach the knob of the jar. Be- 

 fore contact, the electricity flies from 

 knob to knob in the form of a spark. 



A " discharger" suited to our means 

 and purposes is shown in fig. 36. n is a 

 stick of sealing-wax, or, better still, of 

 ebonite ; w w a stout wire bent as in the 

 figure, and ending in the knobs B B'. 

 These may be of wax coated with tin- 

 foil. Any other light conducting knobs 

 would of course answer. The insulating 

 handle n protects you effectually from 

 the shock. 



You must render yourself expert in the 

 use of the discharger. The mode of 

 using it is shown in rig. 37. 



By augmenting the size of a Leydsn 

 jar we render it capable of accepting a. 

 larger charge of electricity. But there 

 is a limit to the size of a jar. When 

 therefore, larger charges are required 

 than a single jar can furnish, we make 

 use of a number of jars. In tig. 38 nine 

 of them are shown. All their interior 

 coatings are united together by brass 

 rods, while all Um outer coatings rest 

 upon a metal suiface in free communica- 

 tion with the eaith. 



This combination of Leydcn jars con- 

 stitutes the Leydcn Battery, the effect of 

 which is equal to that of a single jar ,f 

 nine times the size of one of the jars. 



20. Explanation of the Leydcn Jar. 

 The principles of electrical induction 



