36 l 2 ELECTRICITY. 



rupted by cutting, the space is increased; and in 

 long conveyances, the space will sometimes amount 

 to more than the machine will be able to overcome; 

 therefore, the shorter the illuminations are, the 

 more pleasing they will appear. 



To shoxv how a Jar charges and discharges. 



Coat a jar, as represented Plate 21. flg. 1., by 

 pasting small pieces of tin-foil, at a little distance 

 from each other, round its exterior surface. As 

 this jar is charging, small sparks will pass from one 

 piece of tin-foil to another, in a variety of di- 

 rections; the separation of the tin-foil is the means 

 of making the passage of the fluid, from the outside 

 of the jar to the table, visible. Discharge this jar, 

 by bringing a pointed wire gradually near the 

 brass ball, and the uncoated part of the glass, be- 

 tween the pieces of tin-foil, will be pleasantly illu- 

 minated, and make a crackling noise ; but if the jar 

 be discharged suddenly, the whole outside sur- 

 face will appear illuminated. The glass must be 

 very dry, to produce these appearances to the 

 greatest advantage. 



To pierce a Card by Electricity. 



Take a card or quire of paper, or two cards kept 

 asunder by the interposition of little bits of wax 

 here and there: place either of those articles flat 

 against the outside coating of a charged jar, and 

 put one of the knobs of the discharging-rod over 

 it, so that the card, or quire of paper, or the two 

 cards, may be interposed between that knob and 

 the coating of the jar: then by bringing the other 

 knob of the discharging-rod near the wire of the 



