KI.ECTKK ITV. 



319 



ELECTRICITY. VI. 



KLECTBIFIED PITH BALLS DANCING FIGURES KLKCTBIC 

 BILLS EFFECTS OF A POINT ELECTRIC AUBA ELECTBIC 

 FLYER LICHTENBEBO'B FIOUBES CHEMICAL EFFECTS 

 ELECT ROPHOBU8. 



THERE are many interesting experiments, betide* those already 

 explained, which illuatrate more fully the principles of elec- 

 trical attraction and repulsion ; and to some of these we must 

 now direct our attention. Balls mode out of the pith of the elder 

 are well adapted for many of those experiments, on account of 

 their i-xtromo lightness. If wo place a number of these balls on 

 a metal tray, ard cover them with a glass shade, fitted at the top 

 with a cap through which a brass wire 

 passes (Fr.r L' 1 1. wo shall find that, when 

 the wire in connected with the prime 

 conductor and the machine is set in 

 action, the balls will dance up and down 

 very rapidly. The rod is made to slip 

 tightly through the cap at the top of 

 the shade, so that the ball may be ad- 

 justed to any required height, according 

 to the power of the machine. 



The explanation of this experiment is 

 simple. The brass ball, being connected 

 with the conductor, becomes highly 

 charged, and therefore attracts the 

 light particles of pith. As soon, how- 

 ever, as they touch it, and share 

 its electricity, they are repelled, and 

 fly off violently, so that they 

 would roll quite away were 

 they not confined by the 

 shade. On again touching 

 the tray, each parts with its 

 share of the electricity, and 

 rises as before for a fresh 

 supply. This is by far the 

 best mode of trying the ex- 

 periment ; there is, however, 

 a much simpler plan, which 

 consists in inverting over the 

 balls a common tumbler, pre- 

 viously rendered thoroughly 

 dry and warm. A chain from 

 the conductor is then hud on 

 the bottom of the glass. The 

 electricity thus collected on 

 the exterior surface sets free 

 a corresponding amount on 

 the interior, and the balls rise 

 and convey this away by the 

 tray to the ground. In this 

 case a charge soon accumu- 

 lates in the glass, and must 

 be discharged, or the balls 

 will cease to rise. 



If a pointed wire be in- 

 serted in the conductor, and 

 a tumbler be then held so 

 that different portions of its 

 interior are exposed to the 



action of the point, it will become charged, and on placing it over 

 the balls, they will dance as before. Here, too, the glass be- 

 comes charged in a similar way to that in which a Leyden jar 

 does, and when the action nearly ceases it may be renewed by 

 touching the exterior with the hand, thus removing the free 

 electricity there, and setting free a further amount within. 



Let a disc of metal, or thin wood carefully coated with tin- 

 foil, and having a diameter of five or six inches, bo suspended 

 from the conductor, so as to be about one and a-half or two 

 inches above a similar but rather larger plate supported under 

 it. On this lower plate place some small figures of men dancing, 

 cut out of pith or cardboard ; as soon as the machine is worked 

 they will rise, and then dance up and down rapidly, thus carry- 

 ing away the electricity from the upper plate. The figures 

 should be cut so that their feet are rather heavier ; the upper 

 part should also be somewhat pointed, as otherwise they have a 



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tendency to dance with the haul downward!. Sometime* two 

 brass wire*, with the end* turned orer so as to avoid the effects 

 of the rough ends, are substituted for the two plates, and thus 

 we hare the electrical rope-danoer. This experiment is, however, 

 more difficult to manage properly. 



On the same principle we hare the electric swing, in which a 

 figure supported bj a silk thread U mad* to swing backwards 

 and forwards between two brass balls, one of which is connected 

 with the conductor and the other with the ground. The electric 

 seesaw is merely another ^modification of the tame apparatus. 

 The beam in it must be very carefully balanced, and should 

 turn freely. 



Fig. 22 represents the electric bells. The middle one, c, i* 

 suspended by a thread of silk, and from 

 it a small piece of chain leads to the 

 ground. The other two bells are sus- 

 pended by pieces of chain from the 

 metal bar. Between them are small 

 metal bolls hung by silk threads ; but- 

 tons will answer well for these. As 

 so m as the machine is worked, the bells 

 A and B become positively charged, and 

 attract the clappers ; these take a por- 

 tion of their electricity, and, being then 

 repelled, convey it to the middle bell. 

 by which they are attracted, and thux 

 to the ground. In this way they are 

 kept in a state of oscillation as long as 

 the machine is worked. Bells con- 

 structed on this principle are scm 

 ^^ fitted to wires arranged for 



"^ showing the electricity of the 



atmosphere, and at once ring 

 and call the attention when 

 the air is more than usually 

 charged with the electric 

 fluid. 



Procure two pieces of board 

 two or three feet long, and, 

 having coated them with tin- 

 foil, suspend one by means of 

 silk threads ; then connect it 

 with the machine, placing 

 the other a few inches under 

 it, and connect it with the 

 ground. If now bran or a 

 number of small pieces of 

 paper be scattered on the 

 lower one, they will collect 

 and arrange themselves in a 

 column, rolling about after 

 the manner of columns of 

 sand in a desert when a 

 whirlwind is raging. Many 

 other experiments, showing 

 the manner in which lightning 

 strikes different objects, may 

 also be tried with these 

 boards. 



If a basin of water be 

 placed on an insulating stand, 

 and charged with electricity, 



an imitation swan placed on it will at once be attracted by and 

 follow the finger or any conducting body held to it. A small 

 boat may also be placed on the water, but if a pointed wire be 

 fixed to it, it will be repelled instead of being attracted. A point 

 held to it will also produce the some effect. 



We will now speak of the mechanical and other effects pro- 

 duced by a point, some of which have been already referred to 

 by way of caution in making the machine. When a pointed 

 wire is fixed in or near the conductor, the induction at the point 

 is so much increased, on account of the large surface which it 

 faces, that the electricity cannot be confined, but is dissipated 

 and lost. A needle held at the distance of a few feet from tba 

 conductor will seriously impair the power of a machine, anu 

 particles of dust act in the same way, though, of course, in a 

 much smaller degree. If the hand be held near a point fixed in 

 the conductor a distinct breeze will bo felt, and if the faco be 



