804 



LESSONS IN ELECTRICITY. 



peared also ? No. Remove the glass 

 tube, and once more touch the egg at b 

 by the carrier. It is charged, not with 

 positive, but with negative electricity. 

 nearly understand this experiment. The 

 neutral electricity of the egg is first de- 

 composed into negative and positive ; the 

 former attracted, the latter repelled by 

 the excited glass. The repelled elec- 

 tricity is free to escape, and it has escaped 

 on your touching the egg with your fin- 

 ger. But the attracted electricity cannot 

 escape as long as the influencing tube is 

 held near. On removing the tube which 

 holds the negative fluid in bondage, that 

 fluid immediately diffuses itself over the 

 whole egg. An apple, or a turnip, will 

 answer for these experiments at least as 

 well as an egg. 



Discharge the egg by touching it. Rc- 

 cxcite the glass tube and bring it again 

 near. Touch the egg wth a wire or with 

 your finger at a. Is it the negative at a, 

 into which you plunge your finger, 

 tlutt escapes ? No such thing. The free 

 positive fluid passes through the nega- 

 tive, and through your finger to the 

 earth. Prove this by removing, first, 

 your finger, and then the glass tube. The 

 egg is charged negatively. 



Again ; place two eggs, E E, fig. 17, 



PIG. 17. 



lengthwise on two dry wine-glasses, g g, 

 and cause two of their ends to touch 

 each other, as at c. Bring your rubbed 

 glass rod near the end a, and while it is 

 there separate the eggs by moving one 

 glass away from the other. Withdraw 

 the rod and test both eggs, a repels 

 rubbed sealing-wax, and b repels rubbed 

 glass ; a is therefore negative, b is posi- 



tive. The two charges, moreover, exact- 

 ly neutralize each other in the oiectro- 

 scope. Again l>rinj the eggs together 

 and restore the rubbed tube to its plao 

 near a. Touch a and then separate . tho 

 eggs. Remove the glass rod an-1 t^st the 

 eggs. a is negative, b is reutral. Its 

 electricity lias escaped through the lin- 

 ger, though placed ;.t a. 



Equally good, if not indeed more 

 handy, for theso experiments arc two 

 apples A A, fig. 10, supported on stems 

 cf sealing-wax. A needle is healed L;. \ 

 sni-k in each case into the rtick of wax at 

 the top, and on to the nccilc the apple is 

 pushed. The sealing-wax stems are stuck 

 on by melting to little foot-boards. By 

 arrangements of this kind you rnako ex- 

 periments which are more instructive than 

 those usually made with instruments 

 twenty times more expensive. 



Push vour researches still farther, and 

 instead of bringing the eggs or apples to- 

 gether place them six feet or so apart, 



FIG. 18. 



and let a light chain, c, fig. 19, or a wire, 

 stretch from one to the other. Two 

 brass balls, or wooden balls covered with 



tin-foil, supported by tall drinking glasses, 

 ' will be better than the eggs for this 



GG 



experiment, for they will bear better the 

 strain of the chain ; but you can make 

 the experiment with the eggs, or very 

 readily with the two apples or two tur- 

 nips. For the present we will suppose 

 the straw-index 1 1' not to be there. Rub 



