Aug. 21, 1885.] 



KNOWLEDGE 



terous. But it shows that in one -way or another we 

 have to admit the existence of conditions in Jupiter 

 which are utterly different from any known on earth. 

 {To be continued.) 



THE YOUNG ELECTRICIAN. 



By W. Slingo. 



(Continued from p. 113.) 



EX. C. — A simply-performed experiment is illustrated 

 in Fig. 55. A B is an electrified rod (of any 

 convenient material, in this case glass). G G are dry 

 warm wine-glasses, E E are eggs placed on the glasses as 

 shown, and touching each other, as at F. On A B being 

 broaght near C the eggs become inductively electrified, 

 the near end, C, assuming a state l^(negative) opposite to 

 that on the adjacent electrified rod. The end D of the 

 other egg becomes simultaneously charged with positive 

 electricity, and were means readily available for investi- 

 gating the condition of either egg at F, that condition 

 would be found to be neutral. With such investigations 

 we may deal presently. If, while the state of affairs 

 remains as indicated in the diagram, the approach of a 

 suspended feather or pith ball to D will result in attrac- 

 tion. Assuming the suspended substance to have been 

 keijt from actual contact with the egg, and to be removed 

 together with A B, the eggs will return to the neutral 

 state, neither D nor G showing any signs of electrification. 

 Nothing has been given to or taken from them. 



Pig. 55. 



Let A B again approach C, the eggs become electrified 

 as before. While A B is still in the vicinity of G, separate 

 the remote or positively- charged egg to a short distance 

 — say half-an-inch — from the other. This can be done 

 with the left hand (catching hold of the glass as low 

 down as possible, and with dry fingers), the right hand 

 still grasping the end, B, of the electrified rod. Next 

 oveABto a considerable distance. The eggs will 

 ' show feeble signs of electrification at C and D, 

 e the opposite charges, in their effort to produce 

 3 neutral state, have taken up their position at the 

 adjacent extremities, F. Let the eggs be now separated 

 s to bo practically out of each 



to a greater distance, i 

 other's range of influci 

 the charges on the lu-s will lir 4i>tr 

 surfaces, the grcafi'si ;icciiiiiul:ii inn I 

 the ends, because the srll'-n'|i(ll:iut ii:iiu 

 is more nearly satisfied there than ;il 

 therefore less distant) parts of the . 

 will then exhibit more or less jiow. 

 electricity, and will bo capable nf 

 bodies. After discliarging the 



■ the 



aga: 



brought into contact and let the positively elec 



trifled rod A B again approach C, so as to once more 

 electrify the eggs. Then let D be touched by the finger 

 or any other large conductor ; D will be by that means 

 neutralised, and, however great may be the electrification 

 at C, no charge can be maintained at D. The same re- 

 sult would follow were the finger placed at any other 

 part (except that part immediately opposite A) of either of 

 the eggs. In effect, the remote end of the conductor 

 G D is removed to an infinite distance (as indicated in 

 Ex. XGIX.). Let us confine the finger to some portion 

 of the remote egg E D. The removal of AB wiU allow 

 the negative charge on the other egg to be neutralised. 

 This will not happen if A B be kept near G. Let the 

 finger remain on the remote egg, and let that egg be re- 

 moved. It will, of course, be neutral ; but the subse- 

 quent removal of A B will leave the near egg charged 

 with negative electricity, and it will be able to show its 

 charge by any of the previously-mentioned methods. 



These two eggs, then, teach us a great deal. Indeed, 

 they may presently teach us a deal more. 



Ex. GI.— Fig. 5G illustr.ates another device for per- 

 forming all the experiments contained in Ex. G. A is 

 an electrified rod; D G, G B are two apples (with the 

 stalks cut short) suspended by means of dry silk threads 

 from any convenient support, such as a horizontal 

 wooden lath or even a metal rod. The longer the thread, 

 that is, the greater the distance from the horizontal rod, 

 the better. Pared potatoes, turnips, rounded carrots or 

 parsnips, would answer equally well, for all are 

 sufiiciently good conductors. 



Ex. Gil. — A similar experiment, but on a somewhat 

 more elaborate scale, is illustrated in Fig. 57. D and C 

 are cylinders coated with tinfoil or other thin metal, 

 similar in every respect to the one described in Ex. 

 XGYII. S S are the insulating supports, and A B is the 



Fig. 57. 



rod electrified, let us say, positively. The near end of 

 G becomes negatively electrified, and the remote end 



iH.silivi'Iv Wo ii"\v utI a .species of induction by deputy. 

 l''.n- ilu' jMisitixc rli',ir-'i' "ii tlu' <li>tant end of G acts in 

 it^dini iiulurii\.K nil ilir ailiuTUi i-ylinder D, making 

 tlu- lu-ar rial lu-'-afivo aial tin- rrinnle end positive. This 

 state of affairs is evidenced by the positions assumed by 

 the suspended but uninsulated pith balls. They mani- 



