306 



LESSORS IN ELECTRICITY. 



yourstlf. Half of our book-writers describe 

 experiments which they never made, and 

 Uieir descriptions often luck both force and 

 truth ; but no matter how clever or conscien- 

 tious they may be, their written words cannot 

 supply the place of actual observation. 

 Every fact has numerous radiations, which 

 are shorn off by the man who describes it. 

 Go, then, to a philosophical instrumeut- 

 maker, and give, according to your means, 

 for a straight bar-magnet say, half a crown, 

 or, if you can afford it, five shillings for a 

 pair of thorn ; or get a smith to cut a length 

 of ten inches from a bar of steel an inch wide 

 and half an inch thick ; rile its ends decently, 

 harden it, and get somebody like myself to 

 magnetize it. Two bar-magnets are better 

 than one. Procure some darning-needles 

 such as these. Provide yourself also with a 

 little unspun silk ; which will give you a sus- 

 pending tibre void of torsion ; make a little 

 loop of paper or of wire, thus, and attach 

 your fibre to it. Do it neatly. In the loop 

 place your darning-needle, and bring the two 

 ends or poles, as they are called, of your 

 magnet successively up to cither end of the 

 needle. Both the poles, you find, attract both 

 ends of the needle. Replace the needle by a 

 bit of annealed iron wire, the same effects en- 

 su<\ Suspend successively little rods of lead, 

 copper, silver, or brass, of wood, glass, 

 ivory, or whalebone ; the magnet produces 

 no sensible effect upon any of these suh- 

 itances. You thence infer a special property 

 in the case ot steel and iron. Multiply your 

 experiments, however, nndyou will find that 

 some other substances besides iron are acted 

 upon by your magnet. A rod of the metal 

 nickel, or of the metal cobalt, from which the 

 blue color used by painters is derived, ex- 

 kibits powers similar to thoee observed with 

 tho iron and steel. 



In studying the character of the force you 

 may, howeve^r, confine yourself to iron and 

 steel, which are always at hand. Make your 

 experiments with the darning-necdlo over 

 and over again ; operate on both ends of tho 

 needle ; try both ends of the magnet. Do 

 not think the work stupid ; you are convers- 

 ing with Nature, and must acquire a certain 

 grace and mastery over her language ; and 

 these practice can alone impart. Let every 

 movement be made with care,- and - avoid 

 slovenliness from the outset. In every one 

 of your experiments endeavor to feel the re- 

 sponsibility of a moral agent. Experiment, 

 as I have said, is the language by which we 

 address Nature, and through which she sends 

 her replies ; in the use cf this language a 

 lack of straightforwardness is as possible and 

 as prejudicial as in the spoken language of 

 the tongue. If you w ish to become acquaint- 

 ed with the truth of Nature, you must from 

 the first resolve to deal with her sincerely. 



Now remove your iicedlefrorn its loop, and 

 draw it from end to end along one of the 

 ends of thomngnet ; re-suspend'it, tnd repeat 

 your former experiment. You fliul the result 

 different. You now find that each extremity 

 f the magnet attract* one end of the needle 



nnrt repels the other. The simple attraction 

 observed in the first instance is now replaced 

 by a dual force. Repeat the experiment till 

 you have thoroughly observed the ends which 

 attract and those which repel each other. 



Withdraw the magnet entirely from tho 

 vicinity of your needle, and leave the loUer 

 freely suspended by its fibre. Shelter ii as 

 well as you can from currents of air, and if 

 you have iron -buttons on you-r coa't or a slee? 

 penknife in your pocket, beware of their ac 

 tion. If you work at iiight, beware of iron 

 candlesticks, or of brass ones with .iron rod.-} 

 inside. Freed from such disturbaaces, the 

 needle takes up a certain determinate po- 

 sition. It sets its length nearly north an'f 

 south. Draw it aside from this position and 

 let it go. After several oscillations it will 

 again come to it. If you have obtained your 

 magnet from a philosophical instrument- 

 maker, you will see a mark on one of its emls. 

 Supposing, then, that you drew your needle 

 along the end thus marked, and that the eye- 

 eud of your needle was the last to quit the 

 magnet, you will find that the eye turns to 

 the south, the point of the needle turning 

 toward the north. Make suie of this, and do 

 not take this statement on my authority. 



Now lake a second darning-needle like the 

 first, and magnetize it in precisely the same 

 manner : freely suspended it also will turn its 

 point to the north and its eye to the south. 

 Your next step is to examine the action ot" the 

 two needles which you have thus magnelizvri 

 upon each other. 



Take one ot them in your hand, and leave 

 the other suspended ; bring the eye-end of 

 the former near the eye-end of the latter ; the 

 suspended needle retreats : it is repelled. 

 Make the same experiment with the two 

 points, you obtain the same result, the sus- 

 pended needle is repelled. Now cause tho 

 dissimilar ends to acton each other you 

 have attraction point attracts eye and eye 

 attracts point. Prove the reciprocity of this 

 action by removing the suspended needle, 

 and putting the other in its place. You ob- 

 tain the same result. The attraction, then, 

 is mutual, and the repulsion is mutual, and 

 you have thus demonstrated in the clearest 

 manner the fundamental law of magnetism, 

 that like poles repel, and that, .unlike poles at- 

 tract each other. You may say that this is 

 all easily understood without doing ; but do 

 it, and your knowledge will not be confined 

 to what I have uttered here. 



I have said that one end of your magnet 

 has a mark upon it ; lay several silk fibres 

 together, sa as to get sufficient strength, or 

 employ a thin silk ribbon, and form a loop 

 large enough to hold your magnet. Suspend 

 it ; it turns its marked end toward the north. 

 This marked end is that which in England is 

 called the north pole. If a common smith 

 has made your magnet, it will be convenient 

 to determine its noith pole yourself, and to 

 mark it with a file. You vary your experi- 

 ments by causing your magneti/ed darning- 

 needle to attract and repel your larpe mag- 

 net ; it is guile competent to do so. In 



