266 VttAGMENTS OF SCIENCtt. 



pended; 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 suspended needle is repelled. Now 

 cause the dissimilar ends to act on each other you have 

 attraction point attracts eye, and eye attracts point. 

 Prove the reciprocity of this action by removing the sus- 

 pended needle, and putting the other in its place. You 

 obtain the same result. The attraction, then, is mutual, 

 and the repulsion is mutual. You have thus demonstrated 

 in the clearest manner the fundamental law of magnetism, 

 that like poles repel, and that unlike poles attract 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 bar-magnet has a mark 

 upon it; lay several silk fibers together, so 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 con- 

 venient to determine its north pole yourself, and to mark 

 it with a file. Vary your experiments by causing your 

 magnetized darning-needle to attract and repel your large 

 magnet; it is quite competent to do so. In magnetizing 

 the needle, I have supposed the point to be the last to quit 

 the marked end of the magnet; the point of the needle is 

 a south pole. The end which last quits the magnet is 

 always opposed in polarity to the end of the magnet with 

 which it has been last in contact. 



You may perhaps learn all this in a single hour; but 

 spend several at it, if necessary; and remember, under- 

 standing it is not sufficient: you must obtain a manual 

 aptitude in addressing Nature. If you speak to your 

 fellow-man you are not entitled to use jargon. Bad ex- 

 periments are jargon addressed to Nature, and just as 

 much to be deprecated. Manual dexterity in illustrating 

 the interaction of magnetic poles is of the utmost impor- 

 tance at this stage of your progress; and you must not 

 neglect attaining this power over your implements. As 

 you proceed, moreover, you will be tempted to do more 

 than I can possibly suggest. Thoughts will occur to you 



