ELEMENTARY MAGNETISM 369 



ient 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 

 which you will endeavor to follow out: questions will arise 

 which you will try to answer. The same experiment may 

 be twenty different things to twenty people. Having wit- 

 nessed the action of pole on pole, through the air, you 

 will perhaps try whether the magnetic power is not to be 

 screened off. You use plates of glass, wood, slate, paste- 

 board, or gutta-percha, but find them all pervious to this 

 wondrous force. One magnetic pole acts upon another 

 through these bodies as if they were not present. Should 

 you ever become a patentee for the regulation of ships' 

 compasses, you will not fall, as some projectors have 



