ELEMENTARY MAGNETISM. 349 



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 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 suspended 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 con- 

 fined to what I have uttered here. 



I have said that one end of your bar magnet has a 

 mark upon it ; lay several silk fibres 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 towards 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 north pole yourself, 

 and to mark it with a file. Vary your experiments by 

 causing your magnetised darning-needle to attract and 

 repel your large magnet ; it is quite competent to do 

 so. In magnetising 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- 



