MAGNETIC POLARITY. 237 



We have not to deal with the history of magnetic 

 discovery, but so far as it tells of the strange pro- 

 perties which magnets are found to possess, and the 

 application of this knowledge to the elucidation of 

 effects occurring in nature. 



A brown stone, in no respect presenting anything by 

 which it shall be distinguished from other rude stones 

 around it, is found, upon close examination, to possess the 

 power of drawing light particles of iron towards it. If 

 this stone is placed upon a table, and iron filings are 

 thrown lightly around it, we discover that these filings 

 arrange themselves in symmetric curves, proceeding 

 from some one point of the mass to some other ; and 

 upon examining into this, we shall find that the iron 

 which has once clung to the one point will be rejected 

 by the other. If this stone is freely suspended, we 

 shall learn also that it always comes to rest in a certain 

 position, this position being determined by these 

 points, and some attractive force residing in the earth 

 itself. These points we call its poles ; and it is now 

 established that this rude stone is but a small represen- 

 tative of our planet. Both are magnetic : both are so 

 in virtue of the circulation of currents of electricity, or 

 of lines of magnetic force, as seen in the curves formed 

 by the iron dust, and the north pole of the one attracts 

 the south pole of the other, and the contrary. By a 

 confusion of terms we speak of the north pole of a com- 

 pass-needle, meaning that point which is always oppo- 

 site to the north pole of the earth : the truth being that 

 the pole of the compass-needle, which is so forcibly 

 drawn to the north, is a point in a contrary state, or, as 

 we may express it, really a south pole. 



There is a power of a peculiar kind, differing from 

 gravitation, or any other attracting or aggregating force 

 with which we are acquainted, which exists permanently 

 in the magnetic iron stones, and also in the earth. 

 What is this power ? 



