ELEMENTARY MAGNETISM. 415 



filings, or the scraps of wire, from a sieve upon the 

 paper, and tap the latter gently, so as to liberate the 

 particles for a moment from its friction. The magnet 

 acts on the filings through the paper, and see how it 

 arranges them ! They embrace the magnet in a series 

 of beautiful curves, which are technically called ' mag- 

 netic curves,' or 'lines of magnetic force.' Does the 

 meaning of these lines yet flash upon you ? Set your 

 magnetic needle, or your suspended bit of wire, at any 

 point of one of the curves, and you will find the direc- 

 tion of the needle, or of the wire, to be exactly that of 

 the particle of iron, or of the magnetic curve, at that 

 point. Go round and round the magnet ; the direction 

 of your needle always coincides with the direction of 

 the curve on which it is placed. These, then, are the 

 lines along which a particle of south magnetism, if you 

 could detach it, would move to the north pole, and a 

 bit of north magnetism to the south pole. They are 

 the lines along which the decomposition of the neutral 

 fluid takes place. In the case of the magnetic needle, 

 one of its poles being urged in one direction, and the 

 other pole in the opposite direction, the needle must 

 necessarily set itself as a tangent to the curve. I will 

 not seek to simplify this subject further. If there be 

 anything obscure or confused or incomplete in my 

 statement, you ought now, by patient thought, to be 

 able to clear away the obscurity, to reduce the con- 

 fusion to order, and to supply what is needed to render 

 the explanation complete. Do not quit the subject 

 until you thoroughly understand it ; and if you are 

 then able to look with your mind's eye at the play of 

 forces around a magnet, and see distinctly the operation 

 of those forces in the production of the magnetic curves, 

 the time which we have spent together will not have 

 been spent in vain. 



