276 FRAGMENTS OF SCIENCE. 



the iron filings very small scraps of thin iron wire might 

 be employed. I place a sheet of paper over the magnet; 

 it is all the better if the paper be stretched on a wooden 

 frame, as this enables us to keep it quite level. I scatter 

 the 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 "magnetic 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 direction 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 plaice. In the case of the mag- 

 netic needle, one of its poles being urged in one direction, 

 and the other pole in the opposite direction, the needle 

 must necessarily setitself as a tangent to the curve. I will 

 not seek to simplify this subject further. If there be any- 

 thing 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 confusion to order, and 

 to supply what is needed to render the explanation com- 

 plete. 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. 



In this thorough manner we must master our materials, 

 reason upon them, and, by determined study, attain to 

 clearness of conception. Facts thus dealt with exercise an 

 expansive force upon the intellect they widen the mind 

 to generalization. We soon recognize a brotherhood 

 between the larger phenomena of Nature and the minute 



