352 FEAGMENTS OF SCIENCE. 



single pole that each half possesses two poles with a 



O i^ A A 



neutral point between them. And if you again break 

 the half into two other halves, you will find that each 

 quarter of the original strip exhibits precisely the same 

 magnetic distribution as the whole strip. You may 

 continue the breaking process : no matter how small 

 your fragment may be, it still possesses two opposite 

 poles and a neutral point between them. Well, your 

 hand ceases to break where breaking becomes a mecha- 

 nical impossibility ; but does the mind stop there ? 

 No : you follow the breaking process in idea when you 

 can no longer realise it in fact ; your thoughts wander 

 amid the very atoms of your steel, and you conclude 

 that each atom is a magnet, and that the force exerted 

 by the strip of steel is the mere summation, or resultant, 

 of the forces of its ultimate particles. 



Here, then, is an exhibition of power which we can 

 call forth at pleasure or cause to disappear. We mag- 

 netise our strip of steel by drawing it along the pole of 

 a magnet ; we can demagnetise it, or reverse its mag- 

 netism, by properly drawing it along the same pole in 

 the opposite direction. What, then, is the real nature 

 of this wondrous change ? What is it that takes place 

 among the atoms of the steel when the substance ie 

 magnetised ? The question leads us beyond the region 

 of sense, and into that of imagination. This faculty, 

 indeed, is the divining-rod of the man of science. 

 Not, however, an imagination which catches its crea- 

 tions from the air, but one informed and inspired by 

 facts ; capable of seizing firmly on a physical image 

 as a principle, of discerning its consequences, and of 

 devising means whereby these forecasts of thought 

 may be brought to an experimental test. If such a 

 principle be adequate to account for all the phenomena 

 if from an assumed cause the observed acts neces- 



