354 FKAGMENTS OF SCIENCE. 



then it will attract the green, and, the forces being 

 equal, they neutralise each other. In fact, the least 

 reflection shows you that the strips will be as indifferent 

 to each other as two unmagnetised darning-needles 

 would be under the same circumstances. 



But suppose, instead of mixing the colours, we 

 painted one half of each strip from centre to end red, and 

 the other half green, it is perfectly manifest that the 

 two strips would now behave towards each other exactly 

 as our two magnetised darning-needles the red end 

 would repel the red and attract the. green, the green would 

 repel the green and attract the red ; so that, assuming 

 two colours thus related to each other, we could by 

 their mixture produce the neutrality of an unmagnetised 

 body, while by their separation we could produce the 

 duality of action of magnetised bodies. 



But you have already anticipated a defect in my 

 conception ; for if we break one of our strips of wood 

 in the middle we have one half entirely red, and the 

 other entirely green, and with these it would be im- 

 possible to imitate the action of our broken magnet. 

 How, then, must we modify our conception ? We 

 must evidently suppose each molecule of the wood 

 painted green on one face ,and red on the opposite one. 

 The resultant action of all the atoms would then exactly 

 resemble the action of a magnet. Here also, if the two 

 opposite colours of each atom could be caused to mix 

 so as to produce white, we should have, as before, per- 

 fect neutrality. 



For these two self-repellent and mutually attractive 

 colours, substitute in your minds two invisible self- 

 repellent and mutually attractive fluids, which in ordi- 

 nary steel are mixed to form a neutral compound, but 

 which the act of magnetisation separates from each 

 other, placing the opposite fluids on the opposite face 



