The Evolution of the Sciences 



breathe, water and alcohol in the wine which 

 we drink, so that we are incapable, by any logical 

 or experimental process, of defining a volume, be it 

 ever so small, which will contain oxygen without 

 nitrogen, or water without alcohol. On the 

 other hand, we can realise a space entirely void 

 of matter and yet practically impenetrable. Let 

 us imagine a powerful electro-magnet, with its 

 two iron poles placed a few centimetres apart. 

 Let us take a sword of the best and sharpest steel 

 and try to cleave this space, this field. We could 

 not succeed had we the strength of Samson, 

 and it is not the small quantity of air between the 

 poles that prevents us; we might remove it all, 

 and yet that field would remain equally impene- 

 trable to our sword. Better abandon as beyond 

 reason and experiment this ancient notion of 

 impenetrability, which is merely an heirloom of 

 Cartesian metaphysics and encumbers our 

 brains to no purpose. 



Let us also neglect all the properties of matter 

 which are not general or essential, in order to 

 attain our object. The different sciences, mathe- 

 matics, physics and chemistry, are agreed in 

 characterising matter by three fundamental pro- 



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