138 THE LIMITATIONS OF SCIENCE 



measure the amount concerned, provide us with un- 

 equal quantities of matter, just as conversely equal 

 quantities of matter might show different quantities 

 of electricity. The hypothesis of equivalence of elec- 

 trical charge and matter rests solely on an analogy to 

 electrolysis, where matter is in a quite different state 

 and also where the equivalence may be only approxi- 

 mate. Matter, on the other hand, in a solid state shows 

 no connection between volume and density and elec- 

 trical charge. In dealing with electricity we should not 

 forget the immense superiority of electrical detectors 

 in delicacy to those for mechanical quantities, so that 

 we can appreciate far smaller quantities of electrified 

 than of neutral bodies. 



There is no doubt, from the quotations given, that 

 theorists are basing their work on the assumption of 

 the electron as the unit of matter. And they give to it 

 the following properties: Its mass is wholly electro- 

 magnetic; the motive forces are electric forces; and 

 the laws of mechanics are to be deduced from the laws 

 of electro-magnetism. 



At first sight, it would seem to be a simple matter to 

 devise an experiment which would decide whether the 

 mass or the electrical charge of matter is constant. 

 But so far these two quantities have not only been 

 found to be inseparable but they invariably enter as a 

 simple ratio, whose value decreases with increasing 

 velocity. Such a relation can, of course, be satisfied 



