216 MODERN VIEWS ON MATTER. 



To treat the .subject properly, to give all the evidence as well as the 

 results, would need a volume, or a course of lectures; and in order to 

 be brief I must frequent!}" be dogmatic, l)ut I shall only intend to )>e 

 so in those places where I feel sure that the physicists present (whom 

 here I salute) will agree Avith me. When I have a dogma of this kind 

 to propound I shall call it a thesis. The more speculative opinions 1 

 sLall plainly denominate hypotheses. 



1. My first thesis is that an electric charge possesses the most fun- 

 damental and characteristic property of matter, viz, mass or inertia; 

 so that if anyone were to speak of a milligram or an ounce or a ton of 

 electricity, though he would certainly be speaking inconveniently, he 

 might not necessaril}' be speaking erroneously. At the same time it 

 would l)e well to mistrust anA'one who employed such a phrase, except 

 in speaking to experts. He would most likely be talking nonsense; but 

 if he talks nonsense to experts, his l)lood is on his own head. 



In order to have any appreciable mass, however, an electric charge 

 must either be extremely great or must be extremely concentratc^d, 

 and unless it is to be utterly masked by the matter with which it is 

 associated it must be the latter; that is to say, it must exist on bodies 

 of far less than ultra-microscopic size. The mass or inertia of a 

 charge depends upon two factors— the quantity of electricity in it, 

 and its potential — and by concentrating a given charge onto a suffi- 

 ciently small sphere the latter factor can be raised theoretically to 

 any value we please, and thus any required inertia can be ol)tained, 

 unless a stage is reached at which it becomes physically impossible to 

 concentrate it any more. 



•2. The next thesis is a very simple and familiar one, and dates 

 virtuall}' from the time of Faraday, though the conception has grad- 

 ually gained in clearness and solidity. It is that every atom of matter 

 can have associated with it a certain definite quantity of electricity 

 called the ionic charge; that some atoms can have double this quantity, 

 some treble, and so on, but that no atom or any piece of matter can 

 have a fraction of this cjuaRtity; which therefore appears to be an ulti- 

 mate unit, a sort of "atom," of electricity. The ratio of the charge to 

 the weight of a material atom is measured with accuracy in electrol- 

 ysis, in accordance with what are called Faraday's laws; and in so far 

 as the mass of the atom itself is otherwise approximately known the 

 quantity of electricit}' which can be associated with it is known with a 

 similar degree of approximate accuracy. 



3. Now, mathematical data were given by J. J. Thomson in 1881 

 which enable us to say that if the charge of electricity usually associ- 

 ated with a single monad atom of matter were concentrated on to a 

 spherical nucleus one hundred-thousandth of an atom's dimension 

 in diameter, it wouldthereby possess a mass about one-thousandth of 

 that of the lightest atom known, viz, the hydrogen atom. 



