MODERN VIEWS ON MATTER. 239 



two-fluid theory of electricity is gradually replaced by the orig'inal 

 one-fluid theorj^ of Franklin. On the two-fluid theory the electrons 

 constitute free negatiye electricity and the rest of the chemical atom 

 is chai-ged positiyeh^, although a free positive electron is not known. 

 It seems to me simpler to use the original one-fluid theory of Franklin, 

 and to say that the electron is the atom or unit of electricity. Fleming 

 uses the word "coelectrons" to express the heavy positive ion after 

 separation from the negative electron, '"We can no more,'' he says, 

 "have anything which can be called electricity apart from corpuscles 

 than we can have momentum apart from moving matter." A so-called 

 negatively charged chemical atom is one having a surplus of electrons, 

 the number depending on the valency, whilst a positive ion is one hay- 

 ing a deficiency of electrons. Differences of electrical charge ma}^ thus 

 be likened to debits and credits in one's banking account, the electrons 

 acting as current coin of the realm. On this view only the electron 

 exists; it is the atom of electricity, and the words positive and negative, 

 signifying excess and defect of electrons, are only used for convenience 

 of old-fashioned nomenclature. 



The electron theory fits and luminously explains Ampere's idea that 

 magnetism is due to a rotating current of electricity round each atom 

 of iron; and following these definite views of the existence of free 

 electrons has arisen the electronic theory of matter. It is recognized 

 that electrons have the one property which has been regarded as 

 insepara])le from matter — nay, almost impossible to separate from our 

 conception of matter — I mean inertia. Now, in that remarkable 

 paper of J. J. Thomson's. pu])lished in 1881, he developed the idea of 

 electric inertia (self-induction) as a reality due to a moving charge. 

 The electron therefore appears only as apparent mass b}- reason of its 

 electro-dynamic properties, and if we consider all forms of matter to 

 be merely congeries of electrons the inertia of matter w^ould be 

 explained without any material basis. On this view the electron 

 would be the "protyle" of 188t), whose different groupings cause 

 the genesis of the elements. 



There is one more property of the emanations of radium to bring- 

 before 3"Our notice. I have shown that the electrons produce phos- 

 phorescence of a sensitive screen of barium platinocvanide and the 

 positive ions of radium produce phosphorescence of a screen of zinc 

 blende. 



If a few minute grains of radium salt fall on the zinc-sulphide screen 

 the surface is immediately dotted with brilliant specks of green light. 

 In a dark room, under a microscope with a |-inch objective, each 

 luminous spot shows a dull center sui-rounded l)y a difl'used luminous 

 halo. Outside the halo the dai'k surface of the screen scintillates with 

 sparks of light. No two flashes succeed on the same spot, but arc 



]7;5 



