June 26, 1903.] 



SCIENCE. 



1001 



ionization is communicated to gases faintly 

 by the splashing of water, by flames and 

 red-hot bodies, by ultra-violet light falling 

 on negatively electrified metals, and strong- 

 ly by the passage of Rontgen rays. 



According to Sir Oliver Lodge's elec- 

 tronic theory of matter, a chemical atom 

 or ion has a few extra negative electrons 

 in addition to the ordinary neutral atom, 

 and if these negative electrons are re- 

 moved it thereby becomes positively 

 charged. The free electron portion of the 

 atom is small in comparison with the main 

 bulk, in the proportion in hydrogen of 

 about 1 to 700. The negative charge con- 

 sists of superadded or unbalanced elec- 

 trons—one, two, three, etc., according to 

 the chemical valency of the body — whereas 

 the main bulk of the atom consists of 

 paired groups, equal positive and negative. 

 As soon as the excess electrons are re- 

 moved, the rest of the atom, or ion, acts as 

 a massive positively charged body, hanging 

 tightly together. In a high vacuum the 

 induction spark tears the components of 

 a rarefied gas apart ; the positively charged 

 ions, having great comparative density are 

 soon slowed down by collisions, while the 

 electrons are driven from the negative pole 

 with an enormous velocity depending on 

 the initial electromotive force and the pres- 

 sure of gas inside the tube, but approach- 

 ing, at the highest exhaustions, half that 

 of light. 



After leaving the negative pole the elec- 

 trons meet with a certain resistance, in a 

 slight degree by physical collisions, but 

 principally by reunion with the positive 

 ions. 



Since the discovery of radium and the 

 identification of one set of its emanations 

 with the cathode stream or radiant matter 

 of the vacuum tube, speculation and ex- 

 periment have gone hand in hand, and the 

 two-fiuid theory of electricity is gradually 



replaced by the original one-fluid theory 

 of Franklin. On the two-fluid theory, the 

 electrons constitute free negative elec- 

 tricity, and the rest of the chemical atom 

 is charged positively, although a free posi- 

 tive 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. Flem- 

 ing uses the word 'co-electrons' 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 having 

 a deficiency of electrons. Differences of 

 electrical charge may 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 ex- 

 ists ; it is the atom of electricity, and the 

 words positive and negative, signifying ex- 

 cess and defect of electrons, are only used 

 for convenience of old-fashioned nomen- 

 clature. 



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 re- 

 garded as inseparable from matter — nay, 

 almost impossible to separate from our con- 

 ception of matter — I mean inertia. Now, 

 in that remarkable paper of J. J. Thom- 

 son's piiblished 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 



