64 PHYSICS 



and of least action, any single ether mechanism is possible, there 

 must at the same time be an infinity of others. 



The Electronic Theory 



The splendid triumph of the electronic theory is of quite recent 

 date, although Davy discovered the electric arc in 1821, and although 

 many experiments were made on the conduction of gases by Faraday 

 (1838), Reiss, Gassiot (1858, et seq.}, and others. The marvelous 

 progress which the subject has made begins with the observations 

 of the properties of the cathode ray by Pliicker and Hittorf (1868), 

 brilliantly substantiated and extended later by Crookes (1879). 

 Hertz (1892) and more specifically Lenard (1894) observed the pass- 

 age of the cathode rays into the atmosphere. Perrin (1895) showed 

 them to be negatively charged. Rontgen (1895) shattered them 

 against a solid obstacle, generating the X-ray. Goldstein (1886) 

 discovered the anodal rays. 



Schuster's (1890) original determination of the charge carried by 

 the ion per gram was soon followed by others utilizing both the elec- 

 trostatic and the magnetic deviation of the cathode torrent, and by 

 Lorentz (1895) using the Zeeman effect. J. J. Thomson (1898) suc- 

 ceeded in measuring the charge per corpuscle and its mass, and the 

 velocities following Thomson (1897) and Wiechert (1899), are known 

 under most varied conditions. 



But all this rapid advance, remarkable in itself, became startlingly 

 so when viewed correlatively with the new phenomena of radio- 

 activity, discovered by Becquerel (1896), wonderfully developed by 

 M. and Madame Curie (1898, et seq.}, by J. J. Thomson and his pupils, 

 particularly by Rutherford (1899, et seq.}. From the Curies came 

 radium (1898) and the thermal effect of radioactivity (1903), from 

 Thomson much of the philosophical prevision which revealed the 

 lines of simplicity and order in a bewildering chaos of facts, and 

 from Rutherford the brilliant demonstration of atomic disintegra- 

 tion (1903) which has become the immediate trust of the twentieth 

 century. Even if the ultimate significance of such profound re- 

 searches as Larmor's (1891) Ether and Matter cannot yet be dis- 

 cerned, the evidences of the transmutation of matter are assured, 

 and it is with these that the century will immediately have to reckon. 



The physical manifestations accompanying the breakdown of 

 atomic structure, astoundingly varied as these prove to be, assume 

 fundamental importance when it appears that the ultimate issue 

 involved is nothing less than a complete reconstruction of dynamics 

 on an electromagnetic basis. It is now confidently affirmed that the 

 mass of the electron is wholly of the nature of electromagnetic 

 inertia, and hence, as Abraham (1902), utilizing Kaufmann's data 



