122 Journal of the Mitchell Society [Jan. 



tive electricity consists of particles or corpuscles. The prepond- 

 erance of evidence seems to be in favor of this view, though it 

 is still rejected by some of the foremost men in electrical science. 



The second step is to connect this vv^ith the atom. The 

 electro-chemical theory, Faraday's law, complexity of spectra, 

 etc., lend their support, but the strongest confirmation comes 

 from the production of streams of electrons in the disintegra- 

 tion of radio-active atoms. 



The electron, according to the calculations of Thomson, has a 

 diameter of 10^^ ; that assigned the atom and the mass of the 

 electron would be about one-thousandth that of a hydrogen atom. 

 The original theory of Thomson held that the hydrogen atom 

 with a diameter of 10~^ cm. was entirely made up of electrons. 

 In the production of an atom the rotating electrons arrange 

 themselves in a number of concentric shells. The number of 

 electrons in such ring and the number of rings necessary to 

 insure the stability of the atom have been calculated. The 

 radiation of energy by the electrons must be small if the atom is 

 to remain stable. The radiation diminishes rapidly with the 

 number of electrons in the ring and with their velocity. With 

 a velocity one-hundreth that of light, the amount of radiation 

 of a symmetrical group of six electrons is one 10~-^^ that of a 

 single electron moving with the same velocity in the same orbit. 

 And yet this continuous drain must end either in a rearrange- 

 ment or in an expulsion of electrons from the atom. 



At first the whole mass of the atom was supposed to be made 

 up of electrons and the number of these to be large. Later 

 Thomson showed that the number of electrons was about three 

 times the atomic weight. In such case only a minute fraction 

 of the mass could be made up of electrons. 



. In summing up the account of the hypothesis, it is sufficient 

 to state, as Rutherford does, that the evidence for the existence 

 of electrons and that these are a universal constituent of atoms 

 is strong, but that the atoms are entirely composed of electrons 

 has little positive evidence for and much against it. 



In 1904 (Phil. Mag. [6] -7-237), Thomson states his view 

 that the atoms of the elements consist of a number of negatively 



