Cathode j Lenard, and Rontyen Rays. 273 



of essentially the same nature as an atom. But further, if two 

 things attract one another, we must conceive the possibility 

 of their being drawn apart, so that the ion can be split into 

 an uncharged atom and an electron free of attachment to 

 matter. Maxwell's ascription of inertia to electricity, in 

 his theory of induced currents, bears out our conclusion that 

 the atom and the electron are things of the same sort in many 

 respects. If the electrons are distributed through the aether, 

 we must suppose that in aether showing no electric charge 

 each negative electron is united with a positive electron to 

 form the analogue of a material molecule, which might con- 

 veniently be called a neutron. Of the existence of neutrons 

 in the aether we have powerful evidence in Trowbridge's 

 wonderful experiments ( u The Electrical Conductivity of the 

 .Ether," Phil. Mag. [5] xliii., May 1897). He opens his 

 account of them with a mention of Edlund's old contention 

 that the aether is a conductor and J. J. Thomson's refutation 

 of it, and closes it with the statement, " My experiments lead 

 me to conclude that under very high electrical stress the 

 aether breaks down and becomes a good conductor." Thus both 

 Edlund's contention and J. J. Thomson's are happily recon- 

 ciled ; the aether is a perfect insulator until it is broken down, 

 after which it is a conductor. According to the present 

 theory, Trowbridge's result would be worded thus : — The 

 aether insulates until the electric force at some point is 

 sufficient to decompose the neutrons into electrons, where- 

 upon it becomes a conductor of the same type as electrolytes. 

 This principle should help practical electricians to construct 

 a consistent theory of the hitherto rather intractable electric 

 arc. 



But to return to the cathode rays. The volume of experi- 

 mental and theoretical work on the ionization of gases, which 

 has been turned out from the Cavendish Laboratory, leaves no 

 doubt as to the existence of ions in rare gases through which 

 a current of electricity is passing : hence in the cathode stream 

 there must be a certain number of ions flying along side by 

 side with the electrons; but the experiments of Thomson and 

 Kaufmann, according to our interpretation, prove that the 

 stream of ions is of quite subsidiary importance to the stream 

 of electrons. This is not always necessarily the case in the 

 electric discharge through gases, and it seems to me that, for 

 a satisfactory theory of the varied phenomena of electric 

 conduction through gases, we must take account of the fact 

 that we have two conducting media participating in the action 

 namely, varying numbers of ions and also of free electrons. 



Our theory of the cathode stream has the advantage that it 



