[W/K] :: cathode rays

  Electron \E*lec"tron\, n. [NL., fr. Gr. 'h`lektron. See
     Electric.]
     1. Amber; also, the alloy of gold and silver, called
        electrum. [archaic]
        [1913 Webster]
  
     2. (Physics & Chem.) one of the fundamental subatomic
        particles, having a negative charge and about one
        thousandth the mass of a hydrogen atom. The electron
        carries (or is) a natural unit of negative electricity,
        equal to 3.4 x 10^{-10 electrostatic units, and is
        classed by physicists as a lepton. Its mass is
        practically constant at the lesser speeds, but increases
        due to relativistic effects as the velocity approaches
        that of light. Electrons are all of one kind, so far as is
        known. Thus far, no structure has been detected within an
        electron, and it is probably one of the ultimate composite
        constituents of all matter. An atom or group of atoms from
        which an electron has been detached has a positive charge
        and is called a cation. Electrons are projected from the
        cathode of vacuum tubes (including television picture
        tubes) as cathode rays and from radioactive substances
        as the beta rays. Previously also referred to as
        corpuscle, an obsolete term. The motion of electrons
        through metallic conductors is observed as an electric
        current. A particle identical to the electron in mass and
        most other respects, but having a positive instead of a
        negative charge, is called a positron, or antielectron
        [Webster 1913 Suppl. +PJC] Electro-negative