emical elements
successively were precipitated.

From another side too, suggestions were put forward by Sir Norman
Lockyer and others that the differences in spectra observed in
different classes of stars, and produced by different conditions in
the laboratory, were to be explained by changes in the structure of the
vibrating atoms.

The next step in advance gave a theoretical basis for the idea of a
common structure of matter, and was taken in an unexpected direction.
Clerk Maxwell's electromagnetic theory of light, accepted in England,
was driven home to continental minds by the confirmatory experiments of
Hertz, who in 1888 detected and measured the electromagnetic waves
that Maxwell had described twenty years earlier. But, if light be an
electromagnetic phenomenon, the light waves radiated by hot bodies must
take their origin in the vibrations of electric systems. Hence within
the atoms must exist electric charges capable of vibration. On these
lines Lorentz and Larmor have developed an electronic theory of matter,
which is imagined in its essence to be a conglomerate of electric
charges, with electro-magnetic inertia to explain mechanical inertia.
(Larmor, "Aether and Matter", Cambridge, 1900.) The movement of electric
charges would be affected by a magnetic field, and hence the discovery
by Zeeman that the spectral lines of sodium were doubled by a strong
magnetic force gave confirmatory evidence to the theory of electrons.

Then came J.J. Thomson's great discovery of minute particles, much
smaller than any chemical atom, forming a common constituent of many
different kinds of matter. (Thomson, "Conduction of Electricity through
Gases" (2nd edition), Cambridge, 1906.) If an electric discharge be
passed between metallic terminals through a glass vessel containing
air at very low pressure, it is found that rectilinear rays, known
as cathode rays, proceed from the surface of the cathode or negative
terminal. Where these rays strike solid objects, they give rise to
the Rontgen rays now so well known; but it is with the cathode rays
themselves that we are concerned. When they strike an insulated
conductor, they impart to it a negative charge, and Thomson found that
they were deflected from their path both by magnetic and electric forces
in the direction in which negatively electrified particles would be
deflected. Cathode rays then were accepted as flights of negatively
charged particles, moving with high velocities