At the head of these new discoveries and insights comes the establishment of the facts that electricity is composed of discrete particles of equal size, or quanta, and that light is an electromagnetic wave motion.

Moreover, the abundance of chemical compounds and their importance in daily life hindered the chemist from investigating the question, in what does the individuality of the atoms of different elements consist.

With this in mind, for some twenty years I have set myself as my particular task the experimental investigation of the connexion between change in the structure and change in the spectra of chemical atoms.

A beam of luminous hydrogen canal rays has, owing to its velocity, exactly the same direction as that of the electric field in which it may be made to move.

For under certain conditions the chemical atoms emit light waves of a specific length or oscillation frequency - their familiar characteristic spectra - and these can come in the form of electromagnetic waves only from accelerated electric quanta.

An external electric field, meeting it and passing through it, affects the negative as much as the positive quanta of the atom, and pushes the former to one side, and the latter in the other direction.

The question of the composition of perceptible objects is one which already occupied the mind of the ancient Greeks.