If the experimental physicist has already done a great deal of work in this field, nevertheless the theoretical physicist has still hardly begun to evaluate the experimental material which may lead him to conclusions about the structure of the atom.

The emitters of the spectral series are without exception single atoms, not compounds of atoms.

The discovery of various phenomena has led to a recognition of the fact that the chemical atom is an individual which again is itself made up of several units into a selfcontained whole.

In my view the structure of the whole atom was that of an individual, with all its parts interconnected, and the emission of a spectral line appeared to me to be the result of the coherence and co-operation of several electric quanta.

We have learnt through experience that when an electrical ray strikes the surface of an atom, an electron, and in some circumstances a second and even a third electron, can be detached.

By recognizing that the chemical atom is composed of single separable electric quanta, humanity has taken a great step forward in the investigation of the natural world.

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.

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.

We can in fact first place the beam of rays of moving positive atomic ions in a plane perpendicular to the axis in which we see the spectral lines emitted by them.

If the experimental physicist has already done a great deal of work in this field, nevertheless the theoretical physicist has still hardly begun to evaluate the experimental material which may lead him to conclusions about the structure of the atom.

Along a series of lines running from longer to shorter wavelengths the effect of the electric field becomes greater as the serial numbers increase – that is, as the wavelength decreases.

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.

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.

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.

It is more likely that more than a century will pass before we know the structure of the chemical atoms as thoroughly as we do our solar system.

The removal of an electron from the surface of an atom – that is, the ionization of the atom – means a fundamental structural change in its surface layer.

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.

The movement of the emitters of the spectral lines may be deduced on the basis of the Doppler principle.

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

The most common and most important result of them is that the nature and size of the effect on corresponding series of different elements are largely an expression of the peculiarity of their atomic structure – or, at least, of the structure of the surface.

Many scientists will have to contribute to the solution of the great problem; they will have to follow up and measure all those phenomena in which the atomic structure is directly expressed.

By allowing the positive ions to pass through an electric field and thus giving them a certain velocity, it is possible to distinguish them from the neutral, stationary atoms.

Thus at the beginning of 1906 it seemed to be established that the emitters of the spectral series of chemical elements are their positive atomic ions.