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

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.

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.

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.

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.

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.

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.