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.

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 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.

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

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

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.

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