ABSTRACT
The great question was at once settled, and the list of elements recognisable in the sun's envelope soon came to include not only sodium, but also iron, calcium. Kirchhoff may then be regarded as the father of astronomical spectroscopy. At the suggestion of Zollner, who had in the meantime devised his reversion spectroscope to double the effect to be measured, Professor Vogel of Bothkamp succeeded in applying the method to the sun's rotation. But the sun's rotation is only one of the problems to which the new method of research is applicable. The tendency of more modern research is to discredit the idea of dissociation by heat in favour of some radiative or electro-magnetic effect called 'ionisation'. Rowland's diffraction grating substitutes for the prism a reflecting surface ruled with a very large number of fine lines very close together, so that by the principle of interference duplicate rays are eliminated and a 'diffraction' spectrum produced.
