We have seen above numerous applications of the Doppler effect.
The conclusion seemed natural that the spectra which showed the Doppler effect were due to vibratory systems which had an excess of positive charge.
The principle that the refrangibility of light is altered by endon motion was enunciated by Christian Doppler of Prague in 1842.
We have first the Doppler effect, which, according to Michelson's experiment, is the chief cause of the limit at very low pressures, but it is too small to account for the widening which is now under discussion.
Dorn 5 has found the Doppler effect with a number of lines of helium, which contain representatives of the trunk series as well as of the two branch series.