Formerly the sparkand absorption-spectra were the sole methods available; a third method was introduced by Crookes, who submitted the oxides, or preferably the basic sulphates, to the action of a negative electric discharge in vacuo, and investigated the phosphorescence induced spectroscopically.
Hartwig in 1885, and subsequently spectroscopically examined by many observers; R Andromedae, a regularly variable star; and the Andromedids, a meteoric swarm, associated with Biela's comet, and having their radiant in this constellation (see Meteor).
He employed in his discussion the radial velocities of 280 stars, spectroscopically determined; and the upshot signally exemplified the community of interests between the rising science of astrophysics and the ancient science of astrometry.