It is evident, on the most casual glance at the sky, that in the words of Scripture, 'One star differeth from another star in glory.' There are stars of every degree of brilliancy, from the sparkling white lustre of Sirius or Vega, down to the dim glimmer of those stars which are just on the edge of visibility, and are blotted out by the faintest wisp of haze. Accordingly, the stars have been divided into 'magnitudes' in terms of scales which, though arbitrary, are yet found to be of general convenience. Stars of the first six magnitudes come under the title of 'lucid' stars; below the sixth we come to the telescopic stars, none of which are visible to the naked eye, and which range down to the very last degree of faintness. Of stars of the first magnitude there are recognised about twenty, more or less. By far the brightest star visible to us in the Northern Hemisphere, though it is really below the Equator, is Sirius, whose brightness exceeds by no fewer than fourteen and a half times that of Regulus, the twentieth star on the list. The next brightest stars, Canopus and Alpha Centauri, are also Southern stars, and are not visible to us in middle latitudes. The three brightest of our truly Northern stars, Vega, Capella, and Arcturus, come immediately after Alpha Centauri, and opinions are much divided as to their relative brightness, their diversity in colour and in situation rendering a comparison somewhat difficult. The other conspicuous stars of the first magnitude visible in our latitudes are, in order of brightness, Rigel, Procyon, Altair, Betelgeux, Aldebaran, Pollux, Spica Virginis, Antares, Fomalhaut, Arided (Alpha Cygni), and Regulus, the well-known double star Castor following not far behind Regulus. The second magnitude embraces, according to Argelander, 65 stars; the third, 190; fourth, 425; fifth, 1,100; sixth, 3,200; while for the ninth magnitude the number leaps up to 142,000. It is thus seen that the number of stars increases with enormous rapidity as the smaller magnitudes come into question, and, according to Newcomb, there is no evidence of any falling off in the ratio of increase up to the tenth magnitude. In the smaller magnitudes, however, the ratio of increase does not maintain itself. The number of the stars, though very great, is not infinite.