ing a maximum of light. Considered from this point of view, these novæ, as they are termed, can not correctly, perhaps, be classed among the variable stars at all. They appear once only, and then die out, never to return; at least, no return of a true nova has yet been recorded.
A remarkable peculiarity about these temporary stars is their usually sudden appearance. In all the well-authenticated cases the stars have blazed out with startling rapidity. Such were the brilliant stars of 1572 and 1604; and in later years, those of 1866 in Corona Borealis, and of 1876 in Cygnus. Tycho Brahe's star of 1572 made its appearance near the star Kappa Cassiopeiæ, the faintest of the four stars forming the well-known square in Cassiopeia's Chair. It appears to have been first noticed by Cornelius Gemma, on November 9th of that year, and it seems to have blazed out very suddenly, as he states that it was not visible on the preceding evening in a clear sky. The attention of Tycho Brahe, whose name is generally associated with the star, seems to have been first attracted to it on November 11th. When first seen, it surpassed Jupiter and rivaled Venus in brightness, and was visible at noonday! At this brilliancy, however, it did not long remain, but gradually diminished in luster, and in March, 1574, had completely disappeared, at least to the naked eye. Its curious changes are thus described: "As it decreased in size, so it varied in color; at first its light was white and extremely bright; it then became yellowish, afterward of a ruddy color, and finished with a pale livid color." Tycho Brahe has left an elaborate record of his observations of this wonderful object in a work of no less than 478 pages of printed matter.
"Kepler's nova" of 1604 appeared in the constellation Ophiuchus in October of that year. The planets Mars, Jupiter, and Saturn were near each other in this region of the heavens, near Eta Ophiuchi, and one evening Brunowski, a pupil of Kepler's, remarked that a new and very brilliant star had joined the planetary group. When first seen the new star was white, and exceeded in brilliancy Mars and Jupiter, and was even thought to rival Venus in splendor. It gradually diminished, and in six months was not equal in brightness to Saturn. In March, 1606, it had disappeared. It was also observed by the famous Galileo. Kepler wrote a work on the subject, which is still preserved. Only faint stars are now visible with the telescope near the positions assigned to these bright stars of 1572 and 1604.
In 1670 a star of the third magnitude was observed by Anthelm near Beta Cygni. It remained visible for about two years, and increased and diminished several times before its final disappearance.
A small temporary star was observed by Dr. Hind in Ophiu-