Dr. Anderson followed up his first achievement by the discovery of a brilliant Nova in the constellation Perseus. The discovery was made on the night of February 21-22, 1901, the star being then of magnitude 2·7. Within two days it became about the third brightest star in the sky, being a little more brilliant than Capella; but before the middle of April it had sunk to fifth magnitude. The rapidity of its rise must have been phenomenal! A plate exposed at Harvard on February 19, and showing stars to the eleventh magnitude, bore no trace of the Nova. 'It must therefore,' says Newcomb, 'have risen from some magnitude below the eleventh to the first within about three days. This difference corresponds to an increase of the light ten thousandfold!' Such a statement leaves the mind simply appalled before the spectacle of a cataclysm so infinitely transcending the very wildest dreams of fancy. Subsequent observations have shown the usual tendency towards development into a nebula, and in August, 1901, photographs were actually obtained of a nebulosity round the star, showing remarkable condensations. These photographs, taken at Yerkes Observatory, when compared with others taken at Mount Hamilton in November, revealed the startling fact that the condensations of the nebula were apparently in extraordinarily rapid motion. Now the Nova shows no appreciable parallax, or in other words is so distant that its distance cannot be measured; on what scale, therefore, must these motions have been to be recorded plainly across a gulf measurable perhaps in hundreds of light years! Nova Geminorum, discovered by Professor Turner, at Oxford, in March, 1903, had not the striking features which lent so much interest to Nova Persei. It showed a crimson colour, and its spectrum indicated the presence in its blaze of hydrogen and helium; but it faded so rapidly as to show that the disturbance affected a comparatively small body, and it has exhibited the familiar new star change into a nebula. One point with regard to the Novæ in Auriga and Perseus deserves notice. These discoveries, so remarkable in themselves, and so fruitful in the extension of our knowledge, were made by an amateur observer with no greater equipment than a small pocket telescope and a Klein's Star-Atlas. The thorough knowledge of the face of the heavens which enabled Dr. Anderson to pick out the faint glimmer of Nova Aurigæ and to be certain that the star was a new one is not in the least unattainable by anyone who cares to give time and patience to its acquisition; and even should the study never be rewarded by a capture so dramatic as that of Nova Persei, the familiarity gained in its course with the beauty and wonder of the star-sphere will in itself be an ample reward. CHAPTER XV CLUSTERS AND NEBULÆ