When all the stars blaze out on a clear, moonless night, it seems as if it would be impossible to count them; and yet it is seldom that more than 2,000 are visible together to the unaided eye. The number, however, depends very much upon climate and sharpness of sight. Argelander enumerated at Bonn, where rather more than eight-tenths of the sphere come successively into view, 3,237 stars. But of these no more than 2,000 could be, at any one time, above the horizon, and so many would not be visibly above it, owing to the quenching power of the air in its neighbourhood. Heis, at Münster, saw 1,445 stars more than Argelander at Bonn; Houzeau recorded 5,719 at Jamaica; Gould 10,649 at Cordoba in South America. The discrepancies of these figures, setting aside the comparatively slight effect of the increased area of the heavens displayed in low latitudes, are due to the multitude of small stars always, it might be said, hovering on the verge of visibility. If, indeed, the atmosphere could be wholly withdrawn, fully 25,000 stars would, according to a trustworthy estimate, become apparent to moderately good eyes.

Our system of designating the stars has come down to us from a hoar antiquity. It is a highly incommodious one. ‘The constellations,’ Sir John Herschel remarks, ‘seem to have been almost purposely named and delineated to cause as much confusion and inconvenience as possible.