This star, important less from its brightness than from its position, lies close to that very spot in the heavens where the celestial North Pole passes. It is called the Pole-star. Night after night, through the year, it there remains, all but motionless, never going below the horizon for us in the northern hemisphere, or northern half of the earth; never rising above the horizon for those in the southern hemisphere. It shines ever softly and steadily in its fixed position. If you travel further south, the Pole-star sinks downward towards the horizon. If you travel further north, the Pole-star rises higher above the horizon. If you were at the North Pole, you would see the Pole-star exactly overhead. [Illustration: CONSTELLATION OF THE GREAT BEAR.] Very near the Pole-star is the constellation of the Great Bear, with Cassiopeia nearly opposite on the other side of the Little Bear, and other groups between the two, completing the circle. These constellations do not, to us who live in the northern hemisphere, rise or set; for they simply move in a circle round and round the Pole-star, never going below the horizon. All day and all night long this circling movement continues, though only visible at night. It is caused entirely by the earth’s own motion on her axis. [Illustration: THE GREAT BEAR 50,000 YEARS AGO.] [Illustration: THE GREAT BEAR 50,000 YEARS HENCE.] Lower down, or rather further off from the Pole-star, comes another ring of constellations. These in just the same manner appear to travel round and round the Pole-star. But being further away, each dips in turn below the horizon--or, as we call it, each sets and rises again. And by the time we come to yet another circle of leading constellations, we reach those which are so far affected by the earth’s yearly journey as to be only visible through certain months, and to be hidden during other months. [Illustration: CONSTELLATION OF ORION, AS IT APPEARS NOW.] If we could stand exactly at the North Pole, during part of its six months’ night, we should see the Pole-star just overhead, and all the constellations circling round it once in every twenty-four hours. Those nearest would move slowly, in a small ring. Those furthest, and lowest down, would in the same length of time sweep round the whole horizon. But the stars would not there seem to rise or set. If we were standing at the South Pole, we should see exactly the same kind of seeming movement, only with altogether a different set of stars. If we were standing on the Equator at night, we should see the rising and setting very plainly. The whole mass of stars would appear to rise regularly and evenly in an easterly direction, to pass steadily across the sky, each taking its own straightforward path, and to set in a westerly direction.