A general acquaintance with the stars will be first attempted; a more particular knowledge afterward.  Fig. 67 (page 201) is a map of the circumpolar region, which is in full view every clear night.  It revolves daily round Polaris, its central point.  Toward this star, the two end stars of the Great Dipper ever point, and are in consequence called “the Pointers.”  The map may be held toward the northern sky in such a position as the stars may happen to be.  The Great Bear, or Dipper, will be seen at nine o’clock in the evening above the pole in April and May; west of the pole, the Pointers downward, in July and August; close to the north horizon in October and November; and east of the pole the Pointers highest, in January and February.  The names of such constantly visible stars should be familiar.  In order, from the end of the tail of the Great Bear, we have Benetnasch ae, Mizar z, Little Alcor close to it, [Page 198] Alioth, e Megrez, d at the junction, has been growing dimmer for a century, Phad, g Dubhe and Merak.  It is best to get some facility at estimating distances in degrees.  Dubhe and Merak, “the Pointers,” are five degrees apart.  Eighteen degrees forward of Dubhe is the Bear’s nose; and three pairs of stars, fifteen degrees apart, show the position of the Bear’s three feet.  Follow “the Pointers” twenty-nine degrees from Dubhe, and we come to the pole-star.  This star is double, made of two suns, both appearing as one to the naked eye.  It is a test of an excellent three-inch telescope to resolve it into two.  Three stars beside it make the curved-up handle of the Little Dipper of Ursa Minor.  Between the two Bears, thirteen degrees from Megrez, and eleven degrees from Mizar, are two stars in the tail of the Dragon, which curves about to appropriate all the stars not otherwise assigned.  Follow a curve of fifteen stars, doubling back to a quadrangle from five to three degrees on a side, and thirty-five degrees from the pole, for his head.  His tongue runs out to a star four degrees in front.  We shall find, hereafter, that the foot of Hercules stands on this head.  This is the Dragon slain by Cadmus, and whose teeth produced such a crop of sanguinary men.

The star Thuban was once the pole-star.  In the year B.C. 2300 it was ten times nearer the pole than Polaris is now.  In the year A.D. 2100 the pole will be within 30’ of Polaris; in A.D. 7500, it will be at a of Cepheus; in A.D. 13,500, within 7 deg. of Vega; in A.D. 15,700, at the star in the tongue of Draco; in A.D. 23,000, at Thuban; in A.D. 28,000, back to Polaris.  This indicates no change in the position of the dome [Page 199] of stars, but a change in the direction of the axis of the earth pointing to these various places as the cycles pass.  As the earth goes round its orbit, the axis, maintaining nearly the same direction, really points to every part of a circle near the north star as large as the earth’s orbit, that is, 185,000,000 miles in diameter.  But, as already shown, that circle is too small to be discernible at our distance.  The wide circle of the pole through the ages is really made up of the interlaced curves of the annual curves continued through 25,870 years.  The stem of the spinning top wavers, describes a circle, and finally falls; the axis of the spinning earth wavers, describes a circle of nearly 28,000 years, and never falls.