These facts tend to confirm the conclusion--so often advocated in this book--that the ancestors of the Egyptians, as also of all the great civilized nations of antiquity, followed through many long ages the same sidereal calendar--one based on the observation of the colures amongst the fixed stars 6000 B.C. And it would seem that not till about 4000 B.C., when the colures had traversed, from east to west, the constellations Pisces, Gemini, Virgo, and Sagittarius, and had arrived at the eastern degrees of Aquarius, Taurus, Leo, and Scorpio, did astronomic authorities in Egypt direct their attention to a reform of the calendar and introduce into it, and into religious observances, references to these four last-named constellations. Turning to Plate XVI. we may notice that the equinoctial colure, marking out as it does the extreme western limits of the constellation Cancer, passes also through a part of the constellation Gemini. This fact may, I think, help to explain some of the legends connected with the twins Castor and Pollux in ancient lore. A very brilliant star glitters on the head of each twin. These stars are of almost equal lustre and well deserve the name of twin stars; and so we can easily suppose how it was that the imaginative astronomers who, at the early date in question, mapped out the figures of the Zodiac, noticing that the equinoctial colure passed between these two bright stars, should have elected to represent them as marking the heads of twin figures, which they determined should symbolize the _equal day and night_ of the season over which they presided. These two stars, thousands of years after they had ceased to mark the equinox, were still associated by the Greeks with the twin heroes--Castor and Pollux--brothers who, according to the legend, were “possessed of an immortality of existence so divided among them, that as one dies, the other revives.” The learned Dr Barrett has pointed out that “this furnishes a complete description of Day and Night.” This remark of Dr Barrett’s becomes especially interesting if we attribute the first symbolizing of day and night by these stars to the work of astronomers at a date when the day and night these stars symbolized were of exactly equal length, and when, therefore, the equal stars and equal alternation of light and darkness might both be fitly symbolized as twins. At Plate XVIII. it is to be observed that the equinoctial colure, instead of adjoining Capricornus, occupies an almost central position in the preceding constellation, Sagittarius. This fact, together with other considerations, has led me to think that originally only the bow and arrow of Sagittarius were imagined for that division of the ecliptic; and that the huge composite figure of the archer--half man and half horse--was added to the original design in later ages, by astronomers who chose the spring equinox instead of the winter solstice for the beginning of the year.