The zodiacal twelve are in some respects the most important and interesting of all the ancient constellations. If we could determine the origin of these figures, their exact configuration as at first devised, and the precise influences assigned to them in the old astrological systems, we should have obtained important evidence as to the origin of astronomy itself. Not indeed that the twelve signs of the zodiac were formed at the beginning or even in the early infancy of astronomy. It seems abundantly clear that the division of the zodiac (which includes the moon's track as well as the sun's) had reference originally to the moon's motions. She circuits the star-sphere in about twenty-seven days and a third, while the lunation or interval from new moon to new moon is, as we all know, about twenty-nine days and a half in length. It would appear that the earliest astronomers, who were of course astrologers also, of all nations--the Indian, Egyptian, Chinese, Persian, and Chaldæan astronomers--adopted twenty-eight days (probably as a rough mean between the two periods just named) for their chief lunar period, and divided the moon's track round the ecliptic into twenty-eight portions or mansions. How they managed about the fractions of days outstanding--whether the common lunation was considered or the moon's motion round the star-sphere--is not known. The very circumstance, however, that they were for a long time content with their twenty-eight lunar mansions shows that they did not seek great precision at first. Doubtless they employed some rough system of 'leap-months' by which, as occasion required, the progress of the month was reconciled with the progress of the moon, just as by our leap-years the progress of the year is reconciled with the progress of the sun or seasons.