My object in the above discussion of the origin of the week (as distinguished from the origin of the Sabbath, which I considered in the essay on astrology), has been to show that the use of the twelve zodiacal signs was in every case preceded by the use of the twenty-eight lunar mansions. It has been supposed that those nations in whose astronomy the twenty-eight mansions still appear, adopted one system, while the use of the twelve signs implies that another system had been adopted. Thus the following passage occurs in Mr. Blake's version of Flammarion's 'History of the Heavens:'--'the Chinese have twenty-eight constellations, though the word _sion_ does not mean a group of stars, but simply a mansion or hotel. In the Coptic and ancient Egyptian the word for constellations has the same meaning. They also have twenty-eight, and the same number is found among the Arabians, Persians, and Indians. Among the Chaldæans or Accadians we find no sign of the number twenty-eight. The ecliptic, or "yoke of the sky," with them, as we see in the newly-discovered tablet, was divided into twelve divisions, as now, and the only connection that can be imagined between this and the twenty-eight is the opinion of M. Biot, who thinks that the Chinese had originally only twenty-four mansions, four more being added by Chenkung, 1100 B.C., and that they corresponded with the twenty-four stars, twelve to the north and twelve to the south, that marked the twelve signs of the zodiac amongst the Chaldæans. But under this supposition the twenty-eight has no reference to the moon, whereas we have every reason to believe it has.' The last observation is undoubtedly correct--the twenty-eight mansions have been mansions of the moon from the beginning. But in this very circumstance, as also in the very tablets referred to in the preceding passage, we find all the evidence needed to show that originally the Chaldæans divided the zodiac into twenty-eight parts. For we find from the tablets that, like the other nations who had twenty-eight zodiacal mansions, the Chaldæans used a seven-day period, derived from the moon's motions, every seventh day being called _sabbatu_, and held as a day of rest. We may safely infer that the Chaldæan astronomers, advancing beyond those of other nations, recognised the necessity of dividing the zodiac with reference to the sun's motions instead of the moon's. They therefore discarded the twenty-eight lunar mansions, and adopted instead twelve solar signs; this number twelve, like the number twenty-eight itself, being selected merely as the most convenient approximation to the number of parts into which the zodiac was naturally divided by another period. Thus the twenty-eighth part of the zodiac corresponds roughly with the moon's daily motion, and the twelfth part of the zodiac corresponds roughly with the moon's monthly motion; and both the numbers twenty-eight and twelve admit of being subdivided, while twenty-nine (a nearer approach