Among the more philosophical articles of this creed, astronomy assumed a prominent place from a very early date. The sun, it is true, was described in the original Cosmogony as having been called into existence by the word of the Supreme God, but it came to be taken as his visible representative, and finally worshipped as a god itself. Its different phases were studied and received different names, as Horus when on the horizon rising or setting, Ra in its midday splendour, Osiris during its journey in the night through the underground world of darkness. Of these Ra naturally had the pre-eminence; the title of Pharaoh, or Pi-ra, was that given to kings, who were assumed to be semi-divine beings descended from the Sun. The Osiris myth which was the basis of the national belief in a future life and day of judgment was clearly solar. Egyptian astronomy, like that of the Chaldees and all early nations, assumed that the sky was a crystal dome or firmament which separated the waters of the upper world from the earth and waters below, and corresponded with a similar nether world of darkness below the earth. The Sun was born or rose into the upper world every morning, waxed in strength and glory as his bark navigated the upper waters until noon, then declined and finally sank into the nether world or died, slain by an envious Typhon, but to be born again next morning after traversing the perils and encountering the demons of the realm of darkness. The same idea was repeated by the annual course of the sun through Spring, Summer, Autumn, and Winter, and it translated itself as applied to man into the ideas of birth, growth, manhood, decline, and death, to be followed by a sojourn in Hades, a day of judgment, and a resurrection. The Egyptian religion, however, seems never to have been so largely astronomical as that of Chaldæa, and to have concentrated itself mainly on the Sun. The planets and signs of the zodiac did not, as with the Chaldees, afford a principal element of their sacred books and mythologies. The Egyptian priests had doubtless long studied astronomy; they had watched the stars, traced the annual course of the sun, divided the year into months and the circle into 360°, and constructed calendars for bringing the civil into correspondence with the sidereal year. They not only had intercalated the five supplemental days, bringing the duration of the year from 360 to 365, but they had invented a sothic cycle for the odd quarter of a day, by which at the end of every 1460 years a year was added, and the sun brought back to rise on the first day of the first month of Thoth in the same place in the heavens, determined by the heliacal risings of the brightest of the stars, Sothis or Sirius.