A set of twenty-eight rhymes associated their heliacal risings with the changes of season and the vicissitudes of nomad life; their settings were of meteorological and astrological import; 3 in the Koran (x.
Nominally the beginning Df the rise of the Nile, was the beginning of the year, and as the ~ile commences to rise very regularly at about the date of the annual heliacal rising of the conspicuous dog-star Sothis (Sirius~ (which itself follows extremely closely the slow retrogression af the Julian year), the primitive astronomers found in the heliacal rising of Sothis as observed at Memphis (on July 9 Julian) a very correct and useful, starting-point for the seasonal year.
(4) Astronomical data, especially the heliacal risings of Sothis recorded by dates of their celebration in the vague year.
The importance of their heliacal risings, or first visible appearances at dawn, for the purposes both of practical life and of ritual observance, caused them to be systematically noted; the length of the year was accurately fixed in connexion with the annually recurring Nile-flood; while the curiously precise orientation of the Pyramids affords a lasting demonstration of the high degree of technical skill in watching the heavens attained in the third millennium B.C. The constellational system in vogue among the Egyptians appears to have been essentially of native origin; but they contributed little or nothing to the genuine progress of astronomy.
In the Ephemerides published year by year, the times of new moon were given, together with the calculated intervals to the first visibility of the crescent, from which the beginning of each month was reckoned; the dates and circumstances of solar and lunar eclipses were predicted; and due information was supplied as to the forthcoming heliacal risings and settings, conjunctions and oppositions of the planets.