(M29) And the sign of the rising waters on earth was accompanied by a sign in heaven. For in the early days of Egyptian history, some three or four thousand years before the beginning of our era, the splendid star of Sirius, the brightest of all the fixed stars, appeared at dawn in the east just before sunrise about the time of the summer solstice, when the Nile begins to rise.(67) The Egyptians called it Sothis, and regarded it as the star of Isis,(68) just as the Babylonians deemed the planet Venus the star of Astarte. To both peoples apparently the brilliant luminary in the morning sky seemed the goddess of life and love come to mourn her departed lover or spouse and to wake him from the dead. Hence the rising of Sirius marked the beginning of the sacred Egyptian year,(69) and was regularly celebrated by a festival which did not shift with the shifting official year.(70) The first day of the first month Thoth was theoretically supposed to date from the heliacal rising of the bright star, and in all probability it really did so when the official or civil year of three hundred and sixty-five days was first instituted. But the miscalculation which has been already explained(71) had the effect of making the star to shift its place in the calendar by one day in four years. Thus if Sirius rose on the first of Thoth in one year, it would rise on the second of Thoth four years afterwards, on the third of Thoth eight years afterwards, and so on until after the lapse of a Siriac or Sothic period of fourteen hundred and sixty solar years the first of Thoth again coincided with the heliacal rising of Sirius.(72) This observation of the gradual displacement of the star in the calendar has been of the utmost importance for the progress of astronomy, since it led the Egyptians directly to the determination of the approximately true length of the solar year and thus laid the basis of our modern calendar; for the Julian calendar, which we owe to Caesar, was founded on the Egyptian theory, though not on the Egyptian practice.(73) It was therefore a fortunate moment for the world when some pious Egyptian, thousands of years ago, identified for the first time the bright star of Sirius with his goddess; for the identification induced his countrymen to regard the heavenly body with an attention which they would never have paid to it if they had known it to be nothing but a world vastly greater than our own and separated from it by an inconceivable, if not immeasurable, abyss of space.