An interesting point connected with this is that, among these ancient peoples, the celestial bodies which gave them the unit period of time by which they reckoned were practically looked upon in the same category. Thus, for instance, in Egypt the sun being used, the unit of time was a year; but in Babylonia the unit of time was a month, for the reason that the standard of time was the moon. Hence, when periods of time were in question, it was quite easy for one nation to conceive that the period of time used in another was a year when really it was a month, and _vice versâ_. It has been suggested that the years of Methuselah and other persons who are stated to have lived a considerable number of years were not solar years but lunar years--that is, properly, lunar months This is reasonable, since, if we divide the numbers by twelve, we find that they come out very much the same length as lives are in the present day, and there is no reason why this should not be so. There seems little doubt that the country in which the sun was definitely accepted as the most accurate measurer of time was Egypt. Rā, the sun, was the chief god of ancient Egypt. He was worshipped throughout the various nomes. Even the oldest texts (_cf._ that of Menkaurā in the British Museum) tell of the brilliant course of Rā across the celestial vault and his daily struggle with darkness. "The Egyptians," says Ranke in the first chapter of his "Universal History," which is devoted to Egypt, "have determined the motion of the sun as seen on earth, and according to this the year was divided, in comparison with Babylon, in a scientific and practically useful way, so that Julius Cæsar adopted the calendar from the Egyptians and introduced it into the Roman Empire. The other nations followed suit, and since then it has been in general use for seventeen centuries. The calendar may be considered as the noblest relic of the most ancient times which has influenced the world." [Illustration: THE ANNUAL RISE AND FALL OF THE NILE. (_From Horner._)] Wherever the ancient Egyptians came from--whether from a region where the moon was the time-measurer or not--so soon as they settled in the valley where the Nile then, as now, like a pendulum slowly beat the years by its annual inundation at the Summer Solstice, the solar basis of their calendar was settled. Hence it was Nature, the Nile--on the regulation of which depended the welfare of the country--which facilitated the establishment of the Egyptian year. Solstice and Nile-flood are the turning-points of the old Egyptian year.