But there is one thing in our modern timekeeping which we still have in common with the first men who ever kept the time. We still go by the sun and the stars and refer all our measure to that apparent revolution of the heavens which we know to be really the motion of our world itself. As did those wise men of old Babylon, so do we even now, spying upon the mighty master clock of the universe to correct all our little timepieces thereby. A man sits alone in an observatory, with his eye to a telescope. That telescope is of a certain kind, called a "transit." It is fixed upon the meridian, the north-and-south line in the sky over that place. And a thread of spider-web across the lens marks for him the exact position of the line, in the very middle of his field of view. So as he watches, he can see one star after another come into view at one side of the glass and pass across it to the other side and disappear. He is watching the world go round. A certain star appears, one which his calculations have told him will cross the meridian at a certain particular instant. Beside him is an electrical device connected with a clock, which marks off seconds at intervals round a revolving drum. The star draws nearer to the center of his field. As it crosses the hair-line, the observer touches a key, and the precise instant of its crossing is recorded upon the drum, to within a fraction of a second. Since the clock has marked its record of the seconds there, the clock can be corrected by the star. Now, if that man had been a priest in Babylon, he would have kept his knowledge as a means of power to himself and to his equals. If he had been a dweller in a somewhat later age, he would have kept it to himself no less, either because people would not believe, or because the claim of too deep knowledge of the secrets of nature might put his life in danger. But he is a modern, and so his knowledge is for all who seek it. On some tall building in a distant city, a time-ball hangs suspended at the top of its pole, and people pause to look up at it. They hold their watches in their hands. Upon the tick of noon, an impulse will come from the observatory, and the ball will drop. Then those who have been looking will set the hands of their watches and pass on. At the same instant, the news of noon will be flashed by telegraph across the land, and by wireless to ships at sea. The whole Western Union system will suspend business for a little, while the lines are connected and the observatory at Washington ticks off the seconds. Everywhere there are electric clocks, automatically controlled by some master clock, which, in its turn is governed by the observatory time. So we all, as a matter of course and without thinking, set our watches by the star. Civilization every day catches step with the heavenly bodies.