They divided the equator into three hundred and sixty degrees and they divided the day into twenty-four hours and the hour into sixty minutes and no modern man has ever been able to improve upon this old Babylonian invention. They possessed no watches but they measured time by the shadow of the sun-dial. They learned to use both the decimal and the duodecimal systems (nowadays we use only the decimal system, which is a great pity). The duodecimal system (ask your father what the word means), accounts for the sixty minutes and the sixty seconds and the twenty-four hours which seem to have so little in common with our modern world which would have divided day and night into twenty hours and the hour into fifty minutes and the minute into fifty seconds according to the rules of the restricted decimal system. The Chaldeans also were the first people to recognize the necessity of a regular day of rest. When they divided the year into weeks they ordered that six days of labor should be followed by one day, devoted to the "peace of the soul." [Illustration: THE CHALDEANS.] It was a great pity that the center of so much intelligence and industry could not exist for ever. But not even the genius of a number of very wise Kings could save the ancient people of Mesopotamia from their ultimate fate. The Semitic world was growing old. It was time for a new race of men. In the fifth century before Christ, an Indo-European people called the Persians (I shall tell you about them later) left its pastures amidst the high mountains of Iran and conquered the fertile valley. The city of Babylon was captured without a struggle. Nabonidus, the last Babylonian king, who had been more interested in religious problems than in defending his own country, fled. A few days later his small son, who had remained behind, died. Cyrus, the Persian King, buried the child with great honor and then proclaimed himself the legitimate successor of the old rulers of Babylonia. Mesopotamia ceased to be an independent State. It became a Persian province ruled by a Persian "Satrap" or Governor. As for Babylon, when the Kings no longer used the city as their residence it soon lost all importance and became a mere country village. In the fourth century before Christ it enjoyed another spell of glory. It was in the year 331 B.C. that Alexander the Great, the young Greek who had just conquered Persia and India and Egypt and every other place, visited the ancient city of sacred memories. He wanted to use the old city as a background for his own newly-acquired glory. He began to rebuild the palace and ordered that the rubbish be removed from the temples. Unfortunately he died quite suddenly in the Banqueting Hall of Nebuchadnezzar and after that nothing on earth could save Babylon from her ruin.