Even under the Assyrian monarchs and especially under Sardanapalus, Babylon had been a scene of great intellectual activity. Sardanapalus, though an Assyrian, had been quite Babylon-ized. He made a library, a library not of paper but of the clay tablets that were used for writing in Mesopotamia since early Sumerian days. His collection has been unearthed and is perhaps the most precious store of historical material in the world. The last of the Chaldean line of Babylonian monarchs, Nabonidus, had even keener literary tastes. He patronized antiquarian researches, and when a date was worked out by his investigators for the accession of Sargon I he commemorated the fact by inscriptions. But there were many signs of disunion in his empire, and he sought to centralize it by bringing a number of the various local gods to Babylon and setting up temples to them there. This device was to be practised quite successfully by the Romans in later times, but in Babylon it roused the jealousy of the powerful priesthood of Bel Marduk, the dominant god of the Babylonians. They cast about for a possible alternative to Nabonidus and found it in Cyrus the Persian, the ruler of the adjacent Median Empire. Cyrus had already distinguished himself by conquering Croesus, the rich king of Lydia in Eastern Asia Minor. He came up against Babylon, there was a battle outside the walls, and the gates of the city were opened to him (538 B.C.). His soldiers entered the city without fighting. The crown prince Belshazzar, the son of Nabonidus, was feasting, the Bible relates, when a hand appeared and wrote in letters of fire upon the wall these mystical words: _“Mene, Mene, Tekel, Upharsin,”_ which was interpreted by the prophet Daniel, whom he summoned to read the riddle, as “God has numbered thy kingdom and finished it; thou art weighed in the balance and found wanting and thy kingdom is given to the Medes and Persians.” Possibly the priests of Bel Marduk knew something about that writing on the wall. Belshazzar was killed that night, says the Bible. Nabonidus was taken prisoner, and the occupation of the city was so peaceful that the services of Bel Marduk continued without intermission. PERSIAN MONARCH PERSIAN MONARCH From the ruins of Persepolis _Photo: Miss F. Biggs_ Thus it was the Babylonian and Median empires were united. Cambyses, the son of Cyrus, subjugated Egypt. Cambyses went mad and was accidentally killed, and was presently succeeded by Darius the Mede, Darius I, the son of Hystaspes, one of the chief councillors of Cyrus. THE RUINS OF PERSEPOLIS THE RUINS OF PERSEPOLIS The capital city of the Persian Empire; burnt by Alexander the Great _Photo: Major W. F. P. Rodd_ THE GREAT PORCH OF XERXES, AT PERSEPOLIS THE GREAT PORCH OF XERXES, AT PERSEPOLIS _Photo: Major W. F. P. Rodd_