362, but was frustrated by "balls of fire" issuing from under the ruins and frightening the workmen. In A.D. 529 the Greek emperor Justinian built a church in the city in honor of the Virgin. The Persians under Chosroes II. invaded Palestine in A.D. 614 and destroyed part of Jerusalem. After fourteen years they were defeated and Jerusalem was restored, but the Mohammedans under Omar captured it in A.D. 637. The structure called the Dome of the Rock, on Mt. Moriah, was built by them in A.D. 688. The Crusades next engage our attention. The first of these military expeditions was made to secure the right to visit the Holy Sepulcher. It was commenced at the call of the Pope in 1096. A force of two hundred and seventy-five thousand men began the march, but never entered Palestine. Another effort was made by six hundred thousand men, who captured Antioch in 1098. A little later the survivors defeated the Mohammedan army of two hundred thousand. Still later they entered Jerusalem, and Godfrey of Bouillon was made king of the city in 1099. By conquest he came to rule the whole of Palestine. The orders of Knights Hospitallers and Knights Templars were formed, and Godfrey continued in power about fifty years. In 1144 two European armies, aggregating one million two hundred thousand men, started on the second crusade, which was a total failure. Saladin, the Sultan of Egypt, conquered Jerusalem in 1187, and the third crusade was inaugurated, which resulted in securing the right to make pilgrimages to Jerusalem free from taxes. The power of the Crusaders was now broken. Another band assembled at Venice in 1203 to undertake the fourth crusade, but they never entered Palestine. The fifth effort was made, and Frederick, Emperor of Germany, crowned himself king of Jerusalem in 1229, and returned to his native land the next year. The Turks conquered Palestine in 1244 and burned Jerusalem. Louis IX. of France led the seventh crusade, another failure, in 1248. He undertook it again in 1270, but went to Africa, and Prince Edward of England entered Palestine in 1271 and accepted a truce for ten years, which was offered by the Sultan of Egypt. This, the eighth and last crusade, ended in 1272 by the return of Edward to England. In 1280 Palestine was invaded by the Mamelukes, and in 1291 the war of the Crusaders ended with the fall of Acre, "the last Christian possession in Palestine." Besides these efforts there were children's crusades for the conversion or conquest of the Moslems. The first, in 1212, was composed of thirty thousand boys. Two ship loads were drowned and the third was sold as slaves to the Mohammedans.