When they had thus shared by treaty a city they had not yet conquered, they commenced their operations for the siege. The Christian army left Jerusalem, and the Venetian fleet the port of Ptolemaïs, towards the beginning of spring. The historian of the kingdom of Jerusalem, William of Tyre, was for a long time archbishop of this celebrated commercial city, and he pauses here to describe the ancient wonders of his metropolis. In his recital, at once religious and profane, he invokes by turns the evidence of Isaiah and Virgil; after speaking of King Hyram and the tomb of Origen, he does nor disdain to celebrate the memory of Cadmus and the country of Dido. The good archbishop particularly vaunts the industry and the commerce of Tyre, the fertility of its territory, its dyes, so celebrated in all antiquity; its sand, which changed itself into transparent vases, and its sugar-canes, which began to be sought for by all regions of the universe. The city of Tyre, in the time of Baldwin, was no longer that sumptuous city, whose rich merchants, according to Isaiah, were princes; but it was still considered as the best-peopled and most commercial of the cities of Syria. It stood upon a delightful shore, screened by mountains from the blasts of the north; it had two large moles, which, like long arms, advanced into the sea, to inclose a port to which storm or tempest could find no access. The city of Tyre, which had stood out during more than seven months against the victorious Alexander, was defended on one side by a stormy sea and steep rocks, and on the other by a triple wall, surmounted by high towers. The doge of Venice at once penetrated into the port, and closed up all issue or access on the side of the sea. The patriarch of Jerusalem, and Pontius, count of Tripoli, regent of the kingdom, commanded the land army; the king, Baldwin du Bourg, being at that time a captive to the Saracens. In the early days of the siege, the Christians and the Mussulmans fought with obstinate ardour, but with equal success; the disunion of the infidels, however, soon powerfully assisted the efforts of the Franks. The caliph of Egypt had yielded half of the place to the sultan of Damascus, in order to engage him to defend it against the Christians. The Turks and the Egyptians were divided amongst themselves, and refused to fight together; the Pranks took advantage of these divisions, and daily gained a superiority. After a siege of a few months, the walls crumbled away before the machines of the Christians; provisions began to be short in the place; the Mussulmans were about to capitulate, when discord in turn disunited the Christians, and was on the point of rendering useless the prodigies of valour and all the labours of a long siege.