The commander of this expedition was a Turk called Albitangoth[168], who broke through four of the genoese ships. The Turk appointed another commander to surround the city by sea and land. Constantinople is a very strong city, of a triangular form, twenty miles in circuit on the land side, and five miles wide from the land boundary to the harbour and gulf. The walls on the land side are very strong and high, having barbicans and loop holes on the top, well fortified without by the ditches and ramparts. The principal walls are from fifteen to twenty-two fathoms high: in some places six, and in others eight fathoms wide: the outworks are twenty fathoms high and three in thickness, and the ditches ten deep. The city contained from twenty-five to thirty thousand persons, and six thousand combatants. In the harbour were thirty ships and nine galleys, to defend the chain that had been thrown across it: of this number were two armed vessels, and three merchant ships, from the Venetians; three belonging to the emperor,--and one to sir John Justinian, a Genoese in the pay of the emperor. Constantinople, although besieged by sea and land, and strongly battered by bombards and cannon, held out for fifty days, during which a captain of one of the galleys, in conjunction with others ordered on this service, attempted to set fire to the turkish fleet; but the galley was sunk by a heavy stone from a bombard, and the others ran on the sharp stakes with which the Turks had fortified the van division of their fleet. On the land side, Sangombassa, king of the Albanians, had in his army many who had been accustomed to work in gold and silver mines,--and he ordered them to open fourteen mines under the walls of the city, to throw them down. As these mines were opened at a distance from the walls, the Christians countermined them, and at times stifled the Turks in their mine with smoke, or suffocated them with stinks: at other times they drowned them, by introducing water suddenly on them, or destroyed them by fighting hand to hand. Sangombassa constructed a high and strong tower of wood that overtopped the walls, and threw across an arm of the sea a bridge of boats one thousand fathoms in length and seven wide, for the army to cross, besides erecting other smaller towers that were both light and strong, and could be moved from one place to another when wanted. There were daily skirmishes, in which many were slain on each side,--but for one that was killed in the town one hundred were destroyed of the besiegers.