These jars, when bound together with their mouth inverted in the water,
formed admirable pontoons. Artillery was mounted on this bridge and the
galleys were brought up to the city walls, which were now assailed from
a quarter hitherto safe from attack. The Genoese under Justiniani on one
occasion, and the Venetians on another, were defeated in their attempts
to burn the Turkish fleet and destroy the bridge. The fire of the
artillery rendered the attacks of the Italians abortive, and their
failure afforded a decisive proof that the defence of the city was
becoming desperate. To avoid the admission of their inferiority in
force, the defeated parties threw the blame on one another, and their
dissensions became so violent that the Emperor could hardly appease the
quarrel.

During all the labors of the besiegers in other quarters, the approaches
were pushed vigorously forward against the land wall. Though the activity
in other and more novel operations might attract greater attention, the
industry of those engaged in filling up the ditch, and the fire of the
breaching batteries, never relaxed. Though all attempts to cross the
ditch at the gate of St. Romanus were long baffled by the Greeks, and
the mining operations at Blachern were discovered and defeated by Johann
Grant, still the superior number and indefatigable perseverance of the
Ottomans at last filled up the ditch, and the fire of their guns ruined
the walls. A visible change in the state of the fortifications encouraged
the assailants, and showed the besieged that the enemy was gradually
gaining a decided advantage. At the commencement of the siege, the
Ottoman engineers had displayed so little knowledge of the mode of using
artillery to effect a breach that a Hungarian envoy from John Hunyady,[1]
who visited Mahomet's camp, ridiculed the idea of their producing any
effect on the walls of Constantinople. This stranger was said to have
taught the Turks to fire in volleys, and to cut the wall in rectangular