In the northern point of the Adriatic Sea lay the city of Venice, built upon a cluster of little islands.  The people had taken refuge there when Italy was overrun by the barbarians.  In course of time these Venetians had grown to be a mighty and powerful people, whose merchant ships traded all over the Mediterranean, and whose counsellors were famed for wisdom. They had shaken off the power of the Greek emperor, and were governed by a senate and council, with a chosen nobleman at its head, who was called the Doge, or Duke.  Just when the French, Germans, and Italians were setting off on the Fourth Crusade, in the year 1201, meaning to sail in Venetian ships, the young Alexius Angelus, son to the emperor Isaac Angelus, came to beg for help for his poor old father, who had been thrown into prison by his own brother, with his eyes put out.  It was quite aside from the main work of the Crusade, but the Venetians had always had a quarrel with the Greek emperors, and they prevailed to turn the army aside to attack Constantinople.  With an immense pair of shears they cut in twain the great chains which shut in the harbour of the Golden Horn, and sailed safely in, led by their Doge, Dandolo, who, though eighty years old, and blind, was as keen on the battle as the youngest man there.