Retribution, at least according to human ideas of justice, often seems to lag in history; but in the case of the fall of Constantinople some of the culprits most responsible, on account of their selfish indifference, were speedily called on to pay the penalty. Mohammed II, his ambition inflated by what he had already achieved, planned the reduction of Christendom, declaring that he would feed his horse from the altar of St. Peter’s in Rome. With an enormous army he advanced through Serbia and besieged Belgrade; but here he was thrust back by a Christian champion, John Hunyadi, ‘the wicked one’, as the title reads in Turkish, with such loss of men and material ‘that Hungary and eastern Germany were saved from serious danger for eighty years’. With the Balkan states it was otherwise, whose governments, divided in their counsels, jealous in their rivalries, had been incapable of the union that could alone have saved them, and one by one they were crushed beneath ‘the Conqueror’s’ heel. Greece also came under Moslem domination, and finally the islands of the Aegean Sea that Venice had torn from Constantinople in the interests of her trade were wrested away from her, leaving her faced with the prospect of commercial ruin. PART II. VOYAGE AND DISCOVERY [Sidenote: Marco Polo] All through the Middle Ages it had been to the cities of the Mediterranean, first of all to Amalfi and Pisa, then to Marseilles, Barcelona, Genoa, and Venice, that Europe had turned as her obvious medium of communication with the East and all its fabulous wonders. In the thirteenth century a Venetian merchant, Marco Polo, setting forth with his father and uncle, had visited the kingdom of Cathay, or China, and brought back twenty years later not only marvellous tales of the court of Khubla Khan in Pekin, but also precious stones, rubies, sapphires, diamonds, and emeralds in such abundance that he was soon nicknamed by his fellow citizens ‘Marco of the Millions’. Into the delighted ears of the guests he invited to a banquet on his return he poured descriptions of a land where ‘merchants are so numerous and so rich that their wealth can neither be told nor believed. They and their ladies do nothing with their own hands, but live as delicately as if they were kings.’ What seems to have struck his mediaeval mind with most astonishment were the enormous public baths in the ‘City of Heaven’ in southern China, of which there were four thousand, ‘the largest and most beautiful baths in the world.’