§ 110.10. =Nicholas V., Calixtus III., and Pius II., A.D. 1447-1464.=--With =Nicholas V.=, A.D. 1447-1455, a miracle of classical scholarship and founder of the Vatican Library, the Roman see for the first time became the patron of humanistic studies, and under this mild and liberal pope the secular government of Rome was greatly improved. The conquest of Constantinople by the Turks, in A.D. 1453, produced excitement throughout the whole of Europe. The eloquence of the pope roused the crusading spirit of Christendom, and oratorical appeals were thundered from the pulpits of all churches and cathedrals. But the princes remained cold and indifferent. After Nicholas, a Spaniard, the cardinal Alphonso Borgia, then in his seventy-seventh year, was raised to the papal chair as =Calixtus III.=, A.D. 1455-1458. Hatred of Turks and love of nephews were the two characteristics of the man. Yet he could not rouse the princes against the Turks, and the fleet fitted out at his own cost only plundered a few islands in the Archipelago. Calixtus’ successor was Æneas Sylvius Piccolomini, the able and accomplished apostate from the Basel reform party, who styled himself, with intended allusion to Virgil’s “_pius Æneas_,” =Pius II.=, A.D. 1458-1464. The pope’s Ciceronian eloquence failed to secure the attendance of princes at the Mantuan Congress, summoned in A.D. 1459 to take steps for the equipment of a crusade. A war against the Turks was indeed to have been undertaken by emperor Frederick III., and a tax was to have been levied on Christians and Jews for its cost; but neither tax nor crusade was forthcoming. Pius demanded of the French ambassadors a formal repudiation of the Pragmatic Sanction of Bourges, and when they threatened the calling of an œcumenical council, he issued the bull _Execrabilis_, which pronounced “the execrable and previously unheard of” enormity of an appeal to a council to be heresy and treason. In A.D. 1461 the pope, by a long epistle, attempted the conversion of Mohammed II., the powerful conqueror of Constantinople. As the discovery of the great alum deposit at Rome in A.D. 1462 was attributed to miraculous direction, the pope was led to devote its rich resources to the fitting out of a crusade against the Turks. He wished himself to lead the army in person, in order to secure victory by uplifted hands, like Moses in the war with Amalek. But here again the princes left him in the lurch. Coming to Ancona in A.D. 1464 to take ship there upon his great undertaking, only his own two galleys were waiting him. After long weary waiting, twelve Venetian ships arrived, just in time to see the pope prostrated with fever and excitement.