Thomas of Sarzana, who succeeded to the papacy as Nicolas V., had already won a considerable reputation as a [Sidenote: Nicolas V., 1447-1455.] student of ancient literature. Though he was rather a diligent collector of manuscripts and works of art than an original scholar, his patronage made Rome for a time the centre of humanist culture. His greatest work was the foundation of the Vatican library. As a politician Nicolas showed less ability and interest than as a student, but he was a sincere lover of peace, and he was able to maintain the position which Eugenius had won in his later years. He concluded the concordat with Germany, which put an end to the revolt originating with the Council of Basel, and the Council itself came to an ignominious end in 1449. In 1450 Nicolas celebrated the restoration of unity, and conciliated the Roman people, by a grand jubilee which brought the wealth of Europe to the eternal city. In spite of this general rejoicing, the next year witnessed a famous conspiracy against the secular authority of the Pope. Stefano Porcaro was a Roman noble who had won the favour of Nicolas by his devotion to ancient literature. But these studies led Porcaro, as they had previously led Rienzi, to an enthusiastic admiration of republican liberty. When he endeavoured to inspire the people with his opinions he was banished by the Pope to Bologna. Thence he returned secretly to Rome and organised a plot to imprison the Pope and cardinals, and to restore the republic, with Porcaro as tribune. More than four hundred persons were engaged in the scheme, and the number proved fatal to secrecy. Porcaro and nine of his followers were imprisoned in the castle of St. Angelo and executed without trial. After an interval of a few days harsh measures were resumed, and a number of suspected persons shared the same fate. This severity extinguished the last active desire to restore Roman liberty. Papal rule was strengthened by the failure of the plot; but Porcaro’s name, like that of Rienzi, lived long in the affections of the people. No sooner was this crisis passed than the news came that Constantinople had been taken by Mohammed II. in 1453. The empire had long ceased to possess any general authority in Europe, but the papacy still claimed to represent that unity of Christendom, whose disappearance had rendered such a catastrophe possible. It was upon the papacy, therefore, that the chief discredit fell of so notable a triumph for the infidel. But Nicolas V. had no ability to cope with such a vast problem as was involved in the union of the jarring interests of European states for the purpose of joint resistance to the Turks. Unable to devise any practical scheme, he gave himself up to despair, lamented that fate had raised him from a private station, and died in 1455.