books: while the Vatican library was still being designed and planned, he kept the rarest books near to him in his bedroom, with the others in a room nearby. Often thinking fondly of his former work as a librarian, he once remarked, "I had more happiness in a day than now in a whole year." He was compelled, however, to add that the lustre of his pontificate would be forever dulled by the fall of Constantinople, which the Turks took in 1453. Unsuccessful in a campaign to unite Christian powers to come to the aid of Constantinople, just before that great citadel was conquered, Nicholas had ordered 10 papal ships to sail with ships from Genoa, Venice and Naples to defend the capital of the Eastern Roman Empire. However, the ancient capital fell before the ships could offer any aid. The Pope bitterly felt this catastrophe as a double blow to Christendom and to Greek letters. "It is a second death", wrote Aeneas Silvius, "to Homer and Plato." Nicholas preached a crusade and endeavoured to reconcile the mutual animosities of the Italian states, but without much success. In undertaking these works, Nicholas was moved "to strengthen the weak faith of the populace by the greatness of that which it sees". The Roman populace, however, appreciated neither his motives nor their results, and in 1452 a formidable conspiracy for the overthrow of the papal government under the leadership of Stefano Porcari was discovered and crushed. This revelation of disaffection, together with the fall of Constantinople in 1453, darkened the last years of Pope Nicholas. "As Thomas of Sarzana", he said, "I had more happiness in a day than now in a whole year". Slavery In late spring of 1452 Byzantine Emperor Constantine XI wrote to Pope Nicholas for help against the impending siege by Ottoman Sultan Mehmed II. Nicholas issued the bull Dum Diversas (18 June 1452) authorizing King Alfonso V of Portugal to "attack, conquer, and subjugate Saracens, pagans and other enemies of Christ wherever they may be found". Issued less than a year before the fall of Constantinople, the bull may have been intended to begin another crusade against the Ottoman Empire. Ownership of the Canary Islands continued to be a source of dispute between Spain and Portugal and Nicholas was asked to settle the matter, ultimately in favor of the Portuguese. The geographical area of the concession given