The floor is divided into four rooms by party-walls which are probably older than 1475, but which are proved, by the catalogue of 1481, to have been in existence at that period. The first of these rooms, entered directly from the court, contained the Latin Library; the second, the Greek Library. These two, taken together, formed the Common, or Public, Library (_Bibliotheca communis_, _B. publica_, or merely _Bibliotheca_). Next to this room, or these rooms, was the _Bibliotheca secreta_ or Reserved Library, in which the more precious MSS. were kept apart from the others. The fourth room, which was not fitted up till 1480 or 1481, was called _Bibliotheca pontificia_. In addition to MSS. it contained the papal archives and registers (_Regesta_). In the catalogue dated 1512 it is called _Intima et ultima secretior bibliotheca_, and seems to have contained the most valued treasures. This quadripartite division is commemorated by Aurelio Brandolini (Epigram XII.)[372]. After alluding to the founders of some of the famous libraries of antiquity, he says in conclusion: Bibliotheca fuit, fateor, sua cuique, sed vna. Sixte pater vincis: quatuor vnus habes. Thanks to the care with which Platina set down his expenditure, we are able to follow step by step the gradual transformation of the rooms. His account-books[373], begun 30 June 1475, record, with a minuteness as rare as it is valuable, his transactions with the different artists and workmen whom he thought proper to employ. It was evidently intended that the library should be beautiful as well as useful, and some of the most celebrated artists of the day were set to work upon it. The librarian prudently began in August, 1475, by increasing the light, and a new window was made "on the side next the court." It seems to have been impossible to get either workmen or materials in Rome; both were supplied from a distance. For the windows, glass, lead and solder were brought from Venice, and a German, called simply Hormannus, i.e. Hermann, was hired to glaze them. For the internal decoration two well-known Florentine artists--the brothers Ghirlandajo--were engaged, with Melozzo da Forli, who was painting there in 1477[374]. In 1476 the principal entrance was decorated with special care. Marble was bought for the doorcase, and the door itself was studded with 95 bronze nails, which were gilt, as were also the ring and knocker, and the frame of trellised ironwork (_cancellus_), which hung within the outer door.