It was in the time of Cosimo that the written history of art began its first feeble efforts. Its forerunner was Cennino Cennini of Colle in the Elsa valley, a pupil of Angelo Gaddi apparently at Padua, where he was in the service of Francesco da Carrara. Towards the end of the fourteenth century he wrote a book on painting, which is of great value for the study of artistic practice before the victory of oil-painting over tempera, as it is also for the history of modelling, casting, plaster-work, gilding, &c.[161] This book treats merely of technicalities; but in Lorenzo Ghiberti’s commentaries an unfinished treatise on architecture and the proportion of figures is combined with notices of ancient art and also of modern, from its re-awakening in the second half of the thirteenth century down to the writer’s own time and works.[162] The latter portion is the principal source whence Giorgio Vasari drew his knowledge of past times. Ghiberti’s contemporary Filarete has given many notices, valuable for the history of art, referring to Medicean times, in his treatise on architecture, which he dedicated—in styles differing according to the persons and circumstances, to two patrons, Piero de’ Medici and Francesco Sforza, in 1460.[163] These notices, as well as technical remarks, were also made use of by Vasari, whose judgment on Filarete’s confused book is just, though rather severely expressed. CHAPTER XIII. BUILDING IN THE DAYS OF LORENZO DE’ MEDICI. ARCHITECTURE was always a subject of great interest to Lorenzo de’ Medici; he possessed an unusual knowledge of the art.[164] It was he who made the plan for the façade of Sta. Maria del Fiore, which was executed in wood by Jacopo Sansovino and painted in chiaroscuro by Andrea del Sarto more than twenty years after the designer’s death, when his son, Pope Leo X., made his public entry into Florence.[165] We shall see what share he took in the project for the completion of this façade. He was intimate with several of the chief architects of the time. A letter, written to him from Rome by Alberti,[166] unluckily not on the subject of art but about a proposed exchange of property, shows on what good terms they were: ‘I am glad that thou dost address me in confidence worthy of our old friendship; and as I am conscious of my obligations, I am ready to do for thee and at thy desire anything that can be agreeable to one who loves thee. If what thou askest of me were not founded on reason, thou wouldest neither have consented to act as mediator thyself, nor have sought out a third party to do so.’ The brothers Da Majano and Sangallo enjoyed his interest and assistance both in and outside of Florence, where a great deal of building was carried on. Yet he built nothing more himself than a convent and a villa. Of the convent not a trace is left, and the façades of the cathedral and of the church of the Santo Spirito—in which he was so much interested—still await completion, as does that of San Lorenzo,