As the founder of the Milanese Academy, the first, in all probability, established in Italy, Lionardo composed his Treatise on Painting; which Annibale Carracci declared would have saved him twenty years of study had he known it in his youth. This work was first published in Paris, in 1651, by Raffaelle Dufresne, and was illustrated with engravings from drawings by N. Poussin, with some additions by Errard. The drawings of Poussin were in a MS. copy, which belonged to the Cavaliere del Pozzo. To this last object were directed the studies of Lionardo in optics, perspective, anatomy, libration, and proportion. In this active period of his life also were composed the numerous MS. books, explained by designs, which appear to have comprised specimens of the whole range of his vast knowledge. Thirteen of these books became the property of the Melzi family of Milan, on the death of Lionardo. The history and vicissitudes of these interesting works cannot now be accurately traced. The documents and observations of Dufresne, Mariette, and others, have been collected by Rogers, in his “Imitations of Drawings by the Old Masters.” Six or seven books, which cannot be accounted for after having been collected by one Pompeo Leoni, are supposed to have become the property of Philip II. of Spain. Some of the remaining volumes, augmented by less voluminous MSS. of Lionardo, were presented to the Ambrosian Library by Galeazzo Arconato. The inscription which records this donation, in 1637, states, that Arconato had been offered 3000 pistoles of gold by a king of England, (probably Charles I., and not James I., as Addison, Wright, and latterly Amoretti, suppose,) but which he, Arconato, “regio animo,” had refused. Another volume was presented to the Ambrosian Library by its founder, the Cardinal Borromeo; and Amoretti states, that another, containing drawings relating to hydrostatics, was sold “al Signor Smith, Inglese.” The whole of the MSS. of Lionardo, preserved in the Ambrosian Library, were taken from Milan to Paris, in 1796. A large folio volume of Lionardo’s Drawings, collected by the above-mentioned Pompeo Leoni, is in this country, in His Majesty’s collection. On its cover is inscribed, “Disegni di Lionardo da Vinci, restaurati da Pompeo Leoni:” it contains 779 drawings, various in subject and execution; the most remarkable are, perhaps, some accurate anatomical drawings. The whole are illustrated, like the contents of his other books, by notes written with his left hand, which can only be read through a glass. This volume was discovered, at the bottom of a large chest, about sixty years ago, by Mr. Dalton, the librarian of George III.; and in the same chest were Holbein’s drawings of the principal personages of the court of Henry VIII. It is supposed that they were placed there for security by Charles I., who retained a sincere love for the arts even in his misfortunes.