There are several manuscripts extant of the sixteenth and seventeenth centuries purporting to be treatises of painting by Leonardo da Vinci. The oldest of these, and the only one that contains the Paragone, is preserved in the Vatican Library (Urbinas 1270). It is a compilation made from Leonardo's original manuscripts entitled 'Libro di Pittura di M. Leonardo da Vinci, Pittore et Scultore Fiorentino'. This codex was in the library of the Dukes of Urbino among the books collected by Francesco Maria della Rovere, the last Duke (d. 1631). The library passed into the possession of the popes in 1657 and was transferred then to the Vatican. There is no record of the previous history of the manuscript, when and under what circum- stances it was compiled, and how it came to the ducal library; but from internal evidence we may infer that it was an attempt soon after Leonardo's death to make a selection from his various manuscripts preparatory to a publication. The book, 15 by 21 cm. in size, is bound in vellum and contains 331 numbered sheets. The illustrations accompanying the text were first lightly sketched in pencil and then drawn over in ink. The calligraphy is dear and regular and may be dated approximately in the sixteenth century. To judge by his language, the scribe was a Lombard. His spelling and punctuation were defective; and his work was super- vised, for there are corrections in two other handwritings. That the copyist had Leonardo's original manuscripts before him is shown by his mention of the left-handed writing as an excuse for errors com- mitted, and by the list at the end of his work of eighteen of these manuscripts from which he had copied sections. Of the total of 944 transcribed paragraphs in the compilation a few are still extant in the Master's own writing; the majority, however, are not to be found in the manuscripts that have survived. The compilation must therefore have been made when the collection of manuscripts which Leonardo left at his death was still more or less intact, as was the case when in the safe keeping of Francesco Melzi, who had inherited all Leonardo's literary remains and treasured them as his most precious possessions . . .