More or less successful biographies of Leonardo da Vinci have of late years appeared from the pens of Charles Blanc, Charles Clément, Mrs. Heaton, and Karl Brun. In this work, which Mr. Percy E. Pinkerton has kindly translated for me, I have sought to keep within the limits proper to a mere biography, endeavouring mainly to verify the facts of the artist's life, and to confirm the authenticity of those works which he has left behind. Happily in this instance it has been not wholly impossible to add somewhat to our former personal knowledge of the great painter, as the best and most reliable sources of information are Leonardo's own unpublished documents, which have hitherto met with but scant attention from the student of art. The researches undertaken by me in the four Leonardo mss. In London, and the numerous memoranda in the Royal Library at Windsor — access to which has been most graciously accorded to me — have led to results which throw new light upon several facts relating to Leonardo's biography, and to the history of his works.