The authenticated works of Da Vinci are exceedingly scarce; he bestowed so much labor upon them that they were never very numerous, and time and casualty has reduced the number. It is said that one of the proprietors of the Orleans collection destroyed some of the most capital works of Da Vinci and Correggio from conscientious scruples! The most celebrated are the Mona Lisa Giocondo, in the Louvre; a lovely picture called La Vierge aux Rochers; a Leda, in the collection of Prince Kaunitz at Vienna; Christ disputing with the Doctors, in the Pamfili palace at Rome; John the Baptist, formerly in the French Museum; the portrait of Lodovico Maria Sforza, in the Dresden gallery. There are a few others in the collections at Florence, Milan, and Rome. There are some in England; but the authenticity of most of these, to say the least, is extremely doubtful. The Christ disputing with the Doctors, in the National gallery, is doubtless a copy by some one of his pupils. The original, as before mentioned, is at Rome. Passavant says, “The numerous copies or repetitions of this picture, now existing, imply the estimation in which the original cartoon was held, and are additional proofs of its being an original work. One of these I saw in the Spada gallery at Rome; two others at Milan--one in the Episcopal palace, and the other in the house of the Consigliere Commendatore Casati.” Most of the pictures claimed to be original by Da Vinci, even in the public galleries of Europe, were executed by his pupils and imitators, several of whom copied and imitated him with great success. Lanzi says that Lorenzo di Credi approached him so closely, that one of his copies of Lionardo could hardly be distinguished from the original. For a list of his imitators, see Spooner’s Dictionary of Painters, Engravers, Sculptors, and Architects, table of Imitators. WORKS IN NIELLO.