origin of all the known copies of the Trattato. The extensive
researches I was subsequently enabled to prosecute, and the results
of which are combined in this work, were only rendered possible by
the unrestricted permission granted me to investigate all the
Manuscripts by Leonardo dispersed throughout Europe, and to
reproduce the highly important original sketches they contain, by
the process of "photogravure". Her Majesty the Queen graciously
accorded me special permission to copy for publication the
Manuscripts at the Royal Library at Windsor. The Commission Centrale
Administrative de l'Institut de France, Paris, gave me, in the most
liberal manner, in answer to an application from Sir Frederic
Leighton, P. R. A., Corresponding member of the Institut, free
permission to work for several months in their private collection at
deciphering the Manuscripts preserved there. The same favour which
Lord Ashburnham had already granted me was extended to me by the
Earl of Leicester, the Marchese Trivulsi, and the Curators of the
Ambrosian Library at Milan, by the Conte Manzoni at Rome and by
other private owners of Manuscripts of Leonardo's; as also by the
Directors of the Louvre at Paris; the Accademia at Venice; the
Uffizi at Florence; the Royal Library at Turin; and the British
Museum, and the South Kensington Museum. I am also greatly indebted
to the Librarians of these various collections for much assistance
in my labours; and more particularly to Monsieur Louis Lalanne, of
the Institut de France, the Abbate Ceriani, of the Ambrosian
Library, Mr. Maude Thompson, Keeper of Manuscripts at the British
Museum, Mr. Holmes, the Queens Librarian at Windsor, the Revd Vere
Bayne, Librarian of Christ Church College at Oxford, and the Revd A.
Napier, Librarian to the Earl of Leicester at Holkham Hall.

In correcting the Italian text for the press, I have had the