advantage of valuable advice from the Commendatore Giov. Morelli,
Senatore del Regno, and from Signor Gustavo Frizzoni, of Milan. The
translation, under many difficulties, of the Italian text into
English, is mainly due to Mrs. R. C. Bell; while the rendering of
several of the most puzzling and important passages, particularly in
the second half of Vol. I, I owe to the indefatigable interest taken
in this work by Mr. E. J. Poynter R. A. Finally I must express my
thanks to Mr. Alfred Marks, of Long Ditton, who has most kindly
assisted me throughout in the revision of the proof sheets.

The notes and dissertations on the texts on Architecture in Vol. II
I owe to my friend Baron Henri de Geymuller, of Paris.

I may further mention with regard to the illustrations, that the
negatives for the production of the "photo-gravures" by Monsieur
Dujardin of Paris were all taken direct from the originals.

It is scarcely necessary to add that most of the drawings here
reproduced in facsimile have never been published before. As I am
now, on the termination of a work of several years' duration, in a
position to review the general tenour of Leonardos writings, I may
perhaps be permitted to add a word as to my own estimate of the
value of their contents. I have already shown that it is due to
nothing but a fortuitous succession of unfortunate circumstances,
that we should not, long since, have known Leonardo, not merely as a
Painter, but as an Author, a Philosopher, and a Naturalist. There
can be no doubt that in more than one department his principles and
discoveries were infinitely more in accord with the teachings of
modern science, than with the views of his contemporaries. For this
reason his extraordinary gifts and merits are far more likely to be