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
appreciated in our own time than they could have been during the
preceding centuries. He has been unjustly accused of having
squandered his powers, by beginning a variety of studies and then,
having hardly begun, throwing them aside. The truth is that the
labours of three centuries have hardly sufficed for the elucidation
of some of the problems which occupied his mighty mind.

Alexander von Humboldt has borne witness that "he was the first to
start on the road towards the point where all the impressions of our
senses converge in the idea of the Unity of Nature" Nay, yet more