regarded as an Index, not far short of complete, of all Leonardo s
literary works now extant. The consecutive numbers (from 1 to 1566)
at the head of each passage in this work, indicate their logical
sequence with reference to the subjects; while the letters and
figures to the left of each paragraph refer to the original
Manuscript and number of the page, on which that particular passage
is to be found. Thus the reader, by referring to the List of
Manuscripts at the beginning of Volume I, and to the Bibliography at
the end of Volume II, can, in every instance, easily ascertain, not
merely the period to which the passage belongs, but also exactly
where it stood in the original document. Thus, too, by following the
sequence of the numbers in the Bibliographical index, the reader may
reconstruct the original order of the Manuscripts and recompose the
various texts to be found on the original sheets--so much of it,
that is to say, as by its subject-matter came within the scope of
this work. It may, however, be here observed that Leonardo s
Manuscripts contain, besides the passages here printed, a great
number of notes and dissertations on Mechanics, Physics, and some
other subjects, many of which could only be satisfactorily dealt
with by specialists. I have given as complete a review of these
writings as seemed necessary in the Bibliographical notes.

In 1651, Raphael Trichet Dufresne, of Paris, published a selection
from Leonardo's writings on painting, and this treatise became so
popular that it has since been reprinted about two-and-twenty times,
and in six different languages. But none of these editions were
derived from the original texts, which were supposed to have been
lost, but from early copies, in which Leonardo's text had been more
or less mutilated, and which were all fragmentary. The oldest and on
the whole the best copy of Leonardo's essays and precepts on