Vasari says, and rightly, in his Life of Leonardo, "that he laboured
much more by his word than in fact or by deed", and the biographer
evidently had in his mind the numerous works in Manuscript which
have been preserved to this day. To us, now, it seems almost
inexplicable that these valuable and interesting original texts
should have remained so long unpublished, and indeed forgotten. It
is certain that during the XVIth and XVIIth centuries their
exceptional value was highly appreciated. This is proved not merely
by the prices which they commanded, but also by the exceptional
interest which has been attached to the change of ownership of
merely a few pages of Manuscript.

That, notwithstanding this eagerness to possess the Manuscripts,
their contents remained a mystery, can only be accounted for by the
many and great difficulties attending the task of deciphering them.
The handwriting is so peculiar that it requires considerable
practice to read even a few detached phrases, much more to solve
with any certainty the numerous difficulties of alternative
readings, and to master the sense as a connected whole. Vasari
observes with reference to Leonardos writing: "he wrote backwards,
in rude characters, and with the left hand, so that any one who is
not practised in reading them, cannot understand them". The aid of a
mirror in reading reversed handwriting appears to me available only
for a first experimental reading. Speaking from my own experience,
the persistent use of it is too fatiguing and inconvenient to be
practically advisable, considering the enormous mass of Manuscripts
to be deciphered. And as, after all, Leonardo's handwriting runs
backwards just as all Oriental character runs backwards--that is
to say from right to left--the difficulty of reading direct from the
writing is not insuperable. This obvious peculiarity in the writing