your father, and of the illustrious house of Sforza.

[Footnote: The letter from which this passage is here extracted will
be found complete in section XXI. (see the explanation of it, on
page 2).]

720.

On the 23rd of April 1490 I began this book, and recommenced the
horse.

721.

There is to be seen, in the mountains of Parma and Piacenza, a
multitude of shells and corals full of holes, still sticking to the
rocks, and when I was at work on the great horse for Milan, a large
sackful of them, which were found thereabout, was brought to me into
my workshop, by certain peasants.

722.

Believe me, Leonardo the Florentine, who has to do the equestrian
bronze statue of the Duke Francesco that he does not need to care
about it, because he has work for all his life time, and, being so
great a work, I doubt whether he can ever finish it. [Footnote: This
passage is quoted from a letter to a committee at Piacenza for whom
Leonardo seems to have undertaken to execute some work. The letter
is given entire in section XXL; in it Leonardo remonstrates as to
some unreasonable demands.]