long been a well-known document,--in which he offers his service as
an architect to that prince, tends to confirm the belief that he was
something more than an amateur of the art. This hypothesis has
lately been confirmed by the publication of certain documents,
preserved at Milan, showing that Leonardo was not only employed in
preparing plans but that he took an active part, with much credit,
as member of a commission on public buildings; his name remains
linked with the history of the building of the Cathedral at Pavia
and that of the Cathedral at Milan._

_Leonardo's writings on Architecture are dispersed among a large
number of MSS., and it would be scarcely possible to master their
contents without the opportunity of arranging, sorting and comparing
the whole mass of materials, so as to have some comprehensive idea
of the whole. The sketches, when isolated and considered by
themselves, might appear to be of but little value; it is not till
we understand their general purport, from comparing them with each
other, that we can form any just estimate of their true worth._

_Leonardo seems to have had a project for writing a complete and
separate treatise on Architecture, such as his predecessors and
contemporaries had composed--Leon Battista Alberti, Filarete,
Francesco di Giorgio and perhaps also Bramante. But, on the other
hand, it cannot be denied that possibly no such scheme was connected
with the isolated notes and researches, treating on special
questions, which are given in this work; that he was merely working
at problems in which, for some reason or other he took a special
interest._

_A great number of important buildings were constructed in Lombardy