arrange and elucidate the texts under the heads which have been
adopted in this work. MS. B. at Paris and the Codex Atlanticus at
Milan are the chief sources of our knowledge of Leonardo as an
architect, and I have recently subjected these to a thorough
re-investigation expressly with a view to this work._

_A complete reproduction of all Leonardo's architectural sketches
has not, indeed, been possible, but as far as the necessarily
restricted limits of the work have allowed, the utmost completeness
has been aimed at, and no efforts have been spared to include every
thing that can contribute to a knowledge of Leonardo's style. It
would have been very interesting, if it had been possible, to give
some general account at least of Leonardo's work and studies in
engineering, fortification, canal-making and the like, and it is
only on mature reflection that we have reluctantly abandoned this
idea. Leonardo's occupations in these departments have by no means
so close a relation to literary work, in the strict sense of the
word as we are fairly justified in attributing to his numerous notes
on Architecture._

_Leonardo's architectural studies fall naturally under two heads:_

_I. Those drawings and sketches, often accompanied by short remarks
and explanations, which may be regarded as designs for buildings or
monuments intended to be built. With these there are occasionally
explanatory texts._

_II. Theoretical investigations and treatises. A special interest
attaches to these because they discuss a variety of questions which
are of practical importance to this day. Leonardo's theory as to the