OF LUTING THE FURNACE WITHIN.

The furnace must be luted before you put the metal in it, with earth
from Valenza, and over that with ashes.

[Footnote 1. 2.: _Terra di Valenza_.--Valenza is north of
Alessandria on the Po.]

OF RESTORING THE METAL WHEN IT IS BECOMING COOL.

When you see that the bronze is congealing take some willow-wood cut
in small chips and make up the fire with it.

THE CAUSE OF ITS CURDLING.

I say that the cause of this congealing often proceeds from too much
fire, or from ill-dried wood.

TO KNOW THE CONDITION OF THE FIRE.

You may know when the fire is good and fit for your purpose by a
clear flame, and if you see the tips of the flames dull and ending
in much smoke do not trust it, and particularly when the flux metal
is almost fluid.

OF ALLOYING THE METAL.

Metal for guns must invariably be made with 6 or even 8 per cent,
that is 6 of tin to one hundred of copper, for the less you put in,
the stronger will the gun be.

WHEN THE TIN SHOULD BE ADDED TO THE COPPER.

The tin should be put in with the copper when the copper is reduced
to a fluid.

HOW TO HASTEN THE MELTING.

You can hasten the melting when 2/3ds of the copper is fluid; you
can then, with a stick of chestnut-wood, repeatedly stir what of
copper remains entire amidst what is melted.

_Introductory Observations on the Architectural Designs (XII), and
Writings on Architecture (XIII)._

_Until now very little has been known regarding Leonardo's labours
in the domain of Architecture. No building is known to have been
planned and executed by him, though by some contemporary writers
incidental allusion is made to his occupying himself with
architecture, and his famous letter to Lodovico il Moro,--which has
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
during the period between 1472 and 1499, and among them there are
several by unknown architects, of so high an artistic merit, that it
is certainly not improbable that either Bramante or Leonardo da
Vinci may have been, directly or indirectly, concerned in their
erection._

_Having been engaged, for now nearly twenty years, in a thorough
study of Bramante's life and labours, I have taken a particular
interest in detecting the distinguishing marks of his style as
compared with Leonardo's. In 1869 I made researches about the
architectural drawings of the latter in the Codex Atlanticus at
Milan, for the purpose of finding out, if possible the original
plans and sketches of the churches of Santa Maria delle Grazie at
Milan, and of the Cathedral at Pavia, which buildings have been
supposed to be the work both of Bramante and of Leonardo. Since 1876
I have repeatedly examined Leonardo's architectural studies in the
collection of his manuscripts in the Institut de France, and some of
these I have already given to the public in my work on_ "Les Projets
Primitifs pour la Basilique de St. Pierre de Rome", _P1. 43. In 1879
I had the opportunity of examining the manuscript in the Palazzo
Trivulzio at Milan, and in 1880 Dr Richter showed me in London the
manuscripts in the possession of Lord Ashburnham, and those in the
British Museum. I have thus had opportunities of seeing most of
Leonardo's architectural drawings in the original, but of the
manuscripts tliemselves I have deciphered only the notes which
accompany the sketches. It is to Dr Richter's exertions that we owe
the collected texts on Architecture which are now published, and
while he has undertaken to be responsible for the correct reading of
the original texts, he has also made it his task to extract the
whole of the materials from the various MSS. It has been my task to
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
origin and progress of cracks in buildings is perhaps to be
considered as unique in its way in the literature of Architecture._

_HENRY DE GEYMULLER_

_XII._

_Architectural Designs._

_I. Plans for towns._

_A. Sketches for laying out a new town with a double system of high-
level and low-level road-ways._

_Pl. LXXVII, No. 1 (MS. B, 15b). A general view of a town, with the
roads outside it sloping up to the high-level ways within._

_Pl. LXXVII, No. 3 (MS. B, 16b. see No. 741; and MS. B. 15b, see No.
742) gives a partial view of the town, with its streets and houses,
with explanatory references._

_Pl. LXXVII, No. 2 (MS. B, 15b; see No. 743). View of a double
staircaise with two opposite flights of steps._

_Pl. LXXVIII, Nos. 2 and 3 (MS. B, 37a). Sketches illustrating the
connection of the two levels of roads by means of steps. The lower
galleries are lighted by openings in the upper roadway._

_B. Notes on removing houses (MS. Br. M., 270b, see No. 744)._