The Notebooks of Leonardo Da Vinci — Complete
drawings of the Uffizi Collection, where in one instance, it
indicates the _abacus_ of a Doric capital.]
765.
STEPS OF URRBINO.
The plinth must be as broad as the thickness of the wall against
which the plinth is built. [Footnote: See Pl. CX No. 3. The hasty
sketch on the right hand side illustrates the unsatisfactory effect
produced when the plinth is narrower than the wall.]
766.
The ancient architects ...... beginning with the Egyptians (?) who,
as Diodorus Siculus writes, were the first to build and construct
large cities and castles, public and private buildings of fine form,
large and well proportioned .....
The column, which has its thickness at the third part .... The one
which would be thinnest in the middle, would break ...; the one
which is of equal thickness and of equal strength, is better for the
edifice. The second best as to the usefulness will be the one whose
greatest thickness is where it joins with the base.
[Footnote: See Pl. CIII, No. 3, where the sketches belonging to
lines 10--16 are reproduced, but reversed. The sketch of columns,
here reproduced by a wood cut, stands in the original close to lines
5--8.]
The capital must be formed in this way. Divide its thickness at the
top into 8; at the foot make it 5/7, and let it be 5/7 high and you
will have a square; afterwards divide the height into 8 parts as you
did for the column, and then take 1/8 for the echinus and another
eighth for the thickness of the abacus on the top of the capital.
The horns of the abacus of the capital have to project beyond the
greatest width of the bell 2/7, i. e. sevenths of the top of the
bell, so 1/7 falls to the projection of each horn. The truncated
part of the horns must be as broad as it is high. I leave the rest,
that is the ornaments, to the taste of the sculptors. But to return
to the columns and in order to prove the reason of their strength or
weakness according to their shape, I say that when the lines
starting from the summit of the column and ending at its base and
their direction and length ..., their distance apart or width may be
equal; I say that this column ...
767.
The cylinder of a body columnar in shape and its two opposite ends
are two circles enclosed between parallel lines, and through the
centre of the cylinder is a straight line, ending at the centre of
these circles, and called by the ancients the axis.
[Footnote: Leonardo wrote these lines on the margin of a page of the
Trattato di Francesco di Giorgio, where there are several drawings
of columns, as well as a head drawn in profile inside an outline
sketch of a capital.]
768.
_a b_ is 1/3 of _n m_; _m o_ is 1/6 of _r o_. The ovolo projects 1/6
of _r o_; _s_ 7 1/5 of _r o_, _a b_ is divided into 9 1/2; the
abacus is 3/9 the ovolo 4/9, the bead-moulding and the fillet 2/9
and 1/2.
[Footnote: See Pl. LXXXV, No. 16. In the original the drawing and
writing are both in red chalk.]
_Pl. LXXXV No. 6 (MS. Ash. II 6b) contains a small sketch of a
capital with the following note, written in three lines:_ I chorni
del capitelo deono essere la quarta parte d'uno quadro _(The horns
of a capital must measure the fourth part of a square)._
_MS. S. K. M. III 72b contains two sketches of ornamentations of
windows._
_In MS. C. A. 308a; 938a (see Pl. LXXXII No. 1) there are several
sketches of columns. One of the two columns on the right is similar
to those employed by Bramante at the Canonica di S. Ambrogio. The
same columns appear in the sketch underneath the plan of a castle.
There they appear coupled, and in two stories one above the other.
The archivolls which seem to spring out of the columns, are shaped
like twisted cords, meant perhaps to be twisted branches. The walls
between the columns seem to be formed out of blocks of wood, the
pedestals are ornamented with a reticulated pattern. From all this
we may suppose that Leonardo here had in mind either some festive
decoration, or perhaps a pavilion for some hunting place or park.
The sketch of columns marked "35" gives an example of columns shaped
like candelabra, a form often employed at that time, particularly in
Milan, and the surrounding districts for instance in the Cortile di
Casa Castiglione now Silvestre, in the cathedral of Como, at Porta
della Rana &c._
769.
CONCERNING ARCHITRAVES OF ONE OR SEVERAL PIECES.
An architrave of several pieces is stronger than that of one single
piece, if those pieces are placed with their length in the direction
of the centre of the world. This is proved because stones have their
grain or fibre generated in the contrary direction i. e. in the
direction of the opposite horizons of the hemisphere, and this is
contrary to fibres of the plants which have ...
[Footnote: The text is incomplete in the original.]
_The Proportions of the stories of a building are indicated by a
sketch in MS. S. K. M. II2 11b (see Pl. LXXXV No. 15). The measures
are written on the left side, as follows: br 1 1/2--6 3/4--br
1/12--2 br--9 e 1/2--1 1/2--br 5--o 9--o 3 [br=braccia; o=oncie].
Pl. LXXXV No. 13 (MS. B. 62a) and Pl. XCIII No. 1. (MS. B. 15a) give
a few examples of arches supported on piers._
_XIII.
Theoretical writings on Architecture.
Leonardo's original writings on the theory of Architecture have come
down to us only in a fragmentary state; still, there seems to be no
doubt that he himself did not complete them. It would seem that
Leonardo entertained the idea of writing a large and connected book
on Architecture; and it is quite evident that the materials we
possess, which can be proved to have been written at different
periods, were noted down with a more or less definite aim and
purpose. They might all be collected under the one title: "Studies
on the Strength of Materials". Among them the investigations on the
subject of fissures in walls are particularly thorough, and very
fully reported; these passages are also especially interesting,
because Leonardo was certainly the first writer on architecture who
ever treated the subject at all. Here, as in all other cases
Leonardo carefully avoids all abstract argument. His data are not
derived from the principles of algebra, but from the laws of
mechanics, and his method throughout is strictly experimental.
Though the conclusions drawn from his investigations may not have
that precision which we are accustomed to find in Leonardo's
scientific labours, their interest is not lessened. They prove at
any rate his deep sagacity and wonderfully clear mind. No one
perhaps, who has studied these questions since Leonardo, has
combined with a scientific mind anything like the artistic delicacy
of perception which gives interest and lucidity to his observations.
I do not assert that the arrangement here adopted for the passages
in question is that originally intended by Leonardo; but their
distribution into five groups was suggested by the titles, or
headings, which Leonardo himself prefixed to most of these notes.
Some of the longer sections perhaps should not, to be in strict
agreement with this division, have been reproduced in their entirety
in the place where they occur. But the comparatively small amount of
the materials we possess will render them, even so, sufficiently
intelligible to the reader; it did not therefore seem necessary or
desirable to subdivide the passages merely for the sake of strict
classification._
_The small number of chapters given under the fifth class, treating
on the centre of gravity in roof-beams, bears no proportion to the
number of drawings and studies which refer to the same subject. Only
a small selection of these are reproduced in this work since the
majority have no explanatory text._
I.
ON FISSURES IN WALLS.
770.
First write the treatise on the causes of the giving way of walls
and then, separately, treat of the remedies.
Parallel fissures constantly occur in buildings which are erected on
a hill side, when the hill is composed of stratified rocks with an
oblique stratification, because water and other moisture often
penetrates these oblique seams carrying in greasy and slippery soil;
and as the strata are not continuous down to the bottom of the
valley, the rocks slide in the direction of the slope, and the
motion does not cease till they have reached the bottom of the
valley, carrying with them, as though in a boat, that portion of the
building which is separated by them from the rest. The remedy for
this is always to build thick piers under the wall which is
slipping, with arches from one to another, and with a good scarp and
let the piers have a firm foundation in the strata so that they may
not break away from them.
In order to find the solid part of these strata, it is necessary to
make a shaft at the foot of the wall of great depth through the
strata; and in this shaft, on the side from which the hill slopes,
smooth and flatten a space one palm wide from the top to the bottom;
and after some time this smooth portion made on the side of the
shaft, will show plainly which part of the hill is moving.
[Footnote: See Pl. CIV.]
771.
The cracks in walls will never be parallel unless the part of the
wall that separates from the remainder does not slip down.
WHAT IS THE LAW BY WHICH BUILDINGS HAVE STABILITY.
The stability of buildings is the result of the contrary law to the
two former cases. That is to say that the walls must be all built up
equally, and by degrees, to equal heights all round the building,
and the whole thickness at once, whatever kind of walls they may be.
And although a thin wall dries more quickly than a thick one it will
not necessarily give way under the added weight day by day and thus,
[16] although a thin wall dries more quickly than a thick one, it
will not give way under the weight which the latter may acquire from
day to day. Because if double the amount of it dries in one day, one
of double the thickness will dry in two days or thereabouts; thus
the small addition of weight will be balanced by the smaller
difference of time [18].
The adversary says that _a_ which projects, slips down.
And here the adversary says that _r_ slips and not _c_.
HOW TO PROGNOSTICATE THE CAUSES OF CRACKS IN ANY SORT OF WALL.
The part of the wall which does not slip is that in which the
obliquity projects and overhangs the portion which has parted from
it and slipped down.
ON THE SITUATION OF FOUNDATIONS AND IN WHAT PLACES THEY ARE A CAUSE
OF RUIN.
When the crevice in the wall is wider at the top than at the bottom,
it is a manifest sign, that the cause of the fissure in the wall is
remote from the perpendicular line through the crevice.
[Footnote: Lines 1-5 refer to Pl. CV, No. 2. Line 9 _alle due
anteciedete_, see on the same page.
Lines 16-18. The translation of this is doubtful, and the meaning in
any case very obscure.
Lines 19-23 are on the right hand margin close to the two sketches
on Pl. CII, No. 3.]
772.
OF CRACKS IN WALLS, WHICH ARE WIDE AT THE BOTTOM AND NARROW AT THE
TOP AND OF THEIR CAUSES.
That wall which does not dry uniformly in an equal time, always
cracks.
A wall though of equal thickness will not dry with equal quickness
if it is not everywhere in contact with the same medium. Thus, if
one side of a wall were in contact with a damp slope and the other
were in contact with the air, then this latter side would remain of
the same size as before; that side which dries in the air will
shrink or diminish and the side which is kept damp will not dry. And
the dry portion will break away readily from the damp portion
because the damp part not shrinking in the same proportion does not
cohere and follow the movement of the part which dries continuously.
OF ARCHED CRACKS, WIDE AT THE TOP, AND NARROW BELOW.