The Notebooks of Leonardo Da Vinci (19 page)

The question as to the composition of the atmosphere, which is
inseparable from a discussion on Aerial Perspective, forms a
separate theory which is treated at considerable length. Indeed the
author enters into it so fully that we cannot escape the conviction
that he must have dwelt with particular pleasure on this part of his
subject, and that he attached great importance to giving it a
character of general applicability.

General rules (289—291).

289.

The variety of colour in objects cannot be discerned at a great
distance, excepting in those parts which are directly lighted up by
the solar rays.

290.

As to the colours of objects: at long distances no difference is
perceptible in the parts in shadow.

291.

Which colour strikes most? An object at a distance is most
conspicuous, when it is lightest, and the darkest is least visible.

An exceptional case.

292.

Of the edges [outlines] of shadows. Some have misty and ill defined
edges, others distinct ones.

No opaque body can be devoid of light and shade, except it is in a
mist, on ground covered with snow, or when snow is falling on the
open country which has no light on it and is surrounded with
darkness.

And this occurs [only] in spherical bodies, because in other bodies
which have limbs and parts, those sides of limbs which face each
other reflect on each other the accidental [hue and tone] of their
surface.

An experiment.

293.

All colours at a distance are undistinguishable in shadow, because
an object which is not in the highest light is incapable of
transmitting its image to the eye through an atmosphere more
luminous than itself; since the lesser brightness must be absorbed
by the greater. For instance: We, in a house, can see that all the
colours on the surface of the walls are clearly and instantly
visible when the windows of the house are open; but if we were to go
out of the house and look in at the windows from a little distance
to see the paintings on those walls, instead of the paintings we
should see an uniform deep and colourless shadow.

The practice of the prospettiva de colori.

294.

In order to put into practice this perspective of the variation and
loss or diminution of the essential character of colours, observe at
every hundred braccia some objects standing in the landscape, such
as trees, houses, men and particular places. Then in front of the
first tree have a very steady plate of glass and keep your eye very
steady, and then, on this plate of glass, draw a tree, tracing it
over the form of that tree. Then move it on one side so far as that
the real tree is close by the side of the tree you have drawn; then
colour your drawing in such a way as that in colour and form the two
may be alike, and that both, if you close one eye, seem to be
painted on the glass and at the same distance. Then, by the same
method, represent a second tree, and a third, with a distance of a
hundred braccia between each. And these will serve as a standard and
guide whenever you work on your own pictures, wherever they may
apply, and will enable you to give due distance in those works. [14]
But I have found that as a rule the second is 4/5 of the first when
it is 20 braccia beyond it.

[Footnote: This chapter is one of those copied in the Manuscript of
the Vatican library Urbinas 1270, and the original text is rendered
here with no other alterations, but in the orthography. H. LUDWIG,
in his edition of this copy translates lines 14 and 15 thus: "
Ich
finde aber als Regel, dass der zweite um vier Funftel des ersten
abnimmt, wenn er namlich zwanzig Ellen vom ersten entfernt ist
(?)"
. He adds in his commentary: "
Das Ende der Nummer ist wohl
jedenfalls verstummelt
". However the translation given above shows
that it admits of a different rendering.]

The rules of aerial perspective (295—297).

295.

There is another kind of perspective which I call Aerial
Perspective, because by the atmosphere we are able to distinguish
the variations in distance of different buildings, which appear
placed on a single line; as, for instance, when we see several
buildings beyond a wall, all of which, as they appear above the top
of the wall, look of the same size, while you wish to represent them
in a picture as more remote one than another and to give the effect
of a somewhat dense atmosphere. You know that in an atmosphere of
equal density the remotest objects seen through it, as mountains, in
consequence of the great quantity of atmosphere between your eye and
them—appear blue and almost of the same hue as the atmosphere
itself [Footnote 10:
quado il sole e per leuante
(when the sun is
in the East). Apparently the author refers here to morning light in
general. H. LUDWIG however translates this passage from the Vatican
copy "
wenn namlich die Sonne (dahinter) im Osten steht
".] when the
sun is in the East [Footnote 11: See Footnote 10]. Hence you must
make the nearest building above the wall of its real colour, but the
more distant ones make less defined and bluer. Those you wish should
look farthest away you must make proportionately bluer; thus, if one
is to be five times as distant, make it five times bluer. And by
this rule the buildings which above a [given] line appear of the
same size, will plainly be distinguished as to which are the more
remote and which larger than the others.

296.

The medium lying between the eye and the object seen, tinges that
object with its colour, as the blueness of the atmosphere makes the
distant mountains appear blue and red glass makes objects seen
beyond it, look red. The light shed round them by the stars is
obscured by the darkness of the night which lies between the eye and
the radiant light of the stars.

297.

Take care that the perspective of colour does not disagree with the
size of your objects, hat is to say: that the colours diminish from
their natural [vividness] in proportion as the objects at various
distances dimmish from their natural size.

On the relative density of the atmosphere (298—290).

298.

Because the atmosphere is dense near the earth, and the higher it is
the rarer it becomes. When the sun is in the East if you look
towards the West and a little way to the South and North, you will
see that this dense atmosphere receives more light from the sun than
the rarer; because the rays meet with greater resistance. And if the
sky, as you see it, ends on a low plain, that lowest portion of the
sky will be seen through a denser and whiter atmosphere, which will
weaken its true colour as seen through that medium, and there the
sky will look whiter than it is above you, where the line of sight
travels through a smaller space of air charged with heavy vapour.
And if you turn to the East, the atmosphere will appear darker as
you look lower down because the luminous rays pass less freely
through the lower atmosphere.

299.

It is easy to perceive that the atmosphere which lies closest to the
level ground is denser than the rest, and that where it is higher
up, it is rarer and more transparent. The lower portions of large
and lofty objects which are at a distance are not much seen, because
you see them along a line which passes through a denser and thicker
section of the atmosphere. The summits of such heights are seen
along a line which, though it starts from your eye in a dense
atmosphere, still, as it ends at the top of those lofty objects,
ceases in a much rarer atmosphere than exists at their base; for
this reason the farther this line extends from your eye, from point
to point the atmosphere becomes more and more rare. Hence, O
Painter! when you represent mountains, see that from hill to hill
the bases are paler than the summits, and in proportion as they
recede beyond each other make the bases paler than the summits;
while, the higher they are the more you must show of their true form
and colour.

On the colour of the atmosphere (300-307).

300.

I say that the blueness we see in the atmosphere is not intrinsic
colour, but is caused by warm vapour evaporated in minute and
insensible atoms on which the solar rays fall, rendering them
luminous against the infinite darkness of the fiery sphere which
lies beyond and includes it. And this may be seen, as I saw it by
any one going up [Footnote 5: With regard to the place spoken of as
M'oboso
(compare No. 301 line 20) its identity will be discussed
under Leonardo's Topographical notes in Vol. II.] Monboso, a peak of
the Alps which divide France from Italy. The base of this mountain
gives birth to the four rivers which flow in four different
directions through the whole of Europe. And no mountain has its base
at so great a height as this, which lifts itself almost above the
clouds; and snow seldom falls there, but only hail in the summer,
when the clouds are highest. And this hail lies [unmelted] there, so
that if it were not for the absorption of the rising and falling
clouds, which does not happen twice in an age, an enormous mass of
ice would be piled up there by the hail, and in the middle of July I
found it very considerable. There I saw above me the dark sky, and
the sun as it fell on the mountain was far brighter here than in the
plains below, because a smaller extent of atmosphere lay between the
summit of the mountain and the sun. Again as an illustration of the
colour of the atmosphere I will mention the smoke of old and dry
wood, which, as it comes out of a chimney, appears to turn very
blue, when seen between the eye and the dark distance. But as it
rises, and comes between the eye and the bright atmosphere, it at
once shows of an ashy grey colour; and this happens because it no
longer has darkness beyond it, but this bright and luminous space.
If the smoke is from young, green wood, it will not appear blue,
because, not being transparent and being full of superabundant
moisture, it has the effect of condensed clouds which take distinct
lights and shadows like a solid body. The same occurs with the
atmosphere, which, when overcharged with moisture appears white, and
the small amount of heated moisture makes it dark, of a dark blue
colour; and this will suffice us so far as concerns the colour of
the atmosphere; though it might be added that, if this transparent
blue were the natural colour of the atmosphere, it would follow that
wherever a larger mass air intervened between the eye and the
element of fire, the azure colour would be more intense; as we see
in blue glass and in sapphires, which are darker in proportion as
they are larger. But the atmosphere in such circumstances behaves in
an opposite manner, inasmuch as where a greater quantity of it lies
between the eye and the sphere of fire, it is seen much whiter. This
occurs towards the horizon. And the less the extent of atmosphere
between the eye and the sphere of fire, the deeper is the blue
colour, as may be seen even on low plains. Hence it follows, as I
say, that the atmosphere assumes this azure hue by reason of the
particles of moisture which catch the rays of the sun. Again, we may
note the difference in particles of dust, or particles of smoke, in
the sun beams admitted through holes into a dark chamber, when the
former will look ash grey and the thin smoke will appear of a most
beautiful blue; and it may be seen again in in the dark shadows of
distant mountains when the air between the eye and those shadows
will look very blue, though the brightest parts of those mountains
will not differ much from their true colour. But if any one wishes
for a final proof let him paint a board with various colours, among
them an intense black; and over all let him lay a very thin and
transparent [coating of] white. He will then see that this
transparent white will nowhere show a more beautiful blue than over
the black—but it must be very thin and finely ground.

[Footnote 7:
reta
here has the sense of
malanno
.]

301.

Experience shows us that the air must have darkness beyond it and
yet it appears blue. If you produce a small quantity of smoke from
dry wood and the rays of the sun fall on this smoke, and if you then
place behind the smoke a piece of black velvet on which the sun does
not shine, you will see that all the smoke which is between the eye
and the black stuff will appear of a beautiful blue colour. And if
instead of the velvet you place a white cloth smoke, that is too
thick smoke, hinders, and too thin smoke does not produce, the
perfection of this blue colour. Hence a moderate amount of smoke
produces the finest blue. Water violently ejected in a fine spray
and in a dark chamber where the sun beams are admitted produces
these blue rays and the more vividly if it is distilled water, and
thin smoke looks blue. This I mention in order to show that the
blueness of the atmosphere is caused by the darkness beyond it, and
these instances are given for those who cannot confirm my experience
on Monboso.

302.

When the smoke from dry wood is seen between the eye of the
spectator and some dark space [or object], it will look blue. Thus
the sky looks blue by reason of the darkness beyond it. And if you
look towards the horizon of the sky, you will see the atmosphere is
not blue, and this is caused by its density. And thus at each
degree, as you raise your eyes above the horizon up to the sky over
your head, you will see the atmosphere look darker [blue] and this
is because a smaller density of air lies between your eye and the
[outer] darkness. And if you go to the top of a high mountain the
sky will look proportionately darker above you as the atmosphere
becomes rarer between you and the [outer] darkness; and this will be
more visible at each degree of increasing height till at last we
should find darkness.