Notebooks of Leonardo da Vinci

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.

That smoke will look bluest which rises from the driest wood and
which is nearest to the fire and is seen against the darkest
background, and with the sunlight upon it.

303.

A dark object will appear bluest in proportion as it has a greater
mass of luminous atmosphere between it and the eye. As may be seen
in the colour of the sky.

304.

The atmosphere is blue by reason of the darkness above it because
black and white make blue.

305.

In the morning the mist is denser above than below, because the sun
draws it upwards; hence tall buildings, even if the summit is at the
same distance as the base have the summit invisible. Therefore,
also, the sky looks darkest [in colour] overhead, and towards the
horizon it is not blue but rather between smoke and dust colour.

The atmosphere, when full of mist, is quite devoid of blueness, and
only appears of the colour of clouds, which shine white when the
weather is fine. And the more you turn to the west the darker it
will be, and the brighter as you look to the east. And the verdure
of the fields is bluish in a thin mist, but grows grey in a dense
one.

The buildings in the west will only show their illuminated side,
where the sun shines, and the mist hides the rest. When the sun
rises and chases away the haze, the hills on the side where it lifts
begin to grow clearer, and look blue, and seem to smoke with the
vanishing mists; and the buildings reveal their lights and shadows;
through the thinner vapour they show only their lights and through
the thicker air nothing at all. This is when the movement of the
mist makes it part horizontally, and then the edges of the mist will
be indistinct against the blue of the sky, and towards the earth it
will look almost like dust blown up. In proportion as the atmosphere
is dense the buildings of a city and the trees in a landscape will
look fewer, because only the tallest and largest will be seen.

Darkness affects every thing with its hue, and the more an object
differs from darkness, the more we see its real and natural colour.
The mountains will look few, because only those will be seen which
are farthest apart; since, at such a distance, the density increases
to such a degree that it causes a brightness by which the darkness
of the hills becomes divided and vanishes indeed towards the top.
There is less [mist] between lower and nearer hills and yet little
is to be distinguished, and least towards the bottom.

306.

The surface of an object partakes of the colour of the light which
illuminates it; and of the colour of the atmosphere which lies
between the eye and that object, that is of the colour of the
transparent medium lying between the object and the eye; and among
colours of a similar character the second will be of the same tone
as the first, and this is caused by the increased thickness of the
colour of the medium lying between the object and the eye.

307. OF PAINTING.

Of various colours which are none of them blue that which at a great
distance will look bluest is the nearest to black; and so,
conversely, the colour which is least like black will at a great
distance best preserve its own colour.

Hence the green of fields will assume a bluer hue than yellow or
white will, and conversely yellow or white will change less than
green, and red still less.

_VII._

_On the Proportions and on the Movements of the Human Figure._

_Leonardo's researches on the proportions and movements of the human
figure must have been for the most part completed and written before
the year_ 1498; _for LUCA PACIOLO writes, in the dedication to
Ludovico il Moro, of his book_ Divina Proportione, _which was
published in that year:_ "Leonardo da venci ... hauedo gia co tutta
diligetia al degno libro de pictura e movimenti humani posto fine".