'The air moves like a river and carries the
clouds with it; just as running water carries
all the things that float upon it!
Surface is the name given to the boundaries of bodies with the air or I
would rather say of the air with bodies, that is what is enclosed between
the body and the air that surrounds it; and if the air makes contact with
the body there is no space to put another body there; consequently it
may be concluded that surface has no body and therefore no need of
Surface is the name given to that which divides bodies from the air
which surrounds them; or as you may prefer to say which divides or
separates the air from the things which are located within it.
And if the atmosphere and the bodies which are enclosed within it
are in perpetual contact and there is not any space between them, the
surface being that which shows the shape of the bodies this surface has
existence of itself. And if the atmosphere and the body are touching
each other no space will remain there, so we conclude that the surface
has existence and not space. Consequently this surface is equal to noth-
ing, and all the nothingness of the world is equal to the smallest part
if there can be a part. Wherefore we may say that surface, line, and
point are equal as between themselves, and each is of itself equal to the
other two joined together.
Surface is the name of that division which the body of the air makes
with the bodies which are enclosed within it. And it does not partake
of the body by which it is surrounded, nor of that which it surrounds;
on the contrary it is the actual contact which these bodies make to-
Therefore if these bodies are in continual contact it is necessary that
nothing should interpose between them, and consequently the surface,
which is enclosed there, is nothing. This surface has name and not
substance because that which has substance has place. Not having place
it resembles nothingness which has name without substance; conse-
quently the part of nothing not having anything except the name and
not the substance this part is equal to the whole; so that by this we
conclude that the point and the line are equal to the surface.
c.a. 68 v. a
ELEMENT OF FIRE. MIDDLE REGION OF THE ATMOSPHERE
The atmosphere interposed between the fire and the water partici-
pates in the water and the fire, but so much more in one than the other
as it is nearer one than the other. It follows that the less it participates
in each the more remote it is from them. And this remoteness occurs in
the middle region of the atmosphere; therefore this middle region is
in the first stage of cold. From which it follows that that part of the
cloud which is in closest contact with the middle region becomes cold-
est; consequently the warmth of the sphere of fire of this cloud which
is the attracter and mover is of less potency, and from this it follows
that the movements of the particles of moisture which form the clouds
are slower; and from this it follows that, in the process of these par-
ticles of moisture rising, the nearer they come to the vicinity of this
middle region the slower the movement becomes, and the movement
of that which follows is swifter than it, and consequently it overtakes
it. And it often happens that it strikes underneath and mingles with it
and thus increases its quantity and weight. The atmosphere in conse-
quence not being able to support it makes way for it to descend, and
in doing this it strikes all the drops which interrupt its course, and in-
corporates many in itself, and acquiring weight it acquires velocity in
its descent [. . . .]. And this is the reason why after it has penetrated
the whole of the cloud in every stage of descent its pace will become
slower, and there will be many occasions when these particles will not
arrive at the ground. If then these particles at the highest part of their
height acquire so much gravity that the weight produces a swift de-
scent, then without doubt this movement will increase their size, inas-
much as this speed will cause it to overtake the drops which are de-
scending below it and incorporate them in itself, and this will bring
about an increase of weight at every stage of its descent.
The descent of the drops which strike together without wind will
not be straight but at an angle.
This is proved by the fact that if two bodies strike one another in
the air the one which is less in bulk will be diverted more from its
And if two particles of dew or of quicksilver varying in size become
joined together each will be removed from its position and the propor-
tion of their movements will be as that of their size.
The drop of that liquid is of the most perfect roundness which is of
less . . .
Why if two spherical liquids unequal in quantity come to the be-
ginning of contact with each other does the greater draw to itself the
lesser and incorporate it immediately without destroying the perfection
of its own roundness.
It is difficult to give an answer; but I will not for this reason refrain
from stating my opinion. Water clothed with atmosphere naturally
desires to be united in its sphere, because in such a position it is de-
prived of gravity, which gravity is double; for the whole has a gravity
which depends on the centre of the elements, and there is a second
gravity dependent on the centre of this watery sphere, for if it were not
so it would form by itself a half sphere only which is that which stands
from the centre upwards; and I do not perceive that the human in-
tellect has any means of acquiring perception of this except by saying
as one says of the action of the magnet when it draws the iron, that
such virtue is a hidden property of which there are in nature an in-
But it may be asked why there is greater perfection in the little
sphere of the liquid than in the large one. To this the reply is that the
little drop has a lightness which more resembles the atmosphere that
surrounds it than the large drop has, and from the fact of this small
difference it is more sustained from its centre downwards by this
atmosphere than the large drop. And as a proof of this, one may take
as an instance the little drops which are so small in shape as to be of
themselves almost invisible but which are visible when there are a large
quantity together; and these are the particles which go to form clouds
Why the atmosphere when it has been submerged rises enveloped in
a sheet of water. Which settles on its surface in the shape of a half
And if it is slimy water it moves through the atmosphere in the form
of a sphere.
[Dm wing] Bubble or rather vesicle of water.
You will make an experiment with these bubbles of water which
over a little water set in a basin produce by means of the solar rays
images of the form of a cross on the bottom of this basin.
c.a. 75 v. a
Air and fire are capable of an infinite amount of compression as is
seen with mortar-pieces and thunderbolts. c.a. 97 v. a
The body of the air is filled with an infinite number of radiant
pyramids formed by the objects situated in it, and these pyramids inter-
secting and interweaving without displacement one of another blend
together in their separate courses throughout the whole of the sur-
rounding air; and they are of equal power, and all have as much
capacity as each one and each has as much as all; and through them
the image of the body is carried all into the whole and all into a part,
and each receives of itself in its every smallest part the whole cause.
c.a. 101 v. b
The movement of the thunderbolt which originates in the cloud is
curved, because it bends from thickness to thinness, this thickness being
occasioned by the fury of the aforesaid movement. For this thunderbolt
not being able to extend in the direction in which it commenced, bends
into the course that is freest and proceeds by this until it has created
the second obstacle, and so following this rule it continues on to the
end. c.a. 121 r. b
Why flame does not occur except above some space where there is
smoke, and why it does not strike except through its smoke. This hap-
pens because the flames as they strike the air divide in pyramids, con-
nected by ends which curve concavely and not convexly, and air within
water does the same. c.a. 131 r. b
That the atmosphere attracts to itself like a magnet all the images of.
the things which surround it, and not only their bodily shapes but also
their nature, is clearly to be seen in the case of the sun, which is a hot
and luminous body. All the atmosphere which is exposed to its influ-
ence is charged in all its parts with light and heat, and it all receives
within itself the shape of that which is the source of this heat and radi-
ance and does the same also in each minutest part. The north star is
shown to do the same by the needle of the compass; and each of the
planets does the like without itself undergoing any diminution.
Among the products of the earth the same is found to happen with
musk and other scents. c.a. 138 v. b
The cloud carried by the warmth which is shut up within it thrusts
itself towards [....] disc of fire, comes to the cold region of the air,
which is frozen on the outer side but is not frozen within, because the
warmth which has carried it up there preserves it from such cold; and
this brings to pass three circumstances, the first being the evaporation
of the moisture which after being pent up through the cold separates
and dissolves into vapour and produces a raging wind; the second is
the rain that is produced by the accumulation of the particles of moist
vapour, for those of swift movement driven by the heat clash against
those which are moving more slowly, and as they encounter that part
of the cloud which becomes cold towards its extremities the particles
of the moisture fasten themselves together and acquire weight, and so
it descends to earth in big drops; and on the very extremity of this
cloud the particles of moisture are continually freezing into balls of
various sizes, and these cannot expand because of the intensity of the
cold, but come together with swift movement at the spot where the
sphericity of the drop is produced, and therefore the hail is composed
of [....] of many roundnesses which are joined together.
c.a. 162 r. a
The elements are changed one into another, and when the air is
changed into water by the contact it has with its cold region this then
attracts to itself with fury all the surrounding air which moves furi-
ously to fill up the place vacated by the air that has escaped; and so
one mass moves in succession behind another, until they have in part
equalised the space from which the air has been divided, and this is
But if the water is changed to air then the air which first occupied
the space into which the aforesaid increase flows must needs yield place
in speed and impetus to the air which has been produced, and this is
The mist that is in the wind is produced by heat, and it is smitten
and banished by the cold, and this cold drives it before it, and from
where it has been driven the warmth is left cold. And because the mist
which is driven cannot turn upwards because of the cold that presses it
down, and cannot turn downwards because of the heat that raises it up,
it therefore becomes necessary for it to proceed across, and I for my
part consider that it has no movement of itself, for as the said powers
are equal they confine the middle substance equally, and should it
chance to escape the fugitive is dispersed and scattered in every direc-
tion, just as with a sponge filled with water, which is squeezed so that
the water escapes out of the centre of the sponge in every direction.
So therefore does the northern wind become the producer of all the
winds at one and the same time. c.a. 169 r. a
The north wind comes to us from high and frozen places and there-
fore it cannot give off moisture, and consequently it is pure and clean,
because it is cold and dry, and for this reason it is very light in itself
but its speed makes it powerful wherever it strikes.
The south wind has not the same purity, and since it is warm and
dry it dissolves the thicknesses of the watery vapours which the Medi-
terranean Sea exhales, and these then follow in the wake of this wind
and become dissolved in it; and so for this reason this wind as it strikes
Europe comes to be warm and damp and heavy in its nature, and
although its movement is sluggish its stroke is no less powerful than
that of the north wind.
Every wind is by nature cold and dry but it takes to itself as many
different attributes as are those of the places through which it passes,
leaving behind it in passing dampness and cold to the dry and hot
places and taking from these same hot dry places their dryness and
heat. So in its movement in each region it puts on different attributes,
and in becoming warm and dry it weakens its power, and in resuming
the things it had left behind it resumes the aforesaid forces together
with them, for when there is the same swiftness of movement that
thing which is of greater weight will give a greater percussion, and so
conversely the lighter thing will give a less percussion.
When in summer the sun returns to the parts of Africa the humidity
which had been increased there by the winter becomes dissolved and its
bulk increases, and it searches in fury for places to contain this increase.
And this is the south wind, which in autumn drives the maritime
vapours of the Mediterranean before it, and condenses them above our
regions, until they fall down again through lack of power to maintain
When many winds strive together then the waves of the sea have not
a free course, but they clash together and raise themselves up and at
times cause ships to founder; and in such a contest the stronger wind
will be the victor through its being lighter and less interwoven or
mingled with the other winds. c.a. 169 v. a
All objects have all their images and likenesses projected and
mingled together throughout the whole extent of the surrounding
atmosphere. The image of every point of their bodily surfaces exists in
every point of this atmosphere, and all the images of the objects are in
every point of this atmosphere. The whole and a part of the likeness
of the atmosphere exists in every point of the surface of the objects
which are over against it. Therefore the part and the whole of the
images of the objects appear in all and in each part of the atmosphere
which is opposite to them; and the substance of the atmosphere is seen
reflected in the whole and in each part of the surface of these objects.
Therefore clearly we may say that the likeness of each object either
whole or in part is interchangeably in each part and in the whole of the
objects opposite to it, as is seen with mirrors when placed one opposite
to another. c.a. 179 v. c
Those winds which descending scour the parts of the mountains that
lean towards the sea, penetrate to its bed and make waves, with sides
that resemble the shores from which they descend, and these waves
consequently have often deep narrow spaces between them, as I said
in the book on the movement of water. And this tempest lasts only a
short time after the stroke of the wind, lor alter it has struck it leaps
hack into the air until it finds the other wind, and striking against this
it compresses it and again leaps downward after the manner oi the
rivers as they strike the shores.
On the summits of the mountains the wind is of great density, and
in the mouths of the valleys when the mountains which shut in these
valleys are of great height. The entry of opposite winds one beneath
the other with contrary movements may occur for two reasons, namely
either through the reflex movement of the wind which turns back after
having struck upon the mountains, or by the clashing together when
the weaker parts of opposing winds strike against the stronger parts.
The revolutions or eddies of the winds are born in the winds as they
open out in the embrace of the mountains or of some building, and
afterwards join together and strike with impetus; and their reflex
movements are not made in a straight line, for it is checked in its own
sphere, being moved by a substance like itself which has the power to
check and bend its direct impetus. So therefore this wind not being
able to extend proceeds to exhaust its impulse by a [curving] move-
ment, and goes upwards in order to consume its impetus, this being
necessary for three reasons; firstly because it cannot at once turn on
the very lines of its descent, secondly because they strike at angles less
than right angles, and because they cannot leap back on lines equal to
those of their incidence. c.a. 180 v. a
[Cloud, wind and thunderbolt]
As water flows in different directions out of a squeezed sponge, or
air from a pair of bellows, so it is with the thin transparent clouds that
have been driven up to a height through the reflection occasioned by
the heat, the first part which finds itself uppermost being that which
comes first to the cold region, and here remaining through the cold and
dryness awaits its companion. That part below as it ascends towards the
part that is stationary treats the air which happens to be in the centre
as though it was a syringe, and this then escapes crosswise and down-
wards, not going upwards because it finds the cloud so thick that it
cannot penetrate it.
So for this reason all the winds that make war upon the earth's sur-
face come down from above, and as they strike upon the resisting earth
they produce a movement of recoil, and this as it desires to raise itself
up again to a height finds there the other wind, which descends and
subdues its ascent, whereby the said upward movement is constrained
to break its natural order, and taking a transverse route it pursues a
violent course which grazes incessantly the surface of the earth.
And when the aforesaid winds strike upon the salt waters the form
is clearly visible, in the angle that is created by the line of incidence
and that of the recoil from which proceed the proud menacing and
engulfing waves, of which the one for the most part is the cause of
Here someone perhaps may think to censure me by putting forward
as against my contention as to the winds the argument that these can-
not be produced by the clouds because then it would be necessary for
one to remain stationary and give movement to another, and this does
not appear to be so, because when the north wind blows the clouds all
collect together and fly before it. The reply to this is that when the air
is still and a full company of clouds have risen to a height, and there
above as has been said press themselves together, they squeeze out so
much air from themselves, which through the violence exerted creates
such movement in the air, that as you may see it communicates its
movement to the other lesser clouds. And as they also drive the air
forwards in the same way they even furnish themselves with a reason
for greater flight; for when a cloud either finds itself in the midst of
others or apart from them, if it produces the wind behind itself that
air which is between it and its neighbour following comes to multiply,
and by multiplying acts in the same way as the powder does in the
mortar, for this expels from the position near to it the less heavy body
and the lighter weight. And this being the case it follows that the
cloud in driving the wind towards the others which offer resistance is
the cause of putting these themselves to flight. And by sending this
vanguard of the winds before itself it also adds volume to the rest. And
if it should send them crosswise it would form a kind of rotatory circle
around some cloud and then return in concert with the others.
As the natural warmth spread through the human limbs is driven
back by the surrounding cold which is its opposite and enemy, and
flowing back to the lake of the heart and the liver fortifies itself there,
making of these its fortress and defence, so the clouds being made up
of warmth and moisture, and in summer of certain dry vapours, and
finding themselves in the cold dry region, act after the manner of cer-
tain flowers and leaves which when attacked by the cold hoar-frost
press themselves close together and offer a greater resistance.
So these in their first contact with the cold air commence to resist
and not to wish to pass farther forward; the others below continue
constantly to rise, the part above being stationary proceeds to thicken,
the warmth and dryness recede to the centre, the part above abandoned
by the warmth commences to freeze or to express it more exactly to
dissolve, and as the clouds below continue to rise their warmth is
brought nearer to the cold and so being constrained to reduce itself to
its primary element is suddenly transformed into fire, and this twines
itself among the dry vapour and in the centre of the cloud makes a
great increase, and as it kindles itself within the cloud which has be-
come cool it makes a noise that resembles that of water falling on boil-
ing pitch or oil, or of molten copper when plunged into cold water.
Even so driven forth by its opposite it shatters the cloud that would
withstand it, and hurtling through the air breaks and destroys every-
thing that opposes it, and this is the thunderbolt. c.a. 212 v. a
The air is compressible to infinity, and this is shown by the extremely
swift movement of the radiance which produces the mighty thunder
of the heavens, which bends and twists itself in different directions so
much the more as the air and cloud before it is compressed and . . .
Example of thunder
The process of evaporation of water thrown upon burning coals is
as that of the fire when kindled among the clouds which evaporate
with such fury as to restrict the course of the brightness that has been
created; that is to say that as the water is changed into vapour and
becomes steam as it increases so the cloud evaporates and becomes
changed into air, which by its increase hems in and restricts the flame
which is produced in it. c.a. 213 r. a
Flame has its beginning and end in smoke.
The smoke out of which the flame is produced is of much greater
heat than the smoke in which this flame ends, because in the first
smoke there is the nascent power of the flame, and the last is the dying
away of the same flame.
Wood that is young and dry will produce smoke of a more intense
blue than wood that is old and damp.
The blue flame which is midway between the darkness and the light
comes into being between the nutritive portion of the candle and its
flame, and is of greater heat and radiance than the smoke and of less
heat and radiance than its flame; and the vapour cannot transform
itself into flame, without first becoming changed to this blue colour,
and this is known in the case of smoke.
Flame is condensed smoke, formed out of the meeting together of
the air that is in this blue smoke, which . . .
The blue smoke is the transit of the material nutriment that is the
grease that is in the candle. The white smoke that surrounds the vestige
of the flame is the spiritual transit of the flame of this candle, which in
its lowest part is mingled with the topmost part of the aforesaid blue
smoke, and in the upper part is mingled with the smoke which pro-
ceeds from the flame of the candle. c.a. 237 v. a
Write why the campanile shakes at the sound of its bells.
c.a. 242 v. a
The southern winds are more powerful in the northern than in the
southern regions and in summer than in winter; and this is because
the sun dissolves all the moisture that rises from the Mediterranean
Sea, which cannot dissolve during the cold of winter, and of these
vapours few rise and these few are dissolved in water. But when the
sun passes beyond the circle of the equinox, and it is winter here at
hand and summer over yonder the sun dissolves all the vapours as
they rise, so that they glide in aerial waves as far as the chief [moun-
tains] of Europe, and there coming upon the cold in the autumn they
turn into rain, and in the winter they are knit together in snow, and
fall in snowstorms and so proceed little by little to stifle the breath of
the aforesaid winds. c.a. 246 v. a
Where flame cannot live no animal that draws breath can live.
Excess of wind puts out flame, moderate wind nourishes it.
I Of flame and wind]
The bottom part of the flame is the first beginning of this flame
through which passes all its nutriment of fat; and this is of so much
less heat than the rest of the flame as it is of less brightness; and it is
blue in colour and is the part in which its nutriment is purged and
That has the brighter flame, and this is the first to come into exist-
ence when the flame is created, and it comes into existence in spherical
shape, and after a span of life produces above itself a very small flame,
radiant in colour and shaped like a heart with its point turned to the
sky, and this proceeds to multiply continuously on towards infinity,
by means of its acquiring possession of the substance that feeds it.
The blue flame is formed of spherical shape because it is not of such
great heat as exceeds the lightness of the air; and for this reason it
does not in itself form a pyramidal figure, but remains in spherical
shape until it has warmed sufficiently the air which surrounds it, and
because the chief warming of the air is above the principal heat of this
blue flame, this heat being produced by that part where the natural
desire of the flame is to move itself, that is to the sphere of fire by the
shortest way. Therefore the fire comes into existence in the upper part
of the blue spherical flame, in a small round figure, the roundness of
which immediately undergoes some extension and assumes the shape
of a heart, of which the point is turned towards the sky. And this shape
immediately and with swift dilation overcomes the power that feeds it,
and penetrates the air which serves it as a covering. But this blue colour
remains in the base of this flame as may be seen in the light of the
candle; and this comes to pass because in this position the flame is
always less warm than elsewhere, because there is the first encounter
which provides the nourishment of the flame with this flame, and it
is there that the first heat is produced, and this is feebler and causes
less warmth because it is only the commencement of the heat. . . .
That wind will be of briefer movement which is of more impetuous
beginning; and this the fire has taught us as it bursts forth from the
mortars, for it shows us the form and speed of the movement in the
smoke as it penetrates the air opposite to it in brief and spreading
But the impetuosity of the wind is fitful, as is shown by the dust that
it raises in the air in its various twists and turns. One perceives also
in the chains of the Alps how the clashing together of the winds is
caused by the impetus of various forces. One sees also how the flags
of ships flutter in different ways; how on the sea one part of the water
is struck and not another; and the same thing happening in the pi-
azzas and on the sandbanks of the rivers, where the dust is swept
together furiously in one part and not in another. And since these
effects give us experience of the nature of their causes we can say with
certainty that the wind which has the more impetuous origin will have
the briefer movement, from the experience that has been referred to
above as to the brief movement of the smoke from the mouth of the
mortar. And this arises from the resistance that the air makes on being
compressed by the percussion of this smoke, which also itself, as has
been seen clearly shows compression when it offers resistance to the
wind. But if the wind is of slow movement it will extend a long way
in a straight course, because the air penetrated by it will not become
condensed opposite to it and thus thwart its movement, but will readily
expand spreading its course over a very great space.
OF EDDYING WINDS
When a wind has been divided by mountains or other erections, if
on coming together again it should assume the shape of a rectangle, the
movement which it makes after this reunion will be of a rotatory nature
in the shape of a twisted column; and if the winds which are thus re-
united should be equal then this column will not change its position;
but if the winds are unequal the column will move in the direction of
the weaker wind. c.a. 270 v. a
Fire or other heat lightens moisture and makes it lighter than the
air; for which cause this moisture rises to the middle region of the air,
and finding there the maximum cold of the air, the fire or heat infused
through this cloud flies towards the centre, and there becoming strong
separates the moist vapour from the dry, and it is for this reason that
the fire becomes kindled there and turns into steam a great part of the
moisture which is round about this fire. And this process of vaporisa-
! i) Wr/t ,-f - "*
JM » >/»«. ?*««' ''*'"•• I
CHILD IN WOMB
Royal Library, Windsor
lion as it increases restricts the fire, and the fire thus restricted acquires
potency and bursts through the cloud in the part in which it is weakest,
and forms a gate tor the movement of the thunderbolt and the wind.
Whether the wind is caused amid the air, and cannot make any move-
ment unless it is supported in the place where it resists by the opposite
side of the movement, as is seen to be the case with the rays driven by
the fire, for through the percussion that the fire makes in the air which
offers some resistance to it, these fly more slowly than this fire; and if
this were not the case such ray would be without movement.
Further we may say: the wind moves in a straight line and not as
Aristotle would have it in a circular line; and this we learn from the
movement of a storm at sea when there is no wind, for it is a sign that
such wind follows its straight line leaving below it the curve of the sea.
Why the clouds are formed with various round shapes which are
separated at different spaces one from another:
The movements of the air spring from the dispersal and collection
Heat separates and disperses and cold assembles and freezes or
condenses. c.a. 279 r. b
OF THE DROPS THAT FORM IN THE AIR
Drops are formed in the air through the mists or clouds by various
movements, as when they encounter each other and become condensed
or unite in the movement of the same cloud in the same direction,
when one part of the cloud is swifter or slower than the other; for as
the swifter part is behind the slower it conquers it in its course and
overtakes it, and condenses it and out of many small drops makes one
large one, and this acquires weight and falls. But unless the drops are
so formed as to be of considerable size they are consumed by the fric-
tion they make with the air as they traverse it. c.a. 292 r. a
The moist wind which is found in the caverns that have both en-
trance and exit can produce water, and this especially when these
caverns have twisted and shapeless sides; but this production of water
is not permanent in its effect for when the wind is lacking the supply
ceases, and if a contrary wind should enter by the opposite mouth of
this cavern the water which bathed its walls will become evaporated
and changed into air; and if this cavern have an entrance but no exit
the moist wind which strikes its mouth could not enter there unless
the air within that filled it were expelled. And since two opposite
movements cannot penetrate each other it must needs be that the air
that dwells within the cavern will find it easier to be condensed than
to escape, and for this reason it will resist the entrance of the wind
which beats upon it. c.a. 296 v. b
The images of every visible object are all infused in all the air over
against them, and are all separated in every part of the same air.
The images of objects which confusedly as they mingle fill with
themselves the air over against them are all in all this air and all in
every part of it. c.a. 345 r. b
Every body situated within the luminous air fills the infinite parts of
this air circle-wise with its images, and it is all in all and all in the part,
and goes lessening its images throughout the equidistant surrounding
space like a . . .
Of the four elements and two . . .
1. The stone thrown into the water becomes the centre of various
circles, and these have as their centre the spot which has been struck.
2. And the air in the same way is filled with circles, the centres of
which are the sounds and voices formed within them.
How the various circles of the water form round the spot which has
been struck by the stone.
The stone where it strikes the surface of the water creates circles
round itself which proceed to expand so much that they die away; and
the air also when struck by a voice or a noise departing circle-wise in
the same way proceeds to lose itself so that the nearest perceives better,
and the more distant hears less.
COMPARISON OF HOW THE THINGS COME TO THE EYE
Just as the air struck by the voice, the water by the stone proceed
in circular movement revealing their cause, and these circles make their
centre in the place which has been struck, and the farther away they
proceed from it . . . c.a. 373 r. b
The fifth essence is infused through the air as is the clement of fire,
although each of these may have its reason in itself or through itself;
and since each particle is supplied with nutritive matter it acquires
growth and increase of form; and if the nourishment be taken away
from them they suddenly abandon this body and return to their first
nature. c.a. 393 v. a
The air is all in all and all in its image in the part set over against it.
If within the air there be no opaque body the whole of it has a
capacity which extends over the whole and over the part, and the part
has a capacity which extends over the part and over the whole.
Therefore we may say that the air is all entwined in all of it, and is
filled with the infinite rays of the images of the bodies which are
situated within it, and this air is full of an infinite number of points,
and every point is indivisible, and the parts of this indivisibility of all
the images of the parts of bodies set over against them have capacity,
and in these points they are entirely united and entirely divided and
separated without confusion the one from the other.
And the pyramids of the images are spread throughout the whole of
this air without occupation of space the one of the other, and each for
itself, and are all divided through all and united through all.
And although the images approach the eye in the form of pyramids
the eye is not conscious of this unless it forms a pyramid opposite to the
thing seen. c.a. 396 r. b
Just as the stone thrown into the water becomes the centre and cause
of various circles, and the sound made in the air spreads itself out in
circles, so every body placed within the luminous air spreads itself out
in circles and fills the surrounding parts with an infinite number of
images of itself, and appears all in all and all in each smallest part.
a 9 v.
I say that cold proceeds from two causes; the first is from the air
being deprived of heat; the second is from the movement of the air.
The air of itself is cold and dry and it is void of all matter or vapours,
and it changes readily or to put it more exactly steeps itself in the
nature and image of the things which touch it and which it has oppo-
site to it. As regards things that touch it, when a pungent thing such
as musk or sulphur or some other powerful odour touches it it in-
stantly permeates it; also if a luminous body be placed within it the
whole of the surrounding air will be lit up.
Now to return to this question of cold I say that just as the many
rays of a concave mirror converging at one point produce an extreme
of heat even so many bellows blowing on the same point produce an
extreme cold. a 20 r.
[ Concerning visibility ]
Men naturally if they wish to know whether the rain has com-
menced look in the air that is between the eye and some dark place;
and then the fine threads which the minute drops of water cause to
appear in the air being lighted up are easily visible against a dark
background. But men reckon the threads which are near at hand and
first as though they were the last and almost touched the dark place,
not perceiving that this dark place is sometimes so remote that it
would not be possible to be able to see a neighbouring tower there.
c 5 v.
The colours of the middle of the rainbow mingle with each other.
The bow itself is neither in the rain nor in the eye that sees it, al-
though it is produced by the rain, the sun, and the eye.
The rainbow is invariably seen by the eye which is situated between
the rain and the body of the sun, and consequently when the sun is in
the east and the rain in the west the rainbow is produced upon the
western rain. e cover 1 v.
OF THE POWER OF A VACUUM FORMED
I saw at Milan a thunderbolt strike the Torre della Credenza on its
northern side. It travelled along it with a slow movement and then all
at once parted from the tower and carried with it and tore away a part
of the wall, three braccia in breadth and length and two in depth. The
wall was four braccia in width and was built of old bricks which were
thin and small. It was torn away through the vacuum caused by the
flame of the thunderbolt. I have found traces of the same power in the
rocks of the high Apennines and especially in the rock of La Vernia.
The same thing occurs with a cannon in the vacuum left by the flame.
e 1 r.
Which will darken the earth more? A thick dark cloud that comes
between the earth and the sun, or a quantity of water equal in bulk to
the said cloud, the cloud touching the ground as does the water?
f 46 v.
[Of fire and light]
Fire would increase to infinity if the wood were indefinitely in-
The light of the candle will be proportionately less as it is placed
in a colder spot. f 56 r.
OF THE WIND
The air moves like a river and carries the clouds with it; just as
running water carries all the things that float upon it. This is proved
because if the wind were to penetrate through the air and drive the
clouds these clouds would be condensed between the air and the mov-
ing force and would take a lateral impress from the two opposing
extremities, just as wax does when pressed between the fingers.
OF THE MOVEMENT OF AIR
Air moves when it is drawn away to fill a vacuum, or driven by the
rarefaction of the humidity of the clouds. g 10 r.
[Reflex course of wind and water]
The reflex wind as it turns back upon its course subdues the oncom-
ing wind until this reflex wind becomes enfeebled, and then it regains
its force when it becomes joined with the falling movement; and such
power springs from its condensation acquired at the place of the per-
cussions, which condensation always penetrates into the falling wind
up to the point at which it becomes separated and its speed of move-
ment becomes less.
The water does the same; not however by condensation but because
it rises in the air and acquires weight. g 69 r.
Why do the northern winds commence to blow at the winter solstice,
and continue until melancholy January?
At the winter solstice, that is at the middle of December, the north-
ern winds are at their maximum strength. g 91 r.
HOW THE WIND THAT STRIKES THE CLOUD ON ONE
SIDE MAKES IT TURN ROUND
If the wind strikes the cloud on one side only, then although its
opposite side, that is of the clouds, is in the motionless air, this cloud
will be driven forward and turned round, and it will make a circular
movement like that of the wheel of a mill turned by the water.
WHAT IS THE CAUSE THAT MAKES THE CLOUDS
INCREASE THEIR HEIGHT?
When the movement of two contrary winds brings two clouds to
strike together these clouds then become incorporated in each other,
and not being able either to expand or lower themselves because of the
wind passing beneath them, these clouds extend in that direction in
which their passage is least impeded, that is upwards.
OF THE MEETING OF TWO CLOUDS MOVING DIFFERENTLY
IN THE SAME PATH
When with the same wind two clouds meet together, the greater in
order to have part of the more powerful wind covers the smaller; and
the two become condensed at their common contact, and this causes
rain. c 91 v.
If the wind is created by excess or dearth the southern parts which
separate the humidity drawn to them come to condense themselves,
and not being able to receive such multiplication they drive it back;
it is then drawn by the vacuum created in the cold region where this
humidity becomes contracted in forming clouds, or in the southern
parts where the other clouds are formed
OF THE SWIFTNESS OF CLOUDS
The course of the cloud is less swift in itself than its shadow which
moves over the earth. This is proved: — Let e be the solar body, a the
cloud, and c its shadow: then as the cloud moves from a to b the
shadow will move from c to d> from which it follows that as the
shadows that pass from the earth to the cloud are made by lines that
converge in the centre of the sun,, we may say by my fourth [rule]
that what is set forth is true, for this fourth says : — the equidistant sec-
tions at the angle of the two converging lines will be so much less as
they are nearer the place of meeting; therefore as the clouds are nearer
the sun than their shadow there can be no doubt that the shadow will
travel a greater distance over the earth than the cloud does through the
air in the same time. g 92 v.
The atmosphere is blue because of the darkness which is above it,
for black and white together make blue. h 77  v.
The part of the cloud which is nearest to the eye will seem swifter
than that which is higher; and for this reason they often appear to be
moving in contrary directions, one to the other. h 89  r.
Of the shapes that one element assumes as it penetrates into another :
Air falling from fire will turn the mill as fire issuing from air will,
and in the same way air falling from water as water from air, and as
earth falling from water; and you should describe the equality of the
powers and resistances and the shapes that they assume as they pass.
1 76  v.
[Compressed air in rose-water at barber's]
Whether air can be compressed in itself is shown by the barber's
vessel for supplying rose-water, in which it is doubled.
Fire is quadrupled by the force of the place where it cannot increase.
1 133  r.
OF THE RISING OF THE WIND
Every movable thing continues its movement in the shortest way
and either shuns the obstacle or is bent by the obstacles; therefore the
i9 2 ATMOSPHERE
wind curves in penetrating the thick air, and bends upwards towards
the light air. k 113  v.
OF WATER AND AIR
Air that moves with impetus within the other air is compressed
within itself as is shown in the expansion of the solar rays; for if the
wind moves their atoms in various revolutions you see these atoms
form themselves into marbled waves after the manner of watered silks
or camlets (gianbellotti) ; and that which you see done to these atoms
is done by the air which bears them shut up within itself.
The water in such cases cannot become compressed, and having all
these like movements in its body it is necessary for it to drive the other
water from its place, so that they may all appear on the surface.
l 78 r.
When the sun strikes upon concave mirrors and leaps back from
them with pyramidal course, that part of the pyramid will be propor-
tionately as much warmer than its base as it is less in size, and it does
so in as much as its moisture becomes restricted. The hot steam which
is mingled with it becomes so much more powerful as it is more united,
and as it is confined within a less space it generates more heat. Conse-
quently it often catches fire and increases, forming itself into a thun-
derbolt out of the cloud; and so it bursts the cloud with devastating
lightning and thunder. The little particles of water, when the cloud
has been contracted by the cold, fasten themselves together and fall by
reason of their weight. And in this way the clouds break up, and so
they return in rain to the low position. b.m. 57 r.
The surfaces of transparent and polished bodies always mirror the
objects which look upon their surfaces and are looked upon by them.
Therefore that which stands underneath the water is mirrored in the
surface of the air which borders upon this water, and that which is in
the air is mirrored in the surface of the water which borders upon
this air. b.m. 196 r.
The course of the winds changes and follows the movement of some
other wind by reason of the mouths of the valleys which it enters and
issues forth from, and this happens more with the low winds than with
the high ones, and this it docs 1mm its being flexible and able to be
bent in any direction except that directly opposite to its course. And
desiring to move and to give place to the new wind it has to do as does
the water that enters a pool by a line and then turns in various chan-
nels, but more by the line that follows that of the movement it makes
at its entrance, and less by that farthest away from this entrance.
The wind is condensed above the places where it strikes, and more
in the summits of the mountains than on the sea coasts visited by it;
for there gather all the reflex winds, that is on summits of the straight
sides of the mountains where these winds strike; for they do not ex-
tend all crosswise following the shape of the summit of the mountain,
but many proceed up in a straight line and especially those that strike
nearest the bases of the mountains, although after they are above the
summit of the mountain they describe a curve, and after such process
of curving straighten themselves into the course of the other wind which
struck them and which first made them describe a curve. b.m. 276 r.
OF THE WIND
Many are the times when the course of one wind is diverted into
that of another, and this arises from the percussion which they make
at the meeting of their courses when as they are not able to penetrate
one into the other necessity constrains them to leap back in opposite
If however the said winds are not of equal power one with another
their reflex movements will not follow the movement of their striker,
but the angle of percussion of the more powerful will be as much
greater than that of the less powerful as is the excess of the greater
power over the lesser.
Winds which blow in the same direction may be simple or mixed
with other winds, that is along one part of its side the wind may be all
taut because the free wind strikes it and leaps back at equal angles,
but never opposite to its source because it would have to re-enter into
itself and the movement of two bodies cannot penetrate within them-
selves. Therefore it follows that the part of the greater wind which is
struck by the lesser wind would turn backwards and follow the course
of the lesser wind which has struck it, but it encounters it along the
remainder of its width and this causes it to curve gradually until finally
it has changed back to its former course.
The same wind therefore in striking produces within itself different
movements and different degrees of power, for the part of its breadth
before mentioned which drives before it the part which flies away also
takes a reflex movement upon the wind which it strikes, and so after
it does the part which when struck puts to flight the second; and the
fourth which strikes the third in such a way that in these parts it
becomes denser. But the first density is greater than the last, after the
manner of two streams of water striking together, as I have demon-
strated in the fourth of the seventh of the elements of mechanics, for
there is an angle formed at the place of the first percussion which
makes the water that first strikes leap up more than any other part of it.
b.m. 276 v.
[Movement of the winds]
If the movement of the winds proceeds from Jupiter the cause of
the wind must be in the twenty-four hours during which the move-
ment of Jupiter is from the east to the west and not from the north
to the south; and this arises from the fact that a thing moved by some-
thing else has the form and time of the movement of its mover.
Quaderni 11 20 v.
QUESTIONS: THE MATERIALS WHICH PRODUCE WIND
If (the wind) is a vapour of the earth and of cold and dryness, and
is carried by heat, it rises to the cold region of the air, and, abandoned
by heat, its conductor, it remains there. Such is the reason why the
vapour, being similar to the vapours in that place, that is to say cold
and dry, leaves the place and vapour, and flies from its similar; and
this, indeed, having ceased its upward movement and entering a place
entirely similar to itself is free to remain without motion. And yet if
you concede it its movement, it must still move in the cold region by
itself. But we shall say that such a vapour being cold and dry in its
slow and late birth, becomes successively mixed with the hot, and so
with a gradual expansion it generates an almost imperceptible motion
in proportion to this expansion. But the motion of the heat which car-
ries it upward is swift and SO conducts it as far as the cold region oi
the air, where, having expelled the first part, the heat which conducts
it there leaves it there, and so diminishes the vapour, which being with-
out wind by the same amount as that of the heat which was mixed
with it, being thus diminished in quantity, grows in weight above the
air which sustains it, and so descends below the other vapour, and hav-
ing descended there the heat which is divided from it is reunited with
the heat and with the other vapour; and this giving it an upward
movement and so raising all the vapour little by little it chills the upper
part which penetrates the cold; and so little by little it falls back
through the weight it has acquired, in such a way that the whole is
composed of a greater weight than it was formerly. Hence it descends
in the form of clouds, and approaching the heat refracted by the earth
warmed by the sun, it becomes dissolved and dilates with great move-
ment; and this is the wind.
The winds descend from above to below at various angles, and,
striking the water or the earth, set up lateral movements along various
lines, as does the water which penetrates other water.
You say that the movement of an effect follows the movement of its
cause; and then say that the twelve signs of the Zodiac are the cause of
the motion of winds, and that the three fiery signs, the Ram, the Lion
and the Archer are of the east and move the eastern winds; and that
the three cold and dry signs, the Bull, the Virgin and the Goat move
the southern winds, and the other three signs move the western winds.
This theory leaves the inventor of such causes in confusion from the
first proposition which you agreed on, viz. that all bodies in motion
follow the movement of their motive force. Now these signs of the
Zodiac are moving from east to west and go round the world in twenty-
four hours. How then do you account for the fact that these signs
which move towards the west will move the western winds; and yet
these winds should move towards the east which would be contrary to
the motion of their motive force? This is contrary to your first assump-
tion, which is true, but your consequent theory is false.
You say that the vapour which generates the wind is carried upwards
by heat and pressed down again by cold; which having been said, it
follows in course that this vapour, finding itself between two contrary
motions, escapes to the sides; and this lateral movement is the wind,
which has a tortuous movement because it cannot descend to the earth
because the heat pushes it up, and it cannot move very high up because
the cold presses it down; hence this necessity gives it a latitudinal and
tortuous movement. Now many drawbacks will follow from this the-
ory of yours, of which the first is that the wind will never descend to
the plain, and secondly that the cold in being driven down by such a
vapour would be acting contrary to its inert nature.
Windsor: Drawings 12671 r.
Then again, it is possible that the vapour which collects in the cold
region, through being abandoned by the heat which conducts it there,
comes to be compressed and makes itself larger (heavier?); and the
air which formerly sustained it no longer resists it, and in consequence
gives place to it; and this vapour being heavy descends rapidly into
the hot region near to the earth. There it is entirely permeated with
heat and in consequence completely dilated and resolved, and moves
in every direction which is round about it, and strikes the sea on its
surface. And here one can see the cause of the origin of such wind as
makes the movement of the sea, for it is flying from the first place it
struck. And in this cause (case?) the courses of the parts of this wind
are not parallel because they move from the centre to the circumference
in direct lines.
The congregation of humidity scattered through the air, which comes
together for the creation of clouds, creates wind in the air. And simi-
larly the breaking up of the clouds makes the fine and penetrable
humidity through the air; and this is the wind. The proof: one may
see the water churned up on a fire which makes a wind in the chimney
that is above this fire; and again, boiling water which is shut into vases
escapes through little vents of such a vase with great force in the man-
ner of wind. And again, fires made in small rooms suck in the air
through little cracks in the windows with great force and noise.
Windsor: Drawings 12671 v.
The force inherent in moving bodies has the result that movement
is often contrary to the nature of the thing moved.
You say that the vapour of the wind is driven up by the heat which
lifts it and is then pushed down again by the cold which joins with
it; and yet necessity gives it a lateral and a curved movement, since
being enclosed between two contrary forces it flies out sideways all
over the earth.
But this theory denies that the vapour which has been mixed in the
cold region of the air is pushed down by this cold, because it is neces-
sary to say either that the vapour flies before the cold from its nature,
or that the cold really removes it of itself, which is being contrary to
the nature of the vapour. And if such a vapour moves of itself, it does
so after it has increased and not before, because at first it is the power
of the heat pressing it down which makes itself greater than the power
of the vapour which wishes to descend. Here it must be confessed that
such a vapour in increasing acquires weight, and that with this weight
it overcomes the force of the heat which sustains it, and that here cold
does not press it down because, if it were natural to such cold to press
it down, it would have been easier to expel it when the vapour was
small in quantity and weak than when it was increased in quantity and
in force. And so here we shall say that the vapour of the wind, having
reached the cold region, stops there, because the heat which has con-
ducted it to this place becomes consumed in cold; and the heat being
consumed the vapour remains without motive force, and so it stays
there and awaits the parts which succeed and adjoin it. And these not
being at such an altitude are not yet completely deprived of heat and
in consequence of movement; and so not being stationary they move
until at last they arrive at the same altitude as the part which has been
chilled and they penetrate this and unite with it, and the heat being
there condensed leaves it [the vapour]. And so subsequently rising,
one part after the other, and penetrating the higher part, they are pre-
vented from condensing, and from that weight of such a nature that
the lower region cannot sustain it above itself. Hence by necessity it
descends united with it until the heat makes it light and again lifts it
upwards, and does the same as it did the first time, and so once more
joining with the cold part it again acquires weight and again sinks
down and again turns to vapour in the upper air. And so this would
go on continually and from this arises the motion of the wind spread-
ing itself from high to low and not from here to there [vertically and
not horizontally]. Well then this theory given above is false, because
experience shows itself in disagreement.
You say that the winds begin by being weak and go on growing in
strength, because in the beginning there was a small quantity of vapour
generated by a small blast; but when such a vapour was increased in
a greater quantity, being struck by the cold, it descends with greater
force and from this arises the growth of wind. To this we answer that
any movement is born of a void or a deficiency. If vapour which is
raised by the heat, which though it penetrates the said heat, dissolves
such a vapour and makes a movement sideways or rather upwards
because that is the true [direction] of the movement of fire, and when,
the more this evaporation rises the more it is pressed in, its exterior
moves itself inwards towards the centre of the bulk. And this second
movement is contrary to the first, because the first moved from the
centre to the extremities and the second movement is from the ex-
tremities to the centre, and from one to the other the movement is more
rapid in proportion as it is more remote from the centre, because the
extremities are more affected by heat and cold than are the parts which
are near the middle. But to return to the matter in hand; the more the
vapour rises the more it is pressed in because it grows nearer to the
cold, the exact opposite of the heat which conducts such a vapour and
presses it in.
This cannot make wind which flows from it, but can make it if it
runs contrary to it because it does not allow a vacuum, and the place
from whence its parts are flying would remain a vacuum if the air did
not fill them up, and this air rushes to fill up [the vacuum] with the
same speed as the vapour when it is rushing away from the cold. And
since the material joined with the motive force which moves it, moves
itself in the same amount of time as the movement made by this motive
force, therefore here the vapour will move itself in such time as the fire,
its first motive force, accompanies it, and when the fire is parted from
it the vapour loses its movement which [movement] the cold does not
give it if it is not against the half of its quantity (?), or it may be that
that part of the vapour which touches the cold first of all is the first to
rush backwards towards the centre, but one cannot classify this as
actual flight but as the loss of its elevation.
You say that the wind does not blow continuously, but with various
gusts divided one from the other; and the cause of this is the vapour
which rises to the cold carried by heat in various quantities. Here one
may answer that the cold does not expel the vapour but (that this is
produced); but that the heat which is escaping from the cold brings
back the vapour which it formerly carried with it to the cold regions.
And again one may say that the heat, in the first contact which it
makes with the cold, warms this cold in proportion as it touches it
[the cold]; and similarly the cold chills the heat in proportion as it
receives it [the heat] into itself. Hence there arises a storm; which has
the result that the heat and cold lose some of their original force; and
in this case the way is prepared for the transformation into vapour
which succeeds, together with the heat, in penetrating more deeply into
the cold and warming it to a greater altitude. And so the vapour pene-
trates farther in such a way that it passes through the cold region and
penetrates towards the element of fire [the source of heat]; and being
united with it the vapour makes a great outburst through all the sur-
rounding regions, which outbursts are rapid movements in direct lines
and result in a flood of air which [strikes] the sea above the horizon
and proves to be the cause of your solution.
Windsor: Drawings 12672
OF THE COLOUR OF THE ATMOSPHERE
I say that the blue which is seen in the atmosphere is not its own
colour, but is caused by the heated moisture having evaporated into
the most minute imperceptible particles, which the beams of the solar
rays attract and cause to seem luminous against the deep intense dark-
ness of the region of fire that forms a covering above them. And this
may be seen, as I myself saw it, by anyone who ascends Mon Boso
(Monte Rosa), a peak of the chain of Alps that divides France from
Italy, at whose base spring the four rivers which flow as many different
ways and water all Europe, and there is no other mountain that has
its base at so great an elevation.
This mountain towers to so great a height as almost to pass above all
the clouds; and snow seldom falls there, but only hail in summer when
me clouds are at their greatest height; and there this hail accumulates,
so that if it were not for the infrequency * of the clouds thus rising and
1 MS. has reta which Dr. Richter reads in sense of 'malanno'. I have adopted Dr.
Solmi's suggestion 'rarita'. (Note, Dec. 1929. Calvi reads [rajreta.)
4 oo ATMOSPHERE
discharging themselves, which does not happen twice in an age, there
would be an enormous mass of ice there, built up by the various layers
of the hail; and this I found very thick in the middle of July. And I
saw the atmosphere dark overhead, and the rays of the sun striking
the mountain had far more brightness than in the plains below, be-
cause less thickness of atmosphere lay between the summit of this
mountain and the sun.
As a further example of the colour of the atmosphere, we may take
the case of the smoke produced by old dry wood, for as it comes out
of the chimneys it seems to be a pronounced blue when seen between
the eye and a dark space, but as it rises higher and comes between the
eye and the luminous atmosphere, it turns immediately to an ashen
grey hue, and this comes to pass because it no longer has darkness
beyond it, but in place of this the luminous atmosphere. But if this
smoke comes from new green wood, then it will not assume a blue
colour, because, as it is not transparent, and is heavily charged with
moisture, it will have the effect of a dense cloud which takes definite
lights and shadows as though it were a solid body.
The same is true of the atmosphere, which excessive moisture renders
white, while little moisture acted upon by heat causes it to be dark
and of a dark blue colour; and this is sufficient as regards the defini-
tion of the colour of the atmosphere, although one may also say that if
the atmosphere had this transparent blue as its natural colour, it would
follow that wherever a greater quantity of atmosphere came between
the eye and the fiery element, it would appear of a deeper shade of
blue, as is seen with blue glass and with sapphires, which appear
darker in proportion as they are thicker. The atmosphere, under these
conditions, acts in exactly the opposite way, since where a greater
quantity of it comes between the eye and the sphere of fire, there it is
seen much whiter, and this happens towards the horizon; and in
proportion as a lesser amount of atmosphere comes between the eye
and the sphere of fire, of so much the deeper blue does it appear, even
when we are in the low plains. It follows therefore, from what I say,
that the atmosphere acquires its blueness from the particles of mois-
ture which catch the luminous rays of the sun.
We may also observe the difference between the atoms of dust and
those of smoke seen in the sun's rays as they pass through the chinks
of the walls in dark rooms, that the one seems the colour of ashes, and
the other — the thin smoke — seems of a most beautiful blue. We may
see also in the dark shadows of mountains far from the eye that the
atmosphere which is between the eye and these shadows will appear
very blue, and in the portion of these mountains which is in light, it
will not vary much from its first colour.
But whoever would see a final proof, should stain a board with
various different colours, among which he should include a very
strong black, and then over them all he should lay a thin transparent
white, and he will then perceive that the lustre of the white will
nowhere display a more beautiful blue than over the black, — but it
must be very thin and finely ground. Leic. 4 r.
Smoke is swift at its beginning and becomes slower at every stage of
its ascent, because it becomes colder and heavier, owing to the fact
that a great part of it is condensed through the parts striking against
each other and being pressed together and made to adhere one to an-
other; and water does the same for it is swift at the beginning of its
movement. Leic. 12 v.
Air even if it changes its position preserves the impression of its
eddies more than water does, from the fact of it being swifter and
thinner. Leic. 30 v.
An excess of smoke acts as a veil, a small quantity of it does not
render the perfection of this blue: it is by a moderate admixture of
smoke therefore that the beautiful blue is created.
Experience it is that shows how the air has darkness behind it and
yet appears blue.
Make smoke of dry wood in a small quantity; let the rays of the
sun fall upon this smoke, and behind it place a piece of black velvet,
so that it shall be in shadow. You will then see that all the smoke
which comes between the eye and the darkness of the velvet will show
itself of a very beautiful blue colour; and if instead of the velvet you
put a white cloth, the smoke will become the colour of ashes.
How water blown in the form of spray into a dark place, through
which the solar rays pass, produces this blue ray; and especially when
this water has been distilled; and how the thin smoke becomes blue.
4 o2 ATMOSPHERE
This is said in order to show how the blue colour of the atmosphere
is caused by the darkness that is above it; and the above-mentioned
instances are offered for the benefit of anyone who cannot confirm
my experience on Mon Boso. 1 Leic. 36 r.
1 See Leic. 4 r. in which Leonardo refers to his ascent of Mon Boso (Monte Rosa)
in the month of July and the atmospheric conditions which he found prevailing.