Let there be first represented the summit of a rugged mountain with
valleys surrounding its base, and on its sides let the surface of
the soil be seen to slide, together with the small roots of the
bushes, denuding great portions of the surrounding rocks. And
descending ruinous from these precipices in its boisterous course,
let it dash along and lay bare the twisted and gnarled roots of
large trees overthrowing their roots upwards; and let the mountains,
as they are scoured bare, discover the profound fissures made in
them by ancient earthquakes. The base of the mountains may be in
great part clothed and covered with ruins of shrubs, hurled down
from the sides of their lofty peaks, which will be mixed with mud,
roots, boughs of trees, with all sorts of leaves thrust in with the
mud and earth and stones. And into the depth of some valley may have
fallen the fragments of a mountain forming a shore to the swollen
waters of its river; which, having already burst its banks, will
rush on in monstrous waves; and the greatest will strike upon and
destroy the walls of the cities and farmhouses in the valley [14].
Then the ruins of the high buildings in these cities will throw up a
great dust, rising up in shape like smoke or wreathed clouds against
the falling rain; But the swollen waters will sweep round the pool
which contains them striking in eddying whirlpools against the
different obstacles, and leaping into the air in muddy foam; then,
falling back, the beaten water will again be dashed into the air.
And the whirling waves which fly from the place of concussion, and
whose impetus moves them across other eddies going in a contrary
direction, after their recoil will be tossed up into the air but
without dashing off from the surface. Where the water issues from
the pool the spent waves will be seen spreading out towards the
outlet; and there falling or pouring through the air and gaining
weight and impetus they will strike on the water below piercing it
and rushing furiously to reach its depth; from which being thrown
back it returns to the surface of the lake, carrying up the air that
was submerged with it; and this remains at the outlet in foam
mingled with logs of wood and other matters lighter than water.
Round these again are formed the beginnings of waves which increase
the more in circumference as they acquire more movement; and this
movement rises less high in proportion as they acquire a broader
base and thus they are less conspicuous as they die away. But if
these waves rebound from various objects they then return in direct
opposition to the others following them, observing the same law of
increase in their curve as they have already acquired in the
movement they started with. The rain, as it falls from the clouds is
of the same colour as those clouds, that is in its shaded side;
unless indeed the sun's rays should break through them; in that case
the rain will appear less dark than the clouds. And if the heavy
masses of ruin of large mountains or of other grand buildings fall
into the vast pools of water, a great quantity will be flung into
the air and its movement will be in a contrary direction to that of
the object which struck the water; that is to say: The angle of
reflection will be equal to the angle of incidence. Of the objects
carried down by the current, those which are heaviest or rather
largest in mass will keep farthest from the two opposite shores. The
water in the eddies revolves more swiftly in proportion as it is
nearer to their centre. The crests of the waves of the sea tumble to
their bases falling with friction on the bubbles of their sides; and
this friction grinds the falling water into minute particles and
this being converted into a dense mist, mingles with the gale in the
manner of curling smoke and wreathing clouds, and at last it, rises
into the air and is converted into clouds. But the rain which falls
through the atmosphere being driven and tossed by the winds becomes
rarer or denser according to the rarity or density of the winds that
buffet it, and thus there is generated in the atmosphere a moisture
formed of the transparent particles of the rain which is near to the
eye of the spectator. The waves of the sea which break on the slope
of the mountains which bound it, will foam from the velocity with
which they fall against these hills; in rushing back they will meet
the next wave as it comes and and after a loud noise return in a
great flood to the sea whence they came. Let great numbers of
inhabitants--men and animals of all kinds--be seen driven [54] by
the rising of the deluge to the peaks of the mountains in the midst
of the waters aforesaid.
The wave of the sea at Piombino is all foaming water. [Footnote 55.
56: These two lines are written below the bottom sketch on Pl. XXXV,
3. The MS. Leic. being written about the year 1510 or later, it does
not seem to me to follow that the sketches must have been made at
Piombino, where Leonardo was in the year 1502 and possibly returned
there subsequently (see Vol. II. Topographical notes).]
Of the water which leaps up from the spot where great masses fall on
its surface. Of the winds of Piombino at Piombino. Eddies of wind
and rain with boughs and shrubs mixed in the air. Emptying the boats
of the rain water.
[Footnote: The sketches on Pl. XXXV 3 stand by the side of lines 14
to 54.]
Of depicting natural phenomena (610. 611).
610.
The tremendous fury of the wind driven by the falling in of the
hills on the caves within--by the falling of the hills which served
as roofs to these caverns.
A stone flung through the air leaves on the eye which sees it the
impression of its motion, and the same effect is produced by the
drops of water which fall from the clouds when it [16] rains.
[17] A mountain falling on a town, will fling up dust in the form of
clouds; but the colour of this dust will differ from that of the
clouds. Where the rain is thickest let the colour of the dust be
less conspicuous and where the dust is thickest let the rain be less
conspicuous. And where the rain is mingled with the wind and with
the dust the clouds created by the rain must be more transparent
than those of dust [alone]. And when flames of fire are mingled with
clouds of smoke and water very opaque and dark clouds will be formed
[Footnote 26-28: Compare Pl. XL, 1--the drawing in Indian ink on the
left hand side, which seems to be a reminiscence of his observations
of an eruption (see his remarks on Mount Etna in Vol II).]. And the
rest of this subject will be treated in detail in the book on
painting.
[Footnote: See the sketches and text on Pl. XXXVIII, No. 1. Lines
1-16 are there given on the left hand side, 17-30 on the right. The
four lines at the bottom on the right are given as No. 472. Above
these texts, which are written backwards, there are in the original
sixteen lines in a larger writing from left to right, but only half
of this is here visible. They treat of the physical laws of motion
of air and water. It does not seem to me that there is any reason
for concluding that this writing from left to right is spurious.
Compare with it the facsimile of the rough copy of Leonardo's letter
to Ludovico il Moro in Vol. II.]
611.
People were to be seen eagerly embarking victuals on various kinds
of hastily made barks. But little of the waves were visible in those
places where the dark clouds and rain were reflected.
But where the flashes caused by the bolts of heaven were reflected,
there were seen as many bright spots, caused by the image of the
flashes, as there were waves to reflect them to the eye of the
spectator.
The number of the images produced by the flash of lightning on the
waves of the water were multiplied in proportion to the distance of
the spectator's eye.
So also the number of the images was diminished in proportion as
they were nearer the eye which saw them [Footnote 22. 23: _Com'e
provato_. See Vol. II, Nos. 874-878 and 892-901], as it has been
proved in the definition of the luminosity of the moon, and of our
marine horizon when the sun's rays are reflected in it and the eye
which receives the reflection is remote from the sea.