The Notebooks of Leonardo Da Vinci (66 page)

945.

have flowed from the summits of the mountains of Armenia, it must be
believed that all the water of the ocean has passed very many times
through these mouths. And do you not believe that the Nile must have
sent more water into the sea than at present exists of all the
element of water? Undoubtedly, yes. And if all this water had fallen
away from this body of the earth, this terrestrial machine would
long since have been without water. Whence we may conclude that the
water goes from the rivers to the sea, and from the sea to the
rivers, thus constantly circulating and returning, and that all the
sea and the rivers have passed through the mouth of the Nile an
infinite number of times [Footnote:
Moti Armeni, Ermini
in the
original, in M. RAVAISSON'S transcript
"monti ernini [le loro
ruine?]"
. He renders this _"Le Tigre et l'Euphrate se sont deverses
par les sommets des montagnes [avec leurs eaux destructives?] on
pent cro're" &c. Leonardo always writes
Ermini, Erminia
, for
Armeni, Armenia
(Arabic:
Irminiah
). M. RAVAISSON also deviates
from the original in his translation of the following passage: "
Or
tu ne crois pas que le Nil ait mis plus d'eau dans la mer qu'il n'y
en a a present dans tout l'element de l'eau. Il est certain que si
cette eau etait tombee
" &c.]

Refutation of Pliny's theory as to the saltness of the sea (946.
947).

946.

Pliny says in his second book, chapter 103, that the water of the
sea is salt because the heat of the sun dries up the moisture and
drinks it up; and this gives to the wide stretching sea the savour
of salt. But this cannot be admitted, because if the saltness of the
sea were caused by the heat of the sun, there can be no doubt that
lakes, pools and marshes would be so much the more salt, as their
waters have less motion and are of less depth; but experience shows
us, on the contrary, that these lakes have their waters quite free
from salt. Again it is stated by Pliny in the same chapter that this
saltness might originate, because all the sweet and subtle portions
which the heat attracts easily being taken away, the more bitter and
coarser part will remain, and thus the water on the surface is
fresher than at the bottom [Footnote 22: Compare No. 948.]; but this
is contradicted by the same reason given above, which is, that the
same thing would happen in marshes and other waters, which are dried
up by the heat. Again, it has been said that the saltness of the sea
is the sweat of the earth; to this it may be answered that all the
springs of water which penetrate through the earth, would then be
salt. But the conclusion is, that the saltness of the sea must
proceed from the many springs of water which, as they penetrate into
the earth, find mines of salt and these they dissolve in part, and
carry with them to the ocean and the other seas, whence the clouds,
the begetters of rivers, never carry it up. And the sea would be
salter in our times than ever it was at any time; and if the
adversary were to say that in infinite time the sea would dry up or
congeal into salt, to this I answer that this salt is restored to
the earth by the setting free of that part of the earth which rises
out of the sea with the salt it has acquired, and the rivers return
it to the earth under the sea.

[Footnote: See PLINY, Hist. Nat. II, CIII [C].
Itaque Solis ardore
siccatur liquor: et hoc esse masculum sidus accepimus, torrens
cuncta sorbensque.
(cp. CIV.)
Sic mari late patenti saporem
incoqui salis, aut quia exhausto inde dulci tenuique, quod facillime
trahat vis ignea, omne asperius crassiusque linquatur: ideo summa
aequorum aqua dulciorem profundam; hanc esse veriorem causam, quam
quod mare terrae sudor sit aeternus: aut quia plurimum ex arido
misceatur illi vapore: aut quia terrae natura sicut medicatas aquas
inficiat
… (cp. CV):
altissimum mare XV. stadiorum Fabianus
tradit. Alii n Ponto coadverso Coraxorum gentis (vocant B Ponti)
trecentis fere a continenti stadiis immensam altitudinem maris
tradunt, vadis nunquam repertis.
(cp. CVI [CIII])
Mirabilius id
faciunt aquae dulces, juxta mare, ut fistulis emicantes. Nam nec
aquarum natura a miraculis cessat. Dulces mari invehuntur, leviores
haud dubie. Ideo et marinae, quarum natura gravior, magis invecta
sustinent. Quaedam vero et dulces inter se supermeant alias.
]

947.

For the third and last reason we will say that salt is in all
created things; and this we learn from water passed over the ashes
and cinders of burnt things; and the urine of every animal, and the
superfluities issuing from their bodies, and the earth into which
all things are converted by corruption.

But,—to put it better,—given that the world is everlasting, it
must be admitted that its population will also be eternal; hence the
human species has eternally been and would be consumers of salt; and
if all the mass of the earth were to be turned into salt, it would
not suffice for all human food [Footnote 27: That is, on the
supposition that salt, once consumed, disappears for ever.]; whence
we are forced to admit, either that the species of salt must be
everlasting like the world, or that it dies and is born again like
the men who devour it. But as experience teaches us that it does not
die, as is evident by fire, which does not consume it, and by water
which becomes salt in proportion to the quantity dissolved in
it,—and when it is evaporated the salt always remains in the
original quantity—it must pass through the bodies of men either in
the urine or the sweat or other excretions where it is found again;
and as much salt is thus got rid of as is carried every year into
towns; therefore salt is dug in places where there is urine.— Sea
hogs and sea winds are salt.

We will say that the rains which penetrate the earth are what is
under the foundations of cities with their inhabitants, and are what
restore through the internal passages of the earth the saltness
taken from the sea; and that the change in the place of the sea,
which has been over all the mountains, caused it to be left there in
the mines found in those mountains, &c.

The characteristics of sea water (948. 949).

948.

The waters of the salt sea are fresh at the greatest depths.

949.

The ocean does not penetrate under the earth, and this we learn from
the many and various springs of fresh water which, in many parts of
the ocean make their way up from the bottom to the surface. The same
thing is farther proved by wells dug beyond the distance of a mile
from the said ocean, which fill with fresh water; and this happens
because the fresh water is lighter than salt water and consequently
more penetrating.

Which weighs most, water when frozen or when not frozen?

That fresh water penetrates more against salt water, than salt water
against fresh is proved by a thin cloth dry and old, hanging with
the two opposite ends equally low in the two different waters, the
surfaces of which are at an equal level; and it will then be seen
how much higher the fresh water will rise in this piece of linen
than the salt; by so much is the fresh lighter than the salt.

On the formation of Gulfs (950. 951).

950.

All inland seas and the gulfs of those seas, are made by rivers
which flow into the sea.

951.

HERE THE REASON IS GIVEN OF THE EFFECTS PRODUCED BY THE WATERS IN
THE ABOVE MENTIONED PLACE.

All the lakes and all the gulfs of the sea and all inland seas are
due to rivers which distribute their waters into them, and from
impediments in their downfall into the Mediterranean —which divides
Africa from Europe and Europe from Asia by means of the Nile and the
Don which pour their waters into it. It is asked what impediment is
great enough to stop the course of the waters which do not reach the
ocean.

On the encroachments of the sea on the land and vice versa
(952-954).

952.

A wave of the sea always breaks in front of its base, and that
portion of the crest will then be lowest which before was highest.

[Footnote: The page of FRANCESCO DI GIORGIO'S
Trattato
, on which
Leonardo has written this remark, contains some notes on the
construction of dams, harbours &c.]

953.

That the shores of the sea constantly acquire more soil towards the
middle of the sea; that the rocks and promontories of the sea are
constantly being ruined and worn away; that the Mediterranean seas
will in time discover their bottom to the air, and all that will be
left will be the channel of the greatest river that enters it; and
this will run to the ocean and pour its waters into that with those
of all the rivers that are its tributaries.

954.

How the river Po, in a short time might dry up the Adriatic sea in
the same way as it has dried up a large part of Lombardy.

The ebb and flow of the tide (955-960).

955.

Where there is a larger quantity of water, there is a greater flow
and ebb, but the contrary in narrow waters.

Look whether the sea is at its greatest flow when the moon is half
way over our hemisphere [on the meridian].

956.

Whether the flow and ebb are caused by the moon or the sun, or are
the breathing of this terrestrial machine. That the flow and ebb are
different in different countries and seas.

[Footnote: 1. Allusion may here be made to the mythological
explanation of the ebb and flow given in the Edda. Utgardloki says
to Thor (Gylfaginning 48): "When thou wert drinking out of the horn,
and it seemed to thee that it was slow in emptying a wonder befell,
which I should not have believed possible: the other end of the horn
lay in the sea, which thou sawest not; but when thou shalt go to the
sea, thou shalt see how much thou hast drunk out of it. And that men
now call the ebb tide."

Several passages in various manuscripts treat of the ebb and flow.
In collecting them I have been guided by the rule only to transcribe
those which named some particular spot.]

957.

958.

All seas have their flow and ebb in the same period, but they seem
to vary because the days do not begin at the same time throughout
the universe; in such wise as that when it is midday in our
hemisphere, it is midnight in the opposite hemisphere; and at the
Eastern boundary of the two hemispheres the night begins which
follows on the day, and at the Western boundary of these hemispheres
begins the day, which follows the night from the opposite side.
Hence it is to be inferred that the above mentioned swelling and
diminution in the height of the seas, although they take place in
one and the same space of time, are seen to vary from the above
mentioned causes. The waters are then withdrawn into the fissures
which start from the depths of the sea and which ramify inside the
body of the earth, corresponding to the sources of rivers, which are
constantly taking from the bottom of the sea the water which has
flowed into it. A sea of water is incessantly being drawn off from
the surface of the sea. And if you should think that the moon,
rising at the Eastern end of the Mediterranean sea must there begin
to attract to herself the waters of the sea, it would follow that we
must at once see the effect of it at the Eastern end of that sea.
Again, as the Mediterranean sea is about the eighth part of the
circumference of the aqueous sphere, being 3000 miles long, while
the flow and ebb only occur 4 times in 24 hours, these results would
not agree with the time of 24 hours, unless this Mediterranean sea
were six thousand miles in length; because if such a superabundance
of water had to pass through the straits of Gibraltar in running
behind the moon, the rush of the water through that strait would be
so great, and would rise to such a height, that beyond the straits
it would for many miles rush so violently into the ocean as to cause
floods and tremendous seething, so that it would be impossible to
pass through. This agitated ocean would afterwards return the waters
it had received with equal fury to the place they had come from, so
that no one ever could pass through those straits. Now experience
shows that at every hour they are passed in safety, but when the
wind sets in the same direction as the current, the strong ebb
increases [Footnote 23: In attempting to get out of the
Mediterranean, vessels are sometimes detained for a considerable
time; not merely by the causes mentioned by Leonardo but by the
constant current flowing eastwards through the middle of the straits
of Gibraltar.]. The sea does not raise the water that has issued
from the straits, but it checks them and this retards the tide; then
it makes up with furious haste for the time it has lost until the
end of the ebb movement.

959.

That the flow and ebb are not general; for on the shore at Genoa
there is none, at Venice two braccia, between England and Flanders
18 braccia. That in the straits of Sicily the current is very strong
because all the waters from the rivers that flow into the Adriatic
pass there.

[Footnote: A few more recent data may be given here to facilitate
comparison. In the Adriatic the tide rises 2 and 1/2 feet, at
Terracina 1 1/4. In the English channel between Calais and Kent it
rises from 18 to 20 feet. In the straits of Messina it rises no more
than 2 1/2 feet, and that only in stormy weather, but the current is
all the stronger. When Leonardo accounts for this by the southward
flow of all the Italian rivers along the coasts, the explanation is
at least based on a correct observation; namely that a steady
current flows southwards along the coast of Calabria and another
northwards, along the shores of Sicily; he seems to infer, from the
direction of the fust, that the tide in the Adriatic is caused by
it.]