Notebooks of Leonardo da Vinci

WHICH FORMS ITS SHORE. 

_b d_ is a plain through which a river flows to the sea; this plain
ends at the sea, and since in fact the dry land that is uncovered is
not perfectly level--for, if it were, the river would have no
motion--as the river does move, this place is a slope rather than a
plain; hence this plain _d b_ so ends where the sphere of water
begins that if it were extended in a continuous line to _b a_ it
would go down beneath the sea, whence it follows that the sea _a c
b_ looks higher than the dry land. 

Obviously no portions of dry land left uncovered by water can ever
be lower than the surface of the watery sphere. 

943. 

OF CERTAIN PERSONS WHO SAY THE WATERS WERE HIGHER THAN THE DRY LAND.

Certainly I wonder not a little at the common opinion which is
contrary to truth, but held by the universal consent of the judgment
of men. And this is that all are agreed that the surface of the sea
is higher than the highest peaks of the mountains; and they allege
many vain and childish reasons, against which I will allege only one
simple and short reason; We see plainly that if we could remove the
shores of the sea, it would invest the whole earth and make it a
perfect sphere. Now, consider how much earth would be carried away
to enable the waves of the sea to cover the world; therefore that
which would be carried away must be higher than the sea-shore. 

944. 

THE OPINION OF SOME PERSONS WHO SAY THAT THE WATER OF SOME SEAS IS
HIGHER THAN THE HIGHEST SUMMITS OF MOUNTAINS; AND NEVERTHELESS THE
WATER WAS FORCED UP TO THESE SUMMITS. 

Water would not move from place to place if it were not that it
seeks the lowest level and by a natural consequence it never can
return to a height like that of the place where it first on issuing
from the mountain came to light. And that portion of the sea which,
in your vain imagining, you say was so high that it flowed over the
summits of the high mountains, for so many centuries would be
swallowed up and poured out again through the issue from these
mountains. You can well imagine that all the time that Tigris and
Euphrates 

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.] 

II. 

ON THE OCEAN. 

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

946. 

WHY WATER IS SALT. 

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