The Notebooks of Leonardo Da Vinci — Complete
on the margin on the bank of the river above 1. I; in the
reproduction it is not visible. As may be seen from the last
sentence, the observation was made after long study of the river's
course, when Leonardo had resided for some time at, or near,
Amboise.]
1075.
The water may be dammed up above the level of Romorantin to such a
height, that in its fall it may be used for numerous mills.
1075.
The river at Villefranche may be conducted to Romorantin which may
be done by the inhabitants; and the timber of which their houses are
built may be carried in boats to Romorantin [Footnote: Compare No.
744.]. The river may be dammed up at such a height that the waters
may be brought back to Romorantin with a convenient fall.
1076.
As to whether it is better that the water should all be raised in a
single turn or in two?
The answer is that in one single turn the wheel could not support
all the water that it can raise in two turns, because at the half
turn of the wheel it would be raising 100 pounds and no more; and if
it had to raise the whole, 200 pounds in one turn, it could not
raise them unless the wheel were of double the diameter and if the
diameter were doubled, the time of its revolution would be doubled;
therefore it is better and a greater advantage in expense to make
such a wheel of half the size (?) the land which it would water and
would render the country fertile to supply food to the inhabitants,
and would make navigable canals for mercantile purposes.
The way in which the river in its flow should scour its own channel.
By the ninth of the third; the more rapid it is, the more it wears
away its channel; and, by the converse proposition, the slower the
water the more it deposits that which renders it turbid.
And let the sluice be movable like the one I arranged in Friuli
[Footnote 19: This passage reveals to us the fact that Leonardo had
visited the country of Friuli and that he had stayed there for some
time. Nothing whatever was known of this previously.], where when
one sluice was opened the water which passed through it dug out the
bottom. Therefore when the rivers are flooded, the sluices of the
mills ought to be opened in order that the whole course of the river
may pass through falls to each mill; there should be many in order
to give a greater impetus, and so all the river will be scoured. And
below the site of each of the two mills there may be one of the said
sluice falls; one of them may be placed below each mill.
1078.
A trabocco is four braccia, and one mile is three thousand of the
said braccia. Each braccio is divided into 12 inches; and the water
in the canals has a fall in every hundred trabocchi of two of these
inches; therefore 14 inches of fall are necessary in two thousand
eight hundred braccia of flow in these canals; it follows that 15
inches of fall give the required momentum to the currents of the
waters in the said canals, that is one braccio and a half in the
mile. And from this it may be concluded that the water taken from
the river of Ville-franche and lent to the river of Romorantin
will..... Where one river by reason of its low level cannot flow
into the other, it will be necessary to dam it up, so that it may
acquire a fall into the other, which was previously the higher.
The eve of Saint Antony I returned from Romorantin to Amboise, and
the King went away two days before from Romorantin.
>From Romorantin as far as the bridge at Saudre it is called the
Saudre, and from that bridge as far as Tours it is called the Cher.
I would test the level of that channel which is to lead from the
Loire to Romorantin, with a channel one braccio wide and one braccio
deep.
[Footnote: Lines 6-18 are partly reproduced in the facsimile on p.
254, and the whole of lines 19-25.
The following names are written along the rivers on the larger
sketch, _era f_ (the Loire) _scier f_ (the Cher) three times. _Pote
Sodro_ (bridge of the Soudre). _Villa francha_ (Villefranche)
_banco_ (sandbank) _Sodro_ (Soudre). The circle below shows the
position of Romorantin. The words '_orologio del sole_' written
below do not belong to the map of the rivers. The following names
are written by the side of the smaller sketch-map:--_tors_ (Tours),
_Abosa_ (Amboise) _bres_--for Bles (Blois) _mo rica_ (Montrichard).
_Lione_ (Lyons). This map was also published in the 'Saggio'
(Milano, 1872) Pl. XXII, and the editors remark: _Forse la linia
retta che va da Amboise a Romorantin segna l'andamento proposto d'un
Canale, che poi rembra prolungarsi in giu fin dove sta scritto
Lione._
M. Ravaisson has enlarged on this idea in the Gazette des Beaux Arts
(1881 p. 530): _Les traces de Leonard permettent d'entrevoir que le
canal commencant soit aupres de Tours, soit aupres de Blois et
passant par Romorantin, avec port d'embarquement a Villefranche,
devait, au dela de Bourges, traverser l'Allier au-dessous des
affluents de la Dore et de la Sioule, aller par Moulins jusqu' a
Digoin; enfin, sur l'autre rive de la Loire, depasser les monts du
Charolais et rejoindre la Saone aupres de Macon._ It seems to me
rash, however, to found so elaborate an hypothesis on these sketches
of rivers. The slight stroke going to _Lione_ is perhaps only an
indication of the direction.--With regard to the Loire compare also
No. 988. l. 38.]
1079.
THE ROAD TO ORLEANS
At 1/4 from the South to the South East. At 1/3 from the South to
the South East. At 1/4 from the South to the South East. At 1/5 from
the South to the South East. Between the South West and South, to
the East bearing to the South; from the South towards the East 1/8;
thence to the West, between the South and South West; at the South.
[Footnote: The meaning is obscure; a more important passage
referring to France is to be found under No. 744]
On the Germans (1080. 1081).
1080.
The way in which the Germans closing up together cross and
interweave their broad leather shields against the enemy, stooping
down and putting one of the ends on the ground while they hold the
rest in their hand. [Footnote: Above the text is a sketch of a few
lines crossing each other and the words _de ponderibus_. The meaning
of the passage is obscure.]
1081.
The Germans are wont to annoy a garrison with the smoke of feathers,
sulphur and realgar, and they make this smoke last 7 or 8 hours.
Likewise the husks of wheat make a great and lasting smoke; and also
dry dung; but this must be mixed with olive husks, that is olives
pressed for oil and from which the oil has been extracted.
[Footnote: There is with this passage a sketch of a round tower
shrouded in smoke.]
The Danube.
1082.
That the valleys were formerly in great part covered by lakes the
soil of which always forms the banks of rivers,--and by seas, which
afterwards, by the persistent wearing of the rivers, cut through the
mountains and the wandering courses of the rivers carried away the
other plains enclosed by the mountains; and the cutting away of the
mountains is evident from the strata in the rocks, which correspond
in their sections as made by the courses of the rivers [Footnote 4:
_Emus_, the Balkan; _Dardania_, now Servia.], The Haemus mountains
which go along Thrace and Dardania and join the Sardonius mountains
which, going on to the westward change their name from Sardus to
Rebi, as they come near Dalmatia; then turning to the West cross
Illyria, now called Sclavonia, changing the name of Rebi to Albanus,
and going on still to the West, they change to Mount Ocra in the
North; and to the South above Istria they are named Caruancas; and
to the West above Italy they join the Adula, where the Danube rises
[8], which stretches to the East and has a course of 1500 miles; its
shortest line is about l000 miles, and the same or about the same is
that branch of the Adula mountains changed as to their name, as
before mentioned. To the North are the Carpathians, closing in the
breadth of the valley of the Danube, which, as I have said extends
eastward, a length of about 1000 miles, and is sometimes 200 and in
some places 300 miles wide; and in the midst flows the Danube, the
principal river of Europe as to size. The said Danube runs through
the middle of Austria and Albania and northwards through Bavaria,
Poland, Hungary, Wallachia and Bosnia and then the Danube or Donau
flows into the Black Sea, which formerly extended almost to Austria
and occupied the plains through which the Danube now courses; and
the evidence of this is in the oysters and cockle shells and
scollops and bones of great fishes which are still to be found in
many places on the sides of those mountains; and this sea was formed
by the filling up of the spurs of the Adula mountains which then
extended to the East joining the spurs of the Taurus which extend to
the West. And near Bithynia the waters of this Black Sea poured into
the Propontis [Marmora] falling into the Aegean Sea, that is the
Mediterranean, where, after a long course, the spurs of the Adula
mountains became separated from those of the Taurus. The Black Sea
sank lower and laid bare the valley of the Danube with the above
named countries, and the whole of Asia Minor beyond the Taurus range
to the North, and the plains from mount Caucasus to the Black Sea to
the West, and the plains of the Don this side--that is to say, at
the foot of the Ural mountains. And thus the Black Sea must have
sunk about 1000 braccia to uncover such vast plains.
[Footnote 8: _Danubio_, in the original _Reno_; evidently a mistake
as we may infer from _come dissi_ l. 10 &c.]
III.
THE COUNTRIES OF THE WESTERN END OF THE MEDITERRANEAN.
The straits of Gibraltar (1083-1085).
1083.
WHY THE SEA MAKES A STRONGER CURRENT IN THE STRAITS OF SPAIN THAN
ELSEWHERE.
A river of equal depth runs with greater speed in a narrow space
than in a wide one, in proportion to the difference between the
wider and the narrower one.
This proposition is clearly proved by reason confirmed by
experiment. Supposing that through a channel one mile wide there
flows one mile in length of water; where the river is five miles
wide each of the 5 square miles will require 1/5 of itself to be
equal to the square mile of water required in the sea, and where the
river is 3 miles wide each of these square miles will require the
third of its volume to make up the amount of the square mile of the
narrow part; as is demonstrated in _f g h_ at the mile marked _n_.
[Footnote: In the place marked A in the diagram _Mare Mediterano_
(Mediterranean Sea) is written in the original. And at B, _stretto
di Spugna_ (straits of Spain, _i.e._ Gibraltar). Compare No. 960.]
1084.
WHY THE CURRENT OF GIBRALTAR IS ALWAYS GREATER TO THE WEST THAN TO
THE EAST.
The reason is that if you put together the mouths of the rivers
which discharge into the Mediterranean sea, you would find the sum
of water to be larger than that which this sea pours through the
straits into the ocean. You see Africa discharging its rivers that
run northwards into this sea, and among them the Nile which runs
through 3000 miles of Africa; there is also the Bagrada river and
the Schelif and others. [Footnote 5: _Bagrada_ (Leonardo writes
Bragada) in Tunis, now Medscherda; _Mavretano_, now Schelif.]
Likewise Europe pours into it the Don and the Danube, the Po, the
Rhone, the Arno, and the Tiber, so that evidently these rivers, with
an infinite number of others of less fame, make its great breadth
and depth and current; and the sea is not wider than 18 miles at the
most westerly point of land where it divides Europe from Africa.
1085.
The gulf of the Mediterranean, as an inland sea, received the
principal waters of Africa, Asia and Europe that flowed towards it;
and its waters came up to the foot of the mountains that surrounded