Notebooks of Leonardo da Vinci

_The only notes on musical matters are those given as Nos._ 1129
_and_ 1130, _which explain certain arrangements in instruments._ 

The ship's logs of Vitruvius, of Alberti and of Leonardo 

1113. 

ON MOVEMENTS;--TO KNOW HOW MUCH A SHIP ADVANCES IN AN HOUR. 

The ancients used various devices to ascertain the distance gone by
a ship each hour, among which Vitruvius [Footnote 6: See VITRUVIUS,
_De Architectura lib. X._ C. 14 (p. 264 in the edition of Rose and
Muller- Strubing). The German edition published at Bale in 1543 has,
on fol. 596, an illustration of the contrivance, as described by
Vitruvius.] gives one in his work on Architecture which is just as
fallacious as all the others; and this is a mill wheel which touches
the waves of the sea at one end and in each complete revolution
describes a straight line which represents the circumference of the
wheel extended to a straightness. But this invention is of no worth
excepting on the smooth and motionless surface of lakes. But if the
water moves together with the ship at an equal rate, then the wheel
remains motionless; and if the motion of the water is more or less
rapid than that of the ship, then neither has the wheel the same
motion as the ship so that this invention is of but little use.
There is another method tried by experiment with a known distance
between one island and another; and this is done by a board or under
the pressure of wind which strikes on it with more or less
swiftness. This is in Battista Alberti [Footnote 25: LEON BATTISTA
ALBERTI, _De Architectura lib. V._, c. 12 treats '_de le navi e
parti loro_', but there is no reference to the machine, mentioned by
Leonardo. Alberti says here: _Noi abbiamo trattato lungamente in
altro luogo de' modi de le navi, ma in questo luogo ne abbiamo detto
quel tanto che si bisogna_. To this the following note is added in
the most recent Italian edition: _Questo libro e tuttora inedito e
porta il titolo, secondo Gesnero di_ '_Liber navis_'.]. 

Battista Alberti's method which is made by experiment on a known
distance between one island and another. But such an invention does
not succeed excepting on a ship like the one on which the experiment
was made, and it must be of the same burden and have the same sails,
and the sails in the same places, and the size of the waves must be
the same. But my method will serve for any ship, whether with oars
or sails; and whether it be small or large, broad or long, or high
or low, it always serves [Footnote 52: Leonardo does not reveal the
method invented by him.]. 

Methods of staying and moving in water 

1114. 

How an army ought to cross rivers by swimming with air-bags ... How
fishes swim [Footnote 2: Compare No. 821.]; of the way in which they
jump out of the water, as may be seen with dolphins; and it seems a
wonderful thing to make a leap from a thing which does not resist
but slips away. Of the swimming of animals of a long form, such as
eels and the like. Of the mode of swimming against currents and in
the rapid falls of rivers. Of the mode of swimming of fishes of a
round form. How it is that animals which have not long hind quartres
cannot swim. How it is that all other animals which have feet with
toes, know by nature how to swim, excepting man. In what way man
ought to learn to swim. Of the way in which man may rest on the
water. How man may protect himself against whirlpools or eddies in
the water, which drag him down. How a man dragged to the bottom must
seek the reflux which will throw him up from the depths. How he
ought to move his arms. How to swim on his back. How he can and how
he cannot stay under water unless he can hold his breath [13]. How
by means of a certain machine many people may stay some time under
water. How and why I do not describe my method of remaining under
water, or how long I can stay without eating; and I do not publish
nor divulge these by reason of the evil nature of men who would use
them as means of destruction at the bottom of the sea, by sending
ships to the bottom, and sinking them together with the men in them.
And although I will impart others, there is no danger in them;
because the mouth of the tube, by which you breathe, is above the
water supported on bags or corks [19]. 

[Footnote: L. 13-19 will also be found in Vol. I No. 1.] 

On naval warfare (1115. 1116). 

1115. 

Supposing in a battle between ships and galleys that the ships are
victorious by reason of the high of heir tops, you must haul the
yard up almost to the top of the mast, and at the extremity of the
yard, that is the end which is turned towards the enemy, have a
small cage fastened, wrapped up below and all round in a great
mattress full of cotton so that it may not be injured by the bombs;
then, with the capstan, haul down the opposite end of this yard and
the top on the opposite side will go up so high, that it will be far
above the round-top of the ship, and you will easily drive out the
men that are in it. But it is necessary that the men who are in the
galley should go to the opposite side of it so as to afford a
counterpoise to the weight of the men placed inside the cage on the
yard. 

1116. 

If you want to build an armada for the sea employ these ships to ram
in the enemy's ships. That is, make ships 100 feet long and 8 feet