Order of the book: describing water jets by the four winds
A plan to classify spouting water by force, quantity and obliquity; two equal jets collide
Under the heading 'Order of the book', Leonardo sets out his method: to describe the aspects of waters that 'germinate' (spurt up) into the air, with their impacts, forces, quantities, lengths of motion and varieties of obliquity, he will use the four principal winds, north, south, east and west, as a framework, making the account briefer and more expeditious. He then begins the cases: two jets of equal thickness but unequal height springing eastward will cross as they descend, the more powerful cutting the other. A further note, beside a small angle figure, opens the case of a declining obliquity meeting a rising one at an angle; both this and the collision note break off.
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A plan to describe water jets by analogy to the four winds
To describe the aspects of waters that spring into the air, their impacts, forces, quantities, lengths of motion and obliquities, Leonardo will use the four principal winds, north, south, east and west, as a similitude. This will make the description briefer and more expeditious.
Two jets of equal thickness and unequal height colliding eastward
If two waters of equal thickness but unequal height spring into the air along the straight line of the east, one in descending will cut the other, and it will be the more powerful. A further case of equal jets colliding is begun but breaks off.
Figure of an angle: declining meets rising obliquity
Beside a small angle figure Leonardo opens the case of a declining obliquity meeting a rising obliquity at an angle. The note breaks off before the result is stated.