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Paris Manuscript F — 91

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Bibliothèque de l'Institut de France, Paris

De l'acqua che cade delle chiuse de' fiumi, a quelle parte sarà servato il retto corso, che saran di più potente caduta.

Questo accade perché l'acqua di caduta potente cava il terren del loco da lei percosso e lo1 scarica, dove il suo corso si fa più debole che sotto il moto refresso dell'acqua; il quale essendo mosso in verso il cielo, in ogni grado di moto si fa più debole, tanto ch'al fine perde tutta la sua potenzia e, mancandole la potenzia in tal refressione, ella lascia cadere sotto di sé tutte le gravità tolte dal loco da lei percosso; e dopo tale inondazione l'acqua abbassa2 e trovasi chiusa in fra la materia, che le[i] prima condusse, e in fra la argine, donde ella discese.

Dell'acqua che pe' diluvi discende delle chiuse de' fiumi, sol a quella sarà riservato il suo retto corso dopo esso dilu[v]io, la qual fu di più debole e lenta caduta.

Questo accade, perché quella che lentamente si move, fa debol percussione; onde ne seguita, ch'ella poco leva del fondo da lei percosso, e per conseguenza poco pone sotto il moto refresso dell'acqua, onde per questo dopo tal [di]luvio l'argine resta qui bassa, e tutta l'acqua che cade, seguita il corso suo, dove l'argine è più basso, e per questo qui fia il retto corso di tutta l'acqua del fiume insieme coll'acqua di debole caduta.

Of the water that falls from the sluices of rivers: the straight course will be preserved in those parts where the fall is of greatest force.

This happens because water of powerful fall hollows out the ground of the place it strikes and unloads it where its course grows weaker, that is, beneath the rebounding motion of the water; which, being moved back toward the sky, becomes weaker at every degree of motion, so that in the end it loses all its power. And, its power failing in that rebound, it lets fall beneath itself all the weights taken up from the place it struck; and after such flooding the water sinks and finds itself confined between the material it first carried and the bank down which it descended.

Of the water that descends in floods from the sluices of rivers, only that which was of weaker and slower fall will keep its straight course after the flood.

This happens because water that moves slowly makes a weak impact; whence it follows that it lifts little from the bottom it strikes, and consequently deposits little beneath the rebounding motion of the water. And so, after such a flood, the bank here remains low, and all the water that falls follows its course where the bank is lowest; and for this reason the straight course of all the river's water, together with the water of weak fall, will be here.

Which water keeps its straight course below a river sluice

Force of the fall governs scouring of the bed and the deposition of debris after a flood

Hydraulics Geology

Leonardo argues that below a river sluice the straight, central course of the current is preserved wherever the fall is most powerful. A forceful fall hollows out the bed it strikes and, as the rebounding water weakens climbing back toward the surface, drops the debris it had lifted, so that after a flood the channel is left confined between its own deposits and the bank down which it descended. Where instead the fall is weak and slow the impact lifts little, the bank stays low, and all the water afterward runs straight over that lower bank. The folio is a block of text with no diagram.

On this page

Where the straight course of a stream is preserved below a sluice

Leonardo states that the straight course (retto corso) is kept in the parts of most powerful fall. After a flood, water of weak and slow fall keeps its straight course because it leaves the bank low and all the water then follows the lowest bank.

Scouring of the bed and deposition of the lifted material

Powerful falling water excavates the ground it strikes and carries off the loosened weights until, its rebounding motion spent, it drops them beneath itself. After such flooding the water sinks and lies confined between this deposited material and the bank.

Reader's Edition — described with AI from the e-Leo transcription.