Water flow through a nozzle and an eddy-driven machine
Flow proportional to velocity, a sea-channel sluice, and a siphon-fed rotating axle.
This page of Notebook F joins the measurement of water flow to the design of a water-driven machine. A top note states that the quantity delivered through a mouth or nozzle is proportional to the water's velocity, so that double speed yields double flow in the same time. A marginal note proposes a sluice-gate on a narrow sea channel, to close against storms and high tide and open at the ebb. The larger diagrams describe an 'accidental eddy' vessel fed by a siphon and stirred by an oblique-edged axle turning on a pivot, whose speed Leonardo compares to the beating of a bird's wings against the air.
On this page
Discharge through a nozzle is proportional to velocity
The measures of 'once' assigned at the mouths of water are greater or smaller according to the greater or smaller velocity of the water passing through. Double velocity gives double water in the same time, triple velocity a triple quantity, and so on without end.
A sluice-gate on a sea-fed channel
A marginal note directs the maker to fit a sluice-gate on the narrow channel that comes from the sea, so that it can be closed during storms and at the rising tide and opened at the ebb.
Vessel, siphon and rotating axle of an 'accidental eddy'
a m n is the vessel of the accidental eddy, a braccio and a half across at the mouth and two-thirds at the bottom, into which the siphon's mouth enters by the way a b, c d. The axle turning on pivot e should run faster than, or equal to, the water's inflow so the water assists its motion; making it faster than axle h costs more labour, while equal speeds of axle and water cost almost none. Leonardo cross-refers to the fifth book 'on birds', on the power of the wing-beat against the resistance of the struck air.
How the siphon feeds water behind the axle
The siphon must push its water behind the motion of the axle h, and do so upward along the line of the vessel's obliquity. Between vessel and axle there should be one finger's space and no more, so the water's excess weight does not impede the axle, whose cutting edge must be oblique as the drawing shows.