Harbour dredge and wing-lifting flight studies
A plough-dredge to clean a port; curved springs; a man lifting himself on two wings
The upper drawing shows a device for cleaning out a harbour: a toothed 'plough' (ab-nm) lowered from a boat to scoop mud, hoisted by two windlasses a and b so the boat can pass beneath and be filled. The lower half turns to flight, with sketches of curved springs of horn or steel set into a reed and a note that impetus keeps birds aloft while their wings are not pressing the air. A final study shows a wing over a weight on a pulley, with a calculation that a man of 200 pounds could raise himself on two wings with a force of 300 pounds.
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Plough-dredge for cleaning a harbour
The plough mn carries prongs shaped like a ploughshare and blade to bite into the mud, and is pierced behind like a net so the water is not trapped in the box. Lowered from a boat over the spot to be dug, it is drawn by windlass b beneath windlass a, which lifts it full to its roller; the boat then passes underneath and the plough is unlatched to dump its load.
A man raising himself on two wings
A wing is shown above a weight on a pulley, labelled solaro (frame) 150 pounds and n (the man) 200 pounds. If the man weighs 200 pounds at n and lifts the wing with its stock of 150, then once he is upon the instrument a force of 300 pounds would lift himself with two wings.
Springs of horn or steel set in a reed
A curved spring is drawn, annotated 'better' (me[g]lio). A second type is a spring of horn or of steel, fixed on willow wood and set into a reed. Leonardo pairs this mechanical spring with his observation of natural flight.
Impetus sustains a bird in flight
Alongside the spring note Leonardo writes that impetus keeps birds in their flying course during the moments when the wings do not press the air but instead rise upward.