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Library/Paris Manuscript K/39

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Paris Manuscript K — 39

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Bibliothèque de l'Institut de France, Paris

Uccello che abbassa un'ala1:

Quando l'uccello è portato con fav[o]r di vento settantrionale e che lui si mova per iscirocco, esso tien ferma un'alia a greco alquanto sopra vento e abbassa l'alia di libeccio e fassene vela ricevendovi sotto la percussione del vento2 per obliquo, la quale alia rare volte batte, ma ben con essa si tempera secondo il maggiore o minore vento.

Uccello obliquo:

Quando l'uccello monta per moto refresso contro al vento, se lui non girassi intorno all'alia più bassa, e' tornerebbe indirieto per esso moto refresso col petto al vento, il qual vento l'arroverscerebbe. E montando per moto refresso colla schiena al vento tornerebbe indirieto sotto vento colla schiena.

Bird lowering one wing

When the bird is carried with the favour of a northern wind and moves toward the sirocco, it holds one wing still to the greco (northeast), somewhat to windward, and lowers the wing to the libeccio (southwest), making of it a sail, receiving beneath it the blow of the wind obliquely; which wing it seldom beats, but rather with it trims itself according to the greater or lesser wind.

Bird flying obliquely

When the bird climbs by reflected motion against the wind, if it did not turn about its lower wing it would be carried backward by that reflected motion with its breast to the wind, which wind would overturn it. And climbing by reflected motion with its back to the wind, it would be carried backward, to leeward, with its back.

Trimming a Wing as a Sail and Climbing Against the Wind

How a bird sets one wing to windward and turns on its lower wing

Flight Physics & Mechanics

Two notes on soaring and manoeuvring in the wind, accompanied by small pen sketches of birds. In the first, a bird carried on a northerly wind and heading toward the sirocco holds one wing fixed to windward and lowers the other to leeward, making of it a sail that catches the wind's oblique blow and is rarely beaten but only trimmed to the strength of the wind. The second note explains that when the bird climbs by reflected motion against the wind it must turn about its lower wing, or it would be blown backward and overturned, whether it faces the wind with its breast or its back.

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One wing held to windward, the other lowered as a sail

Carried on a northern wind and moving toward the sirocco, the bird holds one wing still to the greco (northeast), somewhat to windward, and lowers the wing on the libeccio (southwest) side, making of it a sail. This wing receives the wind's blow obliquely, is seldom beaten, and is used to trim the bird according to the greater or lesser wind.

Turning on the lower wing when climbing into the wind

When the bird climbs by reflected motion against the wind, unless it turns about its lower wing it would be carried backward, breast to the wind, and overturned. Climbing with its back to the wind, it would instead be driven backward to leeward with its back.

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