Righting an overturned bird; the lark's straight ascent
Turning the wing tips earthward to recover, and descending by throwing the wings back
Two schematic figures of a bird tumbled onto its back accompany notes, written inverted, on recovering control in the air. Keyed to the letters a and b, the text directs that when the bird is upside down (a) it thrusts its wing tips toward the ground (b) and bends its broad tail toward its back to right itself, and that a bird falling edgewise should raise its wings toward its back. A further remark observes that most birds can only climb in a spiral, except the lark, whose wings become so perforated on the upstroke that they offer no resistance. A marginal passage adds that to descend the bird throws its wings backward so its center of gravity passes forward. A small sketch appears in the lower left margin.
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Righting an overturned bird, marked a and b
When the bird is upside down, as at a, it thrusts its wing tips toward the earth, as at b, and bends its broad tail toward its back, and so rights itself to its usual attitude. If it falls edgewise it instead raises its wings toward its back to recover.
The lark climbs straight by perforating its wings
Many birds can only rise by a screw, that is by circular motions. The lark is the exception: in raising its wings it perforates them so that almost the whole wing lets the air through and offers no resistance, letting it climb straight.
Descending by throwing the wings back
The marginal note explains that when the bird wishes to descend it casts its wings backward. The center of their gravity thereby moves outside the middle of the wings' resistance, so the bird falls forward.