How a Bird Climbs and Steadies in Straight Flight
Driving the center of gravity back to climb; an even wind aligns the glide
Two notes on gliding flight, illustrated by small sketches of birds on outstretched wings above and across the leaf. To climb, the bird drives the center of its gravity back toward the center of its wings so as to hold an oblique, rising attitude. An even wind, meanwhile, tends to straighten a soaring bird, setting its extremities equidistant from the center of its bulk, so that it first wheels in a circle and then settles into straight flight.
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Driving the center of gravity back to climb
When the bird wishes to climb, it shifts the center of its gravity backward toward the center of its wings, and does so in order to hold itself oblique.
An even wind aligns the bird for straight flight
An even wind tends to straighten all the unequal parts of the bird, setting its extremities equidistant from the center of its bulk, in birds that sustain themselves on the wind without beating a wing. Such a bird therefore first makes a circular motion and then a straight one.
Sketches of gliding birds
A small bird on outstretched wings is drawn at the upper right, and another glides across the middle of the leaf along a long ruled line, both without further transcribed text.