a head-wind with the minimum of effort, by partly flexing the 
wings and gliding downwards: -at the end of the descent, by 
turning the body sharply upwards, and spreading the wings to 
the fullest extent, they are lifted up, and driven forward, like 
a kite. 
Marey and Pettigrew, long ago, showed conclusively, by means 
of photography, that our conception of the movement of the wing 
during flight was far from correct. 
To avoid a long and tedious description, and many technical- 
ities, it must suffice to say that the wing of a bird possesses very 
considerable freedom and range of movement at the shoulder 
joint. Certainly, during some phases of flight, the wings are thrust 
forward and extended to their fullest extent, so that the outer 
margins of the wings come to lie almost parallel with the long 
axis of the body, as may be seen in the spirited illustra- 
tion showing the goshawk in flight. As they sweep down- 
wards, and backwards, they lift the body and drive it forwards, 
At the end of the “sweep” they are “ flexed,” that is to say, bent 
at the elbow and wrist-joints, while at the same time they are 
raised and brought forward above the body for a repetition of the 
stroke. These movements are too quick for the eye to follow, 
but they have been fixed for us by the camera. 
Marey devised an ingenious experiment in his endeavour 
to discover the movements of the bird’s wing during flight. He 
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