way against 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 techni- 
calities, 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 illustration showing the goshawk in flight. As they 
sweep downwards, 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 move- 
ments 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. 
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