220 THE STRUCTURE AND LIFE OF BIRDS cuap. 
winging their way quite unconscious of cameras, and 
sensitive plates, and fame. On the other hand, Mr. 
Muybridge’s American Eagle, with his somewhat 
draggled plumes, looks like a scared captive, conscious 
that the camera is being aimed at him. However, it 
is only under conditions like these last, that photo- 
graphs such as those of Professor Marey, showing the 
position of the wing at every stage, can be obtained. 
When the bird is flying with great energy, he raises 
his wings high till in some cases they touch one 
another, and this is the cause of the slapping noise 
that we hear when a Pigeon rises from the ground. 
The wing next moves forward and downward, its 
under surface looking backwards and downwards. In 
its forward movement it meets with little resistance, 
since it cuts edgeways through the air. When it can 
strain no further forward and down, it is drawn back- 
ward and bent sharply at the wrist-joint, facing during 
the process forwards and downwards. During the last 
period of the upstroke there is a further turn, and it 
moves edgeways forward! This description of the 
movements of the wing refers to very vigorous flight, 
such as we most commonly see when the bird is 
getting up steam. When he has plenty of way on 
there is no need for him to take these very long and 
exhausting strokes, unless, like the Duck, he is one 
of those that seem always to fly with effort. In birds 
of long flight, the wing does not rise very high or 
descend very low, and it is flexed very little, if at all, 
when it is raised. These points can be made out if a 
Gull is watched when it is flying steadily. In someof 
1 Further details under next heading. 
