Wings 927 
state of our knowledge. Suffice it to say that if we will 
think of a bird flying through the air when we ourselves 
are swimming in the water, we can realize the achievement 
more vividly than from any amount of descriptions and 
diagrams. 
The under surface of a bird’s wing is concave; and 
Fie. 262.—Wing of living Golden Pheasant; rounded and curved for short, 
sudden flight. 
while the front edge is rather straight and firm, the hinder 
rim of the feathers is soft and yielding; thus a downward 
stroke both raises the bird or holds it sustained at the 
height already reached and urges it in a forward direction. 
Similarly we push our hollowed palms backward and pro- 
pel ourselves through the denser medium of water. 
The manner of flight varies greatly in different birds 
