6 4 
BIRD-FLYING. 
ftrong. The bird drawing in its wings and holding 
them partially clofed eftablifhes itfelf in the air in a 
pofition where it leans flightly forward of a true perpen¬ 
dicular line : the wings and body together make a prac¬ 
tically flat furface or inclined plane fo set in the midft of 
the wind-forces as to fplit them, fo to fpeak, exactly on the 
line of cleavage, where the forces in front of the bird not 
only fupport it againft its tendency to fall, but at the fame 
time uphold it as againft the preflure of the wind-forces at 
its back; the wind-preflure againft the back of the bird con- 
ftituting an impelling force to produce locomotion—and 
the wind-preflure againft the front of the bird maintaining 
it in pofition to be driven forward—the path which it 
travels under thefe conditions being perfectly horizontal . 
Like the wing-movements of the fwallow, the wings 
of the gull may be feen to have a fort of nervous twitching, 
as the creature, ever watchful of the ftrength of the air- 
currents, increafes or diminifhes its wing-furface to increafe 
or diminifh the wind-force in relation to its falling weight. 
This feat of the gull, is, I think, the fort of thing for 
imitation, that men ambitious of “flying” fhould firft 
undertake to do. It will be a ftatic performance fure to 
immortalize the man who does it. 
