vii FLIGHT 225 
his way, the further end of the lever moving with 
great velocity and force. The short wing must beat 
frequently and with a longer swing. Put the wing of 
a Swift beside that of a Duck, and compare the two. 
The cut of them at once shows the flight of each. 
The Swift’s is long and very narrow towards the end, 
the duck’s short for its size, and rounded. The Swift 
7. 
Fic. 62 
Breast-bone of (a) Frigate Bird, (4) of Duck, rds natural size. 
cL, clavicle; co, coracoid ; K, keel; st, sternum proper. 
covers, probably, 60 miles in the hour without great 
effort and without a very rapid stroke : the duck keeps 
up a good pace, but only by means of strokes 
that are at once very rapid and very long. If a 
Gannet be watched as he goes leisurely onwards it 
will be seen that his wings do not rise much ‘above 
or.descend much below a horizontal line from the 
Q 
