vii FLIGHT 217 



equally certain with regard to less flurried flight. 

 The slowness of a bird's stroke compared with an 

 insect's was most remarkable, a common fly attaining 

 the astounding rapidity of 330 per second, and a bee 

 190. It must be borne in mind that the extremity of 

 a long wing may move very rapidly, though the number 

 of strokes per minute be few, and that a bird's wing 

 with its long sweep may produce more effect, even 

 when we allow for the greater weight to be supported 

 and propelled, than the insect's can by its many rapid 

 pulsations. 



There is the further question of the comparative 

 velocity of the up- and downstrokes. Photography 

 has proved what we should not have anticipated — viz., 

 that the upstroke is the more rapid of the two. 1 



Duck 



Duration of Duration of 



upstroke. downstroke. 



— sec. *p sec. 



60 60 



^ 4^ 



Pigeon -^ sec. ^-- sec. 



& 60 60 



01 jo 



Buzzard — 2 sec. ^ sec. 



60 60 



This is accounted for by two facts — (1) that the 

 air offers little resistance to the passage of the rounded 

 upper surface ; (2) that when the pace attained is great 

 the air itself lifts the wing and relieves the Elevator 

 muscle of a great part of its work. 



1 See Marey's Vol des Oiseaux, p. 101. 



