( 419 ) 



OBSERVATIONS ON THE FLIGHT OF BIRDS AND THE. 

 MECHANICS OF FLIGHT. 



By E. W. Young, M.I.C.E. 



(Read February, 1903.) 



It is only quite lately that the possibility of mechanical flight has 

 been seriously entertained. Within my own memory even scientific 

 men were quite at a loss in attempting to explain the flight of birds. 

 No experiments had been made of the effect of wind upon inclined 

 planes, while the deductions from theory were grossly erroneous. 

 Some experiments made by myself with rough apparatus thirty years 

 ago convinced me of the incorrectness of theory, and at nay sugges- 

 tion the Aeronautical Society of Great Britain, of which I was a 

 member, constructed an apparatus in 1873-74 for ascertaining the 

 effect of wind upon inclined planes, as an indispensable preliminary 

 to the construction of machines for mechanical flight. Since those 

 days many careful and elaborate experiments have been made by 

 Maxim, Professor Langley, and others, and the solution of the 

 problem of mechanical flight seems to be close at hand. 



There is still some mystery connected with the flight of birds 

 which calls for explanation ; chiefly the extreme ease with which 

 some birds fly, or rather soar. In endeavouring to account for this, 

 let me begin by an elementary description of the action of a bird's 

 wing during flight. 



One of the best positions for studying the flight of birds is the 

 deck of a steamer. If we watch a gull following the vessel with 

 quietly beating wings, we notice that the body of the bird scarcely 

 perceptibly drops during the upstroke of the wings, showing that 

 the bird is supported, not only by the downward stroke, but during 

 the upward stroke of the wings ; that is to say, the wind strikes the 

 underside of the wing even during the upward stroke. This is 

 effected by the peculiar construction of the bird's wing, in which the 

 muscles are springs tending to pull the after edge of the wing down- 

 ward to meet the rush of the wind. During the downward stroke 



