3S9 
i88o.] 
Flighty Aspirations. 
to the possible vagaries of a screw-propelled plane. It 
seems to me to be a structure without any life in it, unable, 
as it were, to help itself. It represents the fag end of a 
bird’s flight when he rests from his labours, and, by the aid 
of the impetus gained, continues his journey with motion- 
less wings extended as a plane. , • 
This plane he can also use as a propeller ; and therein 
consists one of the grand instances of superiority over any 
other mode of aerial transit. But it is the manner of its 
use which demands from us the acknowledgment ot it 
great advantage. . . . , . ^ 
The adtion of a bird’s wings is exerted in a space of 
three dimensions, measured by the length of the wings from 
tip to tip— the arc of vibration of wings— and the length of 
the body, to which might perhaps be added the effedt, both 
in front and rear, of a readtion arising from their attack 
upon the air. The stability which by this process is at- 
tained, within the knowledge of every one, exists in spite of 
the fa£t that the wings are moved up and down, although 
alternately above and below the centre of gravity of the 
bird, and although the head and the tail are really adting as 
the scales of a balance of which the wings are the centre. 
Those who have watched the flight of wild ducks must 
have been struck with the peculiar contour which they 
present. The wings appear to be the cross centre of a 
cylindrical shaft. The dimensions of a tame duck which I 
have just measured are-Extreme length from toe to beak, 
2 q! inches ; from beak to root of wing, 14 inches ; stretch 
of wing from tip to tip, 32 inches; so that the wings are 
only 2i inches longer than the whole body, which in flight 
would present this shape : 
In all probability this bird flies in a stratum of air- 
taking 1 foot as the extent of vibration of wing more than 
6 cubic feet of which is put into a state of commotion 
in every 7 sense conducive to its support and balance. 
Whatever may be thought, therefore, as to the folly of 
obtaining flight by wing-vibration, nevertheless it is to that, 
or to some application of the principle, that we must come 
in our attempt to make flight serviceable for man. 
It is very doubtful whether man has the power necessary 
for the manipulation of wings of dimensions and strength 
