1872.] Natural and Artificial Flight. ae 
At the commencement of the flight the strokes of the 
wings are fewer, but more energetic ; in mid-flight they at- 
tain a regular rhythm, becoming again irregular at the 
moment of the descent of the bird. Fig. 4 shows the 
difference in amplitude and frequency of the wing-strokes of 
a pigeon during a flight of 15 metres. The extended 
tracings to the left indicate the movements at the com- 
mencement of the flight. A glance at the preceding table 
will be sufficient to show that Nature has here established a 
compensation for the diminutiveness of the organs of the 
smaller birds by rapidity of movement. 
To complete the series of investigations M. Marey studied 
the phenomena of natural flight, not analytical as hitherto, 
Fia. 5. 
=? 
, 
i] 
but as a whole. During flight two distinct effects are pro- 
duced,—the bird is upheld against the force of gravity, and 
it is propelled horizontally. And now arise the questions :— 
Is the bird sustained at aconstant elevation, or does it oscillate 
in a vertical plane? Is there a series of altations and de- 
pressions, the amplitude and occurrence of which cannot be 
observed by the eye? Is there any variation of velocity in 
the horizontal course? Does the action of the wings im- 
part a jerking motion? These questions are of the greatest 
import, if we observe the flight of birds with the view of 
applying the laws discovered to the subject of the artificial 
flight of man; and although some of them might have been 
answered by deductions from the result of preceding ex- 
periments, there can be no doubt of the correctness of 
VOLS 1. (N-S.) F 
