18 
No. 8. — The consequence of a still greater celerity of the action of 
those organs within the same time, enlarging the angle of 
ascension and exhibiting a more marked falling oflf in the 
degree of motion. 
No. 9. — The last one of a series of effects resulting from the force 
of opposing winds, under the action of the wings at the 
rate of three strokes per second of time, thus : if the wild 
duck, for example, be met by a wind of about twenty-five 
miles per hour, he will be thereby raised on the line of No. 
7 ; if the velocity of the current of air should increase to 
about fifty miles per hour, he will rise on that of No. 8 ; 
and if still further augmented to about seventy-five miles 
per hour, as in a hurricane, he will ascend perpendicularly, 
as indicated by the broad line of this figure, without any 
alteration in the movements of his wings. 
No. 10. — The same bird poised in the air on expanded wings by the 
force of a tornado of one hundred miles per hour, and which 
sustains his weight without any exertion on his part, but, 
at the same time, gradually drifts him backward, as indi- 
cated by the horizontal dotted line. 
No. 11. — The animal whilst in this situation illustrates the principle 
and exhibits the manner of flying the kite, thus : the force 
of the wind striking against the under surface of the wings 
sustains his weight, while the tendency of the latter to de- 
scend is precisely similar, in effect, to the power exerted 
through the string held in the hand of the kite-flyer ; and 
on a sudden cessation of the wind he will instantly begin 
to gravitate on the dotted line towards, and thus soon reach 
the earth at, the figiire of the boy. 
No. 12. — The spiral and vertical ascension of certain small birds 
under the greatest celerity of wing : this being the only 
manner in which they can rise by means of those organs 
alone, on a greater angle than that indicated at figure No. 8. 
No. 13. — The spiral ascension of the buzzard, and some others of the 
falcon species, on expanded but motionless wings, as already 
explained. 
No. 14. — The smallest one of the two lines composing this figure 
shows the true angle on which the wings are raised, with re- 
ference to the line of motion in the process of flight proper. 
