the wings inclined upward at an angle instead of being fully extended; the pigeon is an example.
§ 17. Author's Experiments. Remarks and Summary (continued).—It is of some interest to interpret the forms of flight path made by the author's aerodones, in typical cases, in the light of the ballasted aeroplane experiments described in § 3.
It is evident that the rising and falling curve of the trajectory Fig. 25, and in other similar cases, constitutes a portion of the wave-like flight path referred to in (2) § 3; and if we continue this curve as though the launching had taken place from a greater altitude, that is to say, as if the surface of the earth had not intervened, we should have a curve of the form shown dotted in Fig. 29, oscillating about a mean gliding path represented by the line a a. In this figure the curve of flight has also been continued retrospectively in order to show more clearly the sinuous flight curve of which the actual trajectory forms but a fragment. It is evident that the angle of the line of mean flight depends upon the design of the aerodone, the less the total resistance of the latter in proportion to its weight, the less the angle y: this is a matter of aerodynamics.[1] It is further evident that the greater the launching velocity the greater the distance at which the line of mean flight path passes vertically over the point of discharge, i.e., the greater the distance h in the figure.
In the particular flight depicted in Fig. 25, it is evident that, owing to the existence of a head wind at the time of the experiment, the velocity was considerably higher in effect than the ordinary launching velocity; it would in fact under these circumstances be equal to the sum of the launching and wind velocities. In consequence, the height of the mean flight path line is considerably greater in this case as is represented in Fig. 30, and as a result we have nearly three complete "periods" of the flight path oscillation before the aerodone finally comes to earth. The question of whether there was actual soaring taking place
34
