1885. | The Problem of the Soaring Bird. 1171 
motors to drive the machine against the air. Two requirements 
are still needed. The device must be steered and kept in posi- 
tion. When it is remembered that the rear expansion drives the 
bird forward, any change in the extent or position of one wing 
which is not shared by the other would retard or accelerate the 
motion of the changed side relatively to the other, and serve to 
determine the direction of motion. A balance still needs to be 
preserved. The bird gives significant hints here also. The 
heavier it is the steadier is its motion, and a device large enough 
to sustain the weight of.a man may be qualified by its inertia to 
assist in preserving its own equipoise. 
The most important points of this subject have now been 
given. Experiments with artificially induced currents of air, 
requiring a steam-engine to be transported to the sands of Flor- 
ida, were expensive and productive of only negative results. 
Much time and means were wasted in this way, and all my efforts 
previous to the summer cyclone above recited seemed abortive, 
excepting in the settlement of the facts of soaring as shown by 
the birds. The moment the idea that gravity was the motive 
power and not the air, was entertained, the whole matter became 
luminous. No steps subsequently taken have been in the wrong 
direction, and I shall return to the prosecution of the subject the 
moment prudence permits. 
The relation of the soaring birds to artificial air-navigation fills 
the whole subject with a sort of pathos. A turkey-buzzard, most 
despised of all the birds, employs mechanical activities by using 
a device of such simplicity that compared to it a common grind- 
stone is a complex machine, for the purposes of air-locomotion 
in the search for carrion, with conspicuous and complete success, 
itself being a working model of the very thing which man has 
worked, and sweated, and died to possess, and he has never seen it! 
For a period of time coéval with his own existence on this 
planet this thing has been going on, and the world is full of it 
now, and still the mature conviction of both common sense and 
science is, that it is impossible. 
