60 JOURNAL OF THE 



Geneva a large work in which he describes the curvilinear move- 

 ments of the falcons. The oblique downward motion "was 

 sufficient to carry it without effort as high as the elevation from 

 which it came." Monsieur Morey* says this is an exaggeration. 

 Observers say birds can sustain themselves in the air by the 

 use of the wind alone. Count d'Esteruo, in a remarkable mem- 

 oir on the flight of birds, says, " Every one can see some bird 

 practicing this method of flight; to deny it is to deny self-evi- 

 dent facts." M. Morey acknowledges that he has seen it, but 

 attributes it to the bird passing alternately from quiet air to a 

 current. • 



A large part of the discussion iu Nature, through Vols. VIII — 

 XXVIII, hinged on a misunderstanding between the disputants 

 as to the meauing of the word hovering ; some discussing the 

 matter from the point of view of motionless wings, while others 

 treated it having in mind a slow flapping of the wings, while 

 the bird remained over one place on the earth. 



It has loug been observed that some soaring birds, after rising 

 to the height of a few hundred feet by flapping their wings, soar 

 around in great circles on motionless wings and continually rise 

 higher and higher until they are several miles from the surface 

 of the earth. S. E. Peal, writing from Sapakati, Sibsagar, 

 Asam, gives an account of this manner of the translation of 

 soaring birds observed by him.f Whenever the birds attempted 

 to soar the wind was blowing. When they began to circle the 

 resultant course of motion was upward, and toward the point of 

 compass to which the current of air was moving. In soaring, 

 when facing the wind, the slant of the wing was such as to cause 

 the birds to rise, but as they turned with the wind the slant of 

 the wing was changed to give a slight downward motion, then 

 again turning to face the wind they rose higher than before, and 

 at each completion of the circle the bird was farther from the 

 earth. In this way the course of the bird through the aii was 



-Phenomena of flight in the animal kingdom 

 fNature, Vol. XX IT, p. 10. 



