THE SOARING OF BIRDS 107 



account for what he saw. M. J. Marey, the author 

 of Animal Mechanism , after watching flocks of pelicans 

 on the coasts of the Mediterranean mount up to a 

 great height, and there soar for hours with no beat of 

 the wing, proposed to discover the way in which this 

 was done, and published the results of his labour in 

 a most fascinating book, entitled Le Vol des Oiseaux. 

 Amongst a mass of interesting facts and information 

 about the general phenomena of flight the following is 

 briefly the result of his inquiry into the soaring power 

 of birds. The soaring of the kites, condors, vultures 

 and peilcans has three points in common. In the 

 first place, the progress made, even if very slight is 

 against the wind. Secondly, they fly in circles or 

 ellipses, which are not parallel with the line of the 

 horizon, but oblique,* though to the observer who 

 stands below they appear horizontal. This last fact 

 was discovered by Bakounine, who, seeing a pair of 

 eagles soaring in the Carpathian Mountains, climbed 

 up to a point level with the tract of air in which 

 they were flying, and saw at once that the circles 

 were not horizontal a fact which Darwin also noted 

 in the soaring of the condors. Lastly, wind, how- 

 ever light, is a necessary condition. From these data, 

 M. Marey concludes that the soaring of a bird is to 



* Compare Mr Millais's accurate observation of the method of soaring on spirals 

 quoted at the beginning of this chapter. 



