1 921.] Rece7itly pubHshed Ornithological Works. 551 



of India, lias been occupying his leisure for many years 

 in investigating tlie problem of fliglit, not only in birds, 

 but also in flying fishes and insects and even pterodactyls ! 

 He published in 191-1' a volnnie on tlie subject, which 

 we fear lias not attracted the attention it should have ; 

 for his work is of a most interesting nature, and he lias 

 devised a number of exceedingly ingenious instruments 

 and mathematical methods for recording the speed of 

 flight. 



The present short paper deals with the problem of soaring 

 flight. How does a bird whose body is heavier than the air 

 maintain itself at great elevations without [jcrceptible move- 

 ment of its wings and in a calm atmosphere ? 



In the present paper Dr. Hankin gives a summary of his 

 observations during the last ten years, and the conclusion 

 he reaches is that " soaring flight is inexplicable in the light 

 of existing knowledge." He believes that in some way or 

 other the energy involved is derived from the sun's rays, and 

 he hopes that a solution may eventually be discovered by ex- 

 perimental investigation. The introduction by Mr. Haudley 

 Page deals with tlie bearing of soaring flight on mechanical 

 aviation. 



Hurtert on the Palcearctic Birds. 



[Die Yogel der palaarktischen Fauna. Von Dr. Ernst Hartert. 

 Bd. ii. Heft xi.-xii. pp. 1345-1600; Heft xiii.-xiv. pp. i-xxiv & 

 1601-1764; Bd..iii. Heft xv. pp. 176-5-1892. Beiliu (Friedlander), 

 1920-1921. 8vo.] 



The numbers of Dr. Hartert^s invaluable work are coming 

 out more quickly now, and we have before us two double 

 parts, completing the second volume, and the first part of 

 the third volume, containing more matter than we can well 

 deal with in a short article. 



In parts xi.-xii. the balance of the Ducks, the Stegano- 

 podes, Tubinares, Pygopodes, Columbse, Pterocletes, and a 

 portion of the Liraicolae are dealt with. Parts xiii.-xiv. 

 contain the rest of the Waders and the Gulls (Lari). 



SER. XI. VOL. III. 2o 



