RCVfW3 



The Flight of Birds. By F. W. Headley, M.A., F.Z.S., 

 M.B.O.U., X + 163 pp., with sixteen Plates and many 

 text Figures. Witherby & Co., London, 1912. 5s. net. 



Those who remember the excellent account of " Flight " 

 given in Mr. Headley 's Stnicture and Life of Birds, or who 

 have read liis other contributions to the subject in the pages 

 of British Birds and other periodicals, may well expect 

 something especially good when a whole book from his pen 

 is devoted to the question. Nor will they be disappointed. 

 Mr. Headley has not been too ambitious, but has confined 

 himself to an account of what is knoA\Ti with some certainty, 

 wisely refraining from entering realms of (at present) unprofit- 

 able speculation. He has tried to make his account simple 

 for the ordinary reader — no easy task in view of the popular 

 horror of anything savouring of mathematics ! In this he 

 has on the whole succeeded very well, and his style is usually 

 as lucid as could be desired. He is perhaps not always very 

 consistent, in that a simple point is often elaborated very 

 carefully, while the explanation of a more difficult one is 

 condensed. But if he errs in this it is within narrow limits, 

 and there is no paragraph in the book which the most imtech- 

 nical mind could find difficult — a fact which speaks for itself. 

 The aviator's interests have been kept in view, but the book 

 is mainly for the bird-lover. 



The first chapter deals with " Gliding " as being a simple 

 form of flight, and contains a lucid explanation of the prin- 

 ciples involved in air-resistance. The next chapter deals M-ith 

 " Stability " and the adjustments necessary thereto. The 

 third takes a step further, to propelled flight — " Motive 

 Power." The principles of leverage and propulsion are 

 clearly expounded, and the phases of the wing-stroke are 

 fully discussed and well illustrated. The chapter on " Start- 

 ing " discusses the question of the difficulty some birds have 

 in performing that act, and from that goes on to speak of the 

 degree to which different species can rotate the wing. The 

 chapter ends by pointing out that large size is a disadvantage 

 in most aspects of flight. The author adds that large birds 

 are at a further disadvantage in the struggle for existence 

 owing to their long period of immaturity, but it is questionable 

 whether that is a necessary concomitant of large size, 

 although the rule seems to hold for birds so far as we know. 



