1921. 



Notes, 



27 



neighbourhood five species of Bat, viz. : Pierygisies Leisleri, the Hairv- 

 armed Bat ; Pipistrellus p.pistrellas, the Pipistrelle ; Myotis Daiibentoni, 

 Daubenton's Bat ; Myotis Nattereri, the Reddish-gray Bat; and Plecotus 

 auritus, the Long-eared Bat. Many years ago I recorded the Whiskered 

 Bat from here, but I am now doubtful as to its having been correctly 

 identified. ^ 



Charles Langham. 



Tempo, Co. Fermanagh. 



REVIEW. 



THE SOARING OF BIRDS. 



Soaring Flight : a Simple Mechanical Solution of the Problem. By 



Lt.-Col. R. Dii ViLLAMiL (late R.E.), author of "ABC of Hydro* 

 dynamics," &c. London : Charles Spon. is. 6d. net. 



In a modest little pamphlet consisting of only 48 pages Lieut.-Colonel 

 de Villamil has put forward what appears to be a perfectly triumphant 

 solution of the question — How are some of the larger birds enabled to 

 rise in spiral ascents to a great height in the air with no visible effort 

 on their own part, and certainly without the exertion of once flapping 

 their wings ? The simplicity of the explanation offered — when one 

 looks back on the amount of controversy that has been expended over 

 the question — is little short of startling. 



To all students of the flight of birds this subject of " soaring flight " 

 has hitherto proved a complete stumbling-block. The ancient Hebrew 

 sage who spoke of " the way of an eagle in the air " as first of the four 

 things that were too hard for his understanding would seem to have had 

 quite as good a grasp of the nature of the problem as most of the biologists 

 who have written of it in recent years. Professor Charles Roy (in the 

 article on " Flight " written for Newton's " Dictionary of Birds ") was 

 able to dismiss pretty summarily nearly all the theories put forward on 

 the subject by stating that they fell naturally into two great categories' — 

 those that ignored the laws of dynamics and those that were based on 

 inexact knowledge of the observable facts. Two — and only two — of 

 the then existent hypotheses were partially — ^and only partially — exempted 

 by Professor Roy from this sweeping condemnation. These were the 

 theory of upward currents of air, and that of varying velocity of the 

 wind at different heights. To the first of these there is the obvious 

 objection that it postulates for the ascending currents a height, a strength, 

 a command of space, and a numerical abundance that we have no reason 

 to believe them to possess in any part of the world. To the alternative 

 theory (though Professor Roy gave it a hesitating preference) there is 



