Book Notices and Reviews. Il9 



The quantity of air acted upon by the wings in flight is in shape of a solid sector 

 swept out by a radius equal to the span of the wing. 



Wherein is exjilained in what manner the air offers resistance to the stroke of the wings. 



If the velocity wherewith the wings of a Bird i i flight aie bea'en isequal to the velocity 

 wherewith the underlying air recoils to the beat of the wing, the Bird remains in the same 

 place. 



Again, if the velocity wherewith the wings are beaten is greater than the velocity 

 wherewith the underlying air recoils to the beat, the Bird will ascend, and the rate of its 

 ascent will be equal to the difference between the two velocities. 



The power of the muscles that beat the wings is greater by ten-thousand timos than 

 the weight of the Bird. 



Wherein are set forth the reasons for the immense power of tlie wings 



In what manner an oblique transverse force may proi.el straightly a body unaffected 

 by the motion. 



If a Bird suspended in the air strike with its outspread wings the undisturbed air 

 with a motion perpendicidar with the horizon, it will fly with a transverse movement 

 parallel to the horizon. 



Wherein is explained the way in which the horizontal flight of Birds is affected. 



The use of the tail of the Bird is to direct the course of flight upwards and downwards; 

 but not to the right and left. 



How and by what means Birds, when Hying, alter their course to.the right or to the left. 



If the body of the Bird A.C. be moved at an acquired speed through the air in a long- 

 itudinal direction from towards A, and if while flying it bends its outstretched neck with its 

 head B.A. towards the left side B.I. the course of ti e entire Bird is deflected towards B.I. 



It does not appear possible that birds flying horizontally, can depart quii'kly from their 

 course by the transverse flection of their head and neck. 



How Birds without flapping their wings, can sometimes ride in the air for a short time 

 not only horizontally, but also obliquely upward. 



Haw the flying impetus acquired by a bird is checked on landing. ■ . .• 



It is impossible that men should be able to fly craftily by their own strength. 



The 'booklet runs into 40 pages, is well and cleatly pt-inted 

 on good paper. The author deals with his suhject in a terse a»nd 

 practical manner. The book is excellent value at the published price, 

 and will be read with interest by bird-lovers, as well as by tlio.'fc 

 interested in aeronautics. 



British Birds in their Haunts, by the late Rev. C. 

 A. Johns, B.A., F.L.S., The Society for Promotmg- Christian 

 Knowledge, Northumljerland Avenue, London, W.C. — .5s. 



This is a new edition (twelfth), and the following quo- 

 tation from the perface clearly defines the Author's purpose: 



" The Author begs expressly to disclaim all idea of pro- 

 " posing the present volume as a substitute • for the comprehen- 

 " sive work of Yarrell .... which must always remain the 

 " indispensible book of reference for the British Ornithologist. 

 " Yet he does venture to hope that he has provided/ tlie lover 

 " of nature with a pleasant companion in his country walks, 

 " and the young Ornithologist with a Manual that will supply 

 " his present need and prepare him for the study of more 

 " important works." 



This the Author has certainly accomplished, and the re- 

 sult is a very readable and well got up book, the text pro- 



