Recently published Ornithological Works. 669 



species of the typical genus. The '' Meropes,'' " Upupoe/' 

 " Coracise," and " Halcyones/' which, according to the 

 author^s views, should also be treated as " Orders/^ continue 

 the series, which is concluded by the Pici and Cuculi. 

 We are not sure that much is gained by dividing the Picarise 

 of Nitzsch into so many constituent parts, but it is ohvious 

 that these eight groups are all distinguished by well-marked 

 characters. 



"Whatever may be thought of Dr. Ilartert's nomenclature 

 and system of arrangement, the students of Pahearctic Bird- 

 life will find an enormous amount of information recorded 

 in this work, and should not fail to give it close attention. 



95. Headley on the Flight of Birds. 



[The Flight uf Birds. By F. W. Headley. London: Witherbj & Co., 

 1912 ; pp. i-x, 1-163.] 



In these days of Aviation, the subject of a bird's flight is 

 one of more than usual interest, and Mr. Headley, in the 

 book before us, gives us an admirably clear and at the same 

 time concise account of the whole matter from all points of 

 view, comparing at the same time the powers of wingless 

 man and winged fowl. He endeavours to avoid all excess 

 of technicalities, and illustrates his meaning by the aid of 

 photographs and diagrams. 



The mathematical details are naturally of primary im- 

 portance and of the highest interest, while the author has 

 discussed them in a manner suited to the general public. 

 These cannot be adequately treated in an Ornithological 

 journal, but all our members should make themselves ac- 

 quainted with the mechanics of flight, the methods adopted 

 by the bird, and how its structure and plumage is in perfect 

 accord with its needs. 



Mr. Headley first calls our attention to the fact that for 

 successful flight perpetual forward motion is necessary into 

 undisturbed fields of air : otherwise the resistance of the air 

 would not be sufficient, and it is the vertical component of 

 this resistance (which acts perpendicularly to the surface 

 exposed to it) that is the sole force sustaining and uplifting 



sER. IX. — VOL. VI. 3 a 



