268 Recent Ornithological Publications. 



wards and upwards, while during the reverse movement the 

 position of its wings tends somewhat to arrest its progress ; but 

 as it still slides upwards, what is lost in speed is gained in ele- 

 vation. 



M. Marey makes some comparisons between the flight of 

 large and of small birds, and shows that, on the whole, the 

 work done jjer stroke is proportional to the bird's weight ; but, 

 with due deference to him, he appears to overlook the fact that, 

 as the stroke of the larger bird takes a longer time, the actual 

 work done during any given time is less, and, unless the smaller 

 bird has a very great surplus of strength (which there is no 

 reason to think), a similarly-built bird of above a certain weight 

 would be unable to fly at all — soaring, which is chiefly depen- 

 dent on other causes, being left out of the question. The only 

 escape from this difficulty seems to be in the supposition that 

 the tip of the wing of the larger bird strikes the air with a 

 velocity absolutely greater than that of the smaller one, in 

 which case a moderate increase of velocity in proportion to the 

 weight would suffice, as the resistance of the air is here nearly 

 proportional to the square of the velocity. 



In a prior course of papers M. Marey had elucidated the flight 

 of insects, which, though mechanically simpler, presented great 

 diflUculties, from the small size of the subjects of his experi- 

 ments ; and the whole undoubtedly forms the most important 

 contribution to our knowledge of the subject of flight that, 

 with the exception of the standard work of Prechtl*, has ever 

 been made. 



3. Dutch. 



As our readers must by this time be able to judge for them- 

 selves of the merits of Mr. Keulemans as an ornithological 

 artist, it would seem somewhat presumptuous for us to say 

 much of the plates which decorate his work f written for the 

 bird-loving public of his own nation, whether scientific or not. 



* Untersucliungen iiber den Flug der Vogel. Wien : 1846. 



t Onze Vogels in Huis en Tuiu, besclireven en afgebeeld door J. G. 

 Keulemans, Adsistent aan 'sllijks Museum Aau Natuui-lijko Ilistorie. 

 Deel i. Leyden : 1809. Koy. 8vo. 



