228 



ANIMAL MECHANISM. 



nblo to study is very small as yet ; the following arc tlio 

 results obtained : 



Sparrow . 

 Wild duck 



M"iir bux7;ir.l 

 Srivrr.li owl . 

 Buzzard 



Revolutions of wing 



]u r second. 



13 



9 



8 



51 



The frequency of the strokes of the wing varies also, according 

 as the- liird is first starting, in full flight, or at the end of its 

 flight. Some birds, as we know, keep their wings perfectly 

 still for a time ; they glide upou the air, making use of the 

 velocity already acquired. 



Relative duration of the depression and elevation of the wing 

 r'uiitrary to the opinion entertained by some writers, the 

 duration of the depression of the wing is usually longer than 

 that of its rise. The inequality of these two periods is more 

 distinctly seen in birds whose wings have a large surface, and 

 which beat slowly. Thus, while tho durations are almost 

 equal in the duck, whose wings are very narrow, they are 

 imi>qu;il in the pigeon, and still more so in the buzzard. 

 The follow ing are the results of our experiments : 



1 1 is more difficult than would have been expected, to determine 

 the praise instant when the direction of the line traced by the 

 1 1 ',(- i-.-i nh changes. The periods during which the soft iron 

 is lust attracted and then sot free, have an appreciable duration 

 \\li u the blackened cylinder turns with sullicient rapidity to 

 i-iiable us to measure the rapid movements which are the 

 subjects of this iiiijuiiy. The inflections of the line traced by 

 the telegraph then become curves, the precise commencement 



