286 



SMITHSONIAN CONTRIBUTIONS TO KNOWLEDGE 



VUL. _'/ 



I note here thai the measurements were made on a live bird and that it was 

 impracticable t<> gel the separate weight of the wings except by estimate, hut the 

 two wings may be estimated collectively as 1 ] lbs., the whole weight being 2| lbs. 

 to 3 lbs. 



Approximate values: 



Weighl of the bird complete, 3 pounds. 

 Length of bird, 23 inches. 

 Spread of wings from tip to tip, 5 ft. 5 in. 



Complete curtate area of both wings (that is, the area of the shadow of 

 the bird's wings when these are fully extended under a vertical sun) i> 600 

 square inches, or nearly 4 sq. ft., consequently each square fool of the bird's 

 sustaining surface carries : | lbs. Diedral angle nearly 150 . 

 When the bird is soaring in a nearly calm atmosphere, which it inexplicably 

 does, — soaring I mean nearly in the line of the observer's eyes and coming di- 

 rectly to or going directly away from him, — it presents nearly the following 

 appearance: 



Fig. 1.— Jamaica, Mch. 22, 1900. "John Crow." Sketch soaring horizontally, by W. H. Holmes. 

 Weight :; lbs. Total wings area=546 in. Perpendicular distance c below a 6 = 3.3 in. = 



\ 546 . 



CI'. 



CG~. 



Fig. 2. — Another. 



<•!•. -CG, = ?,". in. 



\ r,ir; 



Pigs. 1 and 2. — Type sketches of wings by Holmes from a mean of positions taken from his own 

 sketches and photographs, anu also from sketches and photographs by Langley. 



Fig. 3. Type sketch of same birds, average type, position of wings. — S. P. Langley 



541 



CP.— CG,= ?,A) in. 



6.5 



PW 



Fig. 4.- Average typical position of wings in soaring gull. From memory by S. P. Langley. (The 

 scale here may be taken approximately at — J. 



