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SMITHSONIAN C'OXTIUBrTIONS TO KNOWLEDGE VOL. 21 



measures 5 feet, 5.7 inches, or 3 inches less than when fully extended in the hori- 

 zontal plane. 



5 Tin position of the center of pressure of the wing.— This is indicated on 

 two compo-board patterns, C and D. C was made from a fully extended wing, 

 while 1) was made from the wing in the soaring position. The centers of pressure 

 of the wings are about 2 feet, 0.5 inches apart, or 1 foot, 0.25 inches from the 

 central point of the bird's body. 



6. The position of the center of gravity of the soaring bird.— (Length of 

 buzzard, 26 inches.) The center of gravity of the soaring buzzard in the hori- 

 zontal plane, CG X , was found to lie % inches behind the tip of the beak and 16i 

 inches in front of the tip of the tail. 



The center of gravity of the soaring bird in the vertical plane, CG~, was 

 found to lie 2.8 inches above the ventral point of the body and 1.6 inches below 

 the dorsal point, the depth of the bird's body at CG, being 4.4 inches. 



In determining the center of gravity, the bird was frozen in the soaring 

 position, its wings making a dihedral angle of 150°. It was then hung up, first 

 horizontally and then vertically, and balanced till the line from which it was sus- 

 pended coincided with a plumb-line placed in front of it; the measurements were 

 then made. 



The bird was afterwards, and while still frozen, hung up in the same way 

 in Mr. Smillie's photographic room, and exposures made by him in both posi- 

 tions. These photographs, E, and F, were enlarged to natural size, and meas- 

 urements made on the enlargements yielded, as nearly as could be determined, 

 the same results as when taken directly upon the bird. 



As determined by measurements upon the buzzard in soaring position, the 

 center of gravity was found to be 2.65 inches below the center of pressure (esti- 

 mating the center of pressure to be at the bend of the wing) ; or, employing the 

 compo-board pattern in a corresponding position, the distance was seen to be a 

 small fraction of an inch less. 



7. The position of the root of the wing.— This is indicated on the tracing .1,. 

 a. (Depth of the body on a vertical line with root, 3.5 inches.) The root lies 



1.6 inches below dorsal Hue, 1.9 inches above ventral line. 



h. (Length of body, 26 inches.) The root lies 7.6 inches behind tip of beak. 

 18.4 inches in front of tip of tail. 



8. The dihedral angle between the wings— The photographs taken previ- 

 ously were not sufficiently large or distinct to enable us to determine this with 

 exactness. It was estimated, however, as 150°, and experiments were made on 

 this basis. 



!i. The center of gravity of tin' dissected icing.— This was found, first, for 

 the win- having all the muscles, up to the ball and socket joint, intact. One of 

 the wings was frozen in the soaring position and its center of gravity found by 

 balancing on a point. Its position was marked by a wire thrust through the 

 win- at this place, and the win- (//) is preserved in formalin. This position 

 is also marked on ;i special tracing, /. Tt lies 6 indies from the base of the 

 humerus bone (root of wing). Secondly, it was found for the wing denuded of 

 all muscle. Its position was marked on the other win- of the bird, which is pre- 



ed dry, spread in the soaring position. It lies 9| inches from the base of the 

 humerus. 



