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 suspended 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 positions. These photographs, E1 and F1 were enlarged to natural size, and measurements 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 (estimating 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 A1.
a. (Depth of the body on a vertical line with root, 3.5 inches.) The root lies 1.6 inches below dorsal line, 1.9 inches above ventral line.
b. (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 previously 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.
9. The center of gravity of the dissected wing.—This was found, first, for the wing 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 wing at this place, and the wing (H) is preserved in formalin. This position is also marked on a special tracing, I. It lies 6 inches 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 wing of the bird, which is preserved dry, spread in the soaring position. It lies 934 inches from the base of the humerus. [p291]
10. The weight of the dissected wing.—
a. With all muscle up to the ball and socket joint intact, 325 grammes.