a, b, vessel, lower part filled with water; sl, ray of light in straight line; rps, ray of light refracted; Pencil of Rays, p. 964. A, A, primaries; B, B, tertials; C, C, lesser coverts: D,D, greater coverts; E. E, bastard wing: F, F scapulars; G, upper tail coverts; H. under tail coverts; I, tail feathers. |