atmospheric strata from ten to eighteen thousand (about 10600 to 19000 English) feet above the level of the sea. Humming birds, which make summer excursions as far as 61° N. latitude on the north-west coast of America on the one hand, and the Tierra del Fuego on the other, have been seen by Von Tschudi (Fauna Peruana, Ornithol. p. 12) in Puna as high as 13700 (14600 English) feet. There is a pleasure in comparing the largest and the smallest of the feathered inhabitants of the air. Of the Condors, the largest individuals found in the chain of the Andes round Quito measured, with extended wings, 14 (nearly 15 English) feet, and the smallest 8 (8-1/2 English) feet. From these dimensions, and from the visual angle at which the bird often appeared vertically above our heads, we are enabled to infer the enormous height to which the Condor soars when the sky is serene. A visual angle of 4´, for example, gives a perpendicular height above the eye of 6876 (7330 English) feet. The cave (Machay) of Antisana, which is opposite the mountain of Chussulongo, and from whence we measured the height of the soaring bird, is 14958 (15942 English) feet above the surface of the Pacific, This would give the absolute height attained by the Condor at fully 21834 (23270 English) feet; an elevation at which the barometer would hardly reach 12 French inches, but which yet does not surpass the highest summits of the Himalaya. It is a remarkable physiological phenomenon, that the same bird, which can fly round in circles for hours in regions of an atmosphere so rarified, should sometimes suddenly descend, as on the western declivity of the Volcano of Pichincha, to
