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Published online by Cambridge University Press: 08 May 2017
Note on Page 41 * Untersuchungen über den Flug der Vögel , 8vo. Vienna, 1846
Note on Page 44 * The late Mr. Espy suggested that the phenomenon of sailing in the flight of birds is due to upward currents of air which take place in warm weather, or beneath clouds, and especially up the side of a mountain against which the wind is blowing.—J. H.
Note on Page 46 * Archives Neérlandaises, t. iv. 1869.