. Annual report of the Board of Regents of the Smithsonian Institution. Smithsonian Institution; Smithsonian Institution. Archives; Discoveries in science. THE EMPIRE OF THE AIR. 441 aliuht without hrojikiiij;' their leg-s. It is <'U'ai' however that tkey are lianipered by this excess ofsiirtace; not one of them is remarkable as a Hyer, neither as to velocity—which is easily ex|)laiiie(l, noi- even as a permanent denizen of the air—which is more extiaordinary. They are in foct so well eqniitjsed for sailing,' on li'ht winds that the surlace resistance destroys all the other qnalities when t
. Annual report of the Board of Regents of the Smithsonian Institution. Smithsonian Institution; Smithsonian Institution. Archives; Discoveries in science. THE EMPIRE OF THE AIR. 441 aliuht without hrojikiiij;' their leg-s. It is <'U'ai' however that tkey are lianipered by this excess ofsiirtace; not one of them is remarkable as a Hyer, neither as to velocity—which is easily ex|)laiiie(l, noi- even as a permanent denizen of the air—which is more extiaordinary. They are in foct so well eqniitjsed for sailing,' on li'ht winds that the surlace resistance destroys all the other qnalities when the breeze fresliens. It is only when the weight becomes 4 ponnds or more that tlie mass momentum succeeds in overcoming the fri(;tion of the air against these over-feathered wings. The birds first named in the table Hy as unsteadily as the butterfly; the hoopoe, the armed plover, and the laj^wiug can advance against strong winds only by comj)letely folding- their wings. This deflciency diminishes with the increase in weight. The ibis flies better than the small heron, and both are distanced bv the Kui. <i.—TliK urcy Horon. We tind proof in this type tluit the useful, active surface of the wing lies in the hand and the forearm, and that the arm remains almost quiescent in flapping. The demonstration is i)al]table, as is ever the case in nature. The feathers of the humerus have been simply sup- pressed in most of the herons, and only those of the covert remain, which latter feathers aic merely ornamental. Tite Ix-cslrcJ Falcon.—The kestrel is common in France. It inhabits our large cities. It is known by all observers, and they doubtk'ss have gathered their best knowledge from its evolutions. Its strength is great and it always rows when hunting; but when there comes a change of weather and the soutli wind sets in, then the creature climbs u|) soaring into the sky and exhibits its talents as a sailing bird, which talents are fully as great as might be expected
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