Ficcent Liteyulurc. 



419 



iSSS.* This important paper, the special subject ot' the present review, 

 has three main heads : — i. It discusses the general problem of flight, and 

 especially of soaring flight, taking the usual position, that the mechanics 

 of soaring are referable to those of the paper kite, in which the figure of 

 the bird compares to the body of the kite, and its weight to the resistance 

 of the string of the kite. This proposition was very fully discussed and 

 illustrated in an unknown paper by an unknown man, thirty years ago. 

 2. A concise description of the eighteen known muscles of the forearm 

 and manus of birds, and their eftect in moving the parts upon which they 

 lie.t — 3. The special consideration of the emargination of the primaries, 

 forming the body of the paper. This matter is so interesting, not onlv in 

 reference to the ' interlocking' theory, but in its general bearing, that we 

 transcribe it in full for the readers of The Auk,' who will no doubt agree 

 with us as to its entire soundness : 



"It has been intimated that the emargination in the primaries of hawks 

 and other soaring birds gives evidence of interlocking, being apparently 

 a provision for this purpose. That it has suggested the theory of inter- 

 locking is quite evident, but it has no further bearing on the subject. That 

 it is not distinctively characteristic of soaring birds has been abundantly 

 shown. The purpose of this structure evidently varies in different birds. 



" In some birds, as the woodcock, various genera of pigeons, fly- 

 catchers, and humming-birds, the falcate tips of the outer primaries give 

 rise to musical sounds, of somewhat varying character in difterent species. 

 due to the rapidity and angle with which they strike the air in rapid flight, 

 the emission of the sound being voluntary on the part of the bird, and 

 often forming a part of its amatory demonstrations, as does song or certain 

 peculiar notes in many song-birds. In herons, many water-birds, hawks, 

 eagles, owls, vultures, etc., it is apparently the elimination of a part of 

 the vane which, if present, would prove only an impediment and an ob- 

 struction in flight. The emargination extends, it will be observed, from 

 the point where, in the fully e.vtended wing, the inner vane fails to fill the 

 entire space between two contiguous quills. The vane becomes verv 

 weak and flexible along its edge, and requires the support of the overly- 

 ing feather to keep it smooth and intact, so that were the vane to retain 

 its full width to the tip of the feather, on which the air impinges with the 

 greatest force in flight, it would have no support from the contiguous 

 feather, and would be too weak to resist the air; it would consequently be 

 more or less rolled upward at its free edge and prevent the free closing of 

 the tips of the leathers; it would not be firm enough to give much sus- 

 taining power, would be in the way, and become folded and rumpled in 

 the closing of the wing. Therefore just that useless and obstructive 



* Allen, j..\., " On the Structure of Birds in Relation to Flight, with Special Reference 

 to Recent .\lleged Discoveries in the Mechanism of the Wing," Trans. N. Y. Acad. 

 Sci., Dec. 1887-Mar. 1888, pp. 89-100. 



t Davidson, R. O., "'A New Theory ot the Flight of Birds," 8vo., paper. Washing, 

 ton, 1858, pp. 28. plate. 



X See paper in present Auk, p. 435. 



