THE EMPIKK OK llli; A IK'. 405 



J'luiii llu' l)ii'(rs pijilit of \ i«'\\ . I lie sumll arc lt(\s( ('iidowcd; hiil tlicir 

 power, skill, and life, man can not r(^-pi()du(('. If he is destined ever to 

 cleave the a/nro, he must seek liis model more nearly of his size. 



Varieties iti forms of irinf/s. — Ornitholojuists ha^'e divided tlu^ <lititer- 

 ent forms of winjis into two groups: thr aente wings and the obtusi' 

 wings; then again these are sub-dividccl into the suix'r-acute ami sub- 

 acute, the .super-obtuse and sub-obtuse. 



This elassitication, however ex<*«'llent it may be, is not sullicienr. 

 In order to explain satisfactorily the numerous facts obserxcd couccrn- 

 iug flight, we must have more data than are furnished by these divi- 

 sions, which are too vague and general. Wenuisttake account of the 

 amount of wing surface, in ])roportion to weiglit, of tlu^ length of the 

 wing in relation to its width, and to tlie mass of the bird; in fact we 

 must consider many circumstances, whi(;h render it necessary to study 

 each family l)y itself, in order to reach satistactory conclusions. 



As a result of the study of all these conditions — a study to be found 

 farther on, — \\v may now establish a series of principal divisions, 

 which may be condensed under the rennirks following. 



It may be safely ailiiined: that a bird with long and wide wings is 

 well (Mpiipped for soaring flight. A gift which go<»son increasing with 

 the mass; that the bird with hnig and narrow wings is well equippe<l 

 for gliding in great wimls, and that this gift also increases with the 

 nmss; that short and wide wings (in jn-oportion to body) indicate and 

 ]>roduce a II ight of small extent: tinally that short and narrow wings 

 denote great rectilin<^ar speed. We may even lay down the law: 

 Velocity is in inverse ratio to wing surface. 



This, be it uinlerstood, ap]dies to birds whii-h lly, for else tin; ostrich 

 and the ai)teryx would be the most rapid of l)irds: but we may say that 

 among flying birds velocity, straitlbrward, increases as the propor- 

 tional surface diminishes. It must be so to sustain the increased rela- 

 tive weight. iMcry sportsman know^s the astonishing sixH'd of ducks, 

 teals, loons, <'tc., and the slowness of herons, lai» wings, and barn owls. 



It is useless to enlarge upon these fundamental ])rincii)les, for we 

 shall lind them C(mstantly explained and ap])lied in our studies of the 

 flight of each feathered family. 



The tail of birds. — The tail, as an apparatus, serves to sustain, to 

 direct, and to i)reserve the ecpiilibrium. - - - It is a useful organ, 

 but not indispensable. A bird who has been deprived of its tail will 

 fly, Avith its own i)articular mode of llight, alter some days' ])ractice, 

 ami without much varian(;e or (hlliculty. - Many birds wliich 



are exi)ert flyers have scarcely any tail: the lienms. tlie albatross, the 

 ducks, the teals, the pelicans, the gulls, etc., etc. 



Again, the tail may be larg<^ or snmll without api)arent reason. As 

 witness the turtle-dove ami the Iigyi)tian <love, the magpie ami the 

 jay, the vulture an<l the tumbh'r eagle. 



