260 DR. PETTIGREW ON THE MECHANISM OF FLIGHT. 



Lng, the effect of which is to project them along a series of parabolic curves. The Snipe 

 (Plate XI \ . fig. 36) and Woodcock are irregular in another respect, their flight being 



sudden, jerky, and from side to side. 



Ilotle of usee tiding, descending, turning, Sfc. — All birds which do not, like the Swallow 

 and Hamming-birds, drop from a height, raise themselves at first by a vigorous leap 

 (Plate X f V. fig. 43), in which they incline their bodies in an upward direction (Plate XIV. 

 figs'. 32, 35, and 42), the height thus attained enabling them to extend and depress their 

 wings without injury to the feathers. By a few sweeping strokes delivered downwards and 

 forwards, in which the wings are made nearly to meet above (Plate XIV. fig. 43) and below 

 ( Plate X 1 V. fig. 41) the body, they lever themselves upwards and forwards, and in a surpri- 

 singly short space of time acquire that degree of momentum which greatly assists them in 

 t beir future career*. In rising from the ground, as may readily be seen in the Crow, Pi- 

 eon, and Kingfisher (Diagram 17, p. 252), the tail is expanded and the neck stretched out, 

 10 that the body is converted iuto an inclined plane and acts mechanically as a glider. 

 Che centre of gravity and the position of the body are changed at the will of the animal 

 by the play of the wings, aided by the long flexible neck, feet, and tail: and when it 



Wishes merely to progress, it assumes a more or less horizontal position, well seen in the 

 Wild Duck in full flight (Diagram 4, p. 210). When the bird has elevated itself to the de- 

 snv.l height, the length of the down ward stroke is generally curtailed, the mere extension 

 and flexion of the wing, assisted by the weight of the body, in some cases sufficing for the 



* It kjht, MomenH.m, and Power, to a certain extent mjnonymmu in Jlight.-Wheu a bird rises it has little or 



no momentum, so that if it came in eontact with a solid resisting surface it would not injure itself. When, how 



c r ,t has acqmml all the momentum of which it is capable, and i. in full and rapid flight, such contact 



remits u, destruction. My friend Mr. A. D. Bartlett informed me of an instance where a wild duck terminated 



ns career b, eommg vmlemly in eontact with one of the glasses of the Eddvstone lighthouse. The glass, which 

 bir ! "', "■ '" , " K \ WaS COmP ' etely SmaSheC '- Adva " ta -« is take " ° f «* circumstance in killing sea- 



, I, Z " S ' C :, °" ;, b ° ard ^ " aflMt ™ th a *• «• >™K»g the neck of A, bird when it toop, 



4: i r u o! ; nn ; h h T n these the "*■ ab ii is **** «■"«* -«««« » *» ^ <* 



tiie vessel iuc!ea>r>, the strength of a man \f «v.„r i i i r 



beimr nffld.nl to r ,„ I . T P1 y S " aWser MM[kA t0 the ste ™ °f » moderate-sized vessel, 



e ;,7! 1 , V™ '" S ° me "' StanCe3 ' |,re ™" itS S ' arti °=- *> «* • case the power of the engine i 

 „; , ,: ULIl^r" * "" « 1 » •«* *. -ew or paddle is Lersed. 



IS 



It is conse- 



quently not flip nnwpr rociJin. i *i 1 » U1CW or P aaai e is immersed. It is conse- 



adroitly convening H into an L^^Z^ ti! i^ (P "" e ^ ^ * "" a " d ^ "T 

 prolonged flight of birds is mainly ^ the ^ J ^wei » ? ££~T TJ «" «* — ** <"< 

 wm , an so relieving the e,cc s3 of exertion which would JLj ^Tttti^ ^ 



which in hvino- atriirtnrpa rp,id oc U fi • * UI1 ine 0lra - At is th 



the action of the 

 thus that the power 



lis reci- 



which in livin,, st n,«ure, resides in the mass i. conserved ,„d 7h .1 ' " " """ """ *" 



proci.,, no bird c„„,d retain fa position in ,be ai f r 1 t n ,T ^ T^ " ~' ^ *» * , 

 comparativelv brief upward flight of the Lark and the Z^T ( ^ Z"IT "^ ^ '" ^ " 

 •he body is exclusivclv sustained bv the action of tie win,, ,1 -v. , hUn "" S - In b ° th theSe ^ 



*. « of the b„,,;- does „„t co-utrilnl o Z£Z2££* °T ^ ^ S ™ ""' " " ; ^ ° ther "* 



In the fli,bt of the Albatros. „„ ,1,„ „„,„ ,.„...f . . ' g " S mom cntum and the impulse which momentum begels. 



for the most 



igh« of the Albatros, „„ tn . „ ther ^ ^ ^Z^ZZ 7 ^^ ™ mCnt '" n ^ 



nnst part bdog rin.pl, rotated on and off the »!„/!„* PnnC ' P r™ "' "" "^ ' he m " gS 



mass t „ operate npon. It „p |)M r S to me that in this blendh. of acti e JJT "" ^ """^ ** "" JT2 " 

 »rap|„ ,1 „p, and tllat „„ arr „ 6 « »ctne and passrve power the mystery of fhgbt a 



the p, .ciple here pointed out. ' 8 fl ' S '" a " inciall - T whi d> doe. not recognize and apply 



