232 DR. PETTIGREW ON THE MECHANISM OF FLIGHT. 



The spiral nature of the pinion is most readily recognized when the wing is seen 

 from behind and from beneath (Plate XV. figs. 68, 69, 70, 73, and 74), and when it is 

 foreshortened, as has been done in figures 61 and 62, Plate XV. It is also well marked 

 in some of the long-winged oceanic birds when viewed from before (Diag. 18 a, a b\ d' e'f, 

 p. 253), and cannot escape detection, under any circumstances, if sought for, — the win<* 

 being essentially composed of a congeries of curves, remarkable alike for their apparent 

 simplicity and the subtlety of their detail. The twisting or rotating of the wing on its 

 long axis is particularly observable during extension and flexion in the bat and bird, and 

 likewise in the insect, especiaUy the Beetles, Cockroaches, and others which fold their 



Modes of 



The lecture in 



question was fixed for March 1867, and was published in the Proceedings of the Institution under date the 22nd of 

 March, 1867. At pages 99, 100, and 101 of the Proceedings, the spiral conformation of the wing in the insect and bird 

 is adverted to at length, it being there described as a twisted lever or helix, which owes its peculiar elevating- and pro- 

 pelhng-power in a great measure to its shape. Particular emphasis is also placed upon the partial rotation of the wing 

 on its long ax 13 during extension and flexion, and to its screwing and unscrewing action during the down and up strokes, 

 tins being a sine qua non in flight. In the pages alluded to, the subjoined passages occur :_« All wings obtain their lever- 



forwards 



of obliquity gradually increasing in a direction f 



— ~™ *» *^xii£ given, unu uruuuutii/ aecreas- 



,n„ * an ,«„ teta dunng flexion, or when the wing is being m ore slowly recovered preparatory to making 

 a second stroke. The effect™ stroke in insects-and this holds trne also of birds-is therefore delivered do mw al 



and forwards, and not, as the majority of writers IipKpvp ™*^aii« — - i- l a i , , . .. * 



* * * * tc rp 



intersecting each other, 

 twisted udo 



confer on the wing the multiplicity of movement which it requires, it is supplied with a double hinge or compound 



2 n^e 7 f° n ° Ve ?. 7l " " UPWard ' d ° WnWard ' f ° mard ' and backward directi -> ** ^so at Lous 



2 m or 1 IT -° ; . ^ ^ „ 1 " ThC Wb§ ° f thC bifd ' ^ that ° f the ™«> is concavo-convex, 



and more or less twisted upon itself when extended, so that the upper or thick margin of the pinion presents a dif- 

 ferent degree of curvature to that of the nether or thin margin-the curves of the J™, i ■ 



intersecting eae.h ntW This twistin- is in a W9 f • 7 rg,nS m S ° me 1HStanCeS mn 



i his twisting is m a great measure owing to the manner in which the bones of the wing are 



ing each other at nearlv^ht l P T™ °[ *? I**" ""**"- the h ^ axes of the J** always intersect- 

 ing each other at neaily nght angles. As a result of this disposition of the articular surfaces the win* may be shot 

 out or extended, and retracted or flexed in nearlv th P « n ™ n u *u v places, me win e may be shot 



o™ a • -.u ™ . 7 me P lane ' the bones compos ng the win" rotating on their 



axes during either movement. Th is secondarv apiinn ^fU i • , , 8 ° rotdun o on ineir 



,. n t ,i * * • • . ^onaary action, or the revolving of the component bones uoon their own axes 



is of the greatest importance in the movements of th* ™ nn * •* • P 



seonently to the primary and secondary TZ.I^Z'^ ^"""^ T ** *** "* ^^ ^ C ° a ' 



ensnres that the wing, and the cnrtain or fringe of the £ 2^L > T" " ^ " " ** 



— in, an* *«. vm Me +* in e X te sion, llJ2^ 1^ ZL^IT^ ^ !"f *" Jf 



win 



of the wing; the flanges or spiral thread of the gimlet the nrim V S 



it ™li K* «r,A * *t A , gimlet the primary and secondarv feathers 



t w, 1 be ev.dent that by the nrere rotation of ,he bones of the forearm and hand h 

 est ance . seenred tnnch in the same way that this object is attained h th Taul at 



or auger, the axis of the gimlet representing the bones 



From this description 

 and hand, the maximum and minimum of 



ypmg and feathering of 



manner in which the 



Kaufma 



I have introduced the above quotations from a belief that un fn fU i t * t.- . 



e 22nd of March, 1867, the twisted configuration of he ni , ^ ^ IeCtU ™ ™ S published ' * 



wing rotates on its lo°ng " 12" Zt Z T™ ""** *** °™ d * * 



, „ Glasgow, patented a fl ^ng-maclun °n ti chT ' 1 ^ ^ ^ Mf ' ^ 



more or less accurately reproduced, no allusion L^^^tJ^ ^T' ° ^ ^ ^'^ ^ ^ *" 

 quest I forwarded a copy of my paper to him in March ISfiT 1 7 "* ' aUh ° Ugh Rt Mr * KaufraaDn ' s re " 



That Mr. Kaufmann was unacquainted with the mov L , * """^ **" * ^ '^ ° Ut his P atent ' 



having been made to them in his preliminarv sn^fi 7 "' qUeStl ° n Wi " Eppear fr0m the fact of no reference 



Arable importance is attached to them in hh JtuT !Z "\ V™^™ ^^ in Febmar y 1867 ' whiIe ^ con ' 



his actual patent taken out in August 1867. [Feb. 20, 1868 ] 

































