; ¢ Mg os ff ett ae Yat peer a pS eup J ae a ety acs aes r NOT z = by aN SAP ied 2 A Se Ae in \ Wyss fh, Ly hie WY Ait 2 Lp UY W eg Vy f 7 LM 4 j VG Ls Wy fd Vig ZB Y Hy as = GEMM J pg Warkine, Swine, AND Fryrya. UT 40 | > THE INTERNATIONAL SCIENTIFIC SERIES, vv. 7. ANIMAL LOCOMOTION we WALKING, SWIMM ING, AND FLYIN G, OR WITH A DISSERTATION ON SPRONAUTICS..° .. BY : € a J. BELL PETTIGREW, M.D. ERS. ERSE. RRGP.E. PATHOLOGIST TO TEE ROYAL INFIRMARY OF EDINBURGH ; CURATOR OF THE MUSEUM OF THE ROYAL COLLEGE OF SURGEONS OF EDINBURGH , Extraordinary Member and late President of the Royal Medical Society of Edinburgh; Croonian Lecturer to the Royal Society of London for 1860; Lecturer to the Royal Institution of Great Britain and Russell Institution, 1867; Lecturer to the Rvyal College of Surgeons of Edinburgh, 1872 ; Author of numerous Memoirs on Physiological Subjects in the Philosophical and other Transactions, etc. etc. etc. (ULUSTRATED BY 130 EN GRAVINGS ON WOOD. NEW YORK: = APPLETON & COMPANY, 549 & 551 BROADWAY. 1874, SS JUL 22 1913 , ‘gonian | MStibagp *. PREFACE. _In the present volume I have endeavoured to explain, in simple language, some difficult problems in “Animal — Mechanics.” In order to avoid elaborate descriptions, I have introduced a large number of original Drawings and Diagrams, copied for the most part from my Papers and Memoirs “On Flight,’ and other forms of “ Animal Progression.” I have drawn from the same sources } many of the facts to be found in the present work. My best thanks are due to Mr. W. Ballingall, of Edinburgh, for the highly artistic and effective manner in which he has engraved the several subjects: The figures, I am happy to. state, have in no way deteriorated in his ~ hands. : eee, { Roya CoLLEGE OF SURGEONS OF EDINBURGH, July 1873. » CONTENTS. ANIMAL LOCOMOTION. INTRODUCTION. Motion associated with the life and well-being of animals, Motion not confined to the animal kingdom; all matter in motion; natural and artificial motion; the locomotive, steamboat, etc. OGRESSION IN OR THROUGH THE AIR. ifo pinions. It is corrected in some. by curving the body, in others by bending or straightening the limbs and antenne, but principally in all by the judicious play of the wings themselves. The wing of the bat and bird, like that of the insect, is eoncavo-convex, and more or less twisted upon itself (figs. 94,95, 96, and 97). Fie. 95. Fic. 94.—Right wing of the Bat (Phyllorhina gracilis), dorsal surface. def, Anterior or thick margin of the wing, supported by the bones of the arm, forearm, and hand (first and second phalanges); cab, posterior or thin margin, supported by the remaining phalanges, by the side of the body, and by the foot. — Original. Fic. 95.—Right wing of the Bat (Phyllorhina gracilis), as seen from behind and from beneath. When so regarded, the anterior or thick margin (d f) of the Wing displays different curves from those seen on the posterior or thin mar- gin (bc); the anterior and posterior margins being arranged in different planes, as in the blade of a screw propeller.—Original. The twisting is in a great measure owing to the manner in which the bones of the wing are twisted upon themselves, and the spiral nature of their articular surfaces ; the long axes of the joints always intersecting each other at nearly right angles. As a result of this disposition of the articular surfaces, the wing is shot out or extended, and retracted or flexed in a variable plane, the bones of the wing rotating in the direction of their length during either movement. This secondary action, or the revolving of the component bones upon their own axes, is of the greatest importance in the movements of the wing, as it communicates to the hand and forearm, and 176 ANIMAL LOCOMOTION. consequently to the membrane or feathers which they bear, the precise angles necessary for flight. It, in fact, imsures that the wing, and the curtain, sail, or fringe of the wing shall be screwed into and down upon the air in _ extension, and unscrewed or withdrawn from it during flexion. The wing of the bat and bird may therefore be compared to a huge gimlet or auger, the axis of the gimlet representing the bones of the wing; the flanges or spiral thread of the gimlet the frenum or sail (figs. 95 and 97). Fre. 97, Fic. 96.—Right wing of the Red-legged Partridge (Perdix rubra), dorsal aspect. Shows extreme example of short rounded wing; contrast with the - wing of the albatross (fig. 62, p. 137), which furnishes an extreme example of the long ribbon-shaped wing; def, anterior margin; bac, posterior ditto, consisting of primary (b), secondary (a), and tertiary (c) feathers, with their respective coverts and subcoverts; the whole overlapping and mutually supporting each other. This wing, like the kestrel’s (fig. 61, p. 136), was drawn from a specimen held against the light, the object being to display the mutual relation of the feathers to each other, and how the feathers overlap.—Original. Fic. 97.—Right wing of Red-legged Partridge (Perdix rubra), seen from be- hind and from beneath, asin the beetle (fig. 93) and bat (fig. 95). The same lettering and explanation does for all three.—Original. THE WINGS OF BATS. The Bones of the Wing of the Bat—the spiral configuration of their articular surfaces.—The bones of the arm and hand are especially deserving of attention. The humerus (fig. 17,7, p. 36) 1s short and powerful, and twisted upon itself to the extent of something less than a quarter of a turn. | i “ P ‘ PROGRESSION IN OR THROUGH THE AIR. Lie As a consequence, the long axis of the shoulder-joint is nearly at right angles to that of the elbow-joint. Similar remarks may be made regarding the radius (the principal bone of the forearm) (d), and the second and third metacarpal bones with their phalanges (¢ f), all of which are greatly elongated, and give strength and rigidity to the anterior or thick margin of the wing. The articular surfaces of the bones alluded to, as well as of the other bones of the hand, are spirally disposed with reference to each other, the long axes of the joints intersecting at nearly right angles. The object of this arrangement is particularly evident when the wing of the living bat, or of one recently dead, is extended and flexed as in flight. In the flexed state the wing is greatly reduced in size, its under surface being nearly parallel with the plane of progres- sion. When the wing is fully extended its under surface makes a certain angle with the horizon, the wing being then in a position to give the down stroke, which is delivered downwards and forwards, as in the insect. When extension takes place the elbow-joint is depressed and carried forwards, the wrist elevated and carried backwards, the metacarpo- phalangeal joints lowered and inclined forwards, and the distal phalangeal joints slightly raised and carried backwards. The movement of the bat’s wing in extension is consequently a spiral one; the spiral running alternately from below up- wards and forwards, and from above downwards and back- wards (compare with fig. 79, p. 147). As the bones of the arm, forearm, and hand rotate on their axes during the exten- sile act, it follows that the posterior or thin margin of the wing is rotated in a downward direction (the anterior or thick one being rotated in an opposite direction) until the wing makes an angle of something like 30° with the horizon, which, as I have already endeavoured to show, is the greatest angle made by the wing in flight. The action of the bat’s wing at the shoulder is particularly free, partly because the shoulder-joint is universal in its nature, and partly because the scapula participates in‘ the movements of this region. The freedom of action referred to enables the bat not only to rotate and twist its wing as a whole, with a view to dimin- —— 9 178 ANIMAL LOCOMOTION. - ishing and increasing the angle which its under surface makes with the horizon, but to elevate and depress the wing, and. move it in a forward and backward direction. The rotatory or twisting movement of the wing is an essential feature in flight, as it enables the bat (and this holds true also of the insect and bird) to balance itself with the utmost exactitude, and to change its position and centre of gravity with mar- vellous dexterity. The movements of the shoulder-joint are restrained within certain limits by a system of check-ligaments, and by the coracoid and acromian processes of the scapula. The wing is recovered or flexed by the action of elastic liga- ments which extend between the shoulder, elbow, and wrist. Certain elastic and fibrous structures situated ‘between the fingers and in the substance of the wing generally take part in flexion. The bat flies with great ease and for lengthened periods. Its flight is remarkable for its softness, in which respect it surpasses the owl and the other nocturnal birds. The action of the wing of the bat, and the movements of its component bones, are essentially the same as in the bird. THE WINGS OF BIRDS. The Bones of the Wing of the Bird—their Articular Sur- faces, Movements, etc.—The humerus, or arm-bone of the wing, is supported by three of the trunk-bones, viz. the scapula or shoulder-blade, the clavicle or collar-bone, also called the furculum,! and the coracoid bone,—these three converging to form a point dappui, or centre of support for the head of the humerus, which is received in faceties or depressions situated on the scapula and coracoid. In order that the wing may have an almost unlimited range of motion, and be wielded after the manner of a flail, it 1s articulated to. the trunk by a somewhat lax universal joint, which permits 1 The furcula are usually united to the anterior part of the sternum by ligament; but in birds of powerful flight, where the wings are habitually extended for gliding and sailing, as in the frigate-bird, the union is osseous in its nature. ‘‘In the frigate-bird the furcula are likewise anchylosed with the coracoid bones.”—Comp. Anat. and Phys. of Vertebrates, by Prof. Owen, vol. ii. p. 66. ee PROGRESSION IN OR THROUGH THE AIR. 179 vertical, horizontal, and intermediate movements. The long axis of the joint is directed vertically; the joint itself some- what backwards. It is otherwise with the elbow-joint, which is turned forwards, and has its long axis directed horizontally, from the fact that the humerus is twisted upon itself to the extent of nearly a quarter of a turn. The elbow-joint is decidedly spiral in its nature, its long axis intersecting that of the shoulder-joint at nearly right angles. The humerus articulates at the elbow with ae bones, the radius and the ulna, the former of which is pushed from the humerus, while the other is drawn towards it during extension, the reverse occurring during flexion. Both bones, moreover, while those movements are taking place, revolve to a greater or less extent upon their own axes. The bones of the forearm articulate at the wrist with the carpal bones, which being spirally arranged, and placed obliquely between them and the metacarpal bones, transmit the motions to the latter in a curved direction. The long axis of the wrist-joint is, as nearly as may be, at right angles to that of the elbow-joint, and more or less parallel with that of the shoulder. The metacarpal or hand-bones, and the phalanges or finger-bones are more or less fused together, the better to support the great primary feathers, on the efficiency of which flight mainly depends. They are articulated to each other by double hinge-joints, the long axes of which are nearly at right angles to each other. . As a result of this disposition of the articular surfaces, the wing is shot out or extended and retracted or flexed in a variable plane, the bones composing the wing, particularly those of the forearm, rotating on their axes during either movement. This secondary action, or the revolving of the component bones upon their own axes, is of the greatest importance in the movements of the wing, as it communicates to the hand 1 “The os humeri, or bone of the arm, is articulated by a small rounded surface to a corresponding cavity formed between the coracoid bone and the scapula, in such a manner as to allow great freedom of motion.” —Macgillivray’s Brit. Birds, vol. i. p. 33. “The arm is articulated to the trunk by a ball-and-socket joint, permitting all the freedom of motion necessary for flight.”—Cyc. of Anat. and Phys., vol. iii. p. 424. 180 ANIMAL LOCOMOTION. and forearm, and consequently to the primary and secondary feathers which they bear, the precise angles necessary for flight ; 1t in fact insures that the wing, and the curtain or fringe of the wing which the primary and secondary feathers form, shall be screwed into and down upon the air in ex- tension, and unscrewed or withdrawn from it during flexion. The wing of the bird may therefore be compared to a huge. gimlet or auger; the axis of the gimlet representing the bones of the wing, the flanges or spiral thread of the gimlet — the primary and secondary feathers (fig. 63, p. 138, and fig. OY, Pp. 10). Traces of Design in the Wing of the Bird—the sirrciagnetiie of the Primary, Secondary, and Tertiary Feathers, etc—There are few things m nature more admirably constructed than the wing of the bird, and perhaps none where design can be more readily traced. Its great strength and extreme lightness, the manner in which it closes up or folds during flexion, and opens out or expands during extension, as well as the manner in which the feathers are strung together and overlap each other in divers directions to produce at one time a solid resisting surface, and at another an interrupted and compara- tively non-resisting one, present a degree of fitness to which the mind must necessarily revert with pleasure. If the feathers of the wing only are contemplated, they may be con- veniently divided 7 three sets of three each (on both sides of the wing)—an upper or dorsal set (fig. 61, d,¢,f, p. 136), a lower or ventral set (¢,a,b), and one which is intermediate. This division is intended to refer the feathers to the bones of the arm, forearm, and hand, but is more or less arbitrary in its nature. The lower set or tier consists of the primary (0), secondary (a), and tertiary (c) feathers, strung together by fibrous structures in such a way that they move in an out- ward or inward direction, or turn upon their axes, at precisely the same instant of time,—the middle and upper sets of feathers, which overlap the primary, secondary, and tertiary ones, constituting what are called the “coverts” and “ sub- coverts.” The primary or rowing feathers are the longest and strongest (>), the secondaries (a) next, and the tertiaries third (c). The tertiaries, however, are occasionally longer than the 181 twards, i.c. from the body IM ou The tertiary, secondary, and primary feathers ‘PROGRESSION IN OR THROUGH THE AIR. trength from with secondaries. increase in. s MUIDIUO— NOT “SY JO w “w ye WES OSTR BIB SOSSod -oid osoyy, ‘(f(a “p) FUSIT 0} JJoT WOTZ UOTZOOIIP v UT ToqYZO oY] “(ny ‘q 69) Jo OF FUSLI WLOIJ WOLZD9IIpP B UL (x) Ioyyeoy yore JO JOOI oY} puNos SoAIND YOIYM JO auto ‘sassadoid omy oyur dn sqiqds (m ‘2) pueq [RUIpNyISUOCT [RUISIVUI OU, ‘SLoyyvoy Om} ATOAD U9IMJoq SuLLINIIO SpuRq onhbipqo ey} : uns ‘y pue 6 ‘spueq onbijqo oM4 spueq osey} UsdMyJoq “mM ‘a ‘N18 L ‘SpuUBq [BUIPNYLSUOT 9914} JO S]SISMOD PUB ‘TOT PUL GG "SOY 4B postelus SI JY “WOTJOR IBTMATBA AvI[NOId ILO} SHUITT pure ‘siayyvos oy} Sjtoddns uorsonb Ul yIOMAOU oY], “Lol[}vaJ [RNPIATPUL Tove JO JOOL oY edofeaus 07 sv IOUULUL B YONS Ul postive Suloq s}red yuauodutos sy ‘Aynvaq pu YYSUII]S YvoIs JO YLOMJoU TVOLAZOUMLULAS B SUULIOT pue ‘sxeyyvey Arepuooss puv Areultd oy Jo sjoor oy} sodvpaaus YoryM “GUeTRSI, O14Se[a-O1qy-oTMosny ‘bd ‘d ‘o (q ‘”) saptosnut Areyun -[OA 94} JO VOUINGUL YY JOPUN SST IO VIOUL ST GOM OTYSVIO-OLQY OT, “Wav oY} WO ULIvaIOT OY} XO 04 ‘9 Qa OIYSVTO -O1QY 7918 oY} ‘YIM UoTPOUN[UOd UL Yo puB ‘oq poqtUN ale spueq sa1qy sseyy, “f4e WaaS SI PUL IeTIWITS YY MOUIOS y (wy) suoysod omy oyu dn sqyds puvq siyy, ‘“yY pueq onsepo Ul SulZeULUIIE} SaIqY IeTMoOsnUT AreyuNTOA ‘q 0 ‘OUI OY} Sassoidap TOI oposnur [e1ojooed yvary “(86 “By) & ‘MOT}IPUOD papue4xd9 9} Ul ST SUIM OYJ, “AURIO poqso1d oy Jo SaIM 9yy Jo sqoodse [VIQUAA OY UO SIOyQVOT Arepuooes puv ALVULId oy} JO JUIWASULLIe OY PUB ‘S]UNUILST] OTYSeTa PUB So[OSHUL dy} MOYS TOL pur ‘OOL ‘66 ‘86 ‘SDIA “TOT “SIA ‘OOT “STW ‘66 “SIA 99 I VE uUL™, or) ), 86 ‘OT nd so of the several sets is necessary, because the This arrangement towards the extremity of the wing, a of wing-coverts. 182 - ANIMAL LOCOMOTION. eS strain on the feathers during flight increases in proportion to their distance from the trunk. The manner in which the roots of the primary, secondary, and tertiary feathers are geared to each other in order to rotate in one direction in flexion, and in another and opposite direction in extension, is shown at figs. 98, 99, 100, and 101, p.,181. In flexion the feathers open up and permit the air to pass between them. In extension they flap together and render the wing as air-tight as that of either the insect or bat. The primary, secondary, and tertiary feathers have conse- quently a valvular action. The Wing of the Bird not always opened up to the same extent im the Up Stroke-—The elaborate arrangements and adaptations for increasing the area of the wing, and making it impervious to air during the down stroke, and for decreasing the area and opening up the wing during the up stroke, although necessary to the flight of the heavy-bodied, short-winged birds, as the grouse, partridge, and pheasant, are by no means indispensable to the flight of the long-winged oceanic birds, unless when in the act of rising from a level surface; neither do the short-winged heavy birds require to fold and open up the wing during the up stroke to the same extent in all cases, less folding and opening up being required when the birds fly against a breeze, and when they have got fairly under weigh. All the oceanic birds, even the albatross, require to fold and flap their wings vigorously when they rise from the surface of the water. When, however, they have acquired a certain degree of momentum, and are travelling at a tolerable horizontal speed, they can in a great measure dispense with the opening up of the wing during the up stroke—nay, more, they can in many instances dispense even with flapping. This is particularly the case with the albatross, which (if a tolerably stiff breeze be blowing) can sail about for an hour at a time without once flapping its wings. In this case the wing is wielded in one piece like the insect wing, the bird simply screwing and unscrewing the pinion on and off the wind, and exercising a restraining influence—the breeze doing the principal part of the work. In the bat the wing is jointed as in the bird, and folded during the up stroke. As, PROGRESSION IN OR THROUGH THE AIR. 183 however, the bat’s wing, as has been already stated, 1s covered by a continuous and more or less elastic membrane, it follows that it cannot be opened up to admit of the air passing through it during the up stroke. Flight in the bat is therefore secured by alternately diminishing and increasing the area of the wing during the up and down strokes—the wing rotating upon its root and along its anterior margin, and presenting a variety of kite-like surfaces, during its ascent and descent, pre- cisely as in the bird (fig. 80, p. 149, and fig. 83, p. 158). Fic. 102.—Shows the upward inclination of the body and the flexed condition of the wings (a b, e f; a’ b’, ef ) in the flight of the kingfisher. The body and wings when taken together form a kite. Compare with fig, 59; p. 126, where the wings are fully extended. Hlexion of the Wing necessary to the Flight of Birds.—Con- siderable diversity of opinion exists as to whether birds do or do not flex their wings in flight. The discrepancy is owing . to the great difficulty experienced in analysing animal move- ments, particularly when, as in the case of the wings, they are consecutive and rapid. My own opinion is, that the wings are flexed in flight, but that all wings are not flexed to the same extent, and that what holds true of one wing does not necessarily hold true of another. To see the flexing of the wing properly, the observer should be either immediately above the bird or directly beneath it. If the bird be con- 184 ANIMAL LOCOMOTION. templated from before, behind, or from the side, the up and down strokes of the pinion distract the attention and compli- cate the movement to such an extent as to render the observa- tion of little value. In watching rooks proceeding leisurely ayainst a slight breeze, I have over and over again satisfied myself that the wings are flexed during the up stroke, the mere extension and flexion, with very little of a down stroke, in such instances sufficing for propulsion. I have also observed it in the pigeon in full flight, and likewise in the starling, sparrow, and kingfisher (fig. “102, p. 1s). It occurs principally at the wrist-joint, and gives ‘0 the wing the peculiar quiver or tremor so apparent in rapid flight, and in young birds at feeding-trme. The object to be attained is manifest. By the flexing of the wing in flight, the “remiges,” or rowing feathers, are opened up or thrown out of position, and the air permitted to escape—advantage being thus taken of the peculiar action of the individual feathers and the higher degree of differentiation perceptible in the wing of the bird as compared with that of the bat and insect. In order to corroborate the above opinion, I extended the wings of several birds as in rapid flight, and fixed them in the outspread position by lashing them to light unyielding reeds. In these experiments the shoulder and elbow-joints were left quite free—the wrist or carpal and the metacarpal joints only being bound. I took care, moreover, to interfere as little as possible with the action of the elastic ligament or alar membrane which, in ordinary circumstances, recovers’ or flexes the wing, the reeds being attached for the most part to the primary and secondary feathers. When the wings of a pigeon were so tied up, the bird could not rise, although it made vigorous efforts to do so. When dropped from the hand, it fell violently upon the ground, notwithstanding the strenu- ous exertions which it made with its pinions to save itself. When thrown into the air, it fluttered energetically in its endeavours to reach the dove-cot, which was close at hand ; in every instance, however, it fell, more or less heavily, the distance attained varying with the altitude to which it was projected. Thinking that probably the novelty of the situation and PROGRESSION IN OR THROUGH THE AIR. 185 the strangeness of the appliances confused the bird, I allowed it to walk about and to rest without removing the reeds. I repeated the experiment at intervals, but with no better results. The same phenomena, I may remark, were witnessed in the sparrow ; so that I think there can be no doubt that a cer- tain degree of flexion in the wings is indispensable to the flight of all birds—the amount varying according to the length and form of the pinions, and being greatest in the short broad- winged birds, as the partridge and kingfisher, less in those whose wings are moderately long and narrow, as the gulls, and many of the oceanic birds, and least in the heavy-bodied long and narrow-winged sailing or gliding birds, the best example of which is the albatross. The degree of flexion, moreover, varies according as the bird is rising, falling, or progressing in a horizontal direction, it being greatest in the two former, and least in the latter. It is true that in insects, unless perhaps in those which fold or close the wing during repose, no flexion of the pinion takes place in flight ; but this is no argument against this mode of diminishing the wing-area during the up stroke where the joints exist ; and it is more than probable that when joints are present they are added to augment the power of the wing during its active state, 7.c. during flight, quite as much as to assist in arranging the pinion on the back or side of the body when the wing is passive and the animal is reposing. The flexion of the wing is most obvious when the bird is. exerting itself, and may Te detected in birds which skim or glide when they are rising, or when they are vigorously flap- ping their wings to secure > the impetus necessary to the gliding movement. It is less marked at the elbow-joint than at the wrist; and it may be stated generally that, as. flexion de- creases, the twisting flail-like movement of the wing at the shoulder increases, and vice versd,—the great difference between sailing birds and those which do not sail amounting to this, that in the sailing birds the wing is worked from the shoulder by being alternately rolled on and off the wind, as in insects ; aes, in birds which do not glide, the spiral movement travels along the arm as in bats, and manifests itself during flexion and extension in the bending of the joints and in the 186 - ANIMAL LOCOMOTION. rotation of the bones of the wing on their axes. The spiral conformation of the pinions, to which allusion has been so frequently made, is best seen in the heavy-bodied birds, as the turkey, capercailzie, pheasant, and partridge; and here also the concavo-convex form of the wing is most perceptible. In the light-bodied, ample-winged birds, the amount of twisting is diminished, and, as a result, the wing is more or less flat- tened, as in the sea-gull (fig. 103). Fic. 103.—Shows the twisted levers or screws formed by the wings of the gulL Compare with fig. 53, p. 107 ; with figs. 76, 77, and 78, p. 147, and with figs. 82 and 83, p. 158. — Original. Consideration of the Forcés which propel the Wings of Insects. —In the thorax of insects the muscles are arranged in two principal sets in the form of a cross—i.e. there is a powerful vertical set which runs from above downwards, and.a powerful antero-posterior set which runs from before backwards. There are likewise a few slender muscles which proceed in a more or less oblique direction. The antero-posterior and vertical sets of muscles are quite distinct, as are likewise the oblique muscles. Portions, however, of the vertical and oblique muscles terminate at the root of the wing in jelly-looking points which greatly resemble rudimentary ‘tendons, so that I am inclined to believe that the vertical and oblique muscles exercise a direct influence on the movements of the wing. The shortening of the antero-posterior set of muscles (indi- rectly assisted by the oblique ones) elevates the dorsum of the thorax by causing its anterior extremity to approach its posterior extremity, and by causing the thorax to bulge out or expand laterally. This change in the thorax necessitates the descent of the wing. The shortening of the vertical set (aided by the oblique ones) has a precisely opposite effect, PROGRESSION IN OR THROUGH THE AIR. 187 and necessitates its ascent. While the wing 1s ascending and descending the oblique muscles cause it to rotate on its long axis, the bipartite division of the wing at its root, the spiral configuration of the joint, and the arrangement of the elastic and other structures which connect the pinion with the body, together with the resistance it experiences from the air, con- ferring on it the various angles which characterize the down and up strokes. The wing may therefore be said to be de- pressed by the shortening of the antero-posterior set of muscles, aided by the oblique muscles, and elevated by the shortening of the vertical and oblique muscles, aided by the elastic ligaments, and the reaction of the air. If we adopt this view we have a perfect physiological explanation of the phenomenon, as we have a complete circle or cycle of motion, the antero-posterior set of muscles shortening when the vertical set of muscles are elongating, and wice versé. This, I may add, is in conformity with all other muscular arrange- ments, where we have what are usually denominated exten- sors and flexors, pronators and supinators, abductors and adductors, etc., but which, as I have already explained (pp. 24 to 34), are simply the two halves of a circle of muscle and of motion, an arrangement for securing diametrically opposite movements in the travelling surfaces of all animals. Chabrier’s account, which I SUE virtually supports this hypothesis : — “Tt is generally through the intervention of the proper motions of the dorsum, which are very considerable during flight, that the wings or the elytra are moved equally and simultaneously. Thus, when it is elevated, it carries with it the internal side of the base of the wings with which it is articulated, from which ensues the depression of the external side of the wing; and when it approaches the sternal portion of the trunk, the contrary takes place. During the depres- sion of the wings, the dorsum is curved from before back- wards, or in such a manner that its anterior extremity is brought nearer to its posterior, that its middle is elevated, and its lateral portions removed further from each other. .The reverse takes place in the elevation of the wings; the anterior extremity of the dorsum being removed.to a greater 1368) ANIMAL LOCOMOTION. distancc from the posterior, its middle being depressed, and its sides brought nearer to each other. Thus its bending in one direction produces a diminution of its curve in the direc- tion normally opposed to it; and by the alternations of this motion, assisted by other means, the body is alternately com- pressed and dilated, and the wings are raised and depres by turns.”?} In the lbellule or dragon-flies, the muscles are inserted into the roots of the wings as in the bat and bird, the only difference being that in the latter the muscles creep along the wings to their extremities. In all the wings which I have examined, whether in the insect, bat, or bird, the wings are recovered, flexed, or drawn towards the body by the action of elastic ligaments, these structures, by their mere contraction, causing the wings, when fully extended and presenting their maximum _ of surface, to resume their position of rest, and plane of least resistance. The principal effort required in flight would therefore seem to be made during extension and the down stroke. The elastic ligaments are variously formed, and the amount of contraction which they undergo is in all cases accurately adapted to the size and form of the wings, and the rapidity with which they are worked—the contraction being greatest in the short-winged and heavy- bodied insects and birds, and least mm the light-bodied and ample-winged ones, particularly in such as skim or glide. The mechanical iction of the elastic ligaments, I need scarcely remark, insures a certain period of repose to the wings at each stroke, and this is a point of some importance, as showing that the lengthened and laborious flights of insects and birds are not without their stated intervals of rest. Speed attained by Inseets——Many instances might be quoted of the marvellous powers of flight possessed by insects as a class. The male of the silkworm-moth (Attacus Paphia) is stated to travel more than 100 miles a day ;? and an anony- mous writer in Nicholson’s Journal? calculates that the com- mon house-fly (Musca domestica), in ordinary flight, makes 600 1 Chabrier, as rendered by E. F. Bennett, F.L.S., ete. . 2 Linn, Trans, vii. p. 40. | 3 Vol. ii. p.-a6. PROGRESSION IN OR THROUGH THE ATR. 189 strokes per second, and advances twenty-five feet, but that the rate of speed, if the insect be alarmed, may be increased six or seven fold, so that under certain circumstances it can outstrip the fleetest racehorse. Every one when riding on a warm summer day must have been struck with the cloud of flies which buzz about his horse’s ears even when the animal is urged to its fastest paces; and it is no uncommon thing to see a bee or a wasp endeavouring to get in at the window of a railway car in full motion. If a small insect like a fly can outstrip a racehorse, an insect as large as a horse would — travel very much faster than a cannon-ball. Leeuwenhoek relates a most exciting chase which he once beheld in a menagerie about 100 feet long between a swallow and a dragon-fly (Mordella). The insect flew with incredible speed, and wheeled with such address, that the swallow, notwith- standing its utmost efforts, completely failed to overtake and capture it.? Consideration af the Forces which propel the Wings of Bats — and Birds—The muscular system of birds has been so fre- quently and faithfully described, that I need not refer to it further than to say that there are muscles which by their action are capable of elevating and depressing the wings, and of causing them to move in a forward and backward direction, and obliquely. They can also extend or straighten and bend, or flex the wings, and cause them to rotate in the direction of their length during the down and up strokes. The muscles principally concerned in the elevation of the wings are the smaller pectoral or breast muscles (pectorales minor) ; those chiefly engaged in depressing the wings are the larger pectorals (pectorales major). The pectoral muscles cor- respond to the fleshy mass found on the breast-bone or sternum, which in flying birds is boat-shaped, and furnished with a keel. These muscles are sometimes so powerful and heavy that they outweigh all the other muscles of the body. 1 PROGRESSION IN OR THROUGH THE AIR. 199 vantage is taken of the weight of the body and the shape of the pinion to utilize the air as a supporting medium. In these the pinion acts as a long lever,’ and is wielded with great precision and power, particularly at the shoulder. The Flight of the Albatross compared to the Movements of a Compass set upon Gimbals—A careful examination of the movements in skimming birds has led me to conclude that by a judicious twisting or screw-like action of the wings at the shoulder, in which the pinions are alternately advanced towards and withdrawn from the head in a manner analogous to what occurs at the loins in skating without lifting the feet, birds of this order can not only maintain the motion which they secure by a few energetic flappings, but, if neces- sary, actually increase it, and that without either bending the wing or beating the air. The forward and backward screwing action of the pinion referred to, in no way interferes, I may remark, with the rota- tion of the wing on its long axis, the pinion being advanced and screwed down upon the wind, and retracted and un- screwed alternately. As the movements described enable the sailing bird to tilt its body from before backwards, or 1 Advantages possessed by long Pinions.—The long narrow wings are most effective as elevators and propellers, from the fact (pointed out by Mr. Wen- liam) that at high speeds, with very oblique incidences, the supporting effect becomes transferred to the front edge of the pinion. It is in this way “that the effective propelling area of the two-bladed screw is tantamount to its entire circle of revolution.” A similar principle was announced by Sir George Cayley upwards of fifty years ago. “ In very acute angles with the current, it appears that the centre of resistance in the sail does not coincide with the centre of its surface, but 7s considerably in front of tt. As the obliquity of the current decreases, these centres approach, and coincide when the current becomes perpendicular to the plane ; hence any heel of the machine backwards or forwards removes the centre of support behind or before the point of sus- pension.”—Nicholson’s Journal, vol. xxv. p. 83. When the speed attained by the bird is greatly accelerated, and the stratum of air passed over in any given time enormously increased, the support afforded by the air to the inclined planes formed by the wings is likewise augmented. This is proved by the rapid flight of skimming or sailing birds when the wings are moved at long intervals and very leisurely. The same principle supports the skater as he rushes impetuously over insecure ice, and the thin flat stone projected along the surface of still water. The velocity of the movement in either case pre- vents sinking by not giving the supporting particles time to separate. 200 ANIMAL LOCOMOTION, the converse, and from side to side or “laterally, it may be represented as oscillating on one of two centres, as shown at fig. 105; the one corresponding with the long axis of the body (fie. 105, ab), the other with the long axis of the wings (cd). Between these two extremes every variety of sailing and gliding motion which is possible in the mariner’s compass when set upon gimbals may be performed ; so that a skimming or sailing bird may be said to possess perfect command over itself and over the element in which it moves. 1 N\ 2 Fic. 105. Captain Hutton makes the following remarkable state- ment regarding the albatross :—“I have sometimes watched narrowly one of these birds sailing and wheeling about in all directions for more than an hour, without seeing the slightest movement of the wings, and have never witnessed anything to equal the ease and grace of this bird as he sweeps past, often within a few yards, every part of his body perfectly motionless except the head and eye, which turn slowly and seem to take notice of everything.” } ‘¢ Tranquil its spirit seem’d and floated slow ; Even in its very motion there was rest.” 2 As an antithesis to the apparently lifeless wings of the 1“ On some of the Birds inhabiting the Southern Ocean.’ Ibis, 2d series, vol. 1, 1865: 2 Professor Wilson’s Sonnet, “‘ A Cloud,” etc. PROGRESSION IN OR THROUGH THE AIR. 208 albatross, the ceaseless activity of those of the humming-bird may be adduced. In those delicate and exquisitely beautiful birds, the wings, according to Mr. Gould, move so rapidly when the bird is poised before an object, that it is impossible for the eye to follow each stroke, and a hazy circle of indis- tinctness on each side of the bird is all that is perceptible. When the humming-bird flies in a horizontal direction, it occasionally proceeds with such velocity as altogether to elude observation. The regular and irregular in Flight.—The coot, diver, duck, and goose fly with great regularity in nearly a straight line, and with immense speed ; they rarely if ever skim or glide, their wings being too small for this purpose. The wood- pecker, magpie, fieldfare and sparrow, supply examples of what may be termed the “irregular” in flight. These, as is well known, fly in curves of greater or less magnitude, by giving a few vigorous strokes and then desisting, the effect of which is to project them along a series of para- bolic curves. The snipe and woodeoek are irreculir in another respect, their flight being sudden, Jerky, and from side to side. Mode of ascending, descending, turning, ete—All birds which do not, like the swallow and humming-birds, drop from a height, raise themselves at first by a vigorous leap, in which they incline their bodies in an upward direction, 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 and below the body, they lever themselves upwards and forwards, and in a sur- prisingly short time acquire that degree of momentum which greatly assists them in their future career. In rising from the ground, as may readily be seen in the crow, pigeon, and kingfisher (fig. 102, p. 183), the tail is expanded and the neck stretched out, so that the body is converted into an inclined plane, and acts mechanically as a kite. The centre of gravity and the position of the body are changed at the will of the bird by movements in the neck, feet, and tail, and by increasing or decreasing the angles which the under 10 202 ANIMAL LOCOMOTION. surface of the wings makes with the horizon. When a bird wishes to fly in a horizontal direction, it causes the under - surface of its wings to make a slight forward angle with the horizon. When it wishes to ascend, the angle is increased. When it wishes to descend, it causes the under surface of the wings to make a slight backward angle with the horizon. When a bird flies up, its wings strike downwards and forwards. When it flies down, its wings strike downwards and backwards. When ae in their apparently interminable flights. Lifting-capacity of Birds—The muscular power in birds is usually greatly in excess, particularly in birds of prey, as, ¢.9. the condors, eagles, hawks, and owls. ‘The eagles are remark able in this respect—these having been known to carry off young deer, lambs, rabbits, hares, and, it is averred, even young children. Many of the fishing birds, as the pelicans and herons, can likewise carry considerable loads of fish ;' and even the smaller birds, as the records of spring show, are capable of transporting comparatively large twigs for building purposes. I myself have seen an owl, which weighed a little over 10 ounces, lift 24 ounces, or a quarter of its own weight, without effort, after having fasted twenty-four hours ; and a friend informs me that a short time ago a splendid osprey was shot at Littlehampton, on the coast of Sussex, with a fish 5 Ibs. weight in its mouth. There are many points in the history and economy of birds which crave our sympathy while they elicit our admiration. Their indubitable courage and miraculous powers of flight invest them with a superior dignity, and secure for their order almost a duality of existence. The swallow, tiny and inconsiderable as it may appear, can traverse 1000 miles at a single journey ; and the albatross, despising compass and land- mark, trusts himself boldly for weeks together to the mercy or fury of the mighty ocean. The huge condor of the Andes lifts himself by his sovereign will to a height where no sound is heard, save the airy tread of his vast pinions, and, from an unseen point, surveys in solitary grandeur the wide range of plain and pasture-land ;? while the bald eagle, nothing daunted by the din and indescribable confusion of the queen of waterfalls, the stupendous Niagara, sits composedly on his 1 The heron is in the habit, when pursued by the falcon, of disgorging the contents of his crop in order to reduce his weight. 1° * The condor, on some occasions, attains an altitude of six miles. 206 _ ANIMAL LOCOMOTION. giddy perch, until inclination or desire prompts him to plunge into or soar above the drenching mists which, shapeless and ubiquitous, perpetually rise from the hissing waters of the nether caldron. Fic, 108.—Hawk and quarry.—A/fter The Graphic. \ het aa f ] ine peut ius = d THE VAUXHALL BALLOON OF MR. GREEN. ply AERONAUTICS. THE subject of artificial flight, notwithstanding the large share of attention bestowed upon it, has been particularly barren of results. This is the more to be regretted, as the interest which has been taken in it from early Greek and Roman times has been universal. The unsatisfactory state of the question is to be traced to a variety of causes, the most prominent of which are— | 1st, The extreme difficulty of the problem. 2d, The incapacity or theoretical tendencies of those who have devoted themselves to its elucidation. 3d,-The great rapidity with which wings, especially insect wings, are made to vibrate, and the difficulty experienced in ‘analysing their movements. Ath, The great weight of all flying things when compared with a corresponding volume of air. 5th, The discovery of the balloon, which has retarded the science of aérostation, by misleading men’s minds and causing them to look for a solution of the problem by the aid of a machine lighter than the air, and which has no analogue in nature. - Flight has been unusually unfortunate in its votaries. It has been cultivated, on the one hand, by profound thinkers, especially mathematicians, who have worked out innumer- able theorems, but have never submitted them to the test of experiment; and on the other, by uneducated charlatans who, despising the abstractions of science, have made the most ridi- culous attempts at a practical solution of the problem. Flight, as the matter stands at present, may be divided into two principal varieties which represent two great sects or schools—- 210 AERONAUTICS. 1st, The Balloonists, or those who advocate the employ- ment of a machine specifically lighter than the air. 2d, ‘Those who believe that weight is necessary to flight. The second school may be subdivided into (a) Those who advocate the employment of rigid inclined planes driven forward in a straight line, or revolving planes (aérial screws) ; and (>) Such .as'trust for elevation and propulsion to the vertical flapping of wings. Balloon.—The balloon, as my readers are aware, is con- structed on the obvious principle that a machine lighter than. the air must necessarily rise through it. The Montgolfier brothers invented such a machine in 1782. Their balloon consisted of a paper globe or cylinder, the motor power being super-heated air supplied by the burning of vine twigs under it. The Montgolfier or fire balloon, as it was called, was superseded by the hydrogen gas balloon of MM. Charles and Robert, this being in turn supplanted by the ordinary gas balloon of Mr. Green. Since the introduction of coal gas in the place of hydrogen gas, no radical improvement has been effected, all attempts at guiding the balloon having signally failed. This arises from the vast extent of surface which it necessarily presents, rendering it a fair conquest to every breeze that blows ; and because the power which animates it is a mere lifting ‘power which, in the absence of wind, must _ act in a vertical line. The balloon consequently rises through | the air in opposition to the law of gravity, very much as a dead bird falls in a downward direction in accordance with it. Having no hold upon the air, this cannot be employed as a fulcrum for regulating its movements, and hence the car- dinal difficulty of ballooning as an art. Finding that no marked improvement has been made in the balloon since its introduction in 1782, the more advanced thinkers have within the last quarter of a century turned their attention in an opposite direction, and have come to regard flying creatures, all of which are much heavier than the air, as the true models for flying machines. An old doctrine is more readily assailed than uprooted, and accord- ingly we find the followers of the new faith met by the assertion that insects and birds have large air cavities in AERONAUTICS. 211 their interior; that those cavities contain heated air, and that this heated air in some mysterious manner contributes to, if it does not actually produce, flight. No argument could be more fallacious. Many admirable fliers, such as the bats, have no air-cells ; while many birds, the apteryx for example, and several animals never intended to fly, such as the orang- outang and a large number of fishes, are provided with them. It may therefore be reasonably concluded that flight is in no way connected with air-cells, and the best proof that can be adduced is to be found in the fact that it can be performed to perfection in their absence. The Inclined Plane—The modern school of flying is in some respects quite as irrational as the ballooning school. The favourite idea with most is the wedging forward of a _ rigid inclined plane upon the air by means of a “ vis a tergo.” The inclined plane may be made to advance in a horizontal line, or made fo rotate in the form of a screw. Both plans have their adherents. The one recommends a large support- ing area extending on either side of the weight to be elevated; the surface of the supporting area making a very slight angle with the horizon, and the whole being wedged forward by the action of vertical screw propellers. This was the plan sug- . gested by Henson and Stringfellow. Mr. Henson designed his aérostat in 1843. ‘ The chief feature of the invention was the very great expanse of its sustaining planes, which were larger in proportion to the weight it had to carry than those of many birds. The machine advanced with its front edge a litile raised, the effect of which was to present its under surface to the air over which it passed, the resistance of which, acting upon it like a strong wind on the sails of a windmill, prevented the descent of the machine and its burden. The sustaining of the whole, therefore, depended upon the speed at which wu travelled through the air, and the angle at which its under surface impinged on the air in its front. .. . The machine, fully prepared for flight, was started from the top of an inclined plane, in descending which it attained a velocity necessary to sustain it in its further progress. That velocity would be gradually destroyed by the resistance of the air to forward flight; it was, therefore, the office of the steam- 212 AERONAUTICS. engine and the vanes it actuated simply to repair the loss of velocity ; it was made therefore only of the power and weight necessary for that small effect” (fig. 109). The editor of New- ton’s Journal of Arts and Science speaks of it thus :—“ The apparatus consists of a car containing the goods, passengers, engines, fuel, etc., to which a rectangular frame, made of wood or bamboo cane, and covered with canvas or oiled silk, is attached. This frame extends on either side of the car in a similar manner to the outstretched wings of a bird; but with this difference, that the frame is immovable. Behind the wings are two vertical fan wheels, furnished with oblique Fic. 109.—Mr. Henson’s Flying Machine. vanes, which are intended to propel the apparatus through the air. The rainbow-like circular wheels are the propellers, answering to the wheels of a steam-boat, and acting upon the air after the manner of a windmill. These wheels receive motion from bands and pulleys from a steam or other engine contained in the car. To an axis at the stern of the car a triangular frame is attached, resembling the tail of a bird, which is also covered with canvas or oiled silk. This may be expanded or contracted at pleasure, and is moved up and down for the purpose of causing the machine to ascend or descend. Beneath the tail is a rudder for directing the course of the machine to the right or to the left; and to facilitate the steering a sail is stretched between two masts which rise from the car. The amount of canvas or oiled silk necessary for buoying up the machine is stated to be equal to one square foot for each half pound of weight.” AERONAUTICS. 213 ~ Wenham! has advocated the employment of superimposed planes, with a view to augmenting the support furnished while it diminishes the horizontal space occupied by the planes. These planes Wenham designates Aéroplanes. They are inclined at a very slight angle to the horizon, and are wedged forward either by the weight to be elevated or by the employment of vertical screws. Wenham’s plan was adopted by Stringfellow in a model which he exhibited at the Aéro- nautical Society's Exhibition, held at the Crystal Palace in the summer of 1868. The subjoined woodcut (fig. 110), taken from a photograph === G|aHHd&{€4eA e— Ss Fic. 110.—Mr. Stringfellow’s Flying Machine. of Mr. Stringfellow’s model, gives a very good idea of the arrangement ; abc representing the superimposed planes, d the tail, and ¢ f the vertical screw propellers. The superimposed planes (a 6c) in this machine contained a sustaining area of twenty-eight square feet in addition to the tail (d). : Its engine represented a third of a horse power, and the weight of the whole (engine, boiler, water, fuel, superimposed planes, and propellers) was under 12 lbs. Its sustaining area, 1f that of the tail (d) be included, was something like thirty-six square feet, 7.e. three square feet for every pound —the sustaining area of the gannet, it will be remembered (p. 134), being less than one square foot of wing for every two pounds of body. i «* Aérial Locomotion,” by F. H. Wenham.—- World of Science, June 1867. 214 AERONAUTICS. The model was forced by its propellers along a wire at a great speed, but, so far as I could determine from observa- tion, failed to lift itself notwithstanding its extreme lightness and the comparatively very great power employed. The idea embodied by Henson, Wenham, and Stringfellow is plainly that of a boy’s kite sailing upon the wind. “The _kite, however, is a more perfect flying apparatus than that furnished by Henson, Wenham, and Stringfellow, inasmuch as the inclined plane formed by its body strikes the air at various angles—the angles varying according to the length of string, strength of breeze, length and weight of tail, ete. Henson’s, Wenham’s, and Stringfellow’s methods, although carefully tried, have hitherto failed. The objections are numerous. In the first place, the supporting planes (aéro- planes or otherwise) are not flexible and elastic as wings are, but rigid. This is a point to which I wish particularly to direct attention. Second, They strike the air at a gwen angle. Here, again, there is a departure from nature. Third, A machine so constructed must be precipitated from a height or driven along the surface of the land or water at a high speed to supply it with initial velocity. Fourth, It is un-- fitted for flying with the wind unless its speed greatly exceeds that of the wind. Fifth, It is unfitted for flying across the wind because of the surface exposed. Sixth, The sus- - taining surfaces are comparatively very large. . They are, moreover, passive or dead surfaces, i.e. they have no power of moving or accommodating themselves to altered circum- stances. Natural wings, on the contrary, present small flying surfaces, the great speed at. which wings are propelled con- _verting the space through which they are driven into what — is practically a solid basis of support, as explained at pp. 118, 119, 151, and 152 (vide figs. 64, 65, 66, 82, and 83, pp. 139 and 158). This arrangement enables natural wings to seize and utilize the air, and renders them superior to adventitious currents. Natural wings work up the air in which they move, but unless the flying animal desires it, they are scarcely, if at all, influenced by winds or currents which are not of their own forming. In this respect they entirely differ from the 1 Mr. Stringfellow stated that his machine occasionally left the wire, and was sustained by its superimposed planes alone. _ A®RONAUTICS. 215 balloon and all forms of fixed aéroplanes. In nature, small wings driven at a high speed produce the same result as large wings driven at a slow speed (compare fig. 58, p. 125, with fig. 57, p. 124). In flight a. certain space must be covered either by large wings spread out as a solid (fig. 57, p. 124), or by small wings vibrating rapidly (figs. 64, 65, and 66, p. 139). Fic. 111.—Cayley’s Flying Apparatus. The Aérial Screw—Our countryman, Sir George Cayley, gave the first practical illustration of the efficacy of the screw as applied to the air in 1796. In that year he constructed a small machine, consisting of two screws made of quill feathers (fig. 111). Sir George writes as under :— “As it may be an amusement to some of your readers to see a machine rise in the air by mechanical means, I will con- 216 AERONAUTICS. clude my present communication by describing an instrument of this kind, which any one can construct at the expense of ten minutes’ labour. “qaand b (fig. 111, p. 215) are two corks, into each of which are inserted four wing feathers from any bird, so as to be slightly inclined like the sails of a windmill, but in opposite directions in each set. A round shaft is fixed in the cork a, which ends in a sharp point. At the upper part of the cork 0 is fixed a whalebone bow, having a small pivot hole in its centre to receive the point of the shaft. The bow is then to be strung equally on each side to the upper portion of the shaft, and the little machine is completed. Wind up the string by turning the flyers different ways, so that the spring of the bow may unwind them with their anterior edges ascending ; then place the cork with the bow attached to it upon a table, and with a finger on the upper cork press strong enough to prevent the string from unwinding, and, taking it away sud- denly, the instrument will rise to the ceiling.” Cayley’s screws were peculiar, inasmuch as they were super- imposed and rotated in opposite directions. He estimated that if the area of the screws was increased to 200 square. feet, and moved by a man, they would elevate him. Cayley’s interesting experiment is described at length, and the ap- paratus figured in Nicholson’s Journal for 1809, p. 172. In 1842 Mr. Phillips also succeeded in elevating a model by means of revolving fans. Mr. Phillips’s model was made entirely of metal, and when complete and charged weighed 2 Ibs. It consisted of a boiler or steam generator and four fans supported between eight arms. The fans were inclined to the horizon at an angle of 20°, and through the arms the steam rushed on the principle discovered by Hero of Alexan- dria. By the escape of steam from the arms, the fans were made to revolve with immense energy, so much so that the model rose to a great altitude, and flew across two fields before it alighted. The motive power employed in the pre- sent instance was obtained from the combustion of charcoal, nitre, and gypsum, as used in the original fire annihilator ; the products of combustion mixing with water in the boiler, and forming gas charged steam, which was delivered at a high pressure from the extremities of the eight arms. This — AERONAUTICS. yay model is remarkable as being probably the first which actuated by. steam has flown to a considerable distance. The French have espoused the aérial screw with great enthusiasm, and within the last ten years (1863) MM. Nadar,? Pontin Fic. 112.—Flying Machine designed by M. de la Landelle. d’Amécourt, and de la Landelle have constructed clockwork models (orthopteres), which not only raise themselves into the air, but carry a certain amount of freight. These models are 1 Report on the First Exhibition of the Aéronautical Society of Great Britain, held at the Crystal Palace, London, in June 1868, p. 10. 2 Mons. Nadar, in a paper written in 1863, enters very fully into the sub- ject of artificial flight, as performed by the aid of the screw. Liberal extracts are given from Nadar’s paper in Astra Castra, by Captain Hatton Turner. London, 1865, p. 340. To Turner’s handsome volume the reader is referred for much curious and interesting information on the subject of A€érostation. 218 AERONAUTICS. exceedingly ~ fragile, and because of the prodigious force required to propel them usually break after a few trials. Fig. 112, p. 217, embodies M. de la Landelle’s ideas. In the helicopteric models made by MM. Nadar, Pontin - d’Amécourt, and de la Landelle, the screws (mnopgqrst of - figure) are arranged in tiers, 7.¢. the one screw is placed above the other. In this respect they resemble the aéro- planes recommended by Mr. Wenham, and tested by Mr. Stringfellow (compare mnopqrst of fig..112, with abc of fig. 110, p. 213). The superimposed screws, as already explained, were first figured and described by Sir George Cayley (p. 215). The French screws, and that employed by Mr. Phillips, are rigid or unyielding, and strike the air at a given angle, and herein, I believe, consists their. principal defect. This arrangement results in a ruinous expenditure of power, and is accompanied by a great amount of slip. The aérial screw, and the machine to be elevated by it, can be set in motion without any preliminary run, and in this respect it has the advantage over the machine supported by mere sus- taining planes. It has, in fact, a certain amount of inherent motion, its screws revolving, and supplying it with active or moving surfaces. It is accordingly more independent than the machine designed by Henson, Wenham, and Stringfellow. I may observe with regard to the system of rigid inclined planes wedged forward at a given angle in a straight line or in a circle, that it does not embody the principle carried out in nature. Geis The wing of a flying creature, as I have taken pains to show, is not rigid ; neither does it always strike the air at a given angle. On the contrary, it is capable of moving in all its parts, and attacks the air at an infinite variety of angles (pp. 151 to 154). Above all, the surface exposed by a natural wing, when compared with the great weight it is capable of elevating, is remarkably small (fig. 89, p. 171). This is accounted for by the length and the great range of motion of natural wings; the latter enabling the wings to convert large tracts of air into supporting areas (figs. 64, 65, and 66, p. 139). It is also accounted for by the multiplicity of the movements of natural wings, these enabling the pinions to create and rise upon currents of their own ad AERONAUTICS. 219 forming, and to avoid natural currents when not adapted for propelling or sustaining purposes (fig. 67, 68, 69, and 70, p. 141). If one watches an insect, a bat, or a bird when dressing its wings, he will observe that it can incline the under sur- face of the wing at a great variety of angles to the horizon. This it does by causing the posterior or thin margin of the wing to rotate around the anterior or thick margin as an axis. As a result of this movement, the two margins are forced into double and opposite curves, and the wing con- verted into a plastic helix or screw. He will further observe that the bat and bird, and some insects, have, in addition, the power of folding and drawing the wing towards the body during the up stroke, and of pushing it away from the body and extending it during the down stroke, so as alternately to diminish and increase its area; arrangements necessary to decrease the amount of resistance experienced by the wing during its ascent, and increase it during its descent. It is scarcely requisite to add, that in the aéroplanes and aérial screws, as at present constructed, no provision whatever is made for suddenly increasing or diminishing the flying sur- face, of conferring elasticity upon it, or of giving to it that infinite variety of angles which would enable it to seize and disentangle itself from the air with the necessary rapidity. Many investigators are of opinion that flight is a mere question of levity and power, and that if a machine could only be made light enough and powerful enough, it must of necessity fly, whatever the nature of its flying surfaces. A grave fallacy lurks here. Birds are not more powerful than quadrupeds of equal size, and Stringfellow’s machine, which, as we have seen, only weighed 12 lbs., exerted one-third of a horse power. 'The probabilities there- fore are, that flight 1s dependent to a great extent on the nature of the flying surfaces, and the mode of applying those surfaces to the air. Artificial Wings (Borelli’s Views)—With regard to the production of flight by the flapping of wings, much may and has been said. Of all the methods yet proposed, it is unques- tionably by far the most ancient. Discrediting as apocryphal the famous story of Dedalus and his waxen wings, we cer- 220 AKRONAUTICS. tainly have a very graphic account of artificial wings in the De Motu Animalium: of Borelli, published as far back as 1680, 2.e. nearly two centuries ago.’ Indeed it will not be too eich to affirm, that to this a: tinguished physiologist and mathematician belongs almost all | ne knowledge we possessed of artificial wings up till 1865. He was well acquainted with the properties of the wedge, as applied to flight, and he was likewise cognisant of the flexible and elastic properties of the wing. To him is to be traced the purely mechanical theory of the wing’s action. He figured a bird with artificial wings, each wing consisting of a rigid vod wn front and flexible feathers behind. I have thought fit to reproduce Borelli’s figure both because of its great antiquity, and because it is eminently illustrative of his text.” Fic. 113.—Borelli’s Artificial Bird. The wings () ¢ f, 0 ea), are represented as striking vertically downwards (gh). They remarkably accord with those de- scribed by Straus-Durckheim, Girard, and quite recently by Professor Marey.° Borelli is of opinion iat flight results from the application of an inclined plane, which beats the air, and which has a wedge action. He, in fact, endeavours to prove that a bird wedges itself forward upon the air by the perpendicular vibra- ’ Borelli, De Motu Animalium. Sm. 4to, 2-vols. Rome, 1680. 2 De Motu Animalium, Lugduni Batavorum apud Petrum Vander. Anno MDCLXXXxV, Tab. XIII. figure 2. (New edition.) * Revue des Cours Scientifiques de la France e+ de l’Etranger. ~ Mars 1869. AERONAUTICS. 221 tion of its wings, the wings during their action forming a wedge, the base of which (cde) is directed towards the head of the bird; the apex (af) being directed towards the tail. This idea is worked out in propositions 195 and 196 of the first part of Borelli’s book. In proposition 195 he explains how, if a wedge be driven into a body, the wedge will tend to separate that body into two portions; but that if the two portions of the body be permitted to react upon the wedge, they will communicate oblique wmpulses to the sides of the wedge, and expel it, base first, in a straight line. Following up the analogy, Borelli endeavours to show in his 196th proposition, “that if the air acts obliquely upon the wings, or the wings obliquely upon the air (which is, of - course, a wedge action), the result will be a horizontal trans- ference of the body of the bird.” In the proposition referred to (196) Borelli states—*“ If the expanded wings of a bird sus- pended in the air shall strike the undisturbed air beneath it with a motion perpendicular to the horizon, the bird will fly with a transverse motion in a plane parallel with the horizon.” In other words, if the wings strike vertically downwards, the bird will fly horizontally forwards. He bases his argument upon the belief that the anterior margins of the wings are rigid and unyielding, whereas the posterior and after parts of the wings are more or less flexible, and readily give way under pressure. “If,” he adds, “the wings of the bird be expanded, and the under surfaces of the wings be struck by the air ascending perpendicularly to the horizon, with such a force as shall prevent the bird gliding downwards (1.e. with a tendency to glide downwards) from falling, it will be urged an a horizontal direction. _ This follows because the two osseous rods (virge) forming the anterior margins of the wings resist the upward pressure of the air, and so retain their original form (literally extent or expansion), whereas the flexible after-parts of the wings (posterior margins) are pushed up and approximated to form a cone, the apex of which (vide a f of fig. 113) is directed towards the tail of the bird. In virtue of the air playing upon and compressing the sides of the wedge formed by the wings, the wedge is driven forwards in the direction of its base (c be), which is equiva- 293 AERONAUTICS. lent to saying that the wings carry the body of the bird to which they are attached tn a horizontal direction.” Borelli restates the same argument in different words, as follows :— “Tf” he says, “the air under the wings be struck by the ~ flexible portions of the wings (flabella, literally fly-flaps or small fans) with a motion perpendicular to the horizon, the sails (vela) and flexible portions of the wings (flabella) will yield in an upward direction, and form a wedge, the point of which is directed towards the tail. Whether; therefore, the air strikes the wings from below, or the wings strike the air from above, the result is the same—the posterior or flexible margins of the wings yield in an upward direction, and in ° so doing urge the bird in a horizontal direction.” In his 197th proposition, Borelli follows up and amplifies the arguments contained in propositions 195 and 196. “Thus,” he observes, “it is evident that the object of flight is to impel birds upwards, and keep them suspended in the air, and also to enable them to wheel round in a plane parallel to the horizon. The first (or upward flight) could not be accom- plished. unless the bird were impelled upwards by frequent leaps or vibrations of the wings, and its descent prevented. And because the downward tendency of heavy bodies is per- pendicular to the horizon, the vibration of the plain surfaces of the wings must be made by striking the air beneath them in a direction perpendicular to the horizon, and in this man- ner nature produces the suspension of birds in the air.” “ With regard to the second or transverse motion of birds (z.e. horizontal flight) some authors have strangely blundered ;~ for they hold that it is like that of boats, which, being im- pelled by oars, moved horizontally in the direction of the stern, and pressing on the resisting water behind, leaps with a contrary motion, and so are carried forward. In the same manner, say they, the wings vibrate towards the tail with a horizontal motion, and likewise strike against the undisturbed air, by the resistance of which they are moved forward by a reflex motion. But this is contrary to the evidence of our sight as well as to reason; for we see that the larger kinds of birds, such as swans, geese, etc., never vibrate their wings AERONAUTICS. 993 when flying towards the tail with a horizontal motion like that of oars, but always bend them downwards, and so describe circles raised perpendicularly to the horizon.’ Besides, in boats the horizontal motion of the oars is easily made, and a perpendicular stroke on the water would be per- fectly useless, inasmuch as their descent would be impeded by the density of the water. But in birds, such a horizontal motion (which indeed would rather hinder flight) would be absurd, since it would cause the ponderous bird to fall head- long to the earth; whereas it can only be suspended in the air by constant vibration of the wings perpendicular to the horizon. Nature was thus forced to show her marvellous skill in producing a motion which, by one and the same action, should suspend the bird in the air, and carry it forward in a horizontal direction. This is effected by striking the air below perpendicularly to the horizon, but with oblique strokes—an action which is rendered possible only by the flexibility of the feathers, for the fans of the wings in the act of striking acquire the form of a wedge, by the forcing out of which the bird is necessarily moved forwards in a horizontal direction.” The points which Borelli endeavours to establish are these :— First, That the action of the wing is a wedge action. Second, That the wing consists of two portions—a rigid anterior portion, and a non-rigid flexible portion. The rigid portion he represents in his artificial bird (fig. 113, p. 220) as consisting of a rod (er), the yielding portion of feathers (a 0). Third, That if the air strikes the under surface of the wing perpendicularly in a direction from below upwards, the flexible portion of the wing will yield in an upward direction, and form a wedge with its neighbour. Fourth, Similarly and conversely, if the wing strikes the 1 It is clear from the above that Borelli did not kffow that the wings of birds strike forwards as well as downwards during the down stroke, and /or- wards as well as upwards during the up stroke. These points, as well as the twisting and untwisting figure-of-8 action of the wing, were first described by the author. Borelli seems to have been equally ignorant of the fact that the wings of insects vibrate in a more or less horizontal direction. ° 294 AERONAUTICS. air perpendicularly from above, the posterior and flexible portion of the wing will yield and be forced in an upward direction. Fifth, That this woward melding of the posterior or asta margin of the wing results in and necessitates a horizontal - transference of the body of the bird. Sixth, That to sustain a bird in the air the wings must strike vertically downwards, as this is the direction in which a heavy body, if left to itself, would fall. Seventh, That to propel the bird in a horizontal diesen: the wings must descend in a perpendicular direction, and the : posterior or flexible portions of the wings yzeld in an upward direction, and in such a manner as virtually to communicate an oblique action to them. Kighth, That the feathers of the wing are bent m an upward direction when the wing descends, fue upward bending of the elastic feathers contributing to the horizontal travel of the body of the bird. I have been careful to expound Borelli’s views for several reasons :— 1st, Because the purely mechanical theory of the wing’s action is clearly to be traced to him. 2d, Because his doctrines have remained unquestioned for nearly two centuries, and have been adopted by all the writers since his time, without, I regret to say in the majority of cases, any acknowledgment whatever. 3d, Because his views have been revived by the modern French school ; and 4th, Because, in commenting upon and differmg from Borelli, I will necessarily comment upon and differ from all his successors. As to the Direction of the Stroke, yrelding of the Wing, etc.— The Duke of Argyll+ agrees with Borelli in believing that the wing invariably strikes perpendicularly downwards. His words are—“ Except for the purpose of arresting their flight birds can never strike except durectly downwards ; that is, against the opposing force of gravity.” Professor Owen in his Com- parative Anatomy, Mr. Macgillivray in his British Birds, Mr. Lishop in his article “ Motion” in the Cyclopedia of Anatomy aes Reign of Law”—Good Words, 1865. AERONAUTICS. 29% and Physiology, and M. Liais “On the Flight of Birds and Insects” in the Annals of Natural History, all assert that the stroke is delivered downwards and more or less backwards. To obtain an upward recoil, one would naturally suppose all that is required is a downward stroke, and to obtain an upward and forward recoil, one would naturally conclude a downward and backward stroke alone is requisite. Such, however, is not the case. In the first place, a natural wing, or a properly constructed artificial one, cannot be depressed either vertically downwards, or downwards and backwards. It will of necessity descend downwards and forwards mn a curve. This arises from its being flexible and elastic throughout, and in especial from its being carefully graduated as regards thickness, the tip being thinner and more elastic than the root, and the posterior margin than the anterior margin. In the second place, there is only one direction in which the wing could strike so at once to support and carry the bird forward. ‘The bird, when flying, is a body in motion. It has therefore acquired momentum. If a grouse is shot on the wing wz does not fall vertically downwards, as Borelli and his - successors assume, but downwards and forwards. The flat surfaces of the wings are consequently made to strike down- wards and forwards, as they in this manner act as kites to the falling body, which they bear, or tend to bear, upwards and forwards. So much for the direction of the stroke during the descent of the wing. Let us now consider to what extent the posterior margin of the wing yields in an upward direction when the wing descends.~ Borelli does not state the exact amount. The Duke of Argyll, who believes with Borelli that the posterior margin of the wing is elevated during the down stroke, avers that, “ whereas the air compressed in the hollow of the wing cannot pass through the wing owing to the closing upwards of the feathers against each other, or escape forwards because of the rigidity of the bones and of the quills in this direction, it passes backwards, and in so doing lzfts by ws force the elastic ends of the feathers. In passing backwards it communicates Et 296 AERONAUTICS. to the whole line of both wings a corresponding push forwards to the body of the bird. The same volume of air is thus made, in accordance with the law of action and reaction, to sustain the bird and carry wt forward.”' Mr. Macgillivray observes that “to progress in a horizontal direction it is neces-- sary that the downward stroke should be modified by the ele- vation in a certain degree of the free extremities of the quills.” ? Marey's Views.—Professor Marey states that during the down stroke the posterior or flexible margin of the wing yields in an upward dvrection to such an-extent as to cause the under surface of the wing fo look backwards, and make a backward angle with the horizon of 45° plus or minus according to circumstances.2 That the posterior margin of the wing yields in a slightly upward direction during the down stroke, I admit. By doing so it prevents shock, confers continuity of motion, and contributes in some measure to the elevation of the wing. The amount of yielding, however, is in all cases very slight, and the little upward movement there is, is in part the result of the posterior margin of the wing rotating around the anterior margin as an axis. That the posterior margin of the wing never yields in an upward direction until the under surface of the pinion makes a backward angle ~ of 45° with the horizon, as Marey remarks, is a matter of absolute certainty. This statement admits of direct proof. If any one watches the horizontal or upward flight of a large bird, he will observe that the posterior or flexible margin of the wing never rises during the down stroke to a perceptible extent, so that the under surface of the wing on no occasion looks backwards, as stated by Marey. On the contrary, he will find that the under surface of the wing (during the down stroke) invariably looks forwards—the posterior margin of the wing being inclined downwards and backwards ; as shown at figs. 82 and 83, p: 158 ;figi 103, p.. 16a fig. 85 Si p. 160; and fig. 88 (cde fg), p. 166. The ‘under surface of the wing, as will be seen from this 1 “Reign of Law”—Good Words, February 1865, p. 128. 2 History of British Birds. Lond. 1837, p. 43. 3 “¢ Méchanisme du vol chez les insectes. Comment se fait la propulsion,” by Professor E. J. Marey. Revue des Cours Scientifiques de la France et de VEtranger, for 20th March 1869, p. 254. AERONAUTICS. 227 account, not only always looks forwards, but it forms a true kite with the horizon, the angles made by the kite varying at every part of the down stroke, as shown more particularly at d,e,f,g; j,k, l,m of fig. 88, p. 166. Iam therefore opposed to Borelli, Macgillivray, Owen, Bishop, M. Liais, the Duke of Argyll, and Marey as to the direction and nature.of the down stroke. I differ also as to the direction and nature of the up stroke. Professor Marey states that not only does the posterior margin of the wing yield in an upward direction during the down stroke until the under surface of the pinion makes a backward angle of 45° with the horizon, but that during the up stroke it yields to the same extent am an opposite direc- tion. The posterior flexible margin of the wing, according to Marey, passes through a space of 90° every time the wing reverses its course, this space being dedicated to the mere adjusting of the planes of the wing for the purposes of flight. ‘The planes, moreover, he asserts, are adjusted not by vital and vito-mechanical acts but by the action of the adr alone ; this operating on the under surface of the wing and forcing its posterior margin upwards during the down stroke ; the air during the wp stroke acting upon the posterior margin of the upper surface of the wing, and forcing it downwards. This is a mere repetition of Borelli’s view. Marey dele- gates to the air the difficult and delicate task of arranging the details of flight. The time, power, and space occupied in reversing the wing alone, according to this theory, are such as to render flight impossible. That the wing does not act as stated by Borelli, Marey, and others may be readily proved by experiment. It may also be demonstrated mathematically, as a reference to figs. 114 and 115, p. 228, will show. Let ab of fig. 114 represent the horizon; mn the line of vibration; xc the wing inclined at an upward backward angle of 45° in the act of making the down stroke, and zd the wing inclined at a downward backward angle of 45° and in the act of making the up stroke. When the wing zc descends it will tend to dive downwards in the direction f giving very little of any horizontal support (ab); when the wing xd ascends it will endeavour to rise in the direction g, as it darts up like a kite (the body bearing it being in motion). 228 AERONAUTICS. If we take the resultant of these two forces, we have at most propulsion in the direction ab. This, moreover, would only hold true if the bird was as light as air. As, however, gravity tends to pull the bird downwards as it advances, the real flight of the bird, according to this theory, would fall in- a line between 0 and f, probably in xh. It could not possibly be otherwise ; the wing described and figured by Borelli and Marey is in one piece, and made to vibrate vertically on either side of a given line. If, however, a wing in one piece is elevated and depressed in a strictly perpendicular direction, it is evident that the wing will experience a greater resist- ance during the up stroke, when it is acting against gravity, than during the down stroke, when it is acting with gravity. Fig. 114. Fic. 115. As a consequence, the bird will be more vigorously depressed during the ascent of the wing than it will be elevated during its descent. That the mechanical wing referred to by Borelli and Marey is not a flying wing, but a mere propelling ap- paratus, seems evident to the latter, for he states that the winged machine designed by him has unquestionably not motor power enough to support its own weight.” — The manner in which the natural wing (and the artificial wing properly constructed and propelled) evades the resistance of the air during the up stroke, and gives continuous support and propulsion, is very remarkable. Fig. 115 illustrates the true principle. Let ad represent the horizon; mn the direc- tion of vibration; 2s the wing ready to make the down stroke, and xt the wing ready to make the up stroke. When the wing xs descends, the posterior margin (s) 1s screwed 1 Revue des Cours Scientifiques de la France et de ’Etranger. 8vo. March 20, 1869. AERONAUTICS, 229 downwards and. forwards in the direction s,¢; the forward angle which it makes with the horizon increasing as the wing descends (compare with fig. 85 (abc), p. 160, and fig. 88 (cdef), p. 166). The air is thus seized by a great variety of inclined surfaces, and as the under surface of the wing, which is a true kite, looks upwards and forwards, it tends to carry the body of the bird upwards and forwards in the direc- tion aw. When the wing «t makes the up stroke, it rotates in the direction ¢s to prepare for the second down stroke. It does not, however, ascend in the direction ¢s. On the contrary, it darts up like a true kite, which it is, in the direc- tion xv, in virtue of the reaction of the air, and because the body of the bird, to which it is attached, has a forward motion communicated to it by the wing during the down stroke (compare with gi of fig. 88, p. 166). The resultant of the forces acting in the directions #v and z d, is one acting in © the direction zw, and if allowance be made for the operation of gravity, the flight of the bird will correspond to a line somewhere between w and 0, probably the line «7. This result is produced by the wing acting as an eccentric—by the upper concave surface of the pinion being always directed upwards, the under concave surface downwards—by the under surface, which is a true kite, darting forward in wave curves both during the down and up strokes, and never making a backward angle with the horizon (fig. 88, p. 166) ; and lastly, by the wing employing the air under it as a ful- crum during the down stroke, the air, on its own part, react- ing on the under surface of the pinion, and when the proper time arrives, contributing to the elevation of the wing. If, as Borelli and his successors believe, the posterior margin of the wing yielded to a marked extent in an upward durection during the down stroke, and more especially if it yielded to such an extent as to cause the under surface of the “wing to make a backward angle with the horizon of 45°, one of two things would inevitably follow—either the air on which the wing depends for support and propulsion would be per- mitted. to escape before it was utilized; or the wing would dart rapidly downward, and carry the body of the bird with it. - If the posterior margin of the wing yielded in an upward direction to the extent described by Marey during the down 230 : AERONAUTICS. stroke, it would be tantamount to removing the fulcrum (the air) on which the lever formed by the wing operates. If a bird flies in a horizontal direction the angles made by the under surface of the wing with the horizon are very slight, © but they always look forwards (fig. 60, p. 126). If a bird ~ flies upwards the angles in question are increased (fig. 59, p. 126), In no instance, however, unless when the bird is everted and flying downwards, is the posterior margin of the wing on a higher level than the anterior one (fig. 106, p. 203). This holds true of natural flight, and consequently also of artificial flight. These remarks are more especially applicable to the flight of the bat and bird where the wing is made to vibrate more or less perpendicularly (fig. 17, p. 36; figs. 82 and 83, p. 158. Compare with fig. 85, p. 160, and fig. 88, p. 166). If a bird or a bat wishes to fly upwards, its flying surfaces must always be inclined upwards. It is the same with the fish. A fish can only swim upwards if its body is directed upwards. In the insect, as has been explained, the wing is made to vibrate in a more or less horizontal direction. In this case the wing has not to contend directly against eravity (a wing which flaps vertically must). As a conse- quence it is made to tack upon the air obliquely zigzag fashion as horse and carriage would ascend a steep hill (vide figs. 67 — to 70, p. 141. Compare with figs. 71 and 72, p. 144). In this arrangement gravity is overcome by the wing reversing its planes and acting as a kite which flies alternately forwards and backwards. The kites formed by the wings of the bat and bird always fly forward (fig. 88, p. 166). In the insect, as in the bat and bird, the posterior margin of the wing never rises above the horizon so as to make an upward and backward angle with it, as stated by Borelli, Marey, and others (cwa of fig. 114, p. 228). While Borelli and his successors are correct as to the wedge- action of the wing, they have given an erroneous interpretation of the manner in which the wedge is produced. Thus Borelli states that when the wings descend their posterior margins ascend, the two wings forming a cone whose base is repre- sented by cbe of fig. 113, p. 220); its apex being repre- sented by af of the same figure. The base of Borelli’s cone, it will be observed, is inclined forwards in the direction of AERONAUTICS. Jol the head of the bird. Now this is just the opposite of what ought to be. Instead of the two wings forming one cone, the base of which is directed forwards, each wing of itself forms two cones, the bases of which are directed backwards and outwards, as shown at fig. 116. : Fig. 116. In this figure the action of the wing is compared to the sculling of an oar, to which it bears a considerable resem- blance.! The one cone, viz., that with its base directed out- wards, is represented at vbd. ‘This cone corresponds to the area mapped out by the tip of the wing in the process of elevat- img. ‘The second cone, viz., that with its base directed back- wards, is represented at gyn. This cone corresponds to the area ‘mapped out by the posterior margin of the wing in the process of propelling. The two cones are produced in virtue of the wing rotating on ite root and along its anterior margin as it ascends and descends (fig. 80, p. 149; fig. 83, p. 158). The present figure (116) shows the-double twisting action of the wing, the tip describing the figure-of-8 indicated at be fghd ijkl; the posterior margin describing the figure-of-8 indi- cated at prn. It is in this manner the cross pulsation or wave referred to at p. 148 is produced. To represent the action of the wing the sculling oar (a b,%s,cd) must have a small gscull (mn, q17,0p) working at right angles to it. This follows because 1 In sculling strictly speaking, it is the upper surface of the oar which is most effective ; whereas in flying it is the under. 232 AERONAUTICS. the wing has to elevate as well as propel; the oar of a boat when employed as a scull only propelling. In order to elevate more effectually, the oars formed by the wings are made to oscillate on a level with and under the volant animal rather than above it; the posterior margins of the wings being made - to oscillate on a level with and below the anterior margins fpp. 150: 151). Borelli, and all who have written since his time, are unanimous in affirming that the horizontal transference of the body of the bird is due to the perpendicular vibration of the wings, and to the yielding of the posterior or flexible margins of the wings in an upward direction as the wings descend. I am, however, as already stated, disposed to attribute the transference, 1st, to the fact that the wings, both when elevated and depressed, leap forwards im curves, those curves uniting to form a continuous waved track; 2d, to the tendency which the body of the bird has to swing for- wards, in a more or less horizontal direction, when once set in motion; 3d, to the construction of the wings (they are elastic helices or screws, which twist and untwist when they are made to vibrate, and tend to bear upwards and onwards any weight suspended from them); 4th, to the reaction of the air on the under surfaces of the wings, which always act as kites; 5th, to the ever-varying power with which the wings are urged, this being greatest at the beginning of. the down stroke, and least at the end of the up one; 6th, to the contraction of the voluntary muscles and elastic liga- ments; 7th, to the effect produced by the various inclined surfaces formed by the wings during their oscillations ; 8¢h, to the weight of the bird—weight itself, when acting upon inclined planes (wings), becoming a propelling power, and so contributing to horizontal motion. This is proved by the fact that if a sea bird launches itself from a cliff with ex- panded motionless wings, it sails along for an incredible distance before it reaches the water (fig. 103, p. 186). The authors who have adopted Borelli’s pie of artificial wing, and who have indorsed his mechanical views of the action of the wing most fully, are Chabrier, Straus-Durckheim, Girard, and Marey. Borelli’s artificial wing, as already ex- . plained (p. 220, fig. 113), consists of a rigid rod (e,7) in AERONAUTICS. 233 front, and a flexible sail (a, 0) composed of feathers, behind. It acts upon the air, and the air acts upon it, as occasion demands. ~ Chabrier’s Views.—Chabrier states that the wing has only one period of activity—that, in fact, if the wing be suddenly lowered by the depressor muscles, it is elevated solely by the reaction of the air. There is one unanswerable objection to this theory—the bats and birds, and some, if not all the insects, have distinct elevator muscles. The presence of well- developed elevator muscles implies an elevating function, and, besides, we know that the insect, bat, and bird can elevate their wings when they are not flying, and when, consequently, no reaction of the air is induced. Straus-Durckhewms Views.—Durckheim believes the insect abstracts from the air by means of the inclined plane a com- ponent force (composant) which it employs to support and direct itself. In his Theology of Nature he describes a sche- matic wing as follows :—It consists of a rigid ribbing in front, and a flexible sail behind. A membrane so constructed will, according to him, be fit for flight. It will suffice if such a sail elevates and lowers itself successively. It will, of its own accord, dispose itself as an inclined plane, and receiving obliquely the reaction of the avr, it transfers into tractile force a ° part of the vertical impulsion it has recewed. These two parts of the wing are, moreover, equally indispensable to each other. If we compare the schematic wing of Durckheim with that of Borelli they will be found to be identical, both as regards their construction and the manner of their application. Professor Marey, so late as 1869, repeats the arguments and views of Borelli and Durckheim, with very trifling altera- tions. Marey describes two artificial wings, the one composed of a rigid rod and sail—the rod representing the stiff anterior margin of the wing; the sail, which is made of paper bordered with card-board, the flexible posterior portion. The other wing consists of a rigid nervure in front and behind of thin parchment which supports jine rods of steel. He states, that if the wing only elevates and depresses itself, “the resistance of the air is sufficient to produce all the other movements. In effect the wing of an insect has not the power of equal resistance in every part. On the anterior margin the extended nervures make it rigid, while behind it is fine and flexible. 234 AERONAUTICS. During the vigorous depression of the wing the nervure has the power of remaining rigid, whereas the flexible portion, being pushed in an upward direction on account of the resist- ance it experiences from the air, asswmes an oblique position, which causes the upper surface of the wing to look forwards.” - ... “At first the plane of the wing is parallel with the body of the animal. It lowers itself—the front part of the wing strongly resists, the sail which follows it being flexible yields. Carried by the ribbing (the anterior margin of the wing) which lowers itself, the sail or posterior margin of the wing being raised meanwhile by the air, which sets it straight again, the sail will take an intermediate position, and ¢ncline atself about 45° plus or minus according to circumstances. The wing continues its movements of depression inclined to the hori- zon, but the impulse of the air which continues its effect, and naturally acts upon the surface which it strikes, has the power of resolving itself into two forces, a vertical and a horizontal force, the first suffices to raise the animal, the second to move it along.” + The reverse of this, Marey states, takes place during the elevation of the wing—the resistance of the air from above causing the upper surface of the wing to look backwards. ‘The fallaciousness of this reasoning has been already pointed 1 Compare Marey’s description with that of Borelli, a translation of which I subjoin. ‘‘ Let a bird be suspended in the air with its wings expanded, and first let the under surfaces (of the wings) be struck by the air ascending perpendicularly to the horizon with such a force that the bird gliding down is prevented from falling: I say that it (the bird) will be impelled with @ horizontal forward motion, because the two osseous rods of the wings are able, owing tethe strength of the muscles, and because of their hardness, to resist the force of the air, and therefore to retain the same form (literally ex- tent, expansion), but the total breadth of the fan of each wing yields to the umpulse of the air when the flexible feathers are permitted to rotate around the manubria or osseous axes, and hence it is necessary that the extremities of the wings approximate each other: wherefore the wings acquire the form of a wedge whose point is directed towards the tail of the bird, but whose surfaces are compressed on either side by the ascending air in such a manner that it is driven out in the direction of its base. Since, however, the wedge formed by the wings cannot move forward unless it carry the body of the bird along with it, itis evident that it (the wedge) gives place te the air impelling it, and therefore the bird flies forward in a horizontal direction. But now let the substratum of still air be struck by the fans (feathers) of the wings with a motion perpendicular to the horizon. Since the fans and sails of the wings AERONAUTICS. 235 out, and need not be again referred to. It is not a little curious that Borelli’s artificial wing should have been reproduced in its integrity at a distance of nearly two centuries, The Author's Views:—his Method of constructing and applying Artificial Wings as contra-distinguished from that of Borelli, Chabrier, Durckheim, Marey, etc—The artificial wings which | have been in the habit of making for several years differ from those recommended by Borelli, Durckheim, and Marey in four essential points :— Ist, The mode of construction. 2d, The manner in which they are applied to the air. dd, The nature of the power employed. Ath, The necessity for adapting certain elastic substances to the root of the wing if in one piece, and to the root and the body of the wing if in several pieces. And, first, as to the manner of construction. Borelli, Durckheim, and Marey maintain that the anterior margin of the wing should be rigid ; I, on the other hand, believe that no part of the wing whatever should be rigid, not even the anterior margin, and that the pinion should be flexible and elastic throughout. That the anterior margin of the wing should not be com- posed of a rigid rod may, I think, be demonstrated in a variety of ways. If a rigid rod be made to vibrate by the hand the vibration is not smooth and continuous; on the contrary, it is irregular and jerky, and characterized by two halts or pauses (dead points), the one occurring at the end of the wp stroke, the other at the end of the down stroke. This mechanical impediment is followed by serious consequences as far as power and speed are concerned—the slowing of the wing at the end of the down and up strokes involving a acquire the form of a wedge, the point of which is turned towards the tail (of the bird), and since they suffer the same force and compression from the air, whether the vibrating wings strike the undisturbed air beneath, or whether, on the other hand, the expanded wings (the osseous axes remain- ing rigid) receive the percussion of the ascending air; in either case the Jlearble feathers yield to the impulse, and hence approximate each other, and thus the bird moves in a Sorward durection.’’—De Motu _Animalium, pars prima, prop. 196, 1685. 236547 ABRONAUTICS. great expenditure of power and a disastrous waste of time. The wing, to be effective as an elevating and propelling organ, should have no dead points, and should be character- ized by a rapid winnowing or fanning motion. It should reverse and reciprocate with the utmost steadiness and smoothness—in fact, the motions should appear as contmuous’ as those of a fly- wheel in rapid motion: they are so in the insect (figs. 64, 65, and 66, p. 139). To obviate the difficulty i In question, it is necessary, In my _ opinion, to employ a tapering elastic rod or series of rods bound together for the anterior margin of the wing. ia longitudinal section of bamboo cane, ten feet in length, and one inch in breadth (fig. 117), be taken by the ex- tremity and made to vibrate, it will be found that a wavy serpentine motion is produced, the waves being greatest when the vibration is slowest (fig. 118), and least when it is most rapid (fig. 119). It will further be found that at the extremity of the cane where the impulse is communi- cated there is a steady reciprocating movement devoid of dead pots. The continuous movement in question is no doubt due to the fact that the different portions of the cane reverse at different periods—the undulations induced being to an interrupted or vibratory movement very much what the continuous play of a fly-wheel is to a rotatory motion. The Wave Wing of the Author.—If a similar cane has added to it, tapering rods of whalebone, which radiate in an out-— ward direction to the extent of a foot or so, and the whale- bones be covered by a thin sheet of india- rubber, an artificial wing, resembling the natural one in all its essential points, is at once produced (fig. 120). I propose to designate this wing, from the peculiarities of its movements, the wave wing (fig. 121). If the wing referred to (fig. 121) be made to vibrate at its root, a series of longitudinal (cde) and transverse (fg h) waves are at once produced; the one series running in the direction of the length of the wing, the other in — the direction of as breadth (wide p. 148). This wing further (wists and wntwists, figure-of-8 fashion, during the up and down strokes, as shown at fig. 122, p. 239 (compare with figs. 82 and 83, p: 158; fig. 86, p. 161; and fig. 103) ps Pegi AERONAUTICS. 237 : There is, moreover, a continuous play of the wing; the down stroke gliding into the up one, and we versd, which ! Fig. 117.—Represents a longitudinal section of bamboo cane ten feet long, and one inch wide.— Original. Fig. 118.—The appearance presented by the same cane when made to vibrate by the hand. The cane vibrates on either side of a given line (a @), and ap- pears as if it were in two places at the same time, viz.,¢ and f, g and d, e and A. Itis thus during its vibration thrown into figures-of-S or opposite curves. — Original. Fic. 119.—The same cane when made to vibrate more rapidly. In this case the waves made by the cane are less in size, but more numerous. The cane is seen alternately on either side of the line x a, being now at ¢ now at m, now at n now at 7, now at & now at 0, now at pnow atl. The cane, when madeé to vi- brate, has no dead points. a circumstance due to the fact that no two parts of it reverse or change their curves at precisely the same instant. This curious reciprocating motion enables the wing to seize and disengage itself from the air with astonishing rapidity.— Original. Fic. 120.—The same cane with a flexible elastic curtain or fringe added to it. The curtain consists of tapering whalebone rods covered with a thin layer of india- rubber. a0 anterior margin of wing. cd posterior ditto.—Original. Fig. ‘121.—Gives the appearance presented by the artificial wing (fig. 120) when made to vibrate by the hand. It is thrown into longitudinal and transverse waves. The longitudinal waves are represented by the arrows c d@ e, and the transverse waves by the arrows f/f g h. A wing constructed on this principle gives a continuous elevating and propelling power. It developes figure-of-8 curves during its action in longitudinal, transverse, and oblique di- rections. It literally floats upon the air. It has no dead points—is vibrated witb amazingly little power, and has apparently no slip. It can fly in an up- ward, downward, or horizontal direction by merely altering its angle of in- clination to the horizon. Itis applied to the air by an irregular motion—the movement being most sudden and vigorous always at the beginning of the down stroke.— Original. . 238 AERONAUTICS. clearly shows that the down and up strokes are parts of one whole, and that neither is perfect without the other. The wave wing is endowed with the very remarkable pro- perty that it will fly in any direction, demonstrating more or less clearly that flight 1s essentially a progressive movement, — z.e. a horizontal rather than a vertical movement. Thus, if the anterior or thick margin of the wing be directed up- wards, so that the under surface of the wing makes a forward angle with the horizon of 45°, the wing will, when made to vibrate by the hand, fly with an undulating motion wm an upward dvrection, like a pigeon to its dovecot. If the under surface of the wing makes no angle, or a very small forward angle, with the horizon, it will dart forward in a series of curves in a horizontal direction, like a crow in rapid horizontal flight. Ifthe anterior or thick margin of the wing be directed downwards, so that the under surface of the wing makes a backward angle of 45° with the horizon, the wing will de- scribe a waved track, and fly downwards, as a sparrow from a house-top or from a tree (p. 230). In all those move- ments progression is a necessity. The movements are continuous gliding forward movements. There is no halt or pause between the strokes, and if the angle which the under surface of the wing makes with the horizon be properly regulated, the amount of steady tractile and buoying power developed is truly astonishing. This form of wing, which may be regarded as the realization of the figure-of-8 theory of flight, elevates and propels both during the down and up strokes,’and its working is accompanied with almost no slip. It seems literally to float upon the air. No wing that is rigid in the anterior margin can twist and untwist during its action, and produce the figure-of-8 curves generated by the living wing. To produce the curves in question, the wing must be flexible, elastic, and capable of change of form in all its parts. The curves made by the artificial wing, as has been stated, are largest when the vibration is slow, and least when it is quick. In lke manner, the air is thrown into large waves by the slow movement of a large wing, and into small waves by the rapid movement of a smaller wing. The size of the wing curves and air waves bear a fixed relation to each other, and both are dependent on the rapidity with AERONAUTICS. 239 which the wing is made to vibrate. This is proved by the fact that insects, in order to fly, require, as a rule, to drive their small wings with immense velocity. It is further proved by the fact that the small humming-bird, in order to keep itself stationary before a flower, requires to oscillate its tiny wings with great rapidity, whereas the large humming- bird (Patagona gigas), as was pointed out by Darwin, can attain the same object by flapping its large wings with a very slow and powerful movement. In the larger birds the move- ments are slowed in proportion to the ‘size, and more especially in proportion to the length of the wing ; the cranes and vultures moving the wings very leisurely, and the large oceanic birds dispensing in a great measure with the flapping of the wings, and trusting for progression and support to the wings in the expanded position. Ww r | e 0 TH MN ec SAAQ RQ Since - oN \ g x ‘ ‘ = oy =) hb 5 ar ov : / J. é d a Fic. 122. Fic. 122.—Elastic spiral wing, which twists and untwists during its action, to form a mobile helix or screw. This wing is made to vibrate by steam by a direct piston action, and by a slight adjustment can be propelled vertically, horizontally, or at any degree of obliquity. a, b, Anterior margin of wing, to which the neure or ribs are affixed. c,d, Pos- terior margin of wing crossing anterior one. a, Ball-and-socket joint at root of _ Wing ; the wing being attached to the side of the cylinder by the socket. f, Cylinder. r,r, Piston, with cross heads (w,w) and piston head (s). 0, 0, Stuffing boxes. e, f, Driving chains. m, Superior elastic band, which assists in elevating the wing. 1, Inferior elastic band, which antagonizes m. The alter- nate stretching of the superior and inferior elastic bands contributes to the continuous play of the wing, by preventing dead points at the end of the down and up-strokes. The wing is free to move in a vertical and horizontal direc- tion and at any degree of obliquity.— Original. This leads me to conclude that very large wings may be driven with a comparatively slow motion, a matter of great importance in artificial flight secured by the flapping of wings. 240 AERONAUTICS. How to construct an artificial Wave Wing on the Insect - type.—The following appear to me to be essential features 1 in the construction of an artificial wing :— The wing should be of a generally triangular shape. It should taper from the root towards the tip, and from the anterior margin in the direction of the posterior margin. It should be convex above and concave below, and slightly twisted upon itself. It should be flexible and elastic throughout, and should twist and untwist during its vibration, to produce figure-of-8 curves along its margins and throughout its substance. Such a wing is represented at fig. 122, p. 239. If the wing is in more than one piece, joints and springs require to be ‘added to the body of the pinion. In making a wing in one piece on the model of the insect wing, such as that shown at fig. 122 (p. 239), I employ one or more tapering elastic reeds, which arch from above downwards (ab) for the anterior margin. To this I add tapering elastic reeds, which radiate towards the tip of the wing, and which also arch from above downwards (9,h,7). These latter are so arranged that they confer a certain amount of spirality upon the wing; the anterior (@ 6) and posterior (¢d) margins being arranged in different planes, so that they appear to eross each other. I then add the covering of the wing, which may con- sist of india-rubber, silk, tracing cloth, linen, or any similar substance. If the wing is large, I employ steel tubes, bent to the proper shape. In some cases I secure additional strength by adding to the oblique ribs or stays (ghi of fig. 122) a series of very oblique stays, and another series of cross stays, as shown at m and a, n, 0 » p,q of fig. 123, p. 241. This form of wing is made to oscillate upon two centres viz. the root and anterior margin, to bring out the ie eccentric action of the pinion. If I wish to produce a very delicate light wing, I do so by selecting a fine tapering elastic reed, as represented at ab of fig. 124. 7 To this I add successive layers (7, h, 9, f,¢) of some flerible material, such as parchment, buckram, tracing cloth, or even AERONAUTICS. : 241 paper. As the layers overlap each other, it follows that there are five layers at the anterior margin (a0), and only one at the posterior (cd). This form of wing is not twisted upon itself structurally, but it twists and untwists, and becomes a true screw during its action. r Fic. 123. aK 7 Fie. 125, b Fic. 123.—Artificial Wing with Perpendicular (rs) and Horizontal (¢ u) Elastic Bands attached to ferrule (2). a, b, Strong elastic reed, which tapers towards the tip of the wing. d,e,f,h,t,j,k, Tapering curved reeds, which run obliquely from the anterior to the posterior margin of the wing, and which radiate towards the tip. m, Similar curved reeds, which run still more obliquely. a, n, 0,p,qg, Tapering curved reeds, which run from the anterior margin of the wing, and at right angles to it. These support the two sets of oblique reeds, and give additional strength to the anterior margin. x, Ball-and-socket joint, by which the root of the wing is attached to the cylinder, as in fig. 122, p. 239. —Original. Fic. 124.—Flexible elastic wing with tapering elastic reed (ah) running along ~ anterior margin. c,d, Posterior margin of wing 7, Portion of wing composed of one layer of flexible material. h, Portion of wing composed of two layers. g, Portion of wing composed of three layers ff, Portion of wing composed of four layers. e, Portion of wing composed of five layers. #, Ball-and-socket joint at root of wing.-—Original. Fic. 125.—Flexible valvular wing with india-rubber springs attached to its root. a, b, Anterior margin of wing, tapering and elastic. c,d, Posterior margin of wing, elastic. fj f, f, Segments which open during the up stroke and close during the down, after the manner of valves. These are very narrow, and open and close instantly. 2, Universal joint. m, Superior elastic band. n, Ditto inferior. o, Ditto anterior. p,q, Ditto oblique. 7, Ring into which the clastic bands are fixed. —Oviginal. How to construct a Wave Wing which shall evade the super- imposed Air during the Up Stroke-—To construct a wing which 2492 AERONAUTICS. shall elude the air during the up stroke, it is necessary to make it valvular, as shown at fig. 125, p. 241. This wing, as the figure indicates, is composed of numerous narrow segments (fff), so arranged that the air, when the wing is made to vibrate, opens or separates them at the - beginning of the up stroke, and closes or brings them together at the beginning of the down stroke. The time and power required for opening and closing the segments 1s comparatively trifling, owing to their extreme narrowness and extreme lightness. The space, moreover, through which they pass in performing their valvular action is exceedingly small. The wing under observation is flexible and elastic throughout, and resembles in its general features the other wings described. } I have also constructed a wing which is self-acting in another sense. This consists of two parts—the one part being made of an elastic reed, which tapers towards the ex- tremity ; the other of a flexible sail. To the reed, which corresponds to the anterior margin of the wing, delicate tapering reeds are fixed at right angles; the principal and subordinate reeds being arranged on the same plane. The flexible sail is attached to the under surface of the principal reed, and is stiffer at its insertion than towards its free mar-. gin. When the wing is made to ascend, the sail, because of the pressure exercised upon its upper surface by the air, assumes a very oblique position, so that the resistance ex- perienced by it during the wp stroke 1s very slight. When, however, the wing descends, the sail instantly flaps in an upward direction, the subordinate reeds never permitting its posterior or free margin to rise above its anterior or fixed margin. The under surface of the wing consequently descends in such a manner as to present a nearly flat surface to the earth. It experiences much resistance from the air during the down stroke, the amount of buoyancy thus furnished being very considerable. The above form of wing is more effective during the down stroke than during the up one. It, however, elevates and propels during both, the forward travel being greatest during the down stroke. Compound Wave Wing of the Author.—In order to render AERONAUTICS. 243 the movements of the wing as simple as possible, I was induced to devise a form of pinion, which for the, sake of dis- tinction I shall designate the Compound Wave Wing. This wing consists of two wave wings united at the roots, as represented at fig. 126. It is impelled by steam, its centre e! b ? ea = B B i. | fetes = He \\ aN | MIN WZ ie PN 4 [. Fic. 126. C being fixed to the head of the piston by a compound joint (x), which enables it to move in a circle, and to rotate along its anterior margin (@b¢ed; A, A’) in the direction of its length. The circular motion is for steering purposes only. The wing rises and falls with every stroke of the piston, and the move- ments of the piston are quickened during the down stroke, and slowed during the up one. During the up stroke of the piston the wing is very decidedly convex on its upper surface (abcd; A, A’), its under surface being deeply concave and inclined obliquely upwards and forwards. It thus evades the air during the up stroke. During the down stroke of the piston the wing is flattened out in every direction, and its extremities twisted in such a manner as to form two screws, as shown at a’ 0’ cd’; fg W; B,D of figure. The active area of the wing is by this means augmented, the wing seizing the air with great avidity during the down stroke. The area of the wing may be still further increased and diminished during the down and up strokes by adding joints to the body.of the wing. 944. AERONAUTICS, The degree of convexity given to the upper surface of the wing can be increased or diminished at pleasure by causing a cord (17; A, A’) and elastic band (%) to extend between two points, which may vary according to circumstances. The wing is supplied with vertical springs, which assist in slowing and reversing it towards the end of the down and up strokes, and these, in conjunction with the elastic properties of the wing itself, contribute powerfully to its continued play. The compound wave wing produces the currents on which it rises. Thus during the up stroke it draws after it a current, which being met by the wing during its descent, confers additional elevating and propelling power. During the down stroke the wing in like manner draws after it a current which forms an eddy, and on this eddy the wing rises, as explained at p. 253, fig. 129. The ascent of the wing is favoured by the superimposed air playing on the upper surface of the posterior margin of the organ, in such a manner as to cause the wing to assume a more and more oblique position with reference to the horizon. This change in the plane of the wing enables its upper surface to avoid the superincumbent air during the up stroke, while it confers upon its under sur- face a combined kite and parachute action. The compound wave wing leaps forward in a curve both during the down and up strokes, so that the wing during its vibration describes a waved track, as shown at a, ¢, ¢,g,7 of fig. 81,p. 157. The compound wave wing possesses most of the peculiarities of single wings when made to vibrate separately. It forms a most admirable elevator and propeller, and has this advan- tage over ordinary wings, that it can be worked without injury to itself, when the machine which it is intended to elevate is resting on the ground. Two or more compound wave wings may be arranged on the same plane, or super- imposed, and made to act in concert. They may also by a slight modification be made to act horizontally instead of vertically. The length of the stroke of the compound wave wing is determined in part, though not entirely by the stroke of the piston—the extremities of the wing, because of their elasticity, moving through a greater space than the centre of the wing. By fixing the wing to the head of the piston all. AERONAUTICS. 245 gearing apparatus is avoided, and the number of joints and working points reduced—a matter of no small importance when it is desirable to conserve the motor power and keep down the weight. How to apply Artificial Wings to the Air—Borelli, Durckheim, Marey, and all the writers with whom I am acquainted, assert that the wing should be made to vibrate vertically. 1 believe that if the wing be in one piece it should be made to vibrate obliquely and more or less horizon- tally. If, however, the wing be made to vibrate vertically, itis necessary to supply it with a ball-and-socket joint, and with springs at its root (m 7 of fig. 125, p. 241), to enable it to leap forward in a curve when it descends, and in another and opposite curve when it ascends (vide a, c, e, 9,4 of fig. 81, p. 157). This arrangement practically converts the vertical vibration into an oblique one. If this plan be not adopted, the wing is apt to foul at its tip. In applying the wing to the air it ought to have a figure-of-8 movement communicated to it either directly or indirectly. It 1s a peculiarity of the artificial wing properly constructed (as it is of the natural wing), that it twists and untwists and makes figure-of-8 curves during its action (see a b, cd of fig..122, p. 239), this enabling it to seize and let go the air with wonderful rapidity, and in such a manner as to avoid dead points. If the wing be in several pieces, it may be made to vibrate more vertically than a wing in one piece, from the fact that the outer half of the pinion moves forwards and backwards when the wing ascends and descends so as alternately to become a short and a long lever; this arrangement permitting the wing to avoid the resistance experienced from the air during the up stroke, while it vigorously seizes the air during the down stroke. If the body of a flying animal be in a horizontal position, a wing attached to it in such a manner that its under surface shall look forwards, and make an upward angle of 45° with the horizon is in a position to be applied either vertically (figs. 82 and 83, p. 158), or horizontally (figs. 67, 68, 69, and 70, p. 141). Such, moreover, is the conformation of the shoulder-joint in insects, bats, and birds, that the wing can be applied vertically, horizontally, or at any degree of obliquity 246 ABRONAUTICS, without inconvenience. It is in this way that an insect which may. begin its flight by causing its wings to make figure-of-8 horizontal loops (fig. 71, p. 144), may gradu- ally change the direction of the loops, and make them more and more oblique until they are nearly vertical (fig. 73, p.- 144). In the beginning of such flight the insect is screwed nearly vertically upwards; in the middle of it, it is screwed upwards and forwards; whereas, towards the end of it, the insect advances in a waved line almost horizontally (see q',7,8,U of fig. 72, p. 144). The muscles of the wing are SO arranged that they can propel it in a horizontal, vertical, or oblique direction. It is a matter of the utmost importance that the direction of the stroke and the nature of the angles made by the surface of the wing during its vibration with © the horizon be distinctly understood ; as it is on these that — all flying creatures depend when they seek to elude the up- ward resistance of the air, and secure a maximum of elevating and propelling power with a minimum of slip. As to the nature of the Forces required for propelling Arti- ficial Wings.—Borelli, Durckheim, and Marey affirm that it suffices if the wing merely elevates and depresses itself by a rhythmical movement in a perpendicular direction ; while Chabrier is of opinion that a movement of depression only 1s required. All those observers agree in believing that the details of flight are due to the reaction of the air on the sur- face of the wing. Repeated experiment has, however, con- vinced me that the artificial wing must be thoroughly under control, both during the down and up strokes-—the details of flight being in a great measure due to the movements com- municated to the wing by an intelligent agent. In order to reproduce flight by the aid of artificial wings, I find it necessary to employ a power which varies in intensity at every stage of the down and up strokes. The power which 1 The human wrist is so formed that if a wing be held in the hand at an upward angle of 45°, the hand can apply it to the air in a vertical or horizontal direction without difficulty. This arises from the power which the hand has of moving in an upward and downward direction, and from side to side with equal facility. The hand can also rotate on its long axis, so that it virtually represents all the movements of the wing at its root. AERONAUTICS. 947 suits best is one which is made to act very suddenly and forcibly at the beginning of the down stroke, and which gradu-— ally abates in intensity until the end of the down stroke, where it ceases to act in a downward direction. The power is then made to act in an upward direction, and gradually to decrease until the end of the up stroke. The force is thus applied more or less continuously ; its energy being increased and diminished according to the position of the wing, and the amount of resistance which it experiences from the air. The flexible and elastic nature of the wave wing, assisted by certain springs to be presently explained, insure a continuous vibration where neither halts nor dead points are observ- able. I obtain the varying power required by a direct piston action, and by working the steam expansively. The power employed is materially assisted, particularly during the up - stroke, by the reaction of the air and the elastic struc- tures about to be described. An artificial wing, propelled and regulated by the forces recommended, is in some respects as completely under control as the wing of the insect, bat, or bird. : Necessity for supplying the Root of Artificial Wings with Elastic Structures in vmitation of the Muscles and Elastic Liga- ments of Flying Animals.—Borelli, Durckheim, and Marey, who advocate the perpendicular vibration of the wing, make no allowance, so far as I am aware, for the wing leaping forward in curves during the down and up strokes. As a con- sequence, the wing is jointed in their models to the frame by a simple joint which moves only in one direction, viz., from above downwards, and wice versd. Observation and experiment have fully satisfied me that an artificial wing, to be effective as an elevator and propeller, ought to be able to move not only in an upward and downward direc- tion, but also in a forward, backward, and oblique direction ; nay, more, that it should be free to rotate along its anterior margin in the direction of its length; in fact, that 1ts move- ments should be universal. Thus it should be able to rise or fall, to advance or retire, to move at any degree of obliquity, and to rotate along its anterior margin. To secure the * several movements referred to I furnish the root of the wing 948 AERONAUTICS. with a ball-and-socket joint, «.¢., a universal joint (see 2 of fig. 122, p. 239). To regulate the several movements when the wing is vibrating, and to confer on the wing the various inclined surfaces requisite for flight, as well as to delegate as little as possible to the air, I employ a cross system of elastic bands. These bands vary in length, strength, and direction, and are attached to the anterior margin of the wing (near its root), and to the cylinder (or a rod extending © from the cylinder) of the model (vide m,n of fig. 122, p. 239). The principal bands are four in number—a superior, inferior, anterior, and posterior. The superior band (m) extends between the upper part of the cylinder of the model, and the upper surface of the anterior margin of the wing; the inferior band (n) extending between the under part of the cylinder or the boiler and the inferior surface of the anterior margin of the pinion. The anterior and posterior bands are attached to the anterior and posterior portions of the wing and to rods extending from the centre of the anterior and posterior portions of the cylinder. Oblique bands are added, and these are so arranged that they give to the wing during its descent and ascent the precise angles made by the wing with the horizon.in natural flight. The superior bands are stronger than the inferior ones, and are put upon the stretch during the down stroke. Thus they help the wing over the dead point at the end of the down stroke, and assist, In conjunction with the reaction obtained from the air, in elevating it. The posterior bands are stronger than the anterior ones to restrain within certain limits the great tendency which the wing has to leap forward in curves towards the end of the down and up strokes. The oblique bands, aided by the air, give the necessary degree of rotation to the wing in the direction of its length. This effect can, however, also be produced independently by the four principal bands. From what has been stated it will be’ evident that the elastic bands exercise a restraining influence, and that they act in unison with the driving power and with the reaction supplied by the air. They powerfully contribute to the continuous vibration of the wing, the vibration being peculiar in this that it varies in rapidity at every stage of the AERONAUTICS. 249 down and up strokes. I derive the motor power, as has been stated, from a direct piston action, the piston being urged either by steam worked expansively or by the hand, if it is merely a question of illustration. In the hand models the “muscular sense” at once informs the operator as to what is being done. Thus if one of the wave wings supplied with a ball-and-socket joint, and a cross system of elastic bands as explained, has a sudden vertical impulse communicated to it at the beginning of the down stroke, the wing darts downwards and forwards in a curve (vide ac, of fig. 81, p. 157), and in doing so it elevates and carries the piston and cylinder forwards. The force employed in depressing the wing is partly expended in stretching the superior elastic band, the wing being slowed towards the end of the down stroke. The instant the depress- ing force ceases to act, the superior elastic band contracts and the air reacts ; the two together, coupled with the tendency which the model has to fall downwards and forwards during the up stroke, elevating the wing. The wing when it ascends describes an upward and forward curve as shown at ce of fig. 81, p. 157. The ascent of the wing stretches the inferior elastic band in the same way that the descent of the wing stretched the superior band. The superior and inferior elastic bands antagonize each other and reciprocate with vivacity. While those changes are occurring the wing is twisting and untwisting in the direction of its length and developing figure-of-8 curves along its margins (p. 239, fig. 122, ab, cd), and throughout its substance similar to what are observed. under like circumstances in the natural wing (vide fig. 86, p. 161; fig. 103, p. 186). The angles, moreover, made by the under surface of the wing with the horizon during the down and up strokes are continually varying—the wing all the while acting as a kite, which flies steadily upwards and forwards (fig. 88, p. 166). As the elastic bands, as has been partly explained, are antagonistic in their action, the wing is constantly oscillating in some direction; _ there being no dead point either at the end of the down or up strokes. As a consequence, the curves made by the wing during the down and up strokes respectively, run into each other to form a continuous waved track, as represented at fig. 12° + 250 | AERONAUTICS. 81, p. 157, and fig. 88, p. 166. A continuous movement begets a continuous buoyancy; and it is quite remarkable to what an extent, wings constructed and applied to the air on the principles explained, elevate and propel—how little power is required, and how little of that power is wasted in slip. If the piston, which in the experiment described has been working vertically, be made to work horizontally, a series of essentially: similar results are obtained. When the piston is worked horizontally, the anterior and posterior elastic bands require to be of nearly the same strength, whereas the inferior elastic band requires to be much stronger than the superior one, to counteract the very decided ten- dency the wing has to fly upwards. The power also requires BiG. 127. ; Fie. 128. Fic. 127.—Path described by artificial wave wing from right to left. L, 0 Horizon. ™, 7,0, Wave track traversed by wing from right to left. 9, Angle made by the wing with the horizon at beginning of stroke, 4q, Ditto, made at middle of stroke. b, Ditto, towards end of stroke. c, Wing in the act of reversing ; at this stage the wing makes an angle of 90° with the horizon, and its speed is less than at any other part of its course. d, Wing reversed, and in the act of darting up to wu, to begin the stroke from ‘left to right (vide w of fig. 128). —Original.. Fic. 128.—Path described by artificial wave wing from left to right. a, 2’, Horizon. wu,v,w, Wave track traversed by wing from left to “right. t, Angle made by the wing with horizon at. beginning of stroke. y, Ditto, at middle of stroke. z, Ditto, towards end of stroke. 7, Wing in the act of reversing ; at this stage the wing makes an angle of 90° with ‘the horizon, and its speed i is less that at any other part of its course. s, Wing reversed, and in the act of darting up to m, to begin the stroke from right to left (vide m of fig. 127).—Original. to be somewhat differently applied. Thus the wing must have a violent impulse communicated to it When it begins the stroke from right to left, and also when it begins the stroke from left to right (the heavy parts of the spiral line repre- sented at fig. 71, p. 144, indicate the points where the impulse is communicated). The wing is then left to itself, the elastic bands ‘and the reaction of the air doing the remainder of the work. When the wing is forced by the piston from right to AERONAUTICS. 251 left, it darts forward in double curve, as shown at fig. 127; the various inclined surfaces made by the wing with the horizon changing at every stage of the stroke. At the beginning of the stroke from right to left, the angle made by the under surface of the wing with the horizon (oa) is something like 45° (p), whereas at the middle of the stroke it is reduced to 20° or 25° (q). At the end of the stroke the angle gradually increases to 45° (0), then to 90° (c), after which the wing suddenly turns a somersault (d), and reverses precisely as the natural wing does ate, f,g of figs. 67 and 69, p.141. The artificial wing reverses with amazing facility, and in the most natural manner possible. The angles made by its under surface with the horizon depend aca upon the speed with _ which the wing is urged at different stages of the stroke ; the angle always decreasing as the speed increases, and vice versa. As a consequence, the angle is greatest when the speed is least. When the wing reaches the point b its speed is much less than it was at g. The wing is, in fact, preparing to reverse. At c the wing is in the act of reversing (compare c of figs. 84 and 85, p. 160), and, as a consequence, its speed is at a minimum, and the angle which it makes with the horizon at a maximum. At d the wing is reversed, its speed being increased, and the angle which it makes with the horizon diminished. ‘Between the letters d and uw the wing darts suddenly up like a kite, and at «it is in a position to com- mence the stroke from left to right, as indicated at w of fig. 128, p. 250. ‘The course described and the angles made by the wing with the horizon during the stroke from left to right are represented at fig. 128 (compare with figs. 68 and 70, p. 141). The stroke from left to right is in every respect the converse of the stroke from right to left, so that a separate description is unnecessary. The Artificial Wave Wing can be driven at any speed— a can make its own currents, or utilize existing ones——The remarkable feature in the artificial wave Wing is its adapta- bility. It can be driven slowly, or with astonishing rapidity. It has no dead points. It reverses instantly, and in such a manner as to dissipate neither time nor power. It alternately seizes and evades the air so as to extract the maximum 252 AERONAUTICS, of support with the mimimum of slip, and the minimum of force. It supplies a degree of buoying and propelling power which is truly remarkable. Its buoying area is nearly equal to half a circle. It can act upon still air, and it can create and utilize its own currents. I proved this in the following manner. I caused the wing to make a horizontal sweep from right to left over a candle; the wing rose steadily as a kite would, and after a brief interval, the flame of the candle was persistently blown from right to left. I then waited until the flame of the candle assumed its normal perpendicular position, after which I caused the wing to make another and opposite sweep from left to right. The wing again rose kite fashion, and the flame was a second time affected, being blown in this case from left to right. I now caused the wing to vibrate steadily and rapidly above the candle, with this curious result, that the flame did not incline alternately from right to left and from left to right. On the contrary, it was blown steadily away from me, 7.¢. in the direction of the tip of the wing, thus showing that the arti- ficial currents made by the wing, met and neutralized each other always at mid stroke. I also found that under these circumstances the buoying power of the wing was remarkably increased. : | Compound rotation of the Artificial Wave Wing: the different rarts of the Wing travel at different speeds——The artificial wave wing, like the natural wing, revolves upon two centres (ab, ed ‘of fig. 80, -p. 149; fig. 83, p. 158) and ae p- 289), and owes much of its elevating and propelling, seizing, and disentangling power to its different portions travelling at different rates of speed (see fig. 56, p. 120), and to its storing up and giving off energy as it hastens to and fro. Thus the tip of the wing moves through a very much greater space in a given time than the root, and so also of the posterior margin as compared with the anterior. This is readily understood by bearing in mind that the root of the wing forms the centre or axis of rotation for the tip, while the anterior margin is the centre or axis of rotation for the posterior margin. The momentum, moreover, acquired by the wing during the stroke from right to left is expended i AERONAUTICS. : Da reversing the wing, and in preparing it for the stroke from left to right, and vice versd ; a continuous to-and-fro move- ment devoid of dead points being thus established. If the artificial wave wing be taken in the hand and suddenly de- pressed in a more or less vertical direction, it immediately springs up again, and carries the hand with it. It, in fact, describes a curve whose convexity is directed downwards, and in doing so, carries the hand upwards and forwards. If a second down stroke be added, a second curve is formed ; the curves running into each other, and producing a progressive waved track similar to what is represented at a,c,e,g, 1, of fig. 81, p. 157. This result is favoured if the operator runs forward so as not to impede or limit the action of the wing. How the Wave Wing creates currents, and rises upon them, and how the Air assists in elevating the Wing.—In order to ascertain in what way the air contributes to the elevation of the wing, I made a series of experiments with natural Fic. 129. and artificial wings. These experiments led me to conclude that when the wing descends, as in the bat and bird, it compresses and pushes before it, in a downward and forward 254 AERONAUTICS. direction, a column of air represented by a,b, ¢ of fig. 129, p. 253.1 The air rushes in from all sides to replace the dis- placed air, as shown at d,e,f, g,h,2, and so produces a circle ' of motion indicated by the dotted line s,¢,v,w. The wing rises upon the outside of the circle referred to, aS more par- ticularly seen at d,e,v,w. The arrows, it will be observed, are all pointing upwards, and as these arrows indicate the direction of the reflex or back current, it is not difficult to comprehend how the air comes indirectly to assist in elevating the wing. A similar current is produced to the right of the figure, as indicated by Jl, m,0,p,9,7, but seeing the wing is always advancing, this need not be taken into. account. If fig. 129 be made to assume a horizontal position, in- stead of the oblique position which it at present occupies, the manner in which an artificial current is produced by one sweep of the wing from right to left, and utilized by it in a subsequent sweep from left to right, will be readily — understood. The artificial wave wing makes a horizontal sweep from right to left, z.¢. it passes from the point a to the point ¢ of fig. 129. During its passage it has displaced a column of air. To fill the void so created, the air rushes in from all sides, viz. from d, ¢,f,9,h,2; 1, m, 0,9,9,%. The currents marked g,h,7; p,q, 7, represent the reflex or arti- ficial currents. These are the currents which, after a brief | interval, force the flame of the candle from right to left. It_ is those same currents which the wing encounters, and which contribute so powerfully to its elevation, when it sweeps from left to right. The wing, when it rushes from left to right, produces a new series of artificial currents, which are equally powerful in elevating the wing when it passes a second time from right to left, and thus the process of making and naiane: currents goes on so long as the wing is made to oscillate. In waving the arihoul wing to and fro, I found 1 The artificial currents produced by the wing during its descent may be readily seen by partially filling a chamber with steam, smoke, or some impal- pable white powder, and causing the wing to descend in its midst. By a little practice, the eye will not fail to detect the currents represented at d,¢,f, g, h,t, l,m, 0, p,q, 7 of fig. 129, p. 253. AERONAUTICS. Be the best results were obtained when the range of the wing and the speed with which it was urged were so regulated as to produce a perfect reciprocation. Thus, if the range of the wing be great, the speed should also be high, otherwise the air set in motion by the right stroke will not be utilized by the left stroke, and vice versd. If, on the other hand, the range of the wing be small, the speed should also be low, as the short stroke will enable the wing to reciprocate as per- fectly as when the stroke is longer and the speed quicker. When the speed attained is high, the angles made by the under surface of the wing with the horizon are diminished ; when it is low, the angles are increased. From these re- marks it will be evident that the artificial wave wing reci- procates in the same way that the natural wing reciprocates ; the reciprocation being most perfect when the wing is vibrating in a given spot, and least perfect when it is travel- ling at a high horizontal speed. The Artificial Wing propelled at various degrees of speed during the Down and Up Strokes—The tendency which the artificial wave wing has to rise again when suddenly and vigorously depressed, explains why the elevator muscles of the wing should be so small when compared with the depressor muscles—the latter being something like seven times larger than the former. That the contraction of the elevator muscles is necessary to the elevation of the wing, is abun- dantly proved by their presence, and that there should be so great a difference between the volume of the elevator and depressor muscles is not to be wondered at, when we remem- ber that the whole weight of the body is to be elevated by the rapid descent of the wings—the descent of the wing being entirely due to the vigorous contraction of the powerful pectoral muscles. If, however, the wing was elevated with as great a force as it was depressed, no advantage would be gained, as the wing, during its ascent (it acts against gravity) would experience a much greater resistance from the air than it did during its descent. The wing is con- sequently elevated more slowly than it is depressed; the elevator muscles exercising a controlling and restraining influence. By slowing the wing during the up stroke, 256 | } AERONAUTICS. pe air has an opportunity of reacting on its under sur- ace. The Artificial Wave Wing as a Propeller—The wave wing makes an admirable propeller if its tip be directed vertically downwards, and the wing lashed from side to side with a sculling fioure- of-8 motion, similar to that executed by the tail of the fish. Three wave wings may be made to act in concert, and with a very good result; two of them being made to vibrate figure-of-8 fashion in a more or less horizontal direction with a view to elevating ; the third being turned in a downward direction, and made to act vertically for the purpose of propelling. wf 2 + Sa rz waren €* . Fic. 130.--Aérial wave screw, whose blades are slightly twisted (a6,cd-; ef,gh), so that those portions nearest the root (dh) make a greater angle with the horizon than those parts nearer the tip (bf). The angle is thus adjusted to the speed attained by the different portions of the screw. The angle admits of further adjustment by means of the steel springs 2, s, these exercising a vestraining, and to a certain extent a regulating, influ- ence which effectually prevents shock. , It will be at once perceived from this figure that the portions of the screw marked m and 7 travel at a much lower speed than those portions marked o and p, and these again more slowly than those marked g and r (compare with fig. 56, p. 120). As, however, the angle which a wing or a portion of a wing, as I have pointed out, varies to accommodate itself to the speed attained by the wing, or a portion thereof, it follows, that to make the wave screw mechanically perfect, the angles made by its several portions must be accurately adapted to the travel of its several parts as indieated above. x, Vertical tube for receiving driving shaft. v, w, Soekets in which the roots of the blades of the screw rotate, “the degree of rotation being limited by the steel springs Zs. ab, ef, Tapering elastic reeds forming anterior or thick margins of blades of screw. de, hg, Posterior or thin elastic margins of blades of screw. mn, 0p,qvr, Radii formed by the different portions of the blades of the screw when in operation. The arrows indicate the direc- tion of travel.—Original. A New Form of Aérial Screw.—If two of the wave wings represented at fig. 122, p. 239, be placed end to end, and united to a oie portion of tube. to» form a two- bladed screw, similar to that employed in navigation, a most powerful clastic aérial screw is at once produced, as seen at fig. 130. AERONAUTICS, 257 This screw, which for the sake of uniformity I denominate the aérial wave screw, possesses advantages for aérial pur- poses to which no form of rigid screw yet devised can lay clam. The way in which it clings to the air during its revolution, and the degree of buoying power it possesses, are quite astonishing. It is a self-adjusting, self-regulating screw, and as its component parts are flexible and elastic, it accom- modates itself to the speed at Which it is driven, and gives a uniform buoyancy. ~The slip, I may add, is nominal in amount. This screw is exceedingly light, and owes its efficacy to its shape and the graduated nature of its blades; the anterior margin of each blade being comparatively rigid, the posterior margin being comparatively flexible and more or less elastic. The blades are kites in the same sense that natural wings are kites. They are flown as such when the screw revolves. I find that the aérial wave screw flies best and elevates most when its blades are inclined at a certain upward angle as indicated in the figure (130). The aérial wave screw may have the number of its blades in- creased by placing the one above the other; and two or more screws may be combined and made to revolve in opposite directions so as to make them reciprocate; the one screw pro- ducing the current on which the ones rises, as happens in natural wings. The Aérial Wave Shr ew operates also wpon Water.—The form of screw just described is adapted in a marked manner for water, if the blades be reduced in size and composed of some elastic substance, which will resist the action of fluids, as gutta-percha, carefully tempered finely graduated steel plates, etc. It bears the same relation to, and produces the same results upon, water, as the tail and fin of the fish. It throws its blades during its action into double figure-of-8 curves, similar in all respects to those produced on the anterior and posterior margins of the natural and artificial flying wing. As the speed attained by the several portions of each blade varies, so the angle at which each part of the blade strikes varies ; the angles being always greatest towards the root of the blade and least towards the tip. The angles made by the different portions of the blades are diminished in proportion as the 258 AERONAUTICS, speed, with which the screw is driven, is increased. The screw in this manner is self-adjusting, and extracts a large percentage of propelling power, with very little force and surprisingly little slip. A similar result is obtained if two finely graduated angular- _ shaped gutta-percha or steel plates be placed end to end and applied to the water (vertically or horizontally matters little), with a slight sculling figure-of-8 motion, analogous to that performed by the tail of the fish, porpoise, or whale. If the thick margin of the plates be directed forwards, and. the thin ones backwards, an unusually effective propeller is pro- | duced. This form of propeller is likewise very effective in air. CONCLUDING REMARKS. From the researches and experiments detailed in the pre- sent volume, it will be evident that a remarkable analogy exists between walking, swimming, and flying. It will further appear that the movements of the tail of the fish, and - of the wing of the insect, bat, and bird can be readily imi- tated and reproduced. These facts ought to inspire the pioneer in aérial navigation with confidence. The land and ~ water have already been successfully subjugated. The realms - of the air alone are unvanquished. ‘These, however, are so vast dnd so important as a highway for the nations, that science and civilisation equally. demand their occupation. The history of artificial progression indorses the belief that the fields etherean will one. day. be traversed by a machine designed by human ingenuity, and constructed by human skill. In order to construct a successful flying machine, it is not necessary to reproduce the filmy wing of the insect, the silken pinion of the bat, or the complicated and highly differ- entiated wing of the bird, where every feather may be said AERONAUTICS. 259 to have a peculiar function assigned to it; neither is it neces- sary to reproduce the intricacy of that machinery by which the pinion in the bat, insect, and bird is moved: all that is required is to distinguish the properties, form, extent, and manner of application of the several flying surfaces,a task attempted, however imperfectly executed, in the foregoing pages.- When Vivian and Trevithick devised the locomo- tive, and Symington and Bell the steamboat, they did not seek to reproduce a quadruped or a fish; they simply aimed at producing motion adapted to the land and water, in accordance with natural laws, and in the pre- sence of living models. Their success is to be measured by an involved labyrinth of railway which extends to every part of the civilized world; and by navies whose vessels are despatched without trepidation to navigate the most boisterous seas at the most inclement-seasons. The aéronaut has a similar but more difficult task to perform. In attempting to _ produce a flying-machine he is not necessarily attempting an impossible thing. The countless swarms of flying crea- tures testify as to the practicability of such an undertaking, and nature supplies him at once with models and materials. If artificial flight were not attainable, the insects, bats, and birds would furnish the only examples of animals whose movements could not be reproduced. History, analogy, - observation, and experiment are all opposed to this view. The success of the locomotive and steamboat is an earnest of the success of the flying machine. If the difficulties to be surmounted in its construction are manifold, the triumph and the reward will be correspondingly great. It is impos- sible to over-estimate the boon which would accrue to mankind from such a creation. Of the many mechanical problems before the world at present, perhaps there is none greater than that of aérial navigation. Past failures are not to be regarded as the harbingers of future defeats, for it is only within the last few years that the subject of artificial flight has been taken up in a true scientific spirit. Within a com- paratively brief period an enormous mass of valuable data has been collected. As societies for the advancement of aéro- nautics have been established in Britain, America, France, 260 7 AERONAUTICS. — a and other countries, there is reason to believe that our . knowledge of this most difficult department of science will 4 go on increasing until the knotty problem is finally solved. If this day should ever come, it will not be too much to ; affirm, that it will maugurate a new era in the history of mankind ; and that great as the destiny of our race has been ~ hitherto, it will be quite out-lustred by the grandeur and magnitude of coming events. ~ INDEX. PAGE AERIAL creatures not stronger than terrestrial ones, ° ° 13 Aérial flight as distinguished from sub- aes flight, : . ° 92 Aéronautics, : ° e209 Air cells in insects and birds not necessary to flight, : : LED Albatross, flight of, compared to compass set upon g eimbals, = 2 199 Amphibia have larger travelling surfaces than land animals, put less than aérial ones, ; : - : 8 Artificial fins, flippers, and wings, how constructed, . . . 14 Artificial wings, Borelli, . : ‘ : : : «2 2he Do. Marey, ; Ree : : ‘ on 220 Do. Chabrier, . c : : . « .- 2o0 = De. Straus-Durckheim, : . ° ° - 233 Do. how to apply to the air, : ° - 245 Do. nature of forces required to pr opel, . ° « . 240 Artificial wave wing of Pettigrew, : . « 236 Do. how to construct on insect type, - ; 240 Do. how to construct to evade the sue Salas air duri ing the up stroke, . . 241 Do. can create currents and rise upon them, : . 209 Do. can be driven at any speed; can make new currents and utilize old ones, . : 3 : 251, 255 Do. as a propeller and aérial screw, . a4 200 Do. compound rotation of: the different parts of the ue travel at different speeds, Do. necessity for supplying root of, with elastic structur es, a Artificial compound wave wing of Pettigrew, . - 2 242 Atmospheric pressure, effects of, on limbs, ° ° ° 5 24 Axioms, fundamental, . : : : : . opts Bde BALANCING, how effected in flight, : : ° ° oe ALES Balloon, . | ° ° oo eal Bats and birds, lax condition of shoulder joint i in, . ° ala Birds, lifting capacity of, 2 ee AS) Body and wing recipr ocate in flight, and each describes a waved track, 12 Bones, : ot Paes é y Bones of the extremities twisted and spir al, "98, 29 Bones of wing of bat—spiral configuration of their articular surfaces, eee 7s Bones of wing of bird—their articular surfaces, movements, etc., eu eS Borelli’s artificial (nic: Papen : : - : ° » 220 CHABRIER’S artificial wings 5 . é ‘ ; oie Dae on> ; 262 INDEX, vee ELYTRA or wing cases and membranous wings, . ° ° meee 64) FEATHERS, primary, secondary, and tertiary, . | Pee S aee Fins, flippers, and wings form mobile helices or screws, ; : 14 Flight, weight necessary to, ‘ : F 3, 4,110, 111, 112, 113 Flight the poetry of motion, : : : - : 6 Flight the least fatiguing kind of motion, - - ° - 13 Flight under water, ; : ‘ s oe Flight of the flying- fish, " ‘ es Flight, horizontal, in part due to weight of flying mass, . a ao Flight—the regular and irregular, 2 3) ae Flight—how to ascend, descend, and turn, : ‘* ee Flight of birds referrible to muscular exertion and weight, 4 . 204 Fluids, mechanical effects of, on animals immersed in them, ; . 18 Fluids, resistance of, . ; : : : a - 18 Flying machine, Henson, 3 : : oh eee Do. Stringfellow, : “ . : ~ > ais Do. Cayley, . ; i , : ; sate Do, “Phithigs.<¢ - “ ‘ ; < O Do. M. de 1a Landelle, : : : ‘ ee Do. ~ Borelli, ; : : 219 A flying machine possible, “¢ 2,3 Forces which propel the wings of insects, ‘bats, and birds, : 186, 189 Fulcra, yielding, : ‘ ; : : mt 104, 165 GRAVITY, the legs move by the force of, : ahiets “= 18 Gravity, centre of, : : : 18 History of the figure-of-8 theory of walking, swimming, and flying, 15 JOINTS, : ; : : : 3 : 23 KITE-LIKE action of the wings, . . 98 Kite—how kite formed by wing differs from boy’: S kite, | 2 166 Laws of natural and artificial progression the same, . : . 4,17 Legs, moved by the force of gravity, - : 5 . : 18 Lever—the wing one of the third order, ° . «AOS Levers, the three orders of, : : ; : : 19 Life linked to motion, : a) Lifting capacity of birds, . : 205 Ligaments, 24 Ligaments, elastic, position and action of, in wing of pheasant, snipe, crested crane, swan, etc., 191 Ligaments, elastic, more highly differentiated in wings which vibrate quickly, : =% : ° Mae |S Locomotion, the active or cans of, . : ° ° : 24 Locomotion, the passive organs of, 2 . . ° : 21 Locomotion of the horse,. . : ° : ; . see Locomotion of the ostrich, A . . . , 45 Locomotion of man, : , : : 4 : A 51 Marey’s artificial wings, . , . . , : ~ 233 Membranous wings, 5 <) ee Motion associated with the life and well- being of animals, . : 1 Motion not confined to the animal kingdom, . : ° : Motion, natural and artificial, . ; . : ‘ : PAGE INDEX. | 263 : PAGE Motion, of uniform, ° ° : ° ‘ ° : 17 Motion uniformly varied, : ‘ P ‘ 17 Muscles, their properties, mode of action, ete; ¢ ‘ 24 Muscles arranged in longitudinal, transver se, and oblique spiral lines, . 28 Muscles, oblique spiral, necessary for spiral bones and joints, . ‘ dl Muscles take precedence of bones in animal movements, : : 29 Muscular cycles, . : : ; : . d As 26 Muscular waves, . : : : ‘ ‘ 4 26 PENDULUMS, the extremities of animals act as, in walking, PAS; 56, a : Plane, inclined, as applied to the air, Pettigrew’s method of constructing and applying artificial wings as contradistinguished from that of Borelli, Chabrier, Durckheim, Marey, etc., . : ; : ‘ } . 200 Pettigrew’ S wave Wing : A ° . of yaee Pettigrew’s ee wave wing, . : . . « 242 Progression on the land, . : . : . ‘ : 37 Do. on or in the water,” .. e ° ° : : 64 Do. _ in or through the air, : ‘ : : 2 AS QUADRUPEDS walk, fishes swim, and insects, bats, and birds Aly, by figure-of-8 movements, : ; 215, 16 Screws—the wing of the bird and the extremity of the biped and quadruped screws, structurally and functionally, .. 12 Screws—difference between those formed by the wings and those em- ployed in navigation, : ; , ‘ : voy Loe ‘Sculling action of the wing, : ; 5 ° | ok Speed attained by insects, . 188 Speed of wing movements partly accounted for, F 120 Spine, spiral jnovements of, transferred to the extremities, S : 30 Straus-Durckheim’s artificial wings, ot ).Zoe Swimming of the fish, whale, porpoise, etc, , ’ ° 5 CS Swimming of the seal, sea- -bear, and walrus, . ° : ° 74 Swimming of man, : : 78 Swimming of the turtle, triton, crocodile, etc., - : 89 TERRESTRIAL animals have smaller travelling surfaces than amphibia, amphibia than fishes, and fishes than insects, bats, and birds, : 8 The travelling surfaces of animals increase as the density of the media traversed decreases, . 7,8 The travelling surfaces of animals variously modified and adapted to the media on or in which they move, ; : ‘ d4 WALKING, swimming, and flying correlated, . : : 5 Walking of the quadruped, biped, etc., . A : 9, 10, 11 Wave wing of Pettigrew, . : : . 236 Do. how to construct on insect type, a 240 Do. how to construct to evade the ® superimposed air during the up stroke, . : : ; oo eal Do. can be driven at any speed, ‘ : 2519255 Do. can create currents and rise upon them, : : ae its: _ Do. can make new currents and utilize existing ones, . 25, 255. Do. as a propeller, ‘ : : : : a OO Do. as an aérial screw, . : : : ‘i 26 Do. forces required to “apply to the air, 245, 246 Do. necessity for supplying root of, with elastic ‘structures, « wee 26 4 INDEX. by PAGE Wave wing, compound, . : : ; 242 Weight necessary to flight, 110 Weight contributes to flight, 112 Weight, momentum, and power to a certain extent synonymous in fli cht, 114 The wing of the bird and the extremity of the biped and quadruped are screws, structur ally and functionally, , 186 Wing in flight describes figure-of-8 curves, 12 Wing during its action reverses its planes and describes a figure- of-8 : iY ack j in space, 140 Wing when advancing with the body describes bet and waved tracks, 143 Wing, margins of, thrown into oe curves during extension and flexion, : 146 Wing, tip of, describes an ellipse, 147 Wing ‘and body reciprocate in flight, and ‘each describes a wave ‘track, 12 Wing moves in opposite curves to body, ; : 168 Wing ascends when body descends, and vice versh, 159 Wing during its vibrations produces a cross pulsation, ia. > 1s Wing vibrates unequally with reference to a given line, : 150, 231 Wing, compound rotation of, : : 149 Wing a lever of the third order, : : : ; 103 Wing acts on yielding fulecra, : es 104, 165 Wings, their form, etc., all wings screws, structurally and functionally, 136 Wing capable of change of form in all its: parts, ; 147 Wing- -area variable and in eXcess, 124 Wing- -area decreases as the size and weight of the volant animal in- creases, . Tee Wing, natural, when elevated and depressed must move “for wards, 156 Wing, angles formed by, when in action, 167 Wing acts as true kite both duri ing down and up strokes, 165 Wing, traces of design in, 180 Wing of bird not always opened up to same extent in up stroke, 182 Wing, flexion of, necessary to flight of birds, 183 Wing flexed and. partly elevated by action of elastic ligaments, 191 Wing, power of, to what owing, 194 Wing, effective stroke of, why delivered downwards and forwards, 195 Wing acts as an elevator, propeller, and sustainer both during exten- sion and flexion, 197 - Wings, points wherein the screws formed by, differ from those in ordi- nary use, : ; 15] Wings at all ‘times thor oughly under control, 154 Wings of insects, consideration of forces which pr opel, . 186 - Wings of bats and birds, consideration of forces which pr opel, 189 LIST OF AUTHORS AND SUBFECTS OF THETR BOOKS, TO BE PUBLISHED IN THE INTERNATIONAL SCIENTIFIC SERIES. Rev. M. J. Berxetzy, M. A., F. L.S., and M. Cooke, M. A., LL. D., Fungi, thetr Nature, [nfluences, and Uses. Prof. Oscar ScumipT (University of Stras- burg), Zhe Theory of Descent and Darwinism. Prof. VoGEt (Polytechnic Academy of Ber- lin), Ze Chemical Effects of Light. Prof. W. KinGapon Cutirrorp, M. A., The First Principles of the Exact Sct- ences explained ta the Non-mathematz- cal, Pree... Huxiey, LL. D., F.R. 5., Bodily Motion and Consciousness. Dr. W. B. Carpenter, LL. D., F.R.S., The Physical Geography of the Sea. Prof. Wi1LL1AM Op.iina, F. R. S., The Old Chemistry from the New Stand-pornt. Prof. SHELDON Amos, The Science of Law. W. Lauper Linpsay, M.D., F. R. S. E., Mind in the Lower Animals. Sir Joun Lussock, Bart., F.R.S., The Antiquity of Man. Prof. W. T. TuHisELTON Dyer, B. A., B.S. C., Form and Habit in Flower- ing Plants. Prof. MicHAEL Foster, M. D., Proto- plasm and the Cell Theory. Prof. W. STANLEY JEvons, The Logic of Statistics. Dr. H. CHartton Bastian, M.D.,F.R.S., _ The Brain as an Organ of Mind. ira A. C. Ramsay, LL. Do bh: RS. Earth Sculpture; Hills, Valleys, Mountains, Plains, Rivers, Lakes; how they were Produced, and how they have been Destroyed. Prof. RupotpH Vircuow (University of Berlin), Morbid Physiological Action. Prof. CiLaupE BERNARD (College of France), Physical and Metaphysical Phenomena of Life. Prof. A. QuETELET (Brussels Academy of Sciences), Soctal Physics. Prof. H. SAINTE-CLAIRE DEVILLE, Ax Jx- troduction to General Chemistry. Prof. Wurtz, Atoms and the Atomic Theory. Prof. Dr QvuATREFAGES, The Negro Races. Prof. LAcAzE-DuTHIERS, Zoology since Cuvier. Prof. BERTHELOT, Chemical Synthesis. Prof. J. ROSENTHAL, General Physiology of Muscles and Nerves. Prof. C. A. YounGc (Dartmouth College), The Sun. Prof. James D. Dana, M. A., LL. D., Ox Cephalization ; or, Head-Characters wm the Gradation and Progress of Life. ; Prof. S. W. Jounson, M. A., Ox the Nu- trition of Plants. Prof. Austin Fint, Jr.. M. D., The Ner- vous System and tts Relation to the Bodily Functions. Prof. W. D. WuitnEy, Medern Linguis- tac Science. Prof. BERNSTEIN (University of Halle), Physiology of the Senses. Prof. FERDINAND CoHN (University of Breslau), Thallotyphes (Algae Lichens Fungi). Prof. HERMANN (University of Zurich), Respiration. Prof. LEucKarT (University of Leipsic), Outlines of Animal Organization. Prof. LizspreicH (University of Berlin), Outlines of Toxicology. Prof. Kunpt (University of Strasburg), On Sound. Prof. Lonmet (University of Erlangen), Optics. Prof. REEs (University of Erlangen), Oz Parasitic Plants. Prof. STEINTHAL (University of Berlin), Outlines of the Science of Language. D. APPLETON & CO., Publishers, 549 & 551 Broadway, N. Y. Opinions of the Press on the ** International Scientific Series.” Tyndall's Forms of Water. 1 vol.,12mo. Cloth. Illustrated. . . . . « « 3 -Pige reas ‘“In the volume now published, Professor Tyndall has presented a noble illustration of the acuteness and subtlety of his intellectual powers, the scope and insight of his scientific vision, his singular command of the appropriate language of exposition, and the peculiar vivacity and grace with which he unfolds the results of intricate: scientific research.”—WV. VY. Trcbune. ‘“‘The ‘Forms of Water,’ by Professor Tyndall, is an interesting and instructive \ittle volume, admirably printed and illustrated. Prepared expressly for this series, it is in some measure a guarantee of the excellence of the volumes that will follow, and an indication that the publishers will spare no pains to include in the series the freshest in- vestigations of the best scientific minds.” —Boston Fournal. “‘This series is admirably commenced by this little volume from the pen of Prof. Tyndall. A perfect master of his subject, he presents in a style easy and attractive his methods of investigation, and the results obtained, and gives to the reader a clear con- ception of all the wondrous transformations to which water is subjected.” — Churchman. ' II Bagehot's Physics and Politics. I vol., I2mo. Price, $1.50. ‘‘ If the ‘International Scientific Series’ proceeds as it has begun, it will more than fulfil the promise given to the reading public in its prospectus. ‘The first volume, by Professor Tyndall, was a model of lucid and attractive scientific exposition; and now we have a second, by Mr. Walter Bagehot, which is not only very lucid and charming, but also original and suggestive in the highest degree. Nowhere since the publication of Sir Henry Maine’s ‘Ancient Law,’ have we seen so many fruitful thoughts sug- gested in the course of a couple of hundred pages. . . . Todo justice to Mr. Bage- hot’s fertile book, would require a long article. With the best of intentions, we are conscious of having given but a sorry account of it in these brief paragraphs. But we hope we have said enough to commend it to the attention of the thoughtful reader.” — Prof. JoHNn Fiske, in the Atlantic Monthly. ‘‘Mr. Bagehot’s style is clear and vigorous. We refrain from giving a fuller ac- count of these suggestive essays, only because we. are sure that our readers will find it worth their while to peruse the book for themselves; and we sincerely hope that the forthcoming parts of the ‘International Scientific Series’ will be as interesting.”’— Atheneum. ‘‘Mr. Bagehot discusses an immense variety of topics connected with the progress of societies and nations, and the development of their distinctive peculiarities; and his book shows an abundance of ingenious and original thought.”—ALFRED RussELL WaALtacr, in Nature. D. APPLETON & CO., Publishers, 549 & 551 Broadway, N. Y. Opinions of the Press on the “ International Scientific Series.” Hil. Foods. By Dr. EDWARD SMITH. ever,temo. Cloth. Illustrated. ... . . + < . Price, $1.75. In making up Tue INTERNATIONAL SCIENTIFIC SERIES, Dr. Edward Smith was se- lected as the ablest man in England to treat the important subject of Foods. His services were secured for the undertaking, and the little treatise he has produced shows that the choice of a writer on this subject was most fortunate, as the book is unquestionably the clearest and best-digested compend of the Science of Foods that has appeared in our language. “‘ The book contains a series of diagrams, displaying the effects of sleep and meals on pulsation and respiration, and of various kinds of food on respiration, which, as the results of Dr. Smith’s own experiments, possess a very high value. We have not far to go in this work for occasions of favorable criticism; they occur throughout, but are perhaps most apparent in those parts of the subject with which Dr. Smith’s name is es- pecially linked.” —Loxdon Examiner. ** The union of scientific and popular treatment in the composition of this work will afford an attraction to many readers who would have been indifferent to purely theoreti. cal details. . . . Still his work abounds in information, much of which is of great value, and a part of which could not easily be obtained from other sources. Its interest is de- cidedly enhanced for students who demand both clearness and exactness of statement, by the profusion of well-executed woodcuts, diagrams, and tables, which accompany the volume. .. . The suggestions of the author on the use of tea and coffee, and of the va. rious forms of alcohol, although perhaps not strictly of a novel character, are highly in- structive, and form an interesting portion of the volume.”—W. VY. Tribune. ) IV. / Body and Mind. THE THEORIES OF THEIR RELATION. By ALEXANDER BAIN, LL. D. Memeo Cloth. 2. 5 ose tek a ee. Price,. $1.50. PROFESSOR BAIN is the author of two well-known standard works upon the. Science of Mind—‘“‘ The Senses and the Intellect,’”’ and ‘‘ The Emotions and the Will.” He is one of the highest living authorities in the school which holds that there can be no sound or valid psychology unless the mind and the body are studied, as they exist, together. “It contains a forcible statement of the connection between mind and body, study- ing their subtile interworkings by the light of the most recent physiological investiga- tions. The summary in Chapter V., of the investigations of Dr. Lionel Beale of the embodiment of the intellectual functions in the cerebral system, will be found the freshest and most interesting part of his book. Prof. Bain’s own theory of the ccnnec- tion between the mental and the bodily part in man is stated by himself to be as follows: There is ‘one substance, with two sets of properties, two sides, the physical and the mental—a double-faced unity.’ While, in the strongest manner, asserting the union of mind with brain, he yet denies ‘the association of union zz flace,’ but asserts the union of close succession in time,’ holding that ‘ the same being is, by alternate fits, un- der extended and under unextended consciousness.”’ ’—Christian Register. D. APPLETON & CO., Publishers, 549 & 551 Broadway, N. Y. Opinions of the Press on the‘ International Scientific Series.” ¥. The Study of Sociology. By HERBERT SPENCER. T2mo.: Cloths =. 0560 Sete ee ee ee ‘“‘ The Study of Sociology ’”’ was written for the purpose of conveying to the reading public more definite ideas concerning the nature, claims, scope, limits, and difficulties, of the Science of Sociology. It is intended to prepare the way for the author’s great work on the ‘‘ Principles of Sociology,” which is to follow the ‘‘ Principles of Psychol- ogy.” But, while serving thus as an introduction to the larger work, the present vol- ume is complete in itself. Its style 1s exceedingly clear and vigorous, and the book abounds with a wealth of illustration. ‘‘ The philosopher whose distinguished name gives weight and influence to this vol- ume, has given in its pages some of the finest specimens of reasoning in all its forms and departments. ‘There is a fascination in his array of facts, incidents, and opinions, which draws on the reader to ascertain his conclusions. The coolness and calmness of his treatment of acknowledged difficulties and grave objections to his theories win for him a close attention and sustained effort, on the part of the reader, to comprehend, fol- low, grasp, and appropriate his principles. This book, independently of its bearing upon sociology, is valuable as lucidly showing what those essential characteristics are which entitle any arrangement and connection -of facts and deductions to be called a science.” —LEpiscopalian. “‘To those who are already acquainted with Mr. Spencer’s writing, there is no need of recommending the work; to those who are not, we would say, that by reading ‘‘The Study of Sociology’ they will gain the acquaintance of an author who, for knowledge, depth of thought, skill in elucidation, and originality of ideas, stands prominently for- ward in the front rank of the glorious army of modern thinkers. ‘The Study of Soci- ology’ is the fifth of ‘The International Scientific Series,’ and for beauty of type and elegant appearance is worthy of the great publishin g-house of Messrs. Appleton & Co.”’ —Boston Gazette. ‘‘ This volume belongs to ‘ The International Scientific Series,’ which was projected with so high a standard and which is being so successfully carried out. ‘The value and character of the whole may fairly be judged by this and the preceding volumes. The principle of the enterprise is that each subject shall be treated by the writer of greatest eminence in that department of inquiry, and it is well illustrated in the present work. Herbert Spencer is unquestionably the foremost living thinker in the psychological and sociological fields, and this volume is an important contribution to the science of which it treats. ... . It will prove more popular than any of its author’s other creations, for it is more plainly addressed to the people and has a more practical and less speculative cast. It will require thought, but it is well worth thinking about.”’—Alé6any Evening Fournal. ‘‘Whether the reader agrees with the author or not, he will be delighted with the work, not only for the beauty and purity of its style, and ‘breadth and cyclopedic char- acter of Mr. Spencer’s mind, but also for its freedom from prejudice and kindred i imper- fections.’—Norwich Bulletin. ‘“‘This work compels admiration by the evidence which it gives of immense re- search, study, and observation, and is withal written in a popular and very pleasing style. It is a fascinating work, as well as one of deep practical thought.” —Soston Fost. D. APPLETON & CO., Publishers, 549 & 551 Broadway, N. Y. 7 — eo, | Opinions of the Press on the ‘International Scientific Series.” mine N ee -£ hemistry, By JOSIAH P. COOKE, fr., Erving Professor of Chemistry and Mineralogy in Harvard University. meeeememo.* Cloth, . 7... el} Ye Price, $2.00. ** The book of Prof. Cooke is a model of the modern popular science work. It has just the due proportion of fact, philosophy, and true romance, to make it a fascinating companion, either for the voyage or the study.’’—Dazly Graphic. ‘‘ This admirable monograph, by the distinguished Erving Professor of Chemistry in Harvard University, is the first American contribution to ‘The International Scien- tific Series,’ and a more attractive piece of work in the way of popular exposition upon a difficult subject has not appeared in along time. It not only well sustains the char- acter of the volumes with which it is associated, but its reproduction in European coun- tries will be an honor to American science. It is, moreover, in an eminent degree, timely, for, between the abandonment of its old views and the bewilderment caused by the new, chemical science was getting into a demoralized condition. A work was greatly needed that should relieve the discomfort of transition, and bridge over the gulf between the old order of ideas and those which are to succeed them. Professor Cooke’s compendious contribution to the present exigencies of chemical literature will give the students of the science exactly the help they need, and pass them over by an easy and pleasant route into the new realm of chemical philosophy.”—New York Tribune. ‘¢ All the chemists in the country will enjoy its perusal, and many will seize upon it as a thing longed for. For, to those advanced students who have kept well abreast of the chemical tide, it offers a calm philosophy. To those others, youngest of the class, who have emerged from the schools since new methods have prevailed, it presents a generalization, drawing to its use all the data, the relations of which the newly-fledged fact-seeker may but dimly perceive without its aid... . To the old chemists, Prof. Cooke’s treatise is like a message from beyond the mountain. They have heard of changes in the science; the clash of the battle of old and new theories has stirred them from afar. The tidings, too, had ceme that the old had given way; and little more than this they knew. . . . Prof. Cooke’s‘ New Chemistry’ must do wide service in bringing to close sight the little known and the longed for. . . . As a philosophy it is elemen- tary, but, as a book of science, ordinary readers will find it sufficiently advanced.’”’— Utica Morning Herald. ‘A book of much higher rank than most publications of its class. It treats only of modern chemical theories—relating to molecules, combining proportions, reactions, atomic weights, isomerism, and the synthesis of organic compounds—taking one into the very arcana of chemical mysteries. ‘Though there are no more recondite branches of the science than those here explained and illustrated, such is Professor Cooke’s clearness that he may be said to make every thing plain to the average reader, who will but take pains with his lessons. Professor Cooke reminds us, in his simplicity and lucidity of statement, of Professor Tyndall, than which there can be no higher praise.” —New York Fournal of Commerce. *“The aim of the work is to furnish a hand-book of a symmetrical science, resting fundamentally upon the law of Avogadro that ‘equal volumes of all substances, when in the state of gas and under like conditions, contain the same number of molecules.’ It is to a rigid adherence to this law and the deductions which flow from it that chem- istry, as now taught, owes the marked difference which separates it from the chemistry taught a few years ago. The original lectures of Professor Cooke, enlarged and somewhat modified, present in their present form a clear and full exposition of the sci- ence, and will form a useful text-book as well as a volume of unusual interest to the lovers of physical science.””—New York World. D. APPLETON & CO., Publishers, 549 & 551 Broadway, N. Y. Opinions of the Press on the *‘ International Scientific Series.” Vil The Conservation of Energy. By BALFOUR STEWART, LL. D. With an Appendix, treating of the Vital and Mental Applications of ; the Doctrine. ; ivol.,12mo. Cloth. - .°. . . 0...) Note to the American Edition. ‘‘ The great prominence which the modern doctrine of the Conservation of Energy or Correlation of Forces has lately assumed in the world of thought, has made a simple and popular explanation of the subject very desirable. The present work of Dr. Bal- four Stewart, contributed to the ‘International Scientific Series,’ fully meets this re- quirement, as it is probably the clearest and most elementary statement of the question that has yet been attempted. Simple in language, copious and familiar in illustration, and remarkably lucid in the presentation of facts and principles, his little treatise forms just the introduction to the great problem of the interaction of natural forces that is re- quired by general readers. But Prof. Stewart having confined himself mainly to the physical aspects of the subject, it was desirable that his views should be supplemented by a statement of the operation of the principle in the spheres of life and mind. An Appendix has, accordingly, been added to the American edition of Dr. Stewart’s work, in which these applications of the law are considered. ‘Prof. Joseph Le Conte published a very able essay fourteen years ago on the ‘Correlation of the Physical and Vital Forces,’ which was extensively reprinted abroad, and placed the name of the author among the leading interpreters of the subject. His mode of presenting it was regarded as peculiarly happy, and was widely adopted by other writers. After further investigations and more mature reflection, he has recently re- stated his views, and has kindly furnished the revised essay for insertion in this volume. ‘* Prof. A. Bain, the celebrated Psychologist of Aberdeen, who has done so much to advance the study ofmind in its physiological relations, prepared an interesting lec- ture not long ago on the ‘Correlation of the Nervous and Mental Forces,’ which was read with much interest at the time of its publication, and is now reprinted as a suitable exposition of that branch of the subject. ‘These two essays, by carrying out the prin- ciple in the field of vital and mental phenomena, will serve to give completeness and much greater value to the present volume.”’ ‘‘The great physical generalization called ‘ The Conservation of Energy’ is in an intermediate state. It is so new that all kinds of false ideas are prevalent about it; it is so exact that these cannot be tolerated ; and thus its circumstances are such as to make so thorough and simple a treatise as this, by Prof. Balfour Stewart, a boon to science and the world at large. ‘« The scheme of the book is simple, as is naturally the case when the subject-mat- ter comprehends but one single law of Nature and its manifestations. ‘The first two chapters are devoted to the consideration of mechanical energy and its change into heat, Prof. Stewart rightly devoting special attention to these two forms of energy, compared with which all others are insignificant in practical, if not in theoretical, im- portance. The remaining forms of energy are then explained, and the law of its con- servation is stated, and its operation traced through all varieties of transmutations. An historical sketch of the progress of the science and an examination of Prof. Thomson’s correlative theory of the ‘ Dissipation of Energy ’ follow; and the work concludes with a chapter on the ‘ Position of Life,’ which is closely connected with a well-known essay written some years ago by Prof. Stewart and Mr. Lockyer. The style is all that it should be; it is difficult to understand how so much information can be contained in so few words. Prof. Stewart could not have been nearly so successful in this respect had he been in any degree a pedant. No such writer would permit himself to use the quaint language and still quainter similes and and illustrations that make the book so readable, and yet there is scarcely one that is out of place, or illegitimately used, or likely to mislead.” —Saturday Review. D. APPLETON & CO., Publishers, 549 & 551 Broadway, N. Y. ? 4 : : DESCRIPTIVE SOCIOLOGY. = —_ 06 8 Mr. Hersert SPENCER has been for several years engaged, with the aid of three educated gentlemen in his employ, in collecting and organizing the facts concerning all orders of human societies, which must constitute the data of a true Social Science. He tabulates these facts so as conveniently to admit of ex- tensive comparison, and gives the authorities separately. He divides the races of mankind into three great groups: the savage races, the existing civilizations, ‘and the extinct civilizations, and to each he devotes a series of works, The first installment, THE SOCIOLOGICAL HISTORY OF ENGLAND, in seven continuous tables, folio, with seventy pages of verifying text, is now ready. This work will be a perfect. Cyclopedia of the facts of Social Science, independent of all theories, and will be invaluable to all interested in social problems. Price, five dollars. This great work is spoken of as follows: , From the British Quarterly Review. ‘*No words are needed to indicate the immense labor here bestowed, or the great sociological benefit which such a mass of tabulated matter done under such competent direction will confer. The work will constitute an epoch in the science of comparative sociology.” From the Saturday Review. ** The plan of the ‘ Descriptive Sociology’ is new, and the task is one eminently fitted to be dealt with by Mr. Herbert Spencer’s faculty of scientific organizing. His object is to examine the natural laws which govern the development of societies, as he has ex- amined in former parts of his system those which govern the development of individual life. Now, it is obvious that the development of societies can be studied only in their history, and that general conclusions which shall hold good beyond the limits of particu- lar societies cannot be safely drawn except from a very wide range of facts. Mr. Spen- cer has therefore conceived the plan of making a preliminary collection, or perhaps we should rather say abstract, of materials which when complete will be a classified epi- tome of universal history.” From the London Hxeaminer. “Of the treatment, in the main, we cannot speak too highly; and we must accept it as a wonderfully successful first attempt to furnish the student of social science with data standing toward his conclusions in a relation like that in which accounts of the _ Structures and functions of different types of animals stand to the conclusions of the biologist.” A thoughtful and valuable contribution to the best religious literature of the days" ey RELIGION AND SCIENCE. A Series of Sunday Lectures on the Relation of Natural and Revealed Religion, or the Truths revealed in Nature and Scripture. By JOSEPH LE CONTE, PROFESSOR OF GEOLOGY AND NATURAL HISTORY IN THE UNIVERSITY OF CALIFORNIA. 12mo, cloth. Price, $1.50. OPINIONS OF THE PRESS. ‘¢ This work is chiefly remarkable as a conscientious effort to reconcile the revelations of Science with those of Scripture, and will be very use- ful to teachers of the different Sunday -schools.”—Detroit Union. ‘It will be seen, by this 7ésumé of the topics, that Prof. Le Conte grapples with some of the gravest questions which agitate the thinking world. He treats of them all with dignity and fairness, and in a man- ner so clear, persuasive, and eloquent, as to engage the undivided at- tention of the reader. We commend ‘the book cordially to the regard of all who are interested in whatever pertains to the discussion of these grave questions, and especially to those who desire to examine closely the strong foundations on which the Christian faith is reared.’””—Loston Fournal, | ‘¢ A reverent student of Nature and religion is the best-qualified man to instruct others in their harmony... The author at first intended his work for a Bible-class, but, as it grew under his hands, it seemed well to give it form in aneat volume. The lectures are from a decidedly re- ligious stand-point, and as such present a new methcd of treatment.” —Philadelphia Age. ‘‘ This volume is made up of lectures delivered to his pupils, and is written with much clearness of thought and unusual clearness of ex- pression, although the author’s English is not always above reproach. It is partly a treatise on natural theology and partly a defense of the Bible against the assaults of modern science. In the latter aspect the author’s method is an eminently wise one. He accepts whatever sci- ence has proved, and he also accepts the divine origin of the Bible. Where the two seem to conflict he prefers to await the reconciliation, which is inevitableif both are true, rather than to waste time and words in inventing ingenious and doubtful theories to force them into seeming accord. Both as a theologian and a man of science, Prof. Le Conte’s opinions are entitled to respectful attention, and there are few who will not recognize his book as.a thoughtful and valuable contribution to the best religious literature of the day.”—Wew York World. D. APPLETON & CO., Publishers, 549 & 551 Broadway, N. Y. DESCHANEL’S NATURAL PHILOSOPHY. NATURAL PHILOSOPHY: AN ELEMENTARY TREATISE. By PROFESSOR DESCHANEL, of Paris. Translated, with Extensive Additions, By J. D. Everett, D.C. L., F. R.S., PROFESSOR OF NATURAL PHILOSOPHY IN THE QUEEN’S COLLEGE, BELFAST. 1 vol., medium 8vo.. Illustrated by 760 Wood Engravings and 3 Colored Plates. Cloth, $6.30, Published, also, separately, in Four Parts. Limp cloth, each $1.75. Part I. MECHANICS, HYDROSTATICS, and PNEUMATICS. Part IT. HEAT. Part III. ELECTRICITY and MAGNETISM. Part IV. SOUND and LIGHT. Saturday Review. “ Systematically arranged, clearly written, and admirably illustrated, showing no less than than 760 engravings on wood and three colored plates, it forms a model work for a class of experimental physics. Far from losing in its English dress any of the qualities of matter or style which distinguished it in its original form, it may be said to have gained in the able hands of Professor Everett, both by way of arrangement and of incorporation of fresh matter, without parting in the translation with any of the freshness or force of the author's text.” Atheneum. “ A good working class-book for students in experimental physics.” Westminster Review. * An excellent handbook of physics, especially suitable for self-instruction. ... The work is published in a magnificent style; the woodcuts especially are admirable.” Quarterly Journal of Science. “ We have no work in our own scientific literature to be compared with it, and we are glad that the translation has fallen into such, good hands as those of Professor Everett. . . . It will form an admirable text-book.” Nature. “The engravings with which the work is illustrated are especially good, a point in which most of our English scientific works are lamentably deficient. The clearness of Deschanel’s explanations is admirably preserved in the translation, while the value of the treatise is considerably enhanced by some important additions. . . . We believe the book will be found to supply a real need.” 7 D. APPLETON & CO., New York. An Important Work for Manufacturers, Chemists, and Students. A HAND-BOOK OF CHEMICAL TECHNOLOGY. By RupoLfH WAGNER, Ph. D., PROFESSOR OF CHEMICAL TECHNOLOGY AT THE UNIVERSITY OF WURTZBURG. Translated and edited, from the eighth German edition, with extensive Additions, By WM. CROOKES, ERG With 336 Illustrations. 1 vol., 8vo. 761 pages. Cloth, $5.00. The several editions of Professor Rudolph Wagner's ** Handbuch der Chemischen Technologie’? have succeeded each other so rapidly, that no apology is needed in offering a translation to the public. Under the head of Metallurgic Chemistry, the latest methods of preparing Iron, Cobalt, Nickel, Copper, Copper Salts, Lead and Tin and their Salts, Bismuth, Zinc, Zinc Salts, Cadmium, Antimony, Arsenic, Mercury, Platinum, Silver, Gold, Man- ganates, Aluminum, and Magnesium, are described. ‘The various applications of the Voltaic Current to Electro-Metallurgy follow under this division, The Preparation’ of Potash and Soda Salts, the Manufacture of Sulphuric Acid, and the Recovery of Sul- phur from Soda-Waste, of course occupy prominent places in the consideration of chemical manufactures. It is difficult to over-estimate the mercantile value of Mond’s process, as well as the many new and important applications of Bisulphide of Carbon. The manufacture of Soap will be found to include much detail. The Technology of Glass, Stoneware, Limes and Mortars, will present much of interest to the Builder and Engineer. The Technology of Vegetable Fibres has been considered to include the preparation of Flax, Hemp, Cotton, as well as Paper-making; while the applications of Vegetable Products will be found to include Sugar-boiling, Wine and Beer Brewing, the Distillation of Spirits, the Baking of Bread, the Preparation of Vinegar, the Preser- vation of Wood, etc. Dr. Wagner gives much information in folvenne to the production of Potash from Sugar-residues. ‘The use of Baryta Salts is also fully described, as well as the prepa-_ ration of Sugar from Beet-roots. Tanning, the Preservation of Meat, Milk, etc., the Preparation of Phosphorus and Animal Charcoal, are considered as belonging to the Technology of Animal Products. The Preparation of the Materials for Dyeing has necessarily required much space; while the final sections of the book have been de- voted to the Technology of Heating and Illumination. D. APPLETON & CO., Publishers. *, ve we >