5i8 



NATURE 



\Oct. 29, 1874 



otherwise horizontal plane to become directed slightly 

 backwards, and in its ascent the same cause directs it 

 somewhat forward. But an inclined plane striking the 

 air has a tendency to move in the direction of its own 

 inclination ; consequently, both in the down and up 

 stroke of the wing, it tends to move forward at the same 



time. " But this deviation cannot be effected without the 

 nervure being slightly bent. The force which causes the 

 wing to deviate in a forward direction necessarily varies 

 in intensity according to the rapidity with which the 

 organ is depressed. Thus, when the wing towards the 

 end of its descending course moves more slowly, we shall 



see the nervure, as it is bent with less force, bring the 

 wing backwards in a curvilinear direction. Thus we 

 explain naturally the formation of the descending bran ch 

 of the 8 passed through by the wing ;" and the same 

 theory applies to the ascending branch of the figure. 



Acting upon the suggestions of his theory, Prof. Marey 

 has constructed artificial wings, which are planned and 

 move upon the same principle as those of insects. 

 He has not succeeded in making a flying machine, 

 it is true ; this, however, is not from any fault in the 

 wings, but because it is impossible to obtain an engine 

 sufficiently light to drive them. He has, however, con- 

 trived an apparatus which, when the motor power is 

 supported, is capable of moving horizontally with rapidity, 

 of rising and of falling, just like an insect ; and, what is 

 more, when propelled by a simple up and down move- 

 ment, the tips of the wings describe a figure of S of their 

 own accord, as they ought to do upon the theory which 

 led to their construction. 



The mechanism of the flight of birds is a problem far 

 more difficult to master than that of insects. The size of 

 the subjects of experiment, and the comparative slowness 

 of the movements of their wings, remove them beyond 

 the reach of the optical and direct graphic method pre- 

 viously employed. Each stroke of the wing has to be 



recorded through the interventionof a complicated system 

 of tubes and levers, as fragile as they arc delicate, and as 

 expensive, as they are liable to be broken. Movements 

 in a single plane are capable of being transferred to paper 

 with comparative ease, but when they arc not so limited, 

 and may be in any direction, the necessary complication 

 of the recording machinery becomes immense. The 

 number of little details which have to be continually 

 remembered, and the oft-repeated futile attempts which 

 have to be allowed for, makes Prof. Marey's success in 

 his investigations a matter of more than ordinary surprise. 

 He has mastered the whole subject, having by separate 

 and by combined check methods demonstrated what is 

 the rapidity, direction, and inclination of the wing of the 

 bird in every part of its course. Further than this, he 

 has shown what effects the stroke has on the movements 

 of the body of the bird, and this by a very ingenious new 

 method. The way in which the author invents means for 

 reproducing and originating any quality of movement he 



may want to develop, must be a source of adniiration and 

 almost astonishment to all readers of his work. 



Fig. 5 shows a buzzard saddled with the machinery 

 which, by means of the two tubes running downwards 

 from it, transmits the vertical and horizontal movements 

 of its wing to the recording apparatus, which is not repre- 

 sented. In the study of the more intricate points the 

 necessary instruments are so heavy that the whole bird 

 has to be partially supported. This is done by attaching 

 it to the extremity of a long lever which revolves, with 

 scarcely any friction, on a pivot. This is found not 

 seriously to interfere with the normal flight of the bird. 



Most of the facts made out by the employment of 

 this apparatus are shown in Fig. 6, which is con- 

 structed to illustrate the inclination of the plane of the 

 wing with reference to the axis (./i') of the body of the 

 bird during flight. The direction of tlie movement of the 

 wing is from // to A-<\ It shows " that the wing during 

 its ascent assumes an inclined position, which allows it 



