210 ANIMAL MECHANISM. 



vertical tractions of a thread attached to (.lie wing of tlio bird, 

 and the other by the horizontal tractile force of a second 

 thread also fastened to its wing, \ve can verify the experiment 

 which has furnished us with the trajectory of this organ, and 

 obtain \\ith much greater accuracy the curve illustrating its 

 movements. This \ve have perfectly succeeded in doing, as 

 we shall show further on. 



But this is not all that we wished to obtain. We might 

 have made the bird carry the apparatus which we have just 

 described, and put it in communication with the registers by 

 means of tubes, as in the experiment represented in fig. 99. 

 lint while seeking to render the analogies of the movements 

 of flight perfect, we wished also to discover a plan which 

 would be equally applicable to the living bird, and to every 

 kind of machine intended to represent artificially aerial loco- 

 motion. 



In this project we must endeavour to copy Nature in her 

 functions, as the artist does in her form. We must give more 

 rapidity to movements which are too slow, and render those 

 slower which are too rapid, until they have absolutely the same 

 characters and the same mechanical effects as those of the 

 bird. 



This incessant comparison requires us to place ourselves 

 under new conditions. Hitherto, our analytical studies have 

 been directed to a bird flying at liberty ; for since we have 

 never been able to imitate flight exactly by mechanical 

 methods, it would be impossible to leave an artificial instru- 

 ment to itself; it would be broken at each experiment. 



The comparison of the movements of tlio bird with those 

 of imitative instruments does not require those movements to 

 be effected under the conditions of free flight. Provided that 

 the bird, although restrained in its movements, should flap 

 its win^s with the intention of flying, wo shall bo able to 

 study these muscular actions with reference to their characters 

 of force, extent, and duration. A bird suspended by a cord 

 and allowed to flap its wings might, for example, bo com- 

 pared with an artificial apparatus suspended in the same 

 manner. 



Wo have tried a less imperfect mode of suspension which 



