454 THE POPULAR SCIENCE MONTHLY. 



of the systems of artificial flight into helicopter ons^ areoplanes, and 

 orthopterons (from bpdog, straight, and irrepov, a wing). The helicop- 

 terons sustain themselves by the aid of screws whose axes of rotation 

 are nearly vertical. They may be made to progress either by these 

 vertical screws or by special screw-propellers. The areoplanes have 

 propelling surfaces which are nearly plane and slightly inclined to the 

 horizon. A horizontal motion is given to these surfaces generally by 

 means of screws. Finall}% in the orthopterons, the propelling organs 

 are surfaces moving in vertical directions, and generally having re- 

 ciprocating motions. In this system are embraced the wings of birds 

 and the moving surfaces of the tails of fishes. 



The knowledge of the resistance of the air appeared to us the 

 only guide by which we could arrive at a thorough understanding of 

 the manner in which a machine could sustain itself by the actions of 

 its propelling surfaces on this fluid. We entered upon an attentive 

 study of several imperfectly-understood points appearing to us of 

 capital importance ; such as the sustaining screw, the aerial inclined 

 plane, and tlie theory of the equilibrium of flying-machines. The 

 screw-propeller was well understood from its eflTects in propelling ves- 

 sels. These researches, which led us to a small number of very simple 

 general laws, permitted us to determine the manner of action and the 

 proportions of the machines which we desired to construct. 



It remained to find a motor the easiest of application. Wood, 

 whalebone, and steel, give forces which are at a minimum when re- 

 ferred to their weight ; caoutchouc is much more powerful, but the 

 framework necessary to resist its violent tension is necessarily quite 

 heavy. We then conceived the idea of using the elasticity of the 

 torsion of caoutchouc, which finally led to an easy, simj^le, and eftec- 

 tive method of constructing the models of flying-machines. 



We applied the new motor first to the helicopteron, after having 

 previously investigated the curious and valuable actions of caoutchouc 

 when subjected to various successive torsions. In April, 1870, we pre- 

 sented models to M. de la Landelle which rose in flight to more than 

 fifteen metres, hovering and fluttering through large inclined circles, 

 and sustaining themselves during more than twenty seconds. 



The great superiority of these results over those obtained with 

 preceding helicopterons encouraged us to apply our motor to other 

 systems of artificial flight. On the 18th of August, 1871, in the pres- 

 ence of the Society of Aerial Navigation, we succeeded in making an 

 areoplane fly with various velocities and in difierent directions, around 

 one of the circles of the garden of the Tuileries. The success of this 

 machine in its ascending motions and in its perfect equilibrium gave 

 the first successful exhibition of a machine on the areoplane type. 



Measured directly, and irrespective of any hypothesis, the foi-ce 

 required to sustain and propel the areoplane and the helicoptei-on 

 proved to be relatively moderate, and did not approach the fabulous 



