NEW RESULTS IN ANIMAL MOVEMENTS. 451 



ished considerably, which fact showed an increase in the resistance 

 of the air. 



MM. Planavergne claim the priority of the theoretic idea which I 

 have enunciated, and show, in fact, that they had published, some 

 years since, a memoir, in which this theory is explicitly stated. How- 

 ever, these authors have furnished no experimental demonstrations of 

 their views ; consequently, it has appeared to me that it would be in- 

 teresting to continue the researches which I had begun, and to deter- 

 mine, as accurately as possible, on one hand, the phases and variable 

 conditions of the resistance of the air to a moving body which dis- 

 places it with a uniform motion ; on the other hand, to find the increase 

 of the resistance of the air under the wings of an apparatus which is 

 transported with determinate velocities. 



First Series op Experiments. Determination, of the variable 

 and constant resistatices opposed by the air to a moving body which 

 displaces the air with a uniform motion. 



In a solid framework, which glides easily on an horizontal plane, I 

 placed a light screen, with its plane vertical and perpendicular to the 

 direction of its motion. This screen turns around an horizontal axis ; 

 and an arm attached to it is charged with an additional weight until 

 perfect equilibrium is established between the arm and the screen itself. 

 This having been done, we have no fear of the inertia of one or an- 

 other part of the system causing the screen to revolve around its axis 

 at the beginning of its motion of translation. If such a movement 

 of rotation does take place, we must attribute it to the resistance 

 offered by the air. 



Behind the screen is placed a little manometric apparatus, which 

 communicates, by means of a tube, with a drum, having a lever rest- 

 ing on its membrane. 1 



Fig. 3. 



The apparatus having been thus arranged, we give to it a uniform 

 motion of translation which lasts half or a quarter of a second, and 

 we obtain on a revolving cylinder the above trace of the point of the 

 writing-lever attached to the membrane of the recording drum. 



When the screen is at rest, the apparatus traces an horizontal line 



1 For a description of Marey's manometric apparatus, the reader is referred to 

 "Animal Mechanism," published in the "International Scientific Series." 



