110 ANIMAL MKCIIAXISM. 



opposite directions. Thus, the momentum (M.Y.) is equally 

 divided between the two projectiles, .so that the mass of the 

 cannon and of its carriage, multiplied by the velocity of the 

 recoil which is commuuicuted to it, is equal to the mass of 

 the projectile multiplied by the velocity of propulsion which 

 it receives. As the cannon weighs much more than the ball, 

 the velocity of its recoil is much loss thaii that commuui- 

 cated to the projectile. 



As to the u-iirk developed b} T tlie powder against the cannon 

 and against the ball, it is divided very unequally between 

 these t \\ o masses. 



In fart, the work produced by an active force being pro- 

 portional to the square of the velocity of the mass in motion 

 (ils formula is '^'), calculation shows that this work, when 

 the piece weighs 300 times more than the ball, would be 300 

 t lines greater for the ball than for the cannon. 



We shall return to these questions, when in considering the 

 particular kinds of animal motion, we enter on the investiga- 

 tion of human locomotion. 



CHAPTER II. 



TKKRKSTKIAL LOCOMOTION (BIPIiDS). 



Choice of certain types in order to study terrestrial locomotion - Human 

 locomotion Walking Pressure exerted on the ground, its duration 

 and intensity Re-actions on the body during walking Graphic 

 nirtlmd of .studying them Vertical oscillations of the body 

 Jlnri/Diital oscillations Attempt to represent the trajectory of the 

 pnlii.s Forward movement of the body - Inequalities ol ils velocity 

 during the time occupied by a pace. 



ACT OF WAI. ICING IN MAX. 



TM K types of terrestrial locomotion are so various that wo 

 must, fur a time at least, confine ourselves to the study of the 

 most, important among them. For locomotion among liipeds 

 we \\ill take as a type that of man. The horse will be chosen 



