MOTION. 



479 



By table 13 we find that the 

 duration of the step in leaping 

 is less than in slow walking,* 

 but greater than in running ;f 

 the length of step is much 

 greater than in walking, and 

 may be made greater than in 

 quickest running. As the 

 body swings freely in the air 

 a longer period, and rises to a 

 greater elevation in leaping 

 than in running and walking, 

 it is necessary that the projec- 

 tile force should be made 

 greater, but the time during 

 which the extensor power of 

 the leg acts, although very 

 short, is of intense action ; 



Fig. 271. 



a 1,8 



Fi. 27-2. 



. 



' Figure* desitjned by Weber to illnsfmte the formulas fur leaping. 



hence, it is not easy to regulate the amount 

 of muscular action as in walking and run- 

 ning, and consequently it may be too great or 

 too little for the object in view. The vertical 

 undulations also are much more considerable 

 than in the other modes of locomotion. 



In descending rapidly the sides of steep hills 

 it is much safer to do so by leaping than by 

 running, as in the former mode of progression 

 the foot is placed on the ground at the end of 

 each step in a position favourable for stopping:, 

 which cannot be done in the latter. MM. 

 Weber consider that the study of the laws 

 which regulate the locomotion of man, and of 

 the mechanism by which it is accomplished, 

 will assist mankind in the construction of au- 

 tomatic locomotive machines. Mr. G. Rennie 

 has studied the construction of animals and the 

 principles on which they move with a view of 

 applying them to the locomotion of the steam- 

 boat, on the supposition that animals move in 

 air, in water, with the least expenditure of mus- 

 cular force, an hypothesis which accords with 

 * See Table 8. t See Table 12. 



our views as well as those of M. Dumas, who 

 considers that man is capable of moving and 

 producing a greater mechanical effect, with 

 less expenditure of fuel, than can be produced 

 by any steam-engine hitherto invented. 



In every mode of progression there is a sen- 

 sible increase of action in the circulating and 

 respiratory systems ; but the effect produced on 

 them is much greater in running and leaping 

 than in walking. In the two former cases a vio- 

 lent palpitation of the heart and hurried respira- 

 tory movements are quickly produced, on which 

 account they cannot be very long continued. 

 In running, when four steps are taken in 

 a second, the difficulty of breathing soon 

 causes the pedestrian either to slacken his pace, 

 or what may be most advantageously substi- 

 tuted when it is desirable to continue nearly the 

 same speed, and at the same time preserve the 

 breath, to exchange the running for a leaping 

 movement. In consequence of the deliberate 

 manner in which the steps may be taken in 

 leaping, the breath may be preserved for a longer 

 period, and the action of the heart diminished ; 



