132 ANIMAL MKCIIAMSM. 



we get tliroo tracings at once ; those of the pressures of the two 

 feet, ami that of the re-actions ; these furnish fig. 32. 



We sec here that the maxima of the curve of re-actions 

 (line R) coincide with the pressures. Thus, ly their united 

 energy, tlie t\v> legs raise the body, and then let it fall again at 

 tlie moment \vlien they bend and prepare to act afresh. 



Hopping n one foot gives the tracings (fig. 33) which 

 only consist in the pressure and rise of a single foot. The 

 elevations of the liody coincide with tlie step-curves In fact, 

 when the speed of the leap is lessened, it is prolonged more 

 especially at the period of the pressure of the foot on the 

 ground, that of suspension remaining very nearly constant. 



Fio 33. D, series of hup* on the right foot. The duration of the time 

 of Mi*|H'ii.siiiii remains evidently OOILataut, even when tliutot'the pressure 

 of the loot varies. 



In certain species of animals, successive leaps constitute 

 the ordinary mode of locomotion ; it will be interesting to 

 study by the graphic method the various paces of these 

 animals. 



NOTATION OF KHYTIIM IN DIFFERENT MODES OF 

 PBO6BE8SIOM. 



Among tlie characters of various modes of progression, it 

 is the rhythm of the impact of the feet which is the most 

 striking. The strokes of the feet upon the ground give rise 

 to sounds, the order of whose succession is sufficient for a per- 

 son with an ear accustomed to them to recognise the kind of 

 pace which originates them. Wo will, therefore, endeavour 

 to establish the classification of the various paces by attending 

 to this order of succession. 



In order to give the figure of each of these rhythms, we shall 

 employ the musical notation, modified so as to furnish at the 



