132 



ANIMAL MECHANISM. 



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

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



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

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

 energy, the two legs raise the body, and then let it fall again at 

 the moment when they bend and prepare to act afresh. 



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

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

 elevations of the body coincide with the 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. 



Fig. 33.— D, series of hops on the right foot. The duration of the time 

 of suspension remains evidently constant, even when that of the pressure 

 of the foot 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 RHYTHM IN DIFFERENT MODES OF 

 PROGRESSION. 



Among the 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. We 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 



