THE PACES OF THE HORSE 283 



transports himself from one place to another do not operate 

 according to a unique method and with a constantly 

 uniform velocity. These various modes of progression are 

 designated under the name of faces. 



It is extremely difficult to analyze, by simple observation, 

 the movements which characterize these gaits. Let us, for 

 example, examine the displacements made by the limbs of 

 a horse during that of walking ; if we have no notion of these 

 displacements, it will be, so to speak, impossible to deter- 

 mine in what order they are executed. The sight of the 

 imprints left on the ground by the hoofs is not a sufficient 

 means of demonstration, especially for artists. The noise 

 made by the blows of these limbs, or by the little bells of 

 different timbre suspended from them, are absolutely in the 

 same case. 



Processes enabling us to fix or to register the paces are 

 in every way preferable. Such really exist ; they are : 

 instantaneous photography and those which constitute the 

 graphic method of Professor Marey. The results given by 

 the photograph are certainly appreciable ; but, from the 

 didactic point of view, we give the preference to the graphic 

 method, the general characters and the mode of application 

 of which we now proceed to analyze.* 



It is necessary to understand first of all, in this connec- 

 tion, that which relates to a man's walking pace. 



The method of Professor Marey rests on the following 

 principle : Suppose two rubber globes connected with one 

 another by a tube. If we compress one of these globes, the 

 air which it contains will be driven into the other, and will 

 afterwards return when the pressure has ceased. Nothing 

 more simple, evidently ; but it is necessary to describe it in 

 detail in order the better to comprehend that which follows : 

 The walker who is the subject of experiment is furnished 

 with special shoes (Fig. 115), having thick indiarubber soles, 



* We cannot too strongly recommend the reading of the excellent works 

 which Professor Marey has published, and which have for their object 

 the study of movements, as well as the exhibition of the procedures which 

 he has employed. E. J. Marey, 'La Machine Animale,' Paris, 1873; 

 'La Methode graphique dans les Sciences experimentales,' Paris, 1884; 

 ' Le Vcl des Oiseaux,' Paris, 1890 ; ' Le Mouvement,' Paris, 1894. 



