Oct. 22, 1874J 



NA TURE 



499 



The upper of the two portions of Fig. 3 represents a 

 series of leaps with the feet together, whilst the lower is 

 the notation of the hop on the right leg, in which, from 

 fatigue, the duration of the time of contact with the 

 ground increases ; it will be observed that the time of 

 suspension, nevertheless, does not vary. All these dia- 



grams are so instructive in themselves that they need no 

 fmther detailed explanation. 



Fig. 4 will give an idea of the instrument employed in 

 studying the complicated problem of quadrupedal action, 

 in which it will be seen that the movements of each foot 

 communicate, through elastic tubes, movements to the 



levers of the recording apparatus held in the hand of the 

 rider. In interpreting the tracings thus obtained into the 

 musical notation above employed to describe the different 

 rhythms of human progression, the only thing necessary 

 is to introduce a second pair of bars below that previously 

 employed, to represent the hind feet. A diagram like 

 Fig. I is the result. Before the introduction of this 

 graphic method, the action of the horse, which used to 

 be an endless subject of dispute, was made out from the 

 imprint of the shoe-marks left in soft ground ; this, how- 

 ever, varies for any given action with the rapidity of 

 movement and the size of the animal which forms the 

 subject of experiment. 



As we explained not long ago (NATURE, vol. x. p. 

 39), according to the work before us, the action of the 

 horse in walking, we need not discuss that step on the 

 present occasion. It is by far the most complicated of 

 the movements. The trot is much more simple, being a 

 double instead of a quadruple action ; the opposite fore 

 and hind feet striking the ground simultaneously. There 

 is also an " irregular trot," which is frequently met with, 

 and depends on a lag in the rction of the hind limbs. 



" .Several different paces, the common character of 

 which is that irregular impacts return at regular intervals, 

 are comprehended under the gallop." There is the 

 gallop in two, three, and _/i)«r times, so called according 

 to the number of sounds heard in each completed pace 

 Fig. 5 gives the notation of the gallop in three-time, 



which is the most common ; A indicating the time, and 

 B indicating the number of feet which support the body 

 at each instant of the step. From it the left hind-foot is 



seen to reach the ground before any of the others, and to 

 produce the first sound : the second is caused by the simul- 

 taneous impact of the right hind and left fore feet ; and 

 the third by the right fore-foot, which the animal always 



places forward to commence with. The similarity 

 between this pice and that of children "playing at 

 horses " can be leadily seen by comparing this figure 

 with Fig. 2. The gallop in four-time differs from that 

 just described, in that the impacts of the hind legs are 

 slightly delayed, which causes the two feet, which in 

 three-time strike the ground simultaneously, to do so one 

 after the other, the right hind one after the left fore, so 

 that the single sound is duplicated. 



The full gallop is so violent an action that the delicate 

 instruments employed in analysing the previous move- 

 ments have to be dispensed with, and a more substantial 

 apparatus employed. The rider, instead of carrying it in 



his hand, has it tied, as a knapsack, on his back, and he 

 sets the recording watchwork in motion with his teeth. 

 Notwithstanding the difficulties of the experiment, very 

 successful tracings have been obtained, which show that 

 the full gallop is really a gallop in four-time, in which, 

 although the fore-feet hit the ground with a fair interval, 

 the hind feet hit it nearly simultaneously. The time of 

 complete suspension is extremely short. 



Besides the actual and relative durations of the diflcrent 

 paces. Prof Marey's instruments are so constructed as to 

 record also the rise and fall of the body of the horse 

 during each. This point is of particular interest, as it 

 explains the varying degrees of comfort to the rider in 



