March 13, 1879] 



NATURE 



439 



V hat crossings, what training give reason to expect still 

 more speed ? 



Lastly, as to what is called the exterior of the horse, 

 and his varied paces, specialists have for long devoted 

 themselves to this department. The horseman is trained 

 to distinguish between these different paces, to correct by 

 the education of the horse those which seem to him de- 

 fective, to fix by habit those which give to his mount more 

 pheasant reactions or a much greater stability. The artist, 

 in attempting to represent the horse, seeks to transfer his 

 attitudes more and more faithfully, to express better and 

 better the force, the suppleness, and the grace of his 

 motions. 



These questions, so complicated, I wish to bring before 

 you by a new method, and I hope to show you that the 

 graphic method makes light of difficulties which seem in- 

 surmountable, discerns what escapes the most attentive 

 ob3er\'ation ; finally, it expresses clearly to the eyes, and 

 engra\-es upon the memory the most complicated notions. 

 The graphic method was almost unknown twenty-five 

 years ago ; to-day it is wide-spread. Thus, in almost all 

 countries, recourse is had to the employment of graphic 

 curves as the best mode of expression to represent clearly 

 the movement of administrative, industrial and com- 

 mercial statistics. In all observatories apparatus known 

 as r^gistering or recording, trace on paper the curves of 

 variation of the thermometer, the barometer, rain, wind, 

 and even atmospheric electricity. Physiology utilises 

 still more largely recording apparatus ; but I shall only 

 require to show you a very small number of these instru- 

 ments, those which serve to record forces, rates of speed, 

 or to note the rhythms and the relations of succession of 

 v£ry complicated movements. 



I. Of the Force of Traction of the Horse, and the best 

 Means of Utilising //.—When a carriage is badly con- 

 structed and badly yoked the traveller is jolted, the road 

 is injured, the horse is fatigued more than is necessary, 

 and is often wounded by parts of the harness. Science 

 and industry have long sought to discover these incon- 

 veniences, to find out their causes in order to get rid of 

 them. But it is only in our own time that great progress 

 has been made in this respect. When we complain of 

 being jolted in a humble cab, we ought to go back in 

 thought to the time when people knew nothing of the 

 hanging of carriages. No roughness of the road then 

 escaped the traveller. A Roman emperor mounted on 

 his triumphant chariot was, in the midst of his glory, as 

 ill at ease as the peasant in his cart. Except some im- 

 provements, such as the use of softer cushions, things 

 went on thus till the invention of steel springs such as 

 are now employed, for the leather braces of old-fashioned 

 carriages still left much to desire. 



Does this mean that the present mode of suspending 

 carriages by four and even eight springs is the final step 

 of progress ? Certainly not. Our present springs dimi- 

 nish the force of jolts, transform a sudden shock into a 

 long vibration ; but the perfect spring ought always to 

 maintain a constant elastic force, to allow wheels and 

 axles all the vibrations w^hich the ground demands of 

 them, without allowing any of these shocks to reach the 

 carriage itself. The search for this ideal spring has 

 engaged the attention of one of our most eminent 

 engineers. M. Marcel Deprezhas found happy solutions 

 to the problem of perfect suspension ; he will, doubtless 

 soon apply these in practice. 



A good suspension also saves the carriage by suppress- 

 ing the shocks which put it out of order and destroy it in 

 a short time. Finally, suspension saves the wheel itseLf. 

 On this subject let me recall a remarkable experiment of 

 General Morin. On a high road, in good condition, he 

 drove a diligence with four horses at the trot, and laden 

 with ballast instead of passengers. The springs of 

 the vehicle were raised so that the body rested on the 

 axles. After the diligence had passed and repassed a 



certain number of times, it was found that the road on 

 which it was running was notably deteriorated. The 

 springs of the carriage were replaced and the same move- 

 ments were repeated on another part of the road ; the 

 marked deterioration was no longer produced. It is thus 

 clearly proved that a good suspension is favourable to a 

 good condition of the roads. 



But with non-suspended vehicles, in order thus to 

 shock the passengers, disjoint the carriage, and abuse the 

 road, force is necessary. It is the horse which must 

 supply this ; so that, independently of the useful wor.c 

 which we demand of them, the animal supplies still other 

 work which gives rise to a multitude of shocks, and has 

 only injurious effects. The employment of suspending 

 springs has rendered the double service of suppressing 

 injurious vibrations and of collecting into a useful form 

 all the work which they represent. 



Is this all "i Do there not remain, even with the best 

 carriages, other vibrations and other shocks which must 

 be pursued and destroyed in order to render more perfect 

 the conditions of traction ? You have all experienced, at 

 the moment of the sudden start of a carriage, and even 

 at each stroke of the whip on a living horse, horizontal 

 shocks which sometimes throw you to the bottom of the 

 carriage. In a less degree, shocks of the same kind are 

 produced at each instant of traction, for the speed of the 

 horse is far from being uniform, and the traces are sub- 

 jected to alternate tension and slackness. Here are 

 veritable shocks which use up part of the work of the 

 horse in giving only hurtful effects which bruise and 

 contuse the breast of the animal, injuring his muscles, 

 and, in spite of the padding of the collar, sometimes 

 wounding him. To prove the disadvantages of this kind 

 of shocks, some experiments are necessary. I have 

 borrowed one from Poncelet ; it is easily made, and any 

 one may repeat it. I attach a weight of 5 icilos to the 

 extremity of a small string ; taking hold of the free ex- 

 tremity of this, if I gently raise the weight, you see that 

 the cord resists the weight of 5 kilos and holds it sus- 

 pended. But if I attempt to raise the same weight more 

 rapidly, I bruise my fingers, the cord breaks, and the 

 weight has not budged. The effort which I have made 

 has been greater than the preceding, since it has ex- 

 ceeded the resistance of the cord ; but the duration of 

 this effort has been too short, and the inertia of the 

 weight not being overcome, all my exertion has been 

 expended in injurious work. If, instead of an inexten- 

 sible cord, I had attached to the weight a cord a little 

 extensible, the sudden effort of elevation which I made 

 would have been transformed into an action more pro- 

 longed, and the weight would have been raised without 

 breaking the cord and bruising my fingers. To render 

 the phenomenon more easy of comprehension, I shall 

 make a new experiment under conditions a little different. 



You see on a vertical support (Fig. i) a sort of balance- 

 beam, which bears on one of its arms a weight of 100 

 grammes, on the other a weight of 10 grammes sus- 

 pended at the end of a cord one metre long. Between 

 these two unequal weights the beam is maintained by a 

 spring-catch, which prevents it from falling to the side of 

 the heavier weight, but which, on the other han^, 

 permits the beam to incline in the opposite direction, if 

 we bring to bear on the end of the cord an effort greater 

 than the weight of 100 grammes. But, by letting the 

 smaller weight fall from a sufficient height, at the moment 

 when this reaches the end of its course, it will stretch the 

 cord which holds it, and will develop what is called a vis 

 viva, capable of raising the weight of 100 grammes to a 

 certain height ; but this elevation will only take place on 

 condition that the application of this force does not give 

 rise to a shock. If the cord which sustains the weight of 

 100 grammes is inextensible, and if that which bears the 

 weight of 10 grammes is the same, at the moment of the 

 fall of the latter, you will hear a snap ; a shock agitates 



