A STUDY IN LOCOMOTION. 319 



which serve to record forces, rates of speed, or to note the rhythms 

 and the relations of succession of very complicated movements : 



1. Of the Force of Traction of the Horse, and the best Means of 

 utilizing it. When a carriage is badly constructed and badly yoked 

 the traveler 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 inconve- 

 niences, 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 traveler. 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 improvements, such as the use of softer cushions, things 

 went on thus till the invention of steel springs sucb as are now em- 

 ployed, 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 diminish the force of jolts, transform a sud- 

 den 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 which 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 engi- 

 neers. M. Marcel Deprez has 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 suppressing the 

 shocks which put it out of order and destroy it in a short time. Fi- 

 nally, 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 movements 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 favor- 

 able to a good condition of the road. 



But with non-suspended vehicles, in order thus to shock the pas- 

 sengers, disjoint the carriage, and abuse the road, force is necessary. 

 It is the horse which must supply this ; so that, independently of the 

 useful work which we demand of them, the animal supplies still other 

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



