666 On the Advantage of Employing 



from customs which are consecrated by fashion ; and, 

 on my return to Paris, I had made for my carriage 

 wheels with broad felloes. I have now for two months 

 used them daily, and I am so well pleased with them 

 that I feel it to be a duty to make known the results of 

 this experiment. The carriage, which is a two-seated 

 coach, has become incomparably more comfortable 

 and more agreeable than it ever was before ; and I have 

 just discovered, by comparative experiments of which I 

 will give an account, that it has become more easy to 

 draw, and that it is less tiresome for the horses. 



Having kept the old wheels, which are not worn out, 

 and also by a happy chance a still older set, which are 

 yet narrower, I had my carriage arranged in such a 

 manner as to be able to measure exactly the force 

 employed by the horses in drawing it ; and, using the 

 three kinds of wheels alternately, always going over 

 the same road at the same rate of speed, and with the 

 same amount of load, I have been able to determine, 

 in a perfectly decisive manner, not only which of the 

 wheels roll the easiest, but also in every case how 

 much less is the force exerted in drawing with one 

 set than with the others. 



The method by which I estimated the force em- 

 ployed was as follows : A bar of beech- wood, 29 inches 

 long, 4 inches wide, and i inch thick, moving without 

 sensible friction in a groove, is placed flat upon the 

 forward axle of the carriage, in the direction in 

 which it is to travel. At the two ends of this bar 

 of wood are two iron hooks. To the hook in front 

 is fastened a splinter-bar, and to the ends of this bar 

 the whippletrees are attached. To the other hook is 

 fastened the end of a stout rope, the other end of which 



