relative to Experiments on Wheel- carriages. 89 



The carriage loaded at lotlom carried 1579 lbs. 

 The carriage loaded at top carried 1505 lbs. 



Both carriages were then tried with the springs in action ; but 

 no difference appeared. 



From all this 1 conclude, as far as my experience goes, that, 

 cceterit paribus, there is very little difference ?w drnjt bttween 

 long and short, and between high and low carriages. 



It may be remarked, that the advantage of springs did not 

 appear to be so great in those four-wheeled carriages as in the 

 experiments on two-wheeled carriages, which I have formeriv 

 mentioned. This arose from the weight in the four-wheeled 

 carriages not being heavy enough to bend the elliptic springs, 

 upon which they were supported, with sufficient facility ". 



Comparison of Roads. 



Two roads were formed, one of loose gravel, the other of 

 broken stone. 



The carriages without springs were drawn by horses attached 

 to the peirameter, one running on the loose gravel, the other 0:t 

 the broken stone ; the former having an additional load of seven 

 hundred weight. 



The second carriage running on broken stone, carrying four 

 hundred weight, besides the weight of the carriage, wheels, &:c. 

 They kept nearly together. 



The same carriages were made to run, one on the broken 

 stone, the other on the well made pavement of the court. 



The carriage on the broken stone carried . . . . 5 cwt. 

 The ditto on the pavement carried IJcwt. 



The latter preceded the carriage running on the broken stone. 



The difference between pavement and a road of broken stones, 

 in this experiment, however enormous it may appear, corre- 

 sponds with others which I have repeatedly tried. If, however, 

 the stones are broken sufficiently small, not larger than an inch 

 and half diameter, they will oppose no very great obstruction to 

 the motion, either of a horse or of a carriage. 



It is therefore of great consequence, in making a road, to have 

 the stones broken small ; and this may be effected by purchasing 

 broken stones l)y measure, and not by weight. For workmen 

 may be soon convir.ced, by the evidence of their senses, that it 

 is for their interest to break stones small, when they are paid 

 for them by measure, as the additional labour which is necessary 



* It was noi th .iiiilit cxpRdient to try tlic patience of the spectninrs 'ly 

 a reiteration of experiments, wliich rKjuircd coiisidci'nble time for rai-li 

 rtpetition. Indeed, experiments of tins sort refjuiic more lime ami a 

 greater attention to ininutite tliun are suitable to a public exliiliition. 



for 



