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This remarkable difference points out the great advantage of 

 fprings in rough roads; an advantage which might be obtained 

 for he ivy waggons as well as for other carriages by a judicious 

 application of the fame means. 



It has but feldom happened that the modcfly of theory has 

 promifed lefs than what has been verified by experiment ; but 

 it appears from the Memoirs of the French Academy that the 

 idea of applying fprings to carriages had occurred to Monfieur 

 Thomas in the year 1703, who has given a drawing of a car- 

 riage conftru6led upon this principle many years before it was 

 attempted to be put into execution. So little hope had he 

 entertained of fuccefs, that he exprefsly mentions it as a theory 

 which could not be reduced to practice ; he had, however, no 

 notion of applying fprings to facilitate the draught, but merely 

 for the convenience of the rider-, and I apprehend that it is not at 

 prefent commonly imagined that fprings are advantageous for this 

 purpofe ; nor would it at firft fight appear credible, that upon a 

 rough paved road, fuch as are common in Chefhire and other 

 parts of England, a pair of horfes could draw a carriage mounted 

 upon fprings with greater eafe and expedition than four could 

 draw the fame carriage, if the fprings and braces were removed, 

 and the carriage bolted faft down to the perch. I tried fome other 

 experiments with the fame apparatus to compare long and fliort, 

 high and low carriages. I have loft the particular refults of each 

 experiment, but I am well afiTured that the preference which has 

 lately been given in England to high carriages is ill-founded ; 

 that upon fmooth roads the height of the carriage is a matter 

 of indifference as to the draught, and that in rough roads it is 



confidcrably 



