1 1 6 On the liejijtance experienced hy 



Seclion 2. 



The roads and ways on which loaded carriages are drawft 

 from one place to another by horfes, oxen, and other ani- 

 mals, are fo different in their nature, and the impediments 

 which the moving power has to overcome are fo numerous, 

 that, on the firft view, it appears very difficult to find general 

 formulae to indicate the refinance for every given kind of 

 road, carriage and loading, and to determine the circum- 

 itances under which the one kind of carriage is to be pre- 

 ferred to the other. However, when we feparate from con- 

 ftant impediments the aclion of which is nearly uniform, 

 and which, properly fpeaking, characterize the nature of the 

 way, but without excluding them from our refearch, thofe 

 which occur on every road, but only occasionally, and which, 

 confequently, can be overcome by a momentary exertion of 

 the moving power, among which may be included (ingle 

 eminences and hollows, iuch as ridges, flones, channels, 

 holes, pavements, bridges, &c; all the different kinds of 

 roads may be reduced to the three following dalles : 



lit, Solid and fmooth, to which belong all level as well as 

 inclined roads, crooked and ftraight; alfo hollow roads, with 

 folid, broad, fmooth ruts : in a word, all roads the furface of- 

 which is neither rugged nor yields to the imprellion of the 

 wheels. 



ad, Solid and uneven, which do not fuffer the wheels to 

 fink into them, but which, by their inequality, prefent a 

 pretty uniform reliftance. In this clafs are comprehended 

 rough rugged roads, interfperfed with ridges of rock, paved 

 roads, and roads in which parts are covered with timber and 

 the trunks of trees. 



3d, Soft fmooth roads which yield to the impreffion of the 

 wheels, fuch as marlhy or clayey roads, or roads covered with 

 ibft earth, land, Hints, or fmall ftones. 



Section 3. 



As all roads, either in whole or in part, are comprehended 

 in one of the above claifcs, I ftiall examine them according 

 to tliefe principal diviflons, and determine for each in parti- 

 cular the reliftance experienced by four as well as by two- 

 wheeled carriages, and point out the conditions under which 

 the one kind of carriage is to be preferred to the other for 

 each kind of road. It appears, however, that a diflincYion 

 ought to be made in regard to each of thefe three dalles \ 

 that is to fay, whether the road be horizontal or inclined, 

 fmooth or covered with fmall eminences, new or worn into 



£ circular 



