90 MECHANICS. 



yearly cost of the road, including interest on the land, 

 and the cost of repairs, would not usually be more 

 than a tenth part of the same cost for plank, or would 

 not exceed thirty dollars. 



On rail-roads, where the resistance is only about one 

 fifth part of the resistance of plank roads, the dispro- 

 portion between the draught on a level and up an as- 

 cent becomes many times greater. Thus, if a single 

 engine will move three hundred and fifty tons on a lev- 

 el, then two engines will be required for an ascent of 

 only twenty feet per mile, four engines for fifty feet per 

 mile, and six engines for eighty feet per mile. 



Such estimates as these merit the attention of the 

 farmer in laying out his own private farm roads. It 

 may be worthy of considerable eflbrt to avoid a liill of 

 ten or twenty feet, which must be passed over a hund- 

 red times yearly with loads of manure, grain, hay, and 

 wood. The greatly-increased resistance of soft mate- 

 rials, also, is too rarely taken into account. A few 

 loads of gravel, well applied, would often prevent ten 

 times the labor in plowing through deep ruts, to say 

 nothing of the breaking of harness and wagons by the 

 excessive exertions of the team. 



FORM AND MATERIALS FOR ROADS. 



The depth of the mud in common roads is often un- 

 necessarily great, in consequence of heaping together 

 with the plow and scraper the soft top-soil for the raised 

 carriage-way. When heavy rains fall, this forms a 

 deep bed of mud, into which the wheels work their 

 way, and cause extreme labor to the team. A much 

 better way is to scrape off and cart away into the fields 



