306 



FARM DEVELOPMENT 



Figure 181. Roadside ditches with vertical 

 outer edges. 



if they must be often renewed. Thus, in making a 

 macadam road, as in Figure 179, limestone is suitable 

 for the lower two-thirds of the bed of stone, but harder 

 rock, as trap rock or granite, on the surface will longer 

 endure the wearing of wheels and teams. Some 

 kinds of gravel, likewise, are very much more valuable 



for the upper few inches 

 of surface than are other 

 kinds. Gravel made up of 

 granite and trap rock will 

 wear very much longer than 

 gravels composed of lime- 

 stone or other soft stones. Bricks differ in hardness 

 and durability. Paving brick made in certain localities 

 have proven so superior over the brick made in many 

 other localities that 

 they are shipped hun- 

 dreds of miles for 

 street and road paving. 

 Ease of repairing is 

 also an important prop- 

 erty of the road sur- 

 face. In this connec- 



tion, attention mUSt be Figure 182. In throwing earth from roadside 



t . . ditch to the center of the roadway with the re- 



jnven in tne Selection versible road machine the operator can make a 



. ditch with vertical outer bank, leaving the ditch 



Of material for SUrfaC- and earth as shown by the line A D; slanting outer 



banks, as at B F; or rounded bank, as at C E. 



ing the road to the 



ease of getting material for repairs. Materials for 

 construction brought long distances at much expense 

 are sometimes doubly expensive for repairing if the 

 same material must be brought at a disadvantage. 

 There are sometimes less suitable materials near at 

 hand which can easily be secured for renewing broken 

 surfaces and in the end are more practical for the 

 original construction than are the somewhat better 

 kinds which must be brought long distances. 



