ROADS 



205 



it had a comparatively flat crown. The English roads built 

 somewhat later were entirely of earth, and in order to be at 

 all passable in wet weather they were given great convexity. 





fw*^ Crown 



fin. per ft 



Natural ground feve/- 



Fig. 179. Cross section of a properly shaped loam road 



Kinds of roads. Roads are known under different names 

 according to the material used in their construction. 



Loam. A loam road (Fig. 179) is graded to the proper 

 shape and has a cross section of such material as is available. 



Clay. A clay road is graded and the surface covered with 

 a coating of clay either hauled from a distance or taken out 

 of the side ditches. 



/ "per // 

 'crown 



0/7 



+ C 



OS 



Fig. 180. Cross section showing methods of drainage. A roadbed should 

 be properly drained regardless of the nature of the surfacing. On land that is 

 thoroughly drained a tile at A or B may. be sufficient. On a new road it is 

 desirable to place a tile drain at C, but on an old road this may become very 

 expensive because of the difficulty in digging. In wet, heavy soils or for wide 

 roadways tile should be placed at both A and B. If the tile is placed only on one 

 side of the road, it should be on the side from which the water is coming, in 

 order to avoid seepage. If water is permitted to pass under the roadbed, it will 

 be raised by capillary action and soften the surface, causing the road to settle. 



Gravel. A gravel road is graded and then covered with a 

 coating of gravel. The gravel layer will vary from 4 to 10 



