FORM AND MATERIAL FOR ROADS. 91 



adjoining all the soft, rich, upper surface, and then to 

 form the harder subsoil into a slightly-rounded car- 

 riage-way, with a ditch on each side. Such roads as 

 this have a very hard and firm foundation, and they 

 have heen found not to cut up into ruts, nor to form 

 much mud, even in the wettest seasons. On this hard 

 foundation six inches of gravel will endure longer and 

 form a hotter surface than twelve inches on a raised 

 " turnpike" of soft soil and nmd. 



It frequently happens that the form of the surface 

 increases the quantity of mud in a road, by not allow- 

 ing the water to flow off freely. The earth is heaped 

 up in a high ridge, but having little slope on the top 

 {Fig-. 71), where the water lodges, and ruts are formed, 



Fi£. 71. 



Badly-formed road. 



the only dry portions being on the brink of the ditches, 

 where the water can escape. Instead of this form, 

 there should be a gradual inclination from the centre 

 to the ditches, as shown in Fig. 72. This inclination 



Fis. 72. 



Well-formed road. 



should not exceed 1 foot in 20. On hillsides the slope 

 should all be toward the higher ground, as in Fig. 73. 



Fiff. 73. 



Road for side-hill. 



