2IO 



ENGINEERING ON THE FARM 



Plank. Plank roads (Fig. 184) have frequently been 

 used where a temporary road is needed and sawed timber 



n 



y4'x6 "sfr/naers-r 

 1 3 in. aparf ■ 



a 



3x/z"p/Mk 14 



w 



8 



1 1 



'-I 



Wk 



Fig. 184. Cross section of a plank road. Note the 6-inch offset of eve 

 fourth plank to assist in getting a wheel back on the road. 



is the cheapest road material available. Planks make an 

 excellent road, but their life is very short. 



Sand-clay. Sand-clay roads are used in localities where 

 neither rock nor good gravel is found. They are made of 

 clay and sand mixed in such proportions that the mix- 

 ture will become neither dusty in dry weather nor sticky 

 in wet weather, the clay being in sufficient quantity to 

 bind the sand thoroughly into one mass. 



Burned clay. Where fuel is available and natural road- 

 making materials are scarce, fairly satisfactory results have 

 been secured in road construction by the method of cover- 

 ing the roadbed with dry timber and throwing clay from 

 the side ditches over it. The timber is then fired, and the 



