452 Farm Mechanics. 



closely to the cube with broad, flat faces, sharp angles and 

 having the same diameter in three directions. Fragments 

 of this form pack most readily and, as the broad, flat faces 

 set against each other, the fragments do not so readily turn 

 under the wheel or horses' feet and withstand a heavier 

 load without crushing. 



Where sands and gravels are used in road building those 

 of glacial origin which are much sharper and more angular 

 than water worn types are much to be preferred, for the 

 simple reason that when packed together they give a more 

 rigid body and stronger binding. Beach gravels and sands 

 cannot be held rigidly by any ordinary cementing material 

 because, with the round, smooth surfaces, there is little 

 opportunity for any locking. 



560. Cleanness of Material. Where crushed rock is used 

 in the building of roads it is important that these materials 

 be clean and free from dirt, clay and rubbish of any sort. 

 So with gravel or sand, when these are called for they 

 should be clean. In general, anything which woiks against 

 uniformity of material should be avoided. 



EARTH ROADS. 



In the country in most parts of the United States the 

 greatest number of miles of travel for a long time to come 

 must be made over earth roads. It is therefore of great 

 importance that they should be built in the best possible 

 manner. The proper construction of earth roads is made 

 the more important through the fact that when well built 

 and well maintained there is no road easier on the team, 

 the carriage or the parties riding, where speed is an im- 

 portant consideration, than an earth road. 



561. Forming the Road-bed. After the grade has been 

 established and under-drainage provided where necessary, 

 all organic material and stone should be cleared out of tin. 1 



