290 MASSACHUSETTS AGRICULTURE. 



Grading of Roads. 



The finished road consists of two distinct parts : the sub-road 

 or road proper, and the covering. The sub-road is first graded 

 up to within about a foot of the intended finished surface, and 

 its surface shaped and prepared to receive the covering. 



It is also important that the embankments should be made in 

 a solid and substantial manner, care being taken not to put into 

 them vegetable matter, or decaying substances of any kind to 

 endanger their stability, or to cause unequal settling. 



In cases where the sub-grade runs near the surface of the 

 ground, the sods must be taken off, and all roots and stumps 

 removed. 



Mucky earths must be replaced by material fit for a solid 

 foundation. 



Ledges should be excavated to a depth of one foot, at least, 

 below grade, and the surface dressed so as to leave no hollows 

 for holding water. 



The sub-road should have the same cross-sections as the surface 

 of the finished way, so as to shed any water that may percolate 

 through the superficial coating, and in order that the covering 

 may have the same thickness throughout. 



Foundations for Road Covering. 



That part of the structure lying immediately under the road 

 covering may be termed the foundation, and upon it, in a meas- 

 ure depends the durability of the covering, and the ease of 

 travel. 



As shown by Sir John Macneill's experiments, before men- 

 tioned, the force required to move a ton, on a broken stone sur- 

 face, on a bottom of rough pavement, is forty-six pounds ; while 

 upon a broken stone surface, laid on an old flint-road, it is sixty- 

 five pounds. 



The covering may be laid directly upon the ground without 

 further preparation, than above indicated, or a foundation may 

 be made of concrete, or of rough-paving. 



Many of the military roads of the Romans were constructed 

 upon a concrete foundation, some of which have endured to this 

 day without being entirely worn away. 



The use of this foundation, was introduced into England not 

 many years ago by Thomas Hughes. 



