190 



AGRICULTURE. 



out of the gravel ; in short, the gravel should be as clean as 

 possible; it should be screened, graded, and put on in layers, 

 and should be well rolled. 



STONE ROADS. As a rule, gravel is more or less rounded, 

 and therefore does not at first bind well. You know that a 

 road could not be well made out of marbles. To bind well 

 there must be sharp corners and rough sides on the pieces. 

 So we find that broken stone will make a stronger and more 

 durable road than will gravel. But we must remember the 

 points already referred to, namely, the road must first of all be 

 thoroughly drained, both underneath and on the sides; the 

 stone must be put down in courses, the largest below and the 

 smallest on the surface, and every course must be thoroughly 



Fig. 84. This is the kind of road that is made by placing loose stones 

 on a dirt road without prope 

 stones sink through the mud be 



. . 



on a dirt road without properly preparing the foundation the 

 neath. 



rolled as it is laid. It is a mistake to leave the rolling until 

 the road is all filled in. The dirt sub-soil should first be well 

 rolled. In using broken stone care should be used in choos- 

 ing a tough rock ; if the rock is soft it will soon be ground 

 into dust. Tough limestone and the hard rock called trap 

 are the best. Sandstone and most kinds of granite are too 

 easily crumbled for use on roads for heavy travel. 



Now, as to the mode of building or laying a stone road. 

 First of all, we may build the road of broken stones, none of 

 which are over three inches in diameter, laying the stone in 

 courses, and well packing it by rolling. In this way we make 



