33 FARM DEVELOPMENT 



be wise to put the surfacing material on in two or three 

 general layers, thoroughly mixing and smoothing the 

 first before adding the next. 



The roller is a very important machine for compact- 

 ing the roadway and its .use can hardly be overestimated 



in road construction. It 

 should be used after the 

 mixing and smoothing is 

 completed, both on the 



Figure 219. Macadam road on one side , , , 



of the center of the grade and an earth UDDCr laver and On the 

 track on the other side. , J 



layers beneath. During the 



progress of the work, any large stones which happen to 

 be in the gravel or clay should be carefully removed or 

 broken up. 



MACADAM STONE ROADS 



In preparing the bed for a macadam road, a strip, 10 

 feet or more in width, at the center or at the side of the 

 center of the crown should first be prepared. This can 

 be done in soils free from stone by using the reversible 

 road machine, drawing some earth out of the proposed 

 roadway and leaving a slight embankment against which 

 to place the stone at either side, as shown in Figure 211. 



Crushed rock for macadam roads. The granite, trap 

 rock, limestone, sandstone or other hard stone used for 

 the lower portion of the macadam roadway should be 

 in pieces from 2 to 3 inches in diameter. Where softer 

 rock, as limestone, can be more cheaply secured it may 

 be used for the lower courses, using trap rock or other 

 better-wearing rock for the surface. In some cases 

 harder and softer rocks may be mixed, though this must 

 be done with the greatest care, to prevent uneven wear- 

 ing. If the stone is to be laid 12 inches deep, crushed 

 stone of this size can be used for the lower 8 or 9 inches. 

 The next layer of 2 to 3 inches should be of stone about 

 half the diameter mentioned. On top of this should be 



