EOAD MODELS. 19 



from noise. They have as yet not been used to any great extent on 

 the country roads of the United States. The small sett, or "klein- 

 pflaster/' pavement of Germany is as yet almost unknown in this 

 country. A hard, tough rock, preferably basalt or diabase, is broken 

 by machinery into cubes 3 to 4 inches in size. These are placed on 

 a light sand cushion, with a concrete or old macadam base as founda- 

 tion. In Germany they are generally laid in an oyster shell or mosaic 

 pattern, while in Hungary and Austria they are laid in rows at 

 45 degrees to the axis of the road. This pavement may be laid at a 

 fairly low first cost, is not expensive to maintain, is neither noisy nor 

 slippery, and is well adapted to mixed traffic. 



ASPHALT-BLOCK ROADS. 



Plate XI, figure 1, represents an asphalt-block road. 



Section A shows the subgrade, and beginning with section B is 

 shown the concrete curb. Section B shows the concrete base 6 inches 

 thick, mixed in the proportion 1:3:7; section C, the cement mor- 

 tar bed, one-half inch thick, composed of 1 part of slow-setting 

 Portland cement and 4 parts of sand; section D, the asphalt block 

 surface. The asphalt blocks are 5 inches wide, 12 inches long, and 

 2 inches thick. In section E the surface has been covered with sand 

 which has been screened through a |-inch mesh screen. This sand 

 carpet is used to fill the joints between the blocks, and should be 

 allowed to remain for 30 days. The surface should then be swept 

 clean. 



BRICK ROADS. 



Plate XI, figure 2, illustrates the construction of a 28-foot road- 

 way, 14 feet of which is a brick road with 6-inch concrete curbings. 

 There is a 3-foot earth shoulder along one edge of the brick roadway, 

 and the remaining 11 feet form an earth road on the opposite side. 

 The earth road has a slope toward its ditch of 1 inch to the foot. 

 The outer 11 feet of the brick roadway has a slope of three-eighths 

 inch to the foot, but the slope of the inner 3 feet is less, forming the 

 crown of the road. The earth road is preferred in dry weather by 

 many drivers of horses. 



Section A illustrates the prepared subgrade for the brick roadway; 

 section B, the concrete curbing placed along the edges of the pave- 

 ment; section C, a stone base 6 inches deep, and section D, a con- 

 crete base 6 inches deep. Either of these bases may be used, although 

 the concrete is generally preferable. This base course of the road 

 may vary in thickness from 4 to 8 inches, according to soil condi- 

 tions, but 6 inches is in most general use. Section E shows the sand 

 cushion, about 2 inches deep; section F, the brick laid and rolled but 

 not grouted; section G, the expansion joint between the brick and 



