ELISHA MITCHELL SCIENTIFIC SOCIETY. 73 



The railroads passing through this region long since dis- 

 covered the value of this gravel as a road material, and 

 have used it extensively as a ballast on their road-beds. 

 The small percentage of ferruginous clay soon cements the 

 gravel into a hard, compact mass. 



Limestone. — In the south-eastern portion of this region 

 limestone rock and calcareous shells from the oyster and 

 from fossil mollusks from the marl beds constitute the only 

 hard materials to be found there for road construction. In 

 some places the limestone is fairly hard and compact, as at 

 Rocky Point, on the Northeast Cape Fear River, at Castle 

 Hayne and elsewhere, and this rock will make an excellent 

 road. In other places it is made up of a mass of shells 

 firmly cemented together, as on the Trent River, near 

 Newbern, and elsewhere. At many other points beds of 

 shells are so slightly cemented together that the material 

 may hardly be called a rock, as the term is ordinarily used, 

 and in this condition it is of less value as a road material, 

 but may be used for this purpose to advantage. x\ careful 

 search will show limestone of one of these grades to occur 

 in considerable quantities at many points in these eastern 

 counties, betw^een the Tar River and the South Carolina 

 line. The harder, the more compact, and finer grained 

 this rock, the more valuable it is as a road material; but 

 the loose shells from marl beds, when free from clay, and 

 the oyster-shells from the coast, when placed on a road 

 surface and ground into fine fragments by travel, will 

 solidify into a hard, compact road, as may be seen in the 

 case of the excellent ''shell road" between Wilmington 

 and Wrightsville, which was built of oyster-shells. 



Clay and Sand. — The admixture of a small percentage 

 of clay or loam wnth the sand on the surface of the road- 

 bed wnll solidify it, and will thus very greatly improve the 

 character of the road; and in this connection, and only in 

 this connection, clay may be considered a useful road 



