Bui. 348, U. S. Dept. of Agriculture. 



Plate VIM. 



Fig. 1.— Granite. 



Fiq. 2.— Rhyolite. 



Fig. 3.— Gabbro. 



Fig. 4.— Diabase. 



Fig. 5— Sandstone. Fig. 6.— Schist. 



SCREENINGS FROM ROAD-MAKING ROCKS. 



