546 STUDIES FOR STUDENTS 



EXPLANATION OF PLATE II 



Figs, i, 2, and 3. — These samples illustrate the different forms 

 developed in crushing granite cubes. The one on the left is a typical 

 cone. The one on the right has a tendency toward the wedge-shaped 

 form, while the one in the middle is a typical wedge form. The upper 

 part of this wedge is a sharp ridge from one end to the other. 



Figs. 4, 5, and 6. — These three figures have their apices pointing 

 toward the observer. They are all well shaped cones, in which there 

 has been especially well developed the concentric structure referred to 

 in the text. 



