520 



CHESTER K. WENTWORTH 



equilibrium would depart notably from spheres, but nothing has 

 yet been done along this line. 



9. Effect of violence of motion on rounding. — Not yet studied. 



10. Effect of kind of motion on rounding. — Not yet studied. 



11. Effect of size of cobble on rounding. — Not yet studied. 



12. Effect of size of associated cobbles on rounding. — Figures 27 

 and 28 show the influence of this factor and indicate that large 

 cobbles are much more effective rounding agents than those con- 

 siderably smaller than the cobble rounded, as shown by the much 



Fig. 28. — Showing convergence of diameters of cubes rounded by cobbles 

 averaging 20 grams each. 



slower convergence of the lines in the latter case. It will be noted 

 that the corners and edges lose more rapidly at first (curves concave 

 upward) while the sides lose more rapidly later when their areas 

 are decreased by the wear of corners and edges (curve convex 

 upward). Further studies of this factor are planned. 



13. Effect of kind of rock on surface texture.- — Not yet studied. 



14. Effect of violence of motion on surface texture. — Not yet 

 studied. 



15. Effect of kind of motion on surface texture.- — ^Not yet studied. 



16. Effect of size of cobble on surface texture. — Not yet studied. 



17. Effect of size of associated cobbles on surface texture. — Not 

 yet studied. 



