A STUDY OF COBBLE ABRASION 



519 



notably in small pebbles than in large, which seems reasonable. 

 This interpretation is put forward as a hypothesis which I hope 

 later to test experimentally in considerable detail. 



Fig. 26. — Graph of values of R plotted against distance for the series illustrated 

 in Figures 8 to 25. 



Fig. 27. — Showing convergence of diameters of cubes rounded by cobbles 

 averaging 70 grams each. * 



8. Effect of kind of rock on rounding. — It is hoped later to make 

 studies of the rounding of shaly or schistose rocks whose ellipsoids of 



