S o 



'^ J9. 



O lOO 200 300 400 500 600 700 800 



Miles 



Fig. 3. — Relation of size to distance traveled. Ideal history of cobble starting 

 at 178 grams' weight. 



S 



(U 

 & 



p^ 



^ 



50 100 150 



Number of cobbles in mixture 

 Average weight = 41 . 7 gms. 



Fig. 5. — Effect of amount of mixture in compartment of drum 



