GROUND, ROCK, WATER 



139 



and the erosion of rain, the coarser material maintaining itself at a 

 steeper angle, the finer material lying at a flatter slope. And again, 

 on the beach under the wash of the waves, the angle of repose of each 

 material will be characteristic, both fine and coarse lying less steep 

 than in the bank, but the angle of the finer material being still the less. 

 On the beach the finest stuff will be dragged farthest out by the waves, 



SHORES SUBJECT TO WAVE-ACTION 



SECTION ON A-B 



ec-J- 1 " 1 ' 1 " i _J 



effective wave ach 



A 



AAND 

 AND GRAVEL 



SECTION ON C-D 



DRAWING XVII 



so that the ground at the foot of the cut bank or cliff will often consist 

 of rocks and coarse gravel, while nearer the water line will be finer 

 gravel and sand. Under the surface of the water, the beach will extend 

 outward, composed of finer and finer materials, until it is sufficiently 

 below the surface not to be disturbed by ordinary wave action. Then 

 it slopes more steeply down to the original bottom of the body of water. 

 (See Drawing XVII, above.) 



