DAVIS. — OUTLINE OF CAPE COD. 313 



equality with the work to be done. When this happy condition is 

 reached, the river may be said to have graded its channel. Youth 

 then passes into adolescence. 



A comparable series of changes may be detected in studying the 

 profile of a seacoast at right angles to the general shore line. As the 

 sea can at first usually dispose of more waste than it gathers, the coast 

 is energetically attacked and forced to retreat, and sea cliffs are thus 

 produced. But in virtue of the changes thus brouglit about, the energy 

 of on-and-off-shore attack decreases, while the waste coming from the 

 growing cliffs increases ; thus ability to do work approaches equality 

 with work to be done, and the sea-floor profile, like that of the valley 

 floor, may be said to be graded. When a graded profile is attained, 

 the adolescent stage of shore development is reached. 



The amount of retreat necessary before a graded profile is attained 

 varies with the texture of the coast, and with its exposure to the sea. 

 A coast of unconsolidated deposits will soon supply a large amount of 

 waste from its clitfed margin, while the cliffs of a rockbound coast will 

 shed waste slowly ; hence, on coasts of given exposure, grade will be 

 assumed with a less amount of cliff"-cutting where the rocks are weak 

 than where they are strong. This recalls the behavior of rivers in 

 regions of weak and resistant rocks ; in the latter, they may assume 

 gentle slopes ; but in the former, rather steep slopes are necessary to 

 carry off the freely offered waste ; and gentler slopes can be assumed 

 only as the whole surface is worn down : this general relation having 

 been pointed out some years ago by Major Powell (Uinta Mountains, 

 194). Moreover, inasmuch as a greater amount of waste can be 

 handled on exposed coasts than on i^rotected coasts, a considerable 

 retreat may develop high cliffs on the former before enough waste is 

 shed from the cliff face to give the shore waves all the work they can 

 do ; while on protected coasts a moderate retreat, producing low cliffs, 

 will supply as much waste as can be handled by the sea. 



The under-water form of a graded profile, when first developed, also 

 depends largely on the violence of the ou-and-off-shore movements of 

 the sea. On a protected coast, the bottom will be degraded so as to 

 descend from the shore line by a gentle slope to an eroded platform of 

 moderate depth ; but on an exposed coast, the bottom will be degraded 

 so as to descend from the shore line by steeper slope to a platform of 

 greater depth. 



