318 PROCEEDINGS OF THE AMERICAN ACADEMY. 



where our great interior areas have for some decades past absorbed the 

 attention of geologists ; more studied than river action in Great Britain, 

 but not from the point of view here taken. 



Under favorable conditions, irregular shore lines may be smoothly 

 graded early in their cycle of development. This is well illustrated 

 in the case of Martha's Vineyard. Here an extremely irregular con- 

 structional shore has been reduced to a remarkably even and well 

 graded outline in a relatively early stage of the attack of the sea on 

 the land ; for although a matter of two or three miles of the southern 

 headlands of the island have probably been cut away by the sea,* a 

 good part of the original shore line still remains in the branching bays 

 behind the bridging bars. The straight-cliffed headlands stand perfectly 

 in line with the bars across the bays. The later stages of outline on 

 graded shores are considered in the third section below. 



Application of the Foregoing to Cape Cod. 



The foregoing account of the development of shore lines is perhaps 

 an overlong preparation for the application of the simple principles 

 that govern shore changes to the case of Cape Cod ; but the excuse 

 for the details into which I have entered is the desire to show good 

 ground for the conclusion which they support ,* namely, that on a coast 

 as weak as the mainland of Cape Co^l, any originally irregular shore 

 line would soon be reduced to grade by the action of a sea so ener- 

 getic as the Atlantic, with its frequent southeast and northeast storms. 

 Only a moderate time and a moderate recession is therefore necessary 

 for the production of the even northeast cliff of High head. It does 

 not. however, follow from this that only a short time actually elapsed 

 in this work, for as far as has yet been stated, the High head cliif that 

 we see may have been cut far back from the first position of an even 

 cliff on this part of the coast line. Whether the time was long or short 

 can be best determined by examining into the conditions which deter- 

 mine the development of the bar by which the clilf is now protected, 

 this being the second problem announced above. 



It should be noted that when the northeast cliff of High head 

 formed the open shore line of this part of the Cape, the outline must 

 have extended in a sympathetic curve, HBFjA, for some distance 

 southeast of its present limit ; and from this early form there must 

 have been a gradual change to the shore line of to-day. At some time 

 during this change, the protecting bar, BJ, must have been built out 



* Shaler, loc. cit., 349. 



