52 GLACIAL GEAVELS OF MAINE. 



accounts in part for the absence of such long and continuous beach terraces 

 as those of lakes Bonneville, Lahontan, and Agassiz. We have seen that 

 changes in the level of the sea were rapid, so that the surf beat for only a 

 relatively short time at any one level; but we must also remember that the 

 land surface of most of the coast region of Maine is very uneven, consisting 

 largely of hills and valleys. The hills are in general not high, but high 

 enough to form a multitude of islands off the shore as the sea changed its 

 level with respect to the land. As the sea rose and fell, not only did the 

 shore outline change greatlv, but the number and positions of the islands 

 changed also. Each island more or less protected a portion of the main- 

 land from the fury of the Atlantic waves. Although the waves must have 

 beat against all that part of Maine situated below 230 feet, long horizontal 

 beaches could not be formed, jjartly because of the converging of the beach 

 outline into the bays, and partly because of the great numbers of protecting 

 islands. The places were comparatively few Avhich were so exposed that 

 large beaches, measured either horizontally or at right angles to the shore, 

 were deposited. The small beaches whicli must have been formed at that 

 time in the landlocked bays and fiords are recognizable now either not at 

 all or only with difficulty. Probably the rarity of long, continuous beaches 

 is also due in part to shore ice. Even now, except on the most exposed 

 coasts, the shore ice affords considerable protection against the winter 

 storms. It is a fair inference that at the time the walrus came as far south 

 as Portland the shore ice was more abundant than at present and somewhat 

 resembled the Arctic ice foot. 



Resume. — For scvei'al reasons no long and continuous horizontal beaches 

 were formed on the coast of Maine by the sea in late glacial and postglacial 

 time while it stood above its pi-esent level: 



1. The changes of level were too rapid to permit the formation of cliffs 

 of erosion in the solid rock. 



2. During the comparatively brief time the surf beat upon any one 

 jDortion of the land the energy of the waves was chiefly expended in erod- 

 ing the till and drifting it away from the capes into the bays. 



3. The positions of the exposed bays and headlands constantly shifted 

 during the changes in level of the sea, partly on account of the changes in 

 the shore line and partly because of the appearance or disappearance of 

 protecting islands off the shore. 



