70 AN OUTLINE OF THE 



Shaler, but if it amounted to as great a measure as he 

 concludes it must have been of brief duration, as its 

 records are indistinct. 



At the present time the land has but partially recovered 

 from the late glacial submergence. Many of the preglacial 

 valleys and valley lowlands are submerged as sounds and 

 bays, and the coast line is probably at least twenty or 

 thirty miles farther inland than it was in preglacial time. 

 It is for this reason that Mount Desert is isolated from 

 the mainland, and that the many other islands fringe the 

 coast. All of these were once hills on a coastal lowland, 

 and when thus exposed there would have been better 

 opportunity than now of discovering the true history of 

 the pre-granitic rocks. 



While in its present attitude, the s'ea has begun to make 

 its mark along the shore. As is the habit on steep coasts 

 of hard rock, the waves excavate caves wherever the rate 

 of cutting on the water line at the base of the slope is 

 faster than the wasting of the slope above ; but it is 

 seldom that this relation is found unless aided by joints or 

 other lines of structural weakness in the rocks near sea 

 level. Generally the wasting of the face of the slope on 

 young shore lines about keeps pace with the undercutting 

 of the waves at the base ; and thus a rocky bench is 

 formed a little below water level, surmounted by such 

 vertical faces as Great Head and Otter Cliffs. A consid- 

 erable part of our rocky shore is benched in this manner, 

 but less emphatically. At other parts of the shore, where 

 the land slope is more gentle, yet well exposed to in rolling 

 surf, the loose rocks gathered from the adjacent headlands, 

 and carried in by storm waves from the shelving bottom, 

 are thrown along the water's edge a little beyond high- 

 water mark, making a sea wall, such as occurs in a 

 re-entrant on the shore south of Southwest Harbor. In 

 more protected situations, the embankment formed by the 



