42 GLACIAL GRAVELS OF MAINE. 



Its longer side is thus presented to the open ocean in the direction from 

 which the largest storm waves come. Considering the small size of the 

 island, its position so far from the land, and the exposure of its flank to the 

 storm Avaves, it is doubtful if any place can be found on the whole coast 

 where the sea could act to better advantage. Here we may know what the 

 utmost fmy of the sea could accomplish, remembering that when the ocean 

 stood at higher level than now the island would be still farther from the 

 mainland and still more exposed to waves from every direction. 



Except near the harbor and at a few small coves, the island is bordered 

 by cliffs of erosion at the present level of the sea. On the more exposed 

 (east and southeast) sides these cliffs vary in height from a barely percep- 

 tible roughening of the rock to 30 feet, and in a few places they are even 

 higher. They show the irregular and honeycomb appearance character- 



FlG. 4 Lougituilinal section of cove gravel. 



istic of the cliff of wave erosion. In a few places, not far above high tide, 

 quartz veins show conchoidal depressions and uneven groovings, due to 

 sand carving under the action of the surf At the head of one of the coves 

 are several potholes 10 to 15 feet above high tide. The waves become nar- 

 rowed, and consequently higher, as they advance up the cove. They rush 

 swiftly up the slope at the end of the cove to a height of 20 or even 30 feet 

 above high tide, and then the undertow flows swiftly back. During this 

 alternate rush of water in opposite directions the stones and bowlders are 

 set whirling in any depressions there may be in the rock, and thus potholes 

 are in time eroded. A section across one of these coves or small bays 

 shows a mass of beach gravel and bowlders occupying the bottom of the 

 valley that slopes down to the cove. In cross section the top of the beach 

 matter is neaily level. A longitudinal section shows that it slopes rather 



