46 GLACIAL GEAVELS OP MAINE. 



examined, the bowlders of local rock found lying upon the beach gravel 

 and the soil are due to recent weathering and sliding of the rock, and not 

 to wave erosion. 



Fig. 6 is drawn across the valley. Lengthwise of the valley the sur- 

 face of the beach gravel has about the same slope as the solid rock of the 

 island. In some cases one of these plains of cove gravel can be followed 

 all the way up a valley to the top of the island and then downward to the 

 sea on the other side. The structure lengthwise of the valleys is shown in 

 the diagram, fig. 7. 



If the summit is narrow and rooflike, the gravel is scanty or absent at 

 that point; but where the top is a rounded plateau the beach gravel is 

 continuous across the whole island. The mode of formation of these con- 

 tinuous sheets of gi-avel, filling the valleys and extending across the whole 

 island, is evident. As the sea rose or fell, a valley would always be 



Fig. 7. — Ancient beaches sloping np from shore. 



occupied by a bay or cove, and a hill would form a cape. The till would 

 be washed away from the hills (then capes) and would be drifted obliquely 

 into the present valleys (then bays). If the changes in level went on at a 

 uniform and rather rapid rate, a continuous sheet of beach gravel would be 

 foiTued across the bottom of the valley from the top of the slope down to 

 the present sea level. If there were pauses in the process of change of 

 level, then terraces or cliff's of erosion would interrupt the even slopes of 

 the beach. I saw no trace of any such jiause, unless at about 25 feet 

 above the present beach, where there is an obscure terrace. The valleys 

 which have been covered in this way by beach gravels are not, on the 

 island of Monhegan, more than one-foui1:h or one-third of a mile in extreme 

 breadth. It is evident that the most violent waves must come from the 

 side toward the open ocean, and the fact that this sort of gravel is more 

 rounded on the south and southeastern slopes of the island is a proof that 

 the stones owe their final shapes to beach action. 



