GLACIAL DRIFT. 



311 



standing upon the first. Another example may be seen at the south 

 end of Long island. It is possible that Steamboat island and its cul- 

 mination south in a ridge in shallow water is to be regarded as one of 

 these ramparts. 



Sea Walls. 



A variety of the sea-beach action is indicated by the term sea zvalls, 

 which I suggested for them in 1861.* It is a long embankment of smooth 

 boulders, without sand or gravel, lying just behind the beaches. When 

 the more powerful storms prevail off the coast, stones up to two feet 

 in diameter are carried a distance of hundreds of feet, and deposited just 

 back of the beaches. Sometimes they are fifteen feet in height. I have 

 noticed them in Rye. 



Disturbances in Modified Drift. 



A few examples of curvature in layers of gravel and sand have been 

 noticed. One of them is represented in Fig. G'^. It is seen on the east 



Fig. 63. — Section in Gravel, Whitefield. 



side of John's river, in Whitefield, just east of the depot. Coarse gravel 

 occupies the centre and lowest part of the arch, and there is another 

 mass of it upon the steep slope to the left. The bank was exposed for 

 about fifteen feet. 



* Preliminary Report Geology of Maine, p. 370. 



