SAND DUNES AND SALT MARSHES 



circular or oval outlines and gravelly forma- 

 tion, while the round pebbly island in the 

 Castle Neck River is of the same nature, but 

 is now so nearly submerged, that all humus 

 and land vegetation, as well as the finer par- 

 ticles of the top of the gravel hill, have been 

 washed away in stormy tides, and nothing but 

 boulders and sand is left. 



If the land had remained at the same level 

 as it was at the close of the glacial period, 

 we should be able to discover some traces of 

 ancient shore line where the sea waves form- 

 erly pounded, some old beaches with sub-fossil 

 shells and crabs on and under the borders of 

 the marshes, separated now from the sea by 

 acres of green salt turf and by barrier sand 

 dunes, which, like the marshes, are of recent 

 formation. If on the other hand the land had 

 risen at various rates, we should find a series 

 of flat terraces or several elevated beaches, as 

 on the Labrador coast to-day, where one sees 

 two or even three beaches one above the other, 

 some of them two hundred feet or more above 

 the present sea level and almost as clean as 

 when the surf beat on them. In this Ipswich 

 region, however, there are no traces of old 

 terraces or beaches, either at high tide level 



210 



