THE SALT MARSHES. 



337 



swamp is between 70 and 80 feet perpendicular. It is higher nearer the sea, the 

 inner edge being rounded off, and I think at its highest point it can not be less 

 than 1 00 feet above high- water mark. 



If the hills advance at an equal ratio for twenty or thirty years more, they will 

 swallow up the whole swamp and render the coast a desert indeed, for not a blade 

 of grass finds nutriment upon the sand fsic|. 



This is even to-day a very good picture of the Cape [lenry sand hills 

 and the forest behind them. The advance of the sand must have 

 proceeded at a much less rapid rate during the past century, however, 

 than during the sixteen years before Lai robe's visit. 



Oilier evidences are not lacking of a subsidence and consequent re- 



Fio. 55,-Terraee along tlio aliore near Virginia Beach; sand above, clay below. 



cession of this coast Line. In the low terrace of Columbia clay (fig. 55) 

 which outcrops along Hie Loach from Capo I fen ry southward, some- 

 times several liiclci's above high-lido limit, sometimes between Hie 

 levels of high and low I ide, si limps in situ (usually of the cypress) are 

 frequenl ly to be seen. Such st umps are said to be abundant beneath 

 the waters of Albemarle Sound. 



THE SALT MARSHES. 



This topographical feature, which exactly coincides with a planl 

 formation, is almost everywhere developed along creeks and rivers 

 as far upstream as the influence of brackish water makes itself felt, 

 and in sheltered bayous and lagoons where the slope of the shore 

 is very gentle. Along streams Ihe salt marsh consists usually of a 



