GEOLOGICAL AGE AND FORMATION. 43 



particles of soil from the most elevated parts, and deposit 

 them in banks and points on the adjacent lower grounds, 

 burying beneath them whatever remains of animals or 

 plants might be there. In the succeeding elevations, these 

 points and banks, composed of fine and rich washings, 

 have become the most productive soils of the county. The 

 shells and other fossils buried beneath them are preserved 

 unchanged, while those on or near the surface have decayed 

 without leaving any traces, except in cases like that at 

 Tuckahoe, when some cementing matter has preserved the 

 form of the shell in the more indestructible materials which 

 surrounded them. 



§ Fkom what has been said in relation to the advance 

 of the salt-marshes on the upland, and to the existence of 

 cedar-swamp earth under them in many places, the evi- 

 dence is conclusive that these marshes are of very recent 

 origin. Quite large portions of them have been formed 

 since the first settlement of the county. The marshes 

 along Delaware Bay, especially those about Maurice River 

 Cove, are well illustrated by the section, across the cedar 

 swamp and marsh from the upland in front of Mr. W. S. 

 Townsend's to near the mouth of Sluice Creek on Dennis 

 Creek.* In this section it will be seen that the marsh is 

 on nearly the same level with the cedar swamp; the 

 lowest ground being near the place where the marsh and 

 swamp meet, and the surface rising gradually both toward 

 the creek and the upland. The bottom on which the 

 swamp stands is full of logs and other remains of fallen 

 timber, quite down to the sand and gravel which underlies 



* See page 30. 



