191 1.] STEVENSON— FORMATION OF COAL BEDS. 591 



reaches the permanently wet area. Immediately below its sod, is 

 mud or soft earth, which varies greatly in composition. Near the 

 creeks, it is usually fine clayey mud with embedded roots, the whole 

 evidently transported material ; at a little distance, it is black earth 

 or muck, formed in a swamp ; while at a greater distance one finds 

 only a mass of fibroits roots and vegetable matter with no admixture 

 of earth or mud. The last two are of in j///« origin. The"meadow^s" 

 along the Passaic and Hackensack rivers, emptying into New York 

 harbor, show an extreme thickness of 32 feet of '' mud " resting on 8 

 feet of blue clay, while farther up the stream are great marshes 

 resting on fine sandy material. One sees on the surface of these 

 meadows great numbers of white cedar stumps and the mud is 

 crowded with remains of cedar timber. 



The condition is due to encroachment by the sea, whereby the 

 treeless marshes advance inland and overrun the white cedar swamps 

 along the streams ; one finds at many places the old cedar forest 

 buried in the tidal marsh, while the cedar swamp still exists at a 

 little way beyond. The salt water kills the freshwater grasses and 

 the trees on the border. In many places trees flourished 80 years 

 ago, where one finds now only salt marsh muck. The white cedar 

 is a very durable wood ; trunks of trees killed by the salt water are 

 still standing in localities where several feet of muck have accumu- 

 lated around them. 



Lyell"'" observed the efifects of this encroachment in Georgia. 

 In coming down to the coast, he found the trees becoming dwarfed 

 and at length disappearing to be replaced by reeds ; but in the marshes 

 he saw the stumps and stools of cypress, still retaining the erect 

 position in which they had grown. He cjuotes Bartram, wdio stated 

 that when planters, along the coast of the Carolinas, Georgia and 

 Florida, as well as westward to the Mississippi, bank in the grassy 

 tidal marshes for cultivation, they " cannot sink their drains above 

 three or four feet below the surface, before they come to strata of 

 cypress stumps and other trees, as close together as they now grow 

 in the swamps." 



^*"' C. Lyell, "Second Visit to the United States of North America," 

 London, 1850, Vol. L, pp. 334-336. 



189 



