

Holmes's Notes on the Geology of Charleston. 195 



of South Carolina has changed, and the waters of the coast be- 

 come too cold and uncongenial to these testacea, if, as some sup- 

 pose, they are of the same species. 



Other interesting geological phenomena are displayed in this 

 inland passage of Wadmalaw Sound, which demand some notice. 

 Beginning at Bears Bluff on the west, where it connects with 

 the Edisto river, and ending at Wappoo cut, on Stono river, to 

 the east, there is no portion of it that does not impress upon the 

 mind of the most careless observer, the conviction that it was 

 once an extensive fresh-water swamp. Stumps and logs of the 

 largest cypress and cedar trees (Cvpressus disticha and Juivperus 

 virginiana) are met with, throughout its extent. There are per- 

 sons now living, who remember when parts of this passage could 

 only be navigated by canoes, where now some half dozen steam- 

 boats could lie abreast, and where there is water sufficient to float 

 a frigate. Throughout its extent, but principally about midway 

 of this passage, its navigation is greatly obstructed by mud-flats, 

 which are exposed at half-tide, and can only be passed by vessels 

 of light draft, and at high water. The salt marshes extend from 

 the river to the high land on both sides, and vary from a few 

 yards to a mile in width ; and their surface is slightly covered by 

 every tide. 



But the most interesting feature is the hundreds of little " ce- 

 dar islands/ 7 as they are called, whose soil, composed of vegetable 

 matter, partly decomposed, is only one foot deep, and rests upon 

 the mud on which grows the- salt marsh. The spring tides flow 

 over them, but the ordinary tides, rising only above the marsh 

 land, surround and undermine the small cedars found growing 

 there in great numbers, whose lateral roots being confined to a 

 hght superficial loam, the stunted trees are .compelled to yield to 

 the destructive agent, so that the whole space is filled with their 

 living and dead, or dying trunks. The larger ones with tap-roots 

 descending deeper than the superficial loam, remain erect after 

 death; but there are hundreds that are prostrated often whilst 

 alive, and that lie just where they fell, with their trunks directed 

 outwards. These, as soon as their small limbs and sappy parts 

 have rotted, become imbedded in the salt mud : and the islands 

 °n which they stood being eventually deprived of their covering 

 of vegetable loam, a growth of salt marsh speedily springs up. 



Undoubtedly these islands were once occupied by the large 

 c ypress trees, whose trunks and stumps (many of the latter erect) 

 are now found in numbers in the soft mud around. When the 

 barriers to the ingress of the salt waters of the Edisto and Stono 

 rivers were originally destroyed, they did not immediately cover 

 the whole of the swamp in question ; but after providing a chan- 

 nel for themselves, they must at the return of every tide have 

 gradually increased in width, and thus carried off more or less of 



