1S70.] 227 [Shaler. 



The last considerable change of level which this shore has expe- 

 rienced, came at the close of the Pliocene era. It seems likely that 

 thi? uplift carried the shore line much to the eastward of its present 

 position. The whole of the sea island belt is being worn away by 

 the ocean at a quite rapid rate. The scouring action of the powerful 

 tidal currents which flow through the fiords between the islands, tears 

 away a great deal of the materials over which they sweep. Along 

 the whole sea island belt from Winyah -Bay, just north of Cape Roman, 

 to the mouth of the St. John River, in Florida, this erosive action 

 has resulted in the production of a broad, slightly submerged table 

 land, having an average width of about eight miles, and an average 

 submergence of about three fathoms. This table of sand? is very 

 well shown on the sailing chart of the U. S. Coast Survey, she^r 3d. 

 The outer part of this bank probably marks the position of the shore 

 at the close of the last uplift ; that which created the sea island re- 

 gion. We shall soon see reasons for supposing that this must have 

 been an exceedingly recent occurrence in the geological sense of that 

 word. Wherever one of the great tide water streams, such as the 

 Edisto. the Coosa or the Broad River, debouches into the sea. the coast 

 chart shows that the sands swept out by it have built a delta which 

 reaches beyond the table sands, and some distance out into the deeper 

 water beyond. 



It is very probable that the coast line was once much further out to 

 sea than the border of this three fathom deep shoal would indicate. 

 If the reader will attentively notice the way in which the Gulf 

 Stream runs after it leaves the straits of Florida, he will perceive that 

 it is thrown with great violence ag ainst a part of the coast of the 

 Bay of the Carolinas. Its current, with a velocity of two to four 

 miles per hour, strikes against the bottom of the sea in 31°, where 

 the water has a depth of only one hundred fathoms. From this 

 point nearly to Cape Hatteras, or for most of the length of the Bay 

 of the Carolinas, this stream probably touches the bottom on its inside 

 border. 



There can be no doubt that this stream must exercise a certain 

 wearing action against this part of the slope of the continent. A 

 river having the velocity of the Gulf Stream at this point, or a tidal 

 current, such as may be observed in our harbors, is capable of taking 

 up and removing considerable quantities of detritus. Whatever ero- 

 sive force the Gulf Stream may have at present, there is a great 

 probability that in the immediate geological past its action on this 



