236 PROCEEDINGS OF THE AMERICAN ACADEMY. 



ami the tides, and the volume of tidal waters, the tidal in and out flow 

 largely determines the forms developed. 



The stage of development of this shoreline is one which shows char- 

 acteristic features of adolescence. The projecting headland of Sylt 

 island is graded and has characteristic wings on right and left. The sea 

 is now carrying this shoreline landward. The islands of Fnno, Rom, 

 and Amrum were at an earlier period graded, as is indicated by their 

 form, and are now locally aggrading, as is indicated by the outlying sand 

 banks built in front of probable former shorelines. This geographic 

 interpretation is found to accord with the geology as given by Dr. 

 L. Meyn.* 



The relation of such marked tidal scour to the adolescent stage of 

 development of this coast is not clear. The sequence of tidal forms 

 during successive stages of cycles is a subject needing much furtlier 

 study. 



Georgia-South Carolina Type. — In the case of portions of the Georgia- 

 South Carolina coast (C S., Iu2, 153, 154, 155, 156) the ratio is less in 

 favor of the tides, although they are still the controlling factor in the 

 development of coastal forms. The shore curves are not continuous for 

 long distances, nor are the offsets arranged systematically. Many tidal 

 channels interrupt the sea beaches. These tidal runways are prevail- 

 ingly at right angles to the general direction of the shoreline, but there 

 are many connecting channels which run alongshore roughly parallel to 

 the beaches. 



With the exception of Bulls bay (C. S., 153), where there are bro;id 

 flats covered at high and bare at low tide, the runways drain great areas 

 of salt marsh. The detritus brought down by streams from tlie land, the 

 sands blown by the wind, and the growth of swamp vegetation, as well 

 as the action of salt water upon mud-laden waters, all tend to convert 

 flats into solid land.f The tidal scour is opposed to this filling, and 

 carries off what it can by its runways into deeper water, to be finally 

 built into the continental delta. 



The control of tidal runways b}' large rivers is shown in this region by 

 the Savannah, Broad, and Winyah. Tidal channels are turned toward 

 the stream current in some places, while in others the river fills up the 

 runways with detritus causing the water to flow away from the river, in 



* Geologische-Uebersichtskarte der Provinz Schleswig-Holstein, 1 : 300,000, 

 Berlin, 1881. 



t See discussion by Prof. Shaler, Gtli Ann. Rep. U. S. G. S., 1884-85, 360, 

 361 ; and 10th Ann. Rep. U. S. G. S., 1888-89, 2G1-2G1. 



