GULLIVER. — SHORELINE TOPOGRAPHY. 237 



the same manner that a river higher up in its course causes streams to 

 flow away from the main channel down the slope of the alluvial plain. 

 The gathering is seen in the case of the Broad, and the filling up in the 

 Savannah (C. S., 155). 



These tidal runways, which open to the sea in a direction away from 

 the main river, are often no doubt former distributaries of the river, at 

 present ke[)t open by the tides. The river delta phenomena merge into 

 the tidal very intimately in this region, and features are due usually 

 to more than one cause. River, tidal, and current action are here 

 blended, with the indications that the tides are the dominant factor in 

 tlie determination of the shore forms. 



The average height of tides at cape Romaiu is five feet, while the 

 highest observed tides in this area rise from eight to nine feet. 



An example of a ratio similar to the South Carolina type occurs on 

 the north coast of Holland (Holl., 2, 3, 4, 5, 6, 9 ; Atlas Univ., 33). 



Southern New Jersey Type. — Northward from Winyah bay the ratio 

 is in favor of alongshore action. Areas showing some tidal in and out 

 flow, controlled by alongshore action, are seen on the following sheets 

 (C. S., 152, 149, 148, 123). 



When the lagoons are nearly filled, as in southern New Jersey, the 

 longitudinal feature of the shore is not so marked. But in this case, 

 the time element must be considered, a stage later than that in North 

 Carolina probably exists, and the ratio between tide and current is not 

 necessarily changed. 



North Carolina Type. — The next ratio taken to illustrate this pro- 

 gressive series is where the youthful shoreline shows continuous offshore 

 bars, broken only at intervals of several miles by tidal inlets. Examples 

 are seen on the following sheets (C. S., 122, 138, 145, 14G, 147, 150). 



The tides in the region of Ilatteras rise from one to three feet, while 

 the rate of the currents is various, being much affected by storms. 



Texas Type. — A final example in this series may be taken from the 

 gulf of Mexico, on tlie opposite side from which the first was taken. 

 On the east side of the gulf the ratio seemed to be in favor of pure 

 tidal action ; on the west, however, the alongshore action a[)pears to be 

 practically uninterrupted by the tides, and has determined the form of 

 the Texas bar, continuous for 102 miles (C. S., 210, 211, 212). 



"The tide is almost always less than a foot, and its time is very 

 variable and uncertain. Storm tides are the only important ones." 

 (C. S., 211.) 



