LAKES AND SHORES 



157 



Bars, reefs, etc., often hinder the movements of ocean vessels, 

 especially when they tend to close the entrance of harbors. A spit 

 which does not obstruct the entrance to a harbor, on the other hand, 



Fig 160. Sketch-map of a part of the New Jersey coast. The dotted belt 

 at the east is the barrier, modified by the wind. The area marked by 

 diagonal lines is the mainland; the intervening tract is marsh-land. The 

 numbers show the depth of the water in feet. Scale: 34 inch = 1 mile. 



is sometimes an advantage, since it breaks the force of the incoming 

 waves in storms, and so helps to form a harbor. Spits w r hich form 

 harbors have determined the location of numerous villages and 

 cities. Erie, Pennsylvania, is an example. 



2. Rivers. River erosion has little effect upon the shore-line, 

 but the deposition of sediment brought down by streams is of much 

 consequence in changing the outline of the land, especially where 



