188 



THE WORK OF RUNNING WATER 



fications so successfully used by the French in repelling the 

 German march up the valley. 



Not only may a river be elevated, but it may be depressed. 

 In this case its rate of erosion is diminished, and the river 

 becomes marshy where the grade is low. Where the river 

 valleys approach the sea they will be submerged or drowned. 



These drowned river valleys form some of the finest 

 harbors on the coast. San Francisco Bay, Narragansett 



INTRENCHED MEANDER 



Bay and New York harbor are examples of protected harbors 

 due to the submergence of rivers. The mouth of the Hudson 

 was formerly some seventy miles to the east of Long Island, 

 that of the St. Lawrence to the east of Nova Scotia. In 

 fact the Atlantic coast north of the Hudson furnishes in- 

 numerable examples of submerged river valleys. 



Delaware and Chesapeake bays, where the early settlers 

 each had a nice little sea inlet instead of a rough wagon 



