258 



THE EARTH'S CRUST 



material it is carrying, forming a sand reef at some distance 

 from the shore. 



The waterways inclosed between sand reefs and main- 

 land are often of sufficient depth to form protected routes 

 for coastwise traffic. It is proposed artificially to extend 

 and to develop certain of these water areas along the eastern 

 coast of the United States so as to form a protected waterway 



INLAND SEA CAVE AND BEACH 

 This coast has been recently elevated. 



from New England to the southern ports. At present the 

 low, almost featureless shore of this region, with its shifting 

 sand bars and capes, makes coastwise navigation dangerous, 

 although it is protected by many lighthouses and life- 

 saving stations. The general set of the shore currents may 

 singularly modify the outlines of the reefs, as is shown in the 

 formation of the three much dreaded capes off the coast of 

 North Carolina. 



Sand hills, " dunes," form upon these reefs, building them 



