298 FIRST YEAR SCIENCE 



by lighthouses and life-saving stations. The greatest 

 Mediterranean port of France during the thirteenth cen- 

 tury, Aigues-Mortes, has been closed in by sand bars so 

 that there is no longer access to the sea and only the relics 

 of the former great city now exist. Thus have the mov- 

 ing sea sands overthrown the plans of men. 



A SAND SPIT. 

 Formed by the waves and currents. 



141. Final Effect of Wave and Current Action. Whether 

 the coast is shallow so that the storm waves spend their force 

 off shore, or deep so that they batter the shore with their 

 full strength, the tendency is to straighten the coast line. 

 In the former case sand reefs with gently flowing outlines 

 are built, and in the latter case the headlands are cut away 

 by the waves and the material moved along by the coast 

 currents to fill the protected bays and coves. As aerial 

 erosion is constantly tending to smooth off the irregulari- 



