SEA-BEACHES 



Various Divisions of Shore-Line. — Synimeiry of Sea-Beaches. — Action of Surf. — Rate of 

 Wear of Detritus. — Action of Coast Currents. — Sand Dunes. — rociiet-Beaches. — 

 Action of Sea-Weeds. — Straight Beaches. — Continental Shelf. — Action of Tides and 

 Waves. — Variations in Level of Shores. — Formation of Lagoons. — Mfinne Marshes : 

 Their Agricultural Value. — Endurance of Sand : Effect in Protecting the Continents. 



There arc two great divisions of the shore-line which 

 even the cursory observer quickly learns to recognize ; these 

 are the cliffs and the beaches. In the cliff section he easily 

 perceives that the sea is gaining" on the land. The condi- 

 tions under which the ocean extends its empire afford, as we 

 have already seen, a beautiful subject for inquiry. We have 

 now to turn to the parts of the coast where the sea spends 

 its energies, not on rocky steeps, but on the softer — yet really 

 more resisting— barriers of sand. Below the frowning walls, 

 formed where the suro;es are effectivelv assallinof the land, 

 w^e find generally a wide slope where the breakers are con- 

 tinually at work grintling the stone they have rent from the 

 cliff into small ])its. Usually, however, this incline is made 

 up of large, 1)Owlder-like masses, w^ith a few small pebbles 

 and a little sand packed into their interstices. We readily 

 see that the greater part of the Unv, stuff into which the v/aste 

 from the cliff is ground journeys with the currents, which the 

 storms and tides produce, to some point where it is built into 

 sand or pebble beaches. In this migration the pebbles move 

 along next the shore, in the shallow water where the waves 



