OCEANS AND LAKES 247 



to fine mud. The final reduction of beach material is accom- 

 plished with extreme slowness, however, for the particles are 

 becoming smaller and therefore lighter, and each is surrounded 

 by a film of water, which acts as a cushion. All blows, there- 

 fore, come to be weak blows. Furthermore, before it is re- 

 duced completely, the material is apt to be removed from the 

 mill of the beach, and deposited in quieter water. It is re- 

 placed by new material worn from the cliffs by the waves, 

 or brought from the land by streams. 



FIG. 265. - Hooked spit at entrance to Smithtown Harbor, Long Island. 



(Buffet.) 



Features formed by deposition of shore drift. When 

 shore currents reach the entrance of a harbor, or some other 

 abrupt bend in the shore line, they commonly continue in the 

 direction in which they had been moving, instead of turning 

 with the coast. They accordingly pass from the shallow 

 water of the outer beach into deeper water, where they drop 

 their load. The result is an embankment, known as a spit. 

 Waves may build spits above sea level, and the winds may 

 then form dunes upon them. Many spits accordingly pre- 

 sent irregular surfaces, and support, hills which rise 10 to 40 

 or more feet above sea level. Spits are tied at one end to the 

 beach, of which, indeed, they form an extension, and are 

 bounded by deep water at the free end. The ends of spits are 

 frequently bent by storm waves. Bent spits are called 

 hooks (Fig. 265). Occasionally the hook at the end is closed 



